EP3041909A1

EP3041909A1 - Wood product or natural fiber composite material product and use of a formaldehyde-free aminoplast resin for the production thereof

Info

Publication number: EP3041909A1
Application number: EP14738379.8A
Authority: EP
Inventors: Brigitte Dix; Frank Borner
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2013-09-04
Filing date: 2014-06-24
Publication date: 2016-07-13
Also published as: WO2015032458A1; DE102013014641B4; DE102013014641A1

Abstract

The invention relates to a wood product or natural fiber composite material product made from at least one natural fiber-containing, 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 formaldehyde-free aminoplast resin based on a reactive protective group and a dialdehyde as a crosslinker, and to the use of such an adhesive for producing a wood product or a natural fiber composite material product.

Description

Wood product or natural fiber composite product and use of a formaldehyde-free aminoplast resin for their preparation

The invention relates to a wood-based product or natural fiber composite product of at least one lignocellulosic and / or cellulose-containing or natural fiber material, which was provided with an adhesive and cured or crosslinked in the desired form, and the use of a formaldehyde-free aminoplast resin for producing such wood panel.

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]), support systems, I-beams and honeycomb panels with a core of paper, aluminum, etc. and a cover layer, eg of plywood or fiberboard.

As starting material for lignocellulose composites and possibly natural fiber

CONFIRMATION COPY Composite materials are particles of wood, annual and perennial plants, secondary residues such as waste wood, waste paper, production residues and lignocellulose-containing residues from agriculture, eg straw or hemp shives. The particles are usually assembled by means of an adhesive to form a composite material. In addition to the lignocellulosic raw material and the adhesive or the polymer, the composites usually contain additives such as hydrophobing, flame retardants, curing accelerators, adhesion promoters, formaldehyde scavengers, dyes and surface-active substances to obtain certain properties of the material.

The most widely used adhesive for wood materials is urea-formaldehyde resin (UF resin). Inside, more than 90% of the wood materials are bound with UF resin. In addition to many positive properties such as reactivity, handling and price, UF resins also have 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, a modification of the UF resins, e.g. with melamine (mUF or MUF resins) or the use of resin combinations (e.g., UF resin and polymeric diphenylmethane-4,4'-diisocyanate [PMDI]).

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 lignins, tannins, polysaccharides such as starch, fatty acids, proteins have so far not been able to assert themselves for reasons of both technology and availability; to a limited extent, they are used as extenders for synthetic resins (eg 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 vol.% Of wood chips and about 40 vol.% Of cement and additives. The composite of the wood chips takes place by the setting of the mineral substance components. The same applies to particleboard and fiberboard containing gypsum or magnesite as an inorganic component. 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., Medved, 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 floors (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, 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 quality paper impregnated with a transparent melamine resin. Furthermore, there is a so-called Gegenzugpapier back. For the impregnation of the decorative paper urea-formaldehyde resin (UF resin) and then melamine-formaldehyde resin is often used in a two-stage process for cost reasons. 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). How to In particular, 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://leqacY.forestproud.org/adhesives09powerpoints.htm). In addition to the legal provisions, voluntary, stricter limit values have been established, such as the Ecolabel RAL-ZU 76 for low-emission uncoated and coated wood-based panels (Blue Angel) to 0.05 ppm, and the value required by the German Federation of prefabricated buildings (BDF) 0.03 ppm. Furthermore, regulations in Japan and the US led to considerations in Europe regarding a reduction of the limit below the E1 standard.

To reduce the formaldehyde emission of wood-based materials - preferably to the level of wood or wood particles - is the recommendation made in 2004 by the International Commission for Research on Cancer (IARC) to recommend formaldehyde "presumably carcinogenic to humans" (class 2A). categorized as "carcinogenic to humans" (Class 1) (IARC, 2004: International Agency for Reserach 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 2011: News Releases: Added Substances Added to HHS Report on Carcinos, 10 June 2011, http://www.niehs.nih.gov/news/newsroom/releases/2011/june10/) rated 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 Europe, there are currently efforts to formaldehyde in Category 1 B (Substances which are thought to be carcinogenic in humans) (Hope P. 2012, Formaldehyde in the European Regulatory Area, 8th European Wood-based Panel Symposium, 12.10.2012, Hannover, Coutrot D. 2012, Formaldehyde Situation in Europe: a French view: 8th European Wood-based Panel Symposium 12.10.2012, Hannover, Fischer J. 2013: Very different sector development: Holz-Zentralblatt 21: 499).

A reduction of the formaldehyde content in adhesives for wood-based materials or in impregnating and impregnating resins for decorative papers therefore does not seem to be sufficient from the current perspective; instead, the most complete substitution of formaldehyde is required.

There are numerous possibilities for reducing the formaldehyde release of wood-based panels, such as e.g. Use of formaldehyde-poor UF resins (molar ratio U: F = 1: 1 or <1), modified UF resins, use of glues with little or no free formaldehyde (eg PF resin with protein), use of formaldehyde scavengers, application of a diffusion barrier , Surface treatment (eg coating, cladding of the wood-based material product), subsequent treatment of the wood-based products with formaldehyde-binding systems as well as storage and tempering of the wood-based products.

Numerous research papers include methods for reducing formaldehyde release, such as B. medium-density fiberboard (MDF) for digestion of the wood under alkaline conditions, the treatment of wood chips with formaldehyde-binding substances prior to the thermo-mechanical pulping and removal of the resulting from thermo-mechanical wood pulping degradation products from carbohydrates. Furthermore, the formaldehyde release of wood-based products can be reduced by the use of utility plates or bark, the variation of the type of wood, the moisture of the wood particles, the plate construction, the pressing conditions, etc.

