EP1088042A1 - Adhesive which hardens in several stages - Google Patents

Abstract

The invention relates to a hot-melt adhesive with a melting point of at least 40 °C, containing either a polymer with at least one functional group that is reactive towards a compound with an acidic hydrogen atom and with one functional group that can be polymerised by UV or electron beams or a polymer with at least one functional group that is reactive towards a compound with an acidic hydrogen atom and with no functional group that can be polymerised by UV or electron radiation; and a compound with a functional group that can be polymerised by UV or electron beams and a molecular weight (Mn) of less than 5,000.

Description

 Multi-stage curing adhesive

The invention relates to a hot melt adhesive with a melting point of at least 40 ° C, either containing a polymer which has at least one functional group reactive towards a compound having an acidic hydrogen atom and a functional group polymerizable by UV or electron beams, or a polymer which at least has a functional group reactive to a compound having an acidic hydrogen atom and has no functional group polymerizable by UV or electron beams and a compound having a functional group polymerizable by UV or electron beams and a molecular weight (M _n ) of less than 5,000.

The mechanical production of composite materials, in particular composite films, is often carried out in practice by lamination using solvent-based adhesives. However, such an approach is disadvantageous from various aspects.

If solvent-based adhesives are used for lamination, considerable amounts of solvent usually have to be evaporated during the lamination process with high energy consumption. Furthermore, in order to avoid the emission of solvent vapors into the atmosphere, it is necessary to purify the exhaust air which arises when the solvent evaporates. Furthermore, solvent-based adhesives have the disadvantage that they generally only achieve sufficient strength after they have passed a drying stage, that is to say after at least the majority of the solvent contained in the adhesive has evaporated. On the other hand, dispensing with solvents greatly affects the processability of an adhesive. Adhesives that are suitable for the production of composite materials should initially have a suitable processing viscosity, but should only release small amounts of volatile substances into the environment. Furthermore, there is a requirement for such adhesives that, as a rule, immediately after being applied to at least one of the materials to be joined, after they have been joined together, they have a sufficiently good initial adhesion which, as far as possible, prevents the bonded materials from shifting relative to one another. In addition, however, such an adhesive bond should also have a sufficient degree of flexibility in order to be able to deal with the various tensile and tensile loads to which the composite material which is still in the processing stage is generally subjected, without damage to the adhesive bond and without damage to the bonded material survive.

Particularly high demands are placed on the initial adhesion of the bonded materials if not only thin foils are laminated together, but materials that have increased tensile strength, but instead a much greater bending stiffness, for example sheet-shaped plastic materials with a thickness of more than about 100 μm or composite materials that contain, for example, a layer of cardboard and whose thickness is also usually more than 100 μm. In the case of such composites, an adhesive bond is exposed to particularly high loads, since even low bending forces are transmitted to the bond point almost undamped due to the high flexural strength of the composite. Due to their low initial adhesion, conventional adhesives are generally not able to withstand the high forces that occur at the bond point undamaged shortly after application.

In addition to excellent initial adhesion, various applications, particularly in the packaging of foodstuffs, require further qualities of the adhesive bond. After curing, the adhesive bond must have such a high strength that, for example, packaged food withstand the increased loads to which they are exposed, for example during transport, sales or by the user. Furthermore, such adhesive bonds must have excellent heat resistance, since foods are often filled into the packaging in a warm or even hot state, the temperature of which can be up to about 100.degree. If the adhesive connection of a food packaging then does not prove to be sufficiently heat-resistant, the adhesive connection can be damaged during the filling process or during the cooling phase of the food, which can cause the food to escape from the packaging, for example. However, even the smallest cracks in the adhesive connection can be unfavorable for the food intended for sale, through which microorganisms, for example, can penetrate the packaging and make the food unusable.

In the case of the conventional, solvent-free adhesives known from the prior art, there is generally a fundamental disadvantage in that the adhesive properties of the adhesive after application are unsatisfactory owing to the low viscosity and the adhesive bond must therefore not be subjected to any loads until it has finally hardened, so that the composite material retains the shape intended for the bond. Such adhesives are generally not suitable for the production of composite materials with increased bending stiffness. Furthermore, such adhesives generally require long curing times, which often makes the production of composite materials using such adhesives uneconomical.

One approach to avoid the disadvantages described above was to use a multi-stage curing adhesive system in the manufacture of composite materials. Here, adhesives were used which were subjected to a rapid, first curing reaction in a first stage by irradiation. The strength of the adhesive bond after this first hardening reaction should be such that it enables easy handling of the connected objects or materials. In a second curing stage, the adhesive then cures further until it has the desired final strength. DE-A 29 13676, for example, discloses a method for producing composite films by means of solvent-free adhesives. A solvent-free adhesive is described which is liquid at room temperature and which consists of oligomeric and / or polymeric esters and / or ethers which contain both free isocyanate groups and free (meth) acrylate groups in one molecule.

However, a disadvantage of such methods is that the strength of the bond is sufficient to bond thin, flexible materials with low bending stiffness, but the initial hardening is usually not sufficient to force-fit connections from thicker, stiffer materials in the initial phase .

EP-B 0 564483 relates to reactive contact adhesives, processes for their production and their use. The publication describes two-stage polymerizable coating compositions based on urethane, which can be cured by a content of UV-polymerizable acrylate groups in the course of a first curing stage to form a solidified, but still structurally deformable or embossable material, followed by irreversible bonding in a subsequent second stage. Monofunctional acrylates are added to the adhesive to lower the viscosity. The described adhesive exhibits pressure tack after the irradiation. The intended use for the contact adhesive described is the bonding of wood and / or plastic parts at up to about 70 ° C., preferably at room temperature.

It was the object of the present invention to provide an adhesive which is suitable for the production of composite materials, in particular for the production of composite materials with high flexural strength, which has a high initial adhesion immediately after the bonding has been carried out, and which has excellent properties after complete curing to give composite materials Strength values and good heat resistance leads.

The object of the invention is achieved by a hot melt adhesive with a Melting point of at least 40 ° C, as described below.

The invention relates to a hot melt adhesive with a melting point of at least 40 ° C., containing a component A or a component A and a component B or a component B and a component C or a component A and a component C or components A, B and C. , where a) as component A, a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group which is reactive towards a compound having an acidic hydrogen atom and a functional group which can be polymerized by UV or electron beams, b) as component B a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group reactive towards a compound having an acidic hydrogen atom and no functional group polymerizable by UV or electron beams and c) as component C a compound having a UV or electron beam polymerizable functional group and a molecular weight (M _n ) of less than about 5,000 is included.

The term “melting point” cannot generally be sharply defined in the case of compositions which can contain several components, some of which have different molecular weights. In the context of the present invention, the term “melting point” is therefore understood to mean the temperature at which a molded body consisting of the adhesive according to the invention loses its dimensional stability, that is to say that it (if appropriate depending on the amount used) is used in a period of about one Minute to about an hour, for example within about 5 minutes or about 15 minutes or about 30 minutes or about 45 minutes, at which the temperature referred to as the "melting point" completely loses its original external shape.

In a preferred embodiment, the composition according to the invention has form a melting point of at least about 60 ° C, for example at least about 70 ° C or at least about 80 ° C. In special cases, the melting point can also be higher, for example at least about 90 ° C. or at least about 100 ° C.

The adhesive according to the invention contains a combination of components A, B and C, as have already been explained individually above.

In the context of the present invention, the term “component A” is understood to mean a polymer with a molecular weight (M _n ) of at least about 5,000, which has at least one functional group which is reactive towards a compound having an acidic hydrogen atom and a functional group which can be polymerized by UV or electron beams Group has.

