NO326178B1 - Fiber-containing adhesive mixture - Google Patents

Abstract

Adhesive compositions (I) containing: (a) up to 99.9 wt.% prepolymer derived from: (A) compound(s) which react with isocyanate; and (B) an isocyanate component; (b) 0.1-20 wt.% fibre-containing filler; (c) 0-20 wt.% conventional additives and auxiliary substances; and (d) 0-10 wt.% activator. Independent claims are also included for : (i) a method for the production of (I) by bringing the above components into contact with one another; (ii) adhesive compositions (I) obtained by this method; (iii) composites comprising (at least) a substrate and a composition (I); (iv) building, civil engineering, boat, vehicle or aircraft constructions incorporating compositions (I) or composites (iii), preferably in glued wood laminates.

Description

The invention relates to an adhesive mixture, a method for preparing the mixture, a composite comprising the mixture, and use of the adhesive mixture or of the composite in building construction, engineering engineering, for marine construction, in the construction of aircraft or in the manufacture of motor vehicles.

Wood is a recognized and established material in structural architecture. For the realization of larger spans than those that can be achieved with single-cut beams, glued, laminated wood is used. Glued laminated wood is produced industrially by gluing individual plank layers over their entire area. By means of glued joints of short wooden layers in the longitudinal direction, known as finger jointing, it is possible to produce individual layers of practically unlimited length, and these are conventionally cut across to the required size for the structural component. In addition to larger dimensions, gluing leads to an improvement of wood as a natural substance, as naturally occurring irregularities such as twigs are cut out, and shrinkage and swelling of the wood as a result of climatic changes is significantly reduced.

For such purposes, it is now common to use adhesive mixtures which are primarily based on resins of phenol/resorcinol and/or melamine/urea.

The gluing systems that are predominantly used today are amino resins and phenolic resins which harden in a polycondensation reaction to give the finished glued joint. The chemical curing reaction for these systems, which are predominantly two-component, is initiated by mixing adhesive and curing agent to form the adhesive liquid. In the case of amino resins, curing is generally initiated by lowering the pH; in the case of phenolic resins by adding formaldehyde or paraformaldehyde. Even in the finished linen joint there are still small amounts of free formaldehyde, which can be released into the surrounding air over a long period of time. However, formaldehyde is considered harmful to health.

DE 4 412 759 A1 describes a formaldehyde-free adhesive mixture based on an isocyanate-containing polyurethane prepolymer. This adhesive mixture in particular has a viscosity that is rather unsuitable for processing, and a pressing time that is foreign to practice. The viscosity is of great importance, especially for pumpability and the ability of the adhesive mixture to penetrate the substrate to be bonded (adhesion).

It is an object of the present invention to provide an adhesive composition which has no formaldehyde emissions.

It is a further object of the invention that the provided adhesive mixture should have good pumpability and workability, and in particular a suitable viscosity. As far as processing is concerned, it is particularly a further object of the invention that when gluing laminated planks it should be possible to apply the adhesive mixture in elongated forms, especially lumps, on the surface of the wooden planks using, in most cases, nozzle-like application devices. In this context, it is particularly important that application takes place in a reproducible manner, without pulsation, and preferably in a particularly uniform manner, which is possible preferably with a device described in the journal "Holzzentralblatt", October 11, 1996.

It is a further object of the invention to improve the storage stability of adhesive compositions based on polyurethane prepolymers.

It is also an object of the invention that the adhesive mixture should be able to be used as a one-component system.

It is a further object of the invention that the adhesive mixtures provided in accordance with the invention shall satisfy the requirements that above all exist in construction engineering and engineering, especially imposed by national test institutions, to at least the same extent as they are fulfilled by the adhesive mixtures used until now, especially the adhesive compositions based on phenol/resorcinol and melamine/urea resins, in comparable applications.

We have found that the above stated objects are achieved by means of an adhesive composition comprising at least: up to 99.9% by weight of the adhesive composition of a prepolymer obtainable from at least one component A comprising an isocyanate reactive compound and at least one component B comprising an isocyanate,

from 0.1 to 20% by weight of at least one fibrous filler which comprises at least one fiber and in addition to the fiber contains at least one non-fibrous filler element,

from 0 to 20% by weight of common additives and auxiliaries,

from 0 to 10% by weight of an activator,

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

According to the invention, it is preferred that the adhesive mixture comprises in the range from 70 to 99, preferably from 80 to 94, and particularly preferred from 85 to 90% by weight of the prepolymer, and from 1 to 17, preferably from 5 to 17, and particularly preferred from 6 to 15% by weight of said at least one fibrous filler, as well as from 0 to 5, preferably from 0.01 to 3, and particularly preferred from 0.01 to 1% by weight of the activator and, if desired, up to 20% by weight of additional additives and auxiliaries, in each case based on the adhesive mixture.