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, organofunctional 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 cost is high and there is the safety 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. The curing can only take place at relatively low temperatures, so that PVAC can be used only in the cover layer or in thin plates. Epoxies require resin and hardener, which must be present in an exact mixing ratio, moreover, the polyaddition is highly exothermic, so there is a risk of fire. The service life is very short, epoxies are irritating, environmentally hazardous, so that a special protective equipment is required during handling. 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 mainly 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 invention was based on the object to develop wood-based products with formaldehyde-free amino resins, in which the manufacturing conditions and the mechanical and hygrischen material properties as possible correspond to the formaldehyde-containing aminoplast resin-bonded materials.

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, glyoxal, furfuraldehyde, etc. (Adam, 1988: Melaminharze, in: Kunststoff-Handbuch 10: Duroplastics, Ed .: 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.

US-A-4,906,727 discloses a urea-aldehyde condensate for surface coatings obtained by reacting urea or certain alkylene urethanes with certain aldehydes (including formaldehyde). US-A-4,220,751 discloses a resin for surface coatings of urea or urea derivatives and certain monoaldehydes (e.g., alkyl, aryl-aldehyde).

DE 691 03 847 12 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 (eg epoxy resin emulsion, synthetic latex) and on the other hand, a reaction product of eg 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 material 55: 9-12 replace formaldehyde with suc- cinaldehyde, a dialdehyde with a short hydrocarbon chain. Further, 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 (Maminski, ML, Borysiuk, P., Parzuchowski, PG 2008; Improved water resistance of particleboard 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) are added to a 45% tannin solution, and the reaction 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, the use of α-keto-aldehydes, for example in DE 103 22 107 B4, and of dialdehydes, for example in DE 10 2006 029 408 A1, as formaldehyde substitutes, have been described and discussed in great detail. However, the practical application failed because of the rate of 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 dimethoxyethanal (DME) were used for laboratory particleboard (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: Di- methoxyethanal-derived resins for wood based panels. In: Processing of the International Panel Products Symposium 2009, 16-18 September 2009, La Cite Internationale de Congres Nanes, France, ISBN: 978-1-184220- 18-3). 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 93 ° C chipboard were manufactured Transverse tensile strength meet the requirements of the standard for indoor panels. In further investigations melamine-DME precursors were mixed in a mixture of 5% to 16.5% PMDI, 26.5% latex. 16.5% PMDI and 5% glyoxylic acid (based on melamine-DME + latex) used as adhesive 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 T2. 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. J. Wood Prod. 68: 13-20).

The only besides formaldehyde for the preparation of melamine resins practically used monoaldehyde is the glyoxylic acid. Me laminating resins prepared from glyoxylic acid and its salts are found, inter alia. a. as a flow aid in concrete processing or as an additive for hydraulic binders, such. in DE 196 27 531 B4 and in the tannery, e.g. in DE 39 35 879 A1 and DE 10 2005 032 585 A1 discloses application. Such resins, however, have not hitherto been suitable for use in wood-based materials, since they can lead to swellings in the end products due to the high salt contents in the presence of water. In DE 41 40 899 A1, a condensation product of a mixture of e.g. Melamine or urea, glyoxylic acid and glyoxal described, which is also used as a 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.

Furthermore, water-soluble formaldehyde-free polycondensation products based on aminotriazines, glyoxylic acid and an amino compound as additives for aqueous Rige suspensions based on inorganic binders known 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 result for natural-fiber composite products.

The object of the present invention is to provide a wood-based product or natural fiber composite product that is easy to manufacture and emits less polluting substances.

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 resins based on a reactive protective group and a dialdehyde as a network former. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the descriptions and the tables.

The wood-based product or natural fiber composite product of at least one natural fiber-containing or lignocellulosic and / or cellulosic material provided with an adhesive and cured or crosslinked in the desired form provides that the adhesive is a formaldehyde-free aminoplast resin based on a reactive protecting group a dialdehyde is formed as a network former. For example, plywood, chipboard and fiberboard, scrimber, wood-polymer materials (WPC), engineered wood products such as Oriented Strand Boards (OSB), Laminated Veneer Lumber (LVL), veneer strip wood can be used as wood-based materials (Strand Strand Lumber [PSL]), girder systems, I-beams and honeycomb panels with a core of paper, aluminum, etc., and a top layer, eg of plywood or fiberboard. other than plate-shaped products, for example, molding products or the like. 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 for 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.

The adhesive as a formaldehyde-free aminoplast resin based on a reactive protective group and a dialdehyde as a network former envisages that the amine, for example melamine, dicyandiamide, benzoguanamine or acetylenediurea, is first partially dissolved by addition of glyoxylic acid. The monoaldehyde reacts with the amine and forms a protective group for further additions. The solution thus almost exclusively contains monoamines. It is dosed dialdehyde, so that there is only a small concentration of unreacted dialdehyde in the mixture. Conditions are set in which the equilibrium reaction of the addition and removal of the aldehyde to the amine is faster than the subsequent condensation. Therefore, the dialdehydes are incorporated into the dissolved part of the resin in exchange for monoaldehydes. After installation, even monoaldehydes form. The released in the equilibrium reaction monoaldehyde can be attached to amines again. On the undissolved constituents, only a monoaldehyde can attach. No insoluble passivation layers can form on the solid surface of the amines.

