NO326177B1 - Adhesive composition for gluing finger pads - Google Patents

Abstract

No filler is present in an adhesive composition (I) containing: (a) up to 99.999 wt.% prepolymer derived from (A) compound(s) which react with isocyanate; and (B) isocyanate(s); (b) 0-20 wt.% conventional additives and auxiliary substances; and (c) 0.001-10 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).

Description

The invention relates to an adhesive mixture with a low solvent content, a method for producing the same, a composite comprising it and the use of the adhesive mixture or of the composite in building construction, engineering, marine constructions, construction of aircraft or cars.

Wood, for example, is a recognized and established material in structural architecture. In order to carry out larger spans than is permitted with the help of beams that are cut to size individually, glued laminated wood is used. Glued laminated wood is produced industrially by gluing together individual plank layers, preferably over their entire area. By means of glued joints of layers of short wooden layers in the longitudinal direction, known as finger jointing, it is possible to produce individual layers of practically infinite length, which are cross-cut to the required size. Gluing provides, in the same way as larger dimensions, a reinforcement of the wood, as a natural substance, as naturally occurring irregularities such as twigs are cut out and the shrinkage and swelling of the wood as a result of climate change is significantly reduced.

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

The adhesive systems mainly used at present are amino resins and phenolic resins which cure in a polycondensation reaction to give the final glued joint. The chemical curing reaction for these systems, which is mainly in the form of two components, is initiated by mixing adhesive and hardener 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 the addition of formaldehyde or paraformaldehyde. Even in the finished glue joint, there is still free formaldehyde in small quantities, which can be released into the surrounding air during an extended period of time. There is currently a suspicion that formaldehyde causes health damage.

DE 44 12 759 A1 describes a formaldehyde-free, filler-containing adhesive mixture based on an isocyanate-containing polyurethane prepolymer. This adhesive mixture in particular has a viscosity which is quite unsuitable for processing, and press times which are unsuitable for practical implementation. The viscosity is of great importance, especially for the pumpability and the ability of the adhesive mixture to penetrate into the substrate to be bonded (adhesion).

Adhesive mixtures containing filler are particularly disadvantageous in connection with the machine bonding of surfaces that have narrow and deep incisions. A surface of this type is encountered, for example, in finger joint gluing according to DIN 68140, part 1. Here, the finger joints are generally shaped in terms of their cross-section as pointed triangles, so that triangular, pointed incisions are also formed from in each case one projection of two adjacent fingers. An adhesive mixture is generally applied to the protruding areas of the fingers using a tool that combs through the incisions, and where the adhesive-applied area conforms to the incisions through its shape. In general, the adhesive mixture is dispersed from the flanks of this application comb, which is generally approximately the same length as the projecting portions, by means of slits provided in this area.

When a filler-containing adhesive mixture is distributed, blocking of these gaps occurs very often, as well as the formation of deposits originating from the filler-containing adhesive mixture. First and foremost, these blockages and deposits necessitate frequent cleaning, and thus downtime, of the current installation. Furthermore, the blockages in particular result in one or more fingers of a workpiece to be glued not being applied with adhesive mixture. This can lead to significant differences in the strength of the finger joint glue, which reduces the product's quality to a significant extent.

It is an object of the present invention to provide an adhesive mixture in which the disadvantages associated with the blocking and formation of the deposit are absent. Furthermore, an adhesive mixture of this type should not have formaldehyde emissions. This adhesive mixture must also demonstrate that it is easily pumpable, workable and that it is storage stable. A further purpose is also that the adhesive mixture provided according to the invention should satisfy the requirements that exist above all in building construction and engineering, imposed in particular by national test institutes, to at least the same extent as the adhesive mixtures used until today satisfy these requirements, especially the adhesive mixtures based on phenol/resorcinol resins and melamine/urea resins or on an isocyanate-containing polyurethane prepolymer as well as fillers, for comparable applications.

We have found that the above purpose is achieved by means of the present invention which comprises an adhesive mixture with a low solvent content, where at least up to 99.999% by weight of the adhesive mixture of a prepolymer can be obtained from at least one component A comprising an isocyanate reactive compound and at least one component B comprising a isocyanate,

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

from 0.001 to 10% by weight of at least one morpholine derivative as an activator,

where

(a) the prepolymer has at least one of the secondary features

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

(ii) a viscosity at 25°C in the range of 300 to 15,000 m-Pas;

(b) component A has one of the subordinate features

(i) component A comprises at least one diol,

(ii) The OH number of component A is in the range of 10 to 500 mg KOH/g in which the adhesive composition contains no filler, and the viscosity of the adhesive composition (at 25°C) is in the range of 300-15000 m-Pas.

