Enzyme mediated delamination on demand of multilayer packaging materials

Abstract

A laminate is described comprising at least two substrate layers of different materials bonded together by an adhesive layer comprising one or more enzymes capable of degrading polyester-polyurethanes. The laminate can be delaminated by contacting with a delamination liquid at delamination conditions.

Description

[0001] 240732

[0002] 1

[0003] Enzyme mediated delamination on demand of multilayer packaging materials

[0004] The invention relates to multilayer laminates comprising at least two substrate layers of different materials bonded together by an adhesive layer comprising one or more enzymes. The invention also relates to a method of delamination wherein the laminate is delaminated by contacting with a delamination liquid at delamination conditions.

[0005] Multilayer flexible packaging materials are materials in which two or more different substrates are combined in a layered structure. Multilayer flexible packaging is widely used in different sectors such as food, agriculture or cosmetics. These materials show many advantages in terms of barrier properties (light, oxygen, humidity, aroma). Multilayer packaging is produced with different substrate materials such as aluminum foil and different polymeric materials, such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene such as oriented polypropylene (oPP) or cast polypropylene (cPP). For example, a conventional coffee package usually has a laminate structure consisting of PE, PET, aluminum foil and outer polyester such as PET. Around 25.8 million tons of plastic waste is produced in Europe each year, 59% of which is plastic packaging. Multilayer flexible packaging represents the largest proportion of non-recyclable packaging, accounting for around 20% of all packaging. Multilayer packaging materials are often considered non-recyclable. It is desirable to increase its recyclability. One solution to increase its recyclability would be the delamination (or debonding) of its different material layers, so that the individual layers can be further processed according to type. Usually, these materials are joined together by lamination or co-extrusion. Often an extrudable or coated adhesive is applied between materials. In particular, the separation of the polymeric fraction from aluminum foil in composite packaging still remains a big challenge for the circular economy. The recycling of multilayer packaging materials involves usually a step of debonding of the different material layers, in which the adhesive layer is somehow weekend to allow material separation. Typical debonding process is run in an aqueous NaOH bath (>1 molar) at ca. 80°C. This condition is not favorable for some types of materials. For example, aluminum can be damaged in alkaline conditions, making it difficult to further recycle efficiently and the high temperatures lead to high energy consumption.

[0006] Thus, an increasing demand for sustainable solutions is currently observed in the packaging industry. Plastic products like flexible packaging shall be recyclable. There is a high demand for recyclable multi-layer packaging, where the layers can be separated from each other and recycled. The major challenge consists in providing adhesive materials which have the necessary functionality and stability during their lifetime but which when subject to a suitable stimulation can be triggered to be delaminated in short time to a high extent. It is extremely difficult to achieve simultaneous compliance with, and optimization of, these fundamentally contradictory requirements of stability and sufficient adhesive bond strength of the adhesive before and during use and ease of delamination on demand after use.

[0007] WO 2022 / 135987 and WO 2022 / 135988 describe enzymatic degrading of polyurethane materials using a combination of cutinases and esterases or a combination of cutinases and lipases, respectively. The polyurethane 240732

[0008] 2 materials are incubated in an aqueous solution containing the enzymes. The incubation times ranges from 3 days up to 20 days.

[0009] Therefore, a problem to be solved was providing further materials for lamination adhesives and for producing multilayer laminates useful for flexible packaging. These lamination adhesives should be water based with high stability, can be easily produced, provide sufficient lamination bond strength for storage-stable multi-layer laminates, while simultaneously providing rapid delamination at demand under delamination conditions without damaging the substrate layer materials during delamination. Circular demands could be met in this way and the recovery of fossil-based materials in flexible packaging could be maximized.

[0010] It has been found that the problem can be solved by the laminates and the method of delamination as described below.

[0011] This invention is about a laminate and a method of delamination in which the delamination is triggered by enzymes which are present within the adhesive layer (preferably based on polyester-polyurethane, more preferably on aqueous polyurethane dispersion), when the laminate is contact with water under delamination conditions. The delamination method can be carried out in pure water at neutral pH and elevated temperatures. Although active enzymes involved in microbial degradation of polyester-polyurethanes can be esterases suggesting the degradation of the polyurethane material by the cleavage of the ester bond, it was surprisingly found that theses enzymes can be embedded in an adhesive polyester-polyurethane lamination adhesive wherein laminates made thereof are storage stable. When these are used to produce multi-layer laminates of different substrate materials, a positive effect on delamination can be observed at mild delamination conditions. The laminates produced with enzymes formulated in adhesive layer are storage stable, i.e. the desired adhesive conditions are maintained during ordinary use until delamination is triggered on demand.

[0012] The invention provides a laminate comprising at least two substrate layers of different materials bonded together by an adhesive layer, wherein the adhesive layer comprises at least one adhesive polyester-polyurethane and one or more enzymes capable of degrading polyester-polyurethanes. Preferred enzymes are hydrolases of Enzyme Commission number EC 3. More preferred are enzymes of EC 3.1, i.e. hydrolases acting on ester bonds (esterases), enzymes of EC 3.4, i.e. peptidases (acting on peptide bonds) and enzymes of EC 3.5, i.e. enzymes acting on carbon-nitrogen bonds other than peptide bonds. Preferred are cutinases, proteases and ureases. The adhesive layer preferably does not comprise lipase.

[0013] The invention also provides the use of an aqueous polyurethane dispersion adhesive comprising at least one polyester-polyurethane as defined herein and at least one enzyme capable of degrading polyester-polyurethanes, preferably selected from cutinases, proteases and ureases for making a multilayer packaging material comprising at least two polymeric layers or a polymeric layer and an aluminum layer, wherein the multilayer packaging material can be delaminated to at least 50%, preferably to at least 60 %, by an aqueous composition at pH from 6 to 8 at 240732

[0014] 3 temperatures from 60 to less than 80 °C within 30 to 120 minutes. Typically, the extent of delamination is measured according to the debonding test method described in the examples and typically refers to the debonded parts (wt.%) = (weight of debonded parts of the laminate I total weight of parts of laminate tested) * 100.

[0015] The terms "aqueous composition” and "aqueous polyurethane dispersion” refers to solvent systems primarily based on water, preferably containing no or less than 20%, less than 10%, less than 5%, less than 3% or less than 1% by weight of organic solvents (such as for example methanol, ethanol or tetrahydrofuran), based on the total composition. It is preferred not to use organic solvents.

[0016] Typicall, a lamination adhesive composition or the adhesive polyester-polyurethane is an adhesive suitable for use in lamination processes, the lamination adhesive or the adhesive polyester-polyurethane is preferably non-self- adhesive. Non-self-adhesive adhesives are adhesives that, unlike pressure-sensitive adhesives, have little or no stickiness at room temperature and are preferably applied with pressure and / or elevated temperature. The stickiness measured as a loop tack is preferably less than 1 .7 N / 25 mm (adhesive with an application thickness of 20 pm applied to a 12 pm thick polyester film, measured on steel at room temperature (20 °C) with a removal speed of 300 mm / min).

[0017] The lamination adhesive (or preferably the adhesive layer formed by the lamination adhesive) according to the invention preferably has an adhesive bond strength such that the peel adhesion strength of an aluminumpolyethylene laminate is at least 0.5 N / 15 mm at 23°C, more preferably at least 1.0 N / 15 mm at 23°C, more preferably at least 2.0 N / 15 mm at 23°C and after 24 hours storage at 23°C.

[0018] A lamination adhesive polymer is a polymer with a glass transition temperature preferably less than 20°C, more preferably in the range of -45°C to +15°C, more preferably from -35°C to +10°C or from -10 to +10 °C. By a controlled variation of the nature and amount of the monomers it is possible for the skilled person to prepare adhesive polymer compositions whose polymers have a glass transition temperature within the desired range. The glass transition temperature is determined by differential scanning calorimetry (ASTM D 3418-08, midpoint temperature). The glass transition temperature of the polymer is the glass transition temperature obtained on evaluation of the second heating curve (heating rate 20 K / min).

[0019] A preferred laminate is a laminate, wherein the adhesive layer is formed from an aqueous polyurethane dispersion adhesive, where the polyurethane, which is preferably a polyester-polyurethane, is composed of

[0020] (a) at least one diisocyanate;

[0021] (b) one or more dihydroxy compounds, wherein at least one of the dihydroxy compounds is a polyesterdiol;

[0022] (c) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, wherein the compounds c) preferably contain a group selected from carboxylate groups and sulfonate groups; and

[0023] (d) optionally further compounds different from a) to c). 240732

[0024] 4

[0025] The adhesive to be used in the invention contains (preferably consists essentially of) at least one polyesterpolyurethane dispersed in water as polymeric binder, and optionally of added substances, such as fillers, thickeners, antifoam, etc. The polymeric binder preferably takes the form of dispersion in water or else in a mixture made of water and of water-soluble organic solvents with boiling points which are preferably below 150°C (1 bar). Particular preference is given to water as sole solvent. The water or other solvents are not included in the calculation of weight data relating to the constitution of the adhesive. In the following "polyester-polyurethane” is also abbreviated as "polyurethane”.

