Polyurethane adhesive having high chemical resistance

Abstract

To provide an adhesive composition that is free of migratable compounds such as cyclic esters and at the same time withstands the high mechanical, chemical and thermal stresses encountered in the field of food packaging.SOLUTION: The present invention provides an adhesive composition comprising: a polyether having a urethane group density of 2 to 10 urethane groups per mole of polyether; and at least one NCO-terminated compound. The polyether is prepared by reacting a polyol with a specific isocyanate, and the urethane group density of the polyether is determined by the following formula.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to polyethers having a urethane group density of 2 to 10 urethane groups per mole of polyether, polyurethane (PU) adhesives comprising the polyethers and at least one NCO-terminated compound, and the use of the polyurethanes for producing packaging, in particular food packaging. [Background technology]

[0002] Polyurethane adhesives have various applications, especially in the production of flexible packaging, such as those commonly used in the field of food packaging. When high requirements are placed on the composite material in particular, polyester-based polyurethane adhesives are no longer conceivable. In addition to being exposed to high levels of chemical and thermal stress, adhesives used in the production of food packaging must also comply with a wide range of food regulatory specifications, which vary from region to region, as laid out, for example, by the US Food and Drug Administration (FDA) or in the European Regulation on Plastic Materials EC10 / 2011.

[0003] In addition to the restrictions resulting from legal regulations, the mechanical stresses caused by the weight of the packaged food must be taken into account, as well as the fact that the materials used are subject to attack by the packaged food itself or its components. As a result, producing stable packaging, for example in the field of animal foods, especially wet foods, involves significant difficulties due to the aggressive nature of the ingredients and the quantities to be packaged.

[0004] US Patent No. 5,096,980 describes a polyurethane / adhesive composition that provides excellent adhesion behavior to packaged or encased contents and to boiling water. The claimed composition comprises an organic polyisocyanate, a polyol, 0.01-10% by weight of an oxoacid of phosphorus or its derivatives, 9.91-20% by weight of a carboxylic acid or its anhydride, and 0.1-50% by weight of an epoxy resin.

[0005] EP1983011 relates to a method for preparing a lamination adhesive for shrink-wrap products, in which a mixture is prepared containing 50-98% by weight of a hydroxy-terminated polyester having a hydroxyl number of 50-350 and a hydroxyl functionality of 2-3, 1-30% by weight of an epoxy resin having an epoxy equivalent of 500-4000, and 1-20% by weight of an organoalkoxysilane containing C1-C4-alkoxy groups, said mixture being heated at a temperature of 100-150°C until the epoxy resin is substantially completely dissolved. To prepare the first component, the C1-C4-alcohol is subsequently evaporated at a pressure of less than 13 kPa to a C1-C4-alcohol residual content of less than 0.4% by weight to provide a second component containing a polyfunctional isocyanate having an isocyanate functionality of 1.8-4. This second component is present in a molar ratio of NCO / OH groups of 0.9:1 to 3:1 relative to the first component. Considering current food regulatory provisions, the use of epoxy resins in food packaging should be viewed critically, as at least some of the compounds pose health risks.

[0006] WO 2006 / 026670 discloses a high-temperature laminating adhesive comprising at least one polyester urethane having at least two isocyanate groups, which is obtained by reacting one or more hydroxyl-functional polyesters 1 with an aliphatic diisocyanate and one or more hydroxyl-functional polyesters 2, where the polyesters 1 have a number average molecular weight M in the range of 3000 to 7000 g / mol. n and polyester 2 has a number average molecular weight M in the range of 700 to 2000 g / mol. n The aliphatic diisocyanate has a number average molecular weight M of 110 to 300 g / mol. n and the one or more branched hydroxyl functional polyesters have a number average molecular weight M in the range of 1000 to 3500 g / mol. n has. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 5,096,980 [Patent Document 2] European Patent Application Publication No. 1983011 [Patent Document 3] International Publication No. 2006 / 026670 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] Polyurethane adhesives based on polyester polyols are commonly used in order to be able to meet the stringent requirements imposed on the mechanical properties and adhesive effect of the adhesive.However, some of the above-mentioned adhesives have the disadvantage of forming "migratory" compounds such as cyclic esters, which cannot be prevented from migrating into packaged foods.The above-mentioned migratory compounds are problematic insofar as they may be at least partially harmful to health.

