Carrier made of foamed thermoplastic polyurethane and adhesive tape comprising the foamed carrier

Abstract

The present invention relates to a carrier for an adhesive tape comprising at least one layer based on foamed thermoplastic polyurethane, which is characterized by its particular compression strength, an adhesive tape comprising the carrier, a process for producing the adhesive tape and its use.

Description

The present invention relates to a backing for an adhesive tape which comprises at least one layer based on foamed thermoplastic polyurethane and is distinguished by its particular compressive strength, to an adhesive tape comprising the backing, to a process for producing the adhesive tape and to its use.Adhesive tapes have long been known and enjoying great popularity without interruption. Their use goes beyond their use in household and office applications and extends over the construction industry to the automobile and electrical industries. In particular in the electrical industry, adhesive tapes are being used more and more frequently for bonding electronic devices. However, this involves the difficulty that a balance must be found between sufficient adhesive force and redetachability of the adhesive tape in order to avoid damage to the partially sensitive components during redetachment of the adhesive tape.WO 2015 / 135134 A1 describes an stretch-releasable adhesive tape comprising a carrier and a first layer of a pressure-sensitive adhesive applied to at least one surface of the carrier, the adhesive tape having a thickness of between 0.05 and 0.1 mm and a longitudinal elongation of 850 to 2200%, wherein the adhesive tape is firmly bonded to a substrate and can be released therefrom again by being able to be released from the surface of the substrate at an angle of 90° or more without tearing and without leaving a substantial residue on the substrate, wherein the pressure-sensitive adhesive is formed from an acrylate copolymer containing terminal polyurethane functional groups. The adhesive tape is also intended to be usable in electronic devices.EP 3 757 157 A1 discloses a formulation comprising at least one aqueous dispersion of an elastomer and expandable or expanded microballoons, and also an adhesive tape comprising a carrier prepared from the dispersion. The foams produced from the dispersion are said to have an impact strength comparable to that of PE foams, in particular those of the tesa ®668- series (see https: / / www.tesa.com / en / industry / electronics / solutions / pe-foam tapes). Particularly good results are to be achieved with a formulation which comprises a mixture of two polyether-based polyurethane dispersions.In addition to the adhesive components of an adhesive tape, the properties of an adhesive tape are also determined to a high degree by the non-adhesive constituents. Particularly with regard to the mechanical properties, high requirements are generally imposed on the backing of the adhesive tape which not only has to be compatible with the PSA but is also intended to impart the necessary strength and stability to the latter.Here, particularly when applying the adhesive tapes in sensitive devices, the difficulty arises of providing a carrier which has corresponding damping properties in order to protect the installed components from vibrations.Adhesive tapes with a carrier made of a polyolefin foam are available in a wide variety of designs and densities and are known for their good damping properties. However, they have the disadvantage that they have only a low strength, so that they are generally not suitable, for example, for removable products.Against this background, the present invention provides its object in the provision of a carrier for adhesive tapes, in particular removable adhesive tapes, which has a corresponding profile of properties in order to meet the requirements mentioned and which is distinguished in particular by good damping properties. This object is achieved according to the invention by a carrier according to the main claim. Preferred developments of the carrier according to the invention are set forth in the dependent claims.A first subject of the present invention is therefore a carrier comprising at least one closed-cell layer foamed with microballoons and based on thermoplastic polyurethane, the carrier having a compressive hardness of at least 50% at a maximum force of 140 N / cm 2, preferably at a maximum force of 120 N / cm 2, particularly preferably at a maximum force of 100 N / cm 2 determined in accordance with DIN EN ISO 3386-2 (2010-09).The compressive strength describes the strength of foamed materials and provides information on how much force is required to compress the material in the z-direction from its initial state by a certain percentage. The higher the value, the harder the material.For the production of multilayer structures, it is generally necessary to perform complicated pretreatment in order to generate a sufficiently stable bond between adhesive compositions or outer layers in order thus to withstand high shock loads without failure at the interfaces.Using the microballoons-foamed supports of the invention, these disadvantages can be avoided. High-performance adhesive tapes in multilayer construction can be produced without