Method for producing a shock-resistant adhesive compound

Abstract

Method for producing an adhesive compound, comprising the following process steps: a) Production of a first polyurethane prepolymer by reacting a first starting composition comprising i) one or more first diisocyanate compounds; ii) one or more first diol compounds; b) Production of a second polyurethane prepolymer by reacting a second starting composition comprising iii) one or more second diisocyanate compounds; iv) one or more second diol compounds; wherein at least one of the first and / or second diisocyanate compounds differs from the diisocyanate compounds of the other starting composition; and / or wherein at least one of the first and / or second diol compounds differs from the diol compounds of the other starting composition; and / or wherein the first and second polyurethane prepolymers differ in their weight-average molar mass by at least 10%, based on the polyurethane prepolymer with the higher molar mass; c) Mixing the two polyurethane prepolymers; and d) Crosslinking the prepolymer composition thus obtained; characterized in that the first or second starting composition comprises one or more polyester diols in a combined mass fraction of at least 50% and the other starting composition comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols.

Description

[0001] The invention relates to the technical field of manufacturing pressure-sensitive adhesives, more specifically the manufacturing of polyurethane-based pressure-sensitive adhesives. Specifically, the invention relates to a method for manufacturing a pressure-sensitive adhesive.

[0002] Joining separate components is one of the central processes in manufacturing technology. Alongside other methods, such as welding and soldering, bonding—that is, joining using an adhesive—is of particular importance today. An alternative to using formless adhesives, which are applied, for example, from a tube, are adhesive tapes, whose adhesive effect is based on the adhesive compounds used.

[0003] Polyurethanes have proven to be high-performance base materials for numerous technical applications as polymer systems for the production of adhesives, as disclosed, for example, in WO 2015 / 189323 A1. These polymeric compounds are mostly obtained by polyaddition of polyols with polyisocyanates and regularly possess physicochemical properties that make them ideal for use in adhesives for various high-performance applications, particularly in the field of electronic products.In addition to mostly very advantageous adhesive properties, these include, for example, high resistance to light, adverse weather conditions and a variety of chemicals, whereby it is considered particularly advantageous that the physicochemical properties of polyurethanes can in many cases be specifically adapted to the respective application requirements by the choice of the starting materials.

[0004] The production of polyurethane-based adhesives usually begins with the manufacture of so-called polyurethane prepolymers. These are polyurethanes whose average molecular weight is kept relatively low by adjusting the mixing ratio of the starting materials and / or the reaction conditions, ensuring that the typically hydroxy-terminated and still largely meltable polyurethane prepolymers can be processed effectively. Processing is achieved, for example, by mixing the polyurethane prepolymers with other components such as adhesive resins. This process also allows for efficient molding of the resulting, still meltable composition, for instance, to form the adhesive layer of an adhesive tape. The adhesive compound is then produced from the polyurethane prepolymers or...the prepolymer composition is obtained by crosslinking the polyurethane prepolymers, which in the prior art is mostly achieved by crosslinking the hydroxy-terminated polyurethane prepolymers with multifunctional isocyanates.

[0005] Despite the numerous advantages of polyurethane-based adhesives known from the state of the art, these systems are also perceived as disadvantageous in some aspects.

[0006] WO 2016 / 118399 A1 describes an adhesive compound containing a polyurethane polymer comprising the reaction product of a polyisocyanate component and a polyol component, wherein the polyol component has an overall solubility parameter of 10 to 14 (cal / cm²). 3 ) 1 / 2 exhibits such properties. This type of adhesive is described as highly chemical-resistant.

[0007] A similar pressure-sensitive adhesive, whose polyurethane polymer is not only the reaction product of a polyisocyanate component and a polyol component, but also of an acid-functionalized component, is described in WO 2017 / 052680 A1. This pressure-sensitive adhesive is also attributed with excellent chemical resistance.

[0008] WO 2018 / 160350 A1 relates to an adhesive compound comprising a polyurethane polymer, which includes the reaction product of a polyisocyanate component and a polyol component. The polyol component has a hydrophilic-lipophilic balance (HLB) value of less than 10. The polyurethane further comprises 0.5 to 10 wt% polymerized hydrophilic units with an HLB value greater than 12. In one embodiment, the polyurethane also comprises ethylene unsaturated groups. This adhesive compound is also described as chemically resistant.

[0009] DE 10 2009 045 488 A1 describes a 2-component polyurethane laminating adhesive consisting of - containing a component A, at least one prepolymer with at least two NCO groups, - a component B containing at least one polymeric or oligomeric crosslinker having at least two NCO-reactive groups, wherein component B contains 0.05 to 5 wt% of a low molecular weight compound C, wherein this - should have a nucleophilic group that is reactive with NCO groups and - contains a hydrogen-bonding group selected from O=CO - or O=CCO - or O=CC=CO - or protonated forms.

[0010] DE 100 30 908 A1 discloses a polyurethane composition with pressure-sensitive adhesive properties, optimized with regard to adhesion after repeated opening and re-joining of the adhesive joint and with regard to the migration of harmful components. A polyurethane composition is proposed that is obtainable by reacting two components A and B, wherein a) as component A at least one polyurethane prepolymer A1 is used which is obtainable by reacting at least one polyol component with at least two difunctional different isocyanates and b) Component B is a hardener that is at least difunctional and has at least two functional groups per molecule that are reactive towards isocyanate groups, wherein the ratio of isocyanate groups to functional groups reactive towards isocyanate groups is greater than 0.75 and less than 1.15.

[0011] EP 1 811 006 A1 describes an adhesive system comprising as separate components: (A) a reactive mixture comprising at least one polyol and at least one polyisocyanate, and (B) a modification component comprising at least one polymerization catalyst. The separate provision of an accelerator according to component (B), which can be individually dosed on-site by the user, is intended to enable a high degree of flexibility in adjusting the open time, particularly of a one-component, moisture-curing polyurethane adhesive composition.

[0012] DD 298 118 A5 describes polyurethane systems containing isocyanate groups, obtainable by reacting at least two polyester diols with different melting points and optionally another diol with at least one polyisocyanate. These systems are suitable as hot melt adhesives with rapid crystallization, high flexibility, and good curing properties.

[0013] DE 10 2022 133 906 A1 relates to a process for producing a cross-linked adhesive, in particular within the framework of a 3D printing process, comprising the process steps: a) Production of a prepolymer composition comprising one or more polyurethane prepolymers, wherein the one or more polyurethane prepolymers can be produced by reacting a starting composition comprising: i) one or more diisocyanate compounds, ii) one or more first diol compounds, wherein the first diol compounds are selected from the group consisting of diols with one terminal C-C double bond per molecule, and iii) one or more second diol compounds different from the first diol compounds, and b) Crosslinking of the polyurethane prepolymers in the prepolymer composition by radical reaction of terminal CC double bonds of the first diol compounds to obtain crosslinked polyurethane polymers.

[0014] Good chemical resistance is a highly sought-after property for many adhesive applications, especially in the electronics industry. The products in question must, for example, withstand the effects of water and skin secretions without the adhesive bonds within them losing too much of their bonding strength and other properties.

[0015] Another important requirement for adhesive bonds, particularly in the electronics industry, is so-called shock resistance. This property refers to the behavior of the adhesive bonds in the event of vibrations, such as those caused by dropping products. As has been shown, many pressure-sensitive adhesives described in the prior art exhibit good chemical resistance but inadequate shock resistance.

[0016] Against this background, it was an object of the invention to avoid the disadvantages of the prior art. In particular, it was an object of the invention to provide a method for producing an adhesive compound that combines good chemical resistance with good shock absorption properties.

[0017] Another objective of the invention was that the method to be provided should also be suitable for use with pressure-sensitive adhesives with good adhesive properties.

[0018] A complementary objective of the invention was to design the method to be provided in such a way that it could be carried out simply and efficiently.