In the adhesive mixture according to the invention, at least one of the following principal features (i) to (iii) is also preferred:

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

(a) an NCO content of from 5 to 30% by weight, based on the prepolymer,

(b) a viscosity at 25°C in the range of 300 to 150,000 m-Pas;

(ii) component A has at least one of the following subsidiary features (c) and (d):

(c) component A comprises at least one diol or polyol,

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

(iii) the filler has the following subsidiary feature (e):

(e) the fiber comprises at least one fiber polymer.

The viscosity at 25°C for the prepolymer is preferably in a range from 300 to 15,000, preferably 500 to 10,000 m-Pas, if the adhesive mixture is to be pumpable. If, however, the purpose is to use the adhesive mixture as a pasty mixture which can be applied with a casting spoon, then the viscosity at 25°C for the prepolymer is preferably in the range > 15,000 to 150,000 and particularly preferred in the range from 20,000 to 100,000 m-Pas.

Furthermore, according to the invention, it is preferred that the adhesive mixture has a low solvent content. This is the case if the amount of solvent present in the adhesive mixture is < 10, preferably < 5, and particularly preferably < 2% by weight. Solvents are - in accordance with the invention - organic and inorganic liquids which are suitable as carriers for the other components in the adhesive mixture, and which do not harden with at least some of the other components.

The adhesive mixture according to the invention is preferably solvent-free.

In one embodiment of the adhesive mixture in accordance with the invention, both the above-mentioned most important features of the prepolymer (i) and the most important feature (ii) of component A are realized.

In another embodiment of the adhesive mixture in accordance with the invention, the most important feature (ii) of component A and the most important feature of the filler (iii) are realized.

In another embodiment of the adhesive mixture according to the invention, all the three most important features (i) to (iii) are realized.

Preferred embodiments of the adhesive composition are those where, in conjunction with the prepolymer, component A and the filler, in each case two subsidiary features (a) and (b) and/or (c) and (d) and/or (e) and (f ) is realized.

In another preferred embodiment of the adhesive mixture according to the invention, not only all the main features (i) to (iii) but also all subsidiary features (a) to (f) are realized.

In another embodiment of the adhesive mixture according to the invention, not only the features (i) to (iii), but also at least one of the features (iv) and (v) are realised:

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

(v) the filler element comprises at least one inorganic material.

It is preferred that the fiber polymers in the adhesive mixture are mainly formed from organic or inorganic materials. Particularly suitable organic materials for fiber polymers are polycondensates and polyaddition polymers, which are preferably not polyurethane, with polycondensates being preferred. Particularly suitable polycondensates are polycarbonates, polyesters, polyamides, polyimides, and melamine-formaldehyde resin.

Polyaddition polymers are in particular polyacrylates, polymethacrylates, polystyrenes, polyacrylonitriles, polyethylene, polypropylene, polyvinyl alcohol, and the copolymers of at least two monomers of the above-mentioned homopolymers, as well as mixtures of at least two thereof.

In the adhesive mixture according to the invention, it is particularly preferred that the fiber polymer used is a polyamide. Suitable for this purpose are all commercially common polyamides known to the person skilled in the art. However, those which have proven to be particularly suitable are polyamides such as nylon, especially nylon 6,6 or nylon 6, as well as polyaramids.

The fibers can also consist of, or be based on, natural organic fiber polymers, for example cellulose, cotton, jute, viscose and sisal. The fibers can also be formed from inorganic materials. Preferred inorganic fiber polymers are carbon fibers, glass fibers and mineral wool fibers. It is also possible to obtain the fibers from different materials, by e.g. spinning.

The fibers used in accordance with the invention preferably have a diameter in the range from 5 to 100, more preferably from 10 to 60, and particularly preferably from 10 to 30 µm, and a length in the range from 0.02 to 6, preferably from 0.05 to 4, and particularly preferably from 0.1 to 2 mm.

The adhesive mixture according to the invention can further comprise a filler element comprising at least one inorganic material. In principle are suitable

inorganic materials for the adhesive according to the invention all those known to the person skilled in the art and which are in solid form, especially those which are commercially available. The inorganic materials must in particular be solid within the temperature range where the adhesive mixture according to the invention is processed and the bonded object is then used. This temperature range preferably starts at -50 and goes all the way up to +130°C.

Inorganic materials which have proved particularly suitable are the oxygen compounds of silicon or aluminium, of magnesium or of at least two of these, and which may further include other elements in addition. Particularly suitable are silicates and aluminum oxides, for example aluminum oxide, such as kaolin, and quartz compounds or silica.

The non-fibrous filler elements are preferably particulate. 80% of the particulate filler elements have a particle size in the range from 0.01 to 50, preferably from 0.1 to 10, and particularly preferably from 0.2 to 8 pm.