As a result, melamine, benzoguanamine, dicyandiamide and acetylene diurea are capable of similar dissolution rates as in the preparation of the corresponding formaldehyde resins. The monoaldehydes increase the solubility of the amines and act as entrainers in the continuous phase. By doing so, not only can oligomers with very short sequences be formed, but free aldehydes bound in the resin system also increase the reactivity of the resin. The resin system thus continues to contain free aldehydes. which increases the reactivity of the systems to such an extent that the reactivity of formaldehyde-based resins can be achieved or even exceeded. It is thus possible to use formaldehyde-free amino resins as thermosets whose reactivity corresponds to that of formaldehyde-poor UF resins. There are no special occupational safety measures or release agents necessary for use, the adhesive is miscible with water and can be used on conventional systems without conversion measures.

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

The formaldehyde-free aminoplast 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 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-base product or natural-fiber composite product may also contain, in addition to lignocellulose-containing or cellulose-containing fractions, materials which are not made from renewable raw materials, for example polystyrenes, polyurethane foams, plastics, synthetic fibers, aramids or intumescent elements.

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 can also be designed as a single-layer or multi-layer, wherein layers of non-cellulose-containing or non-lignocellulose-containing materials can also be provided in the case of multilayer wood-based products or natural-fiber composite products, resulting in a composite material of the wood-based material product or natural fiber Composite material 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 aminoplast resin is used as the sole adhesive. As a result, the Formaldehydeinsatz is excluded.

As an alternative to a sole use of the formaldehyde-free aminoplast 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 formed 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.

It is also possible that the aminoplast 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 aminoplast resin thus having at least one inorganic binder.

The formaldehyde-free aminoplast resin based on a reactive protective group and a dialdehyde as a network former can be used in solid, liquid, foamed or intumescent form.

The wood-based product or natural-fiber composite product may have functional le additives such as water repellents, flame retardants, curing accelerators, adhesion promoters, formaldehyde scavengers, dyes and / or surface-active substances may be added.

The invention also relates to the use of a formaldehyde-free aminoplast resin based on a reactive protecting group and a dialdehyde as a network former for producing a wood-based product or natural fiber composite product. As described above prepared by a process

(i) reacting an amine with a monoaldehyde having at least 2 carbon atoms to form an intermediate having at least one amine group a reactive protecting group derived from the monoaldehyde, and

(ii) reacting the intermediate with a dialdehyde or trialdehyde to form a crosslinkable amino resin.

In the context of the present invention, it has been found that storage-stable amino resins can also be prepared with dialdehydes or trialdehydes if the starting amine (such as, for example, melamine or urea) is first reacted with a suitable monoaldehyde. In a known manner, the aldehyde group reacts with the nitrogen of the amine group. The residue covalently bonded to the nitrogen atom of the amine group as a consequence of this reaction and derived from the monoaldehyde then acts as a protecting group which prevents in step (ii) from undesired significant crosslinking in the reaction with the dialdehyde or trialdehyde.

As in the addition of an aldehyde to an amine according to the reaction equation

-NHR + OHC-> -NR-CH (OH) - the aldehyde group is converted into a hydroxyl group and this hydroxyl group is a reactive group that can be used for a later crosslinking reaction, it is the protective group is a reactive protecting group. After step (i), one or more amine groups of the starting amine are thus initially blocked by a reactive protective group derived from the monoaldehyde. If the dialdehyde or trialdehyde is added in step (ii), it may initially react only with N atoms which have not yet been blocked with a protective group in step (i). In addition, since the reaction of the monoaldehyde with the starting amine in step (i) is an equilibrium reaction, the dialdehyde or trialdehyde in step (ii) can partially replace the protecting groups derived from the monoaldehyde.

The process forms oligomers with very short sequences. These amino resins can also be readily stabilized at high solids contents (for example 60% by weight).

In a preferred embodiment, the crosslinkable amino 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 step (ii) reaction of the dialdehyde or trialdehyde with the nitrogen of the amine arise on the one hand according to the reaction equation

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

However, free aldehyde groups, a significant premature (and therefore unwanted) crosslinking does not occur.

The reactivity of the crosslinkable amino resin is also enhanced by the presence of the reactive protecting group. As already explained above, the radical which derives from the monoaldehyde and functions as a protective group for the amine group contains a reactive OH group which, when appropriate conditions are set, is available for a subsequent crosslinking reaction.

Amines which can be used for the preparation of amino resins are known in principle to the person skilled in the art. For example, the starting amine may have 2-3 amine groups (ie, diamine or triamine).

As the starting amine, 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 polyacrylamide, or a mixture of these compounds may be used.

Suitable aminotriazines are, in particular, amino-1,3,5-triazines, e.g. Melamine, acetoguanamine and benzoguanamine. Suitable urea derivatives include, for example, alkylated ureas such as methylurea or cyclic ureas such as acetylenediurea or ethyleneurea. Suitable thiourea derivatives include, for example, cyclic thioureas such as ethylene thiourea. Examples of suitable imino urea derivatives which may be mentioned are cyclic iminoureas. As suitable cyanamide, for example dicyandiamide or cyanamide can be mentioned. Diamino-C 1-8 alkanes, for example, may be mentioned as suitable diaminoalkanes. Diamido-C 1-8 -alkanes, for example, may be mentioned as suitable diamidoalkanes.