According to the invention, it is preferred that the adhesive mixture comprises in the range from 70 to 99.99, preferably from 80 to 99.99, and particularly preferred from 85 to 99.99% by weight of the prepolymer and from 0.01 to 5, preferably from 0.01 to 3, and particularly preferably from 0.01 to 1% by weight of the activator and, if desired, as the remainder, up to a total amount of 100% by weight of additional additives and auxiliaries, based in each case on the adhesive mixture.

Furthermore, in the adhesive mixture according to the invention, at least one of the following main features is preferred:

(a) the prepolymer has at least one of the following secondary features:

(i) an NCO content of from 5 to 30, preferably from 10 to 20, and particularly preferably from 13 to 17% by weight, based on the prepolymer, (ii) a viscosity at 25°C in the range from 300 to 15,000 mPas ;

(b) component A has at least one of the following subordinate features:

(i) component A comprises at least one diol or polyol, preferably a diol or triol, and particularly preferably a diol and triol, (ii) the OH number for component A is in the range from 10 to 500, preferably from 20 to 300, and particularly preferably from 30 to 200 mg KOH/g.

Furthermore, an adhesive mixture is described where the defined components are brought into contact with each other.

The adhesive mixture according to the invention comprises at least one of the material properties (B) to (E).

(B) rheological setting time in the range of 10 to 150 minutes,

(C) storage stability of from 1 to 4 months,

(D) NCO content in the range from 3 to 30% by weight, based on the adhesive mixture, (E) minimum pressing time according to DIN 68141 in the range from 15 to 150 minutes.

Furthermore, the invention includes a composite where this is characterized by

a substrate and an adhesive mixture.

Application of an adhesive mixture or of a composite as described above in building constructions, engineering, marine constructions, automobile or aviation constructions, preferably in glued finger joints, is also discussed.

The viscosity of the prepolymer at 25°C is preferably in a range from 300 and 15,000, preferably 500 and 10,000, m-Pas, in order for the adhesive mixture to be pumpable.

Furthermore, according to the invention, it is preferred that the adhesive mixture has a low solvent content. This applies when the amount of solvent content present in the adhesive mixture is <10, preferably <5, and particularly preferably <2% by weight. Solvents according to the invention are organic and inorganic liquids which are suitable as carriers for the other components in the adhesive mixture, which do not harden with at least part of the other components, but can be removed from the hardened adhesive.

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

In one embodiment of the adhesive mixture according to the invention, both the above-mentioned main feature (a) of the prepolymer and main feature (b) of component A are realized.

In another preferred embodiment of the adhesive mixture according to the invention, not only all the main features, but also all subordinate features are carried out.

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'-dimorpholinodiethylether and dimorpholinopolyethyleneglycol, 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 quantitative proportions of the morpholine derivatives being preferably dominant.

Furthermore, it is also possible to add thixotropic aids to the adhesive mixture. In that case, it is preferred that the thixotropic auxiliaries are not present as solids that would be suitable as filler elements. Particularly preferred are therefore soluble thixotropic auxiliaries which can be obtained, for example, by the 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.

In a further preferred embodiment of the adhesive mixture according to the invention, it is not only the adhesive mixture that has no filler component, but the prepolymer used in the adhesive mixture is also free of fillers.

In another preferred embodiment of the adhesive mixture according to the invention, thixotropic aids are used, it being particularly preferred that no fillers are used in addition to the thixotropic aids.

Thixotropic aids include very finely divided substances that thicken

liquids even when added thereto 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 in which they are dispersed to form hydrogen bonds and thus lead 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 dispersion is carried out in a thorough manner by intimate mixing. Furthermore, the thixotropic aids have the advantage that they do not settle in the dispersed liquid. Preferred materials for thixotropic aids, in the form of fine powder, are montmorillonite, Mg/AI silicate, AI/Na silicate, bentonites, hectorite, Na/Mg silicate, fumed silica types, hydrated silica types, hornblende chrysotile, chrysotile asbestos, chrysotile silica and precipitated MgO, with fumed silica types being particularly preferred, available for example as Aerosil from Degussa-Huls AG, and Mg silicates, available as

benton from Kronos Titan GmbH Leverkusen, Aerosil being very particularly preferred.