[0009] It is therefore an object of the present invention to provide an adhesive composition which is free of migratory compounds of this type and which at the same time withstands the high mechanical, chemical and thermal stresses encountered in the field of food packaging. [Means for solving the problem]

[0010] Surprisingly, it has been found that this object is achieved by a polyurethane-based adhesive composition in which a polyether is used which comprises at least one urethane group per mole of polyether.The present invention therefore relates firstly to polyethers having a urethane group density of 2 to 10, preferably 3 to 7, more preferably 3 to 5 urethane groups per mole of polyether.

[0011] Within the meaning of the present invention, a urethane unit is to be understood as a repeating unit in a polymer having the chemical structure -NH-(CO)-O-. In this case, the number of urethane units can theoretically be determined using the following formula:

number

[0012] The mole fraction of this isocyanate in a 100 g batch can be used to determine the number of urethane units in the composition.

number

[0013] Surprisingly, it has been found that when the number of urethane units is within the indicated range, a polyether is obtained whose use in an adhesive composition results in a composition that achieves good adhesion that can be maintained even after long periods of storage and sterilization. In a preferred embodiment, the polyethers of the present invention are prepared by reacting a polyol with an isocyanate component.

[0014] There are no further requirements for the isocyanate component. However, it has been found to be particularly advantageous to use an aliphatic isocyanate component as the isocyanate component for preparing the polyethers of the present invention. Thus, in a preferred embodiment, the isocyanate component is selected from the group consisting of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), xylylene diisocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), pentamethylene diisocyanate (PDI), and derivatives and mixtures of the above compounds. In a particularly preferred embodiment, the isocyanate component is isophorone diisocyanate (IPDI) and / or hexamethylene diisocyanate (HDI).

[0015] In a further preferred embodiment, the polyol used to prepare the polyethers of the present invention is synthesized from monomers selected from the group consisting of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and mixtures thereof. In a preferred embodiment, the polyether is diglycol.

[0016] In a preferred embodiment, the polyether has a hydroxyl number of less than or equal to 260 mg KOH / g. In particular, preferred are embodiments in which the polyether has a hydroxyl number of 1 to 260 mg KOH / g, preferably 5 to 120 mg KOH / g, particularly preferably 10 to 50 KOH / g. Within the meaning of the present invention, the hydroxyl number (OH number) is a measure of the content of hydroxyl groups in the polyether and is specified as the amount of potassium hydroxide in milligrams that is equal to the amount of acetic acid bound during the acetylation of one gram of substance.

[0017] In a preferred embodiment, the polyethers of the present invention are obtained from a reaction mixture comprising 1 to 20 weight percent, preferably 5 to 10 weight percent, of a polyol, and 1 to 50 weight percent, preferably 20 to 40 weight percent, of an isocyanate component, the weight percentage specifications being based in each case on the total weight of the solvent-free reaction mixture.

[0018] Surprisingly, it has been found that the use of the polyethers of the invention results in adhesive compounds which are characterized by a very good adhesive effect and high hydrolysis resistance.The invention therefore further relates to the use of the polyethers of the invention in adhesive compositions.

[0019] The present invention further comprises: a) at least one polyether having a urethane group density of 2 to 10, preferably 3 to 7, more preferably 3 to 5 urethane groups per mole of polyether; and b) at least one NCO-terminated compound The present invention relates to an adhesive composition comprising:

[0020] Polyether urethanes are known to exhibit poor or no adhesion to aluminum or aluminum-containing alloys. In the context of the present invention, it has surprisingly been found that even when using different materials such as aluminum alloys, very good adhesive effects can be achieved using the adhesive composition of the present invention.

[0021] In a preferred embodiment of the adhesive composition of the present invention, the addition ratio of the at least one NCO-terminated compound to the at least one polyether, expressed as NCO:OH, is from 1.0:1 to 8.0:1, preferably from 1.1:1 to 4.0:1.