complicated surface pretreatment, which at the same time resist a high shock load and are readily removable again.Furthermore, it has surprisingly been found that the supports according to the invention have a significantly improved softness compared to conventional polyethylene-based supports, as a result of which advantageous damping properties can be achieved.In the context of the present invention, it has surprisingly been found that polyurethane foam as carrier material, in combination with the specified compression, provides very good damping capacity and is thus suitable in particular for the production of electronic components.Without being bound to a particular theory, it is assumed that the observed damping properties of the carrier according to the invention can be further improved by a corresponding density of the carrier. In a preferred embodiment, the carrier therefore has a density of 300 to 1200 kg / m 3, preferably 400 to 900 kg / m 3, particularly preferably 500 to 800 kg / m 3.The polyurethane used as carrier material is preferably selected from the group consisting of aromatic polyurethanes, aliphatic polyurethanes, polyester-polyol-based polyurethanes, polyether-polyol-based polyurethanes, polycarbonate-based polyurethanes and hybrids and mixtures thereof.The polyurethane may be crosslinked or uncrosslinked.The thickness of the support may vary depending on the application. Thus, in some applications, carriers with a small thickness are preferred, while in other applications, for example as spacers, carriers with a higher thickness are used. In the context of the present invention, the carrier preferably has a thickness of 20 to 2500 μm, particularly preferably 50 to 1000 μm. In certain cases, a thickness of the support of 150 to 1000 μm is preferred.The support according to the invention is distinguished inter alia by its good damping capacity. In this connection, an embodiment is preferred in which the carrier has a breakdown strength of at least 0.3 J, determined by means of the DuPont test.In a first embodiment, the support comprises at least one, preferably exactly one, layer based on thermoplastic polyurethane, which has typically been produced by means of extrusion. Such a layer based on thermoplastic polyurethane typically means a layer whose proportion of thermoplastic polyurethane is at least 50% by weight. The proportion of thermoplastic polyurethane in the layer is preferably at least 90% by weight, in particular the layer consists essentially of thermoplastic polyurethane.The thermoplastic polyurethane of the at least one carrier layer is preferably based on polyester polyol, but alternatively may also be based on polyether polyol, such as poly-THF as polyol. The polyester polyol-based or polyether polyol-based thermoplastic polyurethane is typically aliphatic polyester polyol-based or aliphatic polyether polyol-based thermoplastic polyurethane.The polyurethane used may have two or more glass transition temperatures, one of which is preferably between -20°C and 40°C and the other is preferably between 60°C and 110°C. The glass transition temperature may be determined, for example, by means of DSC according to DIN 53765.The thermoplastic polyurethane typically has a tear strength of over 10 MPa, preferably over 20 MPa. In a further preferred embodiment, the Shore A hardness is between 45 and 95, such as in particular between 60 and 85. In an alternatively preferred embodiment, the Shore A hardness is between 70 and 85.The thermoplastic polyurethane is preferably a reaction product of a reaction mixture containing at least one diisocyanate, at least one polyester polyol (or polyether polyol), and optionally at least one chain extender, wherein the polyester polyol or polyether polyol typically has a melting temperature of at least 30°C, such as at least 100°C or at least 200°C.Chain extenders may be, for example, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, propylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, hydroquinone dihydroxyethyl ether, ethanolamine, N-phenyldiethanolamine or m-phenylenediamine. Chain extenders are low molecular weight isocyanate-reactive difunctional compounds.Monofunctional isocyanate-reactive materials such as monools may also be used. They serve as chain terminators and can thus be used to control the chain length.The proportion of diisocyanate in the reaction mixture is preferably 0.5 to 47 wt%, more preferably 1 to 40 wt%, and particularly 10 to 25 wt%. The amount of diisocyanate in the reaction mixture can also be expressed as from NCO to OH groups (isocyanate index). An isocyanate index is generally understood to refer to the ratio of the equivalent amount of the isocyanate functional groups used to the equivalent amount of the hydroxyl functional groups. The isocyanate index of the reaction mixture is preferably in a range of from 0.99 to 1.20, more preferably from 1.00 to 1.10.Preferably, the diisocyanate is a diisocyanate having the structure of formula I O=C=N-R-N=C=O (formula I) wherein R is selected from substituted or unsubstituted (C 1- C 40)- alkylene, (C 2- C 40)- alkenylene, (C 4- C 20)- arylene, (C 4- C 20)- arylene-(C 1- C 40)- alkylene-(C 4- C 20)- arylene, (C 4- C 20)- cycloalkylene, and (C 4- C 20)- aralkylene. In further examples, the