Compressible pressure-sensitive structural adhesive films based on latent reactive compositions

Abstract

The invention relates to a pressure-sensitive structural adhesive film based on an epoxy resin composition, wherein the epoxy resin composition contains a latently reactive, heat-activatable curing agent to produce a structural composite structure after thermal curing and additionally contains a curing agent which crosslinks at room temperature, wherein the uncured adhesive film is compressible and thus allows tolerance compensation.

Description

Technical Field

[0001] The present invention relates to a compressible, pressure-sensitive, structural adhesive film based on a latently reactive composition, which is activated and crosslinked by means of heat and is self-adhesive at room temperature in the uncured state. Background Art

[0002] The terms used in the following embodiments should be understood as follows:

[0003] A "latently reactive adhesive film" is understood to be an adhesive film in which curing occurs by supplying heat. The curing agent is present in the adhesive film, but only reacts after the temperature has increased or a certain temperature has been reached.

[0004] In the following, "adhesive film" or "adhesive film" refers to any type of flat adhesive system, i.e. not only adhesive films but also adhesive tapes, adhesive films, adhesive strips, adhesive sheets or adhesive stampings. Furthermore, the terms "adhesive tape" or "adhesive film" also include so-called "transfer films", i.e., adhesive tapes without a carrier.

[0005] "Self-adhesive", "pressure-sensitive" or "pressure-sensitive" adhesives are adhesives or adhesive films which are able to connect two objects to be joined to one another simply by applying pressure. In particular, a permanent connection to the objects to be joined can be achieved with relatively weak pressing forces. The connection is reversible, that is, it can be released again without damaging the objects to be joined.

[0006] In the following, “compressible” refers to an adhesive film or adhesive film which is able to undergo a compressive deformation before the final thermal crosslinking and to regain its original thickness after the stress is removed.

[0007] A “structural or semistructural” adhesive bond is understood to mean a bond with a bond strength > 2 MPa on common substrates (eg aluminum, steel, GFRP, CFRP).

[0008] "Room temperature" is understood to be a temperature of 23±2°C.

[0009] Most epoxy resin adhesives based on liquid adhesives are used for structural and semi-structural bonding of components (e.g. in automotive bodies in white). These epoxy resin adhesives are applied via complex controlled dynamic or static metering facilities. Liquid adhesives have the disadvantage that they do not have an initial strength (also called initial bond strength), so that the components to be joined must be mechanically held in place during curing. This can be achieved, for example, by welding points or clamps.

[0010] According to the prior art, pressure-sensitive adhesive tapes hold the components in place immediately after joining, thereby overcoming the above-mentioned disadvantages of liquid adhesives. The pressure-sensitive adhesive tapes are reversible, that is to say, multiple repositioning is still possible. Subsequently, the specific form of these tapes can be subjected to a curing process, during which the tapes establish their final properties in terms of strength and durability. Curing begins via UV light, increased temperature or moisture. Curing is irreversible, so that subsequent repositioning is no longer possible.

[0011] WO 2015 / 011686 A1 describes an adhesive tape that can be used on oiled surfaces. However, this thermally crosslinked system does not have self-adhesive properties at room temperature, so that the component must be mechanically fixed until the adhesive film has completely cured.

[0012] Furthermore, pressure-sensitive adhesive films based on epoxy resins are prior art, for example in the bonding of temples to windshields, as shown in US Pat. No. 5,587,236 A. However, this system is not suitable for bonding on oiled surfaces.

[0013] It is also known that systems with thermoplastic film formers are described, for example in WO 2017 / 109011 A1, for producing adhesive tapes based on epoxy resins that are pressure-sensitive at room temperature. A disadvantage of this type of adhesive film is the limitation of the layer thickness caused by production.

[0014] Additionally, in the hitherto unpublished patent application PCT / EP2018 / 057550, an epoxy resin-based adhesive bonding film is described which is suitable for bonding oiled surfaces and can be present in thicknesses of 1 μm and 3000 μm at the same time.

[0015] In none of the adhesive films mentioned, tolerance compensation of the joining partners to be joined is possible to the same extent as with liquid adhesives. However, since production-related tolerances are always present in real components, this property is of crucial importance.

