adhesive

Description

[0001] The invention relates to the technical field of pressure-sensitive adhesives used in single- and double-sided adhesive tapes. More specifically, the invention relates to a pressure-sensitive adhesive based on a poly(meth)acrylate based on a specific monomer composition.

[0002] The invention is aimed, among other things, at the parameter "wetting," which is relevant to adhesive technology. In the following, this refers to the formation of an interface between a pressure-sensitive adhesive and the substrate to be bonded. The term "wetting" thus describes the ability of a pressure-sensitive adhesive to compensate for unevenness and to displace air between itself and the substrate. The greater the wetting, the better the interactions between the pressure-sensitive adhesive and the substrate can develop, and the better the adhesion and adhesion. It is frequently observed that, particularly on rough surfaces or surfaces that exhibit unevenness, curvature, or corrugation due to manufacturing, wetting once achieved weakens again under mechanical stress, i.e., dewetting occurs.

[0003] Wetting must be distinguished from the buildup of adhesive strength over time. Even with good initial wetting, adhesive strength can still increase over time, as more and more of the functional groups contained in the adhesive, which can interact with the surface, orient themselves toward it.

[0004] For various applications, such as the construction sector, the industrial production of technical products, or for assembly purposes, thick, yet highly adhesive adhesive tapes (so-called "assembly adhesive tapes") are increasingly required. Since bonding often takes place outdoors and the bonded products are exposed to external weathering, expectations for the properties of such adhesive tapes are often high. The bond should be strong, durable, and weather-resistant; high resistance to moisture, heat, and humid heat is often required. Furthermore, the adhesive tapes should wet quickly, compensate for unevenness in the bonding joint or on the substrates to be bonded, and exhibit high adhesive strengths (initial bond strengths) right from the start.When using non-foamed adhesive tapes, good wetting offers the additional advantage of enabling the bonding of transparent materials without optical defects, which is increasingly also desired for thick adhesive tapes (e.g. when bonding transparent materials such as glass or transparent plastics).

[0005] The adhesive tapes used for such purposes are usually equipped with adhesives whose technical properties must be very well coordinated. Cohesion, tack, flow behavior, and other properties must be precisely adjusted. Since the technical formulations of the pressure-sensitive adhesive that influence these properties often have opposing effects on the individual properties, coordination is usually difficult, or compromises must be accepted.

[0006] Especially for very thick adhesive tapes, it is often difficult to produce very homogeneous adhesive tapes. Due to processing reasons, very thick adhesive tapes are often not homogeneous throughout the entire layer. This is usually undesirable, as adhesive tapes are often required that have well-defined properties regardless of their layer thickness and manufacturing method.

[0007] Materials with viscoelastic properties suitable for pressure-sensitive adhesive applications are characterized by their ability to both flow viscously and develop elastic restoring forces upon mechanical deformation. The respective proportions of both processes are in a certain relationship to each other, depending on the precise composition, structure, and degree of cross-linking of the material in question, as well as the speed and duration of the deformation and the temperature.

[0008] The viscous flow component 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 inherent tack (also referred to as pressure-sensitive adhesion or tack) and thus often also to high adhesive strength. Highly cross-linked systems, crystalline, or glass-like polymers, are generally not inherently tacky due to the lack of flowable components.

[0009] The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transfer of forces acting on an adhesive bond. They ensure that an adhesive bond can sufficiently withstand continuous loading, for example, in the form of permanent shear stress, over an extended period of time.

[0010] In foamed, multilayer adhesive tapes, continuous stress can lead to uneven stress distribution. If the forces exceed the adhesion of the pressure-sensitive adhesive layer to the surface, this can result in partial detachment of the pressure-sensitive adhesive layer. The proportion of the wetted surface thus decreases.

[0011] To prevent the pressure-sensitive adhesives from flowing off the substrate and to ensure sufficient stability of the pressure-sensitive adhesive in the adhesive bond, sufficient cohesion of the pressure-sensitive adhesives is required. However, to achieve good adhesion properties, the pressure-sensitive adhesives must be able to flow onto the substrate, develop sufficient interactions with the surface in the boundary layer, and guarantee good and permanent wetting of the substrate surface. To avoid cracks within the bond line (within the pressure-sensitive adhesive layer), a certain degree of elasticity of the pressure-sensitive adhesive is also required.

[0012] To achieve sufficient cohesion, pressure-sensitive adhesives are usually crosslinked, meaning individual macromolecules are linked together through bridge bonds. Crosslinking can occur in various ways, including physical and chemical (thermal) crosslinking methods.

[0013] To produce homogeneous adhesive tapes, it is advantageous to thermally crosslink the polymers: It is easily possible to supply even thick layers with thermal energy evenly. In contrast, mass layers crosslinked by actinic radiation (e.g., ultraviolet radiation, electron beams) exhibit a crosslinking profile through the crosslinked layer. This crosslinking profile results from the fact that the rays only penetrate the layer to a limited depth, with the intensity of the radiation decreasing with the penetration depth due to absorption processes. Therefore, the outer regions of a radiation-chemically crosslinked mass layer are more strongly crosslinked than the regions further inside, with the crosslinking intensity decreasing overall towards the inside. This effect is particularly significant for thick layers.

[0014] EP 2 305 389 A2 and EP 2 617 789 A1 describe thermally crosslinked, foamed, and non-foamed assembly tapes with good adhesive and cohesive properties. However, these tapes exhibit comparatively poor wetting behavior and also exhibit weaknesses in bonding to non-polar substrates, particularly automotive paints.

[0015] WO 2013 / 048 985 A2 and WO 2013 / 048 945 A1 describe multilayer assembly tapes that are particularly suitable for bonding to nonpolar surfaces, especially automotive paints. The adhesive tapes of WO 2013 / 048 985 A2 are characterized in that the outer pressure-sensitive adhesive layer comprises (meth)acrylic acid esters with 2-alkylalkanol radicals having 12 to 32 carbon atoms, and optionally with C 1-12 -alkanol radicals. In WO 2013 / 048 945 A1, the outer pressure-sensitive adhesive layer comprises, in particular, acrylic acid esters with a primary alcohol radical having 14 to 25 carbon atoms and an iso index of at least 2 to a maximum of 4. In addition to the disadvantage that the products described there are cross-linked by UV radiation, it is evident that the initially good wetting decreases under load, thus leading to de-wetting.

[0016] WO 2014 / 081 623 A2 also describes UV-crosslinked, multilayer assembly tapes with very good bond strengths on automotive paints. This is achieved by using 2-propylheptyl acrylate (PHA) as a comonomer in the outer pressure-sensitive adhesive layer. Preferred comonomer compositions are mixtures of PHA and another comonomer with an ethylenically unsaturated group. The latter are, in particular, (meth)acrylates with branched, cyclic, or aromatic alcohol components, for example, with isobornyl acrylate (IBOA), an acrylic acid ester with a high glass transition temperature and a bicyclic radical.

[0017] US 2011 / 0244230 A1 describes an acrylate-based foam adhesive tape that is particularly conformable and well-suited for bonding to uneven substrates. However, the described adhesive tapes are crosslinked using UV radiation, so the resulting crosslinking gradient leads to poor wetting behavior.

[0018] EP 2 226 372 A1 describes a thermally crosslinked pressure-sensitive adhesive comprising a polyacrylate with an acrylic acid concentration of 8 to 15 wt.% and characterized in that the ratio of linear to branched acrylic acid esters is in the range of 1:6 to 10:1 by mass. However, the composition exhibits too slow wetting and too slow a rise in adhesive strength to the respective maximum adhesive strength on the substrates.

[0019] DE 20 2010 001 353 U1 relates to an adhesive article which is produced with a synthetic polymer as a binder and is characterized in that the polymer is composed of propylheptyl acrylate or of propylheptyl acrylate and other monomers copolymerized therewith.

[0020] EP 3 178 856 A1 describes a melt-processable, thermally crosslinkable polyacrylate-based composition which a) at least one crosslinkable poly(meth)acrylate; b) at least one organosilane having a substituent with a cyclic ether function; and c) at least one substance accelerating the reaction of the crosslinkable poly(meth)acrylate with the cyclic ether function contains.

[0021] The object of the invention is to offer high-performance pressure-sensitive adhesives, particularly for high-adhesion double-sided pressure-sensitive adhesive tapes. The pressure-sensitive adhesives should rapidly wet surfaces with different surface energies, e.g., metals, plastic surfaces such as PP, PE, polycarbonate, and automotive paints, thereby establishing high adhesion. Furthermore, the pressure-sensitive adhesives and the bonds produced with them should exhibit good shear strength even at elevated temperatures, high resistance to humid heat, and high bond strength under dynamic loading, the latter especially at low temperatures. Finally, permanent mechanical stress on the bond should not lead to dewetting of the adhesive tape from the surface.

[0022] The solution to the problem is based on the idea of ​​using a poly(meth)acrylate as the main component of the pressure-sensitive adhesive, which is essentially based on a mixture of monomers with singly branched and unbranched alcohol components.