diisocyanate is selected from dicyclohexylmethane 4,4'-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, m-xylylene diisocyanate, toluylene 2,4-diisocyanate, toluene 2,4-diisocyanate, toluylene 2,6-diisocyanate, poly(hexamethylene diisocyanate), 1,4-cyclohexylene diisocyanate, 4-chloro-6-methyl-1,3-phenylene diisocyanate, hexamethylene diisocyanate, diphenylmethane 4,4'-diisocyanate, 1,4-diisocyanatobutane, 1,8-diisocyanatooctane, 2,6-toluene diisocyanate, 2,5-toluene diisocyanate, 2,4-toluene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, methylenebis(o-chlorophenyl diisocyanate), methylenediphenylene 4,4'-diisocyanate, (4,4'-diisocyanato-3,3',5,5'-tetraethyl)diphenylmethane, 4,4'-diisocyanato-3,3'-dimethoxy-biphenyl(o-dianisidine diisocyanate), 5-chloro-2,4-toluene diisocyanate, 1-chloromethyl-2,4-diisocyanatobenzene, tetramethyl-m-xylylene diisocyanate, 1,6-diisocyanatohexane, 1,12-diisocyanatododecane, 2-methyl-1,5-diisocyanatopentane, methylenedicyclohexylene-4,4'-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 2,2,4-trimethylhexyl diisocyanate or a mixture thereof.Diphenylmethane-4,4'-diisocyanate (MDI), hexane diisocyanate (HDI), isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HMDI) is particularly preferably used as diisocyanate.The proportion of polyester polyol or polyether polyol in the reaction mixture is preferably in the range of 43% by weight to 70% by weight, more preferably in the range of 50% by weight to 60% by weight.The polyester polyol preferably contains two hydroxyl groups, so that the polyester polyol is a polyester diol. The polyester polyol may also contain any suitable number of hydroxyl groups, depending on the concentration of this polyester polyol and the isocyanate index, it may also contain a different number of polyester polyols.The polyester polyol may also be a polycaprolactone polyol.In examples where the polyester polyol is prepared according to a condensation reaction, the reaction may take place between one or more carboxylic acids and one or more polyols. Examples of suitable carboxylic acids include carboxylic acids of formula IIa (dicarboxylic acids) and IIb (hydroxycarboxylic acids) having the structures: In the formula IIa, R 1 is typically selected from substituted or unsubstituted (C 1- C 40)- alkylene, (C 2- C 40)- alkenylene, (C 4- C 20)- arylene, (C 4- C 20)- cycloalkylene and (C 4- C20)aralkylene. In formula IIb, R 2 is typically selected from substituted or unsubstituted (C 1- C 40)- alkylene, (C 2- C 40)- alkenylene, (C 4- C 20)- cycloalkylene and (C 4- C 20)- aralkylene.Examples of suitable carboxylic acids include lactic acid (2-hydroxypropanoic acid), succinic acid (butanedioic acid), 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, terephthalic acid (benzene-1,4-dicarboxylic acid), naphthalenedicarboxylic acid, 4-hydroxybenzoic acid, 6-hydroxynaphthalane-2-carboxylic acid, oxalic acid, malonic acid (propanedioic acid), adipic acid (hexanedioic acid), pimelic acid (heptanedioic acid), ethonic acid, suberic acid (octanedioic acid), azelaic acid (nonanedioic acid), sebacic acid (decanedioic acid), glutaric acid (pentanedioic acid), dodecanedioic acid, brassylic acid, thapsinic acid, maleic acid, fumaric acid, glutaconic acid, 2-decenoic acid, muconic acid, glutinic acid, citraconic acid, Mesaconic acid, itaconic acid, malic acid (2-hydroxybutanedioic acid), aspartic acid (2-aminobutanedioic acid), glutamic acid (2-aminopentanedioic acid), tartaric acid, tartaric acid (2,3-dihydroxybutanedioic acid), diaminopimelic acid, saccharic acid, mesoxalic acid, oxaloacetic acid, acetonicarboxylic acid (3-oxopentanedioic acid), arbinaric acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid or a mixture thereof. Particular preference is given to adipic acid and caprolactone.An example of a suitable polyol includes a polyol of formula III having the structure: HO-R 2- OH (formula III)In formula III, R 2 is selected from substituted or unsubstituted (C 1- C 40)- alkylene, (C 2- C 40)- alkenylene, (C 4- C 20)- arylene, (C 1- C 40)- acylene, (C 4- C20) cycloalkylene, (C4-C20)aralkylene and (C1-C40)alkoxylene.For example, the diol may have a number average molecular weight in a range of 30 g / mol to 600 g / mol, preferably 50 g / mol to 350 g / mol. The diol component may contain any suitable number of carbons. For example, the diol may have a number average number of 2 carbons to 500 carbons, preferably 3 carbons to 140 carbons. Examples of suitable diols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, or a mixture thereof.Particularly preferred polyester polyols are accordingly polyalkylene adipates.For film production, the blown film process of several layers is conventionally mainly used. Here, a PE layer (i.e. polyethylene layer) and the actual TPU layer are produced in the blown film process as coextruded film (i.e. the PE layer functions as support carrier which gives the extrudate the necessary mechanical stability). In use, the PE support is thus removed before or during the production of the adhesive tape, i.e. constitutes a temporary carrier. However, numerous additives such as so-called antiblocking agents (e.g. silicate particles) are necessary for producing a corresponding blown film, in order, for example, to ensure controlled redetachment