[0016] WO 2014 / 071334 A1 describes an adhesive film based on epoxy resin, which contains core-shell rubber particles and heat-expandable microparticles, which expand during curing under the influence of the curing temperature. In this case, it is disadvantageous that before curing, due to the tolerances of the joining parts, the joining parts are not optimally wetted, and this only occurs during the curing when expanding. However, in this case, due to the gradual crosslinking, the establishment of adhesion to the joining partner is no longer guaranteed, so that a lack of adhesion to the second joining part often results. Summary of the invention

[0017] Based on the known prior art, the object of the present invention is to provide an improved self-adhesive adhesive film which is pressure-sensitive at room temperature, can be used on oiled surfaces, can be compressed in the uncured state to compensate for tolerances of the joined parts and, after curing, has a high strength (for example in a tensile shear test on steel greater than 10 MPa according to DIN EN 1465) and a high resistance to environmental influences.

[0018] A further object is to provide a self-adhesive adhesive film which can be produced without the use of film formers and solvents.

[0019] Accordingly, a pressure-sensitive structural adhesive film based on an epoxy resin composition is proposed, wherein the epoxy resin composition contains a latently reactive, heat-activatable curing agent to produce a structural composite structure after thermal curing. According to the invention, the epoxy resin composition additionally contains a curing agent that crosslinks at room temperature, wherein the uncured adhesive film is compressible and thus allows tolerance compensation.

[0020] By using at least one curing agent that crosslinks at room temperature, it is possible to produce prepolymers or, in this case, pressure-sensitive planar structures in the form of adhesive films independently of the layer thickness without the use of film formers etc. In addition, acrylates or hot melt adhesives can be omitted. In addition, the adhesive film has a thermal post-crosslinking potential.

[0021] Thus, the adhesive film can be produced by partially crosslinking the epoxy groups with the aid of a curing agent that crosslinks at room temperature. In particular, the production of the adhesive film and the viscosity increase and gelation of the polymer that occur with it are not carried out by drying or UV polymerization of the acrylate groups, but by pre-crosslinking of the epoxy resin and the resulting prepolymer formation. This partial reaction is carried out similarly to the crosslinking reaction of two-component liquid adhesives based on epoxy resins, but differs from this in that it is not terminated by adding a curing agent that crosslinks at room temperature in a substoichiometric manner. Therefore, there is still a reaction potential, which can be used in the final application to build up the composite strength after thermal curing.

[0022] By further using corresponding additives, compressible adhesive films are produced before the final thermal crosslinking, wherein the additives cause expansion during the production of the adhesive film due to partial crosslinking of the epoxy groups.

[0023] Thus, the produced adhesive film can be applied to components with production-related tolerances before curing and compensate for these tolerances by means of a foam-like compressibility. For this reason, comprehensive wetting of the actual component can be ensured before curing.

[0024] In a preferred embodiment, the epoxy resin composition comprises 30% to 95% by weight of at least one epoxide component; 0.1% to 80% by weight of at least one heat-activatable curing agent; 0.1% to 90% by weight of at least one curing agent that crosslinks at room temperature; 0% to 70% by weight of at least one accelerator; 0.1% to 70% by weight of at least one additive responsible for the expansion of the prepolymer; 0% to 70% by weight of at least one additive, wherein the weight percentages of the components add up to 100%.

[0025] In another preferred embodiment, the curing agent crosslinking at room temperature comprises at least one amine, amide and / or thiol. For example, primary or secondary amines, aliphatic amines, aromatic amines, polyamides, amidoamines, polyether diamines, polythiols or mixtures thereof can be used. Depending on the curing agent crosslinking at room temperature used, other properties of the adhesive film, such as its tensile strength, can also be influenced.

[0026] Curing agents based on amines, amides and / or thiols make it possible to provide a flexible and, in the uncured state, pressure-sensitive planar structure which is easy to handle and which, due to its pressure sensitivity, prevents slipping of the components after bonding until final curing.

[0027] In a further preferred application, the additive responsible for the expansion has an activation temperature between 30° C. and 150° C. and a maximum expansion between 40° C. and 150° C., particularly preferably between 60° C. and 130° C.

[0028] In a further preferred embodiment, the uncured adhesive film has a compression of between 5% and 80%, depending on the filler concentration and the expansion.

[0029] In a further preferred embodiment, the adhesive film has an additional expansion during curing.

[0030] In a preferred embodiment, the pressure-sensitive adhesive film has an adhesion of at least 0.2 N / mm in the uncured state. In this case, the adhesion to steel is determined according to DIN EN 1939:1996 at 23° C.±2° C. and 50%±5% relative humidity, at a peeling speed of 300 mm / min and a peeling angle of 180°. In the test, an etched PET film with a thickness of 50 μm was used as a reinforcing film. The 25 mm wide measuring strip was bonded to the steel substrate with the aid of a 5 kg roller at a temperature of 23° C.±2° C. The adhesive film was peeled off at 300 mm / min 10 minutes after application. The measured value (in N / mm) is generated as the average value of five individual measurements.