[0023] A first and general subject matter of the invention is a pressure-sensitive adhesive which contains at least 50% by weight, based on the total weight of the pressure-sensitive adhesive, of at least one polymer A which can be traced back to the following monomer composition: a1) 55 to 75 wt.% of 2-propylheptyl acrylate (PHA) and / or isodecyl acrylate; a2) 20 to 40 wt.% of at least one (meth)acrylic acid ester, the alcohol component of which is based on a linear C 1 -C 18 alcohol; a3) 5 to 15 wt.% of acrylic acid, except for a polymer obtained by the following steps: Filling a 300 l reactor conventional for radical polymerizations with 62.0 kg of 2-propylheptyl acrylate, 27.0 kg of butyl acrylate, 11.0 kg of acrylic acid, and 72.4 kg of acetone / isopropanol (94:6); passing nitrogen gas through the reactor for 45 minutes with stirring; heating the reactor to 58 °C; adding 50 g of 2,2'-azobis(2-methylbutyronitrile); heating the external heating bath to 75 °C and conducting the reaction at this external temperature; adding 50 g of 2,2'-azobis(2-methylbutyronitrile) after 1 h of reaction time; diluting with 20 kg of acetone / isopropanol (94:6) after 3 h and with 10 kg of acetone / isopropanol (94:6) after 6 h. Addition of 0.15 kg of bis(4-tert-butylcyclohexyl)peroxydicarbonate after 5.5 and 7 h to reduce the residual initiators; the reaction was stopped after 24 h and cooled to room temperature.

[0024] A pressure-sensitive adhesive according to the invention is characterized in particular by rapid wetting of low-energy surfaces and high resistance to dewetting even under sustained mechanical stress on the bond, as well as by good other adhesive properties.

[0025] According to the invention, a pressure-sensitive adhesive is understood, as is generally customary, to be a substance that is permanently tacky and adhesive, particularly at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and remains adhered there, whereby the pressure to be applied and the duration of this pressure are not further defined. In some cases, depending on the exact type of pressure-sensitive adhesive, the temperature and humidity, as well as the substrate, the application of short-term, minimal pressure, which does not go beyond a light touch for a brief moment, is sufficient to achieve the adhesion effect; in other cases, a longer exposure to high pressure may be necessary.

[0026] Pressure-sensitive adhesives have special, characteristic viscoelastic properties that lead to their permanent tack and adhesive strength. They are characterized by the fact that, when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The respective proportions of both processes are in a specific relationship to each other, depending on the precise composition, structure, and degree of crosslinking of the pressure-sensitive adhesive, as well as the speed and duration of the deformation and the temperature.

[0027] The viscous flow component 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 pressure-sensitive adhesion (also referred to as tack or surface adhesion) and thus often also to high adhesive strength. Highly cross-linked systems, crystalline, or glass-like polymers, are generally not or at least only slightly tacky due to the lack of flowable components.

[0028] The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transfer of forces acting on an adhesive bond. They ensure that an adhesive bond can sufficiently withstand continuous loading, for example, in the form of permanent shear stress, over an extended period of time.

[0029] For a more precise description and quantification of the degree of elastic and viscous components as well as the relationship between the components, the storage modulus (G') and loss modulus (G"), which can be determined using Dynamic Mechanical Analysis (DMA), can be used. G' is a measure of the elastic component, G" a measure of the viscous component of a material. Both parameters depend on the deformation frequency and the temperature.

[0030] These parameters can be determined using a rheometer. The material under test is subjected to sinusoidal oscillating shear stress, for example, in a plate-on-plate arrangement. Shear stress-controlled devices measure the deformation as a function of time and the temporal offset of this deformation relative to the application of the shear stress. This temporal offset is referred to as the phase angle δ.

[0031] The storage modulus G' is defined as follows: G' = (τ / γ) •cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G" is: G" = (τ / γ) •sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector).

[0032] A substance is generally considered to be pressure-sensitive adhesive and is defined as pressure-sensitive adhesive in the sense of the invention if, at room temperature, here by definition at 23°C, in the deformation frequency range from 10 0< to 10 1< rad / sec, G' lies at least partly in the range from 10 3< to 10 7< Pa and if G" also lies at least partly in this range. "Partially" means that at least a section of the G' curve lies within the window spanned by the deformation frequency range from 10 0< to 10 1< rad / sec (abscissa) and the range of G' values ​​from 10 3< to 10 7< Pa (ordinate). This applies accordingly to G".

[0033] The term "(meth)acrylic acid ester" is generally understood to encompass both acrylic acid esters and methacrylic acid esters. The same applies to the term "(meth)acrylate."

[0034] The pressure-sensitive adhesive of the invention is preferably thermally crosslinked using at least one epoxycyclohexyl derivative in the absence of proton acceptors, electron pair donors, and electron pair acceptors. Thermal crosslinking results in advantageous homogeneous crosslinking throughout the entire layer of the composition, whereas, for example, with radiation-crosslinked compositions, a crosslinking profile with decreasing crosslinking density toward the center of the composition is observed. A homogeneously crosslinked pressure-sensitive adhesive layer enables the uniform distribution of stresses that may occur when the bond is subjected to stress. Adhesive and cohesive properties can be very precisely balanced for the entire layer, thus enabling resilient bonds with a precisely predictable property profile to be obtained.The pressure-sensitive adhesive according to the invention is particularly preferably thermally crosslinked using at least one epoxycyclohexyl derivative in the absence of any crosslinking accelerators.

[0035] The pressure-sensitive adhesive of the invention preferably contains no bond-strength-enhancing resin. Resins typically added to increase the bond strength of pressure-sensitive adhesives include, for example, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, alkylaromatic hydrocarbon resins; terpene resins, terpene-phenolic resins; rosin resins, especially hydrogenated, non-hydrogenated, and disproportionated rosin resins; functional hydrocarbon resins, and natural resins. The absence of bond-strength-enhancing resins has a positive effect on the cohesive properties of pressure-sensitive adhesives of the invention, which are inherently very soft and conformable and exhibit high tack.

[0036] Polymer A preferably has a weight-average molecular weight M w of at least 500,000 g / mol, particularly preferably at least 700,000 g / mol. Polymer A also preferably has a weight-average molecular weight M w of at most 1,700,000 g / mol. The polydispersity PD, i.e., the breadth of the molar mass distribution, which is determined as the quotient of the weight-average molecular weight M w and the number-average molecular weight M n, for polymer A is preferably 10 ≤ PD ≤ 100, particularly preferably 20 ≤ PD ≤ 80.

[0037] In one embodiment, the pressure-sensitive adhesive of the invention comprises a blend of one or more polymers A and one or more synthetic rubbers. The synthetic rubber(s) are preferably selected from the group consisting of styrene-butadiene-styrene rubbers; styrene-isoprene-styrene rubbers; and hydrogenated derivatives of the aforementioned rubbers.

[0038] The invention further provides an adhesive tape comprising a foamed carrier and a pressure-sensitive adhesive composition according to the invention. The foamed carrier preferably comprises a syntactic polymer foam. The term "syntactic foam" describes a special form of closed-cell foam whose cavities are formed by hollow glass spheres, hollow ceramic spheres, and / or hollow polymer spheres.

[0039] On the back of the syntactic polymer foam layer, for example, a liner or a conventional film material can be provided for stabilization or covering, so that at least a three-layer system comprising the at least two-layer adhesive tape according to the invention is present.

[0040] In the case of sufficiently thick polymer foam layers, the side of the polymer foam layer facing away from the pressure-sensitive adhesive layer, which is exposed in two-layer systems, can also be stabilized by being strongly crosslinked by a crosslinking process with a low penetration depth, so that only part of the foam carrier layer is strongly crosslinked, while on the other side of the carrier facing the pressure-sensitive adhesive layer, the originally existing, more viscoelastic properties are retained.

[0041] Particularly preferably, a pressure-sensitive adhesive is arranged on both sides of the foamed carrier, one of the pressure-sensitive adhesives being a pressure-sensitive adhesive of the invention. In particular, a pressure-sensitive adhesive of the invention is arranged on both sides of the foamed carrier. This is advantageous because, in this case, both sides of the adhesive tape exhibit the advantageous adhesive properties of the pressure-sensitive adhesive of the invention.

[0042] In a specific embodiment, a pressure-sensitive adhesive is arranged on both sides of the foamed carrier, and the two pressure-sensitive adhesives contain identical additives in identical concentrations, in particular functional additives and / or fillers. Likewise, both pressure-sensitive adhesives can also be free of functional additives and / or fillers. In a specific embodiment, a pressure-sensitive adhesive, in particular a pressure-sensitive adhesive according to the invention, is arranged on both sides of the foamed carrier, and the pressure-sensitive adhesives are chemically, physically, and / or dimensionally identical. In particular, both pressure-sensitive adhesives are completely identical, with minor discrepancies, such as those that may result, for example, from impurities within the scope of the ubiquitous concentration, from production-related inaccuracies, and similar other sources, being irrelevant.

[0043] The foamed carrier preferably contains at least 50 wt.%, based on the total weight of the foam, of at least one polymer selected from the group consisting of rubbers, in particular natural rubbers, polyurethanes, poly(meth)acrylates, and styrene block copolymers, as well as blends of the aforementioned polymers. The foamed carrier particularly preferably contains at least 50 wt.%, based on the total weight of the foam, of one or more poly(meth)acrylates.

