Electrically detachable adhesive tape made from a reactively curable adhesive composition

Abstract

The invention relates to a reactively curable adhesive composition, to a reactively curable adhesive tape, to a bonded assembly, to a method for electrically releasing the bonded assembly and to the use of the adhesive composition or the adhesive tape. The reactively curable adhesive composition comprises at least the following components: a) at least one polymer, and b) at least one polymerizable compound, and c) at least one initiator, and d) at least one electrolyte, the electrolyte preferably being an ionic liquid, and e) at least one organic carbonate additive.

Description

[0001] tesa SE

[0002] Norderstedt

[0003] Electrically removable adhesive tape made from a reactive curing adhesive compound

[0004] The invention relates to a reactively curable adhesive compound, a reactively curable adhesive tape, a bonded composite, a method for electrically releasing the bonded composite and the use of the adhesive compound or the adhesive tape.

[0005] 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. Adhesive tapes offer an alternative to using formless adhesives, which are applied, for example, from a tube. Pressure-sensitive adhesive tapes are especially familiar from everyday life. These tapes use an adhesive compound that remains permanently tacky and adhesive under normal environmental conditions. Such tapes can be applied to a substrate by pressing them on, where they adhere, but can later be removed more or less without leaving any residue.

[0006] However, another type of adhesive tape is also of great importance, particularly for use in industrial manufacturing. These tapes, sometimes also referred to as reactive adhesive tapes, utilize a curable adhesive compound. Such reactive curable adhesives, in their intended state for application, have not yet reached their maximum degree of cross-linking and can be cured by external influences. This process initiates polymerization within the adhesive compound, thereby increasing the degree of cross-linking. As a result, the mechanical properties of the now-cured adhesive change, with particular increases in viscosity, surface hardness, and strength.

[0007] Reactive curing adhesives are known in the art and can have very different chemical compositions. These curing adhesives have in common that the crosslinking reaction can be triggered by external factors, such as energy input, particularly temperature, plasma, or radiation curing, and / or contact with a polymerization-promoting substance, as is the case with moisture-curing adhesives. Recently, there has been increased interest in "debonding-on-demand" functionalities, driven by environmental regulations, end-customer awareness of sustainability, and rising cost pressures in manufacturing. Application scenarios for debonding processes are classified into rework, repair, recycling, and processing aids.

[0008] However, adhesive bonds created using reactive curing adhesive tapes generally exhibit very high bond strengths.

[0009] These adhesive tape solutions are therefore either not removable or not removable without damaging the substrates to which they are bonded and with a very high effort.

[0010] US patent 2024 / 0263044 A1 discloses a reactively curable epoxy-based adhesive containing an ionic liquid with an anion selected from SbFe, PFe, and mixtures thereof. After bonding two substrates, including reactive curing of the adhesive, the bond can be separated with reduced force by applying a voltage of 50 V.

[0011] The present invention aims to provide a reactively curable adhesive and a corresponding reactively curable adhesive tape which, after curing and bonding, can be removed from at least one substrate with less force than in the prior art. The substrate should not be damaged, or only minimally damaged, in the process. This should be possible, in particular, even with temperature-sensitive substrates. At the same time, the adhesive strength of the tape to the substrates to be bonded should not be negatively affected before removal.

[0012] It is an additional task to specify a bonded joint and a method for removing the adhesive bond created by the adhesive compound or the adhesive tape.

[0013] Furthermore, it is an object of the invention to provide a use for the adhesives or adhesive tapes to be provided for bonding two or more substrates.

[0014] The aforementioned problems are solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the further dependent claims and the following descriptions.

[0015] Further objects of the invention - besides those mentioned in the independent claims - are a method for producing the reactively curable adhesive mass according to the invention, a method for producing the reactively curable adhesive tape according to the invention, a method for producing the bonded composite according to the invention.

[0016] All descriptions apply to the reactively curable adhesive compound, the reactive adhesive tape, the bonded composite according to the invention, the method for electrically releasing the composite, the use of the adhesive tape or the adhesive compound according to the invention, and the manufacturing methods according to the invention.

[0017] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments also referred to as preferred. Combinations of two or more of the embodiments hereinafter referred to as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment, which is referred to as preferred to any degree, is combined with one or more further features of other embodiments, which are referred to as preferred to any degree. Thus, the invention encompasses combinations of individual features with one another, including combinations of different levels of preference. For example, the invention encompasses the combination of a first feature designated as "preferred" with a second feature designated as "particularly preferred".The characteristics of preferred adhesive tapes, bonded composites, uses, and methods are derived from the characteristics of preferred adhesives. Furthermore, the characteristics of preferred bonded composites, uses, and methods are derived from the characteristics of preferred adhesive tapes.

[0018] The terms "reactive curing adhesive" and "reactive adhesive" or "curing adhesive" are used synonymously within the scope of the present invention. This applies analogously to a corresponding adhesive layer and a corresponding adhesive tape.

[0019] Furthermore, for the sake of simplicity, the terms without descriptive prefixes, namely "adhesive compound", "adhesive layer" and "adhesive tape", are also used in the description of the invention.

[0020] The reactive curing adhesive according to the invention contains at least the following components

[0021] a) at least one polymer, and b) at least one polymerizable compound, and

[0022] c) at least one initiator, and

[0023] d) at least one electrolyte, wherein the electrolyte is preferably an ionic liquid, and

[0024] e) at least one organic carbonate additive.

[0025] The bonded, hardened adhesive mass can be electrically detached by applying a voltage, thanks to the electrolyte contained within.

[0026] Surprisingly, it has been found that the reactively curable adhesive or the reactive adhesive tape according to the invention, after curing and bonding to the substrates, can be easily and quickly removed electrically by applying a voltage without requiring much force, and that the high bond strength of the adhesive tape to the substrates to be bonded is not negatively affected before removal. Surprisingly, the electrical removal is improved by the addition of organic carbonates, which is evident, among other things, from the lower bond strengths after applying a voltage to the adhesives bonded according to the invention compared to adhesives from the prior art.

[0027] The adhesive tapes according to the invention are also suitable for miniaturized applications, such as those required in the electronics industry. Here, it is increasingly important to create highly precise and space-saving connections between components. The reactive adhesive tape according to the invention is preferably a double-sided tape. For the sake of simplicity, the adhesive tape according to the invention, even in its double-sided embodiments, is referred to as "adhesive tape" within the scope of the present invention.

[0028] In its simplest form, double-sided adhesive tape is a transfer tape, meaning an adhesive tape consisting of a single adhesive layer without a backing layer. However, double-sided adhesive tape can also comprise one or more backing layers, in which case the two outermost layers are adhesive layers, specifically adhesive layers.

[0029] The present invention relates to an adhesive tape which can be in any form, with tape rolls being preferred. The adhesive tape, particularly in roll form, can be produced either as a roll, i.e., wound around itself in the form of an Archimedean spiral, or as adhesive strips, such as those obtained, for example, in the form of blanks or die-cuts. Before cutting or die-cutting, the adhesive tape according to the invention is preferably in roll form. A roll is understood to be an object whose length (extension in the x-direction) is many times greater than its width (extension in the y-direction) and whose width is preferably approximately constant along its entire length.

[0030] The general term "adhesive tape", also synonymously called "adhesive strip", encompasses, within the meaning of this invention, all planar structures, such as films or film sections extended in two dimensions, tapes with extended length and limited width, tape sections and the like, ultimately also die-cut pieces or labels.

[0031] In addition to its longitudinal (x-direction) and lateral (y-direction) dimensions, the adhesive tape also has a thickness (z-direction) that runs perpendicular to both dimensions, with the lateral and longitudinal dimensions being many times greater than the thickness. The thickness is as uniform as possible over the entire surface area of ​​the adhesive tape, defined by its length and width, and preferably exactly uniform within tolerances.

[0032] The above applies analogously to the carrier layer(s) which, as a component of the adhesive tape according to some preferred embodiments, forms a layer in the x and y directions.

[0033] It is understood that the individual layers are arranged on top of each other along the z-direction.

[0034] The reactive curing adhesive compound according to the invention and its components are described in more detail below.

[0035] At least one electrolyte d)

[0036] The adhesive mass contains at least one electrolyte d).

[0037] In the present context, an "electrolyte" is understood to be a chemical compound that is dissociated into ions in the solid, liquid or dissolved state and that moves in a directed manner under the influence of an electric field.

[0038] Preferably, the electrolyte is selected from the group consisting of ionic liquids and metal salts, with ionic liquids being particularly preferred. In particular, the use of one or more ionic liquids as the electrolyte allows the adhesive tape to be easily removed without negatively affecting its adhesive properties. Ionic liquids have the advantage that their components are non-volatile, especially at room temperature. Furthermore, ionic liquids are comparatively heat-stable, non-flammable, and chemically stable.

[0039] Ionic liquids are therefore particularly well suited as electrolytes in the separation process or electrical dissolution process according to the invention.

[0040] When a voltage is applied, the adhesive strength of the adhesive containing the ionic liquid decreases on at least one substrate, resulting in an adhesive separation between the adhesive and the bonded surface of the at least one substrate. This ensures that no or virtually no adhesive tape residue remains on the surface.

[0041] In principle, all ionic liquids are suitable within the scope of the present invention.

[0042] Within the scope of the present invention, ionic liquids are salts that are liquid at 100 °C, preferably at room temperature, i.e., 23 °C. Accordingly, ionic liquids contain anions and cations.

[0043] Such ionic liquids, which are liquid at 100 °C but solid at 23 °C, are preferably made processable by suitable process steps, such as, in particular, and for example, dissolving in a solvent.

[0044] Ionic liquids that are liquid at 23 °C are preferred.

[0045] The anion of the electrolyte, preferably the ionic liquid, is particularly preferred. d) Selected from the group consisting of

[0046] Tetrafluoroborate (BF4), hexafluorophosphate (PF6), and hexafluoroantimonate (SbF6). The PF6 anion is particularly favored. _ .

[0047] Particularly preferably, the adhesive mass according to the invention contains an ionic liquid with PFe" as the anion.

[0048] The cation of the electrolyte can in principle be any cation known to a person skilled in the art, such as in particular metal ions, metal complex ions or organic cations.

[0049] Particularly preferably the electrolyte, preferably the ionic liquid, d) comprises a cation selected from the group consisting of imidazolium-based cations, pyridinium-based cations, pyrrolidinium-based cations, ammonium-based cations, phosphonium-based cations, oxazolium-based cations, guadinium-based cations and thiazolium-based cations.

[0050] Particularly preferred is the cation of the electrolyte, preferably of the ionic liquid, d) selected from the group consisting of imidazolium-based cations, pyridinium-based cations and ammonium-based cations, wherein imidazolium-based cations and pyridinium-based cations are again preferred.

[0051] Surprisingly, this achieves an extremely high reduction in bond strength in reactively curing adhesives by applying a voltage, and thus particularly good electrical removability of the adhesive tape according to the invention. In particular, (re-)removal with these cations is especially fast and leaves no or virtually no adhesive tape residue.

[0052] Imidazolium-based cations are particularly preferred.

[0053] These cations are particularly well-suited because they offer the best electrical detachability. In particular, (re-)detachment with these cations is especially fast, leaving little to no residue.

[0054] The cation selected from the group consisting of 1-ethyl-3-methylimidazolium (EMIM), 1-butyl-3-methylimidazolium (BMIM), 1-hexyl-3-methylimidazolium (HMIM) and 1-octyl-3-methylimidazolium (OMIM) is particularly preferred.

[0055] Again, the preferred cation is selected from the group consisting of

[0056] 1-Butyl-3-methylimidazolium (BMIM), 1-hexyl-3-methylimidazolium (HMIM) and 1-0ctyl-3-methylimidazolium (OMIM).

[0057] The cation selected from the group consisting of 1-hexyl-3-methylimidazolium (HMIM) and 1-octyl-3-methylimidazolium (OMIM) is particularly preferred.

[0058] Surprisingly, this achieves an extremely high reduction in bond strength in reactively curing adhesives by applying a voltage, and thus particularly good electrical removability of the adhesive tape according to the invention. In particular, (re-)removal with these cations is especially fast and leaves no or virtually no residue.

[0059] Preferably the electrolyte is selected from the group consisting of the ionic liquids 1-Ethyl-3-methylimidazolium hexafluorophosphate (EMIM-PFβ ,

[0060] 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PFß,

[0061] 1-Butyl-3-methylimidazolium hexafluoroantimonate (BMIM-SbFß,

[0062] 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIM-PFe and

[0063] 1-Octyl-3-methylimidazolium hexafluorophosphate (OMIM-PFe).

[0064] The electrolyte of the adhesive layer D is particularly preferred if selected from the group consisting of the ionic liquids.

[0065] 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PFe),

[0066] 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIM-PFe) and

[0067] 1-Octyl-3-methylimidazolium hexafluorophosphate (OMIM-PFe).

[0068] The electrolyte of the adhesive layer D is again particularly preferred if selected from the group consisting of the ionic liquids.

[0069] 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIM-PFe) and

[0070] 1-Octyl-3-methylimidazolium hexafluorophosphate (OMIM-PFe).

[0071] Preferably, the adhesive mass contains 0.5 to 25 wt.%, particularly preferably 2 to 22 wt.%, most preferably 3 to 10 wt.%, of electrolytes, preferably ionic liquids, based on the total weight of the adhesive mass.

[0072] With such a preferred or particularly preferred amount of electrolytes, especially ionic liquids, a comparatively rapid electrical removal is made possible, while at the same time the adhesion of the adhesive layer to the adjacent layers, especially at least one substrate, is not negatively affected before removal.

[0073] At least one organic carbonate additive e)

[0074] The adhesive contains at least one organic carbonate additive e).

[0075] An “organic carbonate additive” is understood to be an organic compound that is present as an additive in addition to the polymer a), the electrolyte d) and the substances b) and c) involved in the curing process.

[0076] Preferably, the reactively curable adhesive contains at least 0.5 wt.% and / or up to 20 wt.% of organic carbonate additives e). This also includes a mixture of two or more different carbonate additives. Particularly preferably, the reactively curable adhesive contains 0.5 wt.% to 20 wt.%, and most preferably 2 wt.% to 17 wt.%, of organic carbonate additives e).

[0077] According to particularly preferred embodiments of the invention, the reactively curable adhesive mass contains 4.5 wt.% to 20 wt.% of organic carbonate additives e).

[0078] In principle, this can be any organic carbonate-containing compound that can be mixed into reactively curable adhesives.

[0079] The adhesive compound particularly preferably contains as additive e) at least one organic aliphatic carbonate additive.

[0080] Preferably an organic cyclic carbonate with a molar mass of less than 1000 g / mol, particularly preferably less than 500 g / mol, most preferably up to 200 g / mol.

[0081] According to particularly preferred embodiments of the invention, the reactively curable adhesive mass contains as an organic carbonate additive e) an organic cyclic carbonate e1) with a molar mass of 80 to 200 g / mol, preferably of 80 to 120 g / mol.

[0082] Preferably, the organic carbonate additive e) is an organic cyclic carbonate e1 ) with the general structure according to formula I):

[0083]

[0084] where R 1 and R 2 each are independently the same or different and each is selected from the group consisting of hydrogen and alkyl groups, and wherein R 3 and R 4each is independently the same or different and is each selected from the group consisting of hydrogen, alkyl groups, aromatic groups, alkyl halides, halogen groups and vinyl groups.

[0085] The alkyl groups in the above descriptions are preferred over the R groups. 1 , R 2 , R 3 and R 4 Alkyl groups with 1 to 10 carbon atoms, particularly preferably 1 to 4 carbon atoms. Suitable cyclic carbonates are in particular 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolane-2-one, 4-vinyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one (1,2-butylene carbonate), cis-4,5-dimethyl-1,3-dioxolan-2-one (cis-2,3-butylene carbonate), 1,3-dioxolan-2-one (ethylene carbonate), and 4-methyl-1,3-dioxolan-2-one (Propylene carbonate).

[0086] According to particularly advantageous embodiments of the invention, R 1 and R 2 and R3 and R 4 Hydrogen atoms, resulting in the organic cyclic carbonate compound ethylene carbonate with a molar mass of 88.06 g / mol.