of the support carrier, and sliding waxes are necessary as process auxiliaries. Both facts) lead to a negative influence on the mechanical properties. Both the silicate particles in the film (=defects) and the crystalline superstructure (=hard non-flexible domains) lead to a lower extensibility and, above all, to a higher tendency to tear during use, i.e. during extension stretching. The waxes, by migration of the waxes to the PSA surface, i.e. surface of the PSA, additionally lead to problems with bond strength reduction and to difficulties in anchoring the PSA to the film. An advantage of high extensibility and low tear propensity is additionally a high molecular weight of the PU polymer for increasing the toughness of the film.Therefore, the TPU-based carrier layer is preferably free of additives such as antiblocking agents and waxes. In addition, the polyurethane preferably does not have a crystalline superstructure, as manifested in a DSC peak >20° C.In a preferred embodiment, the polyurethane used to produce the carrier is crosslinked.Cross-linkers can react in essentially two different ways: by reaction with a polymer or by reaction with themselves to form a so-called interpenetrating network, creating a much denser network and thus improving many properties such as strength, abrasion resistance, hydrolysis and chemical resistance.Preferred crosslinkers in the context of the present invention are, in particular, crosslinkers based on aziridine, carbodiimide (polycarbodiimide), melamine, radical-forming substances such as organic peroxides, sulfur and isocyanate. In a preferred embodiment, the crosslinking agent is an isocyanate, preferably a blocked polyisocyanate, in particular a blocked aliphatic polyisocyanate.Polyisocyanates can react with functional groups such as amino or hydroxyl groups. The polyfunctionality of this type of crosslinking agent produces a 3D-crosslinked network. Polyisocyanates also react with water, which in turn causes reaction of the polyisocyanate molecules with itself and results in a network consisting of a combination of a classical 3D polymer crosslinked network and an interpenetrating network caused by the reactivity of several polyisocyanate molecules with themselves.In the case of an isocyanate cross-linking agent, it is preferably obtained from a dispersion comprising a polyisocyanate, a blocking agent for isocyanate groups and water. In a preferred embodiment, the dispersion for obtaining the crosslinking agent further comprises a polyamine, preferably one having at least one carboxyl and / or carboxylate group.Polyisocyanates are considered here to be compounds which have NCO groups. The polyisocyanate may have a number average molecular weight of from 140 to 1500 g / mol, and preferably from 168 to 700 g / mol. According to a preferred embodiment of the invention, it is provided that the polyisocyanate has an isocyanate functionality of >2 and <6, preferably >3 and <5 and particularly preferably >3 and <4.The polyisocyanate preferably has an NCO group content of from 15 to 30% by weight, preferably from 18 to 25% by weight and particularly preferably from 20 to 24% by weight, based on the number-average molar weight of the polyisocyanate.Suitable polyisocyanates are, for example, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-diisocyanatodicyclohexylmethane (Hi2MDI), 1,4-butane diisocyanate, hexahydroisocyanatotoluene, 1,3-bishydroxymethylcyclohexane, hexahydroisocyanatoxylene, nonane triisocyanate. Particular preference is given to the use of isophorone diisocyanate, hexamethylene diisocyanate and / or 4,4-diisocyanatodicyclohexylmethane.Aliphatic polyisocyanates, preferably hexamethylene diisocyanate and particularly preferably trimers of hexamethylene diisocyanate, are used as particularly preferred polyisocyanates. It is also advantageous if aqueous blocked polyurethaneurea dispersion is exclusively anionically hydrophilized. This means that the polyurethaneurea dispersion does not hydrophilize cationically and / or non-ionically, i.e. does not have any corresponding groups.In the present case, a blocking agent is understood to mean compounds which react with an isocyanate group and can be split off from it again under defined conditions, for example thermally. This process is referred to as deblocking. Within the scope of the present invention, a low deblocking temperature has proven to be particularly advantageous. Therefore, an embodiment in which the deblocking temperature is less than 130° C. is preferred.Polycarbodiimides selectively react with carboxylic acid groups in polymer chains. This type of crosslinking produces a classic 3D polymer-crosslinked network. Compared with polyisocyanates, polycarbodiimides are less sensitive to water and thus achieve longer pot lives.Melamine resins are very effective crosslinkers on account of their high reactivity. They require smaller amounts of addition than isocyanates or carbodiimes. Melamine resins are often used in conjunction with hydroxl-functional polymer resins to form very hard networks, but may also react with acid groups. Melamine resins require very high crosslinking temperatures, which can be reduced by the addition of catalysts.Polyaziridines are sometimes the most reactive crosslinkers and are thus highly