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

The prepolymer according to the invention is preferably provided by introducing component B and adding component A 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 so thoroughly by means of the mixing device 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:

(A) viscosity at 25°C in the range from 300 to 15,000 m-Pas,

(B) rheological setting time in the range from 10 to 150, preferably from 30 to 100, and particularly preferred from 45 to 70 minutes, (C) storage stability of from 1 to 4, preferably from 2 to 6, and particularly preferred from 3 to 8 months, (D) NCO content in the range from 3 to 30, preferably from 5 to 20, and particularly preferred from 6 to 18% by weight, based on the adhesive mixture, (E) minimum pressing time according to DIN 68141 in the range from 15 to 150, preferably from 15 to 100, and particularly preferred from 15 to 75 minutes.

The viscosity of the adhesive mixture at 25°C is preferably within a range from 300 to 15,000, more preferably from 500 to 10,000 m-Pas for adhesive mixtures that can be pumped.

The storage stability of the adhesive mixture is determined by means of the viscosity of the adhesive mixture. Storage stability is present if the viscosity of the adhesive mixture at 25°C in an accelerated aging test after storage for a defined period of time in the absence of air and moisture has not increased by more than 20% compared to the level before storage.

According to the invention, workability is provided if, over an operating period of 8 hours, there is no deposit of adhesive mixture residues on the comb-like application device for finger-joint gluing.

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

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

Of the above-mentioned material properties, one embodiment of the adhesive mixture according to the invention has at least the viscosity (A), the storage stability (C), the NCO content (D) and the minimal pressing time (E).

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

The invention additionally 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 materials that are known to the person skilled in the art. As naturally occurring materials, wood types from different trees can be mentioned in particular, for example hard wood types and soft wood types. Examples of synthetic cellulose materials are paper types, board types, laminates, cartons and the like. Suitable substrates similarly include materials that can be bonded with the adhesive mixture according to the invention in a similar way to the cellulose materials.

One preferred composite comprises continuous wooden boards comprising at least two individual boards joined to each other at their end pieces by means of a finger joint, the fingers being connected by means of the adhesive mixture according to the invention.

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

The adhesive mixture according to the invention is particularly suitable for the production of wooden boards comprising glued finger joints.

Furthermore, it is preferred that composites) according to the invention, especially if it comprises finger-jointed wood panels, have the following material properties: (F) a bending strength according to the procedural guidelines of the Gutegemeinschaft BS-Holz [Glulam Quality Association] RAL RG 421 in the range from 20 to 70

N/mm<2>.

The bending strength of the finger joint bending test for layers of the following types of classes is particularly preferred:

for layers of type class S10, MS 10 > 30 N/mm<2>

for layers of type class S13, > 35 N/mm<2>

for layers of type class MS13, 40 N/mm<2>

for layers of type class MS17, 45 N/mm<2>

The bending strength of the type of wood that is usually used for the production of glued laminated wood, namely spruce, is in the range from 65 to 70 N/mm<2>.

In addition to their use as load-bearing components for roofing, bridge building and sealing structures, the composites according to the invention are also suitable for use in the manufacture of concrete formwork, especially as concrete formwork carriers, and in scaffolding, especially as scaffolding platforms.

It is further preferred that the composite according to the invention, preferably with surface bonding, has at least one of, preferably all, the following material properties: (G) a delamination resistance according to DIN EN 302, part 2 of no more than 5% according to DIN EN 301, preferably not more than 2%, and particularly preferably not more than 1%, (H) a dry shear strength in the range from at least 6 N/mm<2> up to substrate fracture according to the quality guidelines of the RAL Gutegemeinschaft Holzleimbau

[Glued Wood Construction Quality Association].

The substrate fracture values and shear strength values for different types of wood can be found in Holzlexikon [Wood Dictionary] from BRW-Verlag, 3rd ed. 1998. The substrate fracture for the type of wood usually used, namely spruce, is approx. 7.5 N/mm<2>.

In the production of 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 the viscosity, are achieved. In addition, auxiliaries and additives or catalysts can be used to produce the prepolymer.

The additional starting materials and components for the production of the prepolymer mixture and the adhesive mixture are described by way of example in the following: As isocyanate-reactive compounds, namely component A, 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 the polyetherols and polyesterols, polythioether polyols, hydroxyl-containing polyacetals and hydroxyl-containing aliphatic polycarbonates, polycarbonate diols and polycaprolactone diols, or mixtures of at least two of the said 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. the hardness, and to increase the stability of the prepolymer, however, the addition of chain extenders, cross-linking agents or, if desired, mixtures thereof, may prove beneficial. The chain extenders and/or crosslinkers 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 low molecular weight polyalkylene oxides based on ethylene oxide and/or 1,2-propylene oxide and the above-mentioned diols and/or triols as starting molecules .