[0087] According to further particularly advantageous embodiments of the invention, R 2 and R 3 and R 4 hydrogen atoms and R 1 a methyl group, which results in the organic cyclic carbonate compound propylene carbonate with a molar mass of 102.09 g / mol.

[0088] According to particularly preferred embodiments of the invention, the organic carbonate additive e) is an aliphatic cyclic carbonate e1) selected from the group consisting of ethylene carbonate, propylene carbonate or a mixture thereof, wherein propylene carbonate is particularly preferred.

[0089] Preferably, the adhesive mass contains 0.5 wt.% to 20 wt.%, most preferably 2 to 17 wt.%, ethylene carbonate, propylene carbonate or a mixture thereof, with propylene carbonate being particularly preferred.

[0090] According to particularly preferred embodiments of the invention, the reactively curable adhesive mass contains 4.5 wt.% to 20 wt.% propylene carbonate as an organic carbonate additive e).

[0091] Preferably, the reactively curable adhesive contains 4.5 wt.% to 8.0 wt.% propylene carbonate as an organic carbonate additive (e). This gives the adhesive optimal wet-temperature stability.

[0092] According to further preferred embodiments of the invention, a polycarbonate polyol e2) is included as the organic carbonate additive e).

[0093] Suitable and, within the scope of the present invention, preferred polycarbonate polyols can be obtained by reacting carbonic acid derivatives, e.g., diphenyl carbonate, dimethyl carbonate, or phosgene, with diols. Suitable examples of such diols are ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, bisphenol F, and lactone-modified diols. The diol component preferably contains 40 to 100 wt% hexanediol, preferably 1,6-hexanediol and / or hexanediol derivatives. More preferably, the diol component contains examples that, in addition to terminal OH groups, also have ether or ester groups.

[0094] The polycarbonate polyols should be essentially linear. However, they can optionally be slightly branched by the incorporation of polyfunctional components, especially low-molecular-weight polyols. Suitable examples include glycerol, trimethylolpropane, hexanetriol-1,2,6, butanetriol-1,2,4, trimethylolpropane, pentaerythritol, quinite, mannitol, sorbitol, methyl glycoside, and 1,3,4,6-dianhydrohexites.

[0095] Suitable polycarbonate polyols are available, for example, under the trade names Desmophen® C 2102 (Covestro), Eternacoll® PH-300D (UBE) and Kuraray Polyol C-1090 (Kuraray).

[0096] Copolymers with polyethers are particularly conceivable and preferred, resulting in polyether carbonate polyols e3).

[0097] A suitable polyether carbonate polyol is available, for example, under the trade name Cardyon® LC06 from the company Covestro.

[0098] Particularly preferably, the organic carbonate additive e) is a polycarbonate diol e2) with terminal hydroxy groups. Particularly preferably, this is a linear, aliphatic polycarbonate diol.

[0099] According to particularly preferred embodiments of the invention, the organic carbonate additive e) is a polycarbonate polyol e2), wherein the polycarbonate polyol is selected from the group consisting of linear, aliphatic polycarbonate diols. Preferably, the amount of the linear, aliphatic polycarbonate diol(s) is 0.5 wt.% to 20 wt.%, particularly preferably 2 wt.% to 17 wt.%.

[0100] The linear, aliphatic polycarbonate diol available from Covestro under the trade name Desmophen® C 2102 is particularly suitable.

[0101] According to particularly preferred embodiments of the invention, the at least one organic carbonate additive is selected from the group consisting of

[0102] e1 ) aliphatic cyclic carbonates with a molar mass of 80 to 200 g / mol, preferably of 80 to 120 g / mol,

[0103] e2) linear, aliphatic polycarbonate polyols, wherein linear, aliphatic polycarbonate diols with terminal hydroxy groups are particularly preferred, ande3) polyether carbonate polyols.

[0104] Particularly preferred is at least one organic carbonate additive selected from the group consisting of

[0105] e1) aliphatic cyclic carbonates with a molar mass of 80 to 200 g / mol, preferably of 80 to 120 g / mol, wherein propylene carbonate is particularly preferred; and e2) linear, aliphatic polycarbonate diols with terminal hydroxy groups.

[0106] Reactive curing

[0107] The adhesive compound according to the invention is a reactively curable adhesive compound.

[0108] Within the scope of the present invention, a "reactively curable adhesive" is understood to be an adhesive that cures through a chemical reaction of at least one correspondingly reactive component, thereby forming the adhesive bond. Within the scope of the present invention, such adhesives are also referred to as "reactive adhesives".

[0109] Preferably, the reactive curable adhesive tapes or the corresponding reactive adhesives according to the invention function as structural adhesives or semi-structural adhesives after curing. According to DIN EN 923: 2006-01, structural adhesives are adhesives that form adhesive bonds which can maintain a specified strength within a structure for a predetermined extended period of time (according to the ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). They are therefore adhesives for chemically and physically demanding bonding applications, which contribute to the strengthening of the adhesive tapes in the cured state.

[0110] The term “(semi-)structural adhesive” or “(semi-)structural adhesives” encompasses both “semi-structural adhesives” and “structural adhesives.” “Semi-structural adhesives” are cured adhesives that exhibit a tensile shear strength of at least 1.0 MPa and preferably at least approximately 1.5 MPa (each on steel) in a tensile shear test. “Structural adhesives” or “structural adhesives” are cured adhesives that exhibit particularly high tensile shear strength and that demonstrate a tensile shear strength of at least 5 MPa, preferably at least 7 MPa, and most preferably at least 10 MPa (each on steel) in a tensile shear test. As explained above, the chemical reaction occurs after activation, such as by heat, moisture, plasma, radiation, or by bringing two adhesive layers containing suitable reactants into contact.

[0111] Preferably, within the scope of the present invention, are reactively curable adhesive tapes in which the curing is effected by activation by means of radiation, in particular by means of light of a wavelength in the visible range of the electromagnetic spectrum or by means of UV light.

[0112] The reactive curing adhesive therefore contains at least the following components

[0113] a) at least one polymer, and

[0114] b) at least one polymerizable compound, and

[0115] c) at least one initiator.

[0116] At least one polymer a)

[0117] The product may contain one (single) polymer or several polymers. The description of "polymer" and the term "total quantity" thus encompass both the presence of a single polymer and the presence of multiple polymers. The terms "at least one," "one or more," or "exactly one" refer, in accordance with industry practice, to the chemical nature of the respective compounds and not to their quantity.

[0118] The adhesive mass preferably contains 10 wt.% to 60 wt.% of at least one polymer a), more preferably the adhesive mass comprises 25 wt.% to 60 wt.% and particularly preferably 30 wt.% to 55 wt.% of at least one polymer a), in each case based on the total weight of the adhesive mass.

[0119] The weight percentages (wt%) refer to one polymer or to the sum of all polymers if two or more polymers are present.

[0120] According to preferred embodiments of the invention, the polymer(s) is / are selected from the group consisting of ethylene-vinyl acetate copolymers (EVA), poly(meth)acrylates, polyurethanes (PU), polyvinyl acetates (PVA), polyvinyl acetals, such as in particular polyvinyl butyral (PVB), polyesters and polymers of monomers comprising N-vinyl compounds. Particularly preferred is the polymer(s) selected from the group consisting of ethylene-vinyl acetate copolymers (EVA), (meth)acrylate block copolymers, poly(meth)acrylates and polyurethanes (PU).

[0121] Particularly preferred is the polymer(s) selected from the group consisting of ethylene-vinyl acetate copolymers (EVA) and (meth)acrylate block copolymers, poly(meth)acrylates, in particular and preferably in combination with the reactive chemistry variant A) described below.

[0122] According to particularly preferred embodiments, the adhesive mass contains at least one poly(meth)acrylate.

[0123] Preferably, the adhesive mass contains 10 wt.% to 60 wt.%, particularly preferably 25 wt.% to 60 wt.%, and especially preferably 30 wt.% to 55 wt.%, of poly(meth)acrylate.

[0124] The term "poly(meth)acrylate" refers to a polymer obtainable by polymerization, for example, radical polymerization, of acrylic and / or methacrylic monomers and optionally other copolymerizable monomers. In particular, "poly(meth)acrylate" refers to a polymer whose monomer base consists of acrylic acid, methacrylic acid, acrylic esters, and / or methacrylic esters to a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, and most preferably substantially 100%, based on the mass of the monomer base.

[0125] Preferably, the mass fraction of acrylic acid ester and / or methacrylic acid ester is 50% or more, particularly preferably 70% or more, most preferably 90% or more.

[0126] The adhesive preferably contains at least one poly(meth)acrylate; it may therefore contain one or more poly(meth)acrylates. The terms "at least one," "one or more," or "exactly one" refer, in accordance with industry practice, to the chemical nature of the respective compounds and not to their quantity. This also applies to the monomer composition of the poly(meth)acrylate.

[0127] For example, the monomer composition could consist exclusively of benzyl acrylate as a monomer, which would mean that the monomer composition includes a variety of benzyl acrylate molecules.

[0128] The poly(meth)acrylate(s) can, in principle, be any poly(meth)acrylate. According to preferred embodiments of the invention, the poly(meth)acrylates contained are produced by polymerization of a monomer composition containing one or more monomers selected from the group consisting of ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, iso-amyl acrylate, n-hexyl acrylate, 2-heptyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, iso-octyl acrylate, n-nonyl acrylate, iso-nonyl acrylate, n-decyl acrylate, iso-decyl acrylate.

[0129] 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate, 2-cyanoethyl acrylate,

[0130] 2-(2-Ethoxyethoxy)ethylacrylat, 2-Phenoxyethylacrylat, iso-Stearylacrylat, Docosylacrylat, 2-[2-(2-Methoxyethoxy)-ethoxy]ethylacrylat, Isobornylacrylat, Norbornylacrylat, Benzylacrylat, 3,3,5-Trimethylcyclohexylacrylat, Cyclohexylacrylat, 1 -Acryloyloxy-3-hydroxyadamantan, 4-[(6-Acryloyloxy)hexyloxy]4‘-cyanobiphenyl, N-Succinimidylacrylat,

[0131] 1-Ethylcyclopentylacrylat, N-tert-Octylacrylamid, N-tert-Butylacrylamid, Dimethylacrylamid, Diethylacrylamid, N-iso-Propylacrylamid, N-Hydroxyethylacrylamid, Acrylamid, 2-Acrylamido- 2-methylpropansulfonsäure, N-[3-(Dimethylamino)propyl]acrylamid, Diacetonacrylamid, N-(Butoxymethyl)acrylamid, N-Phenylacrylamid, N-[2-(Dimethylamino)ethyl]acrylamid, N-[2-(Diethylamino)ethyl]acrylamid, Methylmethacrylat, Ethylmethacrylat, Cyclohexylmethacrylat, Benzylmethacrylat, Isobornylmethacrylat, Glycerolformalmethacrylat, 2-Dimethylaminoethylmethacrylat, Phenoxyethylmethacrylat, 9-Anthrylmethylmethacrylat, 2-Ethyl-2-adamantylmethacrylat, 2-(Acetoacetyloxy)ethylmethacrylat, 2-lsopropyl-2-methacryloyloxyadamantan, iso-Propylmethacrylat, iso-Butylmethacrylat,

[0132] tert-Butylmethacrylat, Furfurylmethacrylat, 2-Methacryloyloxy-2-methyladamantan,

[0133] 2-Morpholinoethylmethacrylat, Phenylmethacrylat, N-Succinimidylmethacrylat,

[0134] 2-(tert-Butylamino)ethylmethacrylat, 2-Cyclohexylpropan-2-yl-methacrylat,

[0135] 1 -Adamantylmethacrylat, 1 -Methylcyclopentylmethacrylat,

[0136] N-tert-Butylmethacrylamid, N-(Methoxymethyl)methacrylamid, N,N-Dimethylmethacrylamid, Methacrylamid, N-Phenylmethacrylamid, N,N-Dimethylmethacrylamid, N-iso-Propylmethacrylamid, N-Vinylformamid, N-Vinylpyrrolidon, N-Vinylcaprolactam, N-Vinylcarbazol, N-Vinylimidazol, Vinylmethyloxazolidinon, N-Vinyl-N-methylacetamid, Hydroxyethylacrylat, Hydroxypropylacrylat, 4-Hydroxybutylacrylat, 2-Hydroxy-3-phenoxypropylacrylate, Hydroxyethylmethacrylat, Hydroxypropylmethacrylat, 4-Hydroxybutylmethacrylat, 2-Hydroxy-3-phenoxypropylmethacrylat, 4-Hydrxyethylacrylamid, Acrylsäure, Methacrylsäure, 2-Acryloyloxyethylsuccinat, Methacryloxyethylsuccinat, Sulfoethylmethacrylat, Methacrylamid, Glycidylacrylat, Glycidylmethacrylat, 3,4-Epoxycyclohexylmethylacrylat,

[0137] 3,4-Epoxycyclohexylmethyl methacrylate, 4-Hydroxybutylacrylate glycidyl ether,

[0138] 4-Hydroxybutyl methacrylate glycidyl ether, isocyanatoethyl acrylate, isocyanatoethyl methacrylate, 2-[2-(methacryloyloxy)ethyloxy]ethyl isocyanate, 2-[2-(acryloyloxy)ethyloxy]ethyl isocyanate, and α,α-dimethyl-m-isopropenylbenzyl isocyanate. According to preferred embodiments, the poly(meth)acrylates contained are producible by polymerization of a monomer composition which contains at least 55 wt%, particularly preferably 60 to 100 wt%, most preferably 70 wt% to 100 wt%, 75 wt% to 100 wt%, 80 wt% to 100 wt%, or 90 wt% to 100 wt%, monomers with at least one aromatic residue.

[0139] The aromatic residue is preferably selected from the group consisting of phenyl groups, phenylene groups, naphthyl groups, and naphthylene groups, which may optionally bear substituents. Particularly preferred is the aromatic residue selected from the group consisting of phenyl groups, phenylene groups, naphthyl groups, and naphthylene groups, with phenyl groups or phenylene groups being especially preferred.

[0140] In accordance with expert understanding, a "phenylene group" is understood to be a phenyl group that is bonded at least twice.

[0141] This applies analogously to naphthylene.

[0142] The monomers with aromatic residues are preferably selected from the group consisting of benzyl acrylate, phenyl acrylate, 2-phenylethyl acrylate, 3-phenylpropyl acrylate, 4-phenylbutyl acrylate, 5-phenylpentyl acrylate, 6-phenylhexyl acrylate, benzylmethyl acrylate, phenyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 4-phenylbutyl methacrylate, 5-phenylpentyl methacrylate, 6-phenylhexyl methacrylate, 2-phenoxyethyl acrylate, 2-phenoxydiethylene glycol acrylate, 2-phenoxytriethylene glycol acrylate, 2-phenoxytetraethylene glycol acrylate, 2-phenoxypentaethylene glycol acrylate ; 2-phenoxyhexaethylene glycol acrylate, 2-phenoxyheptaethylene glycol acrylate ; 2-Phenoxyoctaethylene glycol acrylate, 2-phenoxynonaethylene glycol acrylate ; 2-phenoxydecaethylene glycol acrylate, 2-phenoxyethyl methacrylate.

[0143] 2-phenoxydiethylene glycol methacrylate, 2-phenoxytriethylene glycol methacrylate, 2-phenoxytetraethylene glycol methacrylate, 2-phenoxypentaethylene glycol methacrylate; 2-Phenoxyhexaethyleneglycolmethacrylat, 2-Phenoxyheptaethyleneglycolmethacrylat 2-Phenoxyoctaethyleneglycolmethacrylat, 2-Phenoxynonaethyleneglycolmethacrylat.

