Curable (METH)acrylate composition, and detachable bonded assembly

Abstract

The present invention relates to curable compositions containing at least one compound having (meth)acrylate end groups, at least one photoinitiator, at least one thermally expandable material, and, optionally, additives, and to the use thereof in a bonded assembly comprising a substrate, a cured curable composition which is applied to the substrate, and a cured adhesive composition which is applied to the cured curable composition, in particular for adhesive bonds in the automotive sector. The present invention also relates to a method for detaching the bonded assembly, comprising the following steps: heating the bonded assembly to at least the expansion temperature of the thermally expandable material for at least 5 seconds such that an expansion temperature of at least 80°C is reached; separating the cured composition from the substrate. The curable composition can be applied and cured rapidly and easily, and the bonded assembly has a high tensile shear strength during use and has a low debonding strength upon being subjected to a debonding stimulus, i.e. can be detached rapidly and easily.

Description

[0001] Hardenable (meth)acrylate composition and removable adhesive bond

[0002] Technical field

[0003] The invention relates to curable (meth)acrylate compositions and their application in adhesive bonding, in particular for bonding in the automotive sector, and methods for removing the adhesive bonding.

[0004] State of the art

[0005] Curable compositions based on (meth)acrylate compounds are often used as adhesives or adhesive coatings because they exhibit good mechanical and optical stability and, in particular, very good adhesion to many substrates. This also makes them suitable for applications as adhesion promoters (primers).

[0006] Society and industry are increasingly demanding sustainable solutions that enable a circular economy and the recycling of materials used. Adhesives can make a significant contribution to this, as they are used in many applications and, in particular, bond different materials together in composites. However, for the economically viable recycling of bonded products after use or for repair purposes, these bonds must be able to be separated. One possible approach is so-called "debonding on demand," in which an adhesive bond can be detached from a substrate using a well-defined stimulus. The separation process should separate the materials with a sufficiently high level of quality. Therefore, harsh mechanical, chemical, or thermal processes that place excessive stress on the individual materials are unsuitable.Existing adhesive systems are also reaching their limits in many applications, as disassembling the bond is often costly or results in damage to the bonded parts. Specific repair of a part is often impossible. Particularly for automotive and battery components, which use expensive and rare raw materials, the possibility of repair and reuse is desirable not only for environmental but also for economic reasons. Therefore, an adhesive must be used that meets the necessary requirements during use but can be easily removed at the end of the product's lifespan after the application of a stimulus.

[0007] One possible strategy for "debonding on demand" applications is the use of an adhesion promoter with thermo-reversible substances (e.g., products of the Diels-Alder reaction). Similarly, the current state of the art for "debonding on demand" adhesion promoters consists of pressure-sensitive adhesives (PSAs) based on epoxy, polyurethane, or (meth)acrylate compositions.

[0008] Publication JP2023088827A describes a PSA adhesive tape which can be easily and quickly removed from the adhesive surface without damaging the adhesive surface through excessive heat.

[0009] Patent WO2023037914A1 describes a

[0010] Adhesive composition based on unsaturated polyurethanes suitable for a thermally removable adhesive film.

[0011] A previously unresolved problem when using a removable primer layer in "debonding on demand" applications is the time and additional effort required to incorporate this primer layer into the adhesive bond. Particularly when using epoxy-based primers, the long waiting time due to slow curing is a significant issue.

[0012] Therefore, there is a need for a curable composition that can be applied and cured quickly and in a simple process, that meets the mechanical requirements of an adhesive bond, and that can be removed again in the sense of a "debonding on demand" functional layer. Description of the invention

[0013] The object of the present invention is therefore to provide a curable composition suitable as a functional layer in a "debonding on demand" application, which can be applied and cured quickly and can be removed under a thermal stimulus. It is also an object of the present invention to provide an adhesive bond and a process for removing this adhesive bond.

[0014] Particularly surprising is the fact that the adhesive bond according to the invention, in preferred embodiments, has a high tensile shear strength in use (> 4 MPa), but also a low debonding strength after a debonding stimulus (< 0.5 MPa).

[0015] The curable composition can be used as a functional layer with many different substrates and adhesive compositions and can therefore be used in many different areas.

[0016] Another advantage of UV-Vis curing of the composition according to the invention is that the application and curing of the curable composition can take place within 30 seconds, which offers an enormous process advantage compared to the compositions currently used in the prior art.

[0017] This makes the inventive curable composition particularly suitable as a functional layer in "debonding on demand" applications, especially in the automotive industry, in vehicle construction or also in bonding batteries of electric vehicles.

[0018] This problem is solved with a curable composition as described in claim 1. Further aspects of the invention are the subject of further independent claims. For example, an adhesive bond and a process for removing this adhesive bond are also the subject of this invention. Particularly preferred embodiments of the invention are the subject of the dependent claims.

[0019] Ways to implement the invention

[0020] The invention relates to a curable composition containing HZ

[0021] - at least one compound with (meth)acrylate end groups V,

[0022] - at least one photoinitiator P;

[0023] - at least one thermally expandable material E;

[0024] - optional additive AD.

[0025] The term "(Meth)acrylate" should be understood as "methacrylate" or "crylate".

[0026] Substance names beginning with "Poly", such as polyol or poly(meth)acrylate, refer here to substances that formally contain two or more of the functional groups mentioned in their name per molecule.

[0027] In this document, "molecular weight" means the defined and discrete molar mass (in grams per mole) of a molecule or part of a molecule.

[0028] The "average molecular weight" refers to the number mean Mn of an oligomeric or polymeric mixture, especially a polydisperse mixture, of molecules or radicals, which is usually determined by gel permeation chromatography (GPC) against a polystyrene standard.

[0029] A dashed line in the formulas of this document represents the bond between a substituent and its corresponding molecular residue, unless otherwise specified. Unless otherwise specified, all industry standards or other norms mentioned in this document refer to the version of the industry standard or other norm that was valid at the time the patent application was filed.

[0030] The terms "mass" and "weight" are used synonymously in this document. Thus, a "weight percentage" (wt%) is a percentage of the mass which, unless otherwise specified, refers to the mass (weight) of the entire composition or, depending on the context, to the entire molecule.

[0031] An isocyanate group is described as "aliphatic" if it is directly bonded to an aliphatic or cycloaliphatic carbon atom. Isocyanates with exclusively aliphatic isocyanate groups are accordingly called "aliphatic isocyanates".