Monoaldehydes which have at least 2 carbon atoms and can be reacted with an amine are known in principle to the person skilled in the art.

The monoaldehyde may have at least one more functional group in addition to the aldehyde group.

For example, the additional functional group may be a polar group.

When the monoaldehyde has one or more additional functional groups, it may, for example, be a carboxylic acid ester group, a carboxylic acid group or a salt thereof (ie a carboxylate group), an ether group or a carbon-carbon double bond. The monoaldehyde of the present invention may also be an aldehyde which provides good addition products with water and is therefore present as a hydrate.

Preferably, the monoaldehyde is selected from a salt of aldehyde carboxylic acid, an alcoxy aldehyde (e.g., a dialkoxy aldehyde, a monoalkoxy aldehyde), furfural, an unsaturated aldehyde, or a mixture thereof.

As the salt of the aldehyde carboxylic acid, for example, a salt of glyoxylic acid (for example, glyoxylic acid sodium or glyoxylic acid potassium) or a salt of malonic acid monoaldehyde may be used.

If a salt of the aldehyde carboxylic acid is used, it may be, for example, an alkali metal, alkaline earth metal or ammonium salt.

The alkoxyaldehyde may be, for example, a monoalkoxyaldehyde or a dialkoxyaldehyde. The alkoxy radical may be, for example, a C 1-4 -alkoxy radical. As suitable dialkoxyaldehyde, e.g. Dimethoxyethanal be called.

Suitable unsaturated aldehydes are, for example, crotonaldehyde, acrolein, or mixtures thereof.

Preferably, no formaldehyde is added in the process.

Preferably, no alkylation of amine groups of the amine takes place in the process.

The molar ratio of the monoaldehyde to the amine groups of the amine can be varied over a wide range.

For example, if the amine has 3 amine groups, the molar ratio of the monoaldehyde to the amine groups of the amine is preferably in the range of 0.5 / 3 to 3/3, more preferably 1.5 / 2.5 to 3 or 1.8 / 3 to 2.2 / 3. For example, if the amine has 2 amine groups, the molar ratio of the monoaldehyde to the amine groups of the amine is preferably in the range of 0.2 / 2 to 2/2, more preferably 0.3 / 2 to 1.5 / 2 more preferably 0.5 / 2 to

In the process, it is in principle possible that in step (i) each amine group of the starting amine reacts with at least one monoaldehyde so that at least one reactive protective group is present on each amine group. The addition of the dialdehyde or trialdehyde in step (ii) then takes place exclusively via the partial replacement of reactive protecting groups.

Alternatively, however, it may be preferred that in step (i) at least one amine group of the amine is not reacted with the monoaldehyde to form a reactive protecting group. This amine group, which is not blocked by a reactive protective group, would then be directly accessible in step (ii) for a reaction with the dialdehyde or trialdehyde. Suitable process conditions to ensure this are known to those skilled in the art. For example, the monoaldehyde can be added in molar excess, based on the number of amine groups of the amine.

Suitable solvents for step (i) are generally known to the person skilled in the art. Preferably, an aqueous solvent is used. Furthermore, hydrogen bonds breaking polar solvents can be used.

Suitable reaction conditions (such as reaction temperature and pH) for the reaction of the amine with the monoaldehyde are known in the art.

The reaction temperature may be, for example, in the range of 20 ° C to 100 ° C, more preferably in the range of 40 ° C to 65 ° C.

Depending on the amine and the monoaldehyde 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.

If the amine is not or only slightly soluble in water, it may be preferable to use a hydrated monoaldehyde. The not or only slightly water-soluble amines are, for example, aminotriazines (such as melamine or benzoguanamine), cyclic urea compounds (such as acetylene diurea), cyclic thiourea compounds (such as ethylene thiourea), cyanamides (such as dicyandiamide).

The water-soluble monoaldehyde is, for example, a monoaldehyde which, in addition to the aldehyde group, still has a functional polar group.

Examples of suitable water-soluble monoaldehydes are e.g. a salt of an aldehyde carboxylic acid (for example, a salt of glyoxylic acid or malonic monoaldehyde), an alkoxyaldehyde (for example, a dialkoxyaldehyde such as dimethylethanal or a monoalkoxy aldehyde).

The water-soluble aldehydes act as "draggers" of the amine into the aqueous phase, ie the reaction of the water which is insoluble or only sparingly soluble in water with the water-soluble monoaldehyde forms an intermediate amine which has a significantly higher water solubility than the starting amine , a reactive protective group is generated by the addition of the monoaldehyde to one or more amine groups, which on the one hand prevents the subsequent reaction with a dialdehyde or trialdehyde leads to an undesired premature crosslinking of the material, but on the other hand, a reactive group (in the form of a hydroxyl group) contains, which can support the crosslinking reaction when setting suitable crosslinking conditions (especially acidic pH range or salts at elevated temperatures).

Since the reaction of the monoaldehyde with the amine is an equilibrium reaction, during the subsequent addition of the dialdehyde or trialdehyde in step (ii), the reactive protective groups derived from the monoaldehyde can be partially replaced by the dialdehyde or trialdehyde. The monoaldehyde thus partially released in step (ii) is then available again for reaction with the starting amine. Only a monoaldehyde can attach to the undissolved constituents of the starting amine. No insoluble passivation layers can form on the solid surface of the amines. As a result, water-insoluble amines (such as melamine, benzoguanamine, dicyandiamide and acetylenediurea) can be made to achieve dissolution rates similar to those of the corresponding formaldehyde resins. The monoaldehydes increase the solubility of the amines and act as entrainers in the continuous phase.