[0026] The polyurethanes are preferably mainly composed of aliphatic polyisocyanates, in particular diisocyanates, on the one hand, and on the other hand of reactants which are preferably amorphous, non-crystalline polyesterdiols, and also bifunctional carboxylic acids. It is preferable that the polyurethane is composed of at least 60% by weight, and very particularly at least 80% by weight, of diisocyanates, polyesterdiols, and bifunctional carboxylic acids. The polyurethane is preferably amorphous. It is preferable that the polyurethane comprises an amount of more than 10% by weight, more than 50% by weight, or at least 80% by weight, based on the polyurethane, of aliphatic polyesterdiols.

[0027] Aqueous adhesive polyester-polyurethane dispersions

[0028] The polyurethane adhesive polymers are obtainable by polycondensation of polyisocyanates and polyols. Suitable polyurethane dispersions are in principle obtainable by reaction of at least one polyisocyanate with at least one compound having at least two isocyanate-reactive groups and dispersion in water. Suitable polyurethanes also include so-called polyurethane-polyureas comprising not only polyurethane groups but also urea groups. The polyurethane dispersion preferably comprises at least one polyurethane which comprises at least one polyisocyanate and at least one polymeric polyol in copolymerized form. The polyurethane may in particular be formed from at least one polyisocyanate and at least one polymeric polyester polyol.

[0029] The polyurethane (preferably the polyurethane of the aqueous polyurethane dispersion adhesive) is preferably composed of: a) at least one diisocyanate, which preferably is aliphatic or cycloaliphatic, b) at least one diol, where, of these, b1) from 10 to 100 mol%, based on the total amount of the diols (b), are polyesterdiols with a molar mass of from 500 to 5000 g / mol, b2) from 0 to 90 mol%, based on the total amount of the diols (b), have a molar mass of from 60 to 500 g / mol, c) at least one bifunctional carboxylic acid selected from dihydroxycarboxylic acids and diaminocarboxylic acids, d) optionally further compounds different from a) to c) selected from

[0030] (d1) monomers having at least two reactive groups selected from alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups; and 240732

[0031] 5

[0032] (d2) monofunctional compounds having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group; wherein the ratio of isocyanate groups to groups reactive with isocyanates is 0.5:1 to 2:1, preferably from 0.8:1 to 1.5:1, more preferably from 0.9:1 to 1.2:1 when making the polyurethane.

[0033] The molar mass is the number-average molar mass Mn. Mn is calculated by determining the number of terminal groups (OH number).

[0034] The polyurethane (preferably the polyurethane of the aqueous polyurethane dispersion adhesive) is preferably composed of a) at least one monomeric diisocyanate, selected from diisocyanates of the formula X(NCO)2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, an aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms, wherein the amount of aromatic diisocyanates is less than 60 mol%, based on the sum of all organic diisocyanates a), and more preferably the at least one monomeric diisocyanate is aliphatic or cycloaliphatic, b) one or more dihydroxy compounds, where, of these, b1) from 10 to 100 mol%, based on the total amount of the dihydroxy compounds (b), are polyesterdiols with a number-average molecular weight from more than 500 and up to 5000 g / mol, and b2) from 0 to 90 mol%, based on the total amount of the dihydroxy compounds (b), have a molar mass of from 60 to 500 g / mol, and preferably at least 80% by weight of the polyurethane is composed of at least one aliphatic polyesterdiol (b1);

[0035] (c) at least one bifunctional carboxylic acid selected from dihydroxy carboxylic acids and diamino carboxylic acids; and

[0036] (d) optionally further compounds different from a) to c) selected from

[0037] (d1) monomers having at least two reactive groups selected from alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups; and

[0038] (d2) monofunctional compounds having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group; wherein the ratio of isocyanate groups to groups reactive with isocyanates is 0.5:1 to 2:1, preferably from 0.8:1 to 1.5:1, more preferably from 0.9:1 to 1.2:1 when making the polyurethane; wherein the polyurethane is preferably made at least in part of bio-based or recycled materials.

[0039] Also preferred is a polyurethane which is composed of at least 60% by weight of

[0040] (a) at least one aliphatic diisocyanate,

[0041] (b) at least one aliphatic polyesterdiol, 240732

[0042] 6

[0043] (c) at least one bifunctional carboxylic acid selected from dihydroxycarboxylic acids and diaminocarboxylic acids, and

[0044] (d) at least one polyfunctional compound which differs from the monomers (a) to (c), and which has at least two reactive groups selected from primary and secondary amino groups.

[0045] Preferably, at least 80% by weight of the at least one polyesterdiol (b) is composed of at least one aliphatic dicarboxylic acid and of at least one aliphatic diol.

[0046] Suitable monomers (a) are diisocyanates X(NCO)2, where X is an aliphatic hydrocarbon radical having from 4 to 15 carbon atoms or a cycloaliphatic or aromatic hydrocarbon radical having from 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having from 7 to 15 carbon atoms, wherein the aliphatic and / or cycloaliphatic diisocyanates are preferred. Examples of these diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,5,5-trimethyl-3-isocyanatomethylcyclohexane (IPDI), 2,2-bis(4-isocyanatocyclohexyl)propane, trimethylhexane diisocyanate, the isomers of bis(4-isocyanate- cyclohexyl)methane (HMDI), e.g. the trans / trans, the cis / cis, and the cis / trans isomers, and also mixtures composed of said compounds. Examples of aromatic diisocyanates are 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6- diisocyanatotoluene, 4,4'-diisocyanatodiphenylmethane, 2,4'-diisocyanatodiphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI). Diisocyanates of this type are available commercially.

[0047] Mixtures of said isocyanates are for example the mixtures of the respective structural isomers of diisocyanatotoluene and diisocyanatodiphenylmethane, e.g. a mixture made of 80 mol% of 2,4-diisocyanatotoluene and 20 mol% of 2,6- diisocyanatotoluene; or mixtures of aromatic isocyanates such as 2,4-diisocyanatotoluene and / or 2,6- diisocyanatotoluene with aliphatic or cycloaliphatic isocyanates such as hexamethylene diisocyanate or IPDI, where the preferred mixing ratio of the aliphatic to aromatic isocyanates is from 4: 1 to 1 :4.

[0048] Most preferred is hexamethylene diisocyanate.

[0049] Other than the abovementioned compounds, other compounds that can be used in the structure of the polyurethanes are those which have, alongside the free isocyanate groups, other capped isocyanate groups, e.g. uretdione groups.

[0050] With a view to good film-formation and elasticity, diols (b) that can be used are mainly relatively high-molecular- weight diols (b1) which have a molar mass of about 500 to 5000 g / mol, preferably about 1000 to 3000 g / mol. This is the number-average molar mass Mn. Mn is calculated by determining the number of terminal groups (OH number).

[0051] The diols (b1) can be polyester polyols, where these are known by way of example from Ullmanns Enzyklopadie der technischen Chemie [Ullmann's encyclopedia of industrial chemistry], 4thedition, volume 19, pp. 62 to 65. It is preferable to use polyester polyols which are obtained via reaction of difunctional alcohols with difunctional carboxylic acids. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols, or a mixture of these, to produce the polyester polyols. The 240732

[0052] 7 polycarboxylic acids can be aliphatic, cycloaliphatic, araliphatic, aromatic, or heterocyclic, and can optionally have unsaturation and / or substitution, e.g. by halogen atoms. Examples that may be mentioned of these are: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, and dimeric fatty acids. Preference is given to dicarboxylic acids of the general formula HOOC-(CH2)y-COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, examples being succinic acid, adipic acid, sebacic acid, and dodecane dicarboxylic acid.

[0053] Examples of polyfunctional alcohols that can be used are ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane- 1 ,3-diol, butene-1,4-diol, butyne-1 ,4-diol, pentane-1,5-diol, neopentyl glycol, bis(hydroxymethyl)cyclohexanes, such as 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1, 3-diol, methylpentanediols (for example 3-methyl pentanediol), hydroxypivalic acid neopentyl glycolester (3-hydroxy-2,2-dimethylpropy I 3-hydroxy-2,2-dimethyl- propanoate) and also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutylene glycols. Preference is given to alcohols of the general formula HO-(CH2)X-OH, where x is a number from 1 to 20, preferably an even number from 2 to 20, in mixture with branched aliphatic diols, especially neopentyl glycol, wherein the amount of branched aliphatic diols is preferably at least 10 mol%, at least 25 mol% or at least 30 mol% of the total amount of diols.

[0054] It is optionally also possible to use polycarbonatediols as by way of example are obtainable via reaction of phosgene with an excess of the low-molecular-weight alcohols mentioned as structural components for the polyester polyols.

