EP2424727A1

EP2424727A1 - Composite material comprising two or more superimposed layers of wood

Info

Publication number: EP2424727A1
Application number: EP10718127A
Authority: EP
Inventors: Manfred Genz; Hans Ulrich Schmidt; Stefan Ullmann; Timo Prozeske; Stefan Meyer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-04-30
Filing date: 2010-04-26
Publication date: 2012-03-07
Also published as: KR20120028896A; BRPI1014389A2; WO2010125013A1; CN102458828A; JP2012525281A; CA2760407A1; RU2011148454A; US20120088098A1; US8563137B2

Abstract

The invention relates to a composite material having two or more superimposed wood layers. Said layers are joined together by means of a one component polyurethane adhesive containing a prepolymer having free NCO groups and a wood having a volume fraction of libriform fibres in the region of between 50 - 70 % is used.

Description

Composite comprising two or more layers of wood disposed one above the other

description

The invention relates to a composite material comprising two or more superimposed layers of a wood-like material.

Composite materials have very diverse fields of application.

For reasons of sustainable use of resources, composites made from renewable raw materials are particularly attractive. At present, annually approximately 800,000 ^m3 of tropical hardwoods (especially apitong etc.) used solely for container flooring, which corresponds to an area of approximately 560 km ² (= about 3 times the area of Washington DC) tropical rainforest, it cleared every year become. Corresponding restrictions and quotas already severely limit the availability of these tropical rainforest woods, so that one intensively searches for alternative materials.

From US 2007/0088103 a composite material is known, in particular two

Having layers bonded to a non-foamed polyurethane binder based on a urethane-modified isocyanate. The layers of the composite material may be lignoszellulosische layers, in particular cork, wood, grass or straw.

However, the document does not disclose composites of low density, high mechanical resilience and elasticity renewable resources.

It is known to produce laminated materials from wood, wherein the individual layers are bonded together with phenol-formaldehyde adhesives. However, it is disadvantageous that wood-based layer materials produced with phenol-formaldehyde adhesives sometimes have a relatively high density, from 0.8 to 1.0 kg / l, or even> 1 kg / l. Particularly disadvantageous, however, is the insufficient static and in particular their insufficient dynamic performance. This leads to early failure under static load (Institute of International Container Lessors (NLC), Technical Bulletin (TB) 001, September 1, 2002, Short Span Test), and especially to delaminations of the individual, with phenol formaldehyde and / or or polyvinyl acetate-bonded layers of coating materials produced therefrom. Such phenolic-formaldehyde-bonded coating materials also show their insufficient performance, especially at elevated temperatures, for example at 80 ^° C. It was accordingly an object of the invention to provide a composite material based on a wood-like material which has excellent mechanical and dynamic properties, in particular a high static and dynamic load-bearing capacity and high elasticity, at the same time low density, of clearly less than 1 kg / l, and maintains its high level of performance even at elevated temperatures.

This object is achieved by a composite material comprising two or more layers of a wood arranged one above the other, wherein the layers are interconnected with a one-component polyurethane adhesive containing a prepolymer having free NCO groups, which is characterized in that Wood with a volume fraction of libriform fibers in the range of 50 to 70% is used.

It has been found that a composite material based on a closed-chambered wood having excellent mechanical and dynamic properties and at the same time low density can be obtained by using layers made of the wood with closed chambers, with a one-component polyurethane adhesive containing Prepolymer with free NCO groups, are connected.

Libriform fibers are elongated, more or less thick-walled, narrow-lumen, pointed and closed tube cells carrying air or water.

According to Treiber (in H. -G. Völkel and J. Weigl: "Microscopy of Fibers, Fillers and Papers", Papiertechnische Stiftung, Munich, PTS-Manuscript PTS-MS 11 / 94-6 (1994)), birch and aspen have one Almost twice the volume of libriform fibers such as beech (for similar vessels or trachea volumes), (see Table 1)

Table 1: Percentage of libriform fibers or tracheids (in the case of softwoods) in volume percentages for different types of wood

According to the invention, woods with a high proportion by volume of libriform fibers, namely a volume fraction between 50 and 70% of libriform fibers, are used. These libriform fibers (closed tube cells) are at least predominantly closed chambers, and these remain even after bonding with a Einkomponentenpolyurethan adhesive without being penetrated or filled by the adhesive so that they in the finished composite material as an integrated air pump integrated air damper act. It is believed that the above relationships are responsible for obtaining a composite material with significantly improved static and dynamic properties.