When the starting amine is a water-soluble compound (for example, urea or guanidine), it may also be preferable to use the above-described monoaldehydes having good water solubility (for example, an aldehyde carboxylic acid or a salt thereof or an alkoxy aldehyde such as dimethoxyethanal). However, since the amine already has good water solubility, it is also possible to use monoaldehydes having a lower water solubility (for example unsaturated aldehydes such as acrolein or crotonaldehyde).

As stated above, in step (ii) of the process according to the invention, the reaction of the intermediate product provided with one or more reactive protective groups with a dialdehyde or trialdehyde to form a crosslinkable amino resin takes place.

Preferably, the crosslinkable amino resin has free aldehyde groups.

Dialdehydes or trialdehydes convertible with amines are known per se to a person skilled in the art.

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

In the context of the present invention, it is possible for the dialdehyde or trialdehyde to be added to the intermediate from step (i), which is preferably present in an aqueous solution. Alternatively, it is also possible that the intermediate from step (i) (for example in the form of an aqueous solution) is 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.

Preferably, the intermediate from step (i) is not isolated but used in the form of the aqueous solution in which it was prepared in step (i) for the reaction with the dialdehyde or trialdehyde in step (ii).

The amount of dialdehyde or trialdehyde added in step (ii) can be varied over a wide range.

If the starting amine has 3 amine groups, the molar ratio of the dialdehyde or trialdehyde present in step (ii) to the amine groups of the triamine added in step (i) is in the range of 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 has 2 amine or amide groups, the molar ratio of the dialdehyde or trialdehyde added in step (ii) to the amine groups of the diamine added in step (i) is in the range from 0.1 / 3.9 to 3, 9 / 0.1, more preferably 0.3 / 1, 7 to 1, 7 / 0.3, even more preferably 0.5 / 1, 5 to 1, 5 / 0.5.

If the starting amine has two amine groups, the molar ratio of the dialdehyde or trialdehyde added in step (ii) to the monoaldehyde added in step (i) may be, for example, in the range from 1 / 0.01 to 1/3 or 1 / 0.2 If the starting amine has three amine groups, then the molar ratio of the dialdehyde or trialdehyde added in step (ii) to the monoaldehyde added in step (i) may, for example, be from 1 to 0.5 in the range of 1 / 0.01 to 1/5 or 1, 5 / 0.2 to 1, 5/2 or even 2 / 0.3 to 2/1.

Suitable reaction conditions (such as reaction temperature and pH) for the reaction of an amine with the dialdehyde are known in the art in principle. The reaction temperature in the step (ii) 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.

As already explained above, oligomers having very short sequences can be formed by the process according to the invention and the amino resins can also be readily stabilized even at high solids contents (for example 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 protecting group derived from the monoaldehyde that stabilization is very well possible even at high solids contents.

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

The reactivity of the crosslinkable amino resin is also enhanced by the presence of the reactive protecting group. This achieves a reactivity which is equal to or even exceeds that of formaldehyde-based resins.

After step (ii), the prepared amino 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.

Embodiments of wood-based products will be described below.

Example 1 Particleboard with formaldehyde-free Aminoplastharz based on

Glyoxylic glyoxal

From wood shavings of spruce single-layer chipboard were produced under the following conditions:

Chips: Chip fraction 0.6 mm <x <5 mm

Plate thickness: 13 mm

Adhesive: melamine-glyoxylic acid-glyoxal resin A and B

Adhesive content: 12% (solid resin based on dried chips)

Hardening accelerator: 0.6% ammonium sulfate

Paraffin: 1, 5% (solid based on dry-dried chips)

Target density: 700 kg / m ³

Press time: 22 s / mm plate thickness

Pressing temperature: 200 ° C

The resins were prepared as follows:

Resin A

330 g (2.25 mol) of 50% aqueous glyoxylic acid is neutralized with 50% aqueous sodium hydroxide solution to pH 7.5 (precipitation of sodium glyoxylate). After addition of 126 g (1 mol) of melamine is heated with vigorous stirring to 60 ° C and stirred for 1.5 h at this temperature (suspension). Then 54.38 g (0.375 mol) of 40% aqueous glyoxal solution within 40 min. slowly added dropwise at 60 ° C. After a further 5 min, the solution is cooled rapidly to room temperature. The resin is stable at room temperature for more than 3 months. The solids content is 42% (TGA).

Resin B

330 g (2.25 mol) of 50% aqueous glyoxylic acid are neutralized with about 234 g of 50% aqueous sodium hydroxide solution to pH 7.5 (precipitation of sodium glyoxylate). After addition of 252 g (2 mol) of melamine is heated with vigorous stirring to 65 ° C and stirred for 1.5 h at this temperature (suspension). Then 109g (0.75mol) 40% aqueous glyoxal solution was slowly added dropwise at 55 ° C within 30 minutes. After a further 5 minutes, the solution is cooled rapidly to room temperature. The resin is stabilized with ethanol. The solution can be used at 20 ° C for one week.

The flexural strength and the flexural modulus of elasticity according to DIN EN 310: 1993 as well as the transverse tensile strength (tensile strength perpendicular to the plate plane) according to DIN EN 319: 1993 were determined on the plates. The formaldehyde release of the chipboard was determined by the bottle method according to EN 717-3 after 3 h and 24 h storage. The results of mechanical plate properties and formaldehyde release are shown in Table 1.