[0144] 2-Phenoxydecaethyleneglycolmethacrylat, 4-tert.-Butylphenylacrylat ; 4-tert.-Butylphenylmethacrylat, 2-(4-tert.-Butyl)phenoxyethylacrylat, 2-(4-tert.- Butyl)phenoxydiethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxytriethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxytetraethyleneglycolacrylat,

[0145] 2-(4-tert.-Butyl)phenoxypentaethyleneglycolacrylat,

[0146] 2-(4-tert.-Butyl)phenoxyhexaethyleneglycolacrylat,

[0147] 2-(4-tert.-Butyl)phenoxyheptaethyleneglycolacrylat,

[0148] 2-(4-tert.-Butyl)phenoxyoctaethyleneglycolacrylat,2-(4-tert.-Butyl)phenoxynonaethyleneglycolacrylat,

[0149] 2-(4-tert.-Butyl)phenoxydecaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxyethylmethacrylat, 2-(4-tert.-Butyl)phenoxydiethyleneglycolmethacrylat,

[0150] 2-(4-tert.-Butyl)phenoxytriethyleneglycolmethacrylat,

[0151] 2-(4-tert.-Butyl)phenoxytetraethyleneglycolmethacrylat,

[0152] 2-(4-tert.-Butyl)phenoxypentaethyleneglycolmethacrylat,

[0153] 2-(4-tert.-Butyl)phenoxyhexaethyleneglycolmethacrylat,

[0154] 2-(4-tert.-Butyl)phenoxyheptaethyleneglycolmethacrylat,

[0155] 2-(4-tert.-Butyl)phenoxyoctaethyleneglycolmethacrylat,

[0156] 2-(4-tert.-Butyl)phenoxynonaethyleneglycolmethacrylat,

[0157] 2-(4-tert.-Butyl)phenoxydecaethyleneglycolmethacrylat.

[0158] Particularly preferred are monomers with an aromatic residue selected from the group consisting of benzyl acrylate, phenyl acrylate, benzyl methacrylate, phenyl methacrylate, 2-phenoxyethyl acrylate, and 2-phenoxyethyl methacrylate. Most preferred are monomers with an aromatic residue selected from benzyl acrylate and benzyl methacrylate.

[0159] According to particularly preferred embodiments, the poly(meth)acrylates contained can be produced by polymerization of a monomer composition which contains exclusively aromatic (meth)acrylates as monomers, and thus 100 wt.%, wherein benzyl acrylate is exemplary and preferred.

[0160] According to preferred embodiments of the invention, at least one polymer a) is included.

[0161] The poly(meth)acrylates are produced in a manner known to those skilled in the art.

[0162] According to particularly preferred embodiments, the adhesive mass contains at least one polymer a) at least one (meth)acrylate block copolymer.

[0163] Preferably, the adhesive mass contains 10 wt.% to 60 wt.%, particularly preferably 25 wt.% to 60 wt.%, and especially preferably 30 wt.% to 55 wt.%, of (meth)acrylate block copolymers.

[0164] In principle, the (meth)acrylate block copolymers can be any (meth)acrylate block copolymers known to a person skilled in the art.

[0165] In accordance with the expert understanding, (meth)acrylate block copolymers consist of poly(meth)acrylate blocks and thus of building blocks derived from (meth)acrylate monomers, where the term (meth)acrylate, in accordance with the expert understanding, includes acrylates and methacrylates. It is preferred if the (meth)acrylate block copolymers and the corresponding poly(meth)acrylate blocks are produced predominantly or even substantially entirely from (meth)acrylate monomers and thus consist predominantly or even substantially entirely of the correspondingly derived monomer building blocks.

[0166] The term “poly(meth)acrylate” for the poly(meth)acrylate blocks is to be understood as explained above regarding poly(meth)acrylates.

[0167] The poly(meth)acrylate blocks can in principle contain smaller amounts of monomer units that are not derived from (meth)acrylates, in particular (meth)acrylic acid being used as a further component, which strictly speaking is not a “(meth)acrylate” in the narrower sense.

[0168] Preferably, the at least one (meth)acrylate block copolymer comprises at least one so-called hard block P(A) and at least one so-called soft block P(B). Each block P(A) and P(B) is preferably a homopolymer of a (meth)acrylate.

[0169] Hard blocks P(A) are preferably polymers of (meth)acrylates with a glass transition temperature of 30 °C or more, particularly preferably 60 °C or more, most preferably 70 °C or more, and again more preferably 90 °C or more. Soft blocks P(B) are preferably polymers of (meth)acrylates with a glass transition temperature of less than 20 °C, particularly preferably less than 0 °C, and again more preferably less than -20 °C.

[0170] Within the scope of the present invention, the glass transition temperature of polymers or polymer blocks in block copolymers is determined by differential scanning calorimetry (DSC) as described in DIN EN ISO 11357-1:2023-06. For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 pL) and sealed with a perforated lid. A Netzsch DSC 204 F1 is used for the measurement. The instrument is operated under nitrogen for inerting. The sample is first cooled to -150 °C, then heated to +150 °C at a rate of 10 K / min and cooled again to -150 °C. The subsequent second heating cycle is also performed at 10 K / min, and the change in heat capacity is recorded. Glass transitions are identified as steps in the thermogram.Determining the glass transition temperature from DSC measurements is straightforward for a person skilled in the art and is described in more detail, for example, in EP 2832811 A1.

[0171] The monomers of the hard block(s) P(A) are preferably selected from the group consisting of methyl methacrylate, methyl acrylate, t-butyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, isobornyl methacrylate, isobornyl methacrylate, dihydrodicyclopentadienyl acrylate, hydroxyethyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, glycidyl methacrylate, ethyl methacrylate, and benzyl methacrylate. According to particularly advantageous embodiments, at least one hard block is included which is a homopolymer of methyl methacrylate (MMA).

[0172] Monomers of the soft block(s) P(B) are preferably selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, i-octyl acrylate, 2-phenoxyethyl acrylate, propylheptyl acrylate, ethyl acrylate, lauryl acrylate, lauryl methacrylate, hydroxyethyl acrylate, methoxyethyl acrylate, heptadecyl methacrylate, heptadecyl acrylate, ethylene glycol acrylate and stearyl methacrylate.

[0173] According to particularly advantageous embodiments, at least one soft block is included which is a homopolymer of n-butyl acrylate (BA).

[0174] According to further advantageous embodiments, at least one soft block is included, which is a copolymer of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA).

[0175] According to particularly advantageous embodiments, the (meth)acrylate block copolymer is a triblock copolymer with the block sequence P(A)-P(B)-P(A), where P(A) and P(B) represent hard and soft blocks as defined above.

[0176] The two A-blocks of the (meth)acrylate block copolymers of type ABA are characterized by a common criterion: their joint manufacturability from the same A-monomers, and preferably also by a criterion relating to their glass transition temperature. Those skilled in the art understand that, due to the manufacturing process, the A-blocks exhibit a high degree of similarity, but, due to the nature of the polymerization processes used for their production, particularly when using two or more different A-monomers, they need not be exactly identical. This applies analogously to the (meth)acrylate block copolymer itself, since those skilled in the art in polymeric materials would refer to such block copolymers, which differ from each other with respect to the A- and B-blocks only within the scope of manufacturing-related variations, as a single material, i.e., a (meth)acrylate block copolymer.Accordingly, the A-blocks do not differ, or differ only slightly, with respect to their glass transition temperature. This is therefore a curable adhesive according to the invention, wherein the poly(meth)acrylates of the A-blocks can be produced by polymerizing A-monomers of the same composition, and the A-blocks are preferably substantially identical. By way of example, an additional or alternative curable adhesive according to the invention is also present, wherein the two A-blocks represent poly(meth)acrylates whose glass transition temperatures differ by less than 5 °C, preferably by less than 3 °C, and particularly preferably by less than 1 °C. In the inventors' opinion, it is generally preferred to implement the A-blocks as polymethacrylates and to use polyacrylates for the B-blocks. Therefore, a curable adhesive according to the invention is preferred, wherein the A-blocks are methacrylate polymers and the B-block is an acrylate polymer.A particularly preferred material is a curable adhesive compound, wherein the A-blocks are polymethyl methacrylates and the B-block is a poly(n-butyl acrylate), or poly(2-ethylhexyl acrylate) or a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate.

[0177] P(A) is preferably a homopolymer of MMA and P(B) is preferably a homopolymer of BA or a copolymer of BA and 2-EHA, with a homopolymer of BA being particularly preferred as a soft block.

[0178] A suitable (meth)acrylate block copolymer is available, for example, under the trade name KURARITY™ LA 3320.

[0179] The (meth)acrylate block copolymer(s) are otherwise produced in a manner known to those skilled in the art.

[0180] With regard to the mass fractions of the A and B blocks, the inventors consider it particularly advantageous not to choose the mass fraction of the A blocks to be too low. Based on the inventors' experiments, the presence of a sufficient proportion of the hard block appears to have a particularly positive influence on the advantageous bond strength at elevated temperatures, which is especially surprising since the exclusive use of PMMA did not result in any improvement in this respect. According to the inventors, a curable adhesive compound according to the invention is preferred, wherein the combined mass fraction of the A blocks is 15% or more, preferably 25% or more, particularly preferably 35% or more, and most preferably 45% or more, based on the mass of the (meth)acrylate block copolymers.

[0181] With regard to the length of the (meth)acrylate block copolymers, a curable adhesive is preferred, wherein the number-average molar masses M n the (meth)acrylate block copolymers are in the range of 20,000 to 1,000,000 g / mol, preferably in the range of 30,000 to 500,000 g / mol, particularly preferably in the range of 50,000 to 350,000 g / mol.

[0182] According to further particularly advantageous embodiments of the invention, the adhesive mass contains as polymer a) at least one ethylene-vinyl acetate copolymer (EVA).

[0183] Preferably, the adhesive mass contains 10 wt.% to 60 wt.%, particularly preferably 25 wt.% to 60 wt.%, and especially preferably 30 wt.% to 55 wt.%, of ethylene-vinyl acetate copolymers (EVA). In principle, all ethylene-vinyl acetate copolymers known to those skilled in the art are conceivable.

[0184] However, in the context of the present invention, an ethylene-vinyl acetate copolymer with a vinyl acetate content of 60 to 90% is preferably used.

[0185] Ethylene-vinyl acetate copolymers with a vinyl acetate content of less than 60% are also conceivable, but less preferred due to their higher crystallinity. This results in a particularly tacky adhesive mass.

[0186] According to further particularly advantageous embodiments of the invention, the adhesive mass contains as polymer a) at least one polyurethane, in particular and preferably in the case of variant B) described below, of reactive chemistry.

[0187] Preferably, the adhesive mass contains 10 wt.% to 60 wt.%, particularly preferably 25 wt.% to 60 wt.%, and especially preferably 50 wt.% to 60 wt.%, polyurethane.

[0188] Thermoplastic polyurethanes with a crystalline melting point of less than 100 °C and / or a softening point of less than 100 °C are preferred. In this context, the term softening point refers to the temperature at which the thermoplastic granules bond to themselves.

[0189] The crystalline melting temperature is determined by DSC as described in the methods section. Preferably, the polymer is a semicrystalline thermoplastic polymer, particularly to achieve tacky properties in the reactive curing adhesive.

[0190] In this case, in addition to its crystalline melting temperature (which is related to the melting of the crystallites), it very preferably has a glass transition temperature according to DSC of at most 25 °C, preferably at most 0 °C.

[0191] In preferred embodiments, at least one thermoplastic polyurethane is used. Commercially available thermoplastic polyurethanes include, for example, Desmocoll® 530 / 1 and Desmocoll® 540 / 3 as well as Desmomelt® 530 from Covestro AG (Leverkusen, Germany) or IROSTIC® S-6558 and IROSTIC® S 8612 from Huntsman (Huntsman Holland BV, Botlek-Rotterdam, Netherlands) or alternative variants from these product lines. Other available product lines include Elastollan® from BASF (Ludwigshafen, Germany) and Pearlbond from Lubrizol (Lubrizol Advanced Materials Europe BVBA, Brussels, Belgium).

[0192] Manufacturers also specify a minimum activation temperature for polyurethanes. Preferably, thermoplastic polyurethanes have a minimum activation temperature of less than 100 °C, and particularly less than 80 °C. Preferred examples of such thermoplastic polyurethanes are Desmomelt® 530 and IROSTIC® S-6558. Desmomelt® 530 is a hydroxy-terminated, largely linear, thermoplastic, highly crystallizing polyurethane elastomer. According to the manufacturer, IROSTIC® S-6558 is a linear thermoplastic polyurethane for solvent-based adhesives. Its characteristics, according to the manufacturer, are: a very low crystallization rate, a long open time, and a very low activation temperature.

[0193] According to preferred embodiments of the invention, the polymer of the reactively curable adhesive is essentially inert with respect to the at least one polymerizable compound b) and the initiator c) as well as any other substances. In this context, inert means that the polymerizable compounds, the initiator, and any other substances do not react substantially with the polymer before light curing under suitably chosen conditions, particularly at room temperature (23 °C).

[0194] For this reason, in a preferred embodiment, no acid, in particular no acrylic acid or other monomers with one or more carboxyl groups, and no amines, in particular no tertiary amines, are included as comonomer(s) in the monomer composition of the polymer or poly(meth)acrylate.

[0195] In a specific embodiment, the poly(meth)acrylate(s) is also inert after activation of the curing reaction. This means that the poly(meth)acrylate does not participate in the radical reaction.

[0196] Variants of reactive chemistry

[0197] As described above, reactive curing can be based on various mechanisms, whereby, within the scope of the present invention, curing is preferably carried out by radiation using UV light and / or light in the visible range.

[0198] Variant A): cationic epoxy curing

[0199] According to a first preferred embodiment of the invention, the reactively curable adhesive is an epoxy-based adhesive that can be cured by visible light and / or UV light. For this purpose, it contains at least one polymerizable epoxy compound b1) as a polymerizable compound b) and at least one cationic initiator c) as an initiator c). At least one polymerizable epoxy compound b1)

[0200] The term "polymerizable" here refers, in accordance with expert understanding, to the ability of these compounds to undergo a polymerization reaction, possibly after suitable activation. In the case of polymerizable epoxy compounds, for example, polymerizability is enabled by the epoxy groups.

[0201] In accordance with the skilled person's understanding, epoxy compounds are those compounds that contain at least one oxirane group. They can be aromatic or aliphatic, in particular cycloaliphatic, in nature. Polymerizable epoxy compounds can comprise monomeric, oligomeric, or polymeric epoxy compounds. Polymerizable epoxy compounds often have, on average, at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule. A curable adhesive according to the invention is preferred in this respect, wherein the one or more polymerizable epoxy compounds are selected from the group consisting of epoxy compounds with two or more epoxy groups, preferably two epoxy groups.

[0202] Oligomeric and polymeric epoxy compounds mostly comprise linear polymers with terminal epoxide groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol), polymers with skeletal oxirane units (e.g., polybutadiene polyepoxide), and polymers with epoxide side groups (e.g., a glycidyl methacrylate polymer or copolymer). The molecular weight of such epoxide compounds can vary from 58 to approximately 100,000 g / mol or more, with molecular weight being an important parameter for adjusting the dynamic viscosity. Examples of polymerizable epoxy compounds include epoxycyclohexanecarboxylates, such as 4-epoxy-cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. Further examples of polymerizable epoxy compounds are disclosed, for example, in US patent 3,117,099 A.Other polymerizable epoxy compounds that are particularly useful in the application of this invention include glycidyl ether monomers, such as those disclosed, for example, in US 3,018,262 A. Examples include the glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin (e.g., the diglycidyl ether of 2,2-bis-(2,3-epoxypropoxyphenol)propane). In particular, diglycidyl ethers of bisphenols, such as bisphenol-A (4,4'-(propane-2,2-diyl)diphenol) and bisphenol-F (bis(4-hydroxyphenyl)methane), are of particular use. Such reaction products are commercially available in various molecular weights and states of matter (e.g., so-called Type 1 to Type 10 BADGE resins).

[0203] Typical examples of liquid bisphenol-A diglycidyl ethers are the commercial products DER331 from Olin and Epon 828 from Westlakeepoxy, as well as the hydrogenated variant Eponex 1510 from Hexion.

[0204] Typical solid BADGE resins are the commercial products Araldite GT6071, GT7072, Epon 1001 and DER 662. Other reaction products of phenols with epichlorohydrin are the phenol and cresol novolac resins such as the Epiclon types or Araldite EPN and ECN types (e.g. ECN1273).