[0022] Surprisingly, it has been found that the adhesive composition of the present invention can be used to obtain composite systems without the use of polyester polyols, which are normally achieved by using only polyester polyols.A preferred embodiment is therefore a composite system in which the adhesive composition of the present invention does not contain polyester polyols.In a particularly preferred embodiment, the proportion of polyester polyols in the adhesive composition of the present invention is less than 0.1% by weight, preferably less than 0.01% by weight, in each case based on the total weight of the solvent-free adhesive composition.

[0023] In order to be suitable for use as an adhesive in the field of food packaging, the compositions used must contain as few components as possible that are potentially harmful to health. When using conventional compositions, there is a risk that residues of isocyanate monomers remain in the cured adhesive composition, some of these monomers being considered harmful to health. In the adhesive composition of the invention, the presence of monomeric isocyanates is not permitted. A preferred embodiment is therefore an adhesive composition in which the content of monomeric NCO-terminated compounds is in each case less than 10.0% by weight, preferably 0.01-1% by weight, more preferably 0.01-0.1% by weight, particularly preferably less than 0.1% by weight, based on the total weight of said adhesive. Furthermore, when cured, the adhesive composition of the invention has a content of monomeric NCO compounds in each case less than 1% by weight, preferably less than 0.01% by weight, based on the total weight of the cured adhesive composition.

[0024] In a preferred embodiment, the content of the at least one polyether in the adhesive composition of the invention is from 1 to 40% by weight, preferably from 2 to 15% by weight, in each case based on the total weight of the solvent-free adhesive composition.

[0025] According to a preferred embodiment of the invention, the proportion of the at least one NCO-terminated compound in the adhesive composition according to the invention is in each case 1 to 50% by weight, preferably 20 to 40% by weight, based on the total weight of the solvent-free adhesive composition.

[0026] The NCO-terminated compound is preferably a polyisocyanate. The polyisocyanate is an aromatic, aliphatic, or cycloaliphatic isocyanate. The polyisocyanate is preferably 1,5-naphthyl diisocyanate, 2,4- or 4,4'-diphenylmethane diisocyanate (MDI) and mixtures of said isomers, hydrated MDI (H12MDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), tetraalkylene diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3- or 1,4-phenylene diisocyanate, isomers of toluene diisocyanate (TDI), 1-methyl-2,4-diisocyanate-cyclohexane, 1,6-diisocyanate-2,2,4-trimethylhexane, 1,6-diisocyanate-cyclohexane, ... The diisocyanate is selected from the group consisting of isocyanate-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), phosphorus- or halogen-containing diisocyanates, tetramethoxybutane 1,4-diisocyanate, butane 1,4-diisocyanate, 1,6-hexane diisocyanate (HDI), dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, ethylene diisocyanate, methylene triphenyl triisocyanate (MIT), 1,4-diisocyanatobutane, 1,12-diisocyanatododecane and dimeric fatty acid diisocyanates. Polyfunctional isocyanates can also be used as a result of trimerization or oligomerization of the diisocyanate or by reacting the diisocyanate with a polyfunctional hydroxyl or amino group-containing compound. Diisocyanates and their oligomers are preferably used.

[0027] In a particularly preferred embodiment, the NCO-terminated compound is selected from the group consisting of xylylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), as well as polymers and oligomers of said compounds, and derivatives and mixtures of said compounds.

[0028] The adhesive composition of the invention preferably further comprises an adhesion promoter, which is preferably present in an amount of up to 20% by weight, particularly preferably 1 to 10% by weight, in each case based on the total weight of the composition without solvent. The adhesion promoter is preferably selected from alkoxylated silanes and their organofunctional derivatives. Particularly preferably, the adhesion promoter is selected from methoxylated and ethoxylated silanes and mixtures thereof. Surprisingly, it has been found that by adding selected adhesives, adhesive compositions with high adhesion can be achieved even in the presence of fillers in high-demand food packaging.