Table 1: Mechanical properties and formaldehyde release of particleboard with melamine-glyoxylic acid-glyoxal resins

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

Resin A and the specified manufacturing conditions have met the mechanical properties requirements of Type P2 particle board. The formaldehyde release of the plates was very low. Example 2: Particleboard with formaldehyde-free aminoplast resin based on glyoxylic acid-glyoxal

Chips: Chip fraction 0.6 mm <x <5 mm

Plate thickness: 13 mm

Adhesive: melamine-glyoxylic acid-glyoxal resin C, D and E.

Adhesive content: 12% (solid resin based on dried chips)

Curing accelerator 0.6% ammonium sulfate

Paraffin: 1, 5% (solid based on dry-dried chips)

Target density: 700 kg / m ³

Press time: 22 s / mm plate thickness

Pressing temperature: 200 ° C

The resins were prepared as follows:

Resin C

444 g (3 mol) of 50% aqueous glyoxylic acid are adjusted to pH 8 with about 400 g of 50% aqueous potassium hydroxide solution at 0 ° C. In contrast to neutralization with sodium salt, there is no precipitate. At the transition point a slight yellow discoloration is observed. After addition of 252 g (2 mol) of melamine is heated with vigorous stirring to 65 ° C and stirred for 1.5 h at this temperature (suspension). Then 144 g (1 mol) of a 40% aqueous glyoxal solution are slowly added dropwise at 55 ° C within 25 minutes. After a further 5 minutes, the solution is cooled rapidly to room temperature.

Resin D

445 g (3 mol) of 50% aqueous glyoxylic acid is neutralized with 50% aqueous sodium hydroxide solution to pH 8.5 at 0 ° C (precipitation of sodium glyoxylate). After addition of 252 g (2 mol) of melamine is heated with vigorous stirring to 53 ° C and stirred for 2 h at this temperature. After 48h in the refrigerator, the approach is gel-like. When heated to 40 ° C, the resin is flowable again. Then 72.5g (0.5mol) 40% aqueous glyoxal solution was slowly added dropwise at 60 ° C within 40 minutes. After a further 5 minutes, the solution is cooled rapidly to room temperature. The resin is stable at room temperature for more than one month. The solids content is 51.9% (TGA).

Resin E

330 g (2.25 mol) of 50% aqueous glyoxylic acid are neutralized with about 234 g of 50% aqueous sodium hydroxide solution to pH 7.5 (precipitation of sodium glyoxylate). After addition of 252 g (2 mol) of melamine is heated with vigorous stirring to 65 ° C and stirred for 1.5 h at this temperature (suspension). Then 109 g (0.75 mol) of 40% aqueous glyoxal solution are slowly added dropwise at 55 ° C within 30 minutes. After a further 5 minutes, the solution is cooled rapidly to room temperature.

Reference chipboards were produced with a formaldehyde-poor urea-formaldehyde resin of the brand Kaurit® 337 from BASF AG (molar ratio urea: formaldehyde = 1: 0.94) under the same conditions.

The flexural strength and the flexural modulus of elasticity according to DIN EN 310: 1993 as well as the transverse tensile strength (tensile strength perpendicular to the plate plane) according to DIN EN 319: 1993 were determined on the plates. The formaldehyde release of the chipboard was determined by the bottle method according to EN 717-3 after 3 h and 24 h storage. Further, the formaldehyde release of the plates was determined by the 1 m ³ chamber method according to EN 717-1. The results of mechanical plate properties and formaldehyde release are shown in Table 2.

Table 2: Mechanical properties and formaldehyde release of chipboard with melamine-glyoxylic acid-glyoxal resins and a UF resin

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

With the resins C, D and E and the specified manufacturing conditions, the mechanical properties of particleboard type P2 have been met. The mechanical properties of the plates made with aminoplast resin are similar to those made with a UF resin. The formaldehyde release of the melamine-glyoxylic acid-glyoxal resin-made sheets is very low compared to the UF resin-bonded particleboard, well below the current limit of 0.1 ppm (EN 717-1) for the E1 emission class.

On the plates made with melamine-glyoxylic acid-glyoxal resin, the volatile organic compound (VOC) release after 24 hours storage in the 1 m ³ test chamber was also determined under the following conditions: temperature: 23 ° C, relative humidity: 50% ; Degree of loading of the chamber: 1 m ² / m ³ ; Air change rate 1 rr ¹ . The narrow surfaces of the plates were not sealed. The plates were up to the test sealed in foil. Volatile organic compounds were measured by Tenax sampling followed by thermal desorption and GC / MSD analysis in accordance with DIN ISO 16000-6. The aldehydes were determined by the DNPH method according to DIN ISO 16000-3. All individual substances in the retention region C6-Ci6 are designated as VOCs, and WOCs (Very Volatile Organic Compounds) are the volatile substances in the retention range <Ci 6.

The concentration (Mg / m ³ ) of volatile and volatile constituents of the chipboard with melamine-glyoxylic acid-glyoxal resins is listed in Table 3.

