ADHESIVES

Description

[0001] The present invention relates to an aqueous dispersion containing at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, wherein the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C, a process for producing the aqueous dispersion, the use of the aqueous dispersion for producing coated substrates or for producing adhesive films, planar or three-dimensional substrates coated with the aqueous dispersion, a substrate coated with at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, wherein the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C.an adhesive film comprising at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, characterized in that the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C, and a dried adhesive film obtained from such an aqueous dispersion.

[0002] It is known from the prior art to use polyurethanes with linear polymer chains that crystallize at temperatures below 50 °C for the heat-activated bonding of temperature-sensitive substrates. However, when processed without the addition of a crosslinker, only low heat resistances are achieved, corresponding to the melting temperature of the polyester segments present in the polyols. Furthermore, the hydrolysis resistance of the adhesive bond is insufficient for many applications when processed without a crosslinker. For this reason, such dispersion polymers are usually processed with the addition of hydrophilically modified polyisocyanates that are liquid at 23 °C. The gain in improved properties, however, comes at the cost of increased technical effort for the so-called two-component (2K) processing.The crosslinking component must be added immediately before processing the dispersion. Furthermore, the two-component process is prone to errors regarding the addition of the correct amount of crosslinking component and its homogeneous incorporation.

[0003] A typical "pot life" of such a two-component mixture is generally one to twelve hours. Furthermore, the dried adhesive layers must be processed within approximately one to twelve hours, the so-called "open time," because otherwise, due to the ongoing crosslinking reaction, the polymer will no longer be sufficiently flowable to be processed under the usual conditions of heat-induced bonding.

[0004] The two-component method therefore has the disadvantage that the steps of applying the dispersion or creating the adhesive layer on the substrate surfaces to be bonded and the joining process cannot be separated either temporally or spatially. From an economic perspective, however, this separation would be practical and desirable for a large number of applications.

[0005] Adhesive formulations containing solid, finely divided isocyanates are known from the prior art. These so-called latent-reactive dispersion adhesives are based on a dispersion containing an isocyanate-reactive polymer and finely divided solid isocyanate particles. Suitable solid isocyanates are, in particular, polyisocyanates with a melting or softening temperature of more than 40 °C.

[0006] EP-A 1 172 390 discloses storage-stable, essentially aqueous dispersions containing deactivated isocyanates and isocyanate-reactive polymers that crosslink even at low temperatures. The crosslinking reaction begins after water removal at temperatures of 5 to 40 °C. These aqueous dispersion preparations are characterized by good storage stability. A disadvantage of this solution is that the coating produced from the dispersion is not storage-stable, as the crosslinking reaction begins as soon as the layer dries. The desired spatial and temporal separation of the adhesive application and joining processes cannot be achieved with this method.

[0007] EP-A 1 134 245 describes storage-stable preparations made from finely divided di- and polyisocyanate powders that can be incorporated directly into aqueous isocyanate-reactive polymer dispersions without surface deactivation. In these formulations, the crosslinking reaction is triggered by heating the dried layer to a temperature of at least 65 °C. However, the coatings obtained from these formulations are not storage-stable. The desired spatial and temporal separation of the adhesive application and joining processes cannot be achieved with these instructions either.

[0008] EP-A 0 922 720 discloses the use of aqueous dispersions containing at least one surface-deactivated polyisocyanate and at least one isocyanate-reactive polymer for the production of storage-stable, latently reactive films or powders that can be crosslinked by heating. Any aliphatic, cycloaliphatic, heterocyclic, or aromatic isocyanates with a melting point above 40 °C can be used as polyisocyanates. According to this teaching, the stability of the unreacted (latently reactive) systems (films or powders), the reaction temperature, and the reaction progress are determined by the type of polyisocyanate, the amount of surface stabilizer, the solution parameter of the functionalized polymer, as well as by catalysts, plasticizers, and additives.

[0009] EP 2 209 619 A1 describes identification documents coated with a latent-reactive adhesive layer. The adhesive application and bonding processes are separated both temporally and spatially. The aqueous latent-reactive adhesive layer is dried, and the thermoplastic films coated with the reactive adhesive polymer are stored at room temperature. The coated substrates have a shelf life of at least 21 days. The bonding process is preferably carried out at a temperature below 90 °C.

[0010] In the automotive industry, for example, there is a desire to equip decorative films with reactive adhesive layers that are stable over time, and where the stability of the adhesive layers must be maintained even at temperatures well above 40 °C for several months. The decorative films are intended to be coated with the reactive adhesive polymer in a temperate climate zone, such as Northern Europe, and then, if required, applied to a substrate in a hotter climate zone, such as North Africa or Mexico. To make this production chain economically viable, the decorative films coated with the reactive adhesive layer, or the adhesive films themselves, must be able to be transported and stored without a refrigeration chain.

[0011] The object of the present invention is therefore to provide an aqueous dispersion, in particular for the formation of a latent-reactive adhesive layer, a corresponding adhesive film or adhesive powder, which is stable at temperatures above 50 °C and which can be stored, for example, for several months at temperatures above 50 °C without any significant cross-linking of the adhesive polymer occurring.