[0055] It is also possible to use lactone-based polyesterdiols, alone or in combination with the abovementioned polyesterdiols, where these are homo- or copolymers of lactones, preferably adducts which have terminal hydroxy groups and which are produced by addition reactions of lactones onto suitable difunctional starter molecules. Preferred lactones that can be used are those deriving from compounds of the general formula HO-(CH2)Z-COOH, where z is a number from 1 to 20 and an H atom of a methylene unit can also have been replaced by a Ci-C4-alkyl radical. Examples are epsilon-caprolactone, B-propiolactone, gamma-butyrolactone, and / or methyl-epsilon- caprolactone, and also mixtures of these. Examples of suitable starter components are the low-molecular-weight difunctional alcohols mentioned above as structural component for the polyester polyols. Particular preference is given to the corresponding polymers of epsilon-caprolactone. Lower polyesterdiols or polyetherdiols can also be used as starters for producing the lactone polymers. Instead of the polymers of lactones, it is also possible to use the corresponding, chemically equivalent polycondensates of the hydroxycarboxylic acids that correspond to the lactones.

[0056] In addition to the polyesterdiols, it is also optionally possible to make concomitant use of polyetherdiols. Polyetherdiols are in particular obtainable via polymerization of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide, or epichlorohydrin with themselves, e.g. in the presence of BF3, or via an addition reaction of said compounds, optionally in a mixture or in succession, onto starter components having reactive 240732

[0057] 8 hydrogen atoms, e.g. alcohols or amines, examples being water, ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, 2,2-bis(4-hydroxyphenyl)propane, or aniline. Examples of polyetherdiols are polypropylene oxide and polytetrahydrofuran with molar mass from 240 to 5000 g / mol, and especially from 500 to 4500 g / mol. However, it is preferable that no polyetherdiols are used as structural component for the polyurethanes.

[0058] It is also optionally possible to make concomitant use of polyhydroxyolefins, preferably those having 2 terminal hydroxy groups, e.g. a,co-dihydroxypolybutadiene, a, co- dihydroxypolymethacrylate, or a, co- dihydroxypolyacrylate. Other suitable polyols are polyacetals, polysiloxanes, and alkyd resins.

[0059] It is preferable that at least 95 mol% or 100 mol% of the diols bi) are polyesterdiols. It is particularly preferable that diols bi) used comprise exclusively polyesterdiols. The polyesterdiols preferably consist of only aliphatic and / or cycloaliphatic components.

[0060] Preferably, the polyurethane is made of at least 50% by weight, more preferably of at least 85% by weight or of at least 95% by weight or of 100% by weight, based on all polyhydroxy compounds, of polyesterdiols.

[0061] The hardness and the modulus of elasticity of the polyurethanes can be increased if diols (b) used also comprise, alongside the diols (bi), low-molar-mass diols (b2) with molar mass about 60 to 500 g / mol, preferably from 62 to 200 g / mol. Monomers (b2) used are especially the structural components of the short-chain alkanediols mentioned for the production of polyester polyols, where preference is given to the unbranched diols having from 2 to 12 carbon atoms and having an even number of carbon atoms, and also pentane-1,5-diol and neopentyl glycol.

[0062] Examples of diols bg that can be used are ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, butane-1, 3-diol, butene-1 ,4-diol, butyne-1 ,4-diol, pentane-1 ,5-diol, neopentyl glycol, bis(hydroxymethyl)cyclohexanes, such as 1,4- bis(hydroxymethyl)cyclohexane, 2-methylpropane-1, 3-diol, methylpentanediols, and also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutylene glycols. Preference is given to alcohols of the general formula HO-(CH2)X-OH, where x is a number from 1 to 20, preferably an even number from 2 to 20. Examples here are ethylene glycol, butane-1, 4-diol, hexane-1 ,6-diol, octane-1, 8-diol, and dodecane-1 , 12-diol. Preference is further given to neopentyl glycol.

[0063] It is preferable that the proportion of the diols (bi), based on the total amount of the diols (b), is from 10 to 100 mol% or from 60 to 100 mol%, and that the proportion of the monomers (62), based on the total amount of the diols (b), is from 0 to 90 mol%, or from 0 to 40 mol%.

[0064] In order to achieve the water-dispersibility of the polyurethanes and to improve biodegradability, the polyurethanes comprise at least one bifunctional carboxylic acid (c) selected from dihydroxycarboxylic acids and diaminocarboxylic acids. It is optionally also possible to make additional use of hydrophilic structural components which promote dispersibility and which bear at least one isocyanate group or at least one group reactive toward isocyanate groups, 240732

[0065] 9 and moreover at least one hydrophilic group, or one group which can be converted to a hydrophilic group. In the text hereinafter, the "hydrophilic groups or potentially hydrophilic groups” is abbreviated to "(potentially) hydrophilic groups”. When compared with the functional groups of the monomers that are used to construct the main chain of the polymer, the (potentially) hydrophilic groups are substantially slower to react with isocyanates.

[0066] The proportion of the components having (potentially) hydrophilic groups, based on the total amount of components (a) to (d), is generally judged in such a way that the molar amount of the (potentially) hydrophilic groups, based on the total amount of all of the monomers (a) to (d), is from 30 to 1000 mmol / kg, preferably from 50 to 500 mmol / kg, and particularly preferably from 80 to 300 mmol / kg. The (potentially) hydrophilic groups can be nonionic or preferably (potentially) ionic hydrophilic groups. Particular nonionic hydrophilic groups that can be used are in the form of polyethylene glycol ethers preferably made of from 5 to 100 repeat ethylene oxide units, with preference from 10 to 80 repeat ethylene oxide units. The content of polyethylene oxide units is generally from 0 to 10% by weight, preferably from 0 to 6% by weight, based on the total amount of all of the monomers (a) to (d). Examples of monomers having nonionic hydrophilic groups are polyethylene oxide diols using at least 20% by weight of ethylene oxide, polyethylene oxide monools, and also the reaction products of a polyethylene glycol and of a diisocyanate, where these bear an etherified terminal polyethylene glycol radical. Diisocyanates of this type, and also processes for their production, are given in the patent specifications US-A 3 905 929 and US-A 3 920 598.

[0067] The bifunctional carboxylic acid used usually comprises aliphatic, cycloaliphatic, araliphatic, or aromatic carboxylic acids, where these bear at least two hydroxy groups or two primary or secondary amino groups. Preference is given to dihydroxyalkylcarboxylic acids, especially those having from 3 to 10 carbon atoms, as are also described in US-A 3 412 054. Particular preference is given to compounds of the general formula (ci)

[0068] R3

[0069] HO-R- - R-OH (^)

[0070] COOH in which R1and R2are a Ci-C4-alkanediyl group, and R3is a Ci-C4-alkyl group, and especially to dimethylolpropionic acid (DMPA).

[0071] Monomers (c) which can be used, and which have amino groups reactive toward isocyanates are diaminocarboxylic acids, or the adducts which are mentioned in DE-A 2034479 and which derive from an addition reaction of aliphatic diprimary diamines onto alpha, beta-unsaturated carboxylic acids. Compounds of this type comply by way of example with the formula (C2)

[0072] H2N-R4-NH-R5-X (C2) where R4and R5, independently of one another, are a Ci-Ce-alkanediyl group, preferably ethylene, and X is COOH. Particularly preferred compounds of the formula (c2) are N-(2-aminoethyl)-2-aminoethanecarboxylic acid and the corresponding alkali metal salts, where Na is particularly preferred as counterion. 240732

[0073] 10

[0074] Alongside the bifunctional carboxylic acids, other monomers having hydrophilic groups can optionally also be used, examples being appropriate dihydroxysulfonic acids and dihydroxyphosphonic acids, such as 2,3-dihydroxypropane- phosphonic acid, or diaminosulfonic acids. However, it is preferable not to use any bifunctional sulfonic acids or phosphonic acids.

[0075] Ionic hydrophilic groups are especially anionic groups such as the sulfonate group, the carboxylate group, and the phosphate group, in the form of their alkali metal salts or ammonium salts, and also cationic groups, such as ammonium groups, in particular protonated tertiary amino groups, or quaternary ammonium groups. Potentially ionic hydrophilic groups are especially those which can be converted into the abovementioned ionic hydrophilic groups via simple neutralization, hydrolysis, or quaternization reactions, therefore being by way of example carboxylic acid groups or tertiary amino groups. (Potentially) ionic monomers are described by way of example in Ullmanns Enzyklopadie der technischen Chemie [Ullmann's encyclopedia of industrial chemistry], 4thedition, volume 19, pp. 311-313, and by way of example in DE-A 1 495745, in detail.