[0019] The solution to these problems is based on the fundamental idea of ​​using two polyurethane prepolymers, which are similar in their basic chemical structure but nevertheless different from each other, in the production of an adhesive compound. A first and general object of the invention, with which the aforementioned problems are solved, is a method for producing an adhesive compound, comprising the process steps: a) Production of a first polyurethane prepolymer by reacting a first starting composition comprising i) one or more first diisocyanate compounds; ii) one or more first diol compounds; b) Production of a second polyurethane prepolymer by reacting a second starting composition comprising iii) one or more second diisocyanate compounds; iv) one or more second diol compounds; wherein at least one of the first and / or second diisocyanate compounds differs from the diisocyanate compounds of the other starting composition; and / or wherein at least one of the first and / or second diol compounds differs from the diol compounds of the other starting composition; and / or wherein the first and second polyurethane prepolymers differ in their weight-average molar mass by at least 10%, based on the polyurethane prepolymer with the higher molar mass; c) Mixing the two polyurethane prepolymers; and d) Crosslinking the prepolymer composition thus obtained, characterized in that the first or second starting composition is or comprises several polyester diols in a combined mass fraction of at least 50% and the other starting composition comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols.

[0020] In the described manner, pressure-sensitive adhesives with pronounced chemical resistance and good shock resistance can be obtained. As has been shown, the incorporation of a component that differs from the other prepolymer—such as a diisocyanate or diol—or the use of two prepolymers with sufficiently different molecular weights is sufficient to achieve adequate shock resistance. In this respect, the required property profile of the pressure-sensitive adhesive can be achieved without altering the manufacturing process itself, and the production processes can be carried out with the usual efficiency.

[0021] The aforementioned problems are thus solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0022] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment referred to as preferred to any degree is combined with one or more further features of other embodiments referred to as preferred to any degree. Features of preferred adhesives, adhesive tapes, and uses result from the features of preferred methods.

[0023] Insofar as specific amounts or proportions of an element, for example, the diisocyanate compounds or the diol compounds, as well as preferred embodiments of the element, are disclosed below, the specific amounts or proportions of the preferably embodiments of the elements are also disclosed. Furthermore, it is disclosed that, among the corresponding specific total amounts or proportions of the elements, at least some of the elements may be preferably embodiments, and in particular, that preferably embodiments may, within the specific total amounts or proportions, again be present in specific amounts or proportions.

[0024] In accordance with professional understanding, a pressure-sensitive adhesive is an adhesive that possesses tacky properties, meaning it forms a permanent bond to a substrate even under relatively light pressure. Adhesive tapes containing such compounds are typically permanently tacky even at room temperature, meaning they exhibit a certain viscosity and tackiness, allowing them to adhere to the surface of a substrate even with minimal pressure. The tackiness of a pressure-sensitive tape results from the use of a pressure-sensitive adhesive as its base material.Without being bound to this theory, it is often assumed that an adhesive compound can be considered an extremely highly viscous liquid with an elastic component, which consequently exhibits characteristic viscoelastic properties that lead to the permanent inherent tackiness and pressure-sensitive adhesion described above. It is assumed that in adhesive compounds, mechanical deformation results in both viscous flow processes and the development of elastic restoring forces. The viscous flow component serves to achieve adhesion, while the elastic restoring forces component is particularly necessary for achieving cohesion. The relationships between rheology and pressure sensitivity are known in the prior art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology", Third Edition, (1999), pages 153 to 203.To characterize the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G'') are usually used, which can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189323 A1. Within the scope of the present invention, an adhesive compound is preferably considered to be adhesive and thus a pressure-sensitive adhesive compound if, at a temperature of 23 °C in the deformation frequency range of 10 °C to 10 °C, the following properties are observed: 1 rad / sec G' and G'' each at least partially in the range of 10 3 up to 10 7 Pa lie.

[0025] In the process according to the invention, a prepolymer composition is first produced, which is then crosslinked to obtain a crosslinked pressure-sensitive adhesive. This prepolymer composition preferably comprises, in addition to the at least two polyurethane prepolymers, other components that are to be included in the crosslinked pressure-sensitive adhesive, such as adhesive resins, colorants, or other additives, which can be added by a person skilled in the art depending on the intended application. The essential component of the prepolymer composition with regard to the invention is the at least two specific polyurethane prepolymers.

[0026] Polyurethanes themselves, as well as the urethane group from which they derive their name and the underlying chemistry, are thoroughly familiar to those skilled in the art based on their general technical knowledge, and the concept of polyurethane prepolymers is particularly familiar to them. The polyurethane prepolymers used according to the invention are copolymers produced from a specific starting composition by polymerization, more precisely polyaddition. According to the invention, "polyurethane prepolymers" are understood to be compounds in which a small change in the number of units forming the macromolecule no longer causes a significant change in the properties, so that, in accordance with IUPAC rules, the compounds in question would actually be considered polymers and no longer oligomers. This is the case at least from a weight-average molar mass of 10,000 g / mol.Therefore, the polyurethane prepolymers preferably have a weight-average molar mass of at least 8,000 g / mol, preferably at least 12,000 g / mol, and particularly preferably at least 20,000 g / mol. In accordance with the skilled person's understanding and the usual procedure in the field of technology, it is expedient to define (pre)polymers by the manufacturing process or the starting materials used for their production, since it is largely impossible to definitively define the corresponding materials in their entirety in any other way.

[0027] In accordance with this common practice in the field of technology, the manufacturability is specified above with regard to the starting composition, which, in accordance with the understanding of those skilled in the art, comprises all isolated compounds that are converted into building blocks of the polyurethane prepolymers during polymerization. Sometimes, a corresponding starting composition for the production of copolymers is also referred to as a monomer composition, although this term is not used within the scope of the present invention, since, in particular, many of the diols typically used are themselves, strictly speaking, oligomeric or polymeric compounds.In accordance with expert understanding, any other components that may be present in the reaction mixture during polymerization but are not incorporated into the polyurethane prepolymers during polymerization, such as solvents or other non-reactive compounds, are not considered part of the initial composition.

[0028] These components of the starting composition, as defined above, are each referred to as "one or more" in accordance with industry practice. The term "one or more" refers, in the usual way, to the chemical nature of the respective compounds and not to their quantity. For example, if the starting composition consists solely of hexamethylene diisocyanate, it may contain only diisocyanate compounds, which would mean that the starting composition includes a large number of the corresponding molecules.

[0029] In accordance with expert understanding, the prepolymer composition, or more precisely the polyurethane prepolymers, are still uncrosslinked in their prepolymer composition but can be crosslinked to produce a crosslinked pressure-sensitive adhesive. The person skilled in the art understands that the terms "uncrosslinked" and "crosslinked" refer to chemical crosslinking, i.e., the covalent bonding of individual copolymer strands to each other to form a network, and not to any physical crosslinking of the copolymer chains, for example, by entanglement, phase separation, or crystallization, so that polyurethane prepolymers are regularly meltable.A person skilled in the art understands that an uncrosslinked polyurethane prepolymer is not necessarily linear, but can also exhibit branched copolymer chains, which can be the case in particular if the starting composition includes not only diisocyanates and diols, but also higher-grade polyisocyanates and / or polyols. Even if the transition from branched copolymer chains to a crosslinked network of the crosslinked pressure-sensitive adhesive may appear imprecise in theory, the uncrosslinked state or the crosslinking is relatively easy for a person skilled in the art to determine in practice, for example, by examining the temperature-dependent rheological properties or by performing simple solubility tests. In crosslinked pressure-sensitive adhesives, the resulting crosslinked polyurethanes have a significantly increased molecular weight and are therefore regularly no longer soluble in organic solvents.no longer meltable, so that liquefaction, which is essentially irreversible, is only possible through decomposition.