[0044] In particular, the foamed carrier contains at least 50% by weight, based on the total weight of the foam, of at least one poly(meth)acrylate B, which can be traced back to the following monomer composition: b1) 65 to 97 wt.% ethylhexyl acrylate and / or butyl acrylate, b2) 0 to 30 wt.% methyl acrylate, b3) 3 to 15 wt.% acrylic acid.

[0045] The polymers present in the foamed carrier, particularly preferably polymer B, preferably have a weight-average molecular weight M w of at least 500,000 g / mol, particularly preferably at least 700,000 g / mol. Likewise preferably, the polymers present in the foamed carrier have a weight-average molecular weight M w of at most 1,700,000 g / mol. The polydispersity PD, i.e., the breadth of the molar mass distribution, which is determined as the quotient of the weight-average molecular weight M w and the number-average molecular weight M n, for the polymers present in the foamed carrier is preferably 10 ≤ PD ≤ 100, particularly preferably 20 ≤ PD ≤ 80.

[0046] Both the polymers contained in the pressure-sensitive adhesive of the invention and those present in the foamed carrier can preferably be prepared by free-radical polymerization, preferably in solution, according to the prior art. In the case of subsequent processing from the melt, the solvent is removed after polymerization.

[0047] The foamed carrier is preferably formed into a layer from the melt. Thermal crosslinking of the foamed layer preferably takes place. The pressure-sensitive adhesives of the invention can also be formed from the melt. However, since these layers are typically only produced in layer thicknesses of up to 100 µm, they are also excellently suited for coating from solution and subsequent drying.

[0048] For technical reasons, very thick polymer layers such as the foamed carrier layer are much easier to produce from the melt (so-called hotmelts) than from the polymer solution. To define a melt of an amorphous polymer—such as a polyacrylate—the criteria specified in FR Schwarzl, "Polymer Mechanics: Structure and Mechanical Behavior of Polymers," Springer Verlag, Berlin, 1990, are used, according to which the viscosity is on the order of η ≈ 10 4 < Pa s and the internal damping tan δ reaches values ​​of ≥ 1.

[0049] When the polymer layers of the pressure-sensitive adhesives of the invention and the foamed carrier of the adhesive tape of the invention are produced by coating from the melt, a problem arises resulting from the preferred thermal crosslinking. On the one hand, the thermal crosslinker must be added before coating to initiate subsequent thermal crosslinking; on the other hand, the crosslinker is then exposed to the high temperatures required to generate and maintain the polymer melt. This can lead to uncontrolled polymer crosslinking (so-called gelling) even before controlled crosslinking occurs. To suppress this gelling as much as possible, very inert crosslinkers are usually used in the hotmelt process, and only shortly before coating. However, to achieve satisfactory crosslinking results after coating, so-called accelerators are often added.

[0050] The use of accelerators can also be useful and is frequently used for polymer systems coated from solution that are to be thermally crosslinked. The thermally initiated crosslinking process is usually combined with the thermal removal of the solvent from the applied layer (i.e., the drying of the bulk layer). Excessively rapid removal of the solvent leads to a poorly formed, uneven, and inhomogeneous layer, as excessively radical drying can lead to blistering, for example. For this reason, drying is preferably carried out at moderate temperatures. To ensure good and sufficiently rapid crosslinking, accelerators are also typically added to the solvent systems.

[0051] A solution coating is often preferred when the thickness of the resulting layers is not very large, so that an increased viscosity of the polymer solution to be applied (compared to a largely solvent-free melt) is not associated with significant problems.

[0052] According to the invention, the foamed carrier layer is preferably crosslinked with the participation of accelerators. Proton acceptors, electron pair donors (Lewis bases), and / or electron pair acceptors (Lewis acids) are used as accelerators or accelerating substances. Accelerators are compounds or chemicals that support crosslinking reactions by ensuring a reaction rate sufficient for the invention. This occurs, in particular, catalytically (by activating the crosslinking reaction) and / or by converting functional groups of the crosslinking substances or the macromolecules to be crosslinked into functional groups that can react in the sense of a linking reaction between the macromolecules (bridge formation, network formation) or with other functional groups via the crosslinking substances.

[0053] The accelerators themselves do not participate in such a cross-linking reaction (i.e., they do not cross-link themselves), but can be incorporated into or linked to the network in the form of reaction products or fragments. An accelerator thus significantly improves the reaction kinetics of the cross-linking reaction.

[0054] Crosslinkers, on the other hand, are substances that, through their own functional groups, can participate in a reaction, particularly an addition or substitution reaction, leading to the formation of a bridge to form a network. Furthermore, they can contain functional groups that—for example, under the influence of accelerators mentioned above or through other processes—are converted during the crosslinking reaction into functional groups that subsequently lead to the formation of a bridge between the macromolecules of the polymers to be crosslinked.

[0055] The crosslinking reaction in the absence of an accelerator would not proceed at all or only insufficiently quickly at selected reaction parameters – in particular, according to the invention, a temperature below the processing temperature of the polymers of the foamed carrier layer. For example, many epoxies used as crosslinkers for polyacrylates are inherently rather inert, so they do not produce satisfactory crosslinking results without an accelerator.

[0056] Proton donors, in particular carboxylic acids or carboxylic acid groups or their deprotonated derivatives, are not to be counted as accelerators in the sense of the invention.

[0057] The presence of accelerators in the pressure-sensitive adhesives of the invention also has its disadvantages. Nitrogen-containing accelerators, such as amines, in particular, tend to yellow over time due to oxidation processes, making such accelerator systems poorly suited or unsuitable, particularly for transparent pressure-sensitive adhesives or multilayer pressure-sensitive adhesive tapes intended for use primarily for optical purposes.

[0058] Accelerators that are salt-like or form salts (especially basic accelerators), such as the aforementioned amines or zinc chloride, lead to an increased moisture absorption capacity of the product, as salts generally have hygroscopic properties. Such accelerators are particularly unsuitable for pressure-sensitive adhesives, which, due to their intended application, require very high resistance to humid heat.

[0059] According to the invention, the aim is therefore to achieve thermal crosslinking of the pressure-sensitive adhesives of the invention, particularly for those in contact with air, with epoxycyclohexyl derivatives without the addition of accelerators. The absence of accelerators refers in particular to externally added accelerators (i.e., not polymerized or incorporated into the polymer backbone); however, the pressure-sensitive adhesives of the invention particularly preferably contain neither externally added nor polymerized accelerators, and in particular, no accelerators at all.

[0060] The nature of the polymer layers, here in particular of the pressure-sensitive adhesives according to the invention, and their physical properties (for example viscoelasticity, cohesion, elastic component) can be influenced by the type and degree of their crosslinking.

[0061] A pressure-sensitive adhesive according to the invention is therefore preferably crosslinked by at least one epoxycyclohexyl derivative, particularly preferably by at least one epoxycyclohexyl carboxylate, in particular at least by (3,4-epoxycyclohexane)methyl-3,4-epoxycyclohexylcarboxylate (CAS 2386-87-0).

[0062] Epoxycyclohexyl derivatives are preferably present in the pressure-sensitive adhesive to be crosslinked in a total amount of up to 0.4 wt.%, very preferably up to 0.3 wt.%, based in each case on the total amount of polymers to be crosslinked. At crosslinker amounts of more than 0.3 parts by weight per 100 parts by weight of polymer, increasing losses in adhesive strength are to be expected, and wetting deteriorates dramatically. Particularly preferred crosslinker amounts are, for example, in the range from 0.12 to 0.30 wt.%, in particular in the range from 0.15 to 0.25 wt.%, based in each case on the total amount of polymers to be crosslinked.

[0063] The foamed carrier is also preferably thermally crosslinked, which leads to a very homogeneous formation of this layer. The foamed carrier is particularly preferably thermally crosslinked using at least one glycidyl ether, in particular at least one polyglycidyl ether, very preferably at least pentaerythritol tetraglycidyl ether (CAS 3126-63-4). The crosslinking of the foamed carrier is preferably carried out in combination with an amine, particularly preferably with isophoronediamine (CAS 2855-13-2), as an accelerator. The total proportion of crosslinker in the foamed carrier layer to be crosslinked is preferably up to 1.0 wt. %, more preferably up to 0.8 wt. %, based in each case on the total amount of polymers to be crosslinked. Preferred amounts of crosslinker are, for example, in the range from 0.05 to 0.6, in particular from 0.10 to 0.5 wt. %, based in each case on the total amount of polymers to be crosslinked.

[0064] The accelerator is preferably present in an amount of 0.1 to 1.5 wt.%, more preferably 0.15 to 1.2 wt.%, in each case based on the total amount of the polymers to be crosslinked.

[0065] The presence of an amine accelerator in the foamed carrier is uncritical, especially in three- or multi-layer structures, since in these cases the carrier layer is largely shielded from the influence of oxidizing substances such as atmospheric oxygen by the outer adhesive or pressure-sensitive adhesive layers.

[0066] The thermal crosslinking of the foamed carrier and one or both pressure-sensitive adhesive layers can be carried out simultaneously, for example when the pressure-sensitive adhesives are coated onto the not yet crosslinked foamed carrier or when the layers are formed together in a special process.