[0076] (Potentially) cationic hydrophilic monomers that are of particular practical importance are especially monomers having tertiary amino groups, examples being: tris(hydroxyalkyl)amines, N, N'-bis(hydroxyalkyl)alkylamines, N- hydroxyalkyl dialkylamines, tris(aminoalkyl)amines, N, N'-bis(aminoalkyl)alkylamines, and N-aminoalkyl dialkylamines, where the alkyl radicals and alkanediyl units of said tertiary amines are composed independently of one another of from 1 to 6 carbon atoms. Other compounds that can be used are polyethers having tertiary nitrogen atoms and preferably having two terminal hydroxy groups, for example those accessible in a manner which is conventional per se via al koxy lation of amines having two hydrogen atoms bonded to amine nitrogen, e.g. methylamine, aniline, or N, N'-dimethylhydrazine. The molar mass of polyethers of this type is generally from 500 to 6000 g / mol. Said tertiary amines are converted to the ammonium salts either with acids, preferably strong mineral acids, such as phosphoric acid, sulfuric acid, hydrohalic acids, or strong organic acids, or via reaction with suitable quaternizing agents, such as Ci-Ce-alkyl halides or benzyl halides, e.g. bromides or chlorides.

[0077] To the extent that monomers having potentially ionic groups are used, the conversion of these to the ionic form can take place prior to, during, or preferably after the isocyanate polyaddition reaction, since the ionic monomers are often only sparingly soluble in the reaction mixture. It is particularly preferable that the carboxylate groups are present in the form of their salts with an alkali metal ion or ammonium ion as counterion.

[0078] The monomers (d) which differ from the monomers (a) to (c) and which optionally are also constituents of the polyurethane are generally used for crosslinking or for chain extension. They are generally nonphenolic alcohols of functionality more than two, amines having 2 or more primary and / or secondary amino groups, or else compounds which have not only one or more alcoholic hydroxy groups but also one or more primary and / or secondary amino groups. Examples of alcohols which have functionality higher than 2 and which can be used to adjust to a certain degree of branching or of crosslinking are trimethylolpropane, glycerol, or sugars. Monoalcohols can also be used 240732

[0079] 11 where these bear not only the hydroxy group but also another group reactive toward isocyanates, examples being monoalcohols having one or more primary and / or secondary amino groups, e.g. monoethanolamine.

[0080] Polyamines having 2 or more primary and / or secondary amino groups are used especially when the chain extension and, respectively, crosslinking reaction is intended to take place in the presence of water, since the speed of reaction of amines with isocyanates is generally greater than that of alcohols or water. This is frequently a requirement when aqueous dispersions of crosslinked polyurethanes or polyurethanes with high molecular weight are desired. In such cases, the procedure is to produce prepolymers having isocyanate groups, to disperse these rapidly in water, and then to subject them to chain-extension or crosslinking via addition of compounds having a plurality of amino groups reactive toward isocyanates. Amines suitable for this purpose are generally polyfunctional amines in the molar-mass range from 32 to 500 g / mol, preferably from 60 to 300 g / mol, where these comprise at least two amino groups, selected from the group of the primary and secondary amino groups. Examples here are diamines, such as diaminoethane, diaminopropanes, diaminobutanes, diaminohexanes, piperazine, 2,5-dimethylpiperazine, 1-amino-3- (aminomethyl)-3,5,5-trimethylcyclohexane (isophoronediamine, IPDA), 4,4'-diaminodicyclohexylmethane, 1,4- diaminocyclohexane, aminoethyl ethanolamine, hydrazine, hydrazine hydrate, or triamines, such as diethylenetriamine or 1,8-diamino-4-aminomethyloctane.

[0081] The amines can also be used in capped form, e.g. in the form of the corresponding ketimines (see, for example, CA-A 1 129 128), ketazines (cf. , for example, US-A 4 269 748), or amine salts (see US-A 4292 226). Oxazolidines, for example those used in US-A 4 192 937, are also capped polyamines which can be used for producing the polyurethanes of the invention, for purposes of chain-extension of the prepolymers. When capped polyamines of this type are used, they are generally mixed with the prepolymers in the absence of water, and this mixture is then mixed with the dispersion water or with a portion of the dispersion water, so that the corresponding polyamines are liberated by hydrolysis.

[0082] It is preferable to use mixtures of di- and triamines, and it is particularly preferable to use mixtures of isophoronediamine (IPDA) and diethylenetriamine (DETA).

[0083] The polyurethanes preferably comprise, as monomers (d), from 1 to 30 mol%, particularly from 4 to 25 mol%, based on the total amount of functional groups of monomers reactive towards isocyanates, of a polyamine having at least 2 amino groups reactive toward isocyanates. It is also possible to use, as monomers (d) for the same purpose, isocyanates of functionality higher than two. Examples of compounds available commercially are the isocyanurate or the biuret of hexamethylene diisocyanate.

[0084] Monomers (d2) which are optionally used concomitantly are monoisocyanates, monoalcohols, and monoprimary and -secondary amines. The proportion of these is generally at most 10 mol%, based on the total molar amount of the monomers. Said monofunctional compounds usually bear other functional groups, examples being olefinic groups or carbonyl groups, and are used to introduce functional groups into the polyurethane, where these permit the 240732

[0085] 12 dispersion and, respectively, the crosslinking or further polymer-analogous reaction of the polyurethane. Monomers that can be used for this purpose are those such as isopropenyl-a,a-dimethylbenzyl isocyanate (TMI) and esters of acrylic or methacrylic acid, e.g. hydroxyethyl acrylate or hydroxyethyl methacrylate.

[0086] Preferably, the polyurethane consists to at least 50% by weight, more preferably to at least 80% by weight, or to at least 90% by weight, based on the sum of all monomers, of diisocyanates (a), diols (b) and bifunctional carboxylic acids (c).

[0087] The total amount of monomers (d1) and (d2) is preferably up to or less than 10% by weight, for example 0,1 to 10% by weight or 0.5 to 5% by weight.

[0088] Adhesives with particularly good property profile are especially obtained if monomers (a) used are in essence only aliphatic diisocyanates, cycloaliphatic diisocyanates, or araliphatic diisocyanates. Preferably said monomer combination is complemented by, as component (c), alkali-metal salts of dihydroxy- or diamino monocarboxylic acid; the Na salt is most suitable here.

[0089] Most preferred are components (a) to (d) which result in a polyurethane with a glass transition temperature of less than 20 °C, preferably in the range of -45°C to +15°C, and either no melting point above 20°C or wherein the polyurethane has a melting point above 20 °C with an enthalpy ef fusion lower than 10 J / g.

[0090] Preferably, the polyurethane (preferably the polyurethane from the aqueous polyurethane dispersion adhesive) has a glass transition temperature of below 20°C, preferably in the range of -45°C to +15°C, measured by differential scanning calorimetry as the midpoint temperature of the second heating curve at a heating rate of 20 K / min.

[0091] The method for adjusting the molecular weight of the polyurethanes via selection of the proportions of the mutually reactive monomers, and also of the arithmetic average number of reactive functional groups per molecule, is well known in the polyurethane chemistry sector. The normal method selects components (a) to (d), and also the respective molar amounts of these, in such a way that the ratio A:B, where

[0092] A is the molar amount of isocyanate groups and

[0093] B is the sum of the molar amount of the hydroxy groups and of the molar amount of the functional groups which can react with isocyanates in an addition reaction, can be from 0.5:1 to 2: 1 , from 0.8: 1 to 1 .5: 1 , or from 0.9: 1 to 1 .2: 1 .

[0094] The ratio A:B of isocyanate groups to groups reactive with isocyanates is preferably at least 1 :1 or higher than 1 :1, e.g. up to 2:1, or up to 1,5:1 or up to 1.2:1, most preferred as close as possible to 1 :1, so that the polyurethane has no pending NCO-reactive groups (such as pending hydroxy groups). 240732

[0095] 13

[0096] The monomers (a) to (d) used usually bear an average of from 1.5 to 2.5, preferably from 1.9 to 2.1, particularly preferably 2.0, isocyanate groups and, respectively, functional groups which can react with isocyanates in an addition reaction.

[0097] For sustainability reasons it is preferred to use bio-based materials for producing the polyurethane adhesives. The term "bio-based” indicates that the material is of biological origin and comes from a biomaterial / renewable resources. A material of renewable origin or biomaterial is an organic material wherein the carbon comes from the CO2 fixed recently (on a human scale) by photosynthesis from the atmosphere. A biomaterial (carbon of 100% natural origin) has an isotopic ratio14C / 12C greater than 10-12, typically about 1.2x10-12, while a fossil material has a zero ratio. Indeed, the isotopic14C is formed in the atmosphere and is then integrated via photosynthesis, according to a time scale of a few tens of years at most. The half-life of the14C is 5,730 years. Thus, the materials coming from photosynthesis, namely plants in general, necessarily have a maximum content in isotope14C. The determination of the content of biomaterial or of bio-carbon can be carried out in accordance with the standards ASTM D 6866-12, the method B (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04).