[0030] The inventors propose ranges for the average molar mass of the polyurethane prepolymers which, according to their experience, allow for particularly advantageous process configurations. A preferred method according to the invention is one in which the first and the second polyurethane prepolymer independently possess a weight-average molar mass M. w , measured using GPC, of ​​8.0 × 10 3 up to 10.0 × 10 4 g / mol, more strongly preferred to 1.5 × 10 4 up to 8.0 × 10 4 g / mol, particularly preferably 2.0 × 10 4 up to 6.0 × 10 4 g / mol, exhibit.

[0031] In the process according to the invention, the prepolymer composition is crosslinked, resulting in an adhesive compound comprising crosslinked polyurethanes. In addition to these, the adhesive compound can include any other components of the prepolymer composition and their reaction products. In the simplest case, the resulting crosslinked polyurethanes constitute the adhesive compound. A preferred method according to the invention is one in which the adhesive compound comprises the crosslinked polyurethanes in a combined mass fraction of 30 to 100%, more preferably 40 to 100%, and particularly preferably 50 to 100%, based on the mass of the adhesive compound.

[0032] The components used in the starting compositions are described in more detail below. In this respect, the inventors have succeeded in identifying particularly preferred embodiments and mass fractions for the individual components, with which advantageous polyurethane prepolymers or high-performance pressure-sensitive adhesives can be obtained in the course of the process according to the invention.

[0033] In accordance with industry practice, the mass fractions are specified as combined mass fractions of one or more components, thereby expressing that the mass fraction of the correspondingly formed components taken together fulfills the relevant criteria, with the mass of the respective starting composition serving as the reference system in the absence of other information.

[0034] With regard to the average molar masses of the polyurethane prepolymers to be influenced thereby, a method according to the invention is preferred, wherein the first and / or the second starting composition comprises the one or more diisocyanate compounds in a combined mass fraction of 1 to 30%, more preferably of 2 to 25%, and particularly preferably of 3 to 20%, based on the mass of the starting composition in question.

[0035] Furthermore, higher-grade polyisocyanates can also be used in the starting compositions to adjust the physicochemical properties. However, the inventors believe that the resulting branching of the polyurethane prepolymers should be kept to a minimum.A preferred method according to the invention is one in which the first and / or the second starting composition, particularly preferably the first and the second starting composition, comprise one or more polyisocyanate compounds with three or more isocyanate groups, more preferably in a combined mass fraction of 10% or less, particularly preferably 5% or less, very preferably 3% or less, most preferably 0.5% or less, in each case based on the mass of the starting composition in question; and / or wherein the combined mass fraction of polyisocyanate compounds with three or more isocyanate groups in the starting composition is 10% or less, particularly preferably 5% or less, very preferably 1% or less, in each case based on the mass of the starting composition in question.

[0036] In principle, a large number of suitable diisocyanate compounds are known to those skilled in the art. However, the inventors prefer a process according to the invention in which one or more first and / or second diisocyanate compounds, particularly preferably one or more first and second diisocyanate compounds, are selected from the group consisting of hexamethylene diisocyanate, 1,6-diisocyanato-2,2,4-trimethylhexane, pentamethylene diisocyanate, (S)-ethyl 2,6-diisocyanatohexanoate, (R)-ethyl 2,6-diisocyanatohexanoate, isophorone diisocyanate, 1,1'-methylenebis(4-isocyanatocyclohexane), 4,4'-methylenebis(phenyl isocyanate), toluene-2,4-diisocyanate, naphthylene-1,5-diisocyanate, and meta-tetramethylxylylene diisocyanate.

[0037] The inventors prefer the use of rather short diisocyanate compounds and thus a method according to the invention, wherein one or more first and / or second diisocyanate compounds, particularly preferably one or more first and second diisocyanate compounds, are selected from the group consisting of diisocyanates with 3 to 20, more preferably 4 to 18, particularly preferably 5 to 15, carbon atoms.

[0038] A preferred method according to the invention is one or more, wherein the first and / or second diisocyanate compounds, particularly preferably the first and second diisocyanate compounds, are selected from aliphatic diisocyanates; in particular, the first or second starting composition additionally comprises one or more aromatic polyester diols in a combined mass fraction of at least 50%.

[0039] To obtain an adhesive compound that is advantageous from a sustainability perspective, the inventors propose using bio-based diisocyanate compounds that are advantageously suited to the process according to the invention. A preferred method according to the invention is one in which the one or more first and / or second diisocyanate compounds, and particularly preferably the one or more first and second diisocyanate compounds, are produced from renewable raw materials, the production preferably comprising the conversion of plant biomass.

[0040] The crosslinking of the polyurethane prepolymers in the process according to the invention can, in principle, be carried out arbitrarily and in any manner known to those skilled in the art, e.g., via terminal or chain-bound OH and NCO groups. The term "chain-bound" here, in contrast to "terminal," refers to OH and NCO groups that are not terminal but are present as substituents on atoms that form the part of the polymer main chain running between the chain end links or that form a side chain extending from the main chain, although in the latter case they do not form the end link of the side chain.

[0041] A preferred method, however, is one according to the invention in which at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups. In this method, crosslinking preferably occurs via radicals, particularly radiation-initiated radicals, and most preferably UV-initiated radicals; unlike in the prior art, it thus does not occur, or at least not exclusively, preferably not at all, by reaction with multifunctional isocyanates. Typical polyurethane prepolymers, however, cannot actually be crosslinked via radicals. This is only made possible by the C-C double bonds that are incorporated into the polyurethane prepolymers in the preferred method by the respective diol compounds.The inventors recognized that not only is the presence of C-C double bonds protruding from the chain between the OH groups necessary, but that diol compounds equipped with such C-C double bonds should preferably be those diols that carry only one, i.e., exactly one, of these C-C double bonds in order to enable optimal crosslinking and simultaneously allow for advantageous properties in the crosslinked adhesive, in particular good damping and adhesive properties. A method according to the invention is particularly preferred in that at least one of the first and at least one of the second diol compounds each has exactly one C-C double bond per molecule protruding from the chain between the OH groups.

[0042] For the sake of clarity and readability, diol compounds which have at least one CC double bond per molecule protruding from the chain running between the OH groups are also referred to as "diol compounds A".

[0043] The inventors recognized that, with regard to the crosslinking step and the physicochemical properties that can be adjusted in the crosslinked adhesive, it can also be important not only to use diol compounds A with a C-C double bond protruding from the chain between the OH groups, but also to include at least one other diol compound in the starting composition that differs from the aforementioned diol compounds. This other diol compound allows the concentration of units derived from diol compounds with C-C double bonds in the polyurethane prepolymers to be controlled, thus ultimately controlling the concentration of C-C double bonds. The person skilled in the art understands that the expression "diol compound different from the aforementioned diol compounds" means that the other diol compounds do not fall under the definition of diol compounds A.Two different diol compounds, each of which is, for example, diol A with one C-C double bond in each molecule protruding from the chain between the OH groups, will not, according to the present invention, represent one diol compound A and another diol compound, but rather two different diol compounds A. Accordingly, the other diol compounds can be defined, in particular, by the fact that they do not contain a C-C double bond in the molecule protruding from the chain between the OH groups. For the sake of clarity and readability, diol compounds that do not have a C-C double bond protruding from the chain between the OH groups will also be referred to as "diol compounds B" in the following.

[0044] The polyurethanes obtained in process step d), as well as the pressure-sensitive adhesive containing these polyurethanes and produced according to the inventive process, are cross-linked. Those skilled in the art understand that this means the polyurethane prepolymers have been at least partially cross-linked as a result of process step d), which is mandatory according to the invention. In accordance with the skilled person's understanding, this does not exclusively require achieving the theoretically maximum possible degree of cross-linking in the sense of complete cross-linking of the pressure-sensitive adhesive. Rather, any cross-linking that occurs during process step d), in accordance with the above-defined specifications, is sufficient, provided it leads to a technically meaningful and usable change in the properties of the prepolymer composition or the pressure-sensitive adhesive obtained therefrom.