The filler used in accordance with the invention may comprise fibers or further filler elements. If the filler comprises both fibers and filler elements, it is preferred that there are at least as many filler elements as fibres, preferably with filler elements in excess, in the filler.

Fillers are present in the adhesive composition according to the invention specifically to improve the physical properties for various applications. For this purpose, after curing, the adhesive mixture must form a very compact adhesive film without air bubbles, and the joints between the substrates must be as completely filled as possible. To enhance adhesion, the adhesive mixture should penetrate all the way to the substrate surface. However, after the curing of the adhesive mixture to form the adhesive, this penetration, or shrinkage, must not cause voids that could impair cohesion. Especially in relatively thick joints, in the range above 0.1 to 1 mm, preferably from 0.2 to 1 mm, these requirements must be met particularly effectively by incorporating fillers, in the mixture described above, in the adhesive mixture.

As regards the fillers present in the adhesive mixtures according to the invention, it has been found to be particularly suitable for them to 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 advantageous, especially when it comes to the production of the adhesive mixture according to the invention.

The activator for the adhesive mixture according to the invention comprises at least one morpholine derivative. Particularly suitable morpholine derivatives are 4-methylmorpholine, 4-ethylmorpholine, 4-cyclohexylmorpholine, 2,2'-dimorpholine diethyl ether and dimorpholine polyethylene glycol, or at least two of them. In addition to the morpholine derivative, it is also possible to use further activating compounds as described for example as polyurethane catalysts in Becker/Braun, Kunststoffhandbuch 7 (1993), with the proportion of the morpholine derivatives being preferably dominant.

Thixotropic adjuvants have been found to be beneficial, particularly with respect to storage stability. Particularly preferred thixotropic aids are bentonites, kaolins, alginic acid and silica, silica being particularly preferred. In addition to or instead of the above-mentioned thixotropic auxiliaries, which consist of solids, soluble thixotropic auxiliaries which can be obtained for example by reaction of an isocyanate in the presence of amines, as described in the publications EP 300 388 A1, DD 156 480 , DD 211 689, DD 211 930 and DD 211 931.

Thixotropic aids include very finely divided substances that thicken liquids even when added to the liquid in small amounts, for example up to a maximum of 10% by weight, based on the liquid. Preferably, these small particles have silanol groups on their surface, which interact with the liquid with which they are dispersed, to form hydrogen bonds, which thus leads to thickening of this liquid. A characteristic of thixotropic aids is that, for a given amount, the thickening effect increases with decreasing particle size if the dispersion is carried out thoroughly by intimate mixing. Furthermore, the thixotropic aids have the advantage that they do not sediment in the dispersed liquid. Furthermore, the thixotropic aids prevent or delay the sedimentation of fillers. Preferred materials for thixotropic aids, in the form of fine powder, are montmorillonite, Mg/AI silicate, AI/Na silicate, bentonites, hectorite, Na/Mg silicate, pyrogenic silicas, hydrated silicas, hornblende chrysotile, chrysotile asbestos , chrysotile silica and precipitated MgO, and particularly preferred are fumed silicas, available for example as Aerosil from Degussa-Huls AG, and Mg silicates, available as bentone from Kronos Titan GmbH Leverkusen, and particularly preferred is Aerosil.

The adhesive mixture according to the invention is prepared by bringing the above defined components into contact with each other. This is preferably done in the presence of mixing devices, as it is possible to use not only dynamic, but also static, preferably dynamic, mixing devices.

The prepolymer according to the invention is preferably obtained by introducing component B, preferably a monomeric isocyanate, and adding component A, preferably a suitable alcohol, in a temperature range between 20 and 120, preferably from 40 to 100, and particularly preferably from 60 to 90 °C, in a reactor with a mixing device.

The components are preferably mixed with each other using the mixing device in such a thorough manner that it is possible to obtain an extremely homogeneous adhesive mixture from the components.

The adhesive mixture according to the invention has at least one of the following material properties (g) to (m): (g) initial drying time under standard conditions 20/65-1 in accordance with

DIN 50014 at an application rate of 250 g/m<2> in the range from 20 to 40,

(h) initial drying time under standard conditions 20/65-1 in accordance with

DIN 50014 at an application rate of 400 g/m<2> in the range from 20 to 40,

(i) viscosity at 25°C in the range from 300 to 150,000 m-Pas;

(k) storage stability of from 1 to 4;

(I) NCO content in the range from 3 to 20, wt%, based on

the adhesive mixture,

(m) minimum pressing time in accordance with DIN 68141 in the range from 5 to 8.