[0098] Suitable bio-based materials for producing polyurethanes are for example alcohols (in particular diols and polyols) and organic acids (in particular diacids) derived from natural materials such as starch, saccharose, glucose, lignocellulose, natural rubber or plant oils. Suitable alcohols and organic acids derived from natural materials are for example ethanol, monoethylene glycol, polyethylene glycol, isosorbide, 1 ,3-propanediol, 1,4-butanediol, glycerol, adipic acid or succinic acid. Preferably at least part of the polyurethane is made of bio-based materials.

[0099] The polyaddition reaction of the structural components used to produce the polyurethane preferably takes place at reaction temperatures of up to 180°C, with preference up to 150°C, at atmospheric pressure or at autogenous pressure. The production of polyurethanes and, respectively, of aqueous polyurethane dispersions is known to the person skilled in the art. The polyurethanes preferably take the form of aqueous dispersion and are used in this form. The pH of the polymer dispersion is preferably adjusted to pH above 5, in particular to pH from 5.5 to 10.5.

[0100] The adhesive to be used in the invention comprises carboxylate groups and preferably other reactive groups, where these can enter into a crosslinking reaction with one another or with external crosslinking agents. The amount of said reactive groups preferably present is from 0.0001 to 0.5 mol / 100 g of adhesive, particularly from 0.0005 to 0.5 mol / 100 g of adhesive.

[0101] Preferred polyurethane adhesives are made of high amounts of polyesterols (> 80 wt.%, based on the total weight of the polyurethane); have low isocyanate content of < 20 wt.% isocyanate compounds, based on the total weight of the polyurethane); and have low amounts of urea groups of <100 mmol / kg.

[0102] Preferred are amorphous polyester-polyurethanes with high amounts of polyesterols (> 80 wt.%, based on the total weight of the polyurethane), low isocyanate content (< 20 wt.% isocyanate compounds, based on the total weight of 240732

[0103] 14 the polyurethane) and low amount of urea (<100 mmol / kg urea-groups), which are particularly well suited for being delaminated on demand with enzymes.

[0104] Enzymes

[0105] The enzymes are capable of degrading polyester-polyurethanes. Preferred degradation of polyester-polyurethanes refers to a debonding of at least 30%, more preferred of at least 50%, after 45 min at 70 °C, measured as described in the examples. Suitable enzymes are for example esterases, lipases, proteases (peptidases) and ureases. Preferred are hydrolases of Enzyme Commission number EC 3. More preferred are enzymes of EC 3.1, i.e. hydrolases acting on ester bonds (esterases), enzymes of EC 3.4, i.e. peptidases (acting on peptide bonds) and enzymes of EC 3.5, i.e. enzymes acting on carbon-nitrogen bonds other than peptide bonds. Preferred are cutinases, proteases and ureases. The adhesive layer preferably does not comprise lipase.

[0106] Preferably, the at least one of the enzymes belongs to the class of esterases, proteases and ureases, preferably selected from esterases of EC 3.1.1 , proteases of EC 3.4.22 and ureases of EC 3.5.15.

[0107] More preferably, the at least one of the enzymes is selected from cutinase (EC 3.1.1.74), papain (EC 3.4.22.2) and urease (EC 3.5.1 .5) or combinations of two or more thereof, preferred is a combination of papain (EC 3.4.22.2) and urease (EC 3.5.1.5).

[0108] The enzymes may be used in pure form or as crude extracts. The enzymes are mixed with the polyesterpolyurethane adhesive polymer in a concentration of preferably between 0.001 and 0.5 wt.%, more preferably from 0.01 to 0.1 wt.%, based on the amount of polyester-polyurethane adhesive polymer.

[0109] Esterases are hydrolases and are a class of enzymes that split esters into an acid and an alcohol in a chemical reaction with water. Preferred esterases are esterases of EC 3.1.1. , i.e. carboxylic ester hydrolases. A preferred carboxylic ester hydrolase is cutinase. Cutinase has an assigned enzyme commission number of EC 3.1.1.74. Cutinases catalyze the reaction of esters into acid and alcohol. The at least one cutinase may be a cutinase from a fungal or microbial source. The at least one cutinase may be a cutinase from Thermobifida fusca, Thermobifida cellulosilytica, or Thermobifida alba. An example is Cutinase Novozym 51032 Stickaway from Novozymes, originating from Aspergillus micro-organism, CAS No. 9001-62-1. It is an effective catalyst for hydrolysis of triglycerides, as well as a variety of molecules containing ester linkages.

[0110] Preferred lipases are those listed in EC 3.1.1. They are enzymes that catalyze the hydrolysis of lipids (fats). Unlike esterases, which function in water, lipases are typically activated when adsorbed to an oil-water interface. The at least one lipase may be a lipase from aspergillus oryzae. An example is Lipolase 100L from Sigma Aldrich, CAS No. 9001-62-1. 240732

[0111] 15

[0112] Proteases (EC 3.4), also called peptidase, proteinase, or proteolytic enzyme, are enzymes that catalyze proteolysis. Typicall, they do this by cleaving the peptide bonds within proteins by hydrolysis. Preferred are proteases of Enzyme Commission number EC 3.4.22 (cystein proteases). A preferred protease is papain (EC 3.4.22.2). The at least one protease may be Papain (papainase) from papaya latex from Sigma Aldrich, CAS No. 9001-73-4.

[0113] Proteases may digest themselves and are therefore preferably used in combination with protease storage stabilizers, for example protease inhibitors.

[0114] Preferred hydrolases of Enzyme Commission number EC 3.5 are those of Enzyme Commission number EC 3.5.1 (enzymes acting on carbon-nitrogen bonds in linear amides other than peptides). Most preferred enzymes of EC 3.5.1 are ureases. Ureases (EC 3.5.1.5) belong to the superfamily of amidohydrolases and phosphotriesterases. These enzymes catalyze the hydrolysis of urea into carbon dioxide and ammonia. The at least one urease may be an urease from Canavalia ensiformis (Jack bean) from Sigma Aldrich, CAS No. 9002-13-5.

[0115] Most preferred enzymes are cutinase (EC 3.1.1.74), papain (EC 3.4.22.2) and urease (EC 3.5.1.5) or combinations of two or more thereof.

[0116] Particularly preferred enzymes are a combination of papain (EC 3.4.22.2) and Urease (EC 3.5.1.5).

[0117] Compositions and uses of aqueous polyurethane adhesives

[0118] In the aqueous adhesive compositions, the adhesive polymer (i.e. the adhesive polyester-polyurethanes) is present in amounts preferably of from 15 to 75 wt.-%, more preferably from 20 to 70 wt.-%. or from 30 to 60 wt.-% or from 40 to 55 wt.-%.

[0119] The aqueous adhesives may be formulated with typical additi ves.Ty pical additives are, for example, defoamers, preservatives (e.g. biocides), light stabilizers (e.g. UV stabilizers), catalysts, drying agents, antistatic agents, flame retardants, flow control agents, thickeners (preferably associative thickeners), thixotropic agents, surfactants, protective colloids, viscosity modifiers, plasticizers, levelling agents, tackifiers, dispersing aids, wetting agents, chelating agents, filler, dyes, pigments, coloring agents and crosslinking agents.. The amount of each of the additives is preferably (unless otherwise noted) 0.05% to 5% by weight, especially 0.25% to 3% by weight, based on the total weight of the aqueous polymer dispersion.

[0120] Preferably, the aqueous polyurethane dispersion adhesive comprises at least one external crosslinking agent; preferably selected from the group consisting of isocyanurates formed from diisocyanates and having at least two isocyanate groups, compounds having at least one carbodiimide group, chemically capped isocyanates, encapsulated isocyanates, encapsulated uretdiones, biurets, allophanates, aziridines, oxazolines, epoxides, and mixtures of the substances mentioned. 240732

[0121] 16

[0122] In the process for producing laminates the lamination adhesive (aqueous polyurethane dispersion adhesive) is applied to the large-surface-area substrates to be bonded (such as polymer films), preferably with an adhesive layer thickness of 0.1 to 20 g / m2, more preferably 1 to 7 g / m2, by means, for example, of knife coating, spreading, etc. Typical coating techniques may be employed, examples being roller coating, reverse roller coating, gravure roller coating, reverse gravure roller coating, brush coating, rod coating, spray coating, air brush coating, meniscus coating, curtain coating or dip coating. After a short time for the water of the dispersion or organic solvents to evaporate (preferably after 1 to 60 seconds), the coated substrate may then be laminated with a second substrate, the temperature can be, for example, 20 to 200°C, preferably 20 to 100°C, and the pressure can be, for example, 100 to 3000 kN / m2, preferably 300 to 2000 kN / m2.

[0123] The aqueous polyurethane dispersion adhesives can be used as lamination adhesives as a one-component composition with added enzyme, i.e. without additional crosslinking agents.

[0124] The aqueous polyurethane dispersion adhesives can be used as lamination adhesives as a two-component composition with the polyurethane and enzyme in a first composition and at least one crosslinking agent (e.g. a water-emulsifiable isocyanate) in a separate component, and adding the crosslinking component shortly before application of the adhesive. A two-component composition is a product consisting of two separately packaged compositions which are mixed shortly before its use.