[0067] However, the individual layers can also be thermally crosslinked in separate processes, for example, when the pressure-sensitive adhesives are coated onto the already thermally crosslinked carrier layer and then thermally crosslinked, or when the pressure-sensitive adhesives are formed and thermally crosslinked elsewhere—for example, on a temporary carrier such as a release material—and then laminated onto the already crosslinked foamed carrier. For this purpose, it can be particularly advantageous to chemically and / or physically pretreat the foamed carrier and / or the pressure-sensitive adhesive(s), for example, by corona and / or plasma treatment and / or reactive corona and / or reactive plasma treatment (use of gases such as nitrogen, oxygen, fluorine, and / or others) and / or flame treatment.

[0068] The production of double-sided, in particular three-layer adhesive tapes according to the invention can also be carried out according to the description for three- or multi-layer systems in EP 05 792 143 A1. The production and coating processes described therein can also be applied analogously to the adhesive tapes of this document; the disclosure content of EP 05 792 143 A1 is therefore to be considered explicitly included in the present disclosure. The same applies to the presentation of the product structures described in EP 05 792 143 A1. In particular, foaming with microballoons to produce the foamed carrier is advantageously carried out according to the processes described in EP 2 414 143 A1 and DE 10 2009 015 233 A1.

[0069] The foamed carrier is preferably considered a very highly viscous liquid that exhibits flow behavior (also referred to as "creep") under pressure. Viscoelastic masses in this sense preferably exhibit the ability to flow more or less slowly, preferably under gravity, i.e., under the load of their own weight, and in particular to flow onto or wet a substrate. At the very least, however, this effect occurs under external pressure. An increase in pressure, for example, by pressing the adhesive tape onto a substrate, can significantly accelerate this behavior.

[0070] Viscoelastic masses in the sense of the preferred foamed support described above also possess the ability to relax the forces acting upon them when subjected to slow forces. They are thus capable of dissipating the forces into vibrations and / or deformations, which may also be - at least partially - reversible, thus "buffering" the acting forces and preferably avoiding mechanical destruction caused by the acting forces, or at least reducing it or delaying the onset of destruction. In the case of a very rapidly acting force, viscoelastic masses typically exhibit elastic behavior, i.e., the behavior of a completely reversible deformation, whereby forces that exceed the elastic capacity of the mass can lead to fracture.

[0071] In contrast, elastic materials exhibit the described elastic behavior even under slow force application. Elastic behavior generally has a negative effect on wetting. Therefore, it is advantageous that the pressure-sensitive adhesives of the invention, despite their pronounced elastic behavior under rapid force loading, exhibit overall more viscoelastic behavior, particularly over a long time scale, behaving more viscously like a liquid, thus ensuring optimal and, in particular, rapid wetting.

[0072] The foamed carrier preferably contains at least one foaming agent selected from the group consisting of hollow polymer spheres, solid polymer spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres, and solid carbon spheres ("carbon microballoons"). The foamed carrier particularly preferably contains at least partially expanded polymeric microhollow bodies; in particular, those polymeric microhollow bodies that can expand from their basic state upon the application of heat and / or other energy, such as gas- and / or liquid-filled polymer spheres whose shell consists of a thermoplastic material such as polymethyl methacrylate, PVDC, or polystyrene. The pressure-sensitive adhesives of the invention can also contain such foaming agents.

[0073] The foamed carrier preferably contains silica, particularly preferably precipitated silica surface-modified with dimethyldichlorosilane. This is advantageous because it allows the thermal shear strength of the carrier layer to be adjusted, and in particular increased. Silicas are also excellently suited for transparent carriers. Preferably, silica is present in the foamed carrier in quantities of up to 15% by weight, based on the total of all polymers present in the foamed carrier. The pressure-sensitive adhesives of the invention may also contain silica.

[0074] The foamed carrier and / or the pressure-sensitive adhesives of the invention, in particular the pressure-sensitive adhesives of the invention, preferably contain at least one plasticizer. The plasticizer is preferably selected from the group consisting of (meth)acrylate oligomers, phthalates, cyclohexanedicarboxylic acid esters (e.g., Hexamoll®< DINCH, BASF, CAS 166412-78-8), water-soluble plasticizers, plastic resins, phosphates (e.g., Levagard®< DMPP, Lanxess, CAS 18755-43-6), and polyphosphates.

[0075] Adhesive tapes according to the invention, particularly double-sided ones, have a number of advantages in general and in the embodiments described above: Due to the preferred thermal crosslinking, the adhesive tapes do not exhibit a crosslinking profile throughout their layers. Viscoelastic layers or pressure-sensitive adhesive layers crosslinked by actinic radiation (ultraviolet radiation, electron beams) exhibit a crosslinking profile throughout the respective crosslinked layer. Thermally crosslinked layers of adhesive do not exhibit this behavior, since the heat can penetrate evenly into the layer.

[0076] Pressure-sensitive adhesives of the invention thermally crosslinked using epoxycyclohexyl derivatives exhibit higher bond strength than systems crosslinked using other crosslinkers. This finding is of great importance for the adhesive tapes of the invention. If a foamed polyacrylate-based carrier is used and coated on at least one side with a pressure-sensitive adhesive of the invention thermally crosslinked, in particular with epoxycyclohexyl derivatives, both the bond strengths and the wetting behavior on this side of the adhesive tape are better than with systems which have the corresponding pressure-sensitive adhesive on an elastic polymer carrier or which have the same, preferably viscoelastic carrier, but a different, albeit inherently significantly stickier, pressure-sensitive adhesive.

[0077] The adhesive strength of an adhesive tape according to the invention is determined not only by the outer pressure-sensitive adhesive but also by the foamed carrier, so that the overall system is important for the outstanding adhesive properties. The idea underlying the adhesive tapes according to the invention therefore involves the combination of a preferably viscoelastic, relatively soft foam layer with a pressure-sensitive adhesive layer that is not inherently highly adhesive (for example, with elastic film substrates as carriers). This results in the interaction of the two layers improving the adhesive behavior on the side of the pressure-sensitive adhesive layer, thus achieving adhesive strengths and wetting behavior that are significantly better than with inherently more highly adhesive pressure-sensitive adhesive layers on their own or on elastic carriers.

[0078] With the present invention, it has been possible to qualify a cohesive pressure-sensitive adhesive with relatively low tack as a pressure-sensitive adhesive for a very strong and fast-wetting adhesive tape by providing a foam layer adjacent to this cohesive polymer layer.

[0079] In adhesive tapes where the bond strength is determined solely by the outer pressure-sensitive adhesive, a compromise between adhesion and cohesion often has to be made (see the introductory part of the present description). According to the invention, it has been possible to achieve excellent overall properties by controlling the properties of two different layers, which can be optimized individually. In particular, the bond strength of the adhesive tapes according to the invention to steel and to non-polar automotive paints on the side of the pressure-sensitive adhesive according to the invention is at least 40 N / cm or more, preferably after 12 hours, more preferably after 8 hours. Particularly preferably, this bond strength is not measurable at all, since a force of more than 50 N / cm leads to the desired cohesive splitting of the syntactic polymer foam. In addition, the adhesive tapes according to the invention have long shear strengths at high temperatures (for example, at approximately 70°C).

[0080] For better handling or storage of the adhesive tapes according to the invention, they can be provided on one or both sides with a release material, which can be, for example, silicones, films, siliconized films or papers, surface-treated films or papers or the like, i.e. so-called liners.

[0081] The adhesive tapes of the invention may comprise additional layers beyond the layers described above, i.e., multilayer systems with a layer sequence of more than three. It is particularly advantageous if the foamed carrier layer is preferably provided directly or at least indirectly with a pressure-sensitive adhesive layer of the invention, because then the adhesive advantages already described are realized.

[0082] The adhesive tapes according to the invention are characterized by the fact that they can be manufactured as very thick products that also possess very high adhesive strengths. Such products are used, for example, in the construction industry, the automotive industry, or for bonding applications that require compensation for uneven surfaces or cavities.

[0083] Due to the good relaxation behavior of the foamed carrier layer, the adhesive tapes of the invention are suitable for absorbing forces such as mechanical stresses, impacts, and the like, and for dissipating their energy. The adhesive tapes of the invention are therefore also highly suitable wherever a shock- and / or vibration-damping effect is desired, such as for bonding fragile objects, in the electronics sector, or the like. It is particularly advantageous to use the adhesive tapes of the invention when materials with different thermal expansion coefficients are to be bonded together, since their relaxation capacity allows the adhesive tapes of the invention to dissipate stresses resulting from the different expansion behavior of the bonded objects or surfaces.Conventional adhesive tapes, on the other hand, often tend to fail when the expansion behavior of the bonded objects varies greatly, meaning that the bonded area becomes weakened or even breaks.

[0084] The adhesive tapes according to the invention can be produced in conventional adhesive tape thicknesses of a few to a few hundred micrometers, but particularly advantageously in thicknesses of more than 300 µm, for example 500 µm or more, 1000 µm or more, 1500 µm or more, 2000 µm or more, or even 3000 µm or more. Even thicker products are also feasible.

[0085] In an adhesive tape according to the invention, the foamed carrier preferably has a layer thickness of 300 to 2500 µm, more preferably of 400 to 2400 µm, and the at least one pressure-sensitive adhesive has a layer thickness of 40 to 150 µm, more preferably of 50 to 100 µm.