As polyol components, it is also generally possible to use polyols with high functionality, in particular polyetherols based on alcohols with high functionality, sugar alcohols and/or saccharides as starting molecules. 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 according to a known technology. 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, alternating in order, or as mixtures. In the prepolymer in the adhesive mixture according to the invention, those polyetherols are particularly preferred which, at the end of the carboxylation, 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 as ethanolamine and triethanolamine.

The polyetherols have a functionality of preferably from 2 to 6 and especially from 2 to 3, and a molecular weight 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 be prepared, for example, 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, or 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. 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol and 2,2-dimethyl-1,3-propanediol are preferably used; 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 preparation 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.

According to 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, with particular preference from 800 to 1,500, and with very particular preference from 800 to 1,200. Triols which have been found to be suitable are those with 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 that the polyol mixture has 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 not only in the form of a polyol mixture, but also in each case alone to prepare the prepolymer.

In another embodiment of the prepolymer according to the invention, the use of a polyether polyol with preferably primary hydroxyl groups, with an OH number in the range from 10 to 60, preferably from 20 to 40, and particularly preferably 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, they are judiciously used 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, if desired, have been biuretized and/or isocyanuratized according to commonly known processes. 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-methylpenta-methylene-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-hexahydrotoluenediisocyanate, and the corresponding isomeric mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomeric mixtures, 1-isocyanato-3,3,5-trimethyl-5-isocyanato-methylcyclohexane (IPDI) , 2,4- and/or 2,6-tolylene diisocyanate, 4,4'-, 2,4'- and/or 2,2'-diphenylmethane diisocyanate (monomeric MDI), polyphenylpolymethylene polyisocyanate (polymeric MDI) and/or mixtures comprising at least two of the above-mentioned isocyanates. It is also possible to use di- and/or polyisocyanate-containing ester, urea, allophanate, carbodiimide, uretdione and/or urethane groups in method 1 according to the invention.

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 commonly known compounds, 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 of such that 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'-dimorpholinodiethyl ether (DMDEE), N-cyclohexylmorpholine, N.N.W.W-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, f .eg N,N\NMris(dimethylaminopropyl)-s-hexahydrotriazine, ferric chloride, zinc chloride, lead octoate and preferably tin salts, such as tin dioctoate, tin diethylhexoate, dibutyl tin dil aurate and/or dibutyldilauryl tinmercaptide, 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 may also be made of trimerization catalysts such as alkali metal acetate or alkaline earth metal acetate, preferably potassium acetate. The above-mentioned catalysts can also be used in addition as an activator for the morpholine derivatives used as activators. Catalysts are therefore incorporated into the polymer as such during its manufacture, and activators are incorporated with the prepolymer in the adhesive mixture as an additional component thereof. Further compounds which have been found to be suitable as catalysts and/or activators are Ti compounds, especially 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 preferred, Ti(IV)-butoxide.

If desired, further auxiliaries and/or additives can be added to the reaction mixture for the production of the prepolymers. For example, surface-active substances, stabilizers, cell-regulating agents, dyes, pigments, flame retardants, hydrolysis inhibitors and substances with a fungistatic and a bacteriostatic effect can be mentioned. The surface-active substances and stabilizers counteract the formation of a surface layer ("skinning") on the surface of the adhesive mixture that faces air. Furthermore, the surfactants, as well as the stabilizers, enhance the flow of the adhesive mixture, its creep capacity, and its evaporation. Examples of suitable surfactants are compounds that serve to support 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 ricinoleic 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, and cell regulators, such as paraffins, fatty alcohols and dimethylpolysiloxanes. Suitable for improving the emulsifying effect, the cell structure and/or the stabilization of the prepolymer are the oligomeric acrylates described above with polyoxyalkylene and fluoroalkane radicals as side groups. If foaming is to be reduced or avoided, then 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. 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.

Examples of suitable flame retardants are tricresyl phosphate, tris(2-chloroethyl)-phosphate, tris(2-chloropropyl)-phosphate, tris(1,3-dichloropropyl)-phosphate, tris(2,3-dibromo-propyl)-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 alumina, antimony trioxide, arsenic oxide, ammonium polyphosphate, and calcium sulfate, expanded graphite or cyanuric acid derivatives, such as, for example, melamine , or mixtures of at least two flame retardants, such as for example 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 been found to be appropriate 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, marine construction, car construction or aircraft construction, preferably in building construction or engineering. Furthermore, the adhesive mixture according to the invention can be used for gluing finger joints. Finger joints of this type preferably exhibit a distance between the flank areas of the plates that are finger-jointed to each other, which is in the range from 0.05 to 0.2 mm, preferably from 0.09 to 0.13 mm.