[0205] The inventors prefer a curable adhesive composition according to the invention, wherein one or more polymerizable epoxy compounds are selected from the group consisting of epoxy compounds with at least one cycloaliphatic group, in particular a cyclohexyl group or a dicyclopentadienyl group. Additionally or alternatively, a curable adhesive composition according to the invention is preferred, wherein one or more polymerizable epoxy compounds are selected from the group consisting of bisphenol A diglycidyl ethers and bisphenol F diglycidyl ethers, preferably bisphenol A diglycidyl ethers.

[0206] According to the inventors, particularly advantageous curable adhesives can be obtained when two or more different polymerizable epoxy compounds are used, especially when these differ in their state of matter at room temperature.A preferred curable pressure-sensitive adhesive according to the invention comprises one or more polymerizable epoxy compounds selected from the group consisting of epoxy compounds that are solids or highly viscous substances with a dynamic viscosity of 50 Pa s or more, preferably 100 Pa s or more, and particularly preferably 150 Pa s or more, at 25 °C, and / or wherein the curable adhesive comprises one or more polymerizable epoxy compounds selected from the group consisting of epoxy compounds that are liquids with a dynamic viscosity of 40 Pa s or less, preferably 20 Pa s or less, and most preferably 10 Pa s or less, at 25 °C. Within the scope of the present invention, the dynamic viscosity is determined according to DIN 53019-1 from 2008; at 25 °C, with a shear rate of 1 s. -1 certainly.

[0207] Preferably, the adhesive mass according to the invention contains, irrespective of the specific selection of the polymerizable epoxy compound(s), 10 wt.% to 60 wt.%, particularly preferably 25 wt.% to 60 wt.%, particularly preferably 30 wt.% to 55 wt.%, polymerizable epoxy compound(s) b1) as at least one polymerizable compound b).

[0208] The values ​​in wt.% are, as with all components within the scope of the present invention, based on the respective total weight of the reference system, here the adhesive compound.

[0209] At least one cationic initiator c1)

[0210] In the embodiment with the polymerizable epoxy compound(s) b1 ) the adhesive mass according to the invention contains at least one suitable cationic initiator d ).

[0211] Suitable cationic initiators are known to those skilled in the art based on their general technical knowledge and are frequently used, particularly in the field of epoxy-based reactive adhesives. The skilled person essentially tailors the initiator system used for curing to the application requirements and the polymerizable epoxy compounds employed.

[0212] With regard to subsequent handling properties, the inventors believe it is particularly advantageous to use radiation-crosslinking systems, as radiation activation provides significant handling advantages. A curable adhesive compound according to the invention is preferred, wherein one or more cationic initiators are selected from the group consisting of radiation-activated initiators, and / or wherein the curable adhesive compound is a radiation-curing adhesive compound.

[0213] Sulfonium, iodonium, and metallocene-based systems are particularly suitable as initiators for cationic radiation-based, i.e., often UV-induced, curing of epoxy compounds. For examples of sulfonium-based cations, see US 6,908,722 B1. Examples of anions that serve as counterions for the aforementioned cations include tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate, hexachloroantimonate, tetrakispentafluorophenylborate, tetrakis-(pentafluoromethylphenyl)borate, bi-(trifluoromethylsulfonyl)amides, and tris-(trifluoromethylsulfonyl)methide. Furthermore, chloride, bromide or iodide are also conceivable as anions, especially for lodonium-based initiators, although initiators that are essentially free of chlorine and bromine are preferred.A high-performance example of such a system is triphenylsulfonium hexafluoroantimonate. Other suitable initiators are disclosed, for example, in US 3,729,313 A, US 3,741,769 A, US 4,250,053 A, US 4,394,403 A, US 4,231,951 A, US 4,256,828 A, US 4,058,401 A, US 4,138,255 A and US 2010 / 063221 A1.

[0214] Preferably a cationic initiator c1) is used, which is in particular selected from the group of sulfonium salts, such as and in particular triarylsulfonium salts, and iodonium salts.

[0215] Beispielsweise und bevorzugt ist der kationische Initiator c1) ausgewählt aus der Gruppe bestehend aus T ris(4-(4-acetylphenyl)thiophenyl)sulfonium-tetrakis(pentafluorphenyl)borat, T riphenylsulfoniumhexafluoroarsenat, T riphenylsulfoniumhexafluoroborat, T riphenylsulfoniumtetrafluoroborat, T riphenylsulfoniumtetrakis-(pentafluorobenzyl)-borat, Methyldiphenylsulfoniumtetrafluoroborat, Methyldiphenylsulfoniumtetrakis- (pentafluorobenzyl)-borat, Dimethylphenylsulfoniumhexafluorophosphat, T riphenyl-sulfoniumhexafluorophosphat, T riphenylsulfoniumhexafluoroantimonat, Diphenyl-naphthylsulfoniumhexafluoroarsenat, T ritolylsulfoniumhexafluorophosphat, Anisyldiphenyl-sulfoniumhexafluoroantimonat, 4-Butoxyphenyldiphenylsulfoniumtetrafluoroborat, 4-Chlorophenyldiphenylsulfoniumhexafluoroantimonat, Tris-(4-phenoxyphenyl)-sulfonium-hexafluorophosphat, Di-(4-ethoxyphenyl)-methylsulfoniumhexafluoroarsenat, 4-Acetylphenyl-diphenylsulfoniumtetrafluoroborat,4-Acetylphenyldiphenylsulfoniumtetrakis- (pentafluorobenzyl)-borat, T ris-(4-thiomethoxyphenyl)-sulfoniumhexafluorophosphat, Di- (methoxysulfonylphenyl)-methylsulfoniumhexafluoroantimonat, Di-(methoxynaphthyl)-methylsulfoniumtetrafluoroborat, Di-(methoxynaphthyl)-methylsulfoniumetrakis-(penta-fluoro-benzyl)borat, Di-(carbomethoxyphenyl)-methylsulfoniumhexafluorophosphat, (4-Octyloxyphenyl)-diphenylsulfoniumtetrakis-(3,5-bis-trifluoromethylphenyl)-borat, Tris-(dodecyl-phenyl)-sulfoniumtetrakis-(3,5-bis-trifluoromethylphenyl)-borat, 4-Acetamidphenyl-diphe-nylsulfoniumtetrafluoroborat, 4-Acetamidphenyldiphenylsulfoniumtetrakis-(pentafluoro-benzyl)-borat, Dimethylnaphthylsulfoniumhexafluorophosphat, T rifluoromethyldiphenyl-sulfoniumtetrafluoroborat, Trifluoromethyldiphenylsulfoniumtetrakis-(pentafluorobenzyl)-borat, Phenylmethylbenzylsulfoniumhexafluorophosphat, 5-Methylthianthreniumhexa-fluorophosphat, 10-Phenyl-9,9-dimethylthioxantheniumhexafluorophosphat,10-Phenyl-9-oxo-thioxantheniumtetrafluoroborat, 10-Phenyl-9-oxothioxantheniumtetrakis-(pentafluoro-benzyl)-borat, 5-Methyl-10-oxothianthreniumtetrafluoroborat, 5-Methyl-10-oxothianthreni-umtetrakis-(pentafluorobenzyl)-borat und 5-Methyl-10,10-dioxothianthreniumhexafluorophosphat.,

[0216] Specific examples of usable iodonium salts are diphenyliodonium tetrafluoroborate, di-(4-methylphenyl)-iodonium tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate, di-(4-chlorophenyl)-iodonium hexafluorophosphate, dinaphthyliodonium tetrafluoroborate, di-(4-trifluoromethylphenyl)-iodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, di-(4-methylphenyl)-iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, di-(4-phenoxyphenyl)-iodonium tetrafluoroborate, phenyl-2-thienyliodonium hexafluorophosphate, 3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, and 2,2'-diphenyliodonium tetrafluoroborate. Di-(2,4-dichlorophenyl)-iodonium hexafluorophosphate, di-(4-bromophenyl)-iodonium hexafluorophosphate, di-(4-methoxyphenyl)-iodonium hexafluorophosphate, di-(3-carboxyphenyl)-iodonium hexafluorophosphate, di-(3-methoxycarbonylphenyl)-iodonium hexafluorophosphate, Di-(3-methoxysulfonylphenyl)-iodonium hexafluorophosphate,Di-(4-acetamidophenyl)-iodoniumhexafluorophosphat, Di-(2-benzothienyl)-iodoniumhexafluorophosphat, Diaryliodoniumtristrifluormethylsulfonylmethid wie Diphenyliodoniumhexafluoroantimonat, Diaryliodoniumtetrakis-(pentafluorophenyl)-borat wie Diphenyliodoniumtetrakis-(pentafluorophenyl)-borat, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodoniumhexafluoroantimonat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodoniumtrifluoromethylsulfonat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodoniumhexafluorophosphat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodoniumtetrakis-(pentafluorophenyl)-borat, Bis-(4-tert-butylphenyl)-iodoniumhexafluoroantimonat, Bis-(4-tert-butylphenyl)-iodoniumhexafluorophosphat, Bis-(4-tert-butylphenyl)-iodoniumtrifluoromethylsulfonat, Bis-(4-tertbutylphenyl)-iodoniumtetrafluoroborat, Bis-(dodecylphenyl)-iodoniumhexafluoroantimonat, Bis-(dodecylphenyl)-iodoniumtetrafluoroborat, Bis-(dodecylphenyl)-iodoniumhexafluoro-phosphat,Bis-(dodecylphenyl)-iodoniumtrifluoromethylsulfonat, Di-(dodecylphenyl)-iodoniumhexafluoroantimonat, Di-(dodecylphenyl)-iodoniumtriflat, Diphenyliodoniumbisulfat, 4,4'-Dichlorodiphenyliodoniumbisulfat, 4,4'-Dibromodiphenyliodoniumbisulfat, 3,3'-Dinitro-diphenyliodoniumbisulfat, 4,4'-Dimethyldiphenyliodoniumbisulfat, 4,4'-Bis-succinimido-diphenyliodoniumbisulfat, 3-Nitrodiphenyliodoniumbisulfat, 4,4'-Dimethoxydiphenyl-iodoniumbisulfat, Bis-(dodecylphenyl)-iodoniumtetrakis-(pentafluorophenyl)-borat, (4- Octyloxyphenyl)-phenyliodoniumtetrakis-(3,5-bis-trifluoromethylphenyl)-borat und (Tolyl-cumyl)-iodoniumtetrakis-(pentafluorophenyl)-borat, und Ferrocenium-Salze (siehe zum Beispiel EP 0 542 716 B1) wie r|5-(2,4-cyclopentadien-1-yl)-[(1,2,3,4,5,6,9)-(1-methylethyl)-benzol]-eisen.,

[0217] Photoinitiators are typically used individually or in combination with two or more photoinitiators. When using photoinitiators, combinations with other additives are also possible to adapt the activation wavelength of the photoinitiation system to the selected emission spectrum.

[0218] A particularly suitable and preferred cationic initiator c1) is a triarylsulfonium salt. Photoinitiators with the counterion (anion) tetrakis(pentafluorophenyl)borate are particularly preferred. For example, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate and 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borates (CAS No. 178233-72-2) are preferred.

[0219] The connection is particularly preferred

[0220] Tris(4-(4-acetylphenyl)thiophenyl)sulfonium-tetrakis(pentafluorophenyl)borate as cationic initiator c1).

[0221] A curable adhesive mass according to the invention, containing 0.1 to 7 wt.%, preferably 0.3 to 5 wt.%, particularly preferably 0.5 to 4 wt.%, of cationic initiators c1), is preferred largely independent of the selection of the specific cationic initiator.

[0222] In a preferred embodiment, the reactively curable adhesive according to the invention is characterized in that the light-activated initiator system, consisting of cationic initiator c1) in combination with the polymerizable epoxy compound b1), has an open time of at least 1 minute, preferably at least 2 minutes, and particularly preferably at least 5 minutes. After activation and curing, the now cured adhesive tape is no longer considered to be a "tacky" adhesive tape.

[0223] Variant B): radical hardening

[0224] According to a further preferred embodiment of the invention, the reactively curable adhesive is a radically curable adhesive using visible light and / or UV light.

[0225] For this purpose, it contains as polymerizable compound b) at least one radically polymerizable compound b2) and as initiator c) at least one radical initiator c2) and additionally a photoredox catalyst f).

[0226] at least one polymerizable compound b2)

[0227] In accordance with expert understanding, the radically polymerizable compound should stand for a compound that is capable of radical chain polymerization.

[0228] The radically polymerizable compound b2) is preferably selected from radically polymerizable monomers and radically polymerizable oligomers. Preferably, the radically polymerizable monomer or oligomer is selected from the group consisting of acrylic acid esters, methacrylic acid esters, vinyl compounds, compounds with olefinic carbon-carbon double bonds, crosslinking radically polymerizable compounds, higher functional acrylates and higher functional methacrylates.

[0229] Crosslinking radically polymerizable compounds are in particular selected from the group consisting of diacrylates, dimethacrylates, triacrylates and trimethacrylates.

[0230] Here, "higher functional" acrylates or methacrylates are understood to be (meth)acrylates with four or more (meth)acrylate functional groups.

[0231] Particularly preferably, the radically polymerizable compound b2) has at least one acrylate or methacrylate functional group. This applies to radically polymerizable monomers, oligomers, and polymers.

[0232] Thus, the radically polymerizable compound b2) is preferably a radically polymerizable (meth)acrylate compound.

[0233] Oligomeric substances with acrylate or methacrylate functionalities are known to those skilled in the art and are also referred to as reactive resins. Here, too, the functionalization can be present in a single or multiple form within the molecule. According to advantageous embodiments, these are used in a mixture with at least one reactive monomer.

[0234] Preferred monomers for high bond strength are acrylic and / or methacrylic esters in which the alcohol portion of the ester contains aromatic structural elements, heteroatoms, or functional groups. Urethane groups, urea groups, oxygen or nitrogen heterocycles, ether groups, ester groups, acid functional groups, and / or hydroxyl functional groups are preferred. For good wet-heat resistance, acrylic and / or methacrylic esters in which the alcohol portion of the ester is a fatty alcohol are also preferred. Furthermore, for high crosslinking density, crosslinking monomers, and thus especially monomers with two or more (meth)acrylate functional groups, are preferred.

[0235] Examples of preferred monomers are 2-phenoxyethyl acrylate (CAS No.: 48145-04-6), 2-phenoxyethyl methacrylate (CAS No.: 10595-06-9), 2-hydroxy-3-phenoxy-propyl acrylate (CAS No.: 16969-10-1), 2-hydroxy-3-phenoxy-propyl methacrylate (CAS No.: 16926-87-7), 2-[2-(methacryloyloxy)ethoxycarbonyl]benzoic acid (CAS No.: 27697-00-3), 2-[[(phenylamino)-carbonyl]oxy]ethyl methacrylate (CAS No.: 51727-47-0), 2-Tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenylprop-2-enoate (CAS No.: 61167-58-6), (5-Ethyl-1,3-dioxan-5-yl)methyl acrylate (CAS No. 66492-51-1), (2-Oxo-1 ,3-dioxolan-4-yl)methyl methacrylate (CAS No.: 13818-44-5), di(ethylene glycol)-2-ethylhexyl ether acrylate (CAS No.: 117646-83-0), (2,2-dimethyl-1,3-dioxolan-4-yl)methylprop-2-enoate (CAS No.: 13188-82-4), 2-succinic acid mono-[2-(acryloyloxy)-ethyl ester] (CAS no.: 50940-49-3), 2-succinic acid mono-[2-(meth-acryloyloxy)ethyl ester] (CAS no.: 20882-04-6), (2,2-pentamethylene-1,3-oxazolidyl-3)ethyl methacrylate (CAS no.: 4203-89-8, 2-Hydroxy-3-(prop-2-enoyloxy)propyl-2-methyl-2-propyl-hexanoate (CAS No.: 444649-70-1), 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate (CAS No.: 63225-53-6), Stearyl acrylate (CAS No.: 4813-57-4), Stearyl methacrylate (CAS No.: 32360-05-7), and the crosslinking reactive monomers diurethane dimethacrylate (isomer mixture) (CAS No.: 72869-86-4), bisphenol A diglycidyl methacrylate (BIS-GMA, CAS No.: 1565-94-2), bisphenol A dimethacrylate (BIS-DMA, CAS No.: 3253-39-2), ethylene glycol diacrylate (CAS No.: 2274-11-5), ethylene glycol dimethacrylate (CAS No.: 97-90-5), trimethyloylpropane propoxylate triacrylate (CAS No.: 53879-54-2), trimethyloylpropane triacrylate (CAS No.: 15625-89-5) and / or di(trimethylolpropane)tetraacrylate (CAS No.: 94108-97-1).