[0031] Pressure-sensitive adhesives act permanently pressure-sensitively at room temperature, i.e. have sufficiently low viscosity and high initial tack so that they can wet the surface of the corresponding adhesive substrate even with low pressing force. The adhesive's bondability is based on its adhesive properties, while its removability is based on its cohesive properties.

[0032] In another preferred embodiment, the compressible pressure-sensitive structural adhesive film has at least one carrier. If a carrier material is present, the carrier material can be provided on one side or preferably on both sides with a (pressure-sensitive) adhesive, which contains or consists of a compressible composition without solvent and film former. The carrier material includes all planar structures, such as films, foams, knitted fabrics, scrims, nonwovens and paper or combinations thereof. Different carriers can be combined with adhesives for different applications.

[0033] In a further preferred development, the compressible, pressure-sensitive, structural adhesive film is carrier-free and is therefore suitable for forming a transfer film.

[0034] In the case of transfer films or transfer tapes, the adhesive corresponding to the finished adhesive film in the final state is applied before application on a flexible release paper (liner) or between two flexible release papers. The release paper is provided with a release layer and / or has anti-adhesive properties.

[0035] When two release papers are used, in order to apply the adhesive film, one release paper is first removed and the adhesive film is applied with the now exposed adhesive surface to the first joining component. The second release paper is then removed and the now exposed adhesive surface is connected to the second joining component. The adhesive can thus be used directly to connect two surfaces.

[0036] This pressure-sensitive, carrier-free transfer adhesive film enables very precise bonding with regard to positioning and metering.

[0037] Adhesive films or adhesive tapes are also possible in which the adhesive is not operated via two release papers, but only via a single double-sided repellent release paper. In this case, the first side of the adhesive film is covered with one side of the double-sided separated release paper, while the second side of the adhesive film is subsequently covered with the back side of the double-sided separated release paper when it is wound onto a roll or reel.

[0038] In a preferred development, the thickness of the latently reactive adhesive in the form of a transfer adhesive film and applied to the planar structure is between 1 μm and 3000 μm, more preferably between 10 μm and 2000 μm and particularly preferably between 50 μm and 1000 μm.

[0039] Layer thicknesses between 300 μm and 1000 μm are most suitable for compensating for tolerances in the components to be bonded and are therefore often used, for example, in automotive body shells. In combination with the compressible properties of the adhesive film, tolerances caused by production can be compensated and compensated even better.

[0040] Layer thicknesses between 1 μm and 50 μm reduce the adhesion to the joining components, but at the same time reduce the material usage.

[0041] Epoxide component

[0042] The latent reactive composition comprises at least one epoxide component A. In principle, any epoxy resin or any epoxide-containing material known to those skilled in the art for use in adhesives and adhesive tapes can be used as the epoxide component. In this case, the epoxide component is an arbitrary organic compound having at least one oxirane ring, which can be polymerized by a ring-opening reaction. This material includes monomeric epoxides and polymeric epoxides, and can exist in aliphatic, alicyclic and aromatic modes. The material referred to as epoxide usually has at least two epoxy groups per molecule on average, preferably more than two epoxy groups per molecule. What is decisive for the later stoichiometric crosslinking of epoxy groups with corresponding crosslinking agents is the epoxide equivalent (EEW, Epoxy-Equivalent-Weight). EEW represents the mass of an epoxy resin with equivalent [Eq] epoxy functional groups in units of [g]. This is calculated according to the following formula:

[0043]

[0044] Among them, M Epoxy As the molar mass of epoxy resin, f Epoxy As the functionality of epoxy resin.

[0045] Polymer epoxides include linear polymers with terminal epoxy groups, polymers with backbone oxygen stray units and polymers with pendant epoxy groups. Useful epoxides of this type are described in detail in US Pat. No. 3,117,099 A.

[0046] Other epoxide-containing materials include glycidyl ether monomers. These materials are described in US 3,018,262A.