[0032] A monomeric diisocyanate with aliphatic isocyanate groups is called a "monomeric aliphatic diisocyanate".

[0033] A polymer is called a "polyetherurethane polymer" which has ether groups as repeating units and also contains urethane groups.

[0034] A polymer is called a "urethane acrylate polymer" which has urethane groups as repeating units and also contains acrylate groups.

[0035] A radical chain reaction, or chain polymerization, describes the mechanism of polymerization of (meth)acrylate-containing compounds. An initiator is used to generate free radicals that start the polymerization. These radicals add to the double bond of the (meth)acrylate monomers, forming a (meth)acrylate radical. Through repeated addition of further (meth)acrylate monomers to the resulting radicals, the polymer chain grows until the chain is terminated by a termination reaction.

[0036] In this document, UV-Vis light or UV-Vis radiation refers to radiation in the ultraviolet (UV) and visible (Vis) spectrum, particularly the wavelength range between 150 nm and 750 nm. Preferred wavelengths for activating the corresponding preferred photoinitiators used as radical initiators are in the range between 300 nm and 600 nm, particularly between 350 nm and 500 nm. Such wavelengths, in combination with suitable photoinitiators, enable sufficiently rapid curing while simultaneously minimizing exposure to potentially damaging, higher-energy radiation.

[0037] A photoinitiator is an initiator that is activated by light in the ultraviolet (UV) or visible (Vis) spectrum and enables the formation of radicals. The composition according to the invention is thus cured by brief irradiation with UV-Vis light of a suitable wavelength. The advantage of using a UV-Vis-activated photoinitiator is the rapid curing after very short irradiation, usually within seconds, without the need for heat input. UV radiation sources are cost-effective and can be used flexibly. Photoinitiators activatable in the visible spectrum can also be activated by sunlight or a lower-energy radiation source (especially blue LEDs), which can be advantageous in some applications.

[0038] Photoinitiators for radical chain reactions are divided into two types. Type 1 photoinitiators generate radicals directly through photofragmentation, usually via alpha cleavage. The resulting radical then directly triggers chain polymerization. Type 2 photoinitiators, on the other hand, abstract a hydrogen atom from a neighboring molecule. This then initiates chain polymerization. Tertiary amines are often added because they form particularly effective initiating radicals and thus increase reactivity.

[0039] In this document, the term "hollow" refers to the absence of any solid components in a sealed space. Thus, hollow objects, such as hollow spheres or hollow globes, can contain gaseous components like ambient air or any gas in general. Likewise, a volatile liquid with high vapor pressure can be contained within such a hollow globe.

[0040] In this document, the term "expansion temperature" refers to the temperature range at which an expandable material expands. The expansion temperature begins at the initial temperature of the expansion.

[0041] In this document, the term "coefficient of expansion" refers to how much an expandable material expands when its temperature changes, compared to its volume at room temperature. The coefficient of expansion is usually expressed as a percentage (%).

[0042] Hardenable composition HZ

[0043] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the curable composition is curable by UV-Vis radiation, in particular in the range of wavelengths from 315 to 415 nm.

[0044] Preferably, the curable composition HZ is irradiated with UV-Vis radiation for at least 5 seconds, particularly preferably for at least 15 seconds, and most preferably for at least 30 seconds. Preferably, the curable composition HZ is irradiated with electromagnetic waves in the wavelength range of 300 to 750 nm, particularly from 350 to 500 nm.

[0045] In a preferred embodiment, the curable composition HZ is irradiated with an LED-UV lamp using light in the wavelength range of 315 to 415 nm. The UV-A light can also be used in conjunction with ambient light, particularly from other lamps and lighting devices, in the visible light range (380-750 nm).

[0046] Irradiation of the curable composition with UV-Vis radiation generates radicals, which in turn initiate radical chain polymerization. Polymerization of the compounds with (meth)acrylate end groups V results in a covalently cross-linked composition and a macroscopically cured composition.

[0047] Compound with (meth)acrylate end groups V

[0048] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the compound with (meth)acrylate end groups V does not comprise urethane acrylates.

[0049] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the compound with (meth)acrylate end groups V comprises monomers with (meth)acrylate end groups, preferably monofunctional, multifunctional, in particular difunctional and / or trifunctional (meth)acrylate monomers, especially preferably a mixture of difunctional and trifunctional (meth)acrylate monomers.

[0050] A compound with (meth)acrylate end groups V according to the present invention contains at least one radically polymerizable group of formula (I) where

[0051] R 1 represents a water atom or a methyl group, preferably a hydrogen atom;

[0052] R 2a linear or branched monovalent hydrocarbon residue with 2 to 20 carbon atoms, optionally containing one or more CC multiple bonds and optionally containing cyclic residues, in particular cycloaliphatic residues and / or aromatic residues, and / or heteroatoms, preferably oxygen.

[0053] In a preferred embodiment, the compound with (meth)acrylate end groups V according to the present invention contains several radically polymerizable groups, i.e., it is multifunctional. Possible multifunctional (meth)acrylate monomers correspond to formula (II). q

[0054] Where

[0055] R 1 represents a water atom or a methyl group, preferably a hydrogen atom;

[0056] Y represents a linear or branched hydrocarbon residue with 2 to 20 carbon atoms, optionally containing heteroatoms, preferably oxygen; q represents a value of 1 to 2. A difunctional (meth)acrylate monomer of a compound with (meth)acrylate end groups V thus preferably corresponds to a structure of formula (II), where q represents a value of 1.

[0057] In a further preferred embodiment, the curable composition HZ comprises in particular a compound with (meth)acrylate end groups V of formula (III) where

[0058] R 1 represents a water atom or a methyl group, preferably a hydrogen atom;

[0059] X represents a linear or branched hydrocarbon residue with 2 to 10 carbon atoms, optionally containing heteroatoms, preferably oxygen.

[0060] In a particularly preferred embodiment, X from formula (III) corresponds to a trimethylpropane after removal of the OH groups, or to a polymeric diol after removal of the OH groups.

[0061] In a particularly preferred embodiment, the curable composition HZ comprises in particular a compound with (meth)acrylate end groups.

[0062] V of formula (IV) In a further particularly preferred embodiment, X from formula (III) corresponds to a diol, in particular a pentanediol after removal of the OH groups, or a polymeric diol after removal of the OH groups.

[0063] The curable composition HZ comprises in a particularly preferred form

[0064] In particular an embodiment of a compound with (meth)acrylate end groups

[0065] V of the formula (V) where a, b and c represent values ​​from 1 to 20, preferably 1 to 10, particularly preferably 1 to 5.