efficient. Polyaziridines selectively react with carboxylic acid groups in polymer chains. This type of crosslinking produces classical 3D polymer crosslinked networks. Because of the lower molecular weight, a much smaller proportion is required compared with polyisocyanates and polycarbodiimides.The peroxidic crosslinking achieves a high degree of crosslinking with favorable processing safety and broad applicability. However, the vulcanization times are very long.For the crosslinking with sulfur, it is usually necessary to add vulcanization accelerators in order to prevent degradation phenomena at the temperatures used for the crosslinking. The elasticity and cold resistance of the vulcanisates are usually lower.Foaming:The backing comprises a polyurethane layer foamed by microballoons."Microballoons" are understood to mean hollow microspheres which are elastic and thus expandable in their basic state and have a thermoplastic polymer shell. These balls are filled with low boiling liquids or liquefied gas. The casing material used is, in particular, polyacrylonitrile, PVDC, PVC or polyacrylate. Suitable low-boiling liquids are, in particular, hydrocarbons of the lower alkanes, for example isobutane or isopentane, which are enclosed as liquefied gas under pressure in the polymer shell.By acting on the microballoons, in particular by action of heat, the outer polymer shell softens. At the same time, the liquid propellant gas located in the casing changes to its gaseous state. In the process, the microballoons irreversibly expand and expand three-dimensionally. The expansion is completed when the internal and external pressures equalize. Since the polymeric shell is retained, a closed-cell foam is thus obtained.A large number of microsphere types are commercially available, which differentiate substantially over their size, preferably 5 to 45 μm diameter in the unexpanded state, and their starting temperatures required for expansion, preferably 75 to 220° C. An example of commercially available microballoons is the Expancel® DU types (DU=dry unexpanded) from Nouryon.Unexpanded microballoons types are also obtainable as aqueous dispersion having a solids or microsphere content of from about 40 to 45% by weight, and also as polymer-bonded microballoons (masterbatches), for example in ethyl vinyl acetate having a microsphere concentration of about 50% by weight.According to the invention, the average diameter of the voids formed by the microballoons in the foamed carrier is preferably from 10 to 200 μm, more preferably from 15 to 200 μm. Since the diameters of the voids formed by the microballoons in the foamed carrier are measured in this case, the diameters are those diameters of the voids formed by the expanded microballoons. The mean diameter here means the arithmetic mean of the diameters of the voids formed by the microballoons in the PSA layer. The average diameter of the voids formed by the microballoons can be determined by means of a scanning electron microscope (SEM). The diameters of the microballoons to be seen on the images are determined graphically in such a way that the maximum extent thereof in any desired (two-dimensional) direction is taken from the SEM images for each individual microballoons and is regarded as the diameter thereof.According to a preferred embodiment of the invention, the proportion of microballoons in the polyurethane is between greater than 0% by weight and 10% by weight, in particular between 0.25% by weight and 5% by weight, very particularly between 0.5% by weight and 4% by weight, based in each case on the total composition of the carrier. The data relates to unexpanded microballoons.In addition to expandable hollow microspheres, the polyurethane may additionally also comprise nonexpandable hollow microspheres. It is only decisive that almost all gas-containing caverns are closed by a permanently dense membrane, regardless of whether this membrane now consists of an elastic and thermoplastically stretchable polymer mixture or of elastic glass and-in the range of temperatures possible in plastic processing-non-thermoplastic glass.Also suitable-independently selected from other additives-are polymer pellets, hollow glass pellets, solid glass pellets, hollow ceramic pellets, solid ceramic pellets and / or solid carbon pellets ("carbon microballoon").In addition, the polyurethane layer may be foamed by adding a physical foaming agent. Thus, the starting mixture can be foamed, for example, in the presence of a gas such as air, nitrogen or a noble gas such as helium, neon or argon. Blowing agents can be used individually or as a mixture of different blowing agents. Propellants may be selected from a wide variety of materials including hydrocarbons, ethers and esters and the like. Typical physical propellants have a boiling point in the range of -50°C to +100 °C, and preferably from -50°C to +50°C. Preferred physical blowing agents include hydrocarbons such as n-pentane, isopentane, and cyclopentane, methylene chloride, or any combinations of the above compounds. Such blowing agents can preferably be used in amounts of from 5% by weight to 50% by weight of the reaction mixture, in particular from 10% by weight to 30% by weight of the reaction mixture.It is also possible to additionally use a chemical blowing