A compound having an acidic hydrogen atom is understood to mean a compound which has an active hydrogen atom which can be determined by the Zerewittinoff test and is bound to an N, O or S atom. These include in particular the hydrogen atoms of water, carboxy, hydroxyl, amino, imino and thiol groups. In the context of the present invention, water is particularly preferred as a compound having an acidic hydrogen atom. Also preferred are compounds which have amino or OH groups or both, or mixtures of two or more of the compounds mentioned.

NCO, epoxy, anhydride or carboxyl groups are particularly suitable as functional groups which are reactive towards a compound having an acidic hydrogen atom. NCO and epoxy groups or mixtures thereof are preferred in the context of the present invention. A polymer which can be used as component A in the context of the present invention can have, in addition to the other required features, for example only one functional group which is reactive toward a compound having an acidic hydrogen atom. However, it is also possible to use a compound as component A which has two or more such groups. If the corresponding polymer has two or more such functional groups, the functional groups can have one Be kind, that is, for example, only NCO groups or only epoxy groups, but the polymer can also have mixtures of different functional groups of the type mentioned, for example NCO groups and epoxy groups or NCO groups and epoxy groups and one or more further functional groups of the already mentioned type, for example one or more anhydride groups or one or more carboxyl groups.

In the context of the present invention, the functional group capable of reacting with a compound having at least one acidic hydrogen atom is in particular the isocyanate group or the epoxy group, the isocyanate group being particularly preferred.

At least one polymer with a molecular weight of at least about 5,000 is contained as component A in the composition according to the invention. Polymers suitable for use as component A are, for example, polyacrylates, polyesters, polyethers, polycarbonates, polyacetals, polyurethanes, polyolefins or rubber polymers such as nitrile or styrene / butadiene rubbers, provided that they have at least one functional group which can be polymerized by UV or electron beams and at least one for Reaction with a functional group capable of having at least one acidic hydrogen atom.

However, polyacrylates, polyesters or polyurethanes, in particular polyesters or polyurethanes, are preferably used as polymers in the composition according to the invention, since the polymers mentioned offer a particularly simple possibility of attaching the functional groups required according to the invention to the polymer molecule.

The polymers mentioned can be prepared particularly easily by starting from a compound referred to below as the “base polymer” or a mixture of two or more such compounds which have at least two functional groups which are reactive with isocyanate, epoxy, carboxyl or anhydride groups per molecule Groups, preferably NH or OH groups, in Have polymer molecule. The desired functional group can be attached in a particularly simple manner to such a base polymer by reaction with suitably functionalized isocyanates, epoxides, carboxylic acids or anhydrides. In the context of the present invention, a polymer with terminal OH groups is preferably used as the “base polymer”.

For example, a polymer selected from a group containing polyesters, polyethers, polycarbonates or polyacetals with a molecular weight (M _n ) of at least about 200 or mixtures of two or more thereof, which preferably has terminal OH groups, is therefore suitable for use as the base polymer .

Polyesters which can be used as the base polymer in the context of the present invention can be obtained in a manner known to the person skilled in the art by polycondensation of acid and alcohol components, in particular by polycondensation of a polycarboxylic acid or a mixture of two or more polycarboxylic acids and a polyol or a mixture of two or more polyols.

Polycarboxylic acids suitable for the preparation of the base polymer in the context of the present invention can be based on an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic base body and optionally, in addition to the at least two carboxylic acid groups, one or more substituents which are not reactive within the framework of a polycondensation, for example halogen atoms or have olefinically unsaturated double bonds. If necessary, instead of the free carboxylic acids, their acid anhydrides (if any) or their esters with C _L s -monoalcohols, or mixtures of two or more thereof, can be used for the polycondensation.

Suitable polycarboxylic acids are, for example, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, glutaric acid, glutaric anhydride, phthalic acid, isophthalic acid, terphthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride chlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids or trimer fatty acids or mixtures of two or more of the acids mentioned.

If necessary, minor amounts of monofunctional fatty acids can be present in the reaction mixture.

A large number of polyols can be used as diols for the production of a polyester or polycarbonate which can be used as the base polymer. For example, these are linear or branched, saturated or unsaturated aliphatic polyols with two to about ten, preferably about two to about 4, OH groups per molecule. These OH groups can be bound both primary and secondary.

Suitable aliphatic polyols include, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butenediol and 1-butynediol , 4, pentanediol-1,5, and the isomeric pentanediols, pentenediols or pentindiols or mixtures of two or more thereof, hexanediol-1, 6, and the isomeric hexanediols, hexenediols or hexindiols or mixtures of two or more thereof, heptanediol-1 , 7, and the isomeric heptane, heptene or heptinediols, 1,8-octanediol and the isomeric octane, octene or octynediols and the higher homologues or isomers of the compounds mentioned, as is known to a person skilled in the art from a gradual extension of the Hydrocarbon chain by more than one CH ₂ group or by introducing branches into the carbon chain, or mixtures of two or more thereof.

Highly functional alcohols such as glycerol, trimethylolpropane, triethylolpropane, pentaerythritol and mono-, oligo- or polymeric saccharides such as glucose, fructose, galactose, arabinose, ribose, xylose, lyxose, allose, altrose, mannose, gulose are also suitable for the production of the base polymers , Idose, Tallose and Sucrose. Also suitable are the oligomeric ethers of the substances mentioned with themselves or as a mixture of two or more of the compounds mentioned, for example polyglycerol with one Degree of polymerization from about two to about four. In the case of the higher-functional alcohols, one or more OH groups can be esterified with monofunctional carboxylic acids having 1 to about 20 C atoms, with the proviso that on average at least two OH groups are retained. The alcohols mentioned with a functionality of more than 2 can be used in pure form or, for example, as far as possible, as technical mixtures obtainable in the course of their synthesis.

Furthermore, the reaction products of low molecular weight, polyfunctional alcohols with alkylene oxides, so-called polyether polyols, can be used to prepare the base polymers. Polyether polyols which are to be used for the production of polyesters suitable as base polymers are preferably obtained by reacting polyols with alkylene oxides. The alkylene oxides preferably have 2 to about 4 carbon atoms. For example, the reaction products of ethylene glycol, propylene glycol, the isomeric butanediols or hexanediols, as mentioned above, or mixtures of two or more thereof, with ethylene oxide, propylene oxide or butylene oxide or mixtures of two or more thereof are suitable. Furthermore, the reaction products of the abovementioned alcohols with a functionality of more than 2 or their mixtures of two or more thereof, with the alkylene oxides mentioned to give polyether polyols are also suitable. Polyether polyols having a molecular weight (M _n ) of from about 80 to about 3,000, preferably from about 100 to about 2,500 and in particular from about 200 to about 2,000, are particularly suitable from the reactions mentioned. The polyether polyols mentioned can be reacted with the above-mentioned polycarboxylic acids in a polycondensation reaction to give the polyesters which can be used as base polymers.

Polyether polyols, such as those formed, for example, in the manner described above, can also be used as base polymers. Polyether polyols are usually prepared by reacting a starter compound with at least two reactive hydrogen atoms with alkylene or arylene oxides, for example ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrhydrofuran or epichlorethylene. in it or mixtures of two or more of them.

Suitable starting compounds are, for example, water, ethylene glycol, propylene glycol-1, 2 or -1.3, butylene glycol-1, 4 or -1.3, hexanediol-1, 6, octanediol-1,8, neopentylglycol, 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, hexanetriol-1, 2,6, butanetriol-1, 2,4, trimethylolethane, pentaerythritol, mannitol, sorbitol, methylglycosides, sugar, phenol, isononylphenol, resorcinol, hydroquinone, 1,2,2- or 1,1,2-tris (hydroxyphenyl) ethane, ammonia, methylamine, ethylenediamine, tetra- or hexamethylenediamine, triethanolamine, aniline, phenylenediamine, 2,4- and 2,6-diaminotoluene and

Polyphenylpoiymethylene polyamines, as can be obtained by aniline-formaldehyde condensation.