[0236] Particularly preferred are 2-Hydroxy-3-phenoxy-propyl acrylate (CAS No.: 16969-10-1), 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate and diurethane dimethacrylate.

[0237] In advantageous embodiments, a reactively curable adhesive mass is preferred which contains as radically polymerizable compound b2) a radically polymerizable monomer selected from the group consisting of 2-methacryloxyethylphenylurethane, 2-phenoxyethyl acrylate,

[0238] 2-phenoxyethyl methacrylate, 2-hydroxy-3-phenoxy-propyl acrylate,

[0239] 2-Hydroxy-3-phenoxypropyl methacrylate,

[0240] 2-[2-(Methacryloyloxy)ethoxycarbonyl]benzoic acid,

[0241] 2-[[(Phenylamino)carbonyl]oxy]ethyl methacrylate,

[0242] 2-Tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenylprop-2-enoate, (5-ethyl-1,3-dioxan-5-yl)methyl acrylate, (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate, di(ethylene glycol)-2-ethylhexyl ether acrylate, (2,2-Dimethyl-1,3-dioxolan-4-yl)methylprop-2-enoate, 2-succinic acid mono-[2-(acryloyloxy)-ethyl ester],

[0243] 2-Succinic acid mono-[2-(methacryloyloxy)ethyl ester], (2,2-pentamethylene-1,3-oxazolidyl-3)ethyl methacrylate, 2-hydroxy-3-(prop-2-enoyloxy)propyl-2-methyl-2-propylhexanoate, 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate, stearyl acrylate, stearyl methacrylate, and the crosslinking reactive monomers diurethane dimethacrylate, bisphenol A diglycidyl methacrylate (BIS-GMA), bisphenol A dimethacrylate (BIS-DMA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethyloylpropane propoxylate triacrylate,

[0244] Trimethyloylpropane triacrylate and di(trimethylolpropane)tetraacrylate, wherein 2-methacryloxyethylphenylurethane,

[0245] 2-Hydroxy-3-phenoxypropyl acrylate,

[0246] 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate and / or diurethane dimethacrylate are particularly preferred.

[0247] According to particularly advantageous embodiments of the invention, 2-hydroxy-3-phenoxy-propyl acrylate (HPPA) is included as b2) a radically polymerizable compound.

[0248] According to particularly advantageous embodiments of the invention, the monomer 2-methacryloxyethylphenylurethane (MAPII) is included as b2) a radically polymerizable compound.

[0249] This results in particularly high storage stability.

[0250] MAPII appears to work particularly well in small die-cut pieces. While not bound by theory, it is speculated that these monomers have a positive effect on the inhibition caused by atmospheric oxygen.

[0251] Radically polymerizable oligomers, in particular in contrast to polymers, are understood by those skilled in the art to be compounds that are radically polymerizable with a weight average of the molecular weight distribution M. waccording to GPC of less than 35000 g / mol, in particular less than 15000 g / mol, in particular less than 10000 g / mol.

[0252] Within the scope of the present invention, for example and in particular so-called urethane acrylates are preferred as oligomers.

[0253] These include aliphatic and aromatic polyester urethane (meth)acrylates, polyether urethane (meth)acrylates, polybutadiene urethane (meth)acrylates and silicone urethane (meth)acrylates; available, for example, from Miwon, Bomar and Allnex, such as the aliphatic polyester urethane MIRAMER SC2565 with a Mw of 5200 g / mol from Miwon, or the aliphatic urethane acrylates known under the trade names EBECRYL® 8402, EBECRYL® 4858 or EBECRYL® 8809 from Allnex, or the hydrophobic urethane acrylate BRC 843 from Bomar.

[0254] Other preferred examples of radically polymerizable oligomers are aliphatic and aromatic polyester (meth)acrylates, such as the polyester acrylate EBECRYL® 5850 from Allnex, polyether (meth)acrylates, epoxy (meth)acrylates, amino (meth)acrylates, dendritic (meth)acrylates and polycarbonate (meth)acrylates.

[0255] Suitable candidates include acrylated oligoesters, for example, those based on caprolactones, such as the commercially available hydroxyethylcaprolactone acrylate (HECLA; CAS No.: 110489-05-9). The functionality of polymerizable oligomers is preferred, i.e., the number of radically polymerizable groups per molecule is 1 to 20, usually 2 to 15, and mainly 2 to 6. The dynamic viscosity, determined according to DIN 53019-1 from 2008, at 25°C is preferably greater than 1 Pa, but particularly preferably significantly greater than 10 Pa. Oligomers with dynamic viscosities at 25°C of greater than 20 Pa, preferably greater than 30 Pa, are particularly suitable as components for the production of good pressure-sensitive adhesives with sufficient cohesion. Within the scope of the present invention, the dynamic viscosity is determined according to DIN 53019-1 from 2008. at 25 °C, with a shear rate of 1 s -1 certainly.

[0256] According to advantageous embodiments, the radically polymerizable compound b2) is a radically polymerizable (meth-)acrylate-containing oligomer, which is selected from the group consisting of aliphatic urethane diacrylates, polyether urethane diacrylates, polybutadiene urethane diacrylates, polyester urethane diacrylates, epoxy acrylates, amino acrylates, and acrylated oligoesters.

[0257] Preferably, in the reactive adhesive mass according to variant B), the weight ratio of the totality of the polymers a) to the totality of the radically polymerizable compounds b2) is 3:1 to 1 :3, more preferably 2:1 to 1 :2, in particular 2:1 to 1 :1.

[0258] At least one radical initiator c2)

[0259] The adhesive mass contains at least one radical initiator c2) in the case that the polymerizable compound b) is a radically polymerizable compound b2).

[0260] A mixture of two or more initiators is also conceivable.

[0261] In addition, the adhesive mass contains at least one photoredox catalyst (f). These components constitute, in particular, an initiator system that triggers or activates the reaction for curing the reactively curable adhesive mass. Depending on the type of activation, different initiators and redox catalysts are suitable.

[0262] Within the scope of the present invention, the term "radical initiator" or radical-forming substance (or hardener) refers to a compound that can initiate a radical polymerization reaction or crosslinking of the adhesive. However, the radical initiator participates in the reaction only to a very small extent and consequently does not constitute a polymer component that determines the properties of the adhesive.

[0263] All known radical initiators can be used. Preferred radical initiators are peroxides, hydroperoxides, and azo compounds. According to particularly preferred embodiments of the invention, the radical initiator is an organic peroxide. Hydroperoxides are particularly preferred, especially diisopropylbenzene hydroperoxide (CAS No. 26762-93-6). Diisopropylbenzene hydroperoxide is preferably used in the form of a 50 wt% solution of diisopropyl hydroperoxide in diisopropylbenzene, available under the trade name Peroxan® IHP-50. α,α-Dimethylbenzyl hydroperoxide, also known as cumene hydroperoxide (CAS No. 80-15-9), can also be used. Furthermore, for example, p-menthane hydroperoxide (CAS No. 26762-92-5), tert-amyl hydroperoxide (CAS No. 3425-61-4) or 1,1,3,3-tetramethylbutyl hydroperoxide (CAS No. 5809-08-5) can also be used.

[0264] The adhesive preferably contains 0.1 wt.% to 9 wt.%, particularly preferably 0.1 wt.% to 5 wt.%, and particularly preferably 0.1 wt.% to 2 wt.%, of radical initiators c2), preferably selected from hydroperoxides.

[0265] At least one photoredox catalyst f)

[0266] Within the scope of the present invention, the term “redox catalyst” refers to a compound that can mediate the transfer of electrons between chemical compounds that would otherwise react more slowly or not at all.

[0267] Within the scope of the present invention, the term "photoredox catalyst" refers to a light- or UV-light-sensitive compound which, when excited by light or UV light, can mediate the transfer of electrons between chemical compounds that would otherwise react more slowly or not at all. In contrast to a photoinitiator, disclosed, for example, in EP 3910715 A1, a photoredox catalyst does not decompose into reactive fission products upon irradiation with light or UV light, but is merely brought to an excited state, which is generally relatively long-lasting and from which redox processes can be initiated or mediated. Preferably, the photoredox catalyst does not trigger polymerization in the mixture with the radically polymerizable monomers or oligomers at temperatures up to 90 °C, even when the mixture is irradiated with UV or blue light.This applies as long as no radical initiator or other initiating substance is added to the mixture.

[0268] The photoredox catalyst is therefore neither an initiator nor a radical initiator. Upon irradiation with UV or blue light, it merely activates the initiator, which then triggers the polymerization. This delayed mechanism results in a so-called open time, during which the adhesive tape can still be applied before the reactive curing begins. Within the scope of the present invention, the terms "redox catalyst" and "photoredox catalyst" are not limited to the fact that the respective compound is not consumed during the reaction.

[0269] In a preferred embodiment, the reactively curable adhesive according to the invention is characterized in that the light-activated initiator system consisting of radical initiator c2) and photoredox catalyst f) in combination with the radically polymerizable compound b2) has an open time of at least 1 minute, preferably at least 2 minutes, and particularly preferably at least 5 minutes. After activation and curing, the now cured adhesive tape is no longer considered to be a "tacky" adhesive tape.

[0270] Photoredox catalysts known to those skilled in the art can be used. Photoredox catalysts are often transition metal complexes, which exist either as neutral or cationic compounds depending on the ligands, with ruthenium, copper, or iridium as the central atom. Bidentate ligands are preferably used as ligands of the transition metal complex, particularly those with at least two interconnected heteroaromatic six-membered rings, such as biphenyls, which in turn can be part of a more complex structure—such as polycyclic aromatic hydrocarbons and / or bridged bicyclic or polycyclic aromatic hydrocarbons. If ligands containing biphenyl structural units are used, one of the aromatic rings of the biphenyl can advantageously form a "tooth" of the ligand, thus ensuring bidentate structure.Bicyclic aromatic compounds – such as biphenyl compounds – or polycyclic aromatic compounds can be unsubstituted – meaning they have a hydrogen atom attached to each carbon atom – or singly or multiply substituted. The transition metal complex acts as a photoredox catalyst in accordance with the present invention.

[0271] According to preferred embodiments of the invention, the photoredox catalyst is a transition metal complex with ruthenium as the central atom and bipyridine or a singly or multiply substituted bipyridine derivative as ligands.

[0272] In a further preferred embodiment of the invention, the photoredox catalyst is a transition metal complex with iridium as the central atom and phenylpyridine or a singly or multiply substituted phenylpyridine derivative as ligands. Also preferred is a reactively curable adhesive according to the invention as described above, which is characterized in that the photoredox catalyst has ruthenium as the central atom and bipyridine or a singly or multiply substituted bipyridine derivative as ligands, or

[0273] Iridium as the central atom and phenylpyridine or a simply or multiply substituted phenylpyridine derivative as ligands.

[0274] Preferably, at least one photoredox catalyst is selected from the group consisting of Ru(bpm) 2+ (e.g. Tris(2,2'-bipyrimidine)ruthenium(II) dichloride), Ru(bpz)3 2+(e.g. Tris(2,2'-bipyrazine)ruthenium bis(hexafluorophosphate)), Ru(bpy)3 2+ , Ru(phen)3 2+ (e.g. Dichloro tris(1,10-phenanthroline)ruthenium(II) chloride), lr[dF(CF3)ppy]2(dtbbpy) + (e.g.

[0275] [4,4'-B / s(1 , 1 -dimethylethyl)-2,2'-bipyridine-A / 1 , A / 1 '] bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridin-yl- / V]phenyl-C]lridium(ll I) hexafluorophosphate), lr(ppy)2(dtbbpy) + (e.g. [lr(dtbbpy)(ppy)2][PF6]), each plus one or more anions (or counterion(s) of the cation), such as chloride or hexafluorophosphate, lr(Fppy)3 or / ac-lr(ppy)3(fac-Tris(2-phenylpyridine)iridium(1ll)), lr(ppy)3, and the copper complex dichloro-(1 ,10-phenanthroline)-copper(1ll) (CAS: 14783-09-6).

[0276] According to particularly preferred embodiments of the invention, the photoredox catalyst is Tris(2,2'-bipyridyl) ruthenium(II) chloride hexahydrate, Ru(bpy)3Cl2» 6H2O.

[0277] Preferably, the adhesive mass contains up to 1 wt.%, particularly preferably from 0.01 wt.% to 0.5 wt.%, and particularly preferably from 0.01 wt.% to 0.1 wt.%, of photoredox catalysts f), preferably with ruthenium as the central atom and bipyridine or a simply or multiply substituted bipyridine derivative as ligands, or iridium as the central atom and phenylpyridine or a simply or multiply substituted phenylpyridine derivative as ligands.

[0278] Other additives and / or excipients

[0279] The reactively curable adhesive may, regardless of the curing mechanism, and particularly in variants A) and B), optionally contain further additives and / or auxiliary materials known in the prior art. The proportion of these further additives and / or auxiliary materials may range from 0 wt.% to approximately 20 wt.%, preferably 0 wt.% to approximately 15 wt.%, more preferably 0 wt.% to approximately 10 wt.%, and most preferably 0 wt.% to approximately 5 wt.%.

[0280] Other additives and / or auxiliary substances include, for example, fillers, dyes, nucleating agents, rheological additives (for example, pyrogenic silica), blowing agents, adhesive-enhancing additives (adhesion promoters, especially silanes and tackifier resins), compounding agents, plasticizers and / or aging, light and UV protection agents, for example in the form of primary and secondary antioxidants.

[0281] In particular, and according to preferred embodiments, the proportion of fillers, such as glass beads or SiLibeads® 5211, is up to 50 wt.%, in particular up to 40 wt.%.

[0282] According to preferred embodiments, the reactive adhesive contains at least one rheology-modifying filler, such as in particular pyrogenic silica, preferably in an amount of 1 to 10 wt.%, particularly preferably 2 to 5 wt.%.

[0283] According to the inventors, particularly advantageous processing properties can be achieved through the use of so-called open-time additives. Such open-time additives, also known as retarders, serve to delay the viscosity increase of the curing adhesive without preventing complete curing and are known, for example, from EP 0661324 A1. A preferred, curable adhesive according to the invention comprises:

[0284] g) one or more open time additives, wherein the adhesive composition preferably contains 0.1 to 6.0 wt.%, particularly preferably 0.1 to 3.0 wt.%, most preferably 0.3 to 2.0 wt.%, open time additives.

[0285] The amount of open time additives should not be chosen too high, depending on the application of the curable adhesive or curable tape, so that the reaction kinetics are not slowed down too much and the curing process does not take too long if this is not desired for the respective application.

[0286] The inventors have identified particularly suitable open-time additives with which especially advantageous curing properties can be achieved in the curable adhesives according to the invention. A preferred curable adhesive according to the invention is one in which the open-time additives are selected from the group consisting of polyethylene glycol, polycaprolactone, and crown ethers.

[0287] In particular, polyethylene glycol (PEG) with different molecular weights is also used in the prior art to influence the polarity and processability of the adhesive. Since these substances have an open-time effect, the amount should not be too high, as described.

[0288] In the case of polyethylene glycol (PEG) as an open-time additive, the amount should therefore, according to preferred embodiments, be 0.1 to a maximum of 2 wt.%, preferably 0.1 to 1.3 wt.%, based on the total weight of the curable adhesive mass. Bonded composite, method for electrical release, and various adhesive tape structures.