The viscosity at 25°C of the adhesive composition is preferably within a range from 300 to 15,000, more preferably from 500 to 10,000 m-Pas for pumpable adhesive compositions. If, on the other hand, it is intended that the adhesive mixture should have a paste-like composition suitable for application with a spoon, the viscosity at 25°C for the adhesive mixture is preferably in a range from 15,000 to 150,000 and particularly preferably from 20,000 to 100,000 m-Pas.

The storage stability of the adhesive mixture is determined by the sedimentation behavior of the fillers. Storage stability is therefore present in accordance with the invention if the phase separation is monitored for a given period in a container completely filled with adhesive and with a seal that is moisture-tight and air-tight and the drop in the phase boundary (deposition of fillers) is less than 5%, based on the original filler level.

Of the above features, one preferred embodiment of the adhesive mixture according to the invention has at least the viscosity (i) and the storage stability (k).

Of the above features, another preferred embodiment of the adhesive mixture according to the invention has at least the viscosity (i) and the storage stability (k) as well as the minimum pressing time (m).

Of the above-mentioned material properties, one embodiment of the adhesive mixture according to the invention also has at least the viscosity (i), the storage stability (k) and the NCO content (I).

Of the above-mentioned material properties, one embodiment of the adhesive mixture according to the invention has at least the viscosity (i), the storage stability (k), the NCO content (I) and the minimum pressing time (m).

Another preferred embodiment of the adhesive mixture according to the invention has all the above-mentioned material properties (g) to (m).

The invention also provides a composite comprising at least one substrate and an adhesive mixture according to the invention. The substrate is preferably a cellulose material. Suitable cellulose materials are all naturally occurring and artificially produced cellulose materials that are known to the person skilled in the field. As naturally occurring materials, wood of different types of wood, for example hard wood and soft wood, can be mentioned in particular. Examples of synthetic cellulose materials are paper, plates, laminates, cardboard and the like. In the same way, suitable substrates include materials which can be similarly bonded with the adhesive mixture according to the invention to the cellulose materials.

One preferred composite comprises continuous wooden planks comprising at least two individual planks joined together at their end pieces by

using a finger joint, the fingers being joined using the adhesive mixture according to the invention.

A composite which is also preferred in accordance with the invention comprises glued laminated wood comprising a large number of individual planks which are glued to the surface, the planks being at least partially joined to each other, preferably completely, by means of the adhesive mixture according to the invention. Instead of individual planks, it is also possible to use continuous wooden planks.

The adhesive mixture according to the invention is particularly suitable for the production of glued laminated wood.

Furthermore, the present invention includes the use of an adhesive mixture as described above in building construction, engineering, for marine constructions, in the construction of motor vehicles or aircraft, preferably in glued laminated wood.

Building construction, engineering or marine structure, motor vehicle or aircraft structure, preferably in glued laminated wood are also described in the present invention where these comprise an adhesive mixture or a composite as described above.

In addition to the use of the composites as load-bearing components in roofing structures, bridging structures and sealing structures, the composites according to the invention are also suitable for use in the production of concrete formwork, especially as supporting concrete formwork, as well as in scaffolding, especially as scaffolding platforms.

It is further preferred that the composite according to the invention has at least one of the following material properties: (n) a delamination ring resistance in accordance with DIN EN 302 part 2 of no more than 5% in accordance with DIN EN 301, preferably no more than 3%, and

particularly preferably not more than 1%,

(o) a dry shear strength in the range from at least 6 N/mm<2> up to a maximum with substrate failure in accordance with the guidelines for quality according to the RAL Gutegemeinschaft Holzleimbau [Glued Wood Construction Quality Association].

The substrate breaking values and the shear strength values for different types of wood can be found in the Holzlexikon [Wood Dictionary] from DRW-Verlag, 3rd ed.1998. substrate break-

that for the type of wood that is usually used for glued laminated wood, spruce, is approx.

7.5 N/mm<2.>

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

Additional starting materials and components for the production of the prepolymer mixture and the adhesive mixture are described with the help of the following example: As isocyanate-reactive compounds, namely component A, it is possible that it makes sense to use those that have a functionality of from 2 to 8, preferably from 2 to 6, and a molecular weight of from 60 to 10,000, whose isocyanate-reactive groups comprise hydroxyl, thiol and/or primary and/or secondary amino groups. Examples of those which have proven to be suitable are polyols, selected from the group of polyetherols, one example being polytetrahydrofuran, and polyesterols, polythioether polyols, hydroxyl-containing polyacetals and hydroxyl-containing aliphatic polycarbonates, or mixtures of at least two of the aforementioned polyols. Preferably, polyesterols and/or polyetherols are used. The hydroxyl number of the polyhydroxy compounds is generally from 20 to 850 mg KOH/g and preferably from 25 to 500 mg KOH/g.