Also suitable for use as base polymers are polyether polyols which have been modified by vinyl polymers. Products of this type can be obtained, for example, by polymerizing styrene or acrylonitrile or a mixture thereof in the presence of polyethers.

A polyether polyol suitable for use as a base polymer in the context of the present invention is polypropylene glycol with a molecular weight of about 300 to about 1,500.

Polyacetals are also suitable as the base polymer. Polyacetals are understood to mean compounds as can be obtained by reacting glycols, for example diethylene glycol or hexanediol, with formaldehyde. Polyacetals which can be used in the context of the present invention can also be obtained by the polymerization of cyclic acetals.

Polycarbonates are also suitable as base polymers or as polyols for producing the base polymers. Polycarbonates can, for example, by reacting the above-mentioned polyols, in particular diols such as propylene glycol, 1,4-butanediol or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol or mixtures of two or more thereof Diaryl carbonates, for example diphenyl carbonate, or phosgene can be obtained.

Polyacrylates bearing OH groups are also suitable as base polymers or polyol components for producing the base polymers. Such polyacrylates can be obtained, for example, by polymerizing ethylenically unsaturated monomers bearing OH groups. Such monomers can be obtained, for example, by the esterification of ethylenically unsaturated carboxylic acids and difunctional alcohols, the alcohol generally being in excess. Suitable, ethylenically unsaturated carboxylic acids are, for example, acrylic acid, methacrylic acid, crotonic acid or maleic acid. Corresponding esters carrying OH groups are, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate or 3-hydroxypropyl methacrylate or mixtures of two or more thereof.

The base polymers mentioned can optionally be provided with other end groups by suitable choice of the production conditions instead of terminal OH groups. With a suitable choice of the reaction conditions, the polyesters, polyacetals or polycarbonates mentioned can have, for example, carboxyl groups as end groups or at least as part of the end groups. Suitable reactions can furthermore, for example, introduce amino groups into the base polymers.

The molecular weight of the base polymer should not exceed about 100,000. In a preferred embodiment of the present invention, the molecular weight of the base polymer is in a range from about 200 to about 30,000, for example about 300 to about 15,000 or about 500 to about 10,000.

In a preferred embodiment, hot melt adhesives according to the invention are, for example, based on base polymers with a molecular weight (M _n ) of about 500 to about 5,000, for example about 700 to about 3,000 or about 1,000 to about 2,000.

The base polymers mentioned can be used both individually and as a mixture of two or more of the base polymers mentioned in the course of the production processes described below.

In a first embodiment, the hotmelt adhesive according to the invention contains, as component A, a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group which is reactive towards a compound having an acidic hydrogen atom and a functional group which can be polymerized by UV or electron beams.

If a base polymer whose molecular weight (M _n ) is sufficiently high, for example about 5,000 or above, is used to produce the polymer which can be used as component A, a first possibility of producing component A is given below. For this purpose, the OH group-carrying base polymer is reacted with the polyfunctional compound, for example with a polyisocyanate, for example in a molar ratio of 1:> 2, the excess of polyfunctional compound being chosen, for example, to be such that a chain extension of the base is chosen Polymers are avoided but only small amounts of unreacted polyfunctional compound are present in the reaction mixture. Such a procedure can be advantageous in particular when using a polyisocyanate as a polyfunctional compound. In this way, a polymer is obtained which bears two functional groups which can be polymerized by reaction with a compound having at least one acidic hydrogen atom.

Suitable polyfunctional isocyanates which are suitable for reaction with the base polymers to produce a polymer which can be used as component A contain on average two to at most about four isocyanate groups. Examples of suitable polyisocyanates are 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (dicyclohexylmethane diisocyanate, H ₁₂ -MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4,4'- Diphenyldimethylmethane diisocyanate and di- and tetraalkyldiphenylmethane diisocyanate, 4,4-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate (TDI) and mixtures thereof, especially a Mixture containing about 20% by weight of 2,4- and 80% by weight of 2,6-tolylene di-isocyanate, 1-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6 Diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1, 5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanatophenylperfluoroethane,

Tetramethoxybutane-1,4-diisocyanate, ethylene diisocyanate, 1,2-propane diisocyanate, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,6-hexane diisocyanate (HDI), cyclohexane-1,4-diisocyanate, phthalic acid bisisocyanate ethyl ester; Polyisocyanates containing reactive halogen atoms, such as 1-chloromethylphenyl-2,4-diisocyanate, 1-bromomethylphenyl-2,6-diisocyanate or 3,3-bis-chloromethylether-4,4'-diphenyldiisocyanate or mixtures of two or more from that. Sulfur-containing polyisocyanates can also be used, as can be obtained, for example, by reacting 2 mol of hexamethylene diisocyanate with 1 mol of thiodiglycol or dihydroxydihexyl sulfide. Other diisocyanates are trimethylhexamethylene di-isocyanates, 1,4-diisocyanatobutane, 1,2-diisocyanatododecane and dimer fatty acid diisocyanates. Triisocyanatoisocyanurates can be obtained by trimerization of diisocyanates at elevated temperatures, for example at about 200 ° C. and / or in the presence of a catalyst, for example an amine, and can also be used in the context of the present invention. In the context of the present invention, the polyisocyanates mentioned can be used individually or as a mixture of two or more of the polyisocyanates mentioned. A single polyisocyanate or a mixture of two or three polyisocyanates is preferably used in the context of the present invention. HDI, MDI or TDI, for example a mixture of MDI and TDI, are preferred as polyisocyanates to be used individually or in a mixture.

In order to obtain a polymer suitable for use as component A from a polymer obtainable in this way, the polymer is advantageously reacted with a compound which has both a functional group which can be polymerized by irradiation with UV light or with electron beams and also a reaction group having a suitable functional group with the terminal functional group on the polymer. The hydroxyalkyl acrylates or methacrylates, ie the reaction products of acrylic acid or methacrylic acid with difunctional alcohols, are particularly suitable for this purpose. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate or 3-hydroxypropyl methacrylate, or mixtures of two or more thereof, are particularly suitable in the context of the present invention.

The molar ratio between the polymer and the compound, which has both a functional group which can be polymerized by irradiation with UV light or with electron beams and also a functional group capable of reacting with the terminal functional group on the polymer, can be broad in the reaction to component A. Limits vary. As a rule, it applies that a higher proportion of functional groups which can be polymerized by irradiation with UV light or with electron beams leads to a higher strength of an adhesive bond, while a higher proportion of reactive groups with a compound having at least one acidic hydrogen atom , functional groups has a higher ultimate strength.

If, for example, the polymer is used in the first production process with the compound which has both a functional group which can be polymerized by irradiation with UV light or electron beams and a functional group which is capable of reacting with the terminal functional group on the polymer, in a molar ratio of about 1: 1 .mu.m, in the polymer mixture obtainable therefrom each polymer molecule bears on average both a functional group which can be polymerized by irradiation with UV light or with electron beams and also a functional group which is reactive with a compound which has at least one acidic hydrogen atom. Accordingly, the proportions of the two types of functional groups in the polymer mixture obtainable by such a reaction can each be varied between greater than 0 and less than 100% (based on functional groups in the sense of the present invention). For example, good results can be obtained when about 1 to about 50% of the functional groups present in the polymer as terminal groups are functional groups polymerizable by irradiation with UV light or with electron beams, preferably about 5 to about 30%, and particularly preferably about 8 to about 15%. Polymers of this type are particularly suitable for use as component A.