[0125] The aqueous polyurethane dispersion adhesives can be used as lamination adhesives as a two-component composition with the polyurethane in a first composition and the enzyme as a second component to be mixed shortly before application on a substrate.

[0126] The aqueous polyurethane dispersion adhesives can be used as lamination adhesives as a three-component composition with the polyurethane in a first composition, the enzyme as a second component and at least one crosslinking agent as a third component and all three components to be mixed shortly before application on a substrate.

[0127] The amount used of the external crosslinking agent is preferably from 0.5 to 10% by weight, based on the polyurethane solids content of the dispersion. An external crosslinking agent is a compound which, prior to the crosslinking reaction, has not been bonded to the polyurethane but instead has been dispersed or dissolved in the polyurethane dispersion. However, it is also possible to use crosslinking agents which have been bonded to the polyurethane (internal crosslinking agents).

[0128] Suitable crosslinking compounds are for example polyisocyanates which are obtainable by reacting at least one monomeric isocyanate. The monomeric isocyanates used to obtain the polyisocyanate may be aromatic, aliphatic or cycloaliphatic, preferably aliphatic or cycloaliphatic, which is referred to for short in this text as (cyclo)aliphatic; aliphatic isocyanates are particularly preferred. Aromatic isocyanates are those which comprise at least one aromatic 240732

[0129] 17 ring system, i.e. both purely aromatic and araliphatic compounds. Cycloaliphatic isocyanates are those which comprise at least one cycloaliphatic ring system. Aliphatic isocyanates are those which comprise exclusively linear or branched chains, in other words acyclic compounds. The monomeric isocyanates are preferably diisocyanates bearing exactly two isocyanate groups.

[0130] Preferably, the polyisocyanates are the following compounds:

[0131] 1) Polyisocyanates which have isocyanurate groups and derive from aromatic, aliphatic and / or cycloaliphatic diisocyanates. Particular preference here is given to the corresponding aliphatic and / or cycloaliphatic isocyanato-isocyanurates and in particular to those based on hexamethylene diisocyanate and isophorone diisocyanate. These present isocyanurates are, in particular, trisisocyanatoalkyl and / or trisisocyanatocycloalkyl isocyanurates, which are cyclic trimers of the diisocyanates, or are mixtures with their higher homologs containing more than one isocyanurate ring. The isocyanatoisocyanurates generally have an NCO content of 10% to 30% by weight, in particular 15% to 25% by weight, and an average NCO functionality of 2.6 to 8.

[0132] 2) Polyisocyanates having uretdione groups, with aromatically, aliphatically and / or cycloaliphatically bonded isocyanate groups, preferably aliphatically and / or cycloaliphatically bonded, and in particular those derived from hexamethylene diisocyanate or isophorone diisocyanate. Uretdione diisocyanates are cyclic dimerization products of diisocyanates. The polyisocyanates having uretdione groups are obtained in this context in a mixture with other polyisocyanates, especially those mentioned under 1). To this end, the diisocyanates are converted under reaction conditions under which both uretdione groups and the other polyisocyanates are formed, or the uretdione groups are formed first and these are subsequently converted to the other polyisocyanates, or the diisocyanates are first converted to the other polyisocyanates and these are then converted to products containing uretdione groups.

[0133] 3) Biuret group-containing polyisocyanates having aromatically, cycloaliphatically or aliphatically bonded, preferably cycloaliphatically or aliphatically bonded, isocyanate groups, especially tris(6-isocyanatohexyl)biuret or mixtures thereof with higher homologs thereof. These polyisocyanates having biuret groups preferably (particularly in the case of HDI) have an NCO content of 18% to 23.5% by weight and an average NCO functionality of 2.8 to 6.

[0134] 4) Urethane and / or allophanate group-containing polyisocyanates having aromatically, aliphatically or cycloaliphatically bonded, preferably aliphatically or cycloaliphatically bonded, isocyanate groups, as can be obtained, for example, by reaction of excess amounts of diisocyanate, for example hexamethylene diisocyanate or isophorone diisocyanate, with mono- or polyhydric alcohols (A). These polyisocyanates having urethane and / or allophanate groups generally have an NCO content of 12% to 24% by weight and an average NCO functionality of 2.3 to 4.5. Polyisocyanates of this kind containing urethane and / or allophanate groups may be prepared uncatalyzed or, preferably, in the presence of catalysts, such as ammonium carboxylates or ammonium hydroxides, for example, or allophanatization catalysts, such as Zn(ll) compounds, for example, in each case in the presence of monohydric, dihydric or polyhydric, preferably monohydric, alcohols. 240732

[0135] 18

[0136] 5) Polyisocyanates comprising oxadiazinetrione groups, derived preferably from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates comprising oxadiazinetrione groups are obtainable from diisocyanate and carbon dioxide.

[0137] 6) Polyisocyanates comprising iminooxadiazinedione groups, derived preferably from hexamethylene diisocyanate, pentamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates comprising iminooxadiazinedione groups are preparable from diisocyanates by means of specific catalysts. They are typically present in a mixture with polyisocyanates 1), optionally also with 2) and / or 4).

[0138] 7) Uretonimine-modified polyisocyanates.

[0139] 8) Carbodiimide-modified polyisocyanates.

[0140] 9) Hyperbranched polyisocyanates, as known for example from DE-A1 10013186 or DE-A1 10013187.

[0141] 10) Polyurethane-polyisocyanate prepolymers, from di- and / or polyisocyanates with alcohols.

[0142] 11 ) Polyurea-polyisocyanate prepolymers.

[0143] 12) The polyisocyanates 1)-11), preferably 1), 3), 4) and 6), after preparation thereof, can be converted to biuret group-containing or urethane / allophanate group-containing polyisocyanates having aromatically, cycloaliphatically or aliphatically bonded, preferably (cyclo)aliphatically bonded, isocyanate groups. Biuret groups are formed, for example, by addition of water or reaction with amines. Urethane and / or allophanate groups are formed by reaction with monohydric, dihydric or polyhydric, preferably monohydric, alcohols, optionally in the presence of suitable catalysts. These biurets or urethane / allophanate group-containing polyisocyanates generally have an NCO content of 18% to 22% by weight and an average NCO functionality of 2.8 to 6.

[0144] 13) Hydrophilically modified polyisocyanates, i.e. polyisocyanates which, as well as the groups described under 1- 12, comprise those which arise in a formal sense through addition of molecules having NCO-reactive groups and hydrophilizing groups onto the isocyanate groups of the above molecules. The latter groups are nonionic groups such as alkyl polyethylene oxide and / or ionic groups derived from phosphoric acid, phosphonic acid, sulfuric acid or sulfonic acid, and / or their salts, with organic modification. They may be used here in solvent borne systems, more particularly as a co-component of the isocyanate component, preferably in waterborne applications.

[0145] 14) Modified polyisocyanates for dual-cure applications, i.e. polyisocyanates which, as well as the groups described under 1-13, comprise those which arise in a formal sense through addition of molecules having NCO-reactive groups and groups crosslinkable by UV or actinic radiation onto the isocyanate groups of the above molecules. These molecules are, for example, hydroxyalkyl (meth)acrylates and other hydroxyl-vinyl compounds.

[0146] The diisocyanates or polyisocyanates listed above may also be at least partly in blocked form. Preferred polyisocyanate crosslinking compounds are at least one polyisocyanate selected from the group consisting of isocyanurates, monooxadiazinediones, biurets, uretdiones, urethanes, and allophanates; preferably from the group consisting of isocyanurates, urethanes and allophanates, more preferably from the group consisting of isocyanurates and allophanates, and it is especially a polyisocyanate containing isocyanurate groups. In one particularly preferred embodiment, the polyisocyanate comprises polyisocyanates which comprise isocyanurate groups and derive from 240732

[0147] 19

[0148] 1,6-hexamethylene diisocyanate. In a further particularly preferred embodiment, the polyisocyanate is a mixture of polyisocyanates which comprise isocyanurate groups and derive from 1,6-hexamethylene diisocyanate, pentamethylene diisocyanate and from isophorone diisocyanate.

[0149] Substrate layer

[0150] The films (substrate layers) for producing laminated articles may be metalized or printed on the side that is coated with adhesive. Examples of suitable substrate layers include polymer films, more particularly thermoplastic polyolefins (TPO) such as polyethylene (PE), oriented polypropylene (OPP), unoriented polypropylene (OPP), polyamide (PA), polyester (preferably polyethylene terephthalate (PET)), polyacetate, ethylene / vinyl acetate copolymers (EVA), ASA (acrylnitrile / styrene / acryl acid ester copolymers), PUR (polyurethane), polyvinylchloride (PVC), preferably soft-PVC, poly(meth)acrylates, polycarbonates or their alloys, cellophane, polymer films (vapor-)- coated with metal, e.g., with aluminum (metalized films for short), or metal foils, of tin or aluminum, for example. The stated films and foils may be bonded with one another or with a foil or film of a different type - for example, polymer films with metal foils, different polymer films with one another, etc. The stated foils and films may also, for example, be printed with printing inks.