[0012] The problem was solved by the aqueous dispersion according to the invention containing at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, wherein the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C.

[0013] The present invention relates to an aqueous dispersion containing at least one semi-crystalline polyurethane-polyurea polymer. The semi-crystalline polymers present in the dispersed phase can be polyurethanes in the narrower sense, i.e., polymers obtained by the polymerization of polyols and polyisocyanates, and / or they can also be polymers in which mono- and / or diamines are used as structural components, optionally as chain extenders, forming urea groups. Thus, the dispersions usable according to the invention are referred to as aqueous polyurethane-polyurethane dispersions.

[0014] According to the invention, a polymer is described as semi-crystalline or crystalline if it exhibits a melting peak in DSC measurements according to DIN 65467-1999-03 at a heating rate of 20 K / min. The melting peak is caused by the melting of regular substructures within the polymer. The melting temperature of the polymers or polymer layers obtained from the dispersions according to the invention is preferably 55 to 120 °C, particularly preferably 55 to 100 °C, and most preferably 55 to 90 °C, in each case determined by DSC measurement according to DIN 65467-1999-03. The enthalpy of fusion of the polymers or polymer layers obtained from the dispersions according to the invention is generally > 10 J / g, preferably > 20 J / g, and particularly preferably > 25 J / g. The first heating is evaluated in each case to also include slowly crystallizing polymers.

[0015] In general, the present invention can be carried out with any semi-crystalline polyurethane polyurea polymer with a suitable melting temperature that would appear suitable to a person skilled in the art.

[0016] Preferably, the polyurethane-polyurea polymer used according to the invention is composed of A(i) at least one crystalline or semi-crystalline difunctional polyester polyol with a number-average molecular weight of at least 400 g / mol and a melting point of at least 55 °C, A(ii) optionally at least one difunctional polyol component with a number-mean molecular weight of 62 to 399 g / mol, A(iii) at least one isocyanate component A(iv) at least one component reactive towards isocyanate, which bears at least one ionic or potentially ionic group, and A(v) optionally, further components reactive towards isocyanate.

[0017] The at least one semi-crystalline polyurethane polyurea polymer preferably contains 50 to 95 wt.% of component A(i), 0 to 10 wt.% of component A(ii), 4 to 25 wt.% of component A(iii), 0.5 to 10 wt.% of component A(iv) and 0 to 30 wt.% of component A(v), wherein the sum of the components equals 100 wt.%.

[0018] Preferably, the at least one semi-crystalline polyurethane polyurea polymer contains 65 to 92 wt.% of component A(i), 0 to 5 wt.% of component A(ii), 6 to 15 wt.% of component A(iii), 0.5 to 5 wt.% of component A(iv) and 0 to 25 wt.% of component A(v), wherein the sum of the components equals 100 wt.%.

[0019] Particularly preferably, the at least one semi-crystalline polyurethane polyurea polymer contains 75 to 92 wt.% of component A(i)), 0 to 5 wt.% of component A(ii), 8 to 15 wt.% of component A(iii), 0.5 to 4 wt.% of component A(iv) and 0 to 15 wt.% of component A(v), wherein the sum of the components equals 100 wt.%.

[0020] Most preferably, the at least one semi-crystalline polyurethane polyurea polymer contains 80 to 90 wt.% of component A(i), 0 to 3 wt.% of component A(ii), 8 to 14 wt.% of component A(iii), 0.5 to 3 wt.% of component A(iv) and 0 to 10 wt.% of component A(v), wherein the sum of the components equals 100 wt.%.

[0021] Suitable crystalline or semi-crystalline difunctional polyester polyols A(i) include, in particular, linear or weakly branched polyester polyols based on dicarboxylic acids and / or their derivatives, such as anhydrides, esters, or acid chlorides, and preferably aliphatic linear polyols. Mixtures of dicarboxylic acids and / or their derivatives are also suitable. Examples of suitable dicarboxylic acids are adipic acid, succinic acid, sebacic acid, or dodecanedioic acid. Succinic acid, adipic acid, and sebacic acid, and mixtures thereof, are preferred. These are used in amounts of at least 90 mol%, preferably 95 to 100 mol%, based on the total amount of all carboxylic acids.

[0022] The difunctional polyester polyols A(i) can be prepared, for example, by polycondensation of dicarboxylic acids with polyols. The polyols preferably have a number-average molecular weight of at least 400 g / mol, consist of 2 to 12 carbon atoms, are preferably unbranched, difunctional, and / or preferably possess primary OH groups.

[0023] Examples of polyols that can be used for the production of polyester polyols A(i) are polyhydric alcohols, such as ethanediol, di-, tri-, tetraethylene glycol, 1,2-propanediol, di-, tri-, tetrapropylene glycol, 1,3-propanediol, butanediol-1,4, butanediol-1,3, butanediol-2,3, pentanediol-1,5, hexanediol-1,6, 2,2-dimethyl-1,3-propanediol, 1,4-dihydroxycyclohexane, 1,4-dimethylolcyclohexane, octanediol-1,8, decanediol-1,10, dodecanediol-1,12 or mixtures thereof.