In a second production process, suitable polymers for use in component A can also be obtained in several steps, for example, by reacting, for example in a first step, a corresponding base polymer with a molecular weight (M _n ) of about 5,000 or more with a compound which has both a functional group which can be polymerized by irradiation with UV light or with electron beams and also a functional group which is capable of reacting with the terminal OH group on the base polymer. Such a compound is, for example, styrene isocyanate. Other such compounds can be obtained, for example, by reacting an approximately equimolar amount of a hydroxyalkyl acrylate or methacrylate with a diisocyanate. The amount of compound which has both a functional group polymerizable by irradiation with UV light or with electron beams and a functional group capable of reacting with the terminal OH group on the base polymer depends on the desired content of functional groups polymerizable with electron beams Groups. A reaction of approximately equimolar amounts of both reactants leads to polymers which have an average of one functional group which can be polymerized with electron beams per molecule. This proportion can be reduced or increased accordingly by varying the molar ratios of the reactants.

This reaction produces a polymer which has both an OH group and a functional group which can be polymerized by irradiation with UV light or with electron beams. If this polymer is subsequently reacted in an at least equimolar ratio with a compound which has a functional group which is reactive with the terminal OH group of the polymer and a further functional group which is reactive towards compounds with an acidic hydrogen atom, a polymer is obtained which is used for use as Component A is suitable. The above-mentioned polyisocyanates are particularly suitable for this second reaction step in the context of the present invention.

According to a third production method, it is also possible to combine two production steps in the production of component A. For this purpose, an OH group-bearing base polymer with a molecular weight (M _n ) of 5,000 or more, a polyiisocyanate or a polyepoxide, in particular a diisocyanate or a diepoxide, or a mixture thereof, or optionally one or more other polyfunctional compounds in the sense of and a compound which has both a functional group which can be polymerized by irradiation with UV light or electron beams and a functional group which is capable of reacting with the terminal OH group on the base polymer are reacted with one another in a suitable molar ratio. The molar ratios are chosen so that the proportions of the two types of functional groups in the polymer mixture obtainable by such a reaction each vary between greater than 0% and less than 100% (based on functional groups). Good results can also be obtained in this case, for example, when about 1 to about 50% of the functional groups present as terminal groups in the polymer are functional groups which can be polymerized by irradiation with UV light or electron beams, preferably about 5 to about 30%, and particularly preferably about 8 to about 15%.

If base polymers whose molecular weight (M _n ) is less than about 5,000 are used for the production of component A, the production processes given above do not lead to the goal, since only a slight increase in the molecular weight is achieved with the processes mentioned.

If necessary, the molecular weight of the base polymer must therefore be increased in order to produce the polymer which can be used in the composition according to the invention. The molecular weight can be increased, for example, by chain extension of the base polymer. For this purpose, the base polymer is advantageously first used with a reference to the terminal one Groups of the base polymer polyfunctional, preferably difunctional compound implemented.

Polyepoxides, in particular diepoxides, or preferably polyisocyanates, in particular diisocyanates of the type already mentioned, are particularly suitable as polyfunctional compounds in this sense. The diisocyanates are particularly preferred in the context of the present invention. The stoichiometric ratios between base polymer and polyfunctional compound required to achieve a certain increase in molecular weight are known to the person skilled in the art.

In a preferred embodiment of the invention, the chain extension is carried out with an excess of base polymer in the chain extension reaction. As a result of such a reaction procedure, the resulting chain-extended base polymers have the original type of terminal functional groups as terminal functional groups.

In a fourth production process of a polymer which can be used as component A, an OH group-bearing base polymer with a molecular weight (M _n ) of less than 5,000 or a mixture of such OH group-bearing base polymers is therefore firstly used with a suitable amount of chain extenders , for example polyepoxides or polyisocyanates, preferably polyisocyanates, implemented while maintaining the original type of the terminal functional group (chain extended), the ratio of terminal functional groups in the base polymer to functional groups in the chain extender being greater than 1. The conversion to component A then takes place, it then being possible, for example, to use one of the production processes already described.

In a fifth production process, the production of component A can be shortened, for example, by one step or can be carried out in one step if, during chain extension, there is already a compound which is polymerizable both by irradiation with UV light or with electron beams functional group as well as a functional group capable of reacting with the terminal functional group of the base polymer.

In the course of this procedure, for example, a polymer suitable for use as component A can be obtained if, at the same time as the chain extension, for example with one or more of the above-mentioned polyisocyanates, the base polymer is reacted with one or more compounds which both by Irradiation with UV light or electronically polymerizable functional group as well as a functional group capable of reacting with the terminal functional group on the base polymer. The reactants are brought to the reaction in a suitable molar ratio.

In a sixth production process, a base polymer with a molecular weight (M _π ) of 5,000 or more can be assumed, which was produced using one or more components which contain functional groups which can be polymerized by UV or electron radiation. To produce such a polymer which can be used as component A, the corresponding base polymer is reacted with a compound which, as the first functional group, has both a group reactive with the terminal functional groups of the base polymer and, as the second functional group, one with a compound with a acidic hydrogen atom reactive functional group. As a rule, the first and the second functional group will meet both conditions. However, it is possible e.g. B. with first and second functional groups with different reactivity, by a suitable choice of reaction conditions to achieve a selective reaction, for example, of the first functional group with the terminal groups of the base polymer, while the second functional group is not with the terminal functional group of the base polymer responds. An example of such a combination of first and second functional groups is, for example, the combination of epoxy group and NCO group. The reaction is carried out, for example, in such a way that the molar ratio of base polymer to the corresponding compound is approximately 1:> 2 . In a seventh production process for polymers which can be used as component A, the procedure is identical to the sixth production process, only the molar ratio of base polymer to the compound which, as the first functional group, is both a group reactive with the terminal functional groups of the base polymer and as second functional group has a functional group which is reactive towards a compound having an acidic hydrogen atom, is chosen such that, when the reaction is carried out appropriately (both functional groups of the compound must react with the terminal groups of the base polymer), a chain extension to the desired molecular weight occurs.

In the latter two methods, base polymers are preferably used which have about 2 to about 5 functional groups polymerizable by UV or electron beams per polymer molecule.

Component A which can be used in the context of the present invention can contain, for example, only one of the abovementioned polymers. However, mixtures of two or more of the polymers mentioned can also be used as component A.

Typical polymers suitable for use in component A have a viscosity of about 3,000 mPas to about 20,000 mPas, in particular about 5,000 mPas to about 15,000 mPas at about 80 to about 180 ° C., in particular at about 100 to about, at processing temperatures suitable for typical applications 140 ° C, on (Brookfield CAP 200, cone 6, 50 rpm, measuring time 25 s). Typical processing temperatures are, for example, about 100 to about 150 ° C, in particular about 110 to about 140 ° C, for example about 120 to about 130 ° C, e.g. B. in the production of flexible packaging cardboard.

Typical NCO values for polymers suitable for use as component A are about 0.5% by weight to about 10% by weight, in particular about 3.5% by weight to about 5% by weight. In the context of the present invention, the term “component B” refers to a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group which is reactive towards a compound having an acidic hydrogen atom and no functional group which can be polymerized by UV or electron beams , Roger that.

To produce a polymer which can be used as component B, the base polymer is reacted with a compound which, as the first functional group, is both a group reactive with the terminal functional groups of the base polymer and, as the second functional group, is a compound with an acidic hydrogen atom has reactive functional group. As a rule, the first and the second functional group will meet both conditions. However, it is possible, for example, in the case of first and second functional groups with different reactivity, to achieve a selective reaction, for example of the first functional group with the OH groups of the base polymer, by suitable choice of the reaction conditions, while the second functional group is not with the terminal functional group of Base polymer reacts. An example of such a combination of first and second functional groups is, for example, the combination of epoxy group and NCO group.