[0045] According to the inventors, a particular advantage of the crosslinking process preferred with regard to the use of diols A arises from the fact that no terminal hydroxyl groups are required for the subsequent crosslinking. This makes it possible to use monofunctional alcohols or isocyanates in the starting materials in addition to the diols and diisocyanates. These monofunctional building blocks terminate the polymer chains obtained by polymerization and thus advantageously allow for efficient adjustment of the desired average molar mass. Furthermore, polyurethane prepolymers can be obtained by using these monofunctional compounds, which have neither hydroxyl nor isocyanate groups at their ends, which is particularly advantageous with regard to the storage stability of the polyurethane prepolymers. Accordingly, a process according to the invention is preferred.wherein at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, and wherein the first and / or second, more preferably the first and the second starting composition, comprise one or more monofunctional compounds selected from the group consisting of monofunctional alcohols and monofunctional isocyanates, more preferably in a combined mass fraction of 0.1% or more, particularly preferably 1% or more, most preferably 3% or more, in each case based on the mass of the starting composition in question, and / or in a combined amount of substance in the range of 0.5*[TF] to 1.5*[TF], more preferably in the range of 0.8*[TF] to 1.2*[TF], particularly preferably in the range of 0.95*[TF] to 1.05*[TF],where [TF] is the combined amount of substance of the terminal OH groups or isocyanate groups of the polyurethane prepolymers, and where [TF] can be determined, for example, by measurement on reference samples or estimated using typical simulation methods to adjust this feature.

[0046] According to the inventors, the diol compounds A should preferably be designed to be rather short in order to obtain particularly advantageous polyurethane prepolymers or advantageous crosslinked pressure-sensitive adhesives. This allows these diol compounds not only to incorporate the double bonds required for crosslinking into the polyurethane prepolymers, but also to achieve a relatively high density of urethane groups in the polyurethanes. The high density of structurally comparatively rigid functional groups and the formation of hydrogen bonds increase the cohesion of the pressure-sensitive adhesive, which benefits its adhesive properties.In this context, a method according to the invention is preferred, wherein at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, and wherein these diol compounds are selected from the group consisting of diols with 4 to 60, more preferably 5 to 30, and particularly preferably 6 to 10, carbon atoms. A further or alternative preferred method according to the invention is preferred, wherein at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, and wherein these diol compounds are selected from the group consisting of diols with a molar mass in the range of 70 to 750 g / mol, more preferably in the range of 100 to 500 g / mol, and particularly preferably in the range of 140 to 250 g / mol.

[0047] A particularly preferred method according to the invention is one in which at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, and wherein these diol compounds are selected from the group consisting of diols with exactly one C-C double bond per molecule. A further or alternative preferred method according to the invention is one in which at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, and wherein these compounds are selected from the group consisting of diols with at least one, more preferably exactly one, terminal C-C double bond per molecule.Particularly preferred is also or alternatively a method according to the invention, wherein at least one of the first and at least one of the second diol compounds each have at least one CC double bond per molecule protruding from the chain running between the OH groups, and wherein these diol compounds are selected from the group consisting of aliphatic diols.

[0048] According to the inventors, suitable diols with at least one C-C double bond protruding from the chain between the OH groups are (meth)acrylates, with monomeric compounds being preferred. A preferred method according to the invention is wherein at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule protruding from the chain between the OH groups, and wherein these diol compounds are selected from the group consisting of acrylates and methacrylates. A particularly preferred method according to the invention is wherein at least one of the first and at least one of the second diol compounds are selected from the group consisting of dihydroxyalkyl(meth)acrylates.A particularly preferred method according to the invention is wherein at least one of the first and at least one of the second diol compounds is 2,3-dihydroxypropyl methacrylate.

[0049] Essentially independent of the specific selection of the diol compounds A, a method according to the invention is preferred, wherein at least one of the first and at least one of the second diol compounds each have at least one CC double bond per molecule protruding from the chain running between the OH groups, and wherein the starting composition in question comprises these diol compounds in a combined mass fraction in the range of 0.05 to 20%, more preferably in the range of 0.1 to 6%, and particularly preferably in the range of 0.3 to 3.5%, in each case based on the mass of the starting composition in question.

[0050] With regard to crosslinking kinetics and the resulting adhesive properties, the inventors consider it preferable to largely avoid the use of monomeric diols possessing multiple groups that can be converted during radical crosslinking. In particular, it is advantageous to keep the content of monomeric diol compounds with two or more C-C double bonds per molecule protruding from the chain between the OH groups, especially with two or more terminal C-C double bonds, rather low. A preferred method according to the invention is one in which the first and / or the second, and in particular the first and the second, starting composition comprises one or more diol compounds, more preferably monomeric diol compounds, with two or more C-C double bonds per molecule protruding from the chain between the OH groups.more preferably in a combined mass fraction of 30% or less, particularly preferably of 20% or less, most preferably of 10% or less, in each case based on the mass of the starting composition in question, and / or wherein the combined mass fraction of diol compounds with two or more C-C double bonds per molecule projecting from the chain between the OH groups in the starting composition is 10% or less, particularly preferably 5% or less, most preferably 1% or less, in each case based on the mass of the starting composition in question.

[0051] It can be seen as an advantage of the preferred crosslinking method that it is very flexible with regard to the aforementioned additional diols B, i.e., the diol compounds without a C-C double bond protruding from the chain between the OH groups, and thus allows for flexible adaptation of the physicochemical properties to the respective required profile. Those skilled in the art understand that the additional diol compounds B differ from the diol compounds A with at least one C-C double bond protruding from the chain between the OH groups in that they do not contain a C-C double bond protruding from the chain between the OH groups. However, these are not necessarily compounds that contain no unsaturated components at all and are therefore saturated diol compounds. The diol compounds B can, for example,comprise aromatic components and are therefore free of localized C-C double bonds. A preferred method according to the invention is thus one in which at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain between the OH groups, wherein the first and / or second starting composition, in particular the first and the second starting composition, comprise further diol compounds, and wherein the further diol compounds are selected from the group consisting of diols without a localized C-C double bond projecting from the chain between the OH groups.

[0052] In principle, these additional diol compounds, or diol compounds B, can be either relatively short molecules, so-called chain extenders, or oligomeric or polymeric diols, and these can also be mixed. According to the inventors, the use of oligomeric and polymeric diol compounds B is particularly advantageous.For certain applications, a method according to the invention is preferred in this context, wherein at least one of the first and at least one of the second diol compounds each have at least one CC double bond per molecule projecting from the chain running between the OH groups, wherein the first and / or second starting composition, in particular the first and the second starting composition, comprise further diol compounds B and wherein the further diol compounds B are selected from the group consisting of diols with 5 to 600, more preferably 8 to 350, particularly preferably 10 to 250, carbon atoms.However, a method according to the invention is particularly preferred, wherein at least one of the first and at least one of the second diol compounds each have at least one CC double bond per molecule protruding from the chain running between the OH groups, wherein the first and / or second starting composition, in particular the first and the second starting composition, comprise further diol compounds B and wherein the further diol compounds B are selected from the group consisting of diols with a number-average molar mass M. n , measured by GPC as described herein, in the range of 200 to 6000 g / mol, more preferably in the range of 500 to 4500 g / mol, particularly preferably in the range of 1000 to 3000 g / mol.

[0053] Particularly preferred in the case of oligomeric or polymeric further diol compounds B are those compounds which exist as amorphous or semicrystalline substances. A preferred method according to the invention is wherein at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule projecting from the chain running between the OH groups, wherein the first and / or second starting composition, in particular the first and the second starting composition, comprise further diol compounds B, and wherein the further diol compounds B are selected from the group consisting of amorphous or semicrystalline, more preferably amorphous, diol compounds.