These outstanding static and dynamic properties are used according to the invention by proposing the use of such a composite as a structural element in high-altitude, civil, marine, vehicle, aircraft, energy plant mining or furniture construction.

The wood used in the composite material according to the invention is particularly preferably birch wood.

Other preferred woods are aspen, eucalyptus, rubber tree, silk tree, cotton tree, acacia or poplar.

The composite material according to the invention preferably has 5 to 31 layers arranged one above the other.

Advantageously, a composite material can be provided which is characterized in that, in addition to the one or more layers of wood, one or more layers formed from a glass fiber fleece, a natural fiber fleece, a glass fiber mat or a natural fiber mat are provided.

Advantageously, in addition to the one or more layers of a wood one or more plastic layers, in particular one or more polyurethane and / or polyurea layers, in particular as a cover layer (s) may be provided.

It is also possible to coat the composite material on all sides with a plastic layer.

These additional plastic layers may in particular contain further, organic and / or inorganic fillers, for example organic rubber, and other rubber elastomers, clays, quartz sand, corundum, glass or other inorganic minerals or else all types of fibers.

In addition, one or more layers formed of a glass fiber nonwoven fabric, a natural fiber nonwoven fabric, a glass fiber mat, or a natural fiber mat may be formed therein Cover layers or even be provided in the composite itself together with or instead of wood.

According to the invention, the two or more layers of a wood, in particular birch, are bonded with a one-component polyurethane adhesive containing a prepolymer having free NCO groups.

The one-component polyurethane adhesive preferably contains the prepolymer with free NCO groups in an amount of up to 99% by weight, the prepolymer being obtainable from at least one component A which has an isocyanate-reactive compound and at least one isocyanate having component B,

From 0.1 to 40% by weight, preferably from 0.1 to 30% by weight, of a filler containing at least one fiber which, in addition to the fiber, contains at least one non-fibrous filler, from 0 to 20% by weight of conventional filler and auxiliaries, 0 to 20 wt .-% of an activator, and

wherein the at least one fiber has a diameter in the range of 5 to 100 microns and a length in the range of 0.02 to 6 mm.

In a further preferred embodiment, a one-component polyurethane adhesive is used without the addition of a filler containing a fiber. In particular, the one-component polyurethane adhesive contains the prepolymer in a proportion of up to 99.999% by weight, the prepolymer being obtainable from at least one component A having an isocyanate-reactive compound and at least one component B containing an isocyanate, and the one-component polyurethane adhesive

0 to 20 wt .-% of conventional additives and auxiliaries and

0.001 to 20% by weight of at least one activator selected from one or more of the following substances: 4-methylmorpholine, 4-ethylmorpholine, 4-cyclohexylmorpholine, 2,2'-dimorpholinodiethyl ether or dimorpholinopolyethylene glycol

a) the prepolymer has the following characteristics: i) an NCO content of 5 to 30 wt .-%, based on the prepolymer ii) a viscosity at 25 ° C in the range of 300 to 15,000 mPas, and

b) component A has the following characteristics: i) component A contains at least one diol, ii) the OH number of component A is in the range of 10 to 500 KOH / g, and

wherein the one-component polyurethane adhesive contains a filler and has a viscosity at 25 ° C in the range of 300 to 15,000 mPas.

The above preferred one-component polyurethane adhesives are described in EP 1072 620 and EP 1 072 621.

In the preparation of the prepolymer of the one-component polyurethane adhesive, the components A and B are preferably used in such a ratio that the above-described properties of the prepolymer, in particular the NCO content and the viscosity are achieved. In addition, auxiliaries and additives or catalysts can be used to prepare the prepolymer.