[0151] Preferred laminates comprise at least two polymeric substrate layers or a polymeric substrate layer and a metal foil substrate layer of preferably aluminum or tin, wherein the polymeric layers are selected from the group consisting of

[0152] (1) thermoplastic polyolefins (TPO), preferably polyethylene (PE), oriented polypropylene (OPP) or unoriented polypropylene (OPP);

[0153] (2) polyamide (PA);

[0154] (3) polyester, preferably polyethylene terephthalate (PET);

[0155] (4) polyacetate;

[0156] (5) ethylene / vinyl acetate copolymers (EVA);

[0157] (6) acrylnitrile / styrene / acryl acid ester copolymers (ASA);

[0158] (7) polyurethane (PUR);

[0159] (8) polyvinylchloride (PVC), preferably soft-PVC;

[0160] (9) poly(meth)acrylates;

[0161] (10) polycarbonates;

[0162] (11) cellophane; and including metalized polymer films which are coated with metal, preferably vapor-coated with metal, e.g., with aluminum.

[0163] Preferably, the adhesive (or the adhesive layer formed by the adhesive or the adhesive polyester-polyurethane) provides a peel adhesion strength of an aluminum-polyethylene laminate after 24 hours storage at 21 °C of at least 0.5 N / 15 mm at 23°C, more preferably at least 1 N / 15 mm at 21 °C, more preferably at least 2.0 N / 15 mm at 23°C, measured as described in the examples. 240732

[0164] 20

[0165] Method of making a laminate

[0166] The invention also provides a method of making a laminate with the laminate features as described above, the method comprising the steps of

[0167] (I) providing a first lamination substrate, at least one second lamination substrate different from the first lamination substrate and a lamination adhesive; and

[0168] (ii) coating a surface of the first and / or the second lamination substrate with the lamination adhesive; wherein the lamination adhesive comprises at least one adhesive polyester-polyurethane and one or more enzymes, capable of degrading the polyester-polyurethane under delamination conditions.

[0169] Method of delamination

[0170] The invention also provides a method of delamination, the method comprising the steps of

[0171] (I) providing a laminate as described above; and

[0172] (ii) delaminating the laminate by contact with an aqueous delamination liquid at elevated temperatures.

[0173] Preferably, the delamination is performed with an aqueous delamination liquid at a pH from 6 to 8.

[0174] Suitable delamination conditions are subjecting the laminate to an aqueous delamination liquid at elevated temperatures for a sufficient delamination time. The aqueous delamination liquid comprises predominantly water and optionally surfactants and pH adjusting agents and / or pH buffer. Alcohol / water mixtures can also be used as solvents, although water is preferred as sole solvent. Preferred surfactants are nonionic surfactants.

[0175] The aqueous delamination liquid can be buffered. The pH is generally between 2 and 12, preferably between 5 and 9 and most preferably between 6 and 8. The following are examples of buffers which can be used according to the invention: citrate, acetate, phosphate, formate, carbonate, tris-hydroxymethylaminomethane, triethanolamine, imidazole, oxalate, tartrate, fumarate, maleate, phthalate, succinate and ethylenediamine, as well as a plurality thereof. Acetates, phosphates and citrates are preferably used as buffers.

[0176] Elevated temperatures are temperatures above room temperature (20 °C), preferably from 30 to less than 80°C, more preferably from 40 to less than 80 °C, more preferably from 60 to less than 80 °C, more preferably from 60 to 75 °C. Preferably, the delamination is performed at temperatures from 60 to less than 80 °C, more preferably from 60 to 75 °C.

[0177] Sufficient delamination time is a time period sufficient for delamination of preferably at least 50%, more preferably 60 to 100% of the laminate. A preferred lamination time is 30 to 120 minutes. A preferred extent of lamination is at least 50%, more preferably 60 to 100% of the laminate. Preferably, the delamination is performed for a time period from 30 minutes up to 120 minutes. 240732

[0178] 21

[0179] Typicall, the extent of delamination is measured according to the debonding test method described in the examples. Typically, the extent of delamination refers to the debonded parts (wt.%) = (weight of debonded parts of the laminate I total weight of parts of laminate tested) * 100.

[0180] Advantages of the invention are that laminates can be debonded by demand, triggered by enzymes embedded in the adhesive layer (polyester-polyurethane based), when in contact with water at elevated temperatures, wherein the laminates produced with enzymes embedded in the adhesive layer are storage-stable. Delamination can be carried out at comparatively mild conditions (in only water at neutral pH at temperatures below 80°C) compared to typical standard processes (1M NaOH bath at 80°C). Increasing plastic circularity demands can be met in this way, increasing the plastic waste recycling rate of fossil-based plastic materials in flexible packaging.

[0181] Examples

[0182] Ingredients and abbreviations:

[0183] Triton® X-100 nonionic surfactant (Octylphenoxy polyethoxy ethanol)

[0184] Glass transition temperatures were determined by Differential Scanning Calorimetry (ASTM D 3418-08, ''midpoint temperature” of second heating curve, heating rate 20 K / min).

[0185] Melting-points and enthalpy ef fusion were determined according to DIN 53765 (1994) (melting point = peak temperature) by heating with 20 K / min after heating the polyurethane films to 120°C, cooling with 20 K / min to 23°C, annealing there for 20 hours.

[0186] Preparation of composite film laminates

[0187] Layered materials were prepared by using aluminum foil, polyethylene terephthalate (PET) foil or polyethylene (PE) foil. The adhesive polyester-polyurethane dispersion PU1 was applied by blade-coating at a rate of 1-2 ml I DIN A3 size foil on both foils to be treated. The foils were dried with a hot air blower for 3 min. The calendering process was performed at 60-80 °C, at 6 bar pressure. The composite film laminates were subsequently stored at room temperature under standard conditions (21 °C; 60% relative humidity), until further analysis.

[0188] Debonding Test

[0189] For the debonding tests, the Alu-PE laminates were cut in a multitude of 5x5 mm squares. Debonding tests were performed in a water bath containing 0.3% Triton® X-100, tempered at the target temperature (from 60 to less than 80 °C) and pH of 7.2. After the target incubation time, samples were removed, and the separated parts analyzed. The debonding rate is calculated as:

[0190] Debonded parts (%) = (weight of debonded PE parts I total weight of PE of the tested parts) * 100 Measurement of peel adhesion:

[0191] Following storage of the laminate for the desired time at room temperature under standard conditions (21 °C, 60% relative humidity) the laminate was cut into strips 15 mm wide. The laminate strip was pulled apart on a Zwick tensile testing machine and the force required to achieve this was recorded. The test took place at room temperature (21 °C) on a tensile testing machine at an angle of 90 degrees (T-test) and a removal velocity of 100 mm / min. The test strip was opened up on one side, with one of the resultant ends being clamped into the upper jaw and the other into the lower jaw of the tensile testing machine, and the test was commenced. The result reported was the average maximum of the force (X-Fmittel) from 3 individual measurements, in N / 15 mm.

[0192] Example PU1 - aqueous dispersion of polyester-polyurethane

[0193] 604 g of a polyesterdiol made of adipic acid, 1 ,6-hexanediol and neopentyl glycol (OH number = 56 mg KOH / g), 0.94 g trimethylolpropane and 9.39 g dimethylolpropionic acid (DMPA) were reacted at 90 °C in 70 g water-free acetone with 70.9 g hexamethylene diisocyanate for 3 hours 30 min. Then 180 g of water-free acetone was added over 7 hours and the temperature reduced to 65°C. The reaction was continued to a NCO-content of 0.4%. The mixture was then diluted with 450 g of acetone and cooled to 57°C. The mixture was neutralized with 26.3 g of a 10% strength of aqueous sodium hydroxide solution and the mixture was dispersed using 664 g of deionized water. Addition of 0.1 wt.% of Lutensol® AT 18 (nonionic surfactant).

[0194] The acetone was removed by distillation in vacuo, and solids content was adjusted to 50%. pH: 8,0; amorphous, no melting point; Tg: -52 °C

[0195] Example 1 - Debonding of PE-Aluminum-PE laminates using enzymes embedded in adhesive layer PE-Aluminum-polyethylene (Alu-PE) laminates were prepared as described above. PU1 was used as adhesive dispersion. Reference samples are composed of only PU1 without enzymes.

[0196] Enzyme containing adhesive dispersions were prepared as follows:

[0197] Enzyme stock solutions were added to the adhesive dispersion directly before coating on PE-aluminum (aluminium side) or PE foils. Enzyme concentration in the adhesive dispersion is given in wt.% in relation to the polyesterpolyurethane solid contents of the adhesive dispersion. Enzymes used are summarized in table 1.