Table 3: Concentration (Mg / m ³ ) of volatile and volatile substances of

Chipboard with melamine-glyoxylic acid-glyoxal resins

In the VOC measurements, no emission of glyoxylic acid or glyoxal could be detected. Overall, VOC emissions are low. The major contributor to VOC is acetic acid emitted from the wood. Example 3: Particleboard with formaldehyde-free aminoplast resin based on glyoxylic acid glyoxal: Variation of pressing time

Chips: Chip fraction 0.6 mm <x <5 mm

Plate thickness: 13 mm

Adhesive: melamine-glyoxylic acid-glyoxal resin C

Adhesive content: 12% (solid resin based on dried chips)

Hardening accelerator: 0.6% ammonium sulfate

Paraffin: 1, 5% (solid based on dry-dried chips)

Target density: 700 kg / m ³

Press time: 22 s / mm and 15 s / mm plate thickness

Pressing temperature: 200 ° C

The resin was prepared as follows: Resin C

The flexural strength and the flexural modulus of elasticity according to DIN EN 310: 1993 as well as the transverse tensile strength (tensile strength perpendicular to the plate plane) according to DIN EN 319: 1993 were determined on the plates. The formaldehyde release of the chipboard was determined by the bottle method according to EN 717-3 after 3 h and 24 h storage. The results of mechanical plate properties and formaldehyde release are listed in Table 4.

Table 4: Mechanical properties and formaldehyde release of particle board with a melamine-glyoxylic acid-glyoxal resin, prepared at different pressing times

The pressing time could be reduced to 15 s / mm for the chipboard with a melamine-glyoxylic acid-glyoxal resin without deteriorating the mechanical plate properties.

Example 4 Chipboard with Formaldehyde-Free Aminoplast Resin Based on Glyoxylic Acid Glyoxal

Chips: Chip fraction 0.6 mm <x <5 mm

Plate thickness: 13 mm

Adhesive: melamine-glyoxylic acid-glyoxal resin F and G

UF resin Kaurit® 337 from BASF AG

Adhesive content: 12% (solid resin based on dried chips)

Hardening accelerator: 0.6% ammonium sulfate

Paraffin: 1, 5% (solid based on dry-dried chips)

Target density: 650 kg / m ³ and 700 kg / m ³

Press time: 22 s / mm plate thickness

Pressing temperature: 200 ° C

The resins were prepared as follows:

Resin F

Resin G

888 g (6 mol) of 50% aqueous glyoxylic acid are neutralized with about 50% aqueous potassium hydroxide solution to pH 7.3. After addition of 378 g (3 mol) of melamine is heated with vigorous stirring to 65 ° C and stirred for 1 h at this temperature. Then, 435 g (3 mol) of 40% aqueous glyoxal solution are slowly added dropwise at 55 ° C within 40 minutes. After another 5 minutes, the solution is dissolved in a water bath on a Mertemperatur cooled. The solution can be used at room temperature for at least one month.

The bending strength and the flexural modulus of elasticity according to DIN EN 310: 1993 as well as the transverse tensile strength (tensile strength perpendicular to the plate plane) according to DIN EN 319: 1993 were determined on the plates. The formaldehyde release of the chipboard was determined by the bottle method according to EN 7 7-3 determined after 3 h and 24 h storage. Further, the formaldehyde release of the plates was determined by the 1 m ³ chamber method according to EN 717-1. The results of mechanical plate properties and formaldehyde release are shown in Table 5.

Table 5: Mechanical properties and formaldehyde release of chipboard with melamine-glyoxylic acid-glyoxal resins or a UF resin

The mechanical properties of particle board are influenced by the density of the boards. When the melamine-glyoxylic acid-glyoxal resin was used, the standard strength requirements were still met at a plate density of 650 kg / m ³ . Example 5: Medium density fiberboard (MDF) with formaldehyde-free aminoplast resin based on glyoxylic acid glyoxal

Wood chips were made from debarked pine logs. From the wood chips, a pulp was produced by the thermo-mechanical process, which is dried in a tubular dryer and then glued in Blender process with melamine glyoxylic acid-glyoxal resin or the UF resin Kaurit® 337 BASF AG, sprinkled into mats and was hot pressed to MDF.

The conditions for the production of the MDF were:

Wood: pine wood

Wood digestion: 150 ° C, 5 minutes

Gluing process: Blender process

Adhesive: melamine-glyoxylic acid-glyoxal resin F

UF resin Kaurit® 337 from BASF AG

Adhesive content: 12% (solid resin / atro pulp)

Paraffin: Paraffin dispersion

Paraffin quantity: 1.5% (solids based on atro pulp)

Plate format: 500 mm x 500 mm

Plate thickness: 13 mm unpolished

Target density: 720 kg / m ³

Pressing temperature: 200 ° C

Press time: 22 s / mm plate thickness

The resin was prepared as follows:

Resin F

444 g (3 mol) of 50% aqueous glyoxylic acid are adjusted to pH 8 with about 400 g of 50% aqueous potassium hydroxide solution at 0 ° C. In contrast to neutralization with sodium salt, there is no precipitate. At the transition point a slight yellow discoloration is observed. After addition of 252 g (2 mol) of melamine is heated with vigorous stirring to 65 ° C and stirred for 1.5 h at this temperature (suspension). Then 144 g (1 mol) of a 40% aqueous glyoxal solution are slowly added dropwise at 55 ° C within 25 minutes. After another 5 minutes, the solution becomes fast cooled to room temperature.

On the MDF, the flexural strength and the flexural modulus of elasticity according to DIN EN 310: 1993 as well as the transverse tensile strength (tensile strength perpendicular to the plate plane) according to DIN EN 319: 1993 and the thickness swelling after 2h and 24 h water storage according to DIN EN 317: 1993 were determined. The formaldehyde release of the MDF was determined by the bottle method according to EN 717-3 after 3 h and 24 h storage. The results of mechanical and hygric plate properties and formaldehyde release are shown in Table 6.