[0024] Preferred polyol components for the polyester polyols A(i) are ethanediol-1,2, butanediol-1,4, hexanediol-1,6 and 1,4-dimethylolcyclohexane or mixtures thereof.

[0025] The polyester polyols A(i) can be composed of one or more polyols. In a preferred embodiment of the present invention, they are composed of only one polyol. If the crystalline or semi-crystalline difunctional polyester polyols have a number-average molecular weight of at least 400 g / mol and a melting point of at least 60 °C and a heat of fusion of at least 35 J / g, the polymer produced using the same regularly has a heat of fusion of at least 25 J / g, preferably at least 35 J / g. If desired, the heat of fusion of the polymer can be adjusted by slightly changing the content of polyester polyol A(i) in the composition or by slightly varying the heat of fusion of the polyester polyol. These measures require only preliminary tests and are entirely within the practical experience of the average person skilled in the art in this field.

[0026] The production of polyester polyols A(i) is known from the prior art.

[0027] The number-average molecular weight of the polyester polyols A(i) is preferably between 400 and 4000 g / mol, more preferably between 1000 and 3000 g / mol, particularly preferably between 1500 and 2500 g / mol, and most preferably between 1800 and 2400 g / mol.

[0028] The melting point of the crystalline or semi-crystalline polyester polyols A(i) is generally at least 55 °C, preferably 60 to 100 °C, and particularly preferably 60 to 90 °C. The heat of fusion is at least 35 J / g, preferably at least 40 J / g, and particularly preferably at least 50 J / g.

[0029] Suitable difunctional polyol components with a molecular weight of 62 to 399 g / mol, if present, include, for example, the polyols mentioned for the production of polyester polyols A(i). Low-molecular-weight polyester diols, polyether diols, polycarbonate diols, or other polymer diols are also suitable in principle, provided they have a molecular weight of 62 to 399 g / mol.

[0030] Suitable building blocks A(iii) are any organic compounds that have at least two free isocyanate groups per molecule. Diisocyanates of the general formula Y(NCO)₂ are preferably used, where Y represents a divalent aliphatic hydrocarbon residue with 4 to 12 carbon atoms, a divalent cycloaliphatic hydrocarbon residue with 6 to 15 carbon atoms, a divalent aromatic hydrocarbon residue with 6 to 15 carbon atoms, or a divalent araliphatic hydrocarbon residue with 7 to 15 carbon atoms.

[0031] Preferred examples of suitable diisocyanates are selected from the group consisting of tetramethylene diisocyanate, methylpentamethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanato-cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanato-methyl-cyclohexane, 4,4'-diisocyanato-dicyclohexylmethane, 4,4'-diisocyanato-dicyclohexyl-propane-(2,2), 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanato-diphenylmethane, 2,2'- and 2,4'-diisocyanatodiphenylmethane, tetramethylxylylene diisocyanate, p-xylylene diisocyanate, p-isopropylidene diisocyanate and mixtures thereof.

[0032] It is also possible to partially use higher-functional polyisocyanates known in polyurethane chemistry per se, or modified polyisocyanates known per se, for example those containing carbodiimide groups, allophane groups, isocyanurate groups, urethane groups and / or biuret groups.

[0033] In addition to the aforementioned simple diisocyanates, polyisocyanates are also suitable according to the invention which contain heteroatoms in the residue linking the isocyanate groups and / or possess a functionality of more than two isocyanate groups per molecule. The former are, for example, polyisocyanates composed of at least two diisocyanates and consisting of uretdione, isocyanurate, urethane, allophanate, biuret, carbodiimide, imino-oxadiazinedione, and / or oxadiazinetrione structures, produced by modifying simple aliphatic, cycloaliphatic, araliphatic, and / or aromatic diisocyanates. As an example of an unmodified polyisocyanate with more than two isocyanate groups per molecule, 4-isocyanatomethyl-1,8-octanediisocyanate (nonanetriisocyanate) may be mentioned.

[0034] Particularly preferred structural components A(iii) are selected from the group consisting of hexamethylene diisocyanate (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI) and mixtures thereof.