[0198] Table 1. Enzymes tested for debonding of multi-layer materials 240732

[0199] 23

[0200] Debonding of laminates was tested 48 hours after sample preparation, using the procedure described above. Debonding was tested at 60 °C and 70°C for 45 min in the aqueous delamination liquid.

[0201] Figure 1 shows the debonding efficiency of PE-Alu-PE laminates using as adhesive layer polyester-polyurethane PU1 and different enzyme additives. "Ref' is the reference sample without enzymes.

[0202] The results are summarized in table 2.

[0203] Table 2

[0204] As observed in figure 1 and table 2, the reference samples (adhesive layer without enzyme) showed no debonding of parts at 60 °C and less than 5% debonded parts at 70°C. A significant increase in debonded parts can be seen in all enzyme containing samples. In particular using urease and protease more than 90% debonding can be achieved after 45 min at 70 °C and almost 80% at 60 °C.

[0205] Example 2 - Storage stability of enzyme containing PE-Alu-PE laminates

[0206] The PE-Alu-PE laminates prepared as described above with and without different added enzymes were stored at room temperature (approximately 21 °C and 60% relative humidity) up to 28 days. At different time intervals peel adhesion tests were performed to determine the adhesion integrity of the laminates. As a reference a sample containing only PU1 without any enzyme was used.

[0207] Figure 2 shows the peel adhesion (X-Fmittel) upon storage of PE-Alu-PE laminates using as adhesive layer polyester-polyurethane PU1 and different enzyme additives. "Ref” is the reference sample without enzymes.

[0208] The results are summarized in table 3. 24

[0209] Table 3 Peel adhesion test results

[0210] The peel adhesion values (X-Fmittel) provide an indication of the adhesion strength of the prepared lamination adhesives. Decrease in these values indicates a decrease in the adhesion properties of the laminates. As illustrated in table 3 and figure 2, the reference sample containing only polyester-polyurethane adhesive without enzyme maintains a constant adhesion strength on the course of 28 days. Samples containing papain and / or urease maintain a similar adhesion strength as well as the reference material. Samples containing cutinase show a slight initial decrease in adhesion strength which remains constant upon longer storage.

[0211] Samples containing lipase showed a decrease in adhesion after 28 days. Therefore, the adhesive layer preferably does not comprise lipase.

Claims

24073225Claims1. Laminate comprising at least two substrate layers of different materials bonded together by an adhesive layer, wherein the adhesive layer comprises one or more adhesive polyester-polyurethanes and one or more enzymes capable of degrading polyester-polyurethanes, preferred enzymes are selected from hydrolases of Enzyme Commission number EC 3, more preferred enzymes of EC 3.1, peptidases of EC 3.4 and enzymes of EC 3.5.

2. Laminate according to claim 1, wherein the adhesive layer is formed from an aqueous polyurethane dispersion adhesive, where the polyurethane is composed of(a) at least one diisocyanate;(b) one or more dihydroxy compounds, wherein at least one of the dihydroxy compounds is a polyesterdiol;(c) at least one compound having at least one group reactive toward isocyanate groups, and additionally carrying at least one ionic group or one group which can be converted into an ionic group, wherein the compounds c) preferably contain a group selected from carboxylate groups and sulfonate groups; and(d) optionally further compounds different from a) to c).

3. Laminate according to claim 2, wherein the polyurethane is composed of a) at least one monomeric diisocyanate, selected from diisocyanates of the formula X(NCO)2, where X is a noncyclic aliphatic hydrocarbon radical having 4 to 15 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, an aromatic hydrocarbon radical having 6 to 15 carbon atoms, or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms, wherein the amount of aromatic diisocyanates is less than 60 mol%, based on the sum of all organic diisocyanates a), b) one or more dihydroxy compounds, where, of these, b1) from 10 to 100 mol%, based on the total amount of the dihydroxy compounds (b), are polyesterdiols with a number-average molecular weight from more than 500 and up to 5000 g / mol, and b2) from 0 to 90 mol%, based on the total amount of the dihydroxy compounds (b), have a molar mass of from 60 to 500 g / mol, and preferably at least 80% by weight of the polyurethane is composed of at least one aliphatic polyesterdiol (b1);(c) at least one bifunctional carboxylic acid selected from dihydroxy carboxylic acids and diamino carboxylic acids; and(d) optionally further compounds different from a) to c) selected from(d1) monomers having at least two reactive groups selected from alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups; and(d2) monofunctional compounds having a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group; wherein the ratio of isocyanate groups to groups reactive with isocyanates is 0.5:1 to 2:1, preferably from 0.8:1 to 1.5:1, more preferably from 0.9:1 to 1.2:1 when making the polyurethane;24073226 wherein the polyurethane is preferably made at least in part of bio-based or recycled materials.

4. Laminate according to claim 2 or 3, wherein the aqueous polyurethane dispersion adhesive comprises at least one external crosslinking agent; preferably selected from the group consisting of isocyanurates formed from diisocyanates and having at least two isocyanate groups, compounds having at least one carbodiimide group, chemically capped isocyanates, encapsulated isocyanates, encapsulated uretdiones, biurets, allophanates, aziridines, oxazolines, epoxides, and mixtures of the substances mentioned.

5. Laminate according to claim any one of claims 2 to 4, wherein the polyurethane has a glass transition temperature of below 20°C, preferably in the range of -45°C to +15°C, measured by differential scanning calorimetry as the midpoint temperature of the second heating curve at a heating rate of 20 K / min6. Laminate according to any one of claims 1 to 5, wherein the adhesive provides a peel adhesion strength of an aluminum-polyethylene laminate after 24 hours storage at 21°C of at least 0.5 N / 15 mm at 23°C, more preferably at least 1 N / 15 mm at 21 °C, more preferably at least 2.0 N / 15 mm at 23°C, measured as described in the description.

7. Laminate according to any one of claims 1 to 6, wherein the at least one of the enzymes belongs to the class of esterases, proteases and ureases, preferably selected from esterases of EC 3.1.1, proteases of EC 3.4.22 and ureases of EC 3.5.15.

8. Laminate according to any one of claims 1 to 7, wherein the at least one of the enzymes is selected from cutinase (EC 3.1.1.74), papain (EC 3.4.22.2) and urease (EC 3.5.1.5) or combinations of two or more thereof, preferred is a combination of papain (EC 3.4.22.2) and urease (EC 3.5.1.5).

9. Laminate according to any one of claims 1 to 8, wherein the adhesive layer is formed from an aqueous adhesive polymer dispersion and the enzymes are mixed with the adhesive polymer in a concentration between 0.001% and 0.5 wt.%, based on the amount of adhesive polymer.

10. Laminate according to any one of claims 1 to 9 comprising at least two polymeric substrate layers or a polymeric substrate layer and a metal foil substrate layer of preferably aluminum or tin, wherein the polymeric layers are selected from the group consisting of thermoplastic polyolefins (TPO), preferably polyethylene (PE), oriented polypropylene (OPP) or unoriented polypropylene (CPP); polyamide (PA); polyester, preferably polyethylene terephthalate (PET); polyacetate, ethylene / vinyl acetate copolymers (EVA); (6) acrylnitrile / styrene / acryl acid ester copolymers (ASA); polyurethane (PUR); polyvinylchloride (PVC), preferably soft-PVC; poly(meth)acrylates; polycarbonates; cellophane; and including metalized polymer films which are coated, preferably vapor coated, with metal, preferably with aluminum.2407322711 . Method of making a laminate with the features of any one of the preceding claims, the method comprising the steps of(I) providing a first lamination substrate, at least one second lamination substrate different from the first lamination substrate and a lamination adhesive; and(ii) coating a surface of the first and / or the second lamination substrate with the lamination adhesive; wherein the lamination adhesive comprises at least one adhesive polyester-polyurethane and one or more enzymes, capable of degrading the polyester-polyurethane under delamination conditions.

12. Method of delamination, the method comprising the steps of(I) providing a laminate according to any one of the preceding claims; and(ii) delaminating the laminate by contact with an aqueous delamination liquid at elevated temperatures.

13. Method according to the preceding claim, wherein delamination is performed with an aqueous delamination liquid at a pH from 6 to 8.

14. Method according to any one of claims 12 to 13, wherein delamination is performed at temperatures from 60 to less than 80 °C.

15. Method according to any one of claims 12 to 14, wherein delamination is performed for a time period from 30 minutes up to 120 minutes.

16. Use of an aqueous polyurethane dispersion pressure-sensitive adhesive comprising at least one polyester- polyurethane as defined in any one of claims 2 to 5 and at least one enzyme capable of degrading polyesterpolyurethanes, preferably selected from hydrolases of Enzyme Commission number EC 3, peptidases of EC 3.4 and enzymes of EC 3.5 for making a multilayer packaging material comprising at least two polymeric layers or a polymeric layer and an aluminum layer, wherein the multilayer packaging material can be delaminated to at least 50 % by an aqueous composition at pH from 6 to 8 at temperatures from 60 to less than 80 °C within 30 to 120 minutes.

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