[0047] A variety of commercially available epoxide-containing materials and epoxy resins can be used. Readily available epoxides are classified as particularly suitable, such as octadecane oxide, epichlorohydrin, styrene oxide, vinyl cyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ethers of bisphenol A (e.g., those sold under the trade names EPON 828, EPON 1004, and EPON 1001F by Shell Chemical Co., and DER-332 and DER-334 available from Dow Chemical Co.), diglycidyl ethers of bisphenol F (e.g., ARALDITE GY281 from Ciba-Geigy), vinyl cyclohexene dioxide such as ERL 4206 from Union Carbide Corp., 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (e.g., DER-332 from Union Carbide Corp.), bisphenol A (e.g., DER-332 from Union Carbide Corp.), bisphenol B (e.g., DER-332 from Union Carbide Corp.), bisphenol A ... Corp.), 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-dioxane (e.g., ERL-4234 from Union Carbide Corp.), bis(3,4-epoxycyclohexyl) adipate (e.g., ERL-4299 from Union Carbide Corp.), dipentene dioxide (e.g., ERL-4269 from Union Carbide Corp.), epoxidized polybutadiene (e.g., OXIRON 2001 from FMC Corp.), epoxy-functional silicone-containing resins, epoxy silanes (e.g., β-(3,4-epoxycyclohexyl)ethyltrimethoxy)silane and γ-glycidoxypropyltrimethoxysilane, available from Union Carbide), flame retardant epoxy resins (e.g., available from Dow Chemical Co.), 1,4-butanediol diglycidyl ether (e.g., ARALDITE RD-2 from Ciba-Geigy), hydrogenated epoxy resins based on bisphenol A-epichlorohydrin (e.g., EPONEX 1510 from Shell Chemical Co.), and polyglycidyl ethers of novolacs (e.g., DEN-431 and DEN-438 from Dow Chemical Co.).

[0048] In another preferred embodiment, the pressure-sensitive structural adhesive film contains at least 10% by weight of an epoxy resin that is liquid at 25° C., based on the epoxy component A. The proportion of the liquid epoxy resin in the epoxy component A is in particular 10% to 100% by weight, more preferably 20% to 95% by weight. Liquid epoxy resins or mixtures of different resins can be used.

[0049] In a further preferred embodiment, the latently reactive composition comprises, relative to the epoxy equivalent of all epoxy resins or epoxide-containing materials used, 1% to 50% of a curing agent which crosslinks at room temperature.

[0050] Heat activated curing agent

[0051] Suitable heat-activatable curing agent B are all known curing agents for epoxy resin adhesives, for example dicyandiamide and acid anhydrides and mixtures thereof.

[0052] Room temperature cross-linking curing agent

[0053] As curing agents C which crosslink at room temperature, all known curing agents for epoxy resin adhesives are suitable, for example primary or secondary amines, aliphatic amines, aromatic amines, polyamides, amidoamines, polyether diamines, phenol alkane amines, phenol alkane amides, polythiols or mixtures thereof. A selection of crosslinking agents is listed, for example, in the specialist handbook “Formulierung von Kleb- und Dichtstoffen” by Bodo Müller and Walter Rath (Müller & Rath, 2009). Room temperature is defined as 23° C.±2° C.

[0054] Accelerator

[0055] All known accelerators for epoxy resin adhesives and epoxy resin-based adhesive tapes are suitable as accelerator D, for example imidazoles, urea derivatives (e.g. monuron, diuron, fenitrouron), tertiary amines or mixtures thereof. A selection of accelerators is listed, for example, in the specialist handbook “Formulierung von Kleb-und Dichtstoffen” by Bodo Müller and Walter Rath (Müller & Rath, 2009).

[0056] additive

[0057] All known additives for adhesive tapes and pressure-sensitive adhesives are suitable as additives E, for example adhesive resins, so-called tackifiers, polymers, rheology modifiers, foaming agents, expanders, fillers, adhesion promoters, polyols, anti-aging agents, light screens, UV stabilizers, dyes, impact modifiers, phenoxy resins or mixtures thereof. In addition, all additives listed in WO 2017 / 174303 A1 can be used.

[0058] Generally, the epoxy resin-based adhesive films described herein can be prepared according to the following three methods:

[0059] a) Epoxy resin, crosslinking agent, suitable film former and possible additives are dissolved in water or solvent. The mixture is then coated and the adhesive is dried to produce a web-shaped adhesive film.

[0060] b) Melting epoxy resin, crosslinking agent, suitable film former and possible additives and mixing the individual components. The heated mass is then coated and a web-shaped adhesive film is produced by cooling to room temperature.

[0061] c) Mixing epoxy resin, crosslinking agent and possible additives in acrylate monomers mixed with photoinitiator. The adhesive film is produced by coating and polymerization of acrylate. DETAILED DESCRIPTION

[0062] Preferred embodiments are described below.