The polymer suitable for use as component B is preferably reacted by reacting a base polymer or a mixture of two or more base polymers with a compound bearing at least two groups which are reactive toward the terminal functional groups. The molar ratio of the reactants during the reaction is chosen, for example, such that, after the reaction has ended, there are essentially no more OH groups in the reaction mixture. If appropriate, the molecular weight of the base polymer may be too low to achieve the molecular weight of approximately 5,000 (M _n ) required for use as component B after reaction with the compound bearing at least two functional groups which are reactive toward OH groups. In this case, the ratio between the at least two functional groups reactive towards OH groups bearing compound and the H groups of the base polymer and, if appropriate, the reaction conditions (if the at least two compounds bearing functional groups reactive toward OH groups have two differently reactive functional groups) are selected such that a chain extension of the base polymer or of the mixture takes place from two or more base polymers.

In a preferred embodiment of the invention, the base polymer or the mixture of two or more base polymers is reacted with a polyisocyanate, in particular a diisocyanate.

Component B which can be used in the context of the present invention can contain, for example, only one of the abovementioned polymers. However, mixtures of two or more of the polymers mentioned can also be used as component B.

Since the polymer which can be used as component B, in addition to the at least one functional group which is reactive toward a compound having an acidic hydrogen atom, should not have any functional group which can be polymerized by UV or electron beams, no base polymers can be used in the preparation of the polymers which can be used as component B, which were manufactured using olefinically unsaturated components.

The polymer which can be used as component B has an NCO group content of from about 0.5 to about 10% by weight. in particular about 2.5 to about 5% by weight.

The viscosity of the polymer which can be used as component B at typical processing temperatures is about 2,000 to about 60,000 mPas, in particular about 4,000 to about 20,000 mPas (Brookfield RVT D, spindle 27, 110 to 130 ° C.).

Typical processing temperatures are about 100 to about 150 ° C, especially about 110 to about 140 ° C, for example about 120 to about 130 ° C, e.g. B. in the production of flexible packaging boxes. The polymer component used as component A or B can each consist of only one of the polymers described, but it can also be a mixture of two or more of the polymers mentioned. For example, it is advantageous if a mixture of one or more polyester polyols and one or more polyether polyols is used as the base polymer. The various base polymers can differ, for example, in the molecular weight (M _n ) or in the chemical structure, or in both.

For example, about 20 to about 40% by weight of polyester polyols and about 20 to about 60% by weight of polyether polyols, based on the entire component A or B, can be used as the corresponding base polymers for the production of components A or B. In a further preferred embodiment, in addition to a polyester polyol, for example, at least two different polyether polyols are used as base polymers, e.g. a mixture of a polyether polyol with a molecular weight of about 800 to about 1,500 and a polyether polyol with a molecular weight of about 300 to about 700.

In a further preferred embodiment, however, only a terminal OH group, preferably difunctional polyester, or a mixture of two or more such polyesters, is used as the base polymer for the production of component A or B. A polyester which is at least partially crystalline is advantageously chosen as the base polymer, or a mixture of two or more polyesters is used, at least one of which is crystalline or partially crystalline.

For the purposes of the present text, a polymer is understood to be "crystalline" or "partially crystalline" if, when examined by means of differential scanning calorimetry (DSC), it exhibits at least one first order thermal transition, ie at least one enthalpic transition, which is associated with a melting process can be. Crystalline or at least predominantly crystalline polyesters can be obtained, for example, by polycondensation of polyfunctional aromatic carboxylic acids or their acid anhydrides (if any) with short-chain aliphatic diols having about 2 to about 6 carbon atoms. For the production of partially crystalline polyesters, for example, alcohols with a higher number of carbon atoms or branched or unsaturated, in particular cis-unsaturated alcohols can be used.

Suitable aromatic carboxylic acids are phthalic acid, phthalic anhydride, terephthalic acid, trimellitic acid, trimellitic anhydride, tetrachlorophthalic acid, tetrachlorophthalic anhydride or naphthalenedicarboxylic acid.

Suitable alcohols are, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 4, 1,3-butanediol, 2,3-butanediol, 1,4-butenediol, 1,4-butynediol, 4, pentanediol -1, 5, and the isomeric pentanediols, pentenediols or pentindiols or mixtures of two or more thereof, hexanediol-1, 6, and the isomeric hexanediols, hexenediols or hexindiols or mixtures of two or more thereof, heptanediol-1, 7 and the isomeric heptane, heptene or heptinediols, octanediol-1,8 and the isomeric octane, octene or octynediols, and the higher homologues or isomers of the compound mentioned, as is known to the person skilled in the art from a gradual extension of the hydrocarbon chain by one each CH ₂ group or introducing branches into the carbon chain, or mixtures of two or more thereof. If the polyesters are to have as crystalline properties as possible, then the use of branched alcohols should be avoided. To produce partially crystalline polyesters, branched alcohols can be present in different amounts during the polycondensation.

In a preferred embodiment of the present invention, the base polymer carrying OH groups is a partially crystalline polyester or a mixture of partially crystalline polyesters or a mixture of crystalline and partially crystalline polyesters or a mixture of crystalline and amorphous polyesters or a mixture of partially crystalline and amorphous polyesters or a mixture of crystalline, semi-crystalline and amorphous polyesters used, in which the Crystallinity is about 1 to about 70%, for example about 5 to about 50% and in particular about 10 to about 30% (based on the polymer or the mixture).

In the context of the present invention, the term “component C” is understood to mean a compound having a functional group which can be polymerized by UV or electron beams and a molecular weight of less than 5,000.

In a preferred embodiment of the invention, the compound which can be used as component C has a molecular weight of about 80 to about 3,000, in particular about 100 to about 1,000.

For example, acrylate or methacrylate esters with one or more olefinically unsaturated double bonds are suitable as component C. Such acrylate or methacrylate esters include, for example, esters of acrylic acid or methacrylic acid with aromatic or aliphatic linear or branched, saturated or unsaturated aliphatic or cycloaliphatic, monoalcohols or acrylate esters of polyether monoalcohols.

In a preferred embodiment of the present invention, as component C, for example esters of acrylic acid or methacrylic acid with aromatic or linear or branched, saturated or unsaturated C 1-4 alcohols are used. For example, these are esters of acrylic or methacrylic acid with hexyl, heptyl, octyl or 2-ethylhexyl alcohol. The esters of acrylic or methacrylic acid with phenol, methylphenol or benzyl alcohol are also suitable. Also suitable are the esters of acrylic or methacrylic acid with fatty alcohols, for example capron alcohol, caprylic alcohol, 2-ethylhexyl alcohols such as capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, baelyl alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol, oleyl alcohol, Erucyl alcohol and brassidyl alcohol and their technical mixtures, such as those used in the high-pressure hydrogenation of technical methyl esters based on fats and oils or aldehydes from the Roelen's oxosynthesis and as a monomer fraction in the dimerization of unsaturated fatty alcohols.

Di- or higher-functional acrylate or methacrylate esters are also suitable as component C. Such acrylate or methacrylate esters include, for example, esters of acrylic acid or methacrylic acid with aromatic, aliphatic or cycloaliphatic polyols with at least two OH groups or acrylate or methacrylate esters of polyether alcohols with at least two OH groups.