[0289] Another object of the present invention is a bonded composite comprising at least the following layers:

[0290] • A first substrate A; and

[0291] • A second substrate B; and

[0292] • An adhesive tape obtained by curing the reactively curable adhesive tape according to the invention, and which is arranged between the substrate A and the substrate B and bonds the substrates A and B together, wherein in particular either the substrate A and the substrate B or at least one of the substrates and the adhesive tape are electrically conductive at at least one location or neither of the substrates and the adhesive tape are electrically conductive at two different locations.

[0293] A further object of the present invention is a method for electrically separating the composite according to the invention, comprising at least the following method steps: i.) Applying a voltage to two different electrically conductive points of the composite, wherein the voltage is preferably 1 to 50 V.

[0294] The voltage is applied according to step i.) of the inventive method for electrically separating the bond.

[0295] The voltage in question is, in particular, a direct current (DC) voltage.

[0296] The voltage is preferably between 2 and 50 V.

[0297] According to advantageous embodiments, the voltage is 2 to 12 V, for example 9 V. Such a voltage can be applied in particular by using a battery located in the immediate vicinity of the adhesive bond, as is particularly and for example the case in a mobile phone, tablet, etc., or by adding a battery from the outside.

[0298] According to further preferred embodiments of the invention, the voltage is from 12 to 50 V, for example 30 V. This comparatively high voltage allows for particularly quick release; the voltage only needs to be applied for a few seconds.

[0299] It is generally known to those skilled in the art how to apply a voltage without causing unwanted short circuits. The duration of applying the voltage in step i.) can, depending particularly on the selected voltage, range from a few seconds, in particular 2 seconds, up to 900 seconds, preferably up to 600 seconds, and most preferably up to 300 seconds.

[0300] Of course, it is also conceivable that the voltage is applied for a longer period than 900 seconds, especially if the voltage is comparatively low.

[0301] The inventive method for electrically separating the inventive composite allows, for example, the substrates A and B to be separated from each other quickly and easily without requiring excessive force.

[0302] Furthermore, at least one substrate leaves no or virtually no residue of the adhesive tape.

[0303] In some cases, particularly after prolonged separation processes, a thin residual film of the electrolytes used, especially ionic liquids, may remain on the separated substrate. However, this can be easily removed, for example by rinsing with a suitable solvent.

[0304] If the layers do not separate from each other after the application of voltage without further intervention, the inventive method comprises at least the following further process step:

[0305] ii.) Force applied to the adhesive tape and / or substrate A and / or substrate B, such that the distance between substrates A and B is increased.

[0306] The force that may still be required according to step ii.) is significantly less than before the application of the tension according to step i.)

[0307] The voltage is applied according to step i.) at two different electrically conductive points of the bonded composite according to the invention. The points at which the voltage is expediently applied depend on the structure of the adhesive tape and the bonded composite, and thus on the properties of the individual layers and the substrates A and B bonded together.

[0308] Some preferred embodiments are described below.

[0309] According to preferred embodiments, the reactively curable adhesive tape according to the invention is a transfer adhesive tape and consists of the adhesive layer D.

[0310] Such an adhesive tape, when bonded to two substrates A and B, can advantageously be electrically separated by ensuring that both substrates A and B are electrically conductive. This is achieved by applying a voltage to substrates A and B. The application of this voltage significantly reduces the adhesion of the adhesive layer D to substrate A and / or substrate B, causing these layers to separate.

[0311] According to preferred embodiments of the present invention, the bonded composite thus comprises the following layers:

[0312] • A first substrate A, which is electrically conductive; and

[0313] • A second substrate B, which is electrically conductive; and

[0314] • An adhesive tape according to the invention, which consists of the adhesive layer D and is arranged between the substrate A and the substrate B and bonds the substrates A and B together.

[0315] According to preferred embodiments of the invention, the reactively curable adhesive tape additionally comprises at least one carrier layer T.

[0316] According to preferred embodiments of the invention, the carrier layer T is embedded in the adhesive layer D and serves to mechanically stabilize the adhesive tape. The carrier layer T preferably has permeable carrier structures that allow the electrolyte to migrate in the z-direction, so that the electrical removability is not impaired.

[0317] Such permeable support structures can be electrically conductive or electrically non-conductive and are in particular woven fabrics, knitted fabrics made of textile fibers or metal wires, whereby textile fibers can also be coated with metal. Suitable options include, for example, b) electrically conductive textiles comprising at least one metal, preferably selected from the group consisting of copper and nickel, and / or d) at least one metal grid.

[0318] Electrical detachment then occurs analogously in the case of electrically non-conductive carriers permeable to electrolytes in the z-direction by applying the voltage to the electrically conductive substrates A and B.

[0319] Alternatively, if sufficient electrical conductivity is present, a voltage can also be applied to the carrier layer T, with the other pole then being applied to an electrically conductive substrate.

[0320] According to preferred embodiments of the present invention, the bonded composite thus comprises the following layers: • A first substrate A, which is electrically conductive; and

[0321] • A second substrate B, which is electrically conductive; and

[0322] • An adhesive tape according to the invention, comprising an adhesive layer D and a carrier layer T embedded therein which is permeable to electrolytes in the z-direction, wherein the adhesive tape is arranged between the substrate A and the substrate B and bonds the substrates A and B together.

[0323] According to further preferred embodiments, the reactively curable adhesive tape according to the invention comprises, in addition to the first adhesive layer D, at least a second adhesive layer C.

[0324] According to particularly preferred embodiments of the invention, the second adhesive layer C is electrically conductive. Such a structure has the advantage that the voltage can be applied to the adhesive layer C, so that even a non-conductive substrate, here substrate B, can be electrically released.

[0325] According to preferred embodiments of the invention, the adhesive layer C projects laterally beyond the substrate to which it is bonded, so that a tension can be applied to layer C from above, i.e. next to the substrate.

[0326] According to preferred embodiments of the invention, the substrate bonded to layer C, here substrate B, has a hole, so that here too the adhesive layer C projects laterally beyond the substrate to which it is bonded. Here too, a voltage can be applied to layer C from above, i.e., next to the substrate.

[0327] The aforementioned options are particularly advantageous when layer C is so thin that lateral contact with the layer is not practical. Alternatively, a correspondingly thin electrode can be used.

[0328] According to particularly preferred embodiments of the invention, the second adhesive layer C is also a reactively curable adhesive layer. This allows the adhesive tape to continue to be used on substrates or in applications where a reactively curable, and especially a structurally curable at room temperature, adhesive tape with high bond strength is desired. Furthermore, the first and second adhesive layers D and C are thus particularly compatible.

[0329] Preferably, the adhesive tape according to the embodiments described above consists of layers D and C. The structure comprising the second adhesive layer is hereinafter also referred to as a two-layer composite DC. According to preferred embodiments, layer D has the same dimensions in the xy-plane as layer C, so that D and C can be processed together as a two-layer composite and, for example, die-cut.

[0330] According to preferred embodiments of the present invention, the bonded composite thus comprises the following layers:

[0331] • A first substrate A, which is electrically conductive; and

[0332] • A second substrate B; and

[0333] • An adhesive tape according to the invention, which consists of the two-layer composite DC and bonds the substrates A and B together in such a way that the adhesive layer D is bonded to the conductive substrate A.

[0334] The substrate B need not be electrically conductive, as described above. According to preferred embodiments, the substrate B is not electrically conductive.

[0335] According to further preferred embodiments, the adhesive tape comprises, in addition to the first adhesive layer D, at least the following layers:

[0336] • A second adhesive layer C; and

[0337] • at least one electrically conductive support layer T, which is arranged between layers D and C.

[0338] Such an adhesive tape can be adapted to a wide variety of substrates via the second adhesive layer C, acting as a double-sided tape. These substrates can, in principle, be the same as those described in the previous embodiments where the tape is a transfer adhesive tape.

[0339] However, such an adhesive tape can also be used, in particular and advantageously, to later separate substrates A and B from each other, of which only one is electrically conductive, for example substrate A.

[0340] According to preferred embodiments, either xi.) only the carrier layer T or xii.) the carrier layer T and the second adhesive layer C are electrically conductive. This allows a voltage to be applied to xi.) the electrically conductive carrier layer or xii.) the second adhesive layer C as well as to the conductive substrate A.

[0341] The adhesive tape is advantageously pre-bonded as a double-sided tape such that the electrically releasable adhesive layer D is bonded to the conductive substrate A and the second adhesive layer to the substrate B, which may, but need not, be conductive. According to preferred embodiments of the invention, only the carrier layer is electrically conductive. A voltage can be applied to this layer particularly well, especially and preferably if the carrier layer extends laterally beyond at least one of the adhesive layers.

[0342] According to further preferred embodiments of the invention, the carrier layer T and the second adhesive layer C are electrically conductive. Such a structure has the advantage that the voltage can be applied to the adhesive layer C. A lateral overhang of the carrier layer is not necessary. The adhesive tape can therefore be manufactured in a simple manner, particularly since layers D, T, and C can be die-cut together.

[0343] Preferably, the adhesive tape according to the embodiments described above consists of the three layers D, T and C. The term three-layer composite DTC is also used for this purpose within the scope of the present application.

[0344] In a particularly advantageous embodiment of the invention, the adhesive tape according to the embodiments described above consists of the three layers D, T and C, wherein layer D is a layer of the reactively curable adhesive mass according to the invention in all embodiments, and T is an electrically conductive carrier layer, preferably T is a metal-coated PET film, and C is a layer of a reactively curable adhesive mass having the same composition as the reactively curable adhesive mass according to the invention except that it does not contain an electrolyte d) and an organic carbonate additive e).

[0345] According to preferred embodiments of the present invention, the bonded composite thus comprises the following layers:

[0346] • A first substrate A, which is electrically conductive; and

[0347] • A second substrate B; and

[0348] • An adhesive tape according to the invention, which consists of the three-layer composite DTC of all embodiments and bonds the substrates A and B together in such a way that the adhesive layer D is bonded to the conductive substrate A.

[0349] According to further preferred embodiments, the adhesive tape comprises, in addition to the first adhesive layer D, at least the following layers:

[0350] A second adhesive layer C; and at least one first electrically conductive carrier layer T, arranged between layers D and C; and

[0351] • at least one second electrically conductive carrier layer T', which is arranged on the surface of the adhesive layer D opposite the first electrically conductive carrier layer T; and

[0352] • A third adhesive layer C' is arranged on the surface of the second electrically conductive carrier layer T' opposite the first adhesive layer D. Such an adhesive tape has at least the layer structure CTDT'-C' and can be adapted to a variety of different substrates as a double-sided adhesive tape via the adhesive layers C and C'.

[0353] In principle, these can be the same substrates as in the previous embodiments, in which the adhesive tape is a transfer adhesive tape or has the three-layer structure DTC.

[0354] Such an adhesive tape can, in particular and advantageously, also be used to later separate substrates A and B from each other, neither of which is electrically conductive.

[0355] According to preferred embodiments, either xi.) only the carrier layers T and T' or xii.) the carrier layers T and T' and the second adhesive layer C and / or the third adhesive layer C' are electrically conductive.

[0356] This allows a voltage to be applied to xi.) the two electrically conductive carrier layers or xii.) to at least one of the adhesive layers C and C' and to one of the carrier layers or the other adhesive layer.

[0357] Applying the voltage greatly reduces the adhesion of the adhesive layer D to the electrically conductive carrier layers T and / or T' and causes these layers to separate from each other.

[0358] According to preferred embodiments of the invention, only the carrier layers T and T' are electrically conductive. A voltage can be applied to these layers particularly well, especially and preferably if the carrier layers T and T' extend laterally beyond at least one of the adjacent adhesive layers.

[0359] According to further preferred embodiments of the invention, the carrier layers T and T' and the second and third adhesive layers C and C', respectively, are electrically conductive. Such a structure has the advantage that the voltage can be applied to the adhesive layers C and C'. A lateral overhang of the carrier layers T and T' is not necessary. The adhesive tape can therefore be manufactured in a simple manner, particularly since the layers C, T, D, T' and C' can be die-cut together.

[0360] Preferably, the adhesive tape according to the embodiments described above consists of the five layers C, T, D, T' and C'. The term "five-layer composite CTDTC" is also used for this in the present application.

[0361] According to preferred embodiments of the present invention, the bonded composite thus comprises the following layers:

[0362] • A first substrate A; and

[0363] • A second substrate B; and

[0364] • An adhesive tape according to the invention, which consists of the five-layer composite CTDT 1 -C' consists of and bonds the substrates A and B together.

[0365] The electrically conductive substrate of all embodiments can be, for example, a metal housing from a mobile phone or a metallized surface, such as metallized plastic or metallized glass.

[0366] The electrically non-conductive substrate of all embodiments can in particular be a housing made of a non-conductive material, such as plastic, or a battery or glass or other components designed to be non-electrically conductive, such as loudspeakers.

[0367] In all embodiments, an electrically non-conductive substrate can also be treated with an electrically conductive coating to create an electrically conductive substrate. This should be electrically conductive in both the z-direction and the xy-plane in order to effectively apply a voltage to it.

[0368] The carrier layers T, T and T' of all the aforementioned embodiments are electrically conductive.

[0369] These layers are described in more detail below. For the sake of simplicity, the term "electrically conductive carrier layer" or simply "carrier layer" is used. Depending on the embodiments described above, this refers to carrier layer T or carrier layers T and T'.

[0370] The support layers T and T' are independent of each other and can be designed the same or differently.

[0371] Preferably, the electrically conductive support layer comprises at least one metal. Particularly preferably, the metal is selected from the group consisting of copper, nickel, zinc, tin, silver, gold, aluminum, iron, chromium, and alloys of these metals. Most preferably, the metal is selected from the group consisting of aluminum, tin, copper, nickel, chromium-nickel, and nickel-iron. Aluminum or tin are highly preferred.

[0372] Preferably, the electrically conductive support layer has a layer thickness, measured in the z-direction, i.e. parallel to the stacking direction of the layer arrangement, of 10 nm (nanometers) to 50 µm (micrometers).

[0373] According to preferred embodiments of the invention, the electrically conductive carrier layer comprises a) at least one metal foil, preferably an aluminum foil or nickel-iron foil, and / or b) at least one electrically conductive textile comprising at least one metal, preferably selected from the group consisting of copper and nickel, and / or c) one or more layers of at least one vapor-deposited metal, preferably selected from the group consisting of copper, tin and aluminum, and / or d) at least one metal grid and / or e) a metallized foil, and thus a foil coated with metal, wherein the metal is preferably selected from the group consisting of aluminum, tin, chromium-nickel and nickel-iron.

[0374] It is also conceivable, in principle, that layer T or T' has a combination of two or more of the possibilities mentioned.

[0375] Metal foils, such as and preferably aluminum foils or nickel-iron foils, are known to those skilled in the art.

[0376] Preferably, the metal foil, for example and preferably the aluminum foil, has a layer thickness, measured in the z-direction, i.e. parallel to the stacking direction of the layer arrangement, of 5 to 50 pm, particularly preferably of 10 to 30 pm.

[0377] Electrically conductive textiles are known to those skilled in the art, particularly under the English term "conductive mesh". These are textile fabrics, for example made of PET (polyethylene terephthalate), coated with a metal, for example copper and / or nickel, which gives the fabric its electrical conductivity.

[0378] It is also known to those skilled in the art that metals can be directly vapor-deposited as a monolayer or multiple layer onto surfaces, such as the surface of an adhesive layer. Within the scope of the present invention, the electrically conductive carrier layer can be provided by vapor-depositing metal onto the adhesive layer D, the adhesive layer C, or the adhesive layer C'.

[0379] In the case of applied metal as a substrate layer, it is preferred in advantageous embodiments that this substrate layer laterally projects only one adjacent adhesive layer in at least one direction of extension of the layer plane, and that the other adhesive layer serves as mechanical support for this metal layer. In this case, the metal layer does not have an actual support function. Instead, the other adhesive layer acts as a support for the metal layer. For the sake of simplicity, however, the term "substrate layer" for the metal layer is retained in these embodiments as well. Preferably, the layer thickness T in this case is greater than or equal to 10 nm (nanometers), more preferably 50 to 200 nm.