[0035] Preferred components A(iv) that are reactive towards isocyanate and bear at least one ionic or potentially ionic group are mono- and dihydroxycarboxylic acids, mono- and diaminocarboxylic acids, mono- and dihydroxysulfonic acids, mono- and diaminosulfonic acids, as well as mono- and dihydroxyphosphonic acids or mono- and diaminophosphonic acids and their alkali and ammonium salts.Examples include dimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid, N-(2-aminoethyl)-β-alanine, N-(2-aminoethyl)-2-aminoethanesulfonic acid, N-(2-aminoethyl)-2-aminoethanecarboxylic acid, ethylenediaminepropyl or butylsulfonic acid, 1,2- or 1,3-propylenediamine-β-ethylsulfonic acid, malic acid, citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, lysine, 3,5-diaminobenzoic acid, an addition product of IPDI and acrylic acid (see EP-A 0 916 647, Example 1) and its alkali and / or ammonium salts; The adduct of sodium bisulfite to butene-2-diol-1,4-polyethersulfonate, the propoxylated adduct of 2-butenediol and NaHSO₃ (e.g., described in DE-A 2 446 440, pages 5 to 9, formulas I to III). Sodium, potassium, lithium, and calcium hydroxides, as well as tertiary amines such as triethylamine, dimethylcyclohexylamine, and ethyldiisopropylamine, are well suited for salt formation. Other amines can also be used for salt formation, such as...Ammonia, diethanolamine, triethanolamine, dimethylethanolamine, methyldiethanolamine, aminomethylpropanol, and mixtures of these and other amines. It is advisable to add these amines only after the isocyanate groups have largely reacted.

[0036] Building blocks such as N-methyl-diethanolamine, which can be converted into cationic groups by the addition of acids, are also suitable as component A(iv).

[0037] Particularly preferred components A(iv) are those which have carboxyl and / or carboxylate and / or sulfonate groups.

[0038] Particularly preferred as component A(iv) are the sodium salts of N-(2-aminoethyl)-2-aminoethanesulfonic acid and N-(2-aminoethyl)-2-aminoethanecarboxylic acid, especially N-(2-aminoethyl)-2-aminoethanesulfonic acid. Furthermore, the salts of dimethylolpropionic acid are particularly preferred.

[0039] Components A(v) that are reactive towards isocyanates can be, for example, polyoxyalkylene ethers containing at least one hydroxy or amino group. The commonly used polyalkylene oxide polyether alcohols can be accessed in a known manner by alkoxylation of suitable starter molecules. Alkylene oxides suitable for the alkoxylation reaction include, in particular, ethylene oxide and propylene oxide, which can be used individually or together in the alkoxylation reaction.

[0040] Other components A(v) that are reactive towards isocyanate include, for example, monoamines, diamines and / or polyamines and their mixtures.

[0041] Examples of monoamines include aliphatic and / or alicyclic primary and / or secondary monoamines such as ethylamine, diethylamine, the isomeric propylamines and butylamines, higher linear aliphatic monoamines, and cycloaliphatic monoamines such as cyclohexylamine. Further examples are amino alcohols, i.e., compounds containing amino and hydroxyl groups in one molecule, such as ethanolamine, N-methylethanolamine, diethanolamine, or 2-propanolamine. Examples of diamines are 1,2-ethanediamine, 1,6-hexamethylenediamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (isophoronediamine), piperazine, 1,4-diaminocyclohexane, and bis-(4-aminocyclohexyl)methane. Adipic acid dihydrazide, hydrazine, and hydrazine hydrate are also examples. Other examples are amino alcohols, i.e. compounds that contain amino and hydroxyl groups in one molecule, such as 1,3-diamino-2-propanol, N-(2-hydroxyethyl)ethylenediamine or N,N-bis(2-hydroxyethyl)ethylenediamine.Examples of polyamines are diethylenetriamine and triethylenetetramine.

[0042] In a preferred embodiment of the invention, the polymer according to the invention contains at least one monoamine and / or at least one diamine as component A(v) that is reactive towards isocyanate in order to adjust the molar mass.

[0043] The aqueous dispersion according to the invention further contains at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate.

[0044] According to the invention, glassy, ​​crystalline and / or (partially) crystalline solid isocyanates can be used. Particularly suitable glassy, ​​crystalline and / or (partially) crystalline solid isocyanates according to the invention have a melting or softening temperature of at least 30 °C, determined by DSC measurement according to DIN 65467-1999-03.

[0045] According to the invention, preferred solid isocyanates are all aliphatic, cycloaliphatic and aromatic di- and polyisocyanates that have a softening temperature of at least 55 °C. Particularly preferred are dimerization and trimerization products of isophorone diisocyanate, for example available as Desmodur®< I, Covestro Deutschland AG, Leverkusen; bis-(4-isocyanatocyclohexyl)methane, for example available as Desmodur®< W, Covestro Deutschland AG, Leverkusen; ω,ω'-diisocyanato-1,3-dimethylcyclohexane (H6XDI); and mixtures of these dimerization and trimerization products, as well as mixed trimerizates of isophorone diisocyanate / bis-(4-isocyanatocyclohexyl)methane, isophorone diisocyanate / hexamethylene diisocyanate, bis-(4-isocyanatocyclohexyl)methane / hexamethylene diisocyanate, and bis-(4-isocyanatocyclohexyl)methane / ω,ω'-diisocyanato-1,3-dimethylcyclohexane. Isophorone diisocyanate / ω,ω'-Diisocyanato-1,3-dimethylcyclohexane can be used according to the invention.