[0066] In a further preferred embodiment, X from formula (III) corresponds to an ether and / or ester and / or β-hydroxy ether.

[0067] In a further preferred embodiment, the curable composition according to the invention is characterized in that the compound with (meth)acrylate end groups V comprises a prepolymer with polyether and / or polyester and / or β-hydroxy ether repeating units. β-hydroxy ether repeating units can, for example, be derived from epoxy groups.

[0068] Suitable examples include the commercially available chemicals Ebecryl.

[0069] 3416 from Allnex (65% Bisphenol A based epoxy acrylate in tripropylene glycol diacrylate thinner) or Ebecryl 3300 from Allnex (65% Bisphenol A based epoxy acrylate oligomer in dipropylene glycol diacrylate thinner).

[0070] In a particularly preferred embodiment, the curable composition HZ comprises in particular a compound with (meth)acrylate end groups.

[0071] V of the formula (VI)

[0072] In a further embodiment, the curable composition HZ according to the invention is characterized in that the compound with (meth)acrylate comprises end groups V of rubber-based acrylates, also known as acrylate-terminated rubbers or rubber-modified acrylates. Acrylate-terminated rubbers are a class of materials that combine the elastomeric properties of rubber with the reactivity and versatility of acrylate groups.

[0073] Rubber-based acrylates are typically synthesized by introducing functional acrylate groups into the backbone of a rubber polymer. This can be achieved through various chemical reactions, such as radical-initiated emulsion polymerization or suspension polymerization.

[0074] Preferably, the curable composition according to the invention contains HZ between 70 and 95 wt.%, particularly preferably between 75 and 90 wt.%, based on the total composition, of the compound with (meth)acrylate end groups V. Photoinitiator P

[0075] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the photoinitiator P comprises at least one type 1 and / or at least one type 2 photoinitiator, preferably a mixture of type 1 and type 2 photoinitiators.

[0076] UV-Vis-activated photoinitiators are known to those skilled in the art in the field of radically curable compositions. For the present invention, in principle all common photoinitiators suitable as photoinitiator P are appropriate for the radical curing of vinyl groups, in particular (meth)acrylates, and can usually be used without restriction. However, it is advantageous to ensure that the photoinitiators are readily miscible with the respective composition.

[0077] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the photoinitiator P is solid and / or liquid at 23°C.

[0078] Commonly used type 1 photoinitiators are derived from acylphosphine oxides. Commonly used type 2 photoinitiators are derived from α-hydroxy, α-alkoxy, or α-amino aryl ketones, especially benzophenones and their derivatives, and thioxanthones.

[0079] Suitable photoinitiators P include aldehydes and their substituted derivatives, ketones and their substituted derivatives, quinines and their substituted derivatives; thioxanthones, such as 2-isopropylthioxanthone and 2-dodecylthioxanthone, and certain chromophore-substituted vinylhalomethylsymtriazines, such as 2-4-bis-(trichloromethyl)-6-(3',4'-dimethoxyphenyl)-sym-triazine and acyl phosphine oxides, such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.Specific examples of suitable type 1 photoinitiators that can be activated in the UV-Vis range are bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one and ethyl(2,4,6-trimethylbenzoyl)phenyl phosphinate (available as IGM Resins OMNIRAD® 2022), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (available as BASF LUCIRIN® TPO), 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide (available as BASF LUCIRIN® TPO-L), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (available as Ciba IRGACURE® 819), 2,4,6-trimethylbenzyl-diphenylphosphine oxide and other acylphosphines.

[0080] Specific examples of suitable type 2 photoinitiators that can be activated in the UV-Vis range are 2-methyl-1-(4-methylthio)phenyl-2-(4-morpholinyl)-1-propanone (available as Ciba IRGACURE® 907) and 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methylpropan-1-one (available as Ciba IRGACURE® 2959); 2-benzyl-2-dimethylamino 1-(4-morpholinophenyl)butanone-1 (available as Ciba IRGACURE® 369); 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)-benzyl)-phenyl)-2-methylpropan-1-one (available as Ciba IRGACURE® 127); 2-Dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butanone (available as Ciba IRGACURE® 379);

[0081] Titanocene; isopropylthioxanthone; 1-hydroxycyclohexylphenyl ketone; benzophenone; 2,4,6-trimethylbenzophenone; 4-methylbenzophenone; diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide; ethyl trimethylbenzoylphenylphosphine; oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone); 2-hydroxy-2-methyl-1-phenyl-1-propanone; benzyl dimethyl ketal; and mixtures thereof. Other UV / VIS-activated type 2 photoinitiators are 2,2-dimethyl-2-hydroxyacetophenone; 1-hydroxy-1-cyclohexyl phenyl ketone; 2,2-dimethoxy-2-phenylacetophenone; benzophenone.

[0082] Particularly preferred are mixtures of type 1 and type 2 photoinitiators, especially bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-phenyl-2-hydroxy-2-methylpropanone; mixtures of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-hydroxycyclohexylphenyl ketone; bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and camphorquinone.

[0083] Examples of cationic photoinitiators are iodonium and sulfonium salts. Preferred photoinitiators include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one and / or 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one.

[0084] Particularly preferred as photoinitiator P are bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one and ethyl phenyl(2,4-6-trimethylbenzoyl)phosphinate and mixtures thereof.

[0085] Preferably, the curable composition HZ according to the invention contains between 0.1 and 5 wt.%, particularly preferably between 0.1 and 2.5 wt.%, based on the total composition, of photoinitiator P.

[0086] Expandable material E

[0087] In a preferred embodiment, the thermally expandable material E of the curable composition HZ according to the invention comprises a physical and / or chemical blowing agent.

[0088] The thermally expandable material E therefore undergoes a volume expansion when heat is supplied.

[0089] Chemical propellants include, in particular, nitrogen-generating substances such as isocyanate, azodicarbonamide, hydrazines, hydrazides, and other nitrogen-containing compounds, as well as sodium bicarbonate and titanium hydride. Under the influence of a chemical or thermal stimulus, gaseous products and other byproducts are formed through a chemical reaction of the propellant. This chemical reaction produces low molecular weight compounds that act as propellants. Once formed, these low-molecular-weight compounds never revert to the original propellant; the reaction is irreversible.