A large number of polyols can be used as polyols for producing an acrylate or methacrylate ester which can be used as component C. For example, these are aliphatic polyols with 2-4 OH groups per molecule and 2 to about 40 C atoms. The OH groups can be bound either primary or secondary. Suitable aliphatic polyols include, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butenediol, 1,4-butynediol , Pentanediol-1,5, and the isomeric pentanediols, pentenediols or pentindiols or mixtures of two or more thereof, 1,6-hexanediol, and the isomeric hexanediols, hexenediols or hexindiols or mixtures of two or more thereof, heptanediol-1, 7 as well as the isomeric heptane, heptene or heptinediols, 1,8-octanediol and the isomeric octane, octene or octynediols, and the higher homologues or isomers of the compounds mentioned, as is known to the person skilled in the art from a gradual extension of the hydrocarbon chain each give a CH ₂ group or by introducing branches into the carbon chain, or mixtures of two or more thereof.

Highly functional alcohols such as, for example, glycerol, trimethylolpropane, pentaerythritol or sugar alcohols such as sorbitol or glucose, and oligomeric ethers of the substances mentioned with themselves or in a mixture of two or more of the compounds mentioned, for example polyglycerol with a degree of polymerization of about 2 to about, are also suitable 4. In the case of the higher-functional alcohols, one or more OH groups can be used monofunctional carboxylic acids with 1 to about 20 C atoms are esterified, with the proviso that on average at least two OH groups are retained. The higher-functionality alcohols mentioned can be used in pure form or, if possible, as the technical mixtures obtainable in the course of their synthesis.

Furthermore, the reaction products of low molecular weight, polyfunctional alcohols with alkylene oxides, so-called polyether polyols, can be used as the polyol component for the preparation of the acrylate or methacrylate esters. Polyether polyols which are to be used for the production of polyesters suitable as base polymers are preferably obtained by reacting polyols with alkylene oxides. The alkylene oxides preferably have two to about four carbon atoms. For example, the reaction products of ethylene glycol, propylene glycol, the isomeric butanediols or hexanediols, as mentioned above, or mixtures of two or more thereof, with ethylene oxide, propylene oxide or butylene oxide or mixtures of two or more thereof are suitable. Furthermore, the reaction products of polyfunctional alcohols, such as glycerol, trimethylolethane or trimethylolpropane, pentaerythritol or sugar alcohols or mixtures of two or more thereof, with the alkylene oxides mentioned to form polyether polyols are also suitable. Polyether polyols with a molecular weight (M _n ) of about 100 to about 2000, preferably of about 150 to about 1500, in particular of about 150 to about 800, obtainable from the reactions mentioned are particularly suitable.

Acrylate esters of aliphatic diols with 2 to about 40 carbon atoms include, for example, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and (meth) acrylate esters of sorbitol and other sugar alcohols. These (meth) acrylate esters of aliphatic or cycloaliphatic diols can be modified with an aliphatic ester or an alkylene oxide. The aliphatic ester-modified acrylates include, for example, neopentylglycol hydroxypivalate di (meth) acrylate, caprolactone-modified neopentylglycol hydroxypivalate di (meth) acrylates and the like. The alkylene oxide modified acrylate compounds include, for example, ethylene oxide-modified neopentyl glycol di (meth) acrylates, propylene oxide-modified

Neopentyl glycol di (meth) acrylates, ethylene oxide-modified 1, 6-hexanediol di (meth) acrylates or propylene oxide-modified 1, 6-hexanediol di (meth) acrylates or mixtures of two or more thereof.

Acrylate monomers based on polyethene polyols include, for example, neopentyl glycol-modified trimethylolpropane di (meth) acrylates, polyethylene glycol di (meth) acrylates, polypropylene glycol di (meth) acrylates and the like. Trifunctional and higher functional acrylate monomers include, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerytrhitol penta (meth) acrylate, dipentaerythritol hexa- xa (meth) acrylate, caprolactone (methitol) modified dipitol acrylate, pentaerythritol tetra (meth) acrylate, tris [(meth) acryloxyethyl] isocyanurate, caprolactone-modified tris [(meth) acryloxyethyl] isocyanurate or trimethylolpropante- (meth) acrylate or mixtures of two or more thereof.

In a preferred embodiment of the present invention, component C, for example, phenyl acrylate, phenyl methacrylate or phenoxyethyl acrylate is used.

Among the di-, tri- or higher-functional acrylate monomers mentioned which can be used according to the invention as component C, tripropylene glycol diacrylate, neopentyl glycol propoxylate di (meth) acrylate, trimethylolpropane tri (meth) acrylate and pentaerythritol triacrylate are preferred.

In a further preferred embodiment of the present invention, a compound selected from the group consisting of monomeric, oligomeric or polymeric esters of acrylic acid, methyl acrylic acid, ethyl acrylic acid, propylacrylic acid or butylacrylic acid with an aromatic or aliphatic monofunctional or polyfunctional alcohol is used as component C, the ester has a boiling point of at least 100 ° C. In addition to the combinations of components A, B and C mentioned at the beginning, the hotmelt adhesive according to the invention can contain, as component D, a photoinitiator which initiates a polymerization of olefinically unsaturated double bonds under UV radiation. This is particularly advantageous if the adhesive is to be polymerized by the action of UV radiation.

In such cases, component D is therefore a photoinitiator which, when irradiated with light of a wavelength of about 260 to about 480 nm, is capable of initiating a radical polymerization of olefinically unsaturated double bonds. In the context of the present invention, all commercially available photoinitiators which are compatible with the adhesive according to the invention, ie. H. result in at least largely homogeneous mixtures.

For example, these are all Norrish Type I substances that fragment. Examples include benzophenone, camphorquinone, quantacure (manufacturer: International Bio-Synthetics), Kayacure MBP (manufacturer Nippon Kayaku), Esacure BO (manufacturer: Fratelli Lamberti), Trigonal 14 (manufacturer: Akzo), photoinitiators from Irgacure ^® -, Darocure ^® - or Speedcure ^® series (manufacturer: Ciba-Geigy), Darocure ^® 1173 or Fi-4 (manufacturer: Eastman) Irgacure ^® 651, Irgacure ^® 369, Irgacure ^® 184, Irgacure ^® 907, Irgacure ^® 1850, are particularly suitable. Irgacure ^® 1173 (Darocure ^® 1173), Irgacure ^® 1116, Speedcure ^® EDB, Speedcure ^® ITX, Irgacure ^® 784 or Irgacure ^® 2959 or mixtures of two or more thereof.

Conventional low molecular weight photoinitiators can possibly contribute to migratation in composite materials. The photoinitiators contained in the adhesive themselves are suitable as migrates, but another source of migratory agents are also fragments of the photoinitiators, such as may arise when the adhesive is irradiated with UV rays. Under certain circumstances, for example in the production of composite materials which are intended to serve for food packaging, the aim is to avoid migrable compounds in the adhesive as far as possible. The content of migratable compounds in the adhesive according to the invention can be found in the As a rule, lower it even further if the photoinitiator has a molecular weight that largely complicates or even prevents migration.

In the context of a preferred embodiment, component D therefore contains, at least in part, a photoinitiator which has a molecular weight of more than about 200. Commercially available photoinitiators that meet this condition are, for example, Irgacure® 651, Irgacure® 369, Irgacure® 907, Irgacure® 784, Speedcure® EDB, or Speedcure® ITX.

However, photoinitiators which meet the above-mentioned condition with regard to their molecular weight can also be obtained by reacting a low molecular weight photoinitiator which has a functional group which is reactive toward isocyanates, for example an amino group or an OH group, with a high molecular weight compound having at least one isocyanate group (polymer-bound photoinitiators) . Compounds which carry more than one photoinitiator molecule, for example two, three or more photoinitiator molecules, are preferably used as component D. Such compounds can be obtained, for example, by reacting a polyfunctional alcohol having two or more OH groups with suitable di- or triisocyanates and photoinitiators with a suitable functional group which is reactive toward isocyanates.