The further starting materials or components for the preparation of the prepolymer and adhesive composition are described below by way of example:

As isocyanate-reactive compounds, namely component A, it is expedient to use those having a functionality of from 2 to 8, preferably from 2 to 6, and a molecular weight of from 60 to 10,000, which are hydroxyl, thiol and / or isocyanate-reactive groups have primary and / or secondary amino groups. Have proven z. As polyols, selected from the group of polyetherols and polyesterols, Polythioetherpolyole, hydroxyl-containing polyacetals and hydroxyl-containing aliphatic polycarbonates, polycarbonatediols and Polycaprolactondiole or mixtures of at least two of said polyols. Preference is given to polyesterols and / or polyetherols. The hydroxyl number of the polyhydroxyl compounds is usually 20 to 850 mg KOH / g and preferably 25 to 500 mg KOH / g.

As isocyanate-reactive compounds it is also possible to use diols and / or triols having molecular weights of from 60 to <400 as chain extenders and / or crosslinking agents in the process according to the invention. To modify the mechanical properties, eg. As the hardness, and to increase the stability of the prepolymer, however, the addition of chain extenders, crosslinking agents or possibly also mixtures thereof may prove to be advantageous. The chain extenders and / or crosslinkers preferably have a molecular weight of 60 to 300 g / mol. Suitable examples include aliphatic, cycloaliphatic and / or araliphatic diols having 2 to 14, preferably 4 to 10 carbon atoms, for. As ethylene glycol, propanediol 1, 3, decane-1, 10, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably butanediol 1, 4, hexanediol-1, 6 and bis (2-hydroxy- ethyl) -hydroquinone, triols such as 1, 2,4-, 1, 3,5-trihydroxycyclohexane, glycerol and trimethylolpropane and low molecular weight hydro- xylgruppenhaltige polyalkylene oxides based on ethylene and / or 1, 2-propylene oxide and the aforementioned diols and / or triols as starter molecules.

Highly functional polyols, in particular polyetherols based on highly functional alcohols, sugar alcohols and / or saccharides as starter molecules, can generally also be used as polyol components. Preferably, however, 2- and / or 3-functional polyether or polyesterols based on glycerol and / or trimethylolpropane and / or glycols are used as starter molecules or alcohols to be esterified. The preparation of the polyetherols is carried out according to a known technology. Suitable alkylene oxides for preparing the polyols are, for example, tetrahydrofuran, ethylene oxide, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide, preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately in succession or as mixtures. Particular preference is given in the prepolymer in the adhesive composition of the invention as Polyethe- role used those which were alkoxylated to complete the alkoxylation with ethylene oxide and thus have primary hydroxyl groups.

Suitable starter molecules are, for example: water, glycols, such as ethylene glycol, propylene glycol, 1,4-butanediol and 1,6-hexanediol, amines, such as ethylenediamine, hexamethylenediamine, and 4,4'-diaminodiphenylmethane and amino alcohols, such as ethane nolamin or triethanolamine.

The polyetherols have a functionality of preferably 2 to 6 and in particular 2 to 3 and molecular weights of 400 to 10,000, preferably 1,000 to 7,000. The polyetherols can be used alone or in mixtures.

Polycarbonate diols are also suitable. As polycarbonate diols such come with aromatic dihydroxy compounds, for. B. based on 4,4'-dihydroxydiphenyl-2,2-propane or those based on aliphatic dihydroxy compounds, eg. B. 1, 6-hexanediol, in question. The molecular weights range from 500 to 4,000, preferably from 1,000 to 2,000.