[0090] Physical propellants, on the other hand, increase their volume through a phase transition from solid or liquid to gaseous, without a chemical reaction with another substance. Volume expansion also occurs in the gaseous state under the influence of heat. Commonly used physical propellants include carbon dioxide, nitrogen, nitrous oxide, and also hydrocarbons, which are often encapsulated from the rest of the composition, for example, by being enclosed in a hollow sphere.

[0091] Preferably, the thermally expandable material has a coefficient of thermal expansion of more than 500%, preferably more than 1000%, and particularly preferably more than 5000%, at a specific expansion temperature.

[0092] Preferably, the curable composition HZ according to the invention contains between 5 and 25 wt.%, particularly preferably between 5 and 20 wt.%, most preferably between 8 and 16 wt.%, based on the total composition, of thermally expandable material E.

[0093] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the thermally expandable material E consists of microhollow spheres.

[0094] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the thermally expandable material E consists of microhollow spheres in which a thermoplastic shell encloses a gaseous or liquid organic compound. The gaseous or liquid organic compound can be any gas commonly used for thermally expandable microhollow spheres. Preferably, the gas is a saturated hydrocarbon or an ether. Suitable hydrocarbons are, in particular, butane, isobutane, propane, and pentane. Suitable ethers are dimethyl ether, diethyl ether, or tetrahydrofuran (THF).

[0095] In another preferred embodiment, the microhollow spheres have a particle density of 20 to 40 kg / m3, preferably 25 to 35 kg / m3, measured according to ISO 1183-1.

[0096] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the thermally expandable material E consists of microhollow spheres, wherein the mean particle size distribution Dso in the unexpanded state is in the range of 10 to 80 µm, preferably from 20 to 60 µm, measured according to ISO 13320.

[0097] Particularly suitable as thermally expandable material E are commercially available hollow microspheres such as Expancel® (available from Nouryon), Matsumoto Microsphere® F and FN series (available from Matsumoto Yushi-Seiyaku) and UNICELL-MS (available from Tramaco).

[0098] Additive AD

[0099] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the curable composition additionally contains additives AD, in particular selected from adhesion promoters, synergists and wetting additives, rheology modifiers, fillers, plasticizers, pigments, stabilizers, carboxylic acids and solvents. Suitable adhesion promoters are organoalkoxysilanes, (meth)acrylosilanes, anhydridosilanes, carbamatosilanes, alkylsilanes or iminosilanes, or also phosphate acrylates.

[0100] Synergists are substances that enhance the effectiveness of photoinitiators in photochemical processes, particularly in radical chain polymerization. They improve the efficiency of the photoinitiators by increasing their reactivity or promoting radical formation. Suitable synergists include amines, thioesters, and iodine compounds. Particularly preferred synergists for the present invention are acrylated amines, such as those available, for example, as Miramer AS2010 from Miwon Specialty Chemical Co., Ltd.

[0101] Suitable wetting additives are modified polysiloxanes, in particular modified polydimethylsiloxanes. Particularly preferred wetting additives of the present invention are multi-acrylic modified polydimethylsiloxanes, such as those available, for example, as Byk-UV 3505 from BYK Additives & Instruments.

[0102] Preferably, the curable composition HZ according to the invention contains between 0 and 20 wt.%, particularly preferably between 5 and 20 wt.%, most preferably between 5 and 15 wt.%, based on the total composition, of additives AD.

[0103] In a preferred embodiment, the curable composition HZ according to the invention is characterized in that the composition, in each case referring to the entire composition

[0104] - Between 70 wt.% and 95 wt.% compound with (meth)acrylate end groups V;

[0105] - Between 0.1 wt.% and 5 wt.% photoinitiator P;

[0106] - Between 5 wt.% and 25 wt.% thermally expandable material E;

[0107] - Contains between 0 wt.% and 20 wt.% additives AD; and may also contain other ingredients, the sum of which is 100 wt.%.

[0108] The curable composition HZ according to the invention is preferably formulated and mixed at room temperature. The compound with (meth)acrylate end groups V, photoinitiator P, and the optional additives AD is mixed in conventional mixing equipment (speed mixers or batch mixers) for 1 to 15 minutes. Once a homogeneous mass has been obtained, the thermally expandable material E is added and mixing continues until a homogeneous, lump-free mass is obtained. The curable composition HZ is either applied directly or stored in a suitable container, protected from light and air.

[0109] The curable composition HZ according to the invention is preferably formulated to have a liquid to pasty consistency at room temperature, flowable under normal dispensing pressure, with shear-thinning properties. Such a composition can be applied from commercially available cartridges, drums, or pails using a suitable device, for example, a melamine sponge or a doctor blade (spiral or wire). The composition can also be sprayed or printed (inkjet, piezo).

[0110] Cured curable composition AZ

[0111] Another object of the invention is an adhesive composite comprising

[0112] (a) a substrate S;

[0113] (b) a cured curable composition AZ according to the invention, which is applied to the substrate S from (a);

[0114] (c) a cured adhesive composition K applied to the cured curable composition AZ from (b), characterized in that the cured curable

[0115] Composition AZ consisting of a hardenable composition HZ containing

[0116] - at least one compound with (meth)acrylate end groups V;

[0117] - at least one photoinitiator P;

[0118] - at least one thermally expandable material E;

[0119] - optional additive A. was obtained.

[0120] The cured curable composition AZ according to the invention from (b) corresponds to the curable composition HZ after its curing and comprises all the above-mentioned preferred embodiments of the curable composition HZ. However, urethane acrylates as compounds with (meth)acrylate end groups V are also preferred for the cured curable composition AZ.

[0121] In one embodiment, the cured, hardenable composition AZ according to the invention is characterized in that the compound with (meth)acrylate has end groups V in the hardenable composition HZ urethane groups.

[0122] Compounds with (meth)acrylate end groups V, which have urethane groups, are often also referred to as urethane acrylates.

[0123] Compounds with (meth)acrylate end groups V, which have urethane groups, can be obtained from the reaction of an isocyanate group-containing polyetherurethane prepolymer with a hydroxy group-containing (meth)acrylate monomer.

[0124] Compounds with (meth)acrylate end groups V, which have urethane groups, are preferably free of isocyanate groups and in particular have exclusively vinyl end groups. This can be achieved by using a stoichiometric ratio of 1.0 to 1.6 mol of hydroxy-group-containing (meth)acrylate per mol equivalent of isocyanate groups of the isocyanate-containing polymer during the preparation.

[0125] This isocyanate group-containing polyetherurethane prepolymer can be obtained from the reaction of at least one monomeric diisocyanate with at least one polyether polyol and / or polyester polyol.