All of the above-mentioned polyfunctional alcohols can be used as polyfunctional alcohols, but especially neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol and their alkoxylation products with C ₂ alkylene oxides. Also suitable as polyfunctional alcohols, and particularly preferred in the context of the present invention, are the reaction products of trihydric alcohols with caprolactone, for example the reaction product of trimethylolpropane with caprolactone (Capa 305, Interox, Cheshire, UK, molecular weight (M _n ) = 540) .

In a further preferred embodiment of the invention, component D contains a photoinitiator which can be obtained by an at least trihydric alcohol is reacted with caprolactone to form a polycaprolactone having at least three OH groups and having a molecular weight of about 300 to about 900, and then the polycaprolactone using a compound carrying at least two isocyanate groups with 1- [4- (2-hydroxyethoxy) phenyl] -2- hydroxy-2-methyl-propan-1-one is linked.

All diisocyanates mentioned in the context of this text are suitable as compounds bearing at least two isocyanate groups, in particular as diisocyanates for reaction with the polyols mentioned. However, the 2,4- and 2,6-isomers of TDI are particularly preferred, it being possible for the isomers to be used in their pure form or as a mixture.

Suitable photoinitiators for producing the polymer-bound photoinitiators are, for example, all photoinitiators which have a functional group which is reactive toward isocyanate groups. In the context of the present invention, particular preference is given to 1 - [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methylpropan-1 - one (Irgacure® 2959), which has a primary bonded OH group.

If necessary, the photoinitiators which can be used in component D can also be prepared by using a minor amount of photoinitiator molecules which are reactive toward isocyanate groups in the production of component A or component B or in both production processes. This leads to a connection of a photoinitiator to a molecule of component A or component B.

It is also possible to achieve the connection of the photoinitiator to a polymer chain, for example to component A or B, by adding the photoinitiator having a corresponding functional group in monomeric form to the adhesive, and then, for example during a storage period of the adhesive , reacts with a corresponding polymeric component, for example component A or B.

It is also possible to use a photoinitiator with UV radiation. To provide light or a functional group polymerizable with electron beams, the functional group polymerizable with UV light or electron beams being able to be connected to the photoinitiator, for example by reaction of the photoinitiator with an unsaturated carboxylic acid. Examples of suitable unsaturated carboxylic acids are acrylic acid or methacrylic acid. The reaction products of Irgacure® 2959 with acrylic acid or methacrylic acid are particularly suitable in the context of the present invention.

It is accordingly possible that a compound is used as component D which is both a photoinitiator and a functional group which can be polymerized by irradiation with UV light or with electron beams or a functional group capable of reacting with a compound having at least one acidic hydrogen atom, or has both.

In addition to the above-mentioned combinations of components A, B, C and D, the adhesive according to the invention can also contain further additives as component E.

The additives which can be used in their entirety as component E in the context of the present invention include, for example, plasticizers, stabilizers, antioxidants, dyes, fillers, catalysts, accelerators, defoamers or flow control agents.

Examples of plasticizers used are plasticizers based on phthalic acid, in particular dialkyl phthalates, phthalic esters which have been esterified with a linear alkanol having from about 6 to about 12 carbon atoms being preferred as plasticizers. Dioctyl phthalate is particularly preferred.

Also suitable as plasticizers are benzoate plasticizers, for example sucrose benzoate, diethylene glycol dibenzoate and / or diethylene glycol benzoate, in which about 50 to about 95% of all hydroxyl groups have been esterified, phosphate plasticizers, for example t-butylphenyldiphenylphosphate, polyethylene glycols and their derivatives, for example diphenyl ether of poly (ethylene glycol), liquid resin derivatives, for example the methyl ester of hydrogenated resin, vegetable and animal oils, for example glycerol esters of fatty acids and their polymerization products.

Stabilizers or antioxidants which can be used as additives in the context of the invention include phenols, sterically hindered phenols of high molecular weight (M _n ), polyfunctional phenols, sulfur- and phosphorus-containing phenols or amines. Phenols which can be used as additives in the context of the invention are, for example, hydroquinone, hydroquinone methyl ether 2,3- (di-tert-butyl) hydroquinone, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert -butyl-4-hydroxybenzyl) benzene; Pentaerythritol tetra-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl-3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4-methylenebis (2,6-di-tert-butylphenol); 4,4-thiobis (6-tert-butyl-o-cresol); 2,6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2,4-bis (n-octylthio) -1, 3,5-triazine; Di-n-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate; 2- (n-octylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; as well as p-hydroxydiphenylamine or N, N'-diphenylenediamine or phenothiazine.

Further additives can be included in the adhesives according to the invention in order to vary certain properties. These can include, for example, dyes such as titanium dioxide, fillers such as talc, clay and the like. If necessary, small amounts of thermoplastic polymers can be present in the adhesives according to the invention, for example ethylene vinyl acetate (EVA), ethylene acrylic acid, ethylene methacrylate and ethylene-n-butyl acrylate copolymers, which optionally give the adhesive additional flexibility, toughness and strength. It is also possible to add certain hydrophilic polymers, for example polyvinyl alcohol, hydroxyethyl cellulose, hydroxy propyl cellulose, polyvinyl methyl ether, polyethylene oxide, polyvinyl pyrrolidone, polyethyloxazoiine or starch or cellulose esters, in particular the acetates with a degree of substitution of less than 2.5, which, for example, affect the wettability of the Increase adhesives. The adhesive according to the invention can optionally contain the described components alone or, for example, in the following combinations: component A, components A and B, components A and C, components B and C, components A and D, components A and E, components A, B and C, components B, C and D, components B, C and E, components A, B, C and D, components A, B, C and E, components A, C, D and E, components B, C, D and E and components A, B, C, D and E.

If a combination containing this component is desired, the adhesive according to the invention contains component A in an amount of up to about 100% by weight, based on the total hot melt adhesive. If component A is not used alone, the hotmelt adhesive according to the invention contains up to about 99.99% by weight of component A. In this case, the lower limit of the component A content should be at least about 0.01% by weight.

If a combination containing this component is desired, the adhesive according to the invention contains component B in an amount of up to about 99% by weight, based on the total hot melt adhesive. In a particular embodiment, the hotmelt adhesive according to the invention contains about 10% by weight to about 98% by weight, in particular about 80% by weight to about 95% by weight of component B. The lower limit of the component B content should be in the case of the use of which is at least about 0.01% by weight.

If a combination containing this component is desired, the adhesive according to the invention contains component C in an amount of up to about 50% by weight, based on the total hot melt adhesive. In a particular embodiment, the hotmelt adhesive according to the invention contains about 2% by weight to about 40% by weight, in particular about 5% by weight to about 30% by weight of component C. The lower limit of the component C content should be in the case of the use of which is at least about 0.01% by weight.

If a combination containing this component is desired, the adhesive according to the invention contains component D in an amount of up to about 50 % By weight based on the total adhesive, the lower limit should in this case be about 0.01% by weight. Based on the individual photoinitiator molecule in component D itself, regardless of whether it is covalently bound to a further compound, the proportion of the adhesive should be at least about 0.01% by weight to about 10% by weight, preferably is a proportion of approximately 0.5 to approximately 5% by weight and particularly preferably approximately 1 to approximately 3% by weight, based on the total adhesive.

In a preferred embodiment, the hotmelt adhesive according to the invention contains components A, B, C, D and E in the combinations given above in such a ratio that a molded body consisting of the hotmelt adhesive is dimensionally stable at room temperature.