[0063] Raw materials used:

[0064]

[0065]

[0066] Preparation of pressure-sensitive adhesive

[0067] To prepare the corresponding pressure-sensitive adhesive, the corresponding solid epoxy resin is dissolved in the previously added liquid epoxy resin at 23° C. with stirring. A heat-expandable filler is introduced into the homogenized material. Then, optionally, a modified epoxy resin and filler are added. Subsequently, a heat-activatable curing agent and optionally an accelerator are stirred into the resin material.

[0068] To produce the adhesive layer, that is to say the carrier-free (pressure-sensitive) adhesive tape, the different adhesives were mixed with different concentrations of a curing agent that crosslinks at room temperature and applied to a conventional release paper (siliconized polyester film) with the aid of a laboratory spreader and pre-crosslinked. The thickness of the transfer film after pre-crosslinking was 200±15 μm. The pre-crosslinking was carried out analogously to the drying of the solvent-based adhesive film, initially at room temperature for 10 minutes and subsequently at 90° C. for 10 minutes. The pre-crosslinked adhesive film was laminated on the open side immediately after the pre-crosslinking with a second release paper (siliconized paper with a lower release force than the first release paper).

[0069] The production of such transfer films is characterized by the fact that only some of the reactive groups of the epoxy resin used are crosslinked by a curing agent that crosslinks at room temperature, resulting in a so-called prepolymer that swells. This means that the adhesive film is compressible before curing, and only during the final bonding of the substrates and subsequent thermal curing do the other reactive groups crosslink and produce a structural and now no longer compressible bond.

[0070] Adhesive ingredients

[0071] The composition of the adhesive with regard to the selection of the expansion agent is summarized in the following table, wherein the amount indicated is expressed in parts by weight:

[0072]

[0073]

[0074] Adhesive results regarding adhesion, tensile shear strength and tensile strength

[0075] Adhesion:

[0076] The adhesion to steel was determined in accordance with DIN EN 1939:1996 at 23°C ±2°C and 50% ±5% relative humidity, at a peeling speed of 300 mm / min and a peeling angle of 180°. An etched PET film with a thickness of 50 μm was used as reinforcing film. Here, the 25 mm wide measuring strip was bonded to the steel substrate with the aid of a 5 kg roller at a temperature of 23°C ±2°C. The adhesive film was peeled off at 300 mm / min 10 minutes after application. The measured value (in N / mm) was generated as the average of five individual measurements (including standard deviation).

[0077] Tensile shear strength:

[0078] Tensile shear tests were carried out at 23°C ± 2°C and 50% ± 5% relative humidity at a test speed of 10 mm / min as a characteristic parameter for the bond strength to steel in accordance with DIN EN 1465. Steel of alloy 1.4301 was used as test substrate, which was cleaned with acetone on the one hand and subjected to mechanical surface preparation by means of cross grinding on the other hand. The samples were cured at 130°C for 30 minutes in each case. The results are expressed in MPa (N / mm 2 The average value of five measurements (including standard deviation and fracture image evaluation) is given.

[0079] tensile strength:

[0080] Tensile tests were carried out at 23°C ± 2°C and 50% ± 5% relative humidity at a test speed of 10 mm / min as a characteristic parameter for the strength of the pure adhesive film in the cured state according to DIN EN ISO 527. For this purpose, strips with a width of 15 mm and a length of 100 mm were cut from the cured adhesive film. In the results shown, the layer thickness was 0.2 mm. The samples were cured at 130°C for 30 minutes. The results are expressed in MPa (N / mm 2 The average of five measurements (including standard deviation) is given.

[0081] Expansion:

[0082] The expansion after pre-crosslinking is performed by measuring the layer thickness with the aid of a thickness measuring device. An unfilled pattern established with the same coating parameters is used as a reference. On the one hand, the measurement is performed immediately after the coating and the pre-crosslinking performed thereby (as described above in the context of the preparation of the pressure-sensitive adhesive). On the other hand, the expansion is measured again after curing at 140° C. for 30 minutes and subsequently cooling to 23° C. The expansion is derived according to the following formula:

[0083]

[0084] compression:

[0085] The compression is measured with the aid of a Keyence VHX-5000 microscope at a magnification of 20×100. For this purpose, the adhesive film is clamped between two metal substrates and the thickness of the film is measured in the unloaded state. The clamped adhesive film is then loaded with a force of 100 N and the thickness of the film is measured again. The compression is derived according to the following formula:

[0086]

[0087] The table below shows the results of adhesion measurements, tensile shear and tensile testing of the adhesive films and the associated expansion and compression.