[0380] However, it is also conceivable and preferred that none of the layers protrudes beyond another layer. This allows the composite of layers to be processed together easily, in particular by stamping or otherwise forming it into the desired shape. It is also conceivable and preferred that two electrically conductive substrates A and B are bonded together and a voltage is applied to these substrates.

[0381] Furthermore, metal grids of varying dimensions are known to those skilled in the art. Metal grids with suitable layer thicknesses can be produced, for example, by a fabric of appropriately thin metal threads or by punching at least one sheet of appropriate thickness.

[0382] In a metal-coated film, a non-conductive film is coated with metal to make it electrically conductive. The metal is preferably selected from the group consisting of copper, nickel, zinc, tin, silver, gold, aluminum, iron, chromium, and alloys of these metals, with aluminum, tin, chromium-nickel, and nickel-iron being particularly preferred. The film material can, in principle, be selected from any material suitable for metal vapor deposition and use as a carrier film in adhesive tapes, with polymers being particularly suitable. The material is particularly selected from polyesters and polyolefins, although a mixture of several materials is also conceivable. Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferred polyesters. Polypropylene (PP) and polyethylene (PE) are particularly preferred polyolefins.According to preferred embodiments, the film material is selected from the group consisting of PET, PEN, PE, and PP. Preferably, it is a PET (polyethylene terephthalate) film. Such a film is dimensionally stable and therefore easy to process without significant stretching or tearing. This makes it possible to permanently apply a homogeneous and continuous metal layer, ensuring that electrical conductivity, particularly in the z-direction, is permanently guaranteed across the entire film.

[0383] The coating of the foil with metal can be done in any way known to the expert.

[0384] In embodiments in which at least one electrically conductive support layer T or at least two electrically conductive support layers T and T' are present, it is preferred that these extend laterally beyond at least one adjacent adhesive layer in at least one direction of extension of the layer plane and thus have a lateral projection. A voltage can then be easily applied to this lateral projection.

[0385] In the case of the five-layer composite, the lateral projections of the electrically conductive support layers T and T' are arranged spatially separated from each other according to advantageous embodiments. This makes it easier to apply a voltage to these two projections.

[0386] In the case of vapor-deposited metal as a substrate layer, it is preferred that this substrate layer laterally extends beyond only one adjacent adhesive layer in at least one direction of extension of the layer plane, with the other adhesive layer serving as mechanical support for this metal layer. In this case, the metal layer does not have an actual support function. Instead, the other adhesive layer acts as a support for the metal layer. For the sake of simplicity, however, the term "substrate layer" is retained for the metal layer even in these embodiments. Preferably, the layer thickness T in this case is greater than or equal to 10 nm (nanometers), more preferably 50 to 200 nm.

[0387] According to further advantageous embodiments, it is also conceivable and preferred that none of the carrier layers protrudes beyond another layer, in particular an adjacent adhesive layer. This allows the composite of layers to be processed together in a simple manner, in particular by die-cutting or otherwise formed into the desired shape.

[0388] Such a structure thus has the advantage of being easy to manufacture, and the stability of the adhesive tape can also be adjusted by the carrier layer(s). It is also conceivable and preferred that two electrically conductive substrates A and B are bonded together and the voltage is applied to these substrates. In this case, the electrically conductive carrier layer is a layer that is conductive throughout in the z-direction, in particular and preferably a metal foil according to option a) above. Within the scope of the present invention, the term "laterally projecting" means any kind of lateral projection of the layer(s) in question and signifies that the layer in question extends further, particularly in the "xy" plane and thus laterally – perpendicular to the stacking direction – than the reference layer.Instead of the term "lateral overhang", the terms "lateral extension" or "lateral extension section" are also used within the scope of the present invention.

[0389] The term "lateral" here refers to any direction of extension of the layer plane "xy" perpendicular to the stacking direction of the layers "z". The term is therefore independent of the geometric shape of the adhesive tape in the "xy" plane, which can be, for example, a rectangle, as is common for adhesive tapes (see above), but also a square or a circle.

[0390] Minor variations in the dimensions of the individual layers in the "xy" plane, which result from the stamping process or similar forming processes, are not addressed here, especially since such minor material protrusions are not suitable for applying a planned stress to them due to their dimensions.

[0391] The adhesive layers C or C and C' can, in principle, be based on the same materials as the adhesive layer D, whereby the adhesive materials of layers C or C and C' need not contain electrolytes d) and organic carbonate additives e), but may contain them. Preferably, layers C or C and C' do not contain electrolytes d) and organic carbonate additives e).

[0392] According to some embodiments of the two-layer composite DC described above, the adhesive layer C is electrically conductive.

[0393] According to some embodiments of the three-layer composite DTC described above, the adhesive layer C is electrically conductive.

[0394] Similarly, the adhesive layer C and / or the adhesive layer C' of the five-layer composite CTDT'-C' can also be designed to be electrically conductive.

[0395] These layers are described in more detail below. For the sake of simplicity, the term "electrically conductive adhesive layer" is used where appropriate. Depending on the embodiments described above, this refers to adhesive layer C or adhesive layers C and / or C'. Furthermore, for the sake of simplicity, the expression "adhesive layers C or C and / or C'" is used, which refers to the respective layers in the described embodiments of the adhesive tape, comprising at least the two-layer composite, three-layer composite, or at least the five-layer composite. Adhesive layers C and C' are independent of each other and can be the same or different.

[0396] Preferably, the electrically conductive adhesive layer contains at least one metal, such as nickel, copper, silver, preferably in the form of electrically conductive metal particles and / or metallized particles, particularly preferably metal particles.

[0397] Metal particles can exist in any suitable form, including dendritic metal particles.

[0398] Metallized particles are in particular and preferably glass or polymer particles which are metallized with at least one metal, such that the previously electrically non-conductive particles are made electrically conductive by the metallization.

[0399] Particularly preferably, the electrically conductive adhesive layer contains electrically conductive particles selected from the group consisting of nickel particles, copper particles and silver-plated copper particles.

[0400] According to particularly preferred embodiments, the electrically conductive adhesive layer contains nickel particles.

[0401] Preferably, the electrically conductive adhesive layer contains 5 to 65 wt.%, particularly preferably 20 to 62 wt.%, of electrically conductive particles, in particular metal particles and / or metallized particles, based on the total mass of the adhesive.

[0402] The electrically conductive particles should preferably be no larger, or not significantly larger, than the respective thickness of the electrically conductive adhesive layer in the z-direction, as measured by a light microscope.

[0403] Preferably, the electrically conductive particles have an average particle size of 1 to 10 pm, particularly preferably of 1 to 6 pm, and again preferably of 3 to 5 pm, such as particularly 4 pm.

[0404] The electrically conductive adhesive layer is electrically conductive, at least in the z-direction.

[0405] It can also be electrically conductive in the xy-plane. If the electrically conductive adhesive layer is designed to be electrically conductive only in the z-direction, but not necessarily in the xy-direction, a smaller amount of this material is required according to preferred embodiments in which a metal, in particular metal particles, is added to achieve the electrical conductivity. This optimizes the adhesive with regard to the required conductivity, bond strength, flow behavior, and cost. Within the scope of the present invention, a layer is considered "electrically conductive" in particular if the resistance is less than 1 ohm, measured in the respective direction, here in particular in the z-direction, according to the standard MIL-DTL-83528C.

[0406] Regardless of whether the adhesive layers C or C and / or C' are electrically conductive, the following statements apply.

[0407] According to preferred embodiments of the invention, the adhesive layers C or C and / or C' are, like the adhesive layer D, reactively curable adhesives, in particular light-curable adhesives.

[0408] According to preferred embodiments of the invention, the same polymer a) and the same polymerizable compounds b) together with corresponding initiators c) are used in the adhesive layers C or C and / or C' as in the adhesive layer D.

[0409] This can cause similar substrates, referred to here as A and B, to stick together.

[0410] According to further preferred embodiments of the invention, an adhesive different from the adhesive of the adhesive layer D is used in the adhesive layers C or C and / or C'.

[0411] This allows the properties of the conductive layer to be particularly well adapted to the substrate(s) bonded via the adhesive layer C or C and / or C'. Since the adhesive layer C or C and / or C' preferably does not contain, or need not contain, an electrolyte such as an ionic liquid, its components do not need to be specifically tailored to this.

[0412] Particularly preferably, the adhesive compound of the adhesive layer D is tacky before curing and is therefore preferably an adhesive compound, and the adhesive layer D is therefore preferably an adhesive layer D.

[0413] This facilitates the processing and application of the adhesive tape, particularly in embodiments where the adhesive layer D is used as a transfer adhesive tape.

[0414] The adhesive strength allows for reliable and safe application of the reactive adhesive tapes to the substrate before curing.

[0415] To achieve the desired tackiness, the reactively curable adhesive contains, in particular, a minimum of 10 wt.%, preferably at least 15 wt.%, and especially preferably at least 20 wt.% of polymers a), particularly and for example, in combination with the preferred selection of polymers. In particular, the crystalline content should not be too high, as described for EVA and PU, for example, or the polymers should be predominantly amorphous, as in the case of poly(meth)acrylates, which are also described above.

[0416] The flowability, which affects the adhesive strength, is not negatively affected by amorphous or semi-crystalline polymers.

[0417] According to preferred embodiments, the adhesive compound of the adhesive layers C or C and / or C' is also an adhesive compound.

[0418] According to the invention, an adhesive compound is understood to be, as is generally accepted, a substance that is permanently sticky and adhesive, particularly at room temperature. A characteristic of an adhesive compound is that it can be applied to a substrate by pressure and adheres thereto, whereby the pressure to be applied and the duration of this pressure are not defined in detail. In some cases, depending on the exact type of adhesive compound, the temperature and humidity, and the substrate, the application of a short-term, minimal pressure, not exceeding a light touch for a brief moment, is sufficient to achieve the adhesive effect; in other cases, a longer duration of high pressure may be necessary.

[0419] Pressure-sensitive adhesives possess special, characteristic viscoelastic properties that result in their permanent tackiness and bonding strength. A defining characteristic is that when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The relative proportions of these two processes depend on the precise composition, structure, and degree of cross-linking of the pressure-sensitive adhesive, as well as the rate and duration of deformation and the temperature.

[0420] The proportion of viscous flow is necessary to achieve adhesion. Only the viscous components, caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high tack (also known as surface tack) and thus often also to high adhesive strength. Highly cross-linked systems, crystalline or glassy polymers, are generally not tacky or at least only slightly tacky due to a lack of flowable components.

[0421] The elastic restoring forces are necessary to achieve cohesion. They are generated, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transmission of forces acting on an adhesive bond. This allows an adhesive bond to withstand a sustained load, such as continuous shear stress, to a sufficient degree over an extended period.

[0422] To more precisely describe and quantify the degree of elastic and viscous components, as well as their ratio, the storage modulus (G') and loss modulus (G"), which can be determined using Dynamic Mechanical Analysis (DMA, according to DIN EN ISO 6721-1:2019), can be used. G' is a measure of the elastic component, and G'' is a measure of the viscous component of a material. Both quantities depend on the deformation frequency and the temperature.

[0423] The properties can be determined using a rheometer. The material under investigation is subjected, for example, to a sinusoidally oscillating shear stress in a plate-plate arrangement. In shear-stress controlled devices, the deformation is measured as a function of time, along with the time lag of this deformation relative to the application of the shear stress. This time lag is called the phase angle θ.

[0424] The memory module G' is defined as follows:

[0425] G' = (T / Y) • cos(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector).

[0426] The definition of the loss modulus G" is:

[0427] G" = (T / Y) *sin(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector).

[0428] A material is generally considered to be adhesive and is defined as adhesive within the meaning of the invention if, at room temperature, here by definition at 23°C, in the deformation frequency range of 10° to 10 1 rad / sec G' at least partly in the range of 10 3 up to 10 7Pa lies within this range, and if G" also lies at least partially within this range. "Partially" means that at least a section of the G' curve lies within the window defined by the deformation frequency range from 10° inclusive to 10° inclusive. 1 rad / sec (abscissa) and the range of G' values ​​including 10 3 up to and including 10 7 Pa (ordinate) is spanned. The same applies to G".

[0429] Preferably, the adhesive compound exhibits in the deformation frequency range of 10° to 10 1 rad / sec at 23 °C a storage module G' and a loss module G" in the range of 10 3 up to 10 7Pa, determined according to DIN EN ISO 6721-1:2019. To achieve viscoelastic properties, the monomers on which the polymers underlying the pressure-sensitive adhesive are based, as well as any other components of the adhesive, are selected in such a way that the adhesive has a glass transition temperature (according to DIN 53765:1994-03) below the application temperature (i.e., usually below room temperature (23 °C)). By suitable cohesion-enhancing measures, such as crosslinking reactions (formation of bridge-forming links between the macromolecules), the temperature range in which a polymer compound exhibits pressure-sensitive properties can be increased and / or shifted. The application range of the pressure-sensitive adhesive can thus be optimized by adjusting the flowability and cohesion of the compound.

[0430] In particular, an adhesive compound has a glass transition temperature of < 23 °C, determined according to DIN 53765 :1994-03.

[0431] Another object of the present invention is the production of the adhesive tape according to the invention.

[0432] The adhesive mass of the adhesive layer D and, depending on the embodiment, further adhesive masses are produced by known methods and formed into layer form, in particular by spreading or by extrusion.

[0433] Furthermore, one or more drying steps may be carried out.

[0434] The production of the reactive adhesive tape according to the invention is carried out, in particular, under exclusion of UV light or visible light of the wavelength by which the respective initiator system, e.g., the respective photoredox catalyst, is excited, especially violet and blue light. These are generally wavelengths of less than 500 nm. This exclusion can generally be achieved with commercially available yellow light lamps, as well as by covering normal light sources that have UV components and / or violet and blue light components in their wavelength spectrum with commercially available UV-protective yellow light films.

[0435] The reactively curable adhesive compound according to the invention is produced in a manner known to those skilled in the art.

[0436] In particular, the individual components are weighed out in suitable proportions and mixed together until a homogeneous mixture is formed.

[0437] The reactive curing adhesive tape according to the invention comprises at least one layer D of the reactive curing adhesive compound according to the invention. In the production of the reactive curing adhesive tape according to the invention, a film, a foil, a layer, a carrier, an adhesive film, a pressure-sensitive adhesive film, preferably a release liner or a release paper, is coated with the mixture of the adhesive compound.

[0438] The coating is applied using standard techniques known in the prior art.

[0439] For storage, the resulting layer or the reactive adhesive tape according to the invention is covered with a separating liner or paper.

[0440] Laminating several layers on top of each other is carried out in a manner known to those skilled in the art, wherein the layers are placed on top of each other in such a way as to obtain in particular a layer composite DC or DTC, wherein T is arranged between D and C, or C'-T'-DTC as a double-sided adhesive tape.

[0441] The provision of the support layers T or T' can be done in various ways, as already explained above.

[0442] It is conceivable that a) a metal foil, in particular an aluminum foil, and / or b) an electrically conductive mesh and / or d) at least a metal grid and / or e) a metal-coated PET film is placed between the respective adhesive layers.

[0443] Furthermore, c) metal particles can be vapor-deposited directly onto the surface of the adhesive layer D or C or C'.

[0444] Another object of the present invention is the production of a bonded composite using the adhesive tape according to the invention.

[0445] The inventive method for producing a bonded composite and thus for bonding two substrates, preferably at room temperature, using the inventive reactive adhesive tape comprises the following steps

[0446] A) Applying the reactive adhesive tape to a first substrate

[0447] B) Activation of the reactive adhesive tape by irradiation with UV light or blue light, wherein blue light in particular and for example has a wavelength of 365 nm, preferably by irradiation from a UV LED lamp.

[0448] C) Adding a second substrate to the reactive adhesive tape.

[0449] The adhesive tape according to the invention can be any of the described embodiments. In any case, the adhesive tape according to the invention comprises at least one reactively curable adhesive layer D, which is activated in the process for producing a bonded composite according to step B).