[0029] The adhesive composition of the present invention is characterized by the absence of migratory cyclic compounds and is therefore particularly suitable for the production of packaging in the food industry. Preferably, the adhesive composition of the present invention is substantially free of critical migration rings. In a further preferred embodiment, the content of critical migration rings in the adhesive composition of the present invention is less than 1% by weight, preferably less than 0.1% by weight, particularly preferably less than 0.01% by weight, in each case based on the total weight of the solvent-free adhesive composition or the total weight of the cured adhesive composition. In a particularly preferred embodiment, the adhesive composition of the present invention is free of critical migration rings, even after curing.

[0030] The adhesive composition of the present invention can be used as both a one-component (1K) system and a two-component (2K) system. Thus, in a preferred embodiment, the adhesive composition of the present invention is a 2K system. In an alternative preferred embodiment, the adhesive composition of the present invention is a 1K system.

[0031] The adhesive composition of the present invention is particularly suitable for adhesively bonding foil-like substrates in the field of food packaging.A preferred embodiment is therefore one in which the adhesive composition of the present invention is a laminating adhesive.In this case, the adhesive composition can be provided with or without a solvent or in the form of a dispersion.

[0032] In a preferred embodiment, the adhesive composition of the invention may further comprise a catalyst, preferably in an amount of 0 to 10% by weight, particularly preferably 0.5 to 3% by weight, in each case based on the total weight of the solvent-free adhesive composition. In a further preferred embodiment, the adhesive composition of the invention does not comprise a metal compound. Metal compounds are often used as catalysts in conventional systems, but in the field of food packaging they should be avoided due to health concerns associated with these compounds. A preferred embodiment is therefore that the catalyst, if present, is an amine compound, preferably one having at least OH functionality. In this case suitable compounds are, for example, dimethylaminoethanol (DMEA), 2-(diethylamino)ethanol (2-DEEA) or derivatives of the above compounds, N-methylaminoethanol or methyldiethanol.

[0033] The present invention further relates to a method for adhesively bonding substrates using the adhesive composition of the present invention, in which the method of the present invention comprises: i) applying the adhesive composition of the present invention to at least one substrate; ii) contacting the coated substrate with another substrate; iii) curing the applied adhesive composition; and Including, The adhesive composition is cured at a temperature of 40 to 85°C, preferably 55 to 65°C.

[0034] In a preferred embodiment, the substrates are contacted under additional pressure.

[0035] The adhesive composition of the present invention is particularly suitable for adhesively bonding flexible substrates. In this case, within the context of the present application, a flexible substrate should be understood as a substrate having a certain degree of elasticity and flexibility, such as a foil, a sheet or a plate. In a preferred embodiment, the substrate is a substrate such as a foil, in particular a plastic or metal foil. In an alternative embodiment, the substrate is a plastic or metal sheet, in particular an aluminum sheet.

[0036] Adhesive bonding of flexible substrates is a routine matter for the skilled person and is a long-established method. However, adhesive bonding of thick flexible substrates, in particular thick metal foils such as aluminum foils, remains difficult. However, these are precisely the materials used in the field of food packaging. Within the context of the present invention, it has surprisingly been found that the method of the present invention, in combination with the adhesive composition of the present invention, is suitable for adhesive bonding of thick metal foils, in particular those used in the manufacture of wet food packaging. Thus, a preferred embodiment is a method in which at least one substrate is an aluminum foil, preferably having a thickness of 5 to 240 μm, particularly preferably 40 to 180 μm. In a preferred embodiment, the aluminum foil may furthermore be a foil made of an aluminum alloy.

[0037] The present invention further relates to a composite system which comprises the adhesive composition of the present invention or which is obtainable by the process of the present invention.

[0038] The composite system of the invention is characterized by a high adhesive strength even after curing of the adhesive composition and after sterilization.A preferred embodiment is therefore one in which the composite system has an adhesive strength of 3 to 19 N / 15 mm, preferably 5 to 15 N / 15 mm, particularly preferably 5 to 10 N / 15 mm after 7 days and sterilization at 131° C. for 45 minutes.