As isocyanate-reactive compounds, it is also possible to use diols and/or triols with molecular weights of from 60 to < 400 as chain extenders and/or cross-linking agents in the method according to the invention. To modify the mechanical properties, e.g. hardness, and to increase the stability of the prepolymer, it may however prove advantageous to add chain extenders, cross-linking agents, or, if desired, mixtures thereof. The chain extenders and/or cross-linking agents preferably have a molecular weight of from 60 to 300 g/mol. Suitable examples include aliphatic, cycloaliphatic and/or araliphatic diols with 2 to 14, preferably 4 to 10 carbon atoms, e.g. ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m- and p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and, preferably, 1,4-butanediol, 1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone , triols, such as 1,2,4- and 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane, and hydroxyl-containing polyalkylene oxides of low molecular weight, based on ethylene oxide and/or 1,2-propylene oxide and the above-mentioned diols and/or triols which starting molecules.

As polyol components, it is also generally possible to use polyols with high functionality as starting molecules, in particular polyetherols based on alcohols with high functionality, sugar alcohols and/or saccharides. Preferably, however, di- and/or trifunctional polyetherols and/or polyesterols based on glycerol and/or trimethylolpropane and/or glycols are used as starting molecules or as alcohols for esterification. The polyetherols are produced in accordance with known techniques. Examples of suitable alkylene oxides for the production of the polyols are tetrahydrofuran, ethylene oxide, 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, styrene oxide, preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately, or as mixtures. In the prepolymer in the adhesive mixture according to the invention, those polyetherols are particularly preferred which towards the end of the alkoxylation have been alkoxylated with ethylene oxide and thus have primary hydroxyl groups.

Examples of suitable starting molecules are the following: 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 such as ethanolamine and triethanolamine.

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

Polycarbonate diols are also suitable. Suitable polycarbonate diols include those with aromatic dihydroxy compounds, based for example on 2,2-bis(4-hydroxyphenyl)propane, or those based on aliphatic dihydroxy compounds, e.g. 1,6-hexanediol. The molar masses range from 500 to 4,000, preferably from 1,000 to 2,000.

Suitable polyesterols as a polyol component can for example be produced from organic dicarboxylic acids with 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids with 4 to 6 carbon atoms, and polyhydric alcohols, preferably diols, with 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, by polymerization of lactones with 3 to 20 carbon atoms. As dicarboxylic acids, it is for example possible to use glutaric acid, pimelic acid, suberic acid, sebacic acid, dodecanoic acid and preferably adipic acid, succinic acid and phthalic acid. The dicarboxylic acids can be used individually or as mixtures. To prepare the polyesterols, if desired, it may be advantageous to use, instead of the dicarboxylic acids, the corresponding acid derivatives, such as carboxylic acid anhydrides or carbonyl chlorides. Suitable aromatic dicarboxylic acids are terephthalic acid, isophthalic acid or mixtures of these with other dicarboxylic acids, e.g. 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-trimethyl-1,5-pentanediol. It is preferred to use 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol and 2,2-dimethyl-1,3-propanediol; 1,4-Dimethylolcyclohexane; 1,4-diethanolcyclohexane, ethoxylated/propoxylated products of 2,2-bis(4-hydroxyphenylene)propane (bisphenol A). Depending on the desired properties for the polyurethanes, it is possible to use the polyols alone or as a mixture in different ratios. Examples of suitable lactones for the production of the polyesterols are α,α-dimethyl-β-propiolactone, γ-butyrolactone and preferably ε-caprolactone. The polyesterols preferably have a functionality of from 2 to 4, especially from 2 to 3, and a molecular weight of from 1,200 to 3,000, preferably from 1,500 to 3,000, and especially from 1,500 to 2,500.

In accordance with the invention, polyol mixtures have proven to be particularly suitable for the prepolymer. Such polyol mixtures preferably comprise at least one diol, preferably polypropylene glycol, and at least one triol, preferably polyethertriol. Particularly suitable diols have an average molecular weight in the range from 500 to 3,000, preferably from 700 to 1,500, particularly preferred from 800 to 1,500, with from 800 to 1,200 being particularly preferred. Triols which have been found to be suitable are those having an average molecular weight of from 1,000 to 8,000, preferably from 2,000 to 6,000, and particularly preferred from 3,000 to 5,000. It is particularly preferred for polyol mixtures! to have an OH number in the range from 30 to 140, preferably from 50 to 90, and particularly preferably from 60 to 80 mg KOH/g. The above-mentioned diols and triols can be used for the production of the prepolymer not only in the form of a polyol mixture, but also in each case used alone.

In another embodiment of the prepolymer according to the invention, the use of a polyether polyol which preferably has primary hydroxyl groups, with an OH number in the range from 10 to 60, preferably from 20 to 40, and particularly preferred from 25 to 35 mg KOH/g , proved to be suitable.