[0088]

[0089]

[0090] Adhesive films K1, K3, K4 and R1 have similar compositions. Only the swelling filler has changed in order to illustrate the differences in the same selection. Adhesive film K2 corresponds largely to the adhesive composed of K1, only the epoxy resin component has been replaced and the curing agent crosslinking at room temperature has been replaced.

[0091] Adhesives K1 and K2 have identical mechanical behavior and identical expansion and compression within the range of the standard deviation.

[0092] Within the range of the standard deviation, the adhesive films with adhesives K1, K3 and K4 showed no significant differences in adhesion in the uncured state. The reference adhesive R1 without filler had a higher adhesion in the uncured state.

[0093] When measuring the tensile shear strength, no significant differences in the strength of the adhesives K1 to K4 were detected within the scope of the standard deviation. Only the unfilled reference R1 had a significantly higher tensile shear strength, which in turn was attributable to the fact that no swelling filler was used.

[0094] The tensile strength of the adhesive films does not show significant differences with respect to the swelling filler used. Only the unfilled reference R1 has a strength again approximately 5 times higher.

[0095] After 10 minutes of pre-crosslinking at 90° C., the expansion shows clear differences between the fillers used. Thus, adhesives K1 and K2 with the same expanding filler have an expansion of approximately 220%, while adhesive film K3 only has an expansion of approximately 190%. As with adhesive K4, the unfilled reference shows no expansion, which in the case of K4 is attributed to the expanding filler used.

[0096] The expansion measurements after curing at 140° C. for 30 minutes show a similar picture for adhesives K1 to K3 as the expansion measurements after pre-crosslinking at 90° C. After this curing, only adhesive film K4 shows an expansion of approximately 160%. Thus, adhesive film K4 is not compressible before curing, but it expands during curing.

[0097] Due to the limitations of the test method, it is not possible to measure compression precisely. This is largely related to filler concentration, bond film thickness and previous expansion.

[0098] Thus, for the adhesive films K1 to K3, a compression of about 30% was measured after pre-crosslinking for 10 minutes at 90° C. Due to the different types of intumescent fillers or the absence of intumescent fillers, the adhesives K4 and R1 are incompressible.

[0099] As far as applicable, all individual features shown in the exemplary embodiments can be combined with one another and / or exchanged without departing from the scope of the present invention.

Claims

1. A compressible pressure-sensitive structural adhesive film based on an epoxy resin composition, wherein the adhesive film is carrier-free to form a transfer film, or the adhesive film includes a carrier, characterized in that The epoxy resin composition comprises: a) 30% to 95% by weight of at least one epoxide component; b) 0.1% to 80% by weight of at least one latently reactive, heat-activatable curing agent to produce a structural composite structure after thermal curing; c) 0.1% to 90% by weight of at least one curing agent which crosslinks at 23±2° C., wherein the curing agent undergoes a crosslinking reaction of the curing agent for producing the adhesive film by partial crosslinking of epoxy groups; d) 0 to 70 wt. % of at least one accelerator; e) 0.1% to 70% by weight of at least one filler responsible for the expansion of the prepolymer, the filler responsible for the expansion of the prepolymer having an activation temperature between 30° C. and 150° C. and a maximum expansion degree between 40° C. and 150° C. and expanding during the production of the adhesive film by partial crosslinking of the epoxy groups, and f) 0% to 70% by weight of at least one additive, wherein the weight percentages of component a), component b), component c), component d), component e) and component f) add up to 100%.

2. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that Depending on the concentration of the filler responsible for the expansion of the prepolymer and the expansion, the uncured adhesive film has a compression of between 5% and 80%, wherein the compression is given by the following formula:

3. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that The adhesive film has additional expansion during curing.

4. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that In the uncured state, the adhesion is at least 0.2 N / mm in accordance with DIN EN 1939.

5. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that The thickness of the adhesive film is between 1 μm and 3000 μm.

6. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that The thickness of the adhesive film is between 10 μm and 2000 μm.

7. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that The thickness of the adhesive film is between 50 μm and 1000 μm.

8. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that At least one epoxide component comprises at least 10 wt. % of an epoxy resin that is liquid at 25°C.

9. The compressible pressure-sensitive structural adhesive film according to claim 1, characterized in that The at least one epoxide component comprises between 20% and 95% by weight of an epoxy resin that is liquid at 25°C.

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