[0086] The adhesive tapes according to the invention are also particularly suitable for bonding and attaching trim strips, emblems, and bumpers to non-polar automotive paints. If necessary, these surfaces can be treated with a primer prior to bonding to further increase bond strength.

[0087] Further areas of application for which the adhesive tapes according to the invention are outstandingly suitable are, for example, building construction and expansion, building equipment and the architectural sector (interior and / or exterior), the DIY sector, model making, furniture manufacturing, shipbuilding and aircraft construction, the electronics and electrical industries (for example for entertainment electronics, white goods, brown goods, and due to the good heat resistance also red goods) and road traffic (road signage and the like). Experimental part Measurement methods: Solids content (measurement method A1):

[0088] The solids content is a measure of the proportion of non-evaporable components in a polymer solution. It is determined gravimetrically by weighing the solution, then evaporating the evaporable components in a drying oven at 120 °C for 2 hours, and reweighing the residue. K-value (according to FIKENTSCHER) (measurement method A2):

[0089] The K value is a measure of the average molecular size of high-polymer materials. For the measurement, one-percent (1 g / 100 ml) toluene polymer solutions were prepared, and their kinematic viscosities were determined using a Vogel-Ossag viscometer. After normalization to the viscosity of toluene, the relative viscosity is obtained, from which the K value can be calculated according to Fikentscher's method (Polymer 8 / 1967, 381 ff.). Gel permeation chromatography GPC (measurement method A3):

[0090] The weight-average molecular weight (MW) and polydispersity (PD) values ​​given in this document refer to determinations by gel permeation chromatography. The determination is carried out using 100 µl of a filtered sample (sample concentration: 4 g / l). Tetrahydrofuran with 0.1 vol.% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C. A PSS-SDV column, 5 µ, 10 3 < Å, ID 8.0 mm x 50 mm, is used as the precolumn. Columns of the PSS-SDV type, 5 µ, 10 3 < Å, 10 5 < Å, and 10 6 < Å, each with ID 8.0 mm x 300 mm, are used for separation (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate is 1.0 ml per minute. Calibration is performed against PMMA standards (polymethyl methacrylate calibration). Density determination via mass application and layer thickness (measurement method A4)

[0091] The density ρ of a coated self-adhesive is determined by the ratio of the basis weight to the respective layer thickness: ρ = m V = MA d ρ = kg m 2 ⋅ m = kg m 3 MA = mass application / area weight (without liner weight) in [kg / m 2< ] d = layer thickness (without liner thickness) in [m]

[0092] This process yields the bulk density.

[0093] This density determination is particularly suitable for determining the total density of finished, even multi-layer, products. 180° adhesive strength test (measurement method H1);

[0094] A 20 mm wide strip of the pressure-sensitive adhesive coated on polyester was applied to steel panels that had previously been washed twice with acetone and once with isopropanol. The pressure-sensitive adhesive strip was pressed onto the substrate twice with a contact pressure equivalent to a weight of 2 kg. The tape was then immediately peeled off the substrate at a speed of 300 mm / min and at an angle of 180°. All measurements were performed at room temperature.

[0095] The measurement results are given in N / cm and are averaged from three measurements. Shear life (measurement method H2);

[0096] A 13 mm wide and more than 20 mm long (e.g., 30 mm) strip of adhesive tape was applied to a smooth steel surface that had been cleaned three times with acetone and once with isopropanol. The bonding area was 20 mm x 13 mm (length x width), with the adhesive tape extending beyond the test panel at the edges (e.g., by 10 mm, corresponding to the length of 30 mm specified above). The adhesive tape was then pressed onto the steel support four times with a contact pressure equivalent to a weight of 2 kg. This sample was suspended vertically with the protruding end of the adhesive tape facing downward.

[0097] At room temperature, a weight of, for example, 1 kg (10 N) was attached to the protruding end of the adhesive tape; the respective weights are listed in the examples. The measurements were conducted under standard conditions (23 °C, 55% humidity) and at 70 °C in an oven.

[0098] The measured shear times (times until the adhesive tape is completely detached from the substrate; the measurement is stopped at 10,000 min) are given in minutes and correspond to the average of three measurements. Microshear test (measurement method H3)

[0099] This test is used to quickly check the shear strength of adhesive tapes under temperature stress. Sample preparation for microshear test:

[0100] An adhesive tape cut from the respective sample (approximately 50 mm long and 10 mm wide) was bonded to a steel test plate cleaned with acetone, so that the steel plate extended beyond the adhesive tape on both sides and the adhesive tape extended beyond the test plate by 2 mm at the upper edge. The bonded area of ​​the sample was 13 mm x 10 mm (height x width).

[0101] The bonded area was then rolled over six times with a 2 kg steel roller at a speed of 10 m / min. The adhesive tape was reinforced flush with a sturdy adhesive strip, which served as a support for the displacement sensor. The sample was suspended vertically using the test plate. Microshear test:

[0102] The sample to be measured was loaded at its lower end with a weight of 1000 g. The test temperature was 40 °C, and the test duration was 30 minutes (15 minutes of loading and 15 minutes of unloading). The shear elongation after the specified test duration at constant temperature is given as the result in µm, namely as the maximum value ["max"; maximum shear elongation after 15 minutes of loading]; and as the minimum value ["min"; shear elongation ("residual deflection") 15 minutes after unloading; upon unloading, a return movement occurred due to relaxation]. The elastic component is also given as a percentage ["elast"; elastic component = (max - min) 100 / max]. 90° adhesive strength steel open and covered side (measurement method M1):

[0103] The bond strength to steel was determined under conditions of 23 °C + / - 1 °C and 50% + / - 5% relative humidity. The samples were cut to a width of 20 mm and bonded to a steel plate. The steel plate was cleaned and conditioned prior to testing. The plate was first wiped with acetone and then left to air for 5 minutes to allow the solvent to evaporate. Three-layer composite:

[0104] The side of the three-layer composite facing away from the test substrate was then covered with a 50 µm aluminum foil, which prevented the sample from stretching during the measurement. The test sample was then rolled onto the steel substrate. For this purpose, the tape was rolled back and forth five times using a 2 kg roller at a winding speed of 10 m / min. Immediately after rolling, the steel plate was pushed into a special holder that allowed the sample to be pulled vertically upwards at an angle of 90 °. The adhesive strength was measured using a Zwick tensile testing machine. When applying the covered side to the steel plate, the open side of the three-layer composite was first laminated against the 50 µm aluminum foil, the release material was removed and adhered to the steel plate, rolled on in the same way, and measured.

[0105] The measurement results of both sides, open and covered, are given in N / cm and are averaged from three measurements. Sample on 23 µm PET film:

[0106] The single-sided test specimen was applied to the steel substrate and then pressed five times with a 2 kg roller at a speed of 10 m / min. Immediately after rolling, the steel plate was pushed into a special holder that allowed the specimen to be pulled vertically upwards at an angle of 90°. The adhesive strength was measured using a Zwick tensile testing machine. The measurement results are given in N / cm and are averaged from three measurements. Shear life - open and covered side (measurement method M2):

[0107] The sample was prepared in a test environment of 23 °C + / - 1 °C and 50% + / - 5% relative humidity. The test sample was cut to 13 mm and bonded to a steel plate. The bonding area was 20 mm x 13 mm (length x width). Before measurement, the steel plate was cleaned and conditioned. To do this, the plate was first wiped with acetone and then left to air for 5 minutes to allow the solvent to evaporate. After bonding, the open side was reinforced with 50 µm aluminum foil and rolled back and forth twice using a 2 kg roller. A belt loop was then attached to the protruding end of the three-layer composite. The entire assembly was then suspended from a suitable device and loaded with a weight of, for example, 1 kg (10 N); the weight is specified in the respective examples. The suspension device was designed so that the weight applied an angle of 179° + / - 1° to the sample.This ensured that the three-layer composite could not peel off the bottom edge of the panel. The measured shear strength, the time between hanging and falling off the sample, is given in minutes and corresponds to the average of three measurements. To measure the covered side, the exposed side was first reinforced with 50 µm aluminum foil, the release material was removed, and then bonded to the test panel as described. The measurement was conducted under standard conditions (23 °C, 55% humidity). Step wetting test with rigid substrates / Rigid Rigid Wet-out Test (Measurement method M3, Fig. 1, 2a (view from above) and 2b (view from below)):

[0108] The sample preparation was carried out in a test environment of 23 °C + / - 1 °C and 50 % + / - 5 % relative humidity. Before the measurement, a polycarbonate plate (1, Fig. 1 ) was cleaned and conditioned. The plate was first wiped with isopropanol and then left to air for 5 minutes to allow the solvent to evaporate. The test sample (2, Fig. 1 and 2a) was cut to a width of 20 mm, glued centrally to the polycarbonate sheet, and rolled back and forth five times with a roller. The weight of the roller was adjusted to the width of the test sample, so that the test sample was pressed down with 2 kg / cm; for a width of 20 mm, a 4 kg roller was used. Care was taken to ensure that the test sample thoroughly wetted the sheet. The bonded sample was then stored for 24 hours at a test temperature of 23 °C + / - 1 °C and 50% + / - 5% relative humidity to ensure relaxation of the adhesive tape before further processing.