agent. Chemical blowing agents are substances which only during the processing process, as a result of a chemical reaction-usually initiated by heat supply-break off gas and thus make it possible to produce a foam structure in the polymer. The cause of the gas elimination can be either the thermal decomposition of the blowing agent or a chemical reaction of various substances contained in the blowing agent. The resulting gas is usually N 2, CO 2 or CO.The present invention further provides an adhesive tape comprising the backing of the invention which is coated at least on one side with a pressure-sensitive adhesive.PSAThe foamed polyurethane backing of the invention is compatible with a series of PSAs, preference being given to using PSAs based on vinylaromatic block copolymers, polyacrylates, polyurethanes or combinations thereof.In a preferred embodiment, at least one PSA layer consists of a PSA based on vinylaromatic block copolymers.Preferred vinylaromatic block copolymer is at least one synthetic rubber in the form of a block copolymer having a structure A-B, A-B-A, (A-B) n, ( A-B) n X or (A-B-A) n X, in which• Blocks A independently of one another for a polymer formed by polymerization of vinylaromatics;• B blocks are each independently a polymer formed by polymerization of conjugated dienes having 4 to 18 carbon atoms and / or isobutylene, or a partially or fully hydrogenated derivative of such a polymer;• X for the residue of a coupling reagent or initiator, and• n represents an integer ≥ 2.In particular, all synthetic rubbers of the PSA of the invention are block copolymers having a structure as set out above. The PSA of the invention may therefore also comprise mixtures of various block copolymers having a structure as above.Suitable block copolymers include one or more rubbery blocks B (soft blocks) and one or more glassy blocks A (hard blocks). More preferably, at least one of the block copolymers is a block copolymer having a structure A-B, A-B-A, (A-B) 3 X or (A-B) 4 X, where A, B and X are as defined above, and where at least one block copolymer comprises at least two hard blocks. Very particularly preferably, the block copolymers are those having a structure A-B, A-B-A, (A-B) 3 X or (A-B) 4 X, where A, B and X are each as defined above. In particular, it is also possible to use a mixture of block copolymers having an A-B, A-B-A, (A-B) 3 X or (A-B) 4 X structure, which preferably comprises at least diblock copolymers A-B and / or triblock copolymers A-B-A.A mixture of diblock and triblock copolymers and (A-B) n or (A-B) n X block copolymers where n is greater than or equal to 3 is also advantageous.The block copolymers resulting from the A and B blocks may contain the same or different B blocks. The block copolymers may have linear A-B-A structures. It is likewise possible to use block copolymers of radial shape and star-shaped and linear multiblock copolymers. A-B diblock copolymers may be present as further components. The aforementioned polymers can be used alone or in a mixture with one another, it not being possible to use A-B diblock copolymers alone.The block A is in particular a vitreous block having a preferred glass transition temperature (T g, DSC) which is above room temperature. The T g of the glassy block is particularly preferably at least 40° C., in particular at least 60° C., very particularly preferably at least 80° C. and very preferably at least 100° C. The proportion of vinylaromatic blocks A in the entirety of the block copolymers is preferably 10 to 40% by weight, particularly preferably 20 to 33% by weight. Vinylaromatics for building up block A preferably comprise styrene and α-methylstyrene. The block A can thus be present as a homo- or copolymer. Most preferably, the block A is a polystyrene.The block B is in particular a rubber-like block or soft block with a preferred T g of less than room temperature. The T g of the soft block is particularly preferably less than 0° C., in particular less than -10° C., for example less than -40° C. and very particularly preferably less than -60° C.Monomer units for constituting block A preferably include styrene, α-methylstyrene and / or other styrene derivatives. The block A can thus be present as a homo- or copolymer. Most preferably, the block A is a polystyrene.Preferred conjugated dienes as monomers for the soft block B are selected in particular from the group consisting of butadiene, isoprene, ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene and dimethylbutadiene and also any desired mixtures of these monomers. The block B can also be present as a homopolymer or as a copolymer. Particularly preferred are the conjugated dienes as monomers for soft block B selected from butadiene and isoprene. For example, the soft block B is a polyisoprene, a polybutadiene or a partially or fully hydrogenated derivative of one of these two polymers, such as especially polybutylene butadiene, or a polymer of a mixture of butadiene and isoprene. Most preferably, the block B is a polybutadiene.A blocks are also referred to in the context of this invention as "hard blocks". B blocks are also called "soft blocks" or "elastomer blocks", respectively. This reflects the selection according to the invention of the blocks according to their glass transition