[0126] Suitable monomeric diisocyanates include commercially available aliphatic diisocyanates, in particular 1,5-pentamethylene diisocyanate (PDI), 1,6-hexane diisocyanate (HDI), 2,2(4),4-trimethyl-1,6-hexamethylene diisocyanate (TMDI), toluene diisocyanate (TDI), cyclohexane-1,3- or -1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI), perhydro-2,4'- or -4,4'-diphenylmethane diisocyanate (HMDI), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane, m- or p-xylylene diisocyanate (XDI), m-tetramethylxylylene diisocyanate (TMXDI), or mixtures thereof.

[0127] Suitable polyether polyols are polyoxyalkylene diols and / or polyoxyalkylene triols, in particular polymerization products of ethylene oxide or 1,2-propylene oxide or 1,2- or 2,3-butylene oxide or oxetane or tetrahydrofuran or mixtures thereof, wherein these may be polymerized with the aid of a starter molecule with two or more active hydrogen atoms, in particular a starter molecule such as water, ammonia or a compound with several OH or NH groups such as 1,2-ethanediol, 1,2- or 1,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols, nonanediols, decanediols, undecanediols, 1,3- or 1,4- Cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol or aniline, or mixtures of the aforementioned compounds.Particularly preferred are polyoxypropylene diols, polyoxypropylene triols, or ethylene oxide-terminated polyoxypropylene diols or triols. These are polyoxy-ethylenepolyoxypropylene mixed polyols, which are obtained in particular by further alkoxylating polyoxypropylene diols or triols with ethylene oxide after completion of the polypropoxylation reaction, thereby ultimately exhibiting primary hydroxyl groups.

[0128] The hydroxy-containing (meth)acrylate required for the production of the urethane acrylate prepolymer is not particularly limited, as long as it has an acrylate group and a hydroxyl group. Particularly suitable hydroxy-containing (meth)acrylates are hydroxyethyl methacrylate (HEMA) and hydroxyethyl acrylate (HEA).

[0129] In a further embodiment, the curable composition according to the invention is characterized in that the compound with (meth)acrylate end groups V comprises an epoxy acrylate. Epoxy acrylates are formed by a chemical reaction between epoxy resins and acrylic acid or its derivatives. The combination of these two functional groups in a single molecule yields an epoxy acrylate. The epoxy group is frequently bonded to the backbone of the molecule, while the acrylate groups are generally found at the end of the molecular chain or as trailing groups.

[0130] The adhesive bond comprises a layered structure. Additional layers can be added to the bond at any time. For example, a cured adhesive composition K can be followed by another cured curable composition AZ, and this in turn by another substrate S. This process can be repeated as often as desired. The substrates S used do not have to be identical.

[0131] Apart from the layered structure, the spatial configuration of the adhesive bond is preferably adapted to the requirements of the respective adhesive bond. The layer thicknesses of the cured curable composition AZ according to the invention from (b) and the cured adhesive composition K from (c) are preferably adapted to the requirements of the respective adhesive bond.

[0132] Preferably, the layer thickness of the substrate S from (a) corresponds to all common sizes used as substrates in an adhesive composite. Films or very thin materials can also be used as substrate S.

[0133] Preferably the layer thickness of the cured curable composition AZ according to the invention from (b) is between 5 and 200 pm, preferably between 10 and 150 pm, particularly preferably between 20 and 100 pm thick.

[0134] Preferably the layer thickness of the cured adhesive composition K from (c) is between 100 and 3,000 pm, preferably between 250 and 1,000 pm, particularly preferably between 300 and 500 pm.

[0135] Preferably, the cured curable composition AZ from (b) forms a functional layer. This functional layer improves both the adhesion of the adhesive composition K from (c) to the substrate S from (a) and also allows the adhesive bond to be removed.

[0136] In a preferred embodiment, the adhesive bond according to the invention is characterized in that the adhesive composition K cures at room temperature by crosslinking.

[0137] In a preferred embodiment, the adhesive composite according to the invention is characterized in that the adhesive composition K comprises an epoxy resin-based adhesive, a polyurethane-based adhesive, a poly(meth)acrylate-based adhesive, an adhesive based on silane-terminated polymer (STP) or a silicone adhesive, preferably an epoxy resin-based adhesive.

[0138] Suitable epoxy resins are in particular aromatic epoxy resins, especially the glycidyl ethers of:

[0139] - Bisphenol A, Bisphenol F or Bisphenol A / F, where A stands for acetone and F for formaldehyde, which served as starting materials for the production of these bisphenols.

[0140] - In the case of bisphenol F, positional isomers may also be present, in particular derived from 2,4'- or 2,2'-hydroxyphenylmethane.

[0141] - Dihydroxybenzene derivatives such as resorcinol, hydroquinone or catechol;

[0142] - other bisphenols or polyphenols such as bis(4-hydroxy-3-methylphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane (bisphenol-C), bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-tert. butylphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane (bisphenol-B), 3,3-bis(4-hydroxyphenyl)pentane, 3,4-bis(4-hydroxyphenyl)hexane, 4,4-bis(4-hydroxyphenyl)heptane, 2,4-bis( 4-hydroxyphenyl)-2-methylbutane, 2, 4-bis(3, 5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1, 1 -bis( 4-hydroxyphenyl)cyclohexane (bisphenol-Z), 1, 1 -bis(4-hydroxyphenyl)- 3,3,5-trimethylcyclohexane (bisphenol-TMC), 1, 1 -bis( 4-hydroxyphenyl)-1-phenylethane, 1,4-bis[2-(4-hydroxyphenyl)-2-propyl]benzene(bisphenol-P), 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol

[0143] Other suitable epoxy resins are aliphatic or cycloaliphatic poly-epoxides, in particular

[0144] Glycidyl ethers of saturated or unsaturated, branched or unbranched, cyclic or open-chain di-, tri- or tetrafunctional C2 to C30 alcohols, in particular ethylene glycol, propylene glycol, butylene glycol, hexanediol, octanediol, polypropylene glycols, dimethylolcyclohexane, neopentyl glycol, dibromoneopentyl glycol, castor oil, trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol or glycerol, or alkoxylated glycerol or alkoxylated trimethylolpropane; a hydrogenated bisphenol A, F or A / F liquid resin, or the glycidylation products of hydrogenated bisphenol A, F or A / F; an N-glycidyl derivative of amides or heterocyclic nitrogenous bases, such as triglycidyl cyanurate or triglycidyl isocyanurate, or reaction products of epichlorohydrin with hydantoin.