[0039] The composite system is preferably a package, in particular a package for human or animal food, in particular a package for animal food.Surprisingly, it has been found that the composite system of the present invention can be used as an animal food package, which places strict requirements on the system used for aggressive contents.The present invention further relates to the use of the adhesive composition of the present invention for producing a package, preferably a food package for human or animal, in particular a package for animal food, most particularly a package for wet animal food.

[0040] The present invention further relates to the use of the adhesive composition according to the invention for adhesively bonding foil-like substrates, at least one substrate to be adhesively bonded being preferably an aluminum foil, preferably having a thickness of 5 to 240 μm, particularly preferably 40 to 180 μm.

[0041] The present invention will now be described in more detail with reference to the following examples, which are not intended to be considered as limiting the concept of the present invention. EXAMPLES

[0042] Examples of polyethers of the invention were prepared from a reaction mixture containing PPG 400, PPG 1100, isophorone diisocyanate and ethylene glycol (Example 1). The polyether of the invention of Example 2 was obtained from a reaction mixture further containing 2-(diethylamino)ethanol as a catalyst. PPG 400 is a polypropylene glycol having a molecular weight of 400 g / mol and is commercially available from Dow under the trade name Voranol P 400. PPG 1000 is a polypropylene glycol having a molecular weight of 1,000 g / mol and is commercially available from Dow under the trade name Voranol P1000. Isophorone diisocyanate is commercially available from Covestro under the trade name Desmodur I. Ethylene glycol is commercially available, for example, from Dow. Both polyethers of Examples 1 and 2 have a urethane group density of 3.35 urethane groups per mole of polyether and a hydroxyl number of 21 mg KOH / g.

[0043] The polyethers were in each case reacted with NCO-terminated compounds to form laminating adhesives. For this purpose, a film-forming add-on ratio NCO / OH of 2.0 was selected. The resulting reactive adhesive mixture was diluted with ethyl acetate to a solids content of 33.3%.

[0044] The substrate to be coated was formatted in A4 size. The carrier foil, made of aluminum, was 18 g / m 2The carrier foil thus coated was then dried in a drying cabinet at 90° C. for 5 minutes and coated with a 6 g / m2 reactive adhesive mixture. 2 The composite system thus prepared was cured at 60° C. under pressure (weight 8 kg) between metal plates in a drying cabinet.

[0045] The prepared laminates were tested for their utility: for this purpose, a tension test was carried out and the laminates were sterilized.

[0046] The results are summarized in Tables 1 to 3. A mixture of IPDI trimer, IPDI, and methoxysilane was used as the NCO-terminated compound.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] As can be seen from the data in the above table, the adhesive compositions of the present invention can be used to prepare composite systems that maintain their adhesive strength even after sterilization and when stored in the presence of aggressive fillers.

[0051] This application is a divisional application based on Japanese Patent Application No. 2018-094877, and includes all of the contents described in the specification of that original application, including at least the following preferred aspects. [1] A polyether having a urethane group density of 2 to 10 urethane groups per mole of polyether. [2] The polyether according to [1], characterized in that the polyether is prepared by reacting a polyol with an isocyanate component. [3] The polyether according to either or both of [1] and [2], characterized in that the isocyanate component is selected from the group consisting of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), pentamethylene diisocyanate (PDI), and derivatives and mixtures of these compounds. [4] The polyether according to one or more of [1] to [3], characterized in that the polyol is synthesized from a monomer selected from the group consisting of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and a mixture thereof. [5] Use of the polyether according to one or more of [1] to [4] in an adhesive composition, preferably a 2K adhesive composition. [6] a) at least one polyether according to one or more of [1] to [4], and b) at least one NCO-terminated compound 1. An adhesive composition comprising: [7] The adhesive composition according to [6], characterized in that the addition ratio of the at least one NCO-terminated compound to the at least one polyether, expressed as NCO:OH, is from 1.0:1 to 8.0:1, preferably from 1.1:1 to 4.0:1. [8] The adhesive composition according to at least one of [1] to [7], characterized in that the content of monomeric NCO-terminated compounds is in any case less than 10.0 wt. %, preferably 0.01 to 1 wt. %, more preferably 0.01 to 0.1 wt. %, and particularly preferably less than 0.1 wt. %, based on the total weight of the adhesive. [9] The adhesive composition according to at least one of [1] to [8], characterized in that the adhesive is substantially free of a critical migration cyclic ester.