[0054] Essentially independent of the specific selection of the further diol compounds, a process according to the invention is preferred, wherein at least one of the first and at least one of the second diol compounds each have at least one CC double bond per molecule projecting from the chain running between the OH groups, wherein the first and / or second starting composition, in particular the first and the second starting composition, comprise further diol compounds B, and wherein the first and second starting composition each comprise the further diol compounds B in a combined mass fraction in the range of 50 to 99%, more preferably in the range of 55 to 97%, and particularly preferably in the range of 60 to 95%, in each case based on the mass of the starting composition.

[0055] Analogous to the above statements regarding polyisocyanates, higher-grade polyols can also be used in the starting compositions to adjust the physicochemical properties. However, in the inventors' opinion, the resulting branching of the polyurethane prepolymers should also be kept to a minimum in this case.A preferred method according to the invention is wherein the first and / or the second starting composition, in particular the first and the second starting composition, each comprise one or more polyol compounds with three or more hydroxy groups, more preferably in a combined mass fraction of 30% or less, particularly preferably 15% or less, very preferably 3% or less, most preferably 0.5% or less, based on the mass of the starting composition in question, and / or wherein the combined mass fraction of polyol compounds with three or more hydroxy groups in the starting compositions is each 10% or less, particularly preferably 5% or less, very preferably 1% or less, based on the mass of the starting composition in question.

[0056] According to the inventors, it is advantageous if the difference between the first and the second polyurethane prepolymer is established at least via the diol compounds. A preferred method according to the invention is one in which at least one of the first and / or second diol compounds differs from the diol compounds of the other starting composition. This difference can, in principle, be of a chemical nature, by which those skilled in the art understand that one of the first and / or second diol compounds is one that would have to be designated differently from each diol compound of the other starting composition.On the other hand, the difference can also consist in the fact that at least one of the first and / or second diol compounds is chemically identical in the first and second starting compositions and would therefore be referred to by a person skilled in the art with the same designation, but the two diol compounds in question have a different, in particular number-average, molar mass. However, a process according to the invention is more preferred in which at least one of the first and / or second diol compounds is chemically different from the diol compounds of the respective other starting composition.

[0057] The inventors have discovered that, with regard to the efficiency of crosslinking the polyurethane prepolymers, it is advantageous if the difference between the first and second polyurethane prepolymers is not, or at least not significantly, expressed via the diol compounds A with at least one C-C double bond protruding from the chain running between the OH groups. A preferred method according to the invention is therefore one in which at least one of the first and at least one of the second diol compounds each have at least one C-C double bond per molecule protruding from the chain running between the OH groups, and these diol compounds of the first and second starting compositions are at least chemically identical.The person skilled in the art understands that, therefore, the first and the second starting compositions contain the same diol compounds A with regard to their chemical nature, although these may be present in different quantities.

[0058] According to the inventors, it is particularly advantageous with regard to the chemical resistance of the pressure-sensitive adhesive if at least one of the first or second diol compounds is a polyester diol. As the inventors further recognized, it is also advantageous with regard to the chemical resistance of the pressure-sensitive adhesive if the other starting composition does not contain any polyester diol or contains only minor amounts of polyester diols. In the process according to the invention, the first or second starting composition thus comprises one or more polyester diols in a combined mass fraction of at least 50%, preferably at least 75%, particularly preferably at least 85%, and particularly preferably at least 90%, and the other starting composition comprises polyester diols in a combined mass fraction of at most 5%, preferably at most 0.5%, or is—particularly preferably—free of polyester diols.

[0059] The inventors further recognized that, with regard to the shock resistance of the adhesive compound, it is advantageous to combine the polyester diol(s) of one starting composition with one or more polybutadiene diols and / or polycarbonate diols of the other starting composition. A preferred method according to the invention is therefore one wherein - the first or second starting composition comprises one or more polyester diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition comprises polyester diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or - particularly preferably - is free of polyester diols; and - the starting composition which comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols, comprises one or more polybutadiene diols and / or polycarbonate diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition which comprises polybutadiene diols and / or polycarbonate diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or - particularly preferably - is free of polybutadiene diols and polycarbonate diols.

[0060] The polybutadiene diols and polycarbonate diols are preferably diol compounds B, i.e. preferably do not contain a CC double bond protruding from the chain running between the OH groups.

[0061] Those skilled in the art understand that "polyester diols" here do not refer to polycarbonate diols, although polycarbonate diols also generally belong to the class of polyester diols. In this embodiment, at least one polyester diol is preferably an aromatic polyester diol; it is particularly preferred that one or more of the polyester diols be aromatic polyester diols.

[0062] A method according to the invention is particularly preferred, wherein - the first or second starting composition comprises one or more polyester diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition comprises polyester diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or - particularly preferably - is free of polyester diols; and The starting composition comprising polyester diols in a combined mass fraction of at most 5% or being free of polyester diols, comprising one or more polybutadiene diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition comprising polybutadiene diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or – particularly preferably – being free of polybutadiene diols.

[0063] A method according to the invention is also particularly preferred, wherein - the first or second starting composition comprises one or more polyester diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition comprises polyester diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or - particularly preferably - is free of polyester diols; and the starting composition which comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols, comprises one or more polycarbonate diols in a combined mass fraction of at least 50%, more preferably at least 75%, particularly preferably at least 85%, and in particular at least 90%, and the other starting composition which comprises polycarbonate diols in a combined mass fraction of at most 5%, more preferably at most 0.5%, or - particularly preferably - is free of polycarbonate diols.

[0064] To obtain an adhesive compound that is advantageous from a sustainability perspective, the inventors also propose, with regard to the diols used, that bio-based compounds can be employed that are advantageously suited to the process according to the invention and that can be combined, in particular, preferably with bio-based diisocyanates. A preferred method according to the invention is one in which the first diol compounds and / or the second diol compounds, preferably both the first and second diol compounds, are produced from renewable raw materials, the production preferably involving the conversion of plant biomass.

[0065] The inventors have succeeded in identifying an advantageous process for the production of polyurethane prepolymers, which can be carried out both in a solvent and solvent-free, with the former being preferred. When using solvents, a process according to the invention is preferred, wherein the polyurethane prepolymers can be produced by reacting the respective starting composition in a solvent, wherein the solvent is selected from the group consisting of ketones, for example acetone or butan-2-one, esters, for example ethyl acetate, ethers, amides, hydrocarbons, for example gasoline 60 / 90, toluene, halogenated hydrocarbons, and mixtures of these solvents.

[0066] Regardless of the use of a solvent, a method according to the invention is preferred, wherein the polyurethane prepolymers can be produced by reacting the respective starting composition at a temperature of 0 to 120 °C, more preferably from 10 to 100 °C, particularly preferably from 20 to 80 °C.

[0067] According to the inventors, it is advantageous in many cases to provide a catalyst for the production of polyurethane prepolymers. An exemplary process according to the invention is described in which the polyurethane prepolymers can be produced by reacting the respective starting composition in the presence of a catalyst, wherein the catalyst is selected from the group consisting of organobismuth compounds, organotin compounds, organozirconium compounds, organozinc compounds, tertiary amine compounds, morphine-containing compounds, iron-containing salts, and potassium-containing salts.