Table 6: Mechanical and hygric properties and formaldehyde release of MDF with melamine-glyoxylic acid-glyoxal resin or a UF resin

The MDF produced with melamine-glyoxylic acid resin F did not meet the standard requirements with regard to the mechanical properties at the selected production conditions.

Example 6 Veneered plywood with formaldehyde-free aminoplast resin based on glyoxylic acid glyoxal 3-ply veneer plywood was produced under the following conditions:

Veneers: beech industrial tournaments

Veneer thickness: 1, 5 mm

Veneer size: 510 mm x 510 mm

Number of layers: 3

glue liquor:

Glue Resin: 100 g of melamine-glyoxylic acid-glyoxal resin C

Hardener: 10 g of 15% ammonium sulfate solution

Filling agent: 4 g rye flour type 1150

Glue application with roller: 200 g / m ² , one-sided application

Waiting time (closed): 10 minutes

Pressing pressure: 1, 5 N / mm ² - 2 N / mm ²

Pressing temperature: 140 ° C

Pressing time: 1 min / mm veneer thickness (4.5 minutes in total)

The resin was prepared as follows:

Resin C

The tensile shear strength (DIN EN 314-1: 2004) and the formaldehyde release according to the gas analysis method (prEN 717-2: 2011 (D)) were determined on the plywoods without air conditioning (immediate test) (Table 7).

Tensile shear strength and formaldehyde release of veneer plywood with melamine-glyoxylic acid-glyoxal resin

The formaldehyde emission of the produced veneer plywood is very low.

Claims

claims

1 . Wood material product or natural fiber composite product of at least one natural fibers contained, lignocellulose and / or cellulose-containing material provided with an adhesive and cured or crosslinked in the desired shape, characterized in that the adhesive as a formaldehyde-free aminoplast resin based on a reactive protective group and a dialdehyde is formed as a network former.

2. wood material product or natural fiber composite product according to claim 1, characterized in that it is formed one or more layers or formed as a multilayer composite material and the aminoplast resin is used in at least one layer.

3. wood material product or natural fiber composite product according to claim 1 or 2, characterized in that the aminoplast resin is used as a decor or surface coating or for fixing a decorative layer or wear protection layer.

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

5. wood material product or natural fiber composite product according to one of the preceding claims, characterized in that the aminoplast resin is used as the sole adhesive.

6. wood material product or natural fiber composite product according to one of claims 1 to 4, characterized in that the aminoplast 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 aminoplast resin is used in combination with an inorganic binder.

8. wood product or natural fiber composite product according to any one of the preceding claims, characterized in that the wood-based product or natural fiber composite product having functional additives.

9. Use of a formaldehyde-free aminoplast resin for producing a wood-based product or natural fiber composite product according to any one of the preceding claims, prepared by a process comprising

(i) reacting an amine with a monoaldehyde containing at least 2

C atoms, with formation of an intermediate product which has on at least one amine group a reactive protecting group derived from the monoaldehyde, and

(ii) reacting the intermediate with a dialdehyde or trialdehyde to form a crosslinkable amino resin

Use according to claim 9, wherein the crosslinkable amino resin has free aldehyde groups.

Use according to claim 9 or 10, wherein the amine is selected from a diamine, a triamine or mixtures or combinations thereof.

12. Use according to any one of claims 9 to 11, wherein the amine is an aminotriazine, urea, a urea derivative, thiourea, a thiourea derivative, iminourea, an imino urea derivative, a cyanamide, a diaminoalkane, a polyacrylamide, or a mixture of these compounds is.

13. Use according to any one of claims 9 to 12, wherein the monoaldehyde in addition to the aldehyde group has at least one further functional group.

14. Use according to any one of claims 9 to 13, wherein the monoaldehyde is an aldehyde carboxylic acid or a salt of the aldehyde carboxylic acid, an alkoxy aldehyde, an unsaturated aldehyde, or a mixture thereof.

Use according to any one of claims 9 to 14, wherein the amine is a diamine and the molar ratio of the monoaldehyde to the amine groups of the diamine is in the range of 0.2 / 2 to 2/2; or the amine is a triamine and the molar ratio of the monoaldehyde to the amine groups of the triamine is in the range of 0.5 / 3 to 3/3

16. Use according to any one of claims 9 to 15, wherein in step (i) at least one amine group of the amine is not reacted with the monoaldehyde to form a reactive protecting group and thus for the reaction with the dia-Idehyd in step (ii) available stands.

17. Use according to any one of claims 9 to 16, wherein a water-soluble monoaldehyde is used when the amine is water-insoluble or of low water solubility, wherein the water-soluble monoaldehyde is preferably an aldehyde carboxylic acid or a salt of the aldehyde carboxylic acid, an alkoxy aldehyde or a mixture thereof.

18. Use according to any one of claims 9 to 17, wherein the dialdehyde is glyoxal or a dialdehyde of the formula OHC- (CH 2) 1-3 -CHO.

19. Use according to any one of claims 9 to 18, wherein the amine is a triamine and the molar ratio of the dialdehyde or trialdehyde added in step (ii) to the amine groups of the triamine added in step (i) is in the range of 0.1 / 3 to 5.0 / 3 or the amine is a diamine and the molar ratio of the dialdehyde or trialdehyde added in step (ii) to the amine groups of the diamine added in step (i) is in the range of 0.1 / 3, 9 to 3.9 / 0.1.