If chain extenders, cross-linking agents or mixtures thereof are used to prepare the prepolymers, it is sensible to use these in an amount of from 0 to 20% by weight, preferably from 0.5 to 5% by weight, based on the weight of all the isocyanate-reactive compounds used .

Suitable isocyanates or polyisocyanates of component B are the conventional aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates, preferably diisocyanates, which may, if desired, be biuretized and/or isocyanurated in accordance with generally known methods. Specific examples that can be mentioned are the following: alkylene diisocyanates with 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecanediisocyanate, 2-ethyltetramethylene-1,4-diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, tetramethylene- 1,4-diisocyanate, lysine ester diisocyanate (LDI), hexamethylene-1,6-diisocyanate (HDI), cyclohexane-1,3- and/or

-1,4-diisocyanate, 2,4- and 2,6-hexahydrotoluene diisocyanate, and the corresponding isomeric mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomeric mixtures, 1-isocyanate- 3,3,5-trimethyl-5-isocyanate-methylcyclohexane (IPDI), 2,4- and/or 2,6-tolylene diisocyanate, 4,4'-, 2,4'- and/or

2,2'-diphenylmethane diisocyanate (monomer MDI), polyphenylpolymethylene polyisocyanate (polymer MDI) and/or mixtures comprising at least two of the above-mentioned isocyanates. In the method according to the invention, it is also possible to use di- and/or polyisocyanates containing ester, urea, allophanate, carbodiimide, uretdione and/or urethane groups.

Particularly preferred according to the invention for the production of the prepolymer in the adhesive mixture according to the invention 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 an embodiment according to the invention, a polymeric MDI has an average functionality in the range from 1 to 5, preferably from 1.5 to 4 and particularly preferred from 2 to 3.5 and a viscosity in the range from 100 to 400, preferably from 150 to 300 and particularly preferably from 160 to 260 m-Pas, proved to be particularly suitable for the prepolymer.

As a catalyst, it is possible to use compounds which are generally known and which greatly accelerate the reaction of isocyanates with the isocyanate-reactive compounds, the total catalyst content used being preferably from 0.01 to 8% by weight, especially from 0.1 to 5% by weight, based on the weight of all the isocyanate-reactive compounds used. Examples which can be used include the following compounds: triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis(dimethylaminopropyl)urea, N-methyl- and N-ethylmorpholine, N ,N'-dimorpholindiethyl ether (DMDEE), N-cyclohexylmorpholine, N,NIN',N,-tetramethylethylenediamine, N)N,N',N'-tetramethylbutanediamine, N)N,N',N'-tetramethyl-1,6 -hexanediamine, penta-methyldiethylenetriamine, 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-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-tris(dialkylaminoalkyl )hexahydrotriazines, e.g. N,N',N"-tris(dimethylaminopropyl)-s-hexahydrotriazine, ferric chloride, zinc chloride, lead octoate and preferably tin salts, such as tin dioctoate, tin diethylhexoate, dibutyl tin dilaurate and/or dibutyldilauryltinmercaptide, 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 methoxide and potassium isopropoxide, and/or alkali salts of long-chain fatty acids with 10 to 20 carbon atoms and, if desired, protruding OH groups. Mention should also be made of trimerization catalysts such as alkali metal acetate or alkaline earth metal acetate, preferably potassium acetate. The above catalysts can also be used as an activator in addition to the morpholine derivatives that are used as activators. Accordingly, catalysts are incorporated into the polymer as such during its manufacture and activators are incorporated with the prepolymer in the adhesive composition as an additional component thereof. Further compounds which have proved suitable as catalysts and/or activators are Ti compounds, especially Ti(IV)-0-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.

If desired, further auxiliaries and/or additives can be added to the reaction mixture for the production of the prepolymers. Mention may be made, for example, of surface-active substances, stabilizers, cell-regulating agents, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors and substances with a fungistatic and a bacteriostatic effect. The surfactants and stabilizers counteract "peeling" ("skinning") of the air-facing surface of the adhesive composition. Furthermore, the surfactants, as well as the stabilizers, enhance the flow of the adhesive mixture, its shrinking capacity and its evaporation. Examples of suitable surface-active substances are compounds which promote the homogenization of the starting materials. Examples that can be mentioned include emulsifiers, such as the sodium salts of castor oil sulphates or of fatty acids, as well as salts of fatty acids of amines, e.g. diethyl amino oleate, diethanolamine stearate and diethanolamine ricinoleate, salts of sulphonic acids, for example alkali metal salts or ammonium salts of dodecylbenzene or dinaphthylmethanesulphonic acid and castor oleic acid; stabilizers, such as siloxane-oxalkylene copolymers and other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, liquid paraffins, castor oil esters or castor oil acid esters, Turkey red oil and peanut oil, as well as cell regulating agents, such as paraffins, fatty alcohols and dimethylpolysiloxanes. Further suitable for improving the emulsifying effect of, the cell structure of and/or the stabilization of the prepolymer are the above-described oligomeric acrylates with polyoxyalkylene and fluoroalkane radicals as side groups. If foaming is to be reduced or avoided, trialkyl phosphates are preferred antifoam agents. These preferably have alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl and 3-pentyl, preferably ethyl, n-propyl, isopropyl, n-butyl , isobutyl, and tert-butyl. Tributyl phosphate, available under the trade name Entschåumer T from Bayer AG, is particularly preferred for the above purpose. The surface-active substances are usually used in amounts of from 0.01 to 5% by weight, based on 100% by weight of the total isocyanate-reactive compounds used.