[0068] For the crosslinking of the polyurethane prepolymers in process step d), typical initiator systems known to those skilled in the art for radical crosslinking, such as that used, for example, in (meth)acrylate-based systems, can advantageously be used. In the inventor's opinion, radiation-based curing is particularly advantageous in this respect. A process according to the invention is preferred in that the first and / or the second, in particular the first and the second, starting composition comprises one or more diol compounds, more preferably monomeric diol compounds, with one or more, preferably exactly one, C-C double bonds per molecule protruding from the chain running between the OH groups, and wherein the crosslinking of the polyurethane prepolymers in the prepolymer composition orThe reaction of the prepolymer composition is initiated by radical reaction of the aforementioned C-C double bonds by one or more initiator compounds, wherein the one or more initiator compounds are selected from the group consisting of radiation-activated initiators, thermally-activated initiators, and redox initiators; more preferably, they are selected from the group consisting of thermally-activated and radiation-activated initiators; and particularly preferably, they are radiation-activated initiators. A process such as this is preferred, wherein the one or more initiator compounds are selected from the group consisting of α-hydroxyketones, α-alkoxyketones, α-aminoaryl ketones, diaryl ketones, azo compounds, acylphospin oxides, organic or inorganic peroxides, camphorquinones, and camphorquinone derivatives.Preferably, or alternatively, a process is employed in which one or more initiator compounds are used in a combined mass fraction in the range of 0.001 to 5%, more preferably in the range of 0.05 to 1%, based on the mass of the polyurethane prepolymers in the prepolymer composition. Those skilled in the art will understand that these are processes according to the invention, wherein the prepolymer composition comprises the corresponding initiator compounds.

[0069] The inventors have identified temperature ranges that yield particularly advantageous results in crosslinking. A preferred method, when using thermally activated initiators, involves crosslinking the polyurethane prepolymers in the prepolymer composition at a temperature in the range of 40 to 300 °C, more preferably in the range of 50 to 280 °C, and particularly preferably in the range of 60 to 150 °C. Alternatively, a preferred method, when using radiation-activated initiators, involves crosslinking the polyurethane prepolymers in the prepolymer composition at a temperature in the range of -10 to 40 °C, more preferably in the range of 10 to 30 °C, and particularly preferably in the range of 20 to 25 °C.

[0070] According to the inventors, it is particularly advantageous if the produced pressure-sensitive adhesive also comprises resins, especially adhesive resins. A preferred method according to the invention is one in which the pressure-sensitive adhesive comprises one or more resins, preferably in a combined mass fraction of 70% or less, particularly preferably 60% or less, and most preferably 50% or less, based on the mass of the pressure-sensitive adhesive. Examples of such adhesive resins include, among others, hydrocarbon resins, for example, polymers based on unsaturated C5 or C9 monomers; terpene phenolic resins; and polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene. Aromatic resins such as coumaron-indene resins or resins based on styrene or α-methylstyrene, as well as rosin and its derivatives, for example disproportionate, dimerized or esterified resins, for example reaction products with glycol, glycerol or pentaerythritol.

[0071] It can be seen as an advantage of the process according to the invention that, in addition to resins, it is also open to the presence of further components that can be added to the prepolymer composition and are accordingly contained in the pressure-sensitive adhesive. This advantageously allows the physicochemical properties of the pressure-sensitive adhesive to be specifically adapted to the respective application requirements. An exemplary process according to the invention is one in which the pressure-sensitive adhesive comprises one or more further components, wherein the further components are selected from the group consisting of rheology additives, stabilizers, antioxidants, and colorants, wherein the combined mass fraction of the further components is more preferably in the range of 0.1 to 30%, more preferably in the range of 0.5 to 20%, and most preferably in the range of 1 to 20%, based on the mass of the pressure-sensitive adhesive.

[0072] A special case of the additional components used to adjust the properties of the pressure-sensitive adhesive are insoluble fillers that can be added to the prepolymer composition to obtain a filled, crosslinked pressure-sensitive adhesive after crosslinking. These are, for example, particulate fillers with a mean particle diameter (D50) of 5 µm or more, preferably 10 µm or more, and particularly preferably 20 µm or more, which are insoluble in the prepolymer composition and therefore exist as a dispersion within it; or macroscopic fillers, such as fibers. Preferably, the insoluble fillers are selected from the group consisting of particulate fillers.Particularly preferred are insoluble fillers selected from the group consisting of expandable hollow polymer spheres, non-expandable hollow polymer spheres, solid polymer spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres, solid carbon spheres, and powdered inorganic compounds. Suitable insoluble fillers also include, for example, fibers, fabrics, platelets, and rods made of materials insoluble in the prepolymer composition. Due to their sometimes macroscopic dimensions and their lack of solubility, these generally have no significant influence on the relationships between the prepolymer composition and the crosslinking chemistry disclosed above.Accordingly, these insoluble fillers are not considered part of the prepolymer composition within the scope of the present invention and are therefore not taken into account when calculating mass fractions relative to the mass of the prepolymer composition. Rather, within the scope of the present invention, it is defined that the addition of insoluble fillers to a prepolymer composition results in a filled prepolymer composition. In this case, it is therefore a process according to the invention, wherein the prepolymer composition is a filled prepolymer composition consisting of: aa.1) the prepolymer composition, and aa.2) one or more insoluble fillers, wherein the combined mass fraction of the insoluble fillers is preferably in the range of 0.1 to 20%, particularly preferably in the range of 0.5 to 15%, and most preferably in the range of 1 to 10%, based on the mass of the prepolymer composition.

[0073] The invention also relates to a method for producing an adhesive tape, comprising the process steps of the inventive method for producing an adhesive compound, as well as, before or during, preferably before, process step d) the process step: d1a) forming a prepolymer layer from the prepolymer composition thus obtained onto a carrier layer or a separating layer.

[0074] The term adhesive tape is clear to those skilled in the art of adhesive technology. Within the scope of the present invention, the term tape refers to all thin, planar structures, i.e., structures with a predominant extension in two dimensions, in particular films, film sections and labels, preferably tapes with extended length and limited width, as well as corresponding tape sections.

[0075] The material application (coating thickness) of the prepolymer composition is preferably in the range of 10 to 1000 g / m². 2 , preferably in the range of 15 to 500 g / m³ 2 , particularly preferably in the range of 20 to 200 g / m³ 2 .

[0076] With a view to achieving the most favorable handling properties, particularly advantageous results are regularly achieved when adhesives produced according to the invention are used as the adhesive layer of a single- or double-sided adhesive tape, which also includes a carrier layer, or when the adhesive layer is arranged on a separating layer, for example a liner, from which the adhesive layer can be easily removed.

[0077] A preferred method according to the invention for producing an adhesive tape is one in which the prepolymer composition is formed on a release layer. A preferred method for producing an adhesive tape is one in which the release layer comprises one or more materials selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, paper, and combinations of these materials. The release material is preferably coated on one or both sides, particularly preferably on both sides, with a release layer, preferably a carbamate or silicone release layer, and particularly preferably a silicone release layer. The silicone release layer is most preferably produced by crosslinking a crosslinkable silicone system comprising one or more polysiloxanes.

[0078] The term carrier layer, in contrast to the release liner, usually refers to the layer of a multi-layer adhesive tape that significantly determines the tape's mechanical and physical properties, such as tensile strength, elongation, insulation, and resilience. Common materials for the carrier layer include woven fabrics, non-woven fabrics, paper, and plastic films, for example, PET films and polyolefin films.

[0079] When using carrier layers, it is often advantageous to employ an adhesion promoter, a so-called primer layer, between the carrier material and the prepolymer composition, or to perform a physical pretreatment of the carrier surface to improve the adhesion of the cross-linked adhesive to the carrier material. In adhesive tapes with a carrier layer produced according to the invention, the adhesive layers can, in turn, be covered with a release liner to enable trouble-free unwinding and to protect the adhesive from contamination. In the case of single-sided adhesive tapes, the carrier can be coated on one side with a release layer, which can be, for example, silicone-, carbamate-, or acrylate-based.

[0080] The person skilled in the art understands that the invention also relates to an adhesive compound which is manufactured or can be manufactured using a method according to the invention for manufacturing an adhesive compound.