The term “dimensionally stable at room temperature” is understood to mean a state in which a molded body consisting of the hotmelt adhesive according to the invention maintains its external shape at least over 2 hours at 20 ° C. or at least essentially maintains it, with an insignificant change in shape merely resulting in a change of Expresses structures with a small spatial extent, for example in a slight rounding of the corners of a cubic egg or the like produced from the composition according to the invention. However, the term "dimensionally stable" means that the composition can exhibit a plastic behavior in relation to external forces (cold stretching, cold flow).

The invention further relates to a method for producing a composite material comprising at least two layers, in which a hotmelt adhesive according to the invention is applied to a first side of a first layer at a temperature of at least 40 ° C., and then a second layer to the adhesive side of the first layer is laminated and the material thus obtained is then subjected to a treatment with UV or electron beams.

The processing of the hot melt adhesive according to the invention takes place at The method according to the invention generally by applying the adhesive to the first layer and, if appropriate, further layers by means of conventional application methods in the molten state. Suitable application methods are, for example, application by rollers, slot nozzles, spray nozzles, screen printing, dipping or anilox rollers.

In a preferred embodiment of the method according to the invention, the treatment with UV or electron beams takes place at a temperature of more than 30 ° C., in particular at a temperature of more than 50 ° C.

The adhesive solidifies after the first hardening step caused by cooling and the second hardening step caused by electron radiation, in a third hardening step by the presence of at least one functional group which is reactive towards a compound having an acidic hydrogen atom. As a rule, this will be due to a reaction of the groups mentioned with moisture, for example atmospheric moisture. The further solidification usually takes place over a longer period of time, which can be, for example, about one day or a few days up to about a week or more, for example about two weeks, at ambient temperature (about 15 to about 25 ° C.).

However, it is also possible to influence the speed of the third solidification stage, for example by changing the moisture conditions or increasing the temperature, or both, simultaneously or in succession. This can either be done directly after the electron beam treatment or only after some time.

Another object of the invention is an at least two-day composite material with a thickness that exceeds the level of the materials usually used in film lamination, a material connection between at least two of the layers being produced by means of a hot melt adhesive according to the present invention. The thickness of such materials is generally more than about 200 μm, for example more than about 250 or about 300 μm. If appropriate, the thickness of such materials can even be more than about 400, 500, 600 or more than about 800 μm.

The hotmelt adhesive according to the invention is also expediently used for the production and closure of folding boxes or cartons for highly stressed applications, e.g. for frozen food (ready to bake meals), baby food, cosmetics, pharmaceuticals, beverages,

Sterilization packs such as medical devices and bandages. So far, thermoplastic hot melt adhesives or dispersions have been used for this. This had the disadvantage that the cardboard could only achieve a limited functionality due to the thermoplasticity, such as the use of an inner bag e.g. necessary for high temperature or low temperature loads.

The networked adhesive system according to the invention makes it possible to produce, fill and seal highly loaded packaging without an inner bag on conventional systems, which only need to be equipped with a UV or electron emitter. In addition, the production process is reduced by the bagging process. This gives the outer packaging or the outer carton the character of a functional packaging and is therefore to be assessed differently economically and ecologically.

The invention is explained in more detail below by examples.

Examples:

An adhesive according to the invention was produced as follows:

700 g of a first polyester (OH number = 60) and 100 g of a second polyester (OH number = 30), prepared from the components phthalic acid, isophthalic acid, terephthalic acid, diethylene glycol, dipropylene glycol, hexanediol and butanediol, and 20 g MDI were presented and subjected to polyaddition at 120 ° C for 30 minutes. Then 100 g of phenoxyethyl acrylate were added and the polyaddition reaction was continued for a further 20 minutes. The resulting NCO-terminated prepolymer had a viscosity of approximately 10,000 mPas at 120 ° C.

The product was dimensionally stable at room temperature and had a melting point of more than about 80 ° C.

5% by weight of a photoinitiator was added to part of the prepolymer. This product (Example 1) was applied at 120 ° C. on a SiOx-vapor-coated PETP film. It was then bonded with a PETP film and with a SiOx-vaporized PETP film and the bond was irradiated with 400 watt / 400 cm ² UV light (mercury vapor) (see table for the result).

A second part of the prepolymer was applied to the abovementioned films at 120 ° C. without the addition of a photoinitiator (Example 2) and, after bonding with an electron beam, irradiated with 2 megarads of rays (table results). Results UV and EB curing

1

The table shows that the composition according to the invention ensures a high initial adhesion due to the character of a hot melt adhesive. Characteristic is a quick tightening of the adhesion (within a few seconds) by irradiation and a quick reaching of a cross-linked film (material tear after one day). Furthermore, the composite materials produced in this way show a high final adhesion due to the final isocyanate hardening.

Claims

claims

1. Hot melt adhesive with a melting point of at least 40 ° C, containing a component A or a component A and a component B or a component B and a component C or a component A and a component C or components A, B and C, where a ) as component A, a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group that is reactive towards a compound with an acidic hydrogen atom and a functional group that can be polymerized by UV or electron beams, b) as component B, a polymer with a molecular weight (M _n ) of at least 5,000, which has at least one functional group reactive towards a compound with an acidic hydrogen atom and no functional group polymerizable by UV or electron beams and c) as component C a compound with a polymerizable by UV or electron beams functional group and a molecular weight of we less than 5,000 is included.

2. Hot melt adhesive according to claim 1, characterized in that the composition has a melting point of at least 60 ° C.

3. Hot melt adhesive according to one of claims 1 or 2, characterized in that it has a viscosity of 5,000 to 15,000 mPas (Brookfield RVT D, spindle 27) at 120 ° C to 180 ° C.

. Hot melt adhesive according to one of claims 1 to 3, characterized in that as component C contain a compound selected from the group consisting of monomeric, oligomeric or polymeric esters of acrylic acid, methyl acrylic acid, ethyl acrylic acid, propylacrylic acid or butyl acrylic acid with an aromatic or aliphatic monofunctional or polyfunctional alcohol is, the ester has a boiling point of at least 100 ° C.

5. Hot melt adhesive according to one of claims 1 to 3, characterized in that a polyurethane is present as component A or B or A and B.

6. Hot melt adhesive according to one of claims 1 to 5, characterized in that as component A or B or A and B a polyurethane, obtainable by reacting an at least difunctional isocyanate with a crystalline or partially crystalline polyester or a mixture of two or more polyesters, wherein at least one of the polyesters in the mixture is crystalline, is contained.

7. Hot melt adhesive according to one of claims 1 to 6, characterized in that component A or B or A and B as a functional group reactive towards a compound having an acidic hydrogen atom is an NCO, epoxy, anhydride or carboxyl group or a mixture of two or more of it.

. A process for producing a composite material comprising at least two layers from a first and a second layer, in which a hot melt adhesive according to one of claims 1 to 7 is applied to a first side of the first layer at a temperature of at least 40 ° C, then the second layer is laminated onto the adhesive side of the first layer and the material thus obtained is then subjected to a treatment with UV or electron beams.

9. The method according to claim 8, characterized in that the treatment with UV or electron beams takes place at a temperature of more than 30 ° C.

10. The method according to any one of claims 8 or 9, characterized in that the treatment with UV or electron beams takes place at a temperature of more than 50 ° C.

11. At least two-layer composite material, with a thickness that goes beyond the amount of the materials usually used in the film lamination, wherein a material connection between at least two of the layers is made by means of a hot melt adhesive according to one of claims 1 to 7.

12. Use of the hot melt adhesive according to at least one of claims 1 to 7 for the manufacture and closure of folding boxes or cartons for highly stressed applications.