Fillers, especially reinforcing fillers, which may be present in the prepolymer independently of those in the adhesive mixture in question, are conventional, common organic and inorganic fillers, reinforcing agents, weighting agents, agents for improving the abrasion performance, coating materials, etc. The examples given below apply to both the prepolymer and the adhesive mixture according to the invention. Individual examples that can be mentioned are as follows: inorganic fillers and filler elements, such as silicate minerals, such as e.g. phyllosilicates such as antigorite, serpentine, hornblende, amphiboles, chrysotile and talc, metal oxides such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts such as chalk, tungspar, and inorganic pigments such as cadmium sulphide and zinc sulphide, as well glass etc. It is preferred to use kaolin (china clay), aluminum silicate, montmorillonite and coprecipitates of barium sulphate and aluminum silicate, as well as natural and synthetic fiber materials such as wollastonite, metal fibers and especially glass fibers of different lengths, which may have been glued. Examples of suitable organic fillers are charcoal, melamine, rosin, cyclopentadienyl resins, and grafted polymers. The organic and inorganic fillers can be used individually or as mixtures, and are preferably incorporated into the reaction mixture in amounts of from 0.5 to 50% by weight, preferably from 1 to 40% by weight, based on the weight of the isocyanates and on the weight of the combined the isocyanate-reactive compounds used.

The above fillers can alternatively be incorporated into the adhesive mixture according to the invention as they are, with the prepolymer, or already as a component of the prepolymer, or both with and as a component of the prepolymer.

Examples of suitable flame retardants are tricresyl phosphate, tris(2-chloroethyl)-phosphate, tris(2-chloropropyl)-phosphate, tris(1,3-dichloropropyl)-phosphate, tris(2,3-dibromopropyl)-phosphate, tetrakis(2-chloroethyl)ethylenediphosphate, dimethylmethanephosphonate, diethyldiethanolaminomethylphosphonate, as well as common commercial halogenated flame retardant polyols. In addition to the halogen-substituted phosphates already mentioned, it is also possible to use organic or inorganic flame retardants, such as red phosphorus, hydrated aluminum oxide, antimony trioxide, arsenic oxide, ammonium polyphosphate, and calcium sulfate, expanded graphite or cyanuric acid derivatives, such as e.g. melamine, or mixtures of at least two flame retardants, such as e.g. ammonium polyphosphates and melamine, as well as, if desired, corn starch or ammonium polyphosphate, melamine and expanded graphite and/or, if desired, aromatic polyesters, to increase the flame resistance of the prepolymer or of the adhesive mixture. In general, it has proven sensible to use from 5 to 50% by weight, preferably from 5 to 25% by weight, of said flame retardants, based on the weight of the total isocyanate-reactive compounds used.

An adhesive mixture according to the invention or a composite according to the invention can be used in building construction, engineering, for marine constructions, in the construction of aircraft or in the manufacture of motor vehicles, preferably in building construction or engineering.

Furthermore, the invention relates to building construction structures, engineering and marine constructions, motor vehicle or aircraft structures which comprise an adhesive mixture or a composite or both.

The invention will now be illustrated with reference to examples:

Examples

The adhesive mixtures in accordance with the tables below were obtained using the prepolymers synthesized in the manufacturing processes described below.

Prepolymer A

59.4 parts of monomeric MDI, a mixture of 50-54 parts of 2,4'- and 46-50 parts of 4,4'-diphenylmethane diisocyanate (MDI) was introduced under a dry atmosphere into a container that could be heated/cooled, and which was equipped with a stirrer. At a product temperature of 80°C, 40.6 parts of a polyol mixture comprising a polypropylene glycol with an average molecular weight of 1,000 and a polyethertriol with an average molecular weight of 4,000 was slowly added with stirring. The polyol mixture has an OH number of 73 mg KOH/g. After the addition was finished and after a subsequent stirring phase of 1 hour, the prepolymer was cooled to room temperature and taken out.

The prepolymer has an NCO content of 17.5% and a viscosity of 750 m-Pas.