[0145] Preferably, the epoxy resin is a liquid resin or a mixture containing two or more liquid epoxy resins. "Liquid epoxy resin" is defined as a technical-grade polyepoxide with a glass transition temperature below 25°C. Optionally, the resin component may also contain proportions of solid epoxy resin. The epoxy resin is, in particular, a liquid resin based on a bisphenol or novolac, especially with an average epoxy equivalent weight in the range of 156 to 210 g / eq.

[0146] Amines are preferably used as hardeners for epoxy resin.

[0147] Preferred are amines with aliphatic amino groups and at least three hydrogen amines, in particular N-benzyl-1,2-ethanediamine, N-benzyl-1,2-propanediamine, N-benzyl-1,3-bis(aminomethyl)benzene, N-(2-ethylhexyl)-1,3-bis(aminomethyl)benzene, 2,2-dimethyl-1,3-propanediamine, 1,3-pentanediamine (DAMP), 1,5-pentanediamine, 1,5-diamino-2-methylpentane (MPMD), 2-butyl-2-ethyl-1,5-pentanediamine (C11-neodiamine), 1,6-hexanediamine, 2,5-dimethyl-1,6-hexanediamine, 2,2(4),4-trimethyl-1,6-hexanediamine (TMD). 1,7-Heptanediamine, 1,8-Octanediamine, 1,9-Nonanediamine, 1,10-Decanediamine, 1,11-Undecanediamine, 1,12-Dodecanediamine, 1,2-, 1,3- or 1,4-Diaminocyclohexane, 1,3-Bis(aminomethyl)cyclohexane, 1,4-Bis(aminomethyl)cyclohexane, Bis(4-aminonocyclohexyl)methane, Bis(4-amino-3-methylcyclohexyl)methane, Bis(4-aminono-3-ethylcyclohexyl)methane, Bis(4-amino-3,5-dimethylcyclohexyl)methane, Bis(4-aminono-3-ethyl-5-methylcyclohexyl)methane, 1-Am ino-3-am inomethyl- 3,5,5-trimethylcyclohexan (IPDA), 2(4)-Methyl-1 ,3-diaminocyclohexan, 2,5(2,6)-Bis( aminomethyl)bicyclo[2.2.1 ]heptan (NBDA), 3( 4 ), 8(9)-Bis( am inomethyl)tricyclo[5.2.1 .0, 2 ’ 6]decane, 1,4-diamino-2,2,6-trimethylcyclohexane (TMCDA), 1,8-menthanediamine, 3,9-bis(3-aminopropyl)-2,4,8, 10-tetraoxaspiro[SS]undecane, 1,3-bis(aminomethyl)benzene (MXDA), 1,4-bis(aminomethyl)benzene, Bis(2-aminoethyl) ether, 3,6-dioxaoctane-1, 8-diam in, 4, 7-dioxadecane-1, 10-diam in, 4, 7-dioxadecane-2, 9-diamine, 4,9-dioxadodecane-1, 12-diamine, 5,8-dioxadodecane-3, 10-diamine, 4,7, 10-trioxatridecane-1, 13-diamine or higher oligomers of these diamines, bis(3-aminopropyl)polytetrahydrofurans or other polytetrahydrofurandiamines, polyoxyalkylenediamines or triamines, especially polyoxypropylenediamines or polyoxypropylenetriamines such as Jeffamine® D-230, Jeffamine® D-400 or Jeffamine® T-403 (all from Huntsman), furan-based amines such as N-furfuryl-1,2-ethanediamine, 2,5-bis(aminomethyl)furan, 2,5-bis(aminomethyl)tetrahydrofuran, bis(5-aminomethylfuran-2-yl)methane, bis(5-aminomethyltetrahydrofuran-2-yl)methane, 2,2-bis(5-aminomethylfuran-2-yl)propane or 2,2-B is(5-am inom ethyltetrahydrofuran-2-yl)propane, or diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), dipropylenetriamine (DPTA), N-(2-aminoethyl)-1,3-propanediamine (N3-amine), N,N'-bis(3- aminopropyl)ethylenediamine (N4-amine), N,N'-bis(3-aminopropyl)-1,4-diaminobutane, N5-(3-aminopropyl)-2-methyl-1,5-pentanediam in, N3-(3-aminopentyl)-1,3-pentanediam in, N5-(3-amino-1-ethyl-propyl)-2-methyl-1,5- pentanediamine, N,N'-Bis(3-amino-1-ethylpropyl)-2-methyl-1,5-pentanediam in, 3-(2-Aminoethyl)aminopropylam in, Bis(hexamethylene)triam in (BHMT), N-Aminoethylpiperazine, 3-Dimethylaminopropylamine (DMAPA), 3-(3-(Dimethylamino)propylamino)propylam in (DMAPAPA), amine-functional adducts of the aforementioned amines with epoxides, phenalkamines, which are reaction products of cardanol with aldehydes, especially formaldehyde,and polyamines or a mixture of two or more of these amines. In a preferred embodiment, the silicone adhesive is in particular a room-temperature vulcanizing silicone rubber (RTV), especially an RTV-1 or RTV-2 silicone adhesive.

[0148] In a preferred embodiment, the adhesive bond according to the invention is characterized in that the substrate S comprises glass, metals, plastics and / or other materials.

[0149] Suitable substrates S, onto which the curable composition according to the invention can be applied and which can be bonded in an adhesive composite, are in particular

[0150] - Glass, glass-ceramic or glass coated with screen-printed ceramic or polycarbonate;

[0151] - Metals or alloys such as aluminium, copper, iron, steel, non-ferrous metals, including surface-treated metals or alloys such as galvanised or chromium-plated metals;

[0152] - coated or painted substrates, in particular cathodically dip-coated (KTL) or powder-coated metals or alloys or painted sheets;

[0153] - Paints or varnishes, especially automotive topcoats;

[0154] - cured adhesives, in particular based on polyurethane, silane-modified polymer or polysulfide, especially aged adhesives (residual adhesive bead), or body flange which has residual adhesive bead throughout or in places;

[0155] - Plastics such as rigid or flexible PVC, polycarbonate, polystyrene, polyester, polyamide, PMMA, ABS, SAN, epoxy resins, phenolic resins, PUR, POM, TPO, PE, PP, EPM or EPDM, either untreated or surface-treated, for example by plasma, corona or flames;

[0156] - Fiber-reinforced plastics, such as carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GFRP) and sheet moulding compounds (SMC);

[0157] - Repair or leveling compounds based on PCC (polymer-modified cement mortar) or ECC (epoxy resin-modified cement mortar); - Insulating foams, in particular made of EPS, XPS, PUR, PIR, rock wool, glass wool or foamed glass (Foamglas);

[0158] - Concrete, mortar, cement screed, fiber cement, in particular fiber cement boards, brick, tile, gypsum, in particular gypsum boards or anhydrite screed, or natural stones such as granite or marble, varnished tiles or painted concrete, asphalt or bitumen.