[0450] The activation according to step B) can take place before or after step A).

[0451] Preferably, activation according to step B) takes place before step C), especially if activation through the first and second substrates is not possible.

[0452] In this process, particularly when carried out on an industrial scale, irradiation is preferably performed with a wavelength of 365 nm or 385 nm, more preferably with 365 nm.

[0453] Irradiation can also preferably be carried out with a 460 nm LED radiation source. The results obtained by irradiation with 365 nm light are representative of irradiation with light of a wavelength of 460 nm or 385 nm.

[0454] In embodiments in which further layers C or C' are designed to be reactively curable, these are also activated accordingly, preferably also by irradiation with UV light or blue light according to step B).

[0455] The expert will also adapt the sequence of steps to the respective substrates and the nature and construction of the adhesive tape in this case.

[0456] The adhesive tape according to the invention is in particular a double-sided adhesive tape in which, depending on the embodiment, two surfaces of the adhesive layer D (transfer adhesive tape or carrier layer embedded in the adhesive layer permeable in the z-direction for electrolytes) or one surface of the first adhesive layer D and one surface of the second adhesive layer C (two-layer composite DC or three-layer composite DTC) or one surface each of the adhesive layers C and C' (five-layer composite CTDT'-C') are available for bonding substrates.

[0457] Advantageously, the outer, exposed surfaces of the adhesive layers of the adhesive tape according to the invention can be equipped with anti-adhesive materials such as a release paper or a release film, also called a liner. A liner can also be a material coated with an anti-adhesive finish on at least one side, preferably both sides, such as a material siliconized on both sides. A liner, or more generally, a temporary carrier, is not a component of the adhesive tape itself, but merely an aid for its manufacture, storage, and / or further processing by die-cutting. Furthermore, unlike a permanent carrier, a liner is not permanently bonded to an adhesive layer, but rather functions as a temporary carrier, i.e., a carrier that can be peeled off the adhesive layer. In this application, "permanent carriers" are also referred to simply as "carriers."

[0458] The thickness of the individual adhesive layer(s) (in the z-direction) is preferably from 10 to 300 µm, particularly preferably from 15 to 150 µm, most preferably from 20 to 100 µm, and most preferably from 25 to 70 µm.

[0459] In the embodiments of the two-layer composite DC, three-layer composite DTC and the five-layer composite CTDT'-C', the adhesive layers D and C or D and C and D and C' have different layer thicknesses according to preferred embodiments, wherein the thickness of the adhesive layer D is, for example, less than that of the adhesive layers C or C and C'.

[0460] According to further preferred embodiments, layers D and C or D, C and C' have the same layer thickness.

[0461] If the thickness of layer D is too high, it may become uneconomically expensive due to the electrolytes it contains.

[0462] Another object of the present invention is the use of the reactively curable adhesive compound or the reactively curable adhesive tape according to the invention for bonding components in electronic, optical or precision mechanical devices, automobiles, medical devices and dental devices.

[0463] The use of the reactively curable adhesive compound or the reactively curable adhesive tape according to the invention is preferred for producing bonds on materials selected from plastic, metal, glass or ceramic, and the use of the reactively curable adhesive compound or the reactively curable adhesive tape according to the invention as an adhesive in the manufacture of electronic, optical or precision mechanical devices.

[0464] Such portable devices include, in particular:

[0465] Cameras, digital cameras, photography accessories (such as light meters, flash units, apertures, camera bodies, lenses, etc.), film cameras, video cameras, small computers (mobile computers, pocket computers, calculators), laptops, notebooks, netbooks, ultrabooks, tablet computers, handhelds, electronic calendars and organizers (so-called "Electronic Organizers" or "Personal Digital Assistants", PDAs, palmtops), modems; computer accessories and control units for electronic devices, such as mice, drawing pads, graphics tablets, microphones, speakers, game consoles, gamepads, remote controls, touchpads;

[0466] Monitors, displays, screens, touch-sensitive screens (sensor screens, "touchscreen devices"), projectors;

[0467] Reading devices for electronic books (“e-books”);

[0468] Small television sets, pocket televisions, film players, video players, radios (including small and pocket radios), Walkmans, Disemons, music players for e.g. CD, DVD, Blu-ray, cassettes, USB, MP3, headphones, cordless phones, mobile phones, smartphones, two-way radios, hands-free devices, personal alarm devices (pagers, beepers); mobile defibrillators, blood glucose meters, blood pressure monitors, pedometers, pulse monitors;

[0469] Flashlights, laser pointers;

[0470] Mobile detectors, optical magnifying devices, long-range vision devices, night vision devices, GPS devices, navigation devices, portable satellite communication interface devices;

[0471] Data storage devices (USB sticks, external hard drives, memory cards); and wristwatches, digital watches, pocket watches, chain watches, stopwatches.

[0472] The following are some examples to further illustrate the invention.

[0473] Testing methods

[0474] Unless otherwise stated, all measurements are performed at 23 °C and 50% relative humidity. The mechanical and adhesive properties were determined as follows:

[0475] Molecular weight M n , M w

[0476] The data on the numerical mean molecular weight M n or weight-average molecular weight M w This document refers to the 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 performed at 25 °C. A PSS-SDV type column, 5 µm, 10 3 Ä, 8.0 mm * 50 mm (Specifications here and below in the order: type, particle size, porosity, inner diameter * length; 1 Ä = 10 -10m) is used. For separation, a combination of columns of type PSS-SDV, 5 pm, 10 is used. 3 Ä and 10 5 A and 10 6 Columns 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 for polar molecules was performed against PMMA standards (polymethyl methacrylate calibration), and for other molecules against PS standards (polystyrene calibration).

[0477] thickness

[0478] The thickness of an adhesive layer can be determined by measuring the thickness of a section of the adhesive layer applied to a liner, defined in terms of its length and width, and subtracting the (known or separately determinable) thickness of a section of the liner itself of the same dimensions. The thickness of the adhesive layer can be determined using commercially available thickness gauges (probe gauges) with accuracies of less than 1 µm deviation. If thickness variations are detected, the mean value of measurements taken at at least three representative locations is reported, specifically excluding measurements taken at creases, folds, spots, and the like.

[0479] Just as the thickness of an adhesive layer can be determined, the thickness of an adhesive tape (adhesive strip) or a substrate can also be determined analogously using commercially available thickness gauges (touch-type testers) with accuracies of less than 1 pm deviation. If thickness variations are detected, the mean value of measurements taken at at least three representative locations is given, specifically excluding measurements taken at creases, folds, spots, and the like.

[0480] DSC

[0481] Glass transition points – also known as glass transition temperatures – of polymers or polymer blocks are determined by measurements using Dynamic Scanning Calorimetry (DSC) according to DIN 53765:1994-03, specifically sections 7.1 and 8.1, but with uniform heating and cooling rates of 10 K / min in all heating and cooling steps (see DIN 53765:1994-03; section 7.1; note 1). The sample weight is 20 mg. The melting point or softening point of polymers or polymer blocks is also determined in this way.

[0482] Bond strengths - Push-Out see below

[0483] The following examples of reactively curable adhesives or adhesive tapes according to the invention, comprising at least one adhesive layer D, were produced, bonded between substrates, and subsequently electrically released by applying a voltage. The adhesives of layer D were each reactively curable by UV radiation at room temperature and tacky before activation. Table 1: Chemicals used

[0484] <

[0485] <

[0486]

[0487] Production of Polymer P2

[0488] A conventional 4 L reactor for radical polymerizations was filled with 320 g of benzyl acrylate and 273 g of ethyl acetate / isopropanol (96 / 04). After 45 minutes of nitrogen gas purging with stirring, the reactor was heated to 58 °C and 0.2 g of 2,2'-azobis(2-methylbutryonitrile) was added. A further 480 g of benzyl acrylate and 377 g of ethyl acetate were added continuously for 2 hours. Subsequently, the external heating bath was heated to 65 °C and the reaction was carried out at this constant temperature. After 1 h and after 1.5 h of reaction time, 0.3 g and 0.3 g of 2,2'-azobis(2-methylbutryonitrile) were added, respectively. To reduce the residual monomers, 0.12 g of di(4-tert-5-butylcyclohexyl)peroxydicarbonate was added after 6 h and again after 7.5 h. The mixture was diluted with 160 g of ethyl acetate after 2 h and 4 h. The reaction was stopped after 24 h and the mixture was cooled to room temperature.

[0489] Production of reactive curing adhesives

[0490] Tables 2 and 3 show the proportions of the individual masses in wt.%. These naturally add up to 100 wt.%.

[0491] The individual components are weighed out in the specified proportions, and the mixture is placed on the rolling bench for 24 hours. After rolling, the mixtures are transparent, homogeneous, and free of bubbles.

[0492] Preparation of layer D of the reactive curing adhesive as a transfer tape: The mixtures are spread onto a release liner on a conventional spreading bar (on the siliconized side). The spreads are then dried for 15 minutes at room temperature. Afterward, the spreads are further dried for 15 minutes at 80°C in a drying oven. The spreads are then left to cool for 1 hour at 23°C. A second release liner is then laminated onto the spread. The spreads have a layer thickness of 100 µm (without the liner) and a total thickness of 200 µm with the liners.

[0493] Production of the bonded composites

[0494] The following components are provided: a circular first substrate (1) (SUS, VA-1.4301 steel (mirror-polished on one side), 3 mm thick) with a diameter of 21 mm; a square second substrate (2) (SUS, VA-1.4301 steel (mirror-polished on one side), 2 mm thick) with sides of 40 mm and a circular, centrally located opening (bore) of 9 mm diameter; and the adhesive tape sample to be tested, which was fully bonded and then cut out in a circular pattern along the circular substrate. The resulting total bonded area is 283 mm². 2 .

[0495] The liner is removed, and the adhesive layer is adhered to a round substrate (SUS) cleaned with MEK and acetone. Any excess material on the sides is trimmed with scissors, if necessary. Then the second liner is removed, and the adhesive film now stuck to the substrate is tested for 10 seconds at 37% intensity (corresponding to 4500 mJ / cm²). 2The first substrate (purified SUS) is irradiated in a UV cube with UV light at a wavelength of 365 nm. Within 30 seconds, the second substrate (purified SUS) is bonded to this setup. The sample is then compressed at -100 N for 30 seconds before being stored for 3 days under standard conditions (RT + ~60% RH) for curing.

[0496] Push-Out (SUS-SUS) - initial (bonding strength)

[0497] The push-out test provides information about the bond strength of an adhesive product in the direction of the adhesive layer normal.

[0498] After storage, the bonded assembly is clamped in a specimen holder so that it is horizontally aligned. The test specimen is placed in the specimen holder with the disc (substrate (1)) facing downwards, and the bond strength is measured in a device (Zwick). For this purpose, a steel punch with a diameter of 7 mm is inserted through the circular opening in substrate (2), and the force required to separate the circular substrate (1) from the square substrate (2) is determined. The measured force is divided by the bonded area, and the force is expressed in MPa.

[0499] Three samples per product are tested and the average value is given as a measure of the bond strength.

[0500] The results are summarized in Tables 2 and 3.

[0501] Subsequently, samples of the above-mentioned examples were prepared again and tested for electrical re-removability.

[0502] After curing and storage, a voltage was applied to each of the two steel plates as representatives of conductive substrates A and B.

[0503] The applied stress and the duration for which the stress was applied are given in Tables 2 and 3. The bond strengths after application of the stress were determined according to the method described above. The results are also summarized in Tables 2 and 3.

[0504] In the comparative example V3, the adhesive strengths before and after the application of a stress could not be determined (nb) because the adhesive tape failed cohesively during sample preparation when the liner was removed. Table 2

[0505]

[0506] Table 3

[0507]

[0508] As the tests on bond strength and removability in the examples according to the invention show, the bond strength is significantly reduced when an ionic liquid is present in the adhesive layer D and a voltage is applied. Thus, the bonded substrates can be separated from each other again without much effort. Furthermore, removal is achieved completely or almost completely without adhesive residue.

[0509] The examples according to the invention also exhibit an adhesive tackiness before curing, which can be seen, for example, in an adhesive force of at least 1 N / cm according to ASTM D3330 (peel adhesion on steel, peel speed of 300 mm / min at an angle of 180°; measurement of at least three test specimens and subsequent averaging).

Claims

Patent claims 1. Reactive curing adhesive containing at least the following components: a) at least one polymer, and b) at least one polymerizable compound, and c) at least one initiator, and d) at least one electrolyte, wherein the electrolyte is preferably an ionic liquid, and e) at least one organic carbonate additive, preferably at least one organic aliphatic carbonate additive.

2. Reactively curable adhesive according to claim 1, characterized in that the anion of the electrolyte, preferably the ionic liquid, d) is selected from the group consisting of BF4 _ , PF6 _ and SbF6 _ and / or the cation of the electrolyte, preferably the ionic liquid, d) is selected from the group consisting of 1-butyl-3-methylimidazolium (BMIM), 1-hexyl-3-methylimidazolium (HMIM) and 1-octyl-3-methylimidazolium (OMIM).

3. Reactive curing adhesive according to one of claims 1 or 2, characterized in that it contains at least 0.5 wt.% and / or up to 20 wt.% of organic carbonate additives e).

4. Reactively curable adhesive compound according to one of the preceding claims, characterized in that the organic carbonate additive e) contains an organic cyclic carbonate e1 ) with a molar mass of 80 to 200 g / mol, preferably of 80 to 120 g / mol.

5. Reactively curable adhesive according to one of the preceding claims, characterized in that the organic carbonate additive e) contains an organic cyclic carbonate e1) with the general structure according to formula I): where R 1 and R 2 each are independently the same or different and each is selected from the group consisting of hydrogen and alkyl groups, and wherein R 3 and R 4each is independently the same or different and is each selected from the group consisting of hydrogen, alkyl groups, aromatic groups, alkyl halides, halogen groups and vinyl groups.

6. Reactive curing adhesive according to one of the preceding claims, characterized in that the organic carbonate additive e) contains a polycarbonate polyol e2), wherein the polycarbonate polyol is selected from the group consisting of linear, aliphatic polycarbonate diols.

7. Reactive curing adhesive according to one of the preceding claims, characterized in that the organic carbonate additive e) comprises an aliphatic cyclic carbonate e1) selected from the group consisting of ethylene carbonate, propylene carbonate or a mixture thereof, wherein propylene carbonate is particularly preferred.

8. Reactively curable adhesive according to one of the preceding claims, characterized in that it is an epoxy-based adhesive that can be cured by visible light and / or UV light, wherein it contains at least one polymerizable epoxy compound b1) as polymerizable compound b) and at least one cationic initiator d) as initiator c).

9. Reactively curable adhesive according to one of the preceding claims, characterized in that it is a radically curable adhesive using visible light and / or UV light, wherein it comprises at least one radically polymerizable compound b2) as polymerizable compound b) and at least one radical initiator c2) as initiator c) and additionally at least one photoredox catalyst f).

10. Reactive curing adhesive tape comprising at least one layer D of a reactive curing adhesive compound according to one of claims 1 to 9.

11. Reactive curing adhesive tape according to claim 10 characterized in that it is a transfer adhesive tape and consists of the adhesive compound layer D.

12. Reactive curing adhesive tape according to claim 10, characterized in that it additionally comprises at least one carrier layer T.

13. Bonded composite comprising at least the following layers: • A first substrate A; and • A second substrate B; and • An adhesive tape obtained by curing the reactively curable adhesive tape according to one of claims 10 to 12, and which is arranged between the substrate A and the substrate B and bonds the substrates A and B together, wherein in particular either the substrate A and the substrate B or at least one of the substrates and the adhesive tape are electrically conductive at at least one location or neither of the substrates and the adhesive tape are electrically conductive at two different locations.

14. Method for electrically separating the bond according to claim 13, comprising at least the following method steps: i.) Applying a voltage to two different electrically conductive points of the composite, the voltage preferably being 1 to 50 V.

15. Use of the reactive curing adhesive according to any one of claims 1 to 9 or of the adhesive tape according to any one of claims 10 to 12 for bonding components in electronic, optical or precision mechanical devices, automobiles, medical devices and dental devices.

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