[0046] Dimerization products of toluene diisocyanate (TDI) are also preferred. Trimerization products of isophorone diisocyanate and dimerization products of toluene diisocyanate are particularly preferred.

[0047] The aqueous dispersions according to the invention generally contain 15 to 60 wt.% of the at least one semi-crystalline polyurethane polyurea polymer, 0.2 to 30 wt.% of the at least one surface-deactivated polyisocyanate, and 40 to 85 wt.% water, preferably 40 to 50 wt.% of the at least one semi-crystalline polyurethane polyurea polymer, 2 to 10 wt.% of the at least one surface-deactivated polyisocyanate, and 50 to 60 wt.% water. In any case, the amounts of the components present add up to 100 wt.%.

[0048] In addition to the components already mentioned, the aqueous dispersion according to the invention can contain additives selected from the group consisting of deactivating amines, thickeners, further processing-enhancing additives, for example defoamers, and mixtures thereof.

[0049] The aqueous dispersion according to the invention is produced by mixing a corresponding aqueous dispersion of the at least one polyurethane polyurea polymer with the at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate.

[0050] The present invention therefore further relates to a method for producing the aqueous dispersion according to the invention, comprising at least mixing an aqueous dispersion of the at least one polyurethane polyurea polymer with at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, for example at room temperature.

[0051] The present invention preferably relates to the method according to the invention, wherein additives are additionally added. Suitable and preferred additives are known to those skilled in the art and are mentioned above.

[0052] The aqueous dispersion according to the invention can be applied to substrates, such as flat or three-dimensional surfaces, in any desired manner, e.g., by spraying, squeegee, brushing, or roller application. After drying, storage-stable latent-reactive coatings are obtained, which can be stored at 50 °C for extended periods without any crosslinking reaction occurring that would complicate or prevent the subsequent joining process. The adhesive application and joining processes can be spatially and temporally separated using these adhesive layers. Suitable flat or three-dimensional substrates include, for example, furniture fronts, electronic components, and automotive interior parts.

[0053] The present invention therefore also relates to the use of the aqueous dispersion according to the invention for the production of coated, in particular planar or three-dimensional substrates.

[0054] The present invention further relates to planar or three-dimensional substrates coated with the aqueous dispersion according to the invention, for example release liners.

[0055] Release liners are known to those skilled in the art. A release liner is generally a substrate onto which the aqueous dispersion according to the invention is applied. After application and drying of the adhesive on the release liner, i.e., after the formation of an adhesive layer, the release liner can be peeled off the adhesive or separated from the adhesive without leaving any residue. By using release liners, "freestanding" adhesive films according to the invention can be produced. The preferred structure of the release liner according to the invention is: Release liner / adhesive / Release liner.

[0056] After drying this coating, a substrate is obtained which is coated with at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, wherein the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C.

[0057] The present invention therefore also relates to a substrate coated with at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, wherein the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C.

[0058] For example, the aqueous dispersion according to the invention can be applied to a release paper, e.g., silicone paper, polyolefinally coated non-stick paper, or similar substrate materials, using a spray, squeegee, brush, or roller application method. After drying, self-supporting latent-reactive films or nonwovens are obtained, which, if necessary after inserting a release paper, can be wound up and stored until used as an adhesive film.

[0059] The present invention further relates to the use of the aqueous dispersion according to the invention for the production of adhesive films.

[0060] Adhesive films are known to those skilled in the art and are described, for example, in EP 1 134 245 A. Typical dimensions of such adhesive films and methods for producing corresponding adhesive films are also known to those skilled in the art.

[0061] The present invention further relates to an adhesive film comprising at least one semi-crystalline polyurethane polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, characterized in that the melting temperature of the semi-crystalline polyurethane polyurea polymer is at least 55 °C.

[0062] Details and preferred embodiments of the at least one semi-crystalline polyurethane polyurea polymer and the at least one surface-activated polyisocyanate are described above and apply accordingly here.

[0063] The present invention further relates to a dried adhesive film, for example a release liner, obtained from the aqueous dispersion according to the invention, preferably according to the method described in this text or according to a method known to those skilled in the art, for example described in EP 1 134 245 A.

[0064] The present invention is explained by means of examples. Examples Definition of terms and methods:

[0065] Melting point: The melting point (Tm) is determined using DSC (differential scanning calorimetry). The melting point is the temperature at which the melting peak in the DSC diagram reaches its maximum. The heating rate during measurement is 20 K / min unless otherwise specified. The melting points given are the values ​​from the first heating. To determine the melting point and enthalpy of fusion of the dried polymers of the polyurethane dispersions, dried polymer films were produced by pouring the dispersions into Teflon trays and subsequently drying them for seven days at room temperature. Pieces with a mass of 10 mg were cut from these films and placed in DSC crucibles, which were then sealed with lids in the crucible press. The crucibles were placed in the measuring cell of the calorimeter at room temperature and cooled to -100 °C. This was followed by three heating cycles in the temperature range of -100 to +150 °C.The heating rate was 20 K / min. Cooling occurred at 320 K / min between the first and second heating cycles, and at 20 K / min between the second and third. Thermal coupling between the cooling block and the measuring cell was achieved by purging with nitrogen, and a compressor cooled the measuring cell. The first heating cycle was evaluated to determine the melting temperature and the enthalpy of fusion. The instrument used was a Pyris Diamond DSC calorimeter from Perkin-Elmer. Glass transition temperature: The glass transition temperature (Tg) characterizes the temperature range in which a substance transitions from the glassy state to the viscoelastic state. The measurement is performed using DSC (differential scanning calorimetry). The change in specific heat (Cp) during the glass transition causes a step (glass step) in the DSC diagram. The glass transition temperature is defined as the inflection point of the glass step in the DSC diagram. Unless otherwise specified, the measurement is performed at a heating rate of 20 K / min.Oscillation rheometry: The polymer sample is placed in the temperature-controlled measuring unit of the oscillation rheometer (ARES, TA instrument) and subjected to a sinusoidal deformation (frequency = 1 Hz) on one side. The phase shift of the sinusoidal deformation as it passes through the polymer sample is recorded. From the phase shift and the complex shear modulus G*, the elastic component (storage modulus G') and the frictional component G", each in Pa, can be calculated.

[0066] All samples were measured at 120 °C and a frequency of 1 Hz. Measurements were taken at 20-second intervals. The arithmetic mean was calculated from the values ​​for the storage module G' recorded in the first 60 seconds after the start of the measurement.

[0067] If the arithmetic mean value for the storage modulus G' increases by more than 200% during storage of the reactive polymer samples, then the sample is considered not to be storage-stable. Raw materials / products used:

[0068] Dispercoll® BL XP 2514: Aqueous suspension of surface-deactivated TDI dimer, melting point > 145 °C, NCO content approx. 8 wt.%, Covestro Deutschland AG, Leverkusen. Desmodur® Z 2589: Micronized IPDI trimer, NCO content approx. 17 wt.%, particle size d50 approx. 1.5 µm, Tg + 65 °C, Covestro Deutschland AG, Leverkusen. Jeffamine T-403: Polyoxypropylenetriamine, molecular weight approx. 440 g / mol, Huntsman Performance Products GmbH, Hamburg. BorchiGel L 75N: Liquid polyurethane-based thickener, Borchers GmbH, Langenfeld. BorchiGel ALA: Liquid polyacrylate-based thickener, Borchers GmbH, Langenfeld. Tamol NN 4501: Condensation product of 2-Naphthalenesulfonic acid, 45 wt% in water from BASF AG, 67056 Ludwigshafen, Germany. Lucramul 1820-liq: Aqueous solution of stearyl alcohol polyglycol ether, from [Company Name].LEVACO Chemicals GmbH, Leverkusen Polyesterdiol 1: semicrystalline polyester of sebacic acid and 1,4-butanediol, OH number 59.0, melting point 61 °C Polyesterdiol 2: semicrystalline polyester of sebacic acid and ethylene glycol with an OH number 58.0, melting point 76 °C Polyesterdiol 3: semicrystalline polyester of adipic acid and 1,4-dimethylolcyclohexane, OH number 50.9, melting point 79.8 °C Polyesterdiol 4: semicrystalline polyester of a mixture of 70 mol% succinic acid and 30 mol% adipic acid and 1,4-butanediol, OH number 52.4, melting point 79.8 °C PUD 1 (comparison): polyurethane dispersion from Covestro Deutschland AG, Leverkusen, solids content approx. 50 wt.%, isocyanate-reactive polymer of linear Polyurethane chains. The polymer crystallizes after the dispersion dries and the film cools to +23 °C. When measured by DSC, the melting point of the polyurethane polymer is +47 °C, and the enthalpy of fusion is 56 J / g.PUD 2 (comparison): Polyurethane dispersion from Covestro Deutschland AG, Leverkusen, solids content approx. 50 wt.%, isocyanate-reactive polymer consisting of linear polyurethane chains. The polymer crystallizes after drying the dispersion and cooling the film to +23 °C. When measured by DSC, the melting point of the polyurethane polymer is +47 °C, and the enthalpy of fusion is 42 J / g. Preparation of PUD 3 (according to the invention): 382.28 g of polyester diol 1 are dehydrated for 1 hour at 110 °C and 15 mbar. Subsequently, 20.14 g of isophorone diisocyanate (IPDI) and 30.11 g of hexamethylene diisocyanate (HDI) are added at 80 °C. The mixture is stirred for 1 hour at 80 °C and then at 95 °C until an isocyanate content of 1.36 wt.% is reached. The reaction mixture is dissolved in 650 g of acetone and cooled to 50 °C.A solution of 8.86 g sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and 0.90 g diethanolamine in 80 g water is added to the homogeneous solution with vigorous stirring. After 30 minutes, the mixture is dispersed by adding 590 g water. After distillation to remove the acetone, 25.5 g of Lucramul 1820-liq are added with stirring. A stable aqueous polyurethane-polyurea dispersion with a solids content of 40.2 wt% is obtained. The melting point of the dried polymer is 57.5 °C, and the enthalpy of fusion is 69.0 J / g. Preparation of PUD 4 (according to the invention): 386.80 g of polyester diol 2 are dehydrated for 1 hour at 110 °C and 15 mbar. Then, at 80 °C, 20.14 g of isophorone diisocyanate (IPDI) and 30.11 g of hexamethylene diisocyanate (HDI) are added. The mixture is stirred at 80 °C until an isocyanate content of 1.20 wt% is reached. The reaction mixture is dissolved in 656 g of acetone and cooled to 50 °C.A solution of 8.86 g sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and 0.90 g diethanolamine in 80 g water is added to the homogeneous solution with vigorous stirring. After 30 minutes, the mixture is dispersed by adding 600 g of water at 60 °C. After distillation to remove the acetone, 23.0 g of Lucramul 1820-liq are added with stirring. A stable aqueous polyurethane-polyurea dispersion with a solids content of 39.7 wt% is obtained. The melting point of the dried polymer is 59.5 °C, and the enthalpy of fusion is 65.9 J / g. Preparation of PUD 5 (according to the invention): 330.60 g of polyester diol 3 are dehydrated for 1 hour at 110 °C and 15 mbar. Then, at 80 °C, 15.10 g of isophorone diisocyanate (IPDI) and 22.58 g of hexamethylene diisocyanate (HDI) are added. The mixture is heated to 90 °C and stirred at 90 °C until an isocyanate content of 1.16 wt% is reached.The reaction mixture is dissolved in 550 g of acetone at 90 °C and then cooled to 50 °C. A solution of 5.62 g of the sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and 1.93 g of diethanolamine in 55 g of water is added to the homogeneous solution with vigorous stirring. After 30 minutes, the mixture is dispersed by adding 520 g of water at 50 °C. After distillation to remove the acetone, 19.29 g of Lucramul 1820-liq are added with stirring. A stable aqueous polyurethane-polyurea dispersion with a solids content of 40.2 wt% is obtained. The melting point of the dried polymer is 60.9 °C, and the enthalpy of fusion is 26.4 J / g. Preparation of PUD 6 (according to the invention): 321.15 g of polyester diol 4 are dehydrated for 1 hour at 110 °C and 15 mbar. Subsequently, 15.10 g of isophorone diisocyanate (IPDI) and 22.58 g of hexamethylene diisocyanate (HDI) are added at 80 °C.The mixture is heated to 90 °C and stirred at 90 °C until an isocyanate content of 1.18 wt% is reached. The reaction mixture is dissolved in 540 g of acetone at 90 °C and then cooled to 50 °C. A solution of 5.62 g of sodium salt of N-(2-aminoethyl)-2-aminoethanesulfonic acid and 1.93 g of diethanolamine in 55 g of water is added to the homogeneous solution with vigorous stirring. After 30 minutes, the mixture is dispersed by adding 502 g of water at 50 °C. After distillation to remove the acetone, 19.94 g of Lucramul 1820-liq are added with stirring. A stable aqueous polyurethane-polyurea dispersion with a solids content of 39.9 wt% is obtained. The melting temperature of the dried polymer is 69.1 °C, the enthalpy of fusion is 69.8 J / g. Table 1: Melting points of polyurethane polyurea polymers Polyurethane-polyurea polymer made of Melting point [°C] PUD 1 (Comparison) 48,9 PUD 2 (Comparison) 46,9 PUD 3 57,5 PUD 4 59,5 PUD 5 60,0 PUD 6 69,1 Production of the adhesive dispersions: The respective PUD is placed in a stainless steel beaker (diameter = 7 cm). Dispercoll BL XP 2514, Jeffamine T-403, and BorchiGel L 75 are added sequentially. The mixture is then blended homogeneously for 5 minutes at 700 rpm using a dissolver (dissolver disc diameter = 4 cm). Table 2: Composition of the adhesive dispersions: Example PUD Amount of PUD [g] Amount of Dispercoll ®< BL XP 2514 [g] Amount of Jeffamine T-403 [g] Amount of BorchiGel L75 [g] V1 1 100 7 0,15 0,4 V2 2 100 7 0,15 0,4 3 3 100 7 0,15 0,4 4 4 100 7 0,15 0,4 5 5 100 7 0,15 0,4 6 6 100 7 0,15 0,4 V. Comparative examples Preparation of polymer samples for oscillation rheometry: Seven grams of each adhesive dispersion from Examples 1 to 6 are placed in a Teflon dish (diameter = 7 cm). After drying the adhesive dispersion for one week under standard climatic conditions at 23 °C and 50% relative humidity, polymer films approximately 0.8 mm thick form. The first measurement of the polymer films in the oscillation rheometer is performed immediately after drying. The dried polymer films are stored at 55 °C for five months. Samples of the stored polymer films are examined monthly in the rheometer. Oscillation rheometry: The measurement is started immediately after the sample is placed in the measuring unit of the ARES rheometer, which is heated to 120 °C. Average values ​​are calculated from the storage module values ​​of the first 60 seconds after the start of the measurements. The crosslinking of the polymer during storage is indicated by the increase in the G' mean values. If the G' mean value rises to a value ≥ 200%, relative to the initial value of the sample immediately after the reactive adhesive sample was generated, then the polymer sample is considered to be so crosslinked that wetting of the substrate surfaces by the molten polymer can no longer be guaranteed. Table 3: Percentage change in G' mean values ​​(60 sec.) at 120 °C Example 1 month 2 months 3 months 4 months 5 months V1 100 128 223 - - V2 483 - - - - 3 120 108 115 79 105 4 53 66 70 49 86 5 82 129 103 163 - 6 102 132 112 113 89