[0109] An additional polycarbonate plate (3, Fig. 1 and 2a ) was designed with levels (4, Fig. 1 ) with a defined height at a defined distance (5, Fig. 2a) of 20 mm and then cleaned and conditioned according to the method described above. Steps with heights of 20 and 100 µm were used, and a sample without steps was measured as a reference. The substrate with the steps (3, lower layer) was placed on a solid surface with the steps facing upwards, and the substrate (1) with the test sample applied was slowly and evenly placed on the steps with as little pressure as possible (rigid-rigid application), so that the adhesive tape did not actively penetrate the cavities (6, Fig. 1 and 2b ) was pressed between the steps. The joined panels were then evenly rolled over once with a roller of a defined weight. The roller's pressing speed remained constant at approximately 2.4 m / min.

[0110] To determine initial wetting, no step (step height 0 cm) and a 1 kg roll were used. For the step test, a step height of 100 µm and a 4 kg roll were used. In both cases, triplicate determinations were performed. When comparing different adhesive tapes, care was taken to ensure they had the same thickness.

[0111] For both tests, a high-resolution photo of all surfaces between the steps (4) was taken in a photo booth after rolling, using defined lighting. The wetted area was then quantified using image processing software via grayscale analysis. This was done using image analysis, more specifically, an auto-threshold that uses Otsu analysis. The proportion of wetted area as a function of time is given in [%]. The dewetting is also calculated from the difference in [%]. Commercially available chemicals used

[0112] Chemical compound Trade name Manufacturer CAS No. Bis-(4- tert- butylcyclohexyl)peroxydicarbonat Perkadox ®< 16 Akzo Nobel 15520-11-3 2,2'-Azobis(2-methylpropionitrile), AIBN Vazo ®< 64 DuPont 78-67-1 Acrylic acid AS (Tg = 106°C) - Sigma-Aldrich 79-10-7 Butyl acrylate BA (iso index 0, Tg = -43°C) - BASF 141-32-2 2-Ethylhexyl acrylate EHA (iso index 1, Tg = -58°C) - BASF 103-11-7 2-Propylheptylacrylate PHA (iso-index 1, Tg = -69°C) - BASF 149021-58-9 Isodecyl acrylate IDA (iso index 1, Tg = -60°C) - Sartomer 1330-61-6 Heptadecanyl acrylate iC17A (mixture of isomers, iso-index 3.1; Tg = -72°C) - BASF - Isobornyl acrylate IBOA (Tg = 94°C) Visiomer ®< IBOA Evonik 5888-33-5 Pentaerythritol tetraglycidyl ether THE ™< 749 DOW 3126-63-4 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate Uvacure ®< 1500 Cytec Industries Inc. 2386-87-0 Isophoronediamine Vestamin ®< IPD Evonik 2855-13-2 Tetraglycidyl meta-xylenediamine Erisys™< GA-240 CVC 63738-22-7 Resorcinol bis(diphenyl phosphate) Reofos ®< RDP Chemtura 57583-54-7 Microballoons (MB) (dry-unexpanded microspheres, diameter 9 - 15 µm, expansion start temperature 106 - 111 °C, TMA density ≤ 25 kg / m3) Expancel ®< 051 DU 40 Expancel Nobel Industries I. Production of pressure-sensitive adhesives PA1 to PA7

[0113] The preparation of the starting polymers is described below. The polymers investigated are prepared conventionally via free radical polymerization in solution. Polyacrylate pressure sensitive adhesive 1 (PA1):

[0114] A 300 L reactor conventional for radical polymerizations was charged with 11.0 kg of acrylic acid, 27.0 kg of butyl acrylate (BA), 62.0 kg of 2-propylheptyl acrylate (PHA), and 72.4 kg of acetone / isopropanol (94:6). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C and 50 g of Vazo ®< 67 were added. The external heating bath was then heated to 75 °C and the reaction was carried out at a constant external temperature. After a reaction time of 1 h, another 50 g of Vazo ®< 67 were added. After 3 h, the mixture was diluted with 20 kg of acetone / isopropanol (94:6) and after 6 h with 10.0 kg of acetone / isopropanol (94:6). To reduce the residual initiators, 0.15 kg of Perkadox ®< 16 was added after 5.5 and 7 h. The reaction was stopped after 24 h and cooled to room temperature.The polyacrylate was then blended with the crosslinker Uvacure®< 1500, diluted with acetone to a solids content of 30%, and then coated from solution onto a siliconized release liner (50 µm polyester) or onto a 23 µm thick etched PET film. (Coating speed: 2.5 m / min, drying tunnel length: 15 m, temperatures: Zone 1: 40 °C, Zone 2: 70 °C, Zone 3: 95 °C, Zone 4: 105 °C) The coating weight was 50 g / m²< . Molar masses by GPC (measurement method A3): M n = 25,000 g / mol; M w = 1,010,000 g / mol. K value: 50.3. Polyacrylate pressure sensitive adhesive 1 (PA2):

[0115] A 300 L reactor conventional for radical polymerizations was charged with 11.0 kg of acrylic acid, 27.0 kg of BA, 62.0 kg of isodecyl acrylate (IDA), and 72.4 kg of acetone / isopropanol (94:6). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 50 g of Vazo ®< 67 were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at this constant external temperature. After a reaction time of 1 h, another 50 g of Vazo ®< 67 were added. After 3 h, the mixture was diluted with 20 kg of acetone / isopropanol (94:6), and after 6 h with 10.0 kg of acetone / isopropanol (94:6). To reduce the residual initiators, 0.15 kg of Perkadox ®< 16 was added after 5.5 and 7 h. The reaction was stopped after 24 h and cooled to room temperature.The polyacrylate was then blended with the crosslinker Uvacure®< 1500, diluted with acetone to a solids content of 30%, and then coated and dried as described for PA 1. The coating weight was 50 g / m 2< . Molar masses by GPC (Measurement Method A3): M n = 31,400 g / mol; M w = 961,000 g / mol. K value: 49.4. Polyacrylate pressure sensitive adhesive 3 (PA3):

[0116] A 100 L glass reactor conventional for radical polymerizations was charged with 4.0 kg of acrylic acid, 12.0 kg of BA, 24.0 kg of PHA, and 26.7 kg of acetone / petrol 60 / 95 (1:1). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 30 g of AIBN were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at a constant external temperature. After 1 h of reaction time, another 30 g of AIBN were added. After 4 and 8 h, the mixture was diluted with 10.0 kg of acetone / petrol 60 / 95 (1:1) each time. To reduce the residual initiators, 90 g of Perkadox ®< 16 were added after 8 and 10 h. The reaction was stopped after 24 h and cooled to room temperature. The polyacrylate was then blended with the crosslinker Uvacure ®< 1500, diluted with acetone to a solids content of 30%, and then coated and dried in the same way as for PA 1. The application rate was 50 g / m 2< .Molar masses by GPC (Measurement Method A3): M n = 24,500 g / mol; M w = 871,000 g / mol. K value: 48.2. Polyacrylate pressure sensitive adhesive 4 (PA4):

[0117] A 100 L glass reactor conventional for radical polymerizations was charged with 3.2 kg of acrylic acid, 8.0 kg of BA, 28.8 kg of IDA, and 26.7 kg of acetone / isopropanol (94:6). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 30 g of Vazo ®< 67 were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at a constant external temperature. After 1 h of reaction time, another 30 g of Vazo ®< 67 were added. After 4 and 8 h, the mixture was diluted with 10.0 kg of acetone / isopropanol (94:6). To reduce the residual initiators, 90 g of Perkadox ®< 16 were added after 8 and 10 h. The reaction was stopped after 24 h and cooled to room temperature. The polyacrylate was then blended with the crosslinker Uvacure ®< 1500, diluted with acetone to a solids content of 30%, and then coated and dried in the same way as for PA 1. The application rate was 50 g / m 2< .Molar masses by GPC (Measurement Method A3): M n = 35,000 g / mol; M w = 1,020,000 g / mol. K value: 52.9. Comparative example polyacrylate pressure sensitive adhesive 5 (PA5, monomer EHA):

[0118] A 100 L glass reactor conventional for radical polymerizations was charged with 4.0 kg of acrylic acid, 12.0 kg of BA, 24.0 kg of EHA, and 26.7 kg of acetone / petrol 60 / 95 (1:1). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 30 g of AIBN were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at a constant external temperature. After a reaction time of 1 h, another 30 g of AIBN were added. After 4 and 8 h, the mixture was diluted with 10.0 kg of acetone / petrol 60 / 95 (1:1) each time. To reduce the residual initiators, 90 g of Perkadox ®< 16 were added after 8 and 10 h. The reaction was stopped after 24 h and cooled to room temperature. The polyacrylate was then blended with the crosslinker Uvacure ®< 1500, diluted with acetone to a solids content of 30%, and then coated and dried in the same way as for PA 1. The application rate was 50 g / m 2< .Molar masses by GPC (Measurement Method A3): M n = 26,800 g / mol; M w = 809,000 g / mol. K value: 46.3. Comparative example of polyacrylate pressure sensitive adhesive 6 (PA6, monomers PHA and IBOA (cyclic monomer)):