[0081] Based on the inventive methods for producing an adhesive compound, products obtainable by this method are also disclosed within the scope of the invention. Thus, an adhesive tape comprising an adhesive compound producible by a method according to the invention is also disclosed, wherein the adhesive compound is arranged as an adhesive layer on a carrier layer or a release layer.

[0082] The invention also relates to the use of an adhesive compound, producible by means of a method according to the invention, to improve the shock behavior of an adhesive tape equipped with the adhesive compound, in particular a chemical-resistant or chemical-proof adhesive tape. Examples 1. Measurement and Testing Methods Method 1 - Determination of Molar Mass

[0083] The specifications of the numerical or weight-average molar mass (M n or M wThe values ​​in this document refer to the well-known determination by gel permeation chromatography (GPC). The determination is performed on 100 µl of clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1 vol% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C.

[0084] A PSS-SDV type column, 5 µm, 10 is used as a pre-column. 3 Å, 8.0 mm * 50 mm (Specifications here and below in the order: type, particle size, porosity, inner diameter * length; 1 Å = 10 -10 m) is used. For separation, a combination of columns of type PSS SDV, 5 µm, 10 is used. 3 Å and 10 5 Å and 10 6Columns measuring 8.0 mm x 300 mm (Polymer Standards Service; detection via Shodex RI71 differential refractometer) were used. The flow rate was 1.0 ml per minute. Calibration was performed using the commercially available ReadyCal kit Poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz, so that the data are given in polystyrene mass equivalents. Method 2 - Measurement of initial adhesive strength

[0085] A 2 cm wide strip of adhesive tape is applied to the test plate by double-rolling it five times with a 4 kg roller. The test plate is then clamped directly into the machine, and the adhesive strip is peeled off at its free end using a tensile testing machine at a peel angle of 180° and a speed of 300 mm / min. The force required for peeling is measured using a tensile testing device. The measurement results are averaged over three measurements and normalized to the width of the strip, then expressed in N / cm. The test plates are polished ASTM steel plates with a thickness of 2 mm. Method 3 - Measurement of static shear strength

[0086] A 1.3 cm wide strip of self-adhesive tape is bonded to a polished steel plate over a length of 2 cm using a 2 kg roller by double-rolling it twice. The plates are equilibrated for 30 minutes under test conditions, but without a load. Then, the test weight (1 kg) is attached, creating a shear stress parallel to the bonded area, and the time in minutes until the bond fails is measured. If a holding time of 10,000 minutes is reached, the test is terminated before the adhesive bond fails. Method 4 - Shock test (DuPont test) on polycarbonate (PC)

[0087] Transfer tapes were produced for the impact resistance test. The sample was cut into a square, frame-shaped geometry using a laser cutter (outer dimensions: 33 mm × 33 mm; web width: 2 mm; inner dimensions (window cutout): 29 mm × 29 mm). The sample was then bonded to a polycarbonate (PC) window (35 mm × 35 mm, thickness: 3 mm). A polycarbonate frame (outer dimensions: 45 mm × 45 mm; web width: 10 mm; inner dimensions (window cutout): 25 mm × 25 mm; thickness: 3 mm) was bonded to the other side of the transfer tape. The bonded area is 248 mm². 2 The bonding process involves aligning the geometric centers and diagonals (corner-to-corner). The bond is then pressed with 248 N for 5 seconds and stored for 24 hours.

[0088] The assembly consisting of a PC frame, adhesive tape, and PC window is clamped into a sample holder so that the protruding edges of the frame lie flat. The assembly is horizontally aligned. The window is attached below the PC frame, held in place only by the adhesive bond ("free-floating"). The sample holder is then inserted into the designated frame of the DuPont Impact Tester. The impact head (weight: 150 g) is positioned so that its circular impact geometry, with a diameter of 24 mm, rests centrally and flush on the surface of the PC window that is freely accessible from above. A weight, guided by two rods, is dropped vertically from a height of 5 cm. The drop height is increased in 5 cm increments until the adhesive bond is broken by the impact energy and the PC window detaches from the PC frame. Five measurements are taken for each sample, and the average is then determined.

[0089] To ensure comparability between different samples, the energy (E) is calculated as follows: E[J]=height[m]*mass weight[kg]*9.81 kg / m*s2. Method 5 - Shock test (DuPont test) on steel

[0090] Transfer tapes were produced for the impact resistance test. The sample was cut into a circular shape (diameter: 21 mm) using a laser cutter. The sample was then bonded to a steel window (diameter: 21 mm; thickness: 3 mm). A steel frame (outer width: 40 mm × 40 mm; inner diameter (window cutout): 9 mm; thickness: 3 mm) was bonded to the other side of the transfer tape. The bonded area is 282 mm². The bonding was done so that the geometric centers were aligned. The bond was then pressed with 248 N for 5 seconds and stored for 24 hours.

[0091] The assembly of steel frame, adhesive tape, and steel window is clamped into a sample holder so that the protruding edges of the frame lie flat. The assembly is horizontally aligned. The window is attached below the steel frame, held only by the adhesive bond ("free-floating"). The sample holder is then inserted into the designated frame of the DuPont Impact Tester. The impact head (weight: 150 g) is positioned so that its circular impact geometry, with a diameter of 4 mm, rests centrally and flush on the surface of the steel window that is freely accessible from above. A weight, guided by two rods, is dropped vertically from a height of 5 cm. The drop height is increased in 5 cm increments until the adhesive bond is broken by the impact energy and the PC window detaches from the PC frame. Five measurements are taken for each sample, and the average is then determined.

[0092] To ensure comparability between different samples, the energy (E) is calculated as follows: E[J]=height[m]*mass weight[kg]*9.81 kg / m*s2. Method 6 - Determination of chemical resistance

[0093] To assess chemical resistance, the adhesive strength on ASTM steel is compared before and after treatment with various chemicals.

[0094] A 0.5 cm wide strip of adhesive tape is bonded to an ASTM test plate by double-rolling it five times with a 4 kg roller. The resulting bonds are stored for 24 hours under standard climate conditions (air, 23 °C, 50% relative humidity) and then placed in a sealed box with the test chemicals, ensuring complete coverage. The box is then stored in a water bath at 60 °C for 72 hours. Test chemical 1: Oleic acid with a purity of > 85% Test chemical 2: Isopropanol / water 70 / 30 (by weight)

[0095] After the storage period, the boxes are removed from the water bath, the samples are carefully cleaned with a cloth and conditioned for 2 hours under standard climate conditions.

[0096] To determine the adhesive strength (under standard climate conditions – air, 23 °C, 50% relative humidity), the test plate was clamped, and the self-adhesive strip was peeled off at its free end using a tensile testing machine at a peel angle of 180° and a speed of 300 mm / min. The force required for this was determined using a tensile testing device. The measurement results were averaged over three measurements and normalized to the width of the strip and reported in N / cm. Based on these results, the chemical resistance was categorized as follows, using the initial adhesive strength described above as a reference. Table 1: Assessment of chemical resistance Chemical resistance assessment observation A After chemical treatment, the adhesive tape showed an adhesive strength of > 60% compared to the reference. B After chemical treatment, the adhesive tape showed an adhesive strength of > 30% compared to the reference. C The adhesive tape came loose from the steel plate. 2. Raw materials used Table 2: Raw materials used Trade name Chemical name / description Manufacturer / Supplier Baycoll® AD 2047 Polyesterdiol Covestro Desmophen® C1200 Polycarbonate diol Covestro Eternacoll® PH200D Polycarbonate diol UBE Corporation Krasol® LBH 2000 Hydroxyl-terminated polybutadiene Cray Valley Glyceryl monomethacrylate (GMMA) 2,3-Dihydroxypropyl methacrylate (CAS:5919-74-4); Diol abcr GmbH HDI Hexamethylene diisocyanate (CAS: 822-06-0) Sigma Aldrich IPDI Isophorone diisocyanate (CAS: 4098-71-9) Sigma Aldrich Coscat® 83 bismuth trisneodecanoate; catalyst story acetone solvent Sigma Aldrich 2,2-Dimethoxy-2-phenylacetophenone (DMPA) photoinitiator; CAS:24650-42-8 Sigma Aldrich 3. Production of polyurethane prepolymers

[0097] The polyurethane prepolymers were produced using a solvent-based process starting from the components listed in Table 2.