Suitable polyesterols as the polyol component may be, for example, from organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids having 4 to 6 carbon atoms, and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms or by polymerization of lactones with 3 to 20 carbon atoms are produced. As dicarboxylic acids, for example, glutaric acid, pimelic acid, suberic acid, sebacic acid, dodecanoic acid and preferably adipic acid, succinic acid and phthalic acid can be used. The dicarboxylic acids can be used individually or as mixtures. For the preparation of the polyesterols, it may be advantageous, instead of the dicarboxylic acids, to use the corresponding acid derivatives, such as carboxylic acids. to use anhydrides or carboxylic acid chlorides. Suitable aromatic dicarboxylic acids are terephthalic acid, isophthalic acid or mixtures thereof with other dicarboxylic acids, eg. For example, diphenic acid, sebacic acid, succinic acid and adipic acid. Examples of suitable glycols are diethylene glycol, 1, 5-pentanediol, 1, 10-decanediol and 2,2,4-Trimenthylpentandiol-1, 5. Preferably used are 1, 2-ethanediol, 1, 4-butanediol, 1, 6-hexanediol and 2,2-dimethylpropanediol-1, 3; 1, 4-dimethylolcyclohexane; 1, 4-Diethanolcyclohexane, ethoxylated / propoxylated products of 2,2-bis (4-hydroxy-phenylene) -propane (bisphenol A). Depending on the desired properties of the polyurethanes, the polyols can be used alone or as a mixture in various proportions. As lactones for the preparation of polyesterols are z. B. α, α-dimethyl-β-propiolactone, γ-butyrolactone and preferably ε-caprolactone. The polyesterols preferably have a functionality of 2 to 4, in particular 2 to 3, and a molecular weight of 1,200 to 3,000, preferably 1,500 to 3,000 and in particular 1,500 to 2,500.

For the prepolymer in particular polyol mixtures have proven. Such polyol mixtures preferably have at least one diol, preferably polypropylene glycol, and at least one triol, preferably polyether triol. Particularly suitable diols have an average molecular weight in the range from 500 to 3,000, preferably 700 to 1,500 and particularly preferably 800 to 1,500 and moreover preferably 800 to 1,200. As triol, those having an average molecular weight of from 1,000 to 8,000, preferably from 2,000 to 6,000 and more preferably from 3,000 to 5,000 have proven useful. It is particularly preferred that the polyol mixture has an OH number in the range from 30 to 140, preferably 50 to 90 and particularly preferably 60 to 80 mg KOH / g. The abovementioned diols and triols can be used not only as a polyol mixture but also individually for the preparation of the prepolymer.

In another embodiment of the prepolymer, the use of a polyetherpolyol, which preferably has primary hydroxyl groups, with an OH number in the range of 10 to 60, preferably 20 to 40 and particularly preferably 25 to 35 mg KOH / g has proven.

If chain extenders, crosslinking agents or mixtures thereof are used to prepare the prepolymers, these are expediently used in an amount of from 0 to 20% by weight, preferably from 0.5 to 5% by weight, based on the weight of the total used Isocyanate-reactive compounds are used.

Suitable isocyanates or polyisocyanates of component B are the aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates known per se, preferably diisocyanates, which may, if appropriate, have been biuretized and / or isocyanurated by generally known processes. In detail, be Examples are: alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecane diisocyanate, 2-ethyltetramethylene diisocyanate-1,4-2-methylpentamethylene diisocyanate-1, 5, tetramethylene diisocyanate-1,4, lysine ester diisocyanate (LDI), Hexamethylene diisocyanate-1, 6 (HDI), cyclohexane-1, 3- and / or -1, 4-diisocyanate, 2,4- and 2,6-hexahydro-toluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2, 2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures, 1-isocyanato-S ^^ - trimethyl-δ-isocyanotomethylcyclohexane (IPDI), 2,4- and / or 2,6-tolylene diisocyanate, 4.4 '-, 2,4' and / or 2,2'-diphenylmethane diisocyanate (monomeric MDI), Polyphenylpolymethylenpolyisocyana- te, (polymer-MDI) and NDI, TODI, PPDI, etc. and / or mixtures containing at least two of said isocyanates. In addition, di- and / or polyisocyanates containing ester, urea, allophanate, carbodiimide, uretdione and / or urethane groups can be used in the process according to the invention.