temperatures, preferably at least 25° C., in particular at least 50° C., for A blocks and at most 25° C., in particular at most -25° C., for B blocks.In a preferred embodiment, the proportion of vinylaromatic block copolymers, based on the total PSA, is from 15 to 60% by weight, more preferably from 20 to 50% by weight. Too low a proportion of vinylaromatic block copolymers has the consequence that the cohesion of the PSA is relatively low, and so the tear strength required for stripping is too low. Too high a proportion of vinylaromatic block copolymer in turn has the consequence that the PSA is barely pressure-sensitively adhesive.In an alternatively preferred embodiment, a polyacrylate-based pressure-sensitive adhesive is used.In the present application, the terms "acrylate" and "polyacrylate" are used interchangeably. This is understood to mean in each case a polymer which has resulted from a polymerization of (meth)acrylic acid, an ester thereof or mixtures of the abovementioned monomers, and optionally further copolymerizable monomers. The term (meth)acrylic acid also includes both acrylic acid and methacrylic acid. Typically, the polyacrylates are copolymers.Acrylate-based PSAs based on solvents, based on water or else as hotmelt systems, for example an acrylate hotmelt-based composition, which may have a K value of at least 20, especially greater than 30, obtainable by concentrating a solution of such a composition to give a system processable as hotmelt, are usable in the sense of the invention for the polyacrylate-based PSAs. The concentration can take place in correspondingly equipped vessels or extruders; in particular, in the case of the degassing associated therewith, a degassing extruder is preferred. Such an adhesive is set out in DE 43 13 008 A1, the content of which is hereby incorporated by reference and the content of which forms part of this disclosure and invention. The acrylate-Hotmelt-based adhesive can be chemically crosslinked.An adhesive which is also found to be suitable is a low molecular weight hot melt acrylate adhesive such as acResin® UV from BASF and acrylate dispersion adhesives such as Acronal® available from BASF.In a further embodiment, copolymers of (meth)acrylic acid and esters thereof having 1 to 25 carbon atoms, maleic, fumaric and / or itaconic acid and / or esters thereof, substituted (meth)acrylamides, maleic anhydride and other vinyl compounds such as vinyl esters, in particular vinyl acetate, vinyl alcohols and / or vinyl ethers, are used in PSAs. The residual solvent content should be below 1% by weight.In another preferred embodiment, a pressure-sensitive adhesive is used which comprises a polyacrylate polymer. This is a polymer which is obtainable by free-radical polymerization of acrylic monomers, which are also understood to mean methacrylic monomers, and optionally further copolymerizable monomers.According to the invention, it may be a polyacrylate crosslinkable with epoxide groups. Accordingly, functional monomers crosslinkable with epoxide groups are preferably used as monomers or comonomers; here, monomers having acid groups (especially carboxylic acid, sulfonic acid or phosphonic acid groups) and / or hydroxyl groups and / or acid anhydride groups and / or epoxide groups and / or amine groups are used in particular; monomers containing carboxylic acid groups are preferred. It is particularly advantageous if the polyacrylate comprises copolymerized acrylic acid and / or methacrylic acid. Further monomers which can be used as comonomers for the polyacrylate are, for example, acrylic and / or methacrylic esters having up to 30 carbon atoms, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 double bonds, or mixtures of these monomers.Preference is given to using a polyacrylate which can be recycled to the following monomer composition: i. acrylic ester and / or methacrylic ester of the following formula CH 2= C(R 1)( COOR 2), where R 1= represents H or CH 3 and R 2= represents H or linear, branched or ring-shaped, saturated or unsaturated alkyl radicals having 1 to 30, in particular having 4 to 18, carbon atoms, ii. olefinically unsaturated monomers having functional groups of the type already defined for reactivity with epoxide groups, iii. optionally further acrylates and / or methacrylates and / or olefinically unsaturated monomers which can be copolymerized with component (i).More preferably, for the use of the polyacrylate as pressure-sensitive adhesive, the proportions of the corresponding components (i), (ii) and (iii) are chosen such that the polymerization product has in particular a glass transition temperature of less than or equal to 15° C. (determined by DSC (differential scanning calorimetry) in accordance with DIN 53765 at a heating rate of 10 K / min).For the production of PSAs, it is very advantageous to choose the monomers of component (i) in a proportion of from 45 to 99% by weight, the monomers of component (ii) in a proportion of from 1 to 15% by weight and the monomers of component (iii) in a proportion of from 0 to 40% by weight (the details are based on the monomer mixture for the "base polymer", i.e. without additives to the finished polymer such as resins).The monomers of component (i) are in particular plasticizing and / or nonpolar monomers. Preferably, acrylic