[0098] The polyurethane prepolymer was prepared by weighing the solvent, all diol compounds, and any additional polyols and catalyst into a reaction vessel. The mixture was homogenized using a mechanical laboratory stirrer under an inert gas atmosphere. The diisocyanate(s) were added, and the mixture was stirred for 1.5 h at room temperature under an inert gas atmosphere. The mixture was then stored in a warming oven at 40 °C for 48 h to allow for complete reaction. Table 3 - Prepolymer I, Mw: 24,900 raw material Mass used [g] Baycoll AD 2047 50,1 GMMA 0,67 IPDI 2,94 HDI 2,21 Coscat 83 0,08 acetone 24,0 Table 4: Prepolymer II, Mw: 42,200 raw material Mass used [g] Desmophen C 1200 61,8 GMMA 0,82 IPDI 7,25 Coscat 83 0,12 acetone 30 Table 5 - Prepolymer III, Mw: 40,800 raw material Mass used [g] Eternacoll PH200D 58,6 GMMA 0,80 IPDI 7,06 Coscat 83 0,10 acetone 35,0 Table 6 - Prepolymer IV, Mw: 49,500 raw material Mass used [g] Krasol LBH 2000 62,4 GMMA 0,30 IPDI 4,36 Coscat 83 0,12 acetone 30,0 Table 7 - Prepolymer V, Mw: 19,800 raw material Mass used [g] Desmophen C 1200 75,2 GMMA 0,30 HDI 4,36 Coscat 83 0,12 acetone 20,0 Table 8 - Prepolymer VI, Mw: 14,100 raw material Mass used [g] Desmophen C 1200 75,3 GMMA 0,64 HDI 3,96 Coscat 83 0,12 acetone 20,0 Table 9 - Prepolymer VII, Mw: 8,200 raw material Mass used [g] Baycoll AD 2047 75,8 GMMA 0,30 HDI 3,78 Coscat 83 0,12 acetone 20,0 4. Production of polyurethane pressure-sensitive adhesives

[0099] The polyurethane prepolymers prepared according to section 3 were each mixed in the mixing ratios listed in Table 10 and the photoinitiator was added (Examples 1-13). For counterexamples 1-4, only the respective polyurethane prepolymer was mixed with the photoinitiator.

[0100] The mixture was homogenized for at least 5 minutes. To produce an adhesive tape, the mixture was coated onto a substrate of etched PET film or a silicone-release-coated PET liner using a laboratory coating table. The solvent was evaporated in a forced-air oven at 80 °C. The dried films were covered with siliconized PET film. The uncrosslinked films were cured with a UV source matched to the initiator (dose: 1800–2400 mJ / cm²). 2 , UV-A) irradiated. Adhesive, cross-linked films with a layer thickness of 45-55 µm were obtained. Table 10: Compositions of the examples Example Prepolymer 1 Prepolymer 2 DMPA Nr. Designation Mass [g] Designation Mass [g] [g] 1 (See below) Prepolymer I 50 - - 0,08 2 (See below) Prepolymer II 50 - - 0,08 3 (See below) Prepolymer III 50 - - 0,08 4 (See below) Prepolymer IV 50 - - 0,08 5 Prepolymer I 30 Prepolymer V 2,92 0,05 6 Prepolymer I 30 Prepolymer V 6,56 0,05 7 Prepolymer I 30 Prepolymer VI 2,92 0,05 8 Prepolymer I 30 Prepolymer VI 6,56 0,05 9 Prepolymer I 30 Prepolymer II 3,33 0,06 10 Prepolymer I 30 Prepolymer II 7,50 0,07 11 Prepolymer I 30 Prepolymer II 16,2 0,07 12 Prepolymer I 30 Prepolymer III 3,58 0,06 13 Prepolymer I 30 Prepolymer III 8,03 0,07 14 Prepolymer I 30 Prepolymer III 15,8 0,07 15 Prepolymer I 30 Prepolymer VII 2,92 0,05 16 Prepolymer I 30 Prepolymer IV 3,33 0,05 17 Prepolymer I 30 Prepolymer IV 7,50 0,05 Cf. = comparative experiment

[0101] The specified mass refers to the amount of the respective prepolymers in solution.

[0102] The adhesive tapes produced according to the above description were tested for their properties using the methods described above. The results obtained are summarized in Table 11. Table 11: Test results Example Adhesive strength [N / cm] Shear strength [min] Shock(PC) [J] Shock(steel) [J] Chemical resistance Nr. IPA / H2O oleic acid 1 (See below) 3,8 8963 0,18 0,10 B A 2 (See below) 0,8 1236 0,52 0,12 C B 3 (See below) 2,4 10000 0,52 0,10 C B 4 (See below) 1,93 10000 0,17 0,20 A C 5 5,3 8343 0,37 0,61 A A 6 6,5 5089 0,47 0,52 A A 7 5,4 7328 0,29 0,49 A A 8 7,3 1911 0,42 0,56 A A 9 3,8 10000 0,44 0,15 B A 10 3,9 10000 0,52 0,15 B A 11 4,6 10000 0,96 0,15 B A 12 3,5 10000 0,37 0,15 B A 13 4,1 10000 0,52 0,29 B A 14 4,8 3570 0,88 0,15 B A 15 5,0 10000 0,25 0,42 A A 16 2,5 10000 0,37 0,22 A A 17 2,7 10000 0,47 0,15 A A Cf. = comparative experiment

Claims

[1] Method for producing an adhesive compound, comprising the process steps: a) Production of a first polyurethane prepolymer by reacting a first starting composition comprising i) one or more first diisocyanate compounds; ii) one or more first diol compounds; b) Production of a second polyurethane prepolymer by reacting a second starting composition comprising iii) one or more second diisocyanate compounds; iv) one or more second diol compounds; wherein at least one of the first and / or second diisocyanate compounds differs from the diisocyanate compounds of the other starting composition; and / or wherein at least one of the first and / or second diol compounds differs from the diol compounds of the other starting composition; and / or wherein the first and second polyurethane prepolymers differ in their weight-average molar mass by at least 10%, based on the polyurethane prepolymer with the higher molar mass; c) Mixing the two polyurethane prepolymers; and d) Crosslinking the prepolymer composition thus obtained; characterized by that the first or second starting composition comprises one or more polyester diols in a combined mass fraction of at least 50% and the other starting composition comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols. [2] Method according to claim 1, characterized by , that at least one of the first and / or second diol compounds differs from the diol compounds of the other starting composition. [3] Method according to one of claims 1 and 2, characterized bythat at least one diol compound is an aromatic polyester diol. [4] Method according to any one of the preceding claims, characterized by , that the starting composition which comprises polyester diols in a combined mass fraction of not more than 5% or is free of polyester diols, comprises one or more polybutadiene diols and / or one or more polycarbonate diols in a combined mass fraction of at least 50%, and the other starting composition which comprises polybutadiene diols and / or polycarbonate diols in a combined mass fraction of not more than 5% or is free of polybutadiene diols and polycarbonate diols. [5] Method according to claim 4, characterized by, that the starting composition which comprises polyester diols in a combined mass fraction of at most 5% or is free of polyester diols, comprises one or more polybutadiene diols in a combined mass fraction of at least 50% and the other starting composition which comprises polybutadiene diols in a combined mass fraction of at most 5% or is free of polybutadiene diols.