[10] i) applying the adhesive composition according to at least one of [1] to [9] to at least one substrate; ii) contacting the coated substrate with a further substrate; iii) curing the polyurethane adhesive; 1. A method for adhesively bonding at least two substrates comprising: 4. The method according to claim 1, wherein the adhesive is cured at a temperature of 40 to 85°C, preferably 55 to 65°C.

[11] The method according to

[10] , wherein the substrate is a foil-like substrate.

[12] The method according to

[10] or

[11] , wherein the at least one substrate is an aluminum foil having a thickness of preferably 5 to 240 μm, particularly preferably 40 to 180 μm.

[13] A composite system comprising the polyurethane adhesive according to at least one of [1] to [9] or obtained according to the method according to any one of claims 10 to 12.

[14] Use of the adhesive composition according to at least one of [1] to [9] for producing packaging, preferably food packaging, in particular packaging for animal food and human food.

[15] Use of the adhesive composition according to at least one of [1] to [9] for adhesively bonding foil-like substrates.

Claims

1. a) at least one polyether having a urethane group density of from 2 to 10 urethane groups per mole of polyether; and b) at least one NCO-terminated compound An adhesive composition for food packaging comprising: The polyethers are prepared by reacting a polyol with an aliphatic isocyanate component selected from the group consisting of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), pentamethylene diisocyanate (PDI), and derivatives and mixtures of these compounds; the NCO-terminated compound is selected from the group consisting of pentamethylene diisocyanate, hexamethylene diisocyanate, 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), and polymers and oligomers of the foregoing compounds, and derivatives and mixtures of the foregoing compounds; The urethane group density of polyether is given by the following formula: [Formula 1] [Formula 2] [The above formula is used to calculate the mole fraction of isocyanate in a 100g batch, and the below formula is used to calculate the number of urethane units] The adhesive composition according to claim 1,

2. 2. The adhesive composition of claim 1, wherein the polyol is synthesized from monomers selected from the group consisting of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and mixtures thereof.

3. The adhesive composition according to any one of claims 1 to 2, which is a 2K adhesive composition.

4. 4. The adhesive composition according to claim 1, wherein the addition ratio of the at least one NCO-terminated compound to the at least one polyether, expressed as NCO:OH, is from 1.0:1 to 8.0:

1.

5. The adhesive composition of claim 4, wherein the add-on ratio is from 1.1:1 to 4.0:

1.

6. 6. The adhesive composition according to claim 1, wherein the adhesive has a content of monomeric NCO-terminated compounds of less than 10.0 wt. %, based on the total weight of the adhesive.

7. 7. The adhesive composition according to claim 6, wherein the content of monomeric NCO-terminated compounds is 0.01 to 1 wt. %, based on the total weight of the adhesive.

8. 7. The adhesive composition of claim 6, wherein the content of monomeric NCO-terminated compounds is less than 0.1 wt. %, based on the total weight of the adhesive.

9. 9. The adhesive composition according to claim 1, wherein the adhesive is substantially free of a critical migration cyclic ester.

10. The adhesive composition of claim 1, wherein the at least one polyether is at least one polyether having a urethane group density of 3 to 7 urethane groups per mole of polyether.

11. i) applying an adhesive composition according to any one of claims 1 to 10 to at least one substrate; ii) contacting the coated substrate with a further substrate; iii) curing the adhesive composition; and 1. A method for adhesively bonding at least two substrates comprising: The method according to claim 1, wherein the adhesive is cured at a temperature of 40 to 85°C.

12. The method of claim 11 , wherein the substrate is a foil-like substrate.

13. The method according to claim 11 or 12, characterized in that the at least one substrate is an aluminum foil having a thickness of 5 to 240 μm.

14. A composite system comprising the adhesive composition according to any one of claims 1 to 10.

15. Use of the adhesive composition according to any one of claims 1 to 10 for producing packaging.

16. Use of an adhesive composition according to any one of claims 1 to 10 for adhesively bonding foil-like substrates.

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