[0069] In comparison examples V1 and V2, the mean G' values ​​from the oscillation measurements at 120 °C / 1 Hz double after one and three months of storage at 55 °C, respectively. The samples of examples 3 to 6 according to the invention remain stable.

[0070] The storage modulus values ​​of the reactive adhesive polymers of Examples 3 and 6 according to the invention do not increase above the limit of 200% when stored at 55 °C. Therefore, storage temperatures above 55 °C are, in principle, possible with the reactive adhesive polymers according to the invention.

Claims

1. Aqueous dispersion containing at least one semicrystalline polyurethane-polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, characterized in that the melting temperature of the semicrystalline polyurethane-polyurea polymer is at least 55°C, wherein the melting temperature is measured as defined in the description.

2. Dispersion according to Claim 1, characterized in that the at least one polyurethane-polyurea polymer is formed from A(i)at least one crystalline or semicrystalline difunctional polyester polyol having a number-average molecular weight of at least 400 g / mol and a melting temperature of at least 55°C,A(ii)optionally at least one difunctional polyol component having a number-average molecular weight of 62 to 399 g / mol,A(iii)at least one isocyanate component,A(iv)at least one isocyanate-reactive component bearing at least one ionic or potentially ionic group, andA(v)optionally further isocyanate-reactive components.

3. Dispersion according to Claim 2, characterized in that at least one semicrystalline polyurethane-polyurea polymer preferably contains 50% to 95% by weight of constituent A(i), 0% to 10% by weight of constituent A(ii), 4% to 25% by weight of constituent A(iii), 0.5% to 10% by weight of constituent A(iv) and 0% to 30% by weight of constituent A(v), wherein the constituents sum to 100% by weight.

4. Dispersion according to any of Claims 1 to 3, characterized in that the at least one surface-deactivated polyisocyanate is a dimerization or trimerization product of isophorone diisocyanate, bis(4-isocyanatocyclohexyl)methane, ω,ω'-diisocyanato-1,3-dimethylcyclohexane (H6XDI) and mixtures of these dimerization products and trimerization products and also mixed trimers of isophorone diisocyanate / bis(4-isocyanatocyclohexyl)methane, isophorone diisocyanate / hexamethylene diisocyanate, bis(4-isocyanatocyclohexyl)methane / hexamethylene diisocyanate, bis(4-isocyanatocyclohexyl)methane / ω,ω'-diisocyanato-1,3-dimethylcyclohexane or isophorone diisocyanate / ω,ω'-diisocyanato-1,3-dimethylcyclohexane.

5. Dispersion according to any of Claims 2 to 4, characterized in that synthesis component A(iii) is selected from the group consisting of hexamethylene diisocyanate (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) and mixtures thereof.

6. Dispersion according to any of Claims 1 to 5, characterized in that it contains 15% to 60% by weight of the at least one semicrystalline polyurethane-polyurea polymer, 0.2% to 30% by weight of the at least one surface-deactivated polyisocyanate and 40% to 85% by weight of water, preferably 40% to 50% by weight of the at least one semicrystalline polyurethane-polyurea polymer, 2% to 10% by weight of the at least one surface-deactivated polyisocyanate and 50% to 60% by weight of water, wherein the amounts of the components present in each case sum to 100% by weight.

7. Process for preparing the aqueous dispersion according to any of Claims 1 to 6 by mixing an aqueous dispersion of the at least one polyurethane-polyurea polymer with at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate.

8. Process according to Claim 7, characterized in that additives are additionally added.

9. Use of the aqueous dispersion according to any of Claims 1 to 6 for producing coated substrates.

10. Use of the aqueous dispersion according to any of Claims 1 to 6 for producing adhesive films.

11. Flat or three-dimensional substrates coated with the aqueous dispersion according to any of Claims 1 to 6.

12. Adhesive film comprising at least one semicrystalline polyurethane-polyurea polymer and at least one surface-deactivated polyisocyanate, preferably at least one surface-deactivated solid polyisocyanate, characterized in that the melting temperature of the semicrystalline polyurethane-polyurea polymer is at least 55°C.

13. Dried adhesive film obtained from an aqueous dispersion according to any of Claims 1 to 6.