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

The invention will now be illustrated by reference to non-limiting examples.

Examples

The adhesive compositions according to the following table 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 placed under a dry atmosphere in 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 placed under a dry atmosphere in 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 15.0% and a viscosity of 1200 m-Pas.

Preparation of the adhesive mixtures

The preparation of comparative adhesive compositions, as described in Table 1 (Examples 1 and 2), took place according to the following method: A vessel equipped with anchor stirrer and solvent was charged under a dry atmosphere with the appropriate amount of the prepolymer. Then the activator and, if appropriate, the additives and auxiliaries were added one after the other and the mixture was homogenized with the solvent at as high speeds as possible.

The production of the adhesive mixture according to the invention, as described in examples 3, 4 and 5 in table 1, took place according to the following method:

The appropriate amount of activator was either added after the preparation of the prepolymer, as described by way of example above, after the subsequent stirring phase but before cooling, or in a step after the preparation of the prepolymer; the appropriate amount of the prepolymer was placed under a dry atmosphere in a container equipped with a stirrer, and at room temperature the appropriate amount of the activator was added, and then the mixture was homogenized with the stirrer.

Storage stability:

The storage stability is determined by the viscosity of the adhesive mixture. Storage stability is therefore present according to the invention if the viscosity of the adhesive mixture in an accelerated aging test after storage for 4 weeks at 60°C in the absence of air and moisture has not risen by more than 20% compared to the original level.

Machinability:

Processability is present if, after a production period of 8 hours, there are no visible deposits on the application comb.

Rheological curing time:

The curing behavior was measured using the Haake RS 100 viscometer at 20°C in oscillation mode. The "curing time" is the time after which a complex viscosity of 5<*>10<6> m-Pas is achieved.

Claims (8)

1. Adhesive mixture with low solvent content, characterized in that it includes at least up to 99.999% by weight of the adhesive mixture of a prepolymer which can is obtained from at least one component A comprising an isocyanate-reactive compound and at least one component B comprising an isocyanate, from 0 to 20% by weight of common additives and aids, from 0.001 to 10% by weight of at least one morpholine derivative as an activator, wherein (a) the prepolymer has at least one of the subordinate features (i) an NCO content of from 5 to 30% by weight, based on the prepolymer, (ii) a viscosity at 25°C in the range from 300 to 15,000 m-Pas ; (b) component A has one of the subordinate features (i) component A comprises at least one diol, (ii) the OH number of component A is in the range from 10 to 500 mg KOH/g in which the adhesive composition contains no filler, and the viscosity to the adhesive mixture (at 25°C) is in the range from 300-15000 m-Pas. 2. Method for producing an adhesive mixture according to claim 1, characterized in that the components defined in claim 1 are brought into contact with each other. 3. Adhesive mixture, characterized in that it can be obtained by bringing the components defined in claim 1 into contact with each other. 4. Adhesive mixture according to any one of claims 1 and 3, characterized in that it comprises at least one of the material properties (B) to (E) (B) rheological curing time in the range from 10 to 150 minutes, (C) storage stability of from 1 to 4 months, (D) NCO content in the range from 3 to 30% by weight, based on the adhesive mixture, (E) minimum pressing time according to DIN 68141 in the range from 15 to 150 minutes. 5. Composite, characterized in that it at least comprises a substrate and an adhesive mixture according to any of claims 1, 3 and 4. 6. Composite according to claim 5, characterized in that it comprises at least one of the material properties (F) a bending strength according to the procedural guidelines of the Gutegemeinschaft BS-Holz [Glulam Quality Association] RAL RG 421 in the range from 20 to 70 N/mm<2>, (G) a delamination resistance according to DIN EN 302, part 2, of no more than 5% according to DIN EN 301, (H) a dry shear strength in the range from at least 6 N/mm<2> up to substrate fracture according to quality the guidelines from the RAL-Gutegemeinschaft Holzleimbau. 7. Composite according to claim 5 or 6, characterized in that a substrate comprising at least wood material comprises glued layer(s) or glued finger joint(s), or both. 8. Use of an adhesive mixture according to any of claims 1, 3 and 4 or of a composite according to any of claims 5 to 7 in building construction, engineering, marine constructions, car or aircraft construction, preferably in glued finger joints.