[0159] - Leather, textiles, paper, wood, wood-based materials bonded with resins such as phenolic, melamine or epoxy resins, resin-textile composites or other so-called polymer composites.

[0160] The substrates can be pretreated before application if necessary, in particular by physical and / or chemical cleaning processes.

[0161] Detachment of the adhesive bond

[0162] A further aspect of the invention is a method for separating the adhesive bond according to the invention, comprising the following steps: i) Heating the adhesive bond to at least the expansion temperature of the thermally expandable material E for at least 5 seconds, preferably for at least 30 seconds, particularly preferably for 1 minute, whereby an expansion temperature of at least 80°C, preferably at least 100°C, particularly preferably at least 120°C is reached; ii) Separating the cured composition from the substrate S, directly after step i) or after cooling the adhesive bond to room temperature, preferably directly after step i); iii) Optionally reusing the substrate S.

[0163] The adhesive bond can be heated by conductive heat transfer. Preferably, conductive heat transfer is achieved using a heating element or heating jacket placed at the point where the adhesive bond is to be separated. Another preferred method for heating the adhesive bond is convective heat transfer, for example, using a radiant heater or heat gun. Inductive heating of the adhesive bond is particularly preferred, especially in the case of a metallic substrate S.

[0164] Another preferred method for heating the adhesive bond is using electromagnetic radiation, for example, an infrared lamp.

[0165] Examples

[0166] The following are exemplary embodiments intended to further illustrate the described invention. Of course, the invention is not limited to these described embodiments.

[0167] A temperature of 23±1 °C and a relative humidity of 50±5% are referred to as "standard climate" (NC).

[0168] Production of a hardenable composition HZ

[0169] The hardenable compositions HZ of the comparative examples Z1 (Ref.) and the compositions according to the invention Z2 to Z6 were provided with the chemicals from Table 1 and in the weight percent, based on the respective composition, from Table 2.

[0170] First, the compounds with (meth)acrylate end groups V, the photoinitiator P, and additional additives AD were mixed for 1 minute in a speed mixer at 3500 rpm. Then, the thermally expandable material E was added and mixed further until a homogeneous, lump-free mass was obtained. The curable composition Z was then applied directly.

[0171] The composition in the comparative example Z1 (Ref.) is not in accordance with the invention, since this composition does not contain any thermally expandable material E.

[0172] Adhesive bonding

[0173] Adhesive composites according to the invention were produced using the curable compositions Z1 (Ref.), Z2, Z3, Z4, Z5, and Z6. A further comparative example, Z0 (Ref.), was also produced. However, no curable composition according to the invention was used in Z0 (Ref.); the adhesive composite Z0 (Ref.) therefore consists only of substrate S and an adhesive composition K. In all examples Z0 (Ref.), Z1 (Ref.), Z2, Z3, Z4, Z5, and Z6, two hot-dip galvanized steel sheets with dimensions of 100 x 25 x 1.2 mm, available, for example, from Rocholl, were used as substrate S.

[0174] For example ZO (Ref.), two of the above-mentioned untreated steel sheets were bonded with approximately 300 pm of a commercially available adhesive composition K. SikaPower®-1277 (available from Sika) was used.

[0175] In examples Z1 (Ref.) and Z2, a two-component epoxy resin adhesive with amines as the hardener component was used as adhesive composition K (SikaPower®-477 R).

[0176] For examples Z3, Z4, Z5, and Z6, a two-component epoxy resin adhesive with amines as the hardener component was used as adhesive composition K (SikaPower®-1277).

[0177] For examples Z1 (Ref.) and Z2, approximately 20 µm of the curable composition Z1 (Ref.) and Z2, respectively, was first applied to the aforementioned steel sheets. After a waiting period of 5 minutes, the curable composition was irradiated with an LED-UV lamp (LED-UV HANDcure from IST METZ GmbH & Co. KG) using light in the wavelength range of 315 to 415 nm for approximately 5 seconds. The two steel sheets with the cured curable composition were then bonded together with 300 µm of adhesive composition (SikaPower®-477 R).

[0178] For examples Z3, Z4, Z5, and Z6, approximately 100 µm of the curable composition Z3 to Z6 was first applied to two of the aforementioned steel sheets. After a waiting period of 5 minutes, the curable composition was irradiated with an LED-UV lamp (LED-UV HANDcure from IST METZ GmbH & Co. KG) using light in the wavelength range of 315 to 415 nm for approximately 5 seconds. The two steel sheets with the cured curable composition were then bonded together with 300 µm of adhesive composition (SikaPower®-1277).

[0179] Test methods: The tensile shear strength of the adhesive composites produced from Z0 (Ref.), Z1 (Ref.), Z2, Z3, Z4, Z5, and Z6 was tested under standard climate conditions.

[0180] The adhesive composites produced from ZO (Ref.), Z1 (Ref.), Z2, Z3, Z4, Z5, and Z6 were also subjected to the inventive method for separating the adhesive composite. The adhesive composite was heated to 120°C and 130°C, respectively, for one minute using two heating blocks, each attached to one side of the test setup and in direct contact with the adhesive composite. The tensile shear strength of the heated adhesive composite was then tested.

[0181] To determine the tensile shear strength, the manufactured adhesive joints were tested according to DIN EN-1465 at a tensile speed of 10 mm / min.

[0182] chemicals

[0183] Table 1: Chemicals used. Compositions

[0184] The compositions Z2 to Z6 are according to the invention.

[0185] Compounds marked with “(Ref.)” are comparative examples.

[0186] Z1 (Ref.) does not contain any thermally expandable material E.

[0187] Table 2: Compositions (in wt.%).

[0188]

[0189] Table 3 shows that the adhesive bond in embodiments and compositions Z2, Z3, Z4, Z5, and Z6 exhibits a tensile shear strength of more than 4 MPa under standard climate conditions (SCC). This fulfills the requirements for an adhesive bond suitable for use, particularly in the automotive sector.