[0119] A 100 L glass reactor conventional for radical polymerizations was charged with 2.4 kg of acrylic acid, 12.0 kg of isobornyl acrylate (IBOA), 25.6 kg of PHA, and 26.7 kg of acetone / petrol 60 / 95 (1:1). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 30 g of AIBN were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at a constant external temperature. After a reaction time of 1 h, another 30 g of AIBN were added. After 4 and 8 h, the mixture was diluted with 10.0 kg of acetone / petrol 60 / 95 (1:1) mixture each time. To reduce the residual initiators, 90 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate were added after 8 and 10 h. The reaction was stopped after 24 h and cooled to room temperature.The polyacrylate was then blended with the crosslinker Uvacure®< 1500, diluted with acetone to a solids content of 30%, and then coated and dried as described for PA 1. The coating weight was 50 g / m 2< . Molar masses by GPC (Measurement Method A3): M n = 24,800 g / mol; M w = 980,000 g / mol. K value: 50.1. Comparison example_Polyacrylate pressure sensitive adhesive 7 (PA7, Monomer iC17A) :

[0120] A 100 L glass reactor conventional for radical polymerizations was charged with 11.0 kg of acrylic acid, 27.0 kg of BA, 62.0 kg of heptadecanyl acrylate (iC17A), and 72.4 kg of acetone / isopropanol (94:6). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 50 g of Vazo ®< 67 were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at this constant external temperature. After a reaction time of 1 h, another 50 g of Vazo ®< 67 were added. After 3 h, the mixture was diluted with 20 kg of acetone / isopropanol (94:6), and after 6 h with 10.0 kg of acetone / isopropanol (94:6). To reduce the residual initiators, 0.15 kg of Perkadox ®< 16 was added after 5.5 and 7 h. The reaction was stopped after 24 h and cooled to room temperature.The polyacrylate was then blended with the crosslinker Uvacure® 1500, diluted with acetone to a solids content of 30%, and then coated and dried in the same way as for PA 1. The coating application rate was 50 g / m². (Coating speed 2.5 m / min, drying tunnel 15 m, temperatures zone 1: 40 °C, zone 2: 70 °C, zone 3: 95 °C, zone 4: 105 °C) The coating application rate was 50 g / m². Molar masses by GPC (measurement method A3): M n = 27,000 g / mol; M w = 990,000 g / mol. K value: 50.1.

[0121] To measure the adhesive properties of the pressure-sensitive adhesives, the PA1 - PA7 compounds specified in the examples were first tested without the polyacrylate foam carrier, both with the crosslinker Uvacure®< 1500 and, in a comparative example, with a glycidyl-functionalized crosslinker (Erisys GA-240). The results in Table 1 show that both Examples B1 - B5 of the inventive pressure-sensitive adhesives PA1 - PA4 and Comparative Examples VB6 - VB9 of the comparative pressure-sensitive adhesives PA5 - PA7 are highly cohesive compounds with moderate bond strength to steel. Crosslinking of the pressure-sensitive adhesive PA1 (Ex. 5) using a glycidylamine also shows good results. Table 1: Examples B1 - B5 and comparative examples VB6 - VB10 - Adhesive data of the pressure-sensitive adhesives e.g. PA Crosslinker [wt.%] Adhesive strength steel [N / cm] Adhesive strength PE [N / cm] SSZ, 10 N, 23°C [min] SSZ, 10 N, 70°C [min] MSW max [µm] elastic content [%] B1 PA1 Uvacure, 0.18 5,7 0,9 > 10.000 1.180 532 92 B2 PA1 Uvacure, 0.22 5,4 0,8 > 10.000 2.500 420 93 B3 PA2 Uvacure, 0.20 5,8 1,0 > 10.000 2.200 470 95 B4 PA3 Uvacure, 0.20 6,3 0,9 > 10.000 2.510 416 97 B5 PA1 Erisys, 0.075 5,1 0,8 > 10.000 2.900 120 95 B6 PA4 Uvacure, 0.20 6,3 0,8 > 10.000 1.750 450 92 VB7 PA5 Uvacure, 0.18 4,9 1,0 > 10.000 440 297 97 VB8 PA5 Uvacure, 0.22 5,2 0,8 > 10.000 2.200 350 94 VB9 PA6 Uvacure, 0.20 5,4 1,2 > 10.000 3.100 420 89 VB10 PA7 Uvacure, 0.20 2,8 1,5 > 10.000 25 390 91 Adhesive strength steel and PE = measurement method H1, SSZ = shear strength at 23° and 70°C = measurement method H2, MSW = micro shear test = measurement method H3, elastic component = elastic component II Production of the starting polymers for the polyacrylate foam VT and the pressure-sensitive adhesive tape examples MT1 to MT10

[0122] The following describes the preparation of the starting polymer, which was produced conventionally via free radical polymerization in solution. Base polymer P

[0123] A reactor conventional for radical polymerizations was charged with 30 kg of EHA, 67 kg of BA, 3 kg of acrylic acid, and 66 kg of acetone / isopropanol (96:4). After 45 minutes of nitrogen gas flow with stirring, the reactor was heated to 58 °C, and 50 g of Vazo ®< 67 were added. The external heating bath was then heated to 75 °C, and the reaction was carried out at a constant external temperature. After 1 h, another 50 g of Vazo ®< 67 were added, and after 4 h, the reaction mixture was diluted with 20 kg of acetone / isopropanol (96:4). After 5 and 7 h, the reaction mixture was reinitiated with 150 g of Perkadox ®< 16, followed by dilution with 23 kg of acetone / isopropanol (96:4). After a reaction time of 22 h, the polymerization was stopped and the mixture was cooled to room temperature. The polyacrylate has a K value of 75.1, a solids content of 50.2%, and average molecular weights of M n = 91,900 g / mol and M w = 1,480,000 g / mol. Method 1: Concentration / Production the hot melt adhesive:

[0124] The base polymer P was largely freed of solvent using a single-screw extruder (concentration extruder, Berstorff GmbH, Germany) (residual solvent content ≤ 0.3 wt%). The parameters for concentrating the base polymer were as follows: the screw speed was 150 rpm, the motor current was 15 A, and a liquid throughput of 58.0 kg / h was achieved. For concentration, a vacuum was applied to three different domes. The negative pressures were between 20 mbar and 300 mbar in each case. The outlet temperature of the concentrated hot melt P was approximately 115 °C. The solids content after this concentration step was 99.8%. Method 2: Production the adhesive tapes according to the invention, blended with the crosslinker-accelerator system for thermal crosslinking and coating

[0125] The foaming took place in a test facility, which is similar to the one shown in Fig. 3 corresponds.

[0126] The base polymer P was melted in a feed extruder 1 according to process 1 and conveyed as a polymer melt via a heatable hose 11 into a planetary roller extruder 2 (PWE) from ENTEX (Bochum, Germany). Specifically, a PWE with four independently heatable modules T1, T2, T3, and T4 was used. Additional additives or fillers, such as color pastes, could be added via the metering opening 22. The crosslinker was added at point 23. All components were mixed to form a homogeneous polymer melt.

[0127] Using a melt pump 24a and a heatable hose 24b, the polymer melt was transferred into a twin-screw extruder 3 (BERSTORFF) (input position 33). The accelerator component was added at position 34. The entire mixture was then freed of all gas inclusions in a vacuum dome V at a pressure of 175 mbar. A blister B was located on the screw downstream of the vacuum zone, which enabled pressure to build up in the subsequent segment S. By appropriately controlling the extruder speed and the melt pump 37a, a pressure of greater than 8 bar was built up in the segment S between blister B and melt pump 37a. The microballoon mixture (microballoons embedded in the dispersing agent according to the specifications in the test series) was added at metering point 35 and homogeneously incorporated into the premix using a mixing element. The resulting melt mixture was transferred to a nozzle 5.

[0128] After leaving nozzle 5, i.e., after the pressure drop, the incorporated microballoons expanded, resulting in low-shear cooling of the polymer mass. A foamed carrier material was formed. This was then coated on both sides with the pressure-sensitive adhesives listed below, each of which was applied to a release liner that can be reused after removal (process liner). The resulting three-layer composite was formed into a web using a roll calender 4.

[0129] To improve the anchoring of the pressure-sensitive adhesives from Examples B 1-10 to the molded polyacrylate foam, both the pressure-sensitive adhesives and the foam were pretreated with corona treatment (corona treatment system from Vitaphone, Denmark, 70 W min / m 2 ). This treatment led to improved chemical bonding to the polyacrylate foam carrier layer after the three-layer composite was produced.