monomers are used for the monomers (i) which comprise acrylic and methacrylic esters having alkyl groups consisting of 4 to 18 carbon atoms, preferably 4 to 9 carbon atoms. Examples of such monomers are n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate and the branched isomers thereof, such as, for example, 2-ethylhexyl acrylate or 2-ethylhexyl methacrylate.Preferably, for component (ii), monomers having such functional groups are used that are selected from the following list:hydroxy, carboxy, sulphonic or phosphonic acid groups, acid anhydrides, epoxides, amines.Particularly preferred examples of monomers of component (ii) are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, itaconic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate.Examples of monomers mentioned for component (iii) are: methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butyl acrylate, tert. Butyl acrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, isobornyl methacrylate, t-butylphenyl acrylate, t-butylphenyl methacrylate, dodecyl methacrylate, isodecyl acrylate, lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecyl acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyl adamantyl acrylate, 4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, 4-biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofufuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethyl aminoethyl acrylate, dimethylaminoethyl methacrylate, 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, methyl 3-methoxyacrylate, 3-methoxybutyl acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyldiglycol methacrylate, ethylene glycol acrylate, ethylene glycol monomethyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, propylene glycol monomethacrylate, butoxydiethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3,3 hexafluoroisopropyl acrylate, 1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctylmethacrylat dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N-(1-methylundecyl)acrylamide, N-(n-butoxymethyl)acrylamide, N-(butoxymethyl)methacrylamide, N-(ethoxymethyl)acrylamide, N-(n-octadecyl)acrylamide, and also N,N-dialkyl-substituted amides, for example N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-benzylacrylamides, N-isopropylacrylamide, N-tert-butylacrylamide, N-tert. Octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylonitrile, methacrylonitrile, vinyl ethers such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3,4-dimethoxystyrene, macromonomers such as 2-polystyreneethyl methacrylate (molecular weight Mwof 4000 to 13000 g / mol), poly(methyl methacrylate)ethyl methacrylate (Mwof 2000 to 8000 g / mol).Monomers of component (iii) can advantageously also be selected such that they contain functional groups which support subsequent radiation-chemical crosslinking (for example by electron beams, UV). Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers that aid crosslinking by electron irradiation are, for example, tetrahydrofufuryl acrylate, N-tert-butylacrylamide and allyl acrylate, this enumeration not being exhaustive.The composition of the polyacrylate-based PSA (or based on an acrylate blend) also frequently relates to epoxide-based crosslinkers. Substances containing epoxide groups used are, in particular, multifunctional epoxides, i.e. those which have at least two epoxide units per molecule (i.e. are at least bifunctional). These may be both aromatic and aliphatic compounds. Epoxide-based crosslinkers can also be used in oligomeric or polymeric form.The mixture of acrylates may in turn more preferably have the following composition: (I) 90 to 99% by weight of n-butyl acrylate and / or 2-ethylhexyl acrylate, (II) 1 to 10% by weight of an ethylenically unsaturated monomer having an acid or acid anhydride function, (I) and (II) preferably adding up to 100% by weight.Preferably, the monomer (I) forms a mixture of 2-ethylhexyl acrylate and n-butyl acrylate, more preferably in equal parts.Suitable monomers (II) are advantageously, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and / or maleic anhydride.Preference is given to acrylic acid or methacrylic acid, optionally the mixture of the two.In a preferred embodiment, the pressure-sensitive adhesive used may also be a blend of a vinylaromatic block copolymer and a polyacrylate.In a preferred embodiment, the PSAs comprise, in addition to the at least one vinylaromatic block copolymer, at least one tackifier resin in order to increase the adhesion in the desired manner.According to the general understanding of the skilled worker, an "tackifier resin" is understood to mean an oligomeric or polymeric resin which increases the adhesion (the tack, the inherent tackiness) of the PSA compared with the PSA which does not comprise any tackifier resin but is otherwise identical.In a preferred embodiment, the PSA layer consists of a PSA which is constructed on the basis of vinylaromatic block copolymer and tackifier resins, where at least 30% by weight, and preferably at least 50% by weight, based in each case on the total tackifier resin fraction, of an tackifier resin is selected having a DACP (diacetone alcohol cloud point) of greater than -20° C., preferably greater than 0° C., and a softening temperature (ring & ball) of greater than or equal to 