[0190] The inventive composition Z2, in particular after heating the adhesive bond to 120°C, surprisingly exhibits a very low tensile shear strength of 0.24 MPa and is therefore particularly well suited for the inventive removal of the adhesive bond after heating at this temperature. The inventive compositions Z4 and Z6, after heating the adhesive bond to 130°C, surprisingly exhibit very low tensile shear strengths of 0.07 and 0.08 MPa, respectively, and are therefore particularly well suited for the inventive removal of the adhesive bond after heating at this temperature.

[0191] The urethane-containing curable compositions Z of the comparative tests Z3 and Z5 show a lower tensile shear strength in both temperature ranges and are therefore less suitable for a debonding on demand application.

[0192] In the comparative example Z0 (Ref.), which does not contain any curable composition Z according to the invention, and in the comparative example Z1 (Ref.), which does not contain any thermally expandable material E, the tensile shear strength after heating the adhesive bond to 120°C and 130°C respectively is above 3 MPa, which does not meet the requirements of a "debonding on demand" application. Consequently, this adhesive bond cannot be detached using the inventive method.

Claims

Patent claims 1. Hardenable composition containing HZ - at least one compound with (meth)acrylate end groups V, - at least one photoinitiator P; - at least one thermally expandable material E; - optional additive AD.

2. Curable composition HZ according to claim 1, characterized in that the at least one compound with (meth)acrylate Engruppen V does not comprise urethane acrylates.

3. Curable composition HZ according to one of claims 1 to 2, characterized in that the at least one compound with (meth)acrylate comprises end groups V of formula (II) q where R 1 represents a water atom or a methyl group, preferably a hydrogen atom; Y represents a linear or branched hydrocarbon residue with 2 to 20 carbon atoms, optionally containing heteroatoms, preferably oxygen; q represents a value of 1 to 2.

4. Curable composition HZ according to one of claims 1 to 2, characterized in that the at least one compound with (meth)acrylate comprises end groups V of formula (III) where R 1 represents a water atom or a methyl group, preferably a hydrogen atom; X represents a linear or branched hydrocarbon residue with 2 to 10 carbon atoms, optionally containing heteroatoms, preferably oxygen. Curable composition HZ according to one of claims 1 to 2, characterized in that the at least one compound with (meth)acrylate end groups V comprises at least one of formulas (IV), (V) and / or (VI). where a, b and c represent values ​​from 1 to 20, preferably 1 to 10, particularly preferably 1 to 5.

6. Curable composition HZ according to one of claims 1 to 5, characterized in that the curable composition is curable by UV-Vis radiation, in particular in the range of wavelengths from 315 to 415 nm.

7. Curable composition HZ according to one of claims 1 to 6, characterized in that the compound with (meth)acrylate end groups V comprises monomers with (meth)acrylate end groups, preferably monofunctional, multifunctional, in particular difunctional and / or trifunctional (meth)acrylate monomers, particularly preferably a mixture of difunctional and trifunctional (meth)acrylate monomers.

8. Curable composition according to any one of claims 1 to 7, characterized in that the compound with (meth)acrylate end groups V comprises a prepolymer with polyether and / or polyester and / or β-hydroxy ether repeating units.

9. Curable composition HZ according to one of claims 1 to 8, characterized in that the photoinitiator P comprises at least one type 1 and / or one type 2 photoinitiator, preferably a mixture of type 1 and type 2 photoinitiators.

10. Curable composition HZ according to one of claims 1 to 7, characterized in that the thermally expandable material E comprises a physical and / or chemical blowing agent.

11. Curable composition HZ according to one of claims 1 to 8, characterized in that the thermally expandable material E consists of microhollow spheres.

12. Curable composition HZ according to one of claims 1 to 9, characterized in that the thermally expandable material E consists of microhollow spheres in which a thermoplastic shell encloses a gaseous or liquid organic compound.

13. Curable composition HZ according to one of claims 1 to 10, characterized in that the thermally expandable material E consists of microhollow spheres, wherein the mean particle size distribution Dso in the unexpanded state is in the range of 10 to 80 µm, preferably from 20 to 60 µm, measured according to ISO 13320.

14. Curable composition HZ according to one of claims 1 to 11, characterized in that the curable composition additionally contains additives AD, selected from adhesion promoters, synergists, wetting additives, rheology modifiers, fillers, plasticizers, pigments, stabilizers, carboxylic acids and solvents.

15. Curable composition HZ according to one of claims 1 to 12, characterized in that the composition, in each case referring to the total composition - Between 70 wt.% and 95 wt.% compound with (meth)acrylate end groups V; - Between 0.1 wt.% and 5 wt.% photoinitiator P; - Between 5 wt.% and 25 wt.% thermally expandable material E; - Between 0 wt.% and 20 wt.% additives AD; and may contain other ingredients, the sum of which is 100% by weight.

16. Adhesive bond, comprehensive (a) a substrate S; (b) a cured curable composition AZ applied to the substrate S from (a); (c) a cured adhesive composition K applied to the cured curable composition AZ from (b), characterized in that the cured curable composition AZ comprises a curable composition HZ. - at least one compound with (meth)acrylate end groups V; - at least one photoinitiator P; - at least one thermally expandable material E; - optional additive A. was obtained.

17. Adhesive bond according to claim 16, characterized in that the adhesive composition K cures at room temperature by crosslinking.

18. Adhesive composite according to one of claims 16 to 17, characterized in that the adhesive composition K comprises an epoxy resin-based adhesive, a polyurethane-based adhesive, a poly(meth)acrylate-based adhesive, an adhesive based on silane-terminated polymer (STP) and / or a silicone adhesive, preferably an epoxy resin-based adhesive.

19. Adhesive composite according to one of claims 16 to 18, characterized in that the substrate S comprises glass, metals, plastics and / or other materials.

20. Method for removing the adhesive bond according to one of the Claims 16 to 19, comprising the following steps: i) Heating the adhesive composite to at least the expansion temperature of the thermally expandable material E for at least 5 seconds, preferably for at least 30 seconds, particularly preferably for 1 minute, whereby an expansion temperature of at least 80°C, preferably at least 100°C, particularly preferably at least 120°C is reached; ii) Separating the cured composition from the substrate S, directly after step i) or after cooling the adhesive composite to room temperature, preferably directly after step i); iii) Optionally reusing the substrate S.

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