Particularly preferred for the preparation of the prepolymer of the adhesive composition is MDI, such as polymeric MDI or preferably monomeric MDI, especially 4,4'-MDI, or mixtures of 2,4'-MDI and 4,4'-MDI.

In one embodiment, a polymer MDI having an average functionality in the range of 1 to 5, preferably 1, 5 to 4 and particularly preferably 2 to 3.5 and a viscosity in the range of 100 to 400 has proven particularly suitable for the prepolymer , preferably 150 to 300 and particularly preferably 160 to 260 mPas to use.

As catalysts, it is possible to use generally known compounds which greatly accelerate the reaction of isocyanates with the compounds reactive toward isocyanates, preferably a total catalyst content of from 0.01 to 8% by weight, in particular from 0.1 to 5% by weight on the weight of the total isocyanate-reactive compounds used. For example, the following compounds can be used: triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N, N, N ', N'-tetramethyl-diamino-diethyl ether, bis (dimethylaminopropyl) -urea, N-methyl or N Ethylmorpholine, N, N'-dimorpholinodiethyl ether (DMDEE), N-cyclohexylmorpholine, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N'-tetramethylbutanediamine, N, N, N ', N' Tetramethylhexanediamine-1, 6, pentamethyldiethylenetriamine, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1, 2-dimethylimidazole, N-hydroxypropylimidazole, 1-azabicyclo- (2,2,0) -octane, 1,4-diazabicyclo- (2, 2,2) -octane (Dabco) and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyl-diethanolamine, dimethyl-aminoethanol, 2- (N, N-dimethylaminoethoxy) ethanol, N, N ', N-tris (dialkylaminoalkyl) hexahydrotriazines, e.g. N, N ', N-Tris

(Dimethylaminopropyl) -s-hexahydrotriazine, iron (II) chloride, zinc chloride, lead octoate, and preferably tin salts, such as tin dioctoate, tin diethylhexoate, dibuthyltin dilaurate and / or dibutyldilauryltin mercaptide, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, alkali metal alkoxides, such as sodium methylate and potassium isopropylate, and / or alkali metal salts of long-chain fatty acids containing from 10 to 20 carbon atoms optionally pendant OH groups. Furthermore, trimerization catalysts such as alkali metal or alkaline earth metal acetate, preferably potassium acetate, may be mentioned. The above catalysts can also be used as an activator for the morpholine derivatives used as activators. Thus, catalysts are incorporated in the prepolymer as such in its preparation and activators with the prepolymer as an additional component of the adhesive composition according to the invention in this. Also suitable as catalysts or activators Ti compounds, in particular Ti (IV) -O-alkyl compounds, with alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl, preferably ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl and particularly preferably Ti (IV) butoxide, proven.

Optionally, further auxiliaries and / or additives may also be added to the reaction mixture for the preparation of the prepolymers. Mention may be made, for example, of surface-active substances, stabilizers, cell regulators, dyes, pigments, flame retardants, hydrolysis protectants, insecticides, fungistatic and bacteriostatic substances. The surface-active substances and stabilizers counteract the "skin formation" of the air-facing surface of the adhesive composition.Furthermore, the surface-active substances and stabilizers improve the running of the adhesive composition and the creeping ability of the adhesive composition and the degassing thereof These include, for example, emulsifiers, such as the sodium salts of castor oil sulfates or of fatty acids and salts of fatty acids with amines, for example diethylamine, stearic diethanolamine, diethanolamine, salts of Sulfonic acids, for example alkali metal or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid, stabilizers, such as siloxane-oxalkylene copolymers and other organopolysiloxanes, ethoxylated alkylphenols, oxethyl fatty alcohols, paraffin oils, castor oil or ricinoleic acid esters, Turkish red oil and peanut oil, and cell regulators, such as paraffins, fatty alcohols and dimethylpolysiloxanes. To improve the emulsifying effect, the cell structure and / or stabilization of the prepolymer, the above-described oligomeric acrylates having polyoxyalkylene and fluoroalkane radicals are also suitable as side groups. If foam formation is to be reduced or avoided, trialkyl phosphates are preferred as defoamers. These preferably have alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl,

Pentyl, preferably ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl. The surface-active substances are usually used in amounts of from 0.01 to 5% by weight, based on 100 wt .-% of total used, isocyanate-reactive compounds used.