[0130] The web speed during the coating process was 30 m / min. After leaving the roll gap, one release liner was removed and the finished three-layer product was wound up with the remaining second release liner. Table 2: Polyacrylate foam VT Example VT Components Base polymer P [Wt.%] 97,8 Expancel 051 DU 40 1,5 Polypox R16 0,139 IPDA 0,144 Reofos RDP 0,41 Construction thickness [µm] 902 density [kg / m 3 ] 749 Adhesive properties SSZ [min] RT 20 N [min] 1874 70°C 10 N 1282 Adhesive strength steel [N / cm] immediately [N / cm] 24,5 A 3d 33,4 A 14d 35,1 A Density: Measurement method A4, Adhesive strength: Measurement method H2, SSZ (Shear strength): Measurement method M2

[0131] In the following, concrete examples B1 - B6 of the adhesive tapes according to the invention comprising the polyacrylate foam carrier VT with the pressure-sensitive adhesives according to the invention with a double-sided application rate of 50 g / m 2< as well as comparative examples VB7 - VB10 comprising the polyacrylate foam carrier VT with the pressure-sensitive adhesives not according to the invention, likewise with a double-sided application rate of 50 g / m 2<, are presented. Table 3: Adhesive strengths on steel and PE as well as application behaviour of the three-layer pressure-sensitive adhesive tapes MT1 - MT10 comprising the polyacrylate foam carrier VT with a total thickness of 1000 µm e.g. PPE Adhesive strength to steel immediately, [N / cm] Adhesive strength steel 8h, [N / cm] Adhesive strength steel 1d, [N / cm] Adhesive strength steel 3d, [N / cm] Adhesive strength PE 3d, [N / cm] open page covered side open page open page open page open page MT1 B1 11,1 12,0 44 fs 44 fs 45 fs 10,1 MT2 B2 16,3 15,1 44 fs 44 fs 46 fs 10,3 MT3 B3 11,5 10,1 45 fs 45 fs 44 fs 12,6 MT4 B4 15,2 15,9 45 fs 45 fs 45 fs 11,4 MT5 B5 12,0 12,1 44 fs 45 fs 46 fs 10,9 MT6 B6 12,2 11,6 45 fs 45 fs 46 fs 10,5 MT7 VB7 11,9 12,6 38,2 42,6 47 fs 11,2 MT8 VB8 14,1 15,1 40,1 45 fs 45 fs 12,7 MT9 VB9 10,7 9,9 22,9 38,7 45 fs 12,6 MT10 VB10 9,8 9,8 15,4 22,2 25,4 8,0 PSA = pressure-sensitive adhesive, bond strength to steel = measurement method M1 (fs = foam split), shear time = measurement method M2

[0132] The adhesive strength measurements in Table 3 show that the pressure-sensitive adhesive tapes MT1 - MT6 according to the invention apply to steel significantly more quickly and reach their maximum adhesive strength, or rather, the polyacrylate foam carrier splits more quickly. One notable example is pressure-sensitive adhesive VB9 in Example MT9, which, in addition to the PHA monomer used according to the invention, uses a cyclic acrylate with a high Tg instead of a linear monomer. This shows that the polymer takes significantly longer to apply to the substrate. Furthermore, pressure-sensitive adhesive VB10 is noticeable; its adhesive strength to steel in combination with the polyacrylate foam carrier is significantly lower even after three days. With the exception of the last-mentioned example, all pressure-sensitive adhesive tapes exhibit comparable adhesive strengths to PE. Furthermore, the influence of the crosslinker is evident in Example MT5.The use of a glycidyl-functionalized instead of an epoxycyclohexyl-functionalized crosslinker results in a slower take-up behavior.

[0133] Table 4 lists the bond strengths on the different low-energy automotive paints UreGloss, CeramiClear5 (CC5) and VW2K after three days of application. Table 4: Adhesive strengths on low-energy varnishes of the three-layer pressure-sensitive adhesive tapes MT1 - MT10 comprising the polyacrylate foam carrier VT with a total thickness of 1000 µm e.g. PPE Adhesive strength UreGloss 3d, [N / cm] Adhesive strength CC5 3d, [N / cm] Adhesive strength VW2K 3d, [N / cm] open page open page open page MT1 B1 16,6 23,8 44 fs MT2 B2 16,9 24,7 46 fs MT3 B3 19,1 25,9 46 fs MT4 B4 16,7 24,0 45 fs MT5 B5 16,1 21,5 44 fs MT6 B6 19,2 24,3 45 fs MT7 VB7 14,3 22,8 38,5 MT8 VB8 14,6 25,1 34,2 MT9 VB9 12,2 21,5 31,7 MT10 VB10 10,1 12,5 20,4

[0134] Here, too, it can be seen that the pressure-sensitive adhesive tapes comprising the pressure-sensitive adhesives according to the invention produce better results in comparison. Table 5: Rigid Rigid Wet-out test of the three-layer pressure-sensitive adhesive tapes MT1 - MT10 comprising the polyacrylate foam carrier VT with a total thickness of 1000 µm e.g. Wetting 0 µm, 1 kg, immediate, [%] Wetting 100 µm, 4 kg, immediate, [%] Wetting 100 µm, 4 kg, 1d, [%] Wetting 100 µm, 4 kg, 3d, [%] Dewetting 100 µm, 4 kg, difference 3d - immediate, [%] open page open page open page open page open page MT1 98 93 90 69 -24 MT2 96 90 85 73 -17 MT3 97 87 82 72 -15 MT4 98 90 86 68 -22 MT5 98 85 55 42 -33 MT6 97 85 79 69 -16 MT7 98 86 53 12 -74 MT8 97 88 49 9 -77 MT9 96 69 42 22 -47 MT10 98 82 12 6 -76

[0135] The difference between the pressure-sensitive adhesive tapes according to the invention and the comparative examples is best demonstrated in the rigid-rigid wet-out test. While wetting is very good in all examples when bonded without a step, it is evident that when using a step height of 100 µm, immediate wetting is only good when using the pressure-sensitive adhesives MT1 - MT6 according to the invention. The influence of the monomers, in particular the cyclic acrylate in example MT9 and the crosslinker (MT5), is clearly visible here. Furthermore, it is evident that dewetting, expressed here as the difference between wetting after three days and immediately after (the smaller the difference, the lower the dewetting), is also lowest in the case of the inventive examples.

Claims

1. Pressure-sensitive adhesive comprising at least 50 wt%, based on the total weight of the pressure-sensitive adhesive, of at least one polymer A which may be derived from the following monomer composition: a1) 55 to 75 wt% of 2-propylheptyl acrylate (PHA) and / or isodecyl acrylate; a2) 20 to 40 wt% of at least one (meth)acrylic acid ester for which the alcohol component is based on a linear C1-C18 alcohol; a3) 5 to 15 wt% of acrylic acid, except for a polymer obtained in the following steps: - charging a 300 I reactor conventional for radical polymerizations with 62.0 kg of 2-propylheptyl acrylate, 27.0 kg of butyl acrylate and 11.0 kg of acrylic acid and also 72.4 kg of acetone / isopropanol (94:6); - passing nitrogen gas through for 45 minutes with stirring; - heating the reactor to 58°C; - adding 50 g of 2,2'-azobis(2-methylbutyronitrile); - heating the external heating bath to 75°C and carrying out the reaction constantly at this external temperature; - adding 50 g of 2,2'-azobis(2-methylbutyronitrile) after 1 h reaction time; - diluting with 20 kg of acetone / isopropanol (94:6) after 3 h and with 10 kg of acetone / isopropanol (94:6) after 6 h; - adding 0.15 kg of bis(4-tert-butylcyclohexyl) peroxydicarbonate after 5.5 and after 7 h respectively to reduce the residual initiators; - discontinuing the reaction after 24 h reaction time and cooling down to room temperature.

2. Pressure-sensitive adhesive according to Claim 1, characterized in that the pressure-sensitive adhesive is thermally crosslinked by at least one epoxycyclohexyl derivative.

3. Pressure-sensitive adhesive according to at least one of the preceding claims, characterized in that the pressure-sensitive adhesive contains no peel adhesion-boosting resin.

4. Pressure-sensitive adhesive according to at least one of the preceding claims, characterized in that the polymer A has a weight-average molecular weight Mw (gel permeation chromatography, PMMA standards) of at least 500 000 g / mol.

5. Pressure-sensitive adhesive according to at least one of the preceding claims, characterized in that the polymer A has a weight-average molecular weight Mw (gel permeation chromatography, PMMA standards) of not more than 1 700 000 g / mol.

6. Adhesive tape comprising a foamed carrier and a pressure-sensitive adhesive according to at least one of the preceding claims.

7. Adhesive tape according to Claim 6, characterized in that the foamed carrier comprises a syntactic polymer foam.

8. Adhesive tape according to Claim 7, characterized in that the syntactic polymer foam contains at least 50 wt% , based on the total weight of the foam, of one or more poly(meth)acrylates.

9. Adhesive tape according to at least one of Claims 6 to 8, characterized in that the pressure-sensitive adhesive is laminated on at least one side of the foamed carrier.

10. Adhesive tape according to at least one of Claims 6 to 9, characterized in that the foamed carrier contains at least 50 wt%, based on the total weight of the foam, at least one poly(meth)acrylate B which may be derived from the following monomer composition: b1) 65 to 97 wt% of ethylhexyl acrylate and / or butyl acrylate, b2) 0 to 30 wt% of methyl acrylate, b3) 3 to 15 wt% of acrylic acid.

11. Adhesive tape according to at least one of Claims 6 to 10, characterized in that the foamed carrier is thermally crosslinked.

12. Adhesive tape according to at least one of Claims 6 to 11, characterized in that on both sides of the foamed carrier there is a pressure-sensitive adhesive according to at least one of Claims 1 to 6.