Prepolymer B

53.0 parts of monomeric MDI, a mixture of 50-54 parts of 2,4'- and 46-50 parts of 4,4'-diphenylmethane diisocyanate (MDI) was introduced under a dry atmosphere into a container that could be heated/cooled, and which was equipped with a stirrer. At a product temperature of 80°C, 47.0 parts of a polyol mixture comprising a polypropylene glycol with an average molecular weight of 1,000 and an amine-based polyethertriol with an average molecular weight of 4,000 was slowly added with stirring. The polyol mixture has an OH number of 73 mg KOH/g. After the addition was finished and after a subsequent stirring phase of 1 hour, the prepolymer was cooled to room temperature and taken out.

The prepolymer has an NCO content of 14.9% and a viscosity of 1,200 m-Pas.

DMDEE 2)2'-dimorpholindiethyl ether

Claims (14)

1. Adhesive mixture, characterized in that it includes at least up to 99.9% by weight of the adhesive mixture of a prepolymer obtainable from at least one component A comprising an isocyanate-reactive compound and at least one component B comprising an isocyanate, from 0.1 to 20% by weight of at least one fibrous filler which comprises at least one fiber and in addition to the fiber contains at least one non-fibrous filler element, from 0 to 20% by weight of common additives and auxiliaries, from 0 to 10% by weight of an activator, wherein at least one fiber has a diameter in the range from 5 to 100 µm and a length in the range from 0.02 to 6 mm. 2. Adhesive mixture according to 1, characterized in that it comprises at least one of the features (i) to (iii): (i) the prepolymer has at least one of the subsidiary features (a) and (b): (a) an NCO content of from 5 to 30% by weight , based on the prepolymer, (b) a viscosity at 25°C in the range of 300 to 150,000 m-Pas; (ii) component A has at least one of the subsidiary features (c) and (d): (c) component A comprises at least one diol or polyol, (d) the OH number of component A is in the range from 10 to 500 mg KOH /g; (iii) the filler has the following subsidiary feature (e): (e) the fiber comprises at least one fiber polymer. 3. Adhesive component according to claim 2, characterized in that it comprises at least one of the following features (iv) and (v): (iv) the fiber polymer is at least one polyamide, (v) the filler element comprises at least one inorganic material. 4. Adhesive mixture according to claim 3, characterized in that said inorganic material is an oxygen compound of silicon, aluminum or magnesium or of at least two thereof. 5. Adhesive mixture according to any one of claims 1 to 4, characterized in that said activator comprises at least one morpholine derivative. 6. Adhesive mixture according to any one of claims 1 to 5, characterized in that it has a low solvent content. 7. Method for producing an adhesive mixture according to any one of claims 1 to 6, characterized in that the components defined in claim 1 are brought into contact with each other. 8. Adhesive mixture, characterized in that it can be obtained by bringing the components defined in claim 1 into contact with each other. 9. Adhesive mixture according to any one of claims 1 to 6 or 8, characterized in that it comprises at least one of the following material properties (g) to (m): (g) initial drying time under standard conditions 20/65-1 in accordance with DIN 50014 at an application rate of 250 g/m2 in the range from 20 to 40 minutes, (h) initial drying time under standard conditions 20/65-1 in accordance with DIN 50014 at an application rate of 400 g/m2 in the range from 20 to 40 minutes, ( i) viscosity at 25°C in the range from 300 to 150,000 m-Pas, (k) storage stability of from 1 to 4 months, (I) NCO content in the range from 3 to 20% by weight, based on the adhesive composition, (m ) minimum pressing time in accordance with DIN 68141 in the range from 5 to 8 hours. 10. Composite, characterized in that it at least comprises a substrate and an adhesive mixture according to any of claims 1 to 6, 8 and 9. 11. Composite according to claim 10, characterized in that it comprises at least one of the following material properties: (n) a delamination resistance in accordance with DIN EN 302 part 2 of no more than 5% in accordance with DIN EN 301, (o) a dry shear strength in the range of at least 6 N/ mm<2> up to a maximum of substrate fracture in accordance with the quality guidelines of the RAL-Gutegemeinschaft Holzleimbau. 12. Composite according to claim 10 or 11, characterized in that the substrate comprises wood and glued layer(s) or glued finger joint(s), or both. 13. Use of an adhesive mixture according to any one of claims 1 to 6, 8 and 9 or of a composite according to claims 10 to 12 in building construction, engineering, for marine constructions, in the construction of motor vehicles or aircraft, preferably in glued laminated three. 14. Building construction, engineering or marine structure, motor vehicle or aircraft structure, preferably in glued laminated wood, characterized in that it comprises an adhesive mixture according to any of claims 1 to 6, 8 and 9 or a composite according to any of claims 10 to 12.