Suitable flame retardants are, for example, tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate, Tetrakis (2-chloroethyl) ethylene diphosphate, dimethyl methane phosphonate, Diethanolaminomethylphosphonsäurediethylester and commercially available halogen-containing flame retardant polyols. In addition to the aforementioned halogen-substituted phosphates, inorganic or organic flame retardants, such as red phosphorus, alumina hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite or cyanuric acid derivatives, such as. As melamine, or mixtures of at least two flame retardants, such as. As ammonium polyphosphates and melamine and optionally corn starch or ammonium polyphosphate, melamine and expandable graphite and / or optionally aromatic polyesters to increase the flame resistance of the prepolymer or the adhesive composition can be used. In general, it has proven expedient to use 5 to 50% by weight, preferably 5 to 25% by weight, of the flame retardants mentioned, based on the weight of the total isocyanate-reactive compounds used.

In a further preferred embodiment, a one-component polyurethane adhesive is used which has a filler containing at least one fiber.

The one-component polyurethane adhesive preferably has at least one of the following main features (i) to (iii):

(i) the prepolymer has at least one of the following sub-features (a) and (b):

(a) an NCO content of 5 to 30 wt .-%, based on the prepolymer, (b) a viscosity at 25 ⁰ C in the range of 300 to 150,000 mPas,

(ii) Component A has at least one of the following sub-features (c) and (d):

(c) the component A contains at least one diol or polyol, preferably a diol or triol and more preferably a diol and triol,

(d) the OH number of component A is in the range of 10 to 500 mg KOH / g,

(iii) the filler has at least one of the following sub-features (e) or (f):

(e) the fiber consists of at least one fiber polymer, (f) the filler consists, in addition to the fiber, of at least one non-fibrous packing. The viscosity at 25 ° C of the prepolymer is preferably in a range between 300 and 15,000, preferably 500 and 10,000 mPas, if the adhesive composition is to be pumpable. If, on the other hand, it is intended to use the adhesive composition as a pasty, coatable composition, the viscosity at 25 ° C. of the prepolymer is preferably in the range> 15,000 to 150,000 and particularly preferably in the range from 20,000 to 100,000 mPas.

Furthermore, it is preferred that the adhesive composition is low in solvent. This is the case when the amount of solvent contained in the adhesive composition is <10, preferably <5 and particularly preferably <2% by weight. According to the invention, solvents are organic and inorganic liquids which are suitable as carriers of the other constituents of the adhesive composition and do not cure with at least some of the other constituents.

Preferably, the adhesive composition is solvent-free.

In an advantageous embodiment of the adhesive composition, both the aforementioned main feature of the prepolymer (i) and the main feature (ii) of the component A are realized.

In another embodiment of the adhesive composition, the main feature (ii) of the component A and the main feature of the filler (iii) are fulfilled.

In another embodiment of the adhesive composition, all three main features (i) to (iii) are satisfied.

Preferred embodiments of the adhesive composition are those in which both the sub-features (a) and (b) or (c) and (d) or (e) and (f) are fulfilled in the prepolymer, component A and the filler.

In another preferred embodiment of the adhesive composition, all the main features (i) to (iii) as well as all sub-features (a) to (f) are satisfied.

In a further embodiment of the adhesive composition in addition to the features (i) to (iii) at least one of the features (iv) and (v) is fulfilled:

(iv) the fiber polymer is at least one polyamide,

(v) the filler is composed of at least one inorganic material.

It is preferred that the fiber polymers of the adhesive composition be formed predominantly of organic or inorganic materials. As organic materials for fiber polymers in particular polycondensates and polyaddition polymers, which are preferably not polyurethane, with polycondensates being preferred. As polycondensates, polycarbonates, polyesters, polyamides, polyimides, melamine-formaldehyde resin are particularly suitable.

Polyaddition polymers are in particular polyacrylates, polymethacrylates, polystyrenes, polyacrylonitriles, polyethylene, polypropylene, polyvinyl alcohol and the copolymers of at least two monomers of the abovementioned unipolymers and their blends of at least two thereof.

In the adhesive composition, it is particularly preferable that a polyamide is used as the fiber polymer. For this purpose, all known in the art, commercially available polyamides are suitable. However, polyamides such as nylon, in particular nylon-6,6 or nylon-6 and polyaramides have proven particularly suitable.

Furthermore, the fibers may be based on natural organic fiber polymers such as cellulose, cotton, jute, viscose and sisal. In addition, the fibers can also be formed from inorganic materials. As the inorganic fiber polymers, carbon, glass and mineral wool fibers are preferable. Furthermore, it is possible that the fibers are obtained from different materials, for example by spinning.

The fibers used preferably have a diameter in the range of 5 to 100, preferably 10 to 60 and particularly preferably 10 to 30 .mu.m and a length in the range of 0.02 to 6, preferably 0.05 to 4 and particularly preferably 0.1 to 2 mm.

In addition, the adhesive composition has a non-fibrous packing consisting of at least one inorganic material. Basically, all known to the expert and in particular the commercially available inorganic materials for the adhesive according to the invention are suitable, which are present as a solid. In particular, the inorganic materials must be present as a solid in the temperature range in which the adhesive composition according to the invention is processed and the bonded article is used later. This temperature range preferably starts at -50 and reaches +160 ⁰ C.

Particularly suitable inorganic materials have proven to be the oxygen compounds of silicon or aluminum, or magnesium or at least two thereof, which optionally also have further elements. Particularly suitable are silicates and aluminum oxides, for example alumina, such as China clay, and quartz compounds or silica. The non-fibrous filling bodies are preferably particulate. 80% of the particulate fillers have a particle size in the range from 0.01 to 50, preferably 0.1 to 10 and particularly preferably 0.2 to 8 μm.

The filler used according to the invention may comprise fibers or additionally fillers. If the filler has both fibers and filler, it is preferred that at least as much filler as fibers, preferably filler in excess, are found in the filler.

In particular, fillers are included in the adhesive composition to improve their physical properties for the various uses. For this purpose, the adhesive composition must form a compact as possible, bubble-free adhesive layer after curing and the joints between the substrates must be filled as completely as possible. To increase adhesion, the adhesive composition should partially penetrate the substrate surface. However, after curing of the adhesive composition to the adhesive, it is not allowed to cause voids through this infiltration or shrinkage, which could degrade the cohesion. Especially in thicker joints, in the range of greater than 0.1 to 1 mm, preferably 0.2 to 1 mm, these requirements can be met particularly well by the incorporation of fillers in the composition described above in the adhesive composition.

In the case of the fillers contained in the adhesive compositions, it has proven particularly advantageous that they have a water content of less than 5, preferably less than 1, and particularly preferably less than 0.1,% by weight, based on the filler. This is particularly advantageous with regard to the preparation of the adhesive composition according to the invention.

The activator of the adhesive composition consists of at least one morpholine derivative. Particularly suitable as morpholine derivatives are 4-methylmorpholine, 4-

Ethylmorpholine, 4-cyclohexylmorpholine, 2,2'-dimorpholinodiethylether or dimorpholino-polyethylene glycol, or at least two of them. Furthermore, in addition to the morpholine derivative, further activating compounds can be used, as described, for example, as polyurethane catalysts in Becker / Braun, Kunststoffhandbuch 7 (1993), the proportion of the morpholine derivatives preferably predominating.

Advantageously, in particular with regard to storage stability, thixotropic adjuvants have proved themselves. Particularly preferred thixotropic auxiliaries are bentonites, kaolins, alginic acid and silicic acid, with silicic acid being particularly preferred. In addition to or instead of the abovementioned thixotropic adjuvants consisting of solids, soluble thixotropic adjuvants are preferred which, for example, comprise the reaction of an isocyanate in the presence of amines can be obtained, as described in the publications EP 300 388 A1, DD 156 480, DD 211 689, DD 211 930 and DD 211 931.

Thixotropic auxiliaries are very finely divided substances which already thicken liquids when they are added in small amounts to the liquid, for example up to a maximum of 10% by weight, based on the liquid. Preferably, these small particles have silane groups on their surface, which interact with the liquid with which they are dispersed with formation of hydrogen bonds and thus lead to a thickening of this liquid. Typical of thixotropic auxiliaries is that, for the same amount, the thickening effect increases with decreasing particle size with correspondingly thorough dispersion by vigorous mixing. Furthermore, the thixotropic aids have the advantage that they do not sediment in the dispersed liquid. In addition, the thixotropic adjuvants prevent or delay the sedimentation of fillers. As materials for thixotropic aids are in fine powder form montmorillonite, Mg / Al silicate, Al / Na silicate, bentonites, hectorite, Na / Mg silicate, fumed silicas, hydrated silicas, hornblende chrysotile, chrysotile asbestos, chrysotile Silica and precipitated MgO are preferred, pyrogenic silicas, for example obtainable as Aerosil from Degussa-Hüls AG, and Mg silicates, available as Bentones from Kronos Titan GmbH Leverkusen, being preferred, and Aerosil being particularly preferred.

Claims

claims

1. A composite material comprising two or more layers of a wood arranged one above the other, the layers being provided with one another with a one-component polyurethane adhesive containing a prepolymer with free NCO-

Groups are connected, characterized in that a wood is used with a volume fraction of Libriformfasern in the range of 50 to 70%.

2. Composite material according to claim 1, characterized in that the wood with a volume fraction of Libriformfasern in the range of 50 to 70% birch wood.

3. Composite material according to claim 1, characterized in that the wood with a volume fraction of libriform fibers in the range of 50 to 70% wood is one of the trees listed below: aspen, eucalyptus, rubber tree, silk tree, cotton tree, acacia or poplar.

4. Composite material according to one of claims 1 to 3, characterized in that the one-component polyurethane adhesive contains the prepolymer with free NCO groups in an amount of up to 99.9 wt .-%, wherein the prepolymer is available from at least a component A having an isocyanate-reactive compound and at least one isocyanate-containing component B,

From 0.1 to 20% by weight of a filler containing at least one fiber which contains at least one non-fibrous filler in addition to the fiber,

0 to 20 wt .-% of conventional additives and auxiliaries, 0 to 10 wt .-% of an activator, and

5. A composite material according to any one of claims 1 to 3, characterized in that the one-component polyurethane adhesive contains the prepolymer in a proportion of up to 99.999 wt .-%, the prepolymer is obtainable from at least one isocyanate-reactive compound component A and at least one isocyanate-containing component B, and wherein the one-component polyurethane adhesive

0 to 20 wt .-% of conventional additives and auxiliaries and 0.001 to 20% by weight of at least one activator selected from one or more of the following substances: 4-methylmorpholine, 4-ethylmorpholine, 4-cyclohexylmorpholine, 2,2'-dimorpholinodiethyl ether or dimorpholinopolyethylene glycol

a) the prepolymer has the following characteristics: i) an NCO content of 5 to 30 wt .-%, based on the prepolymer, ii) a viscosity at 25 ° C in the range of 300 to 15000 mPas, and b) the component A. having the following characteristics: i) component A contains at least one diol, ii) the OH number of component A is in the range from 10 to

500 KOH / g, and wherein the one-component polyurethane adhesive contains a filler and has a viscosity at 25 ° C in the range of 300 to 15,000 mPas.

6. Composite material according to one of claims 1 to 5, characterized in that in addition to the one or more layers of wood, one or more plastic layers, in particular a polyurethane and / or polyurea cover layer, is provided.

7. A composite material according to any one of claims 1 to 6, characterized in that in addition to the one or more layers of wood one or more layers are formed from a glass fiber fleece, a natural fiber fleece, a glass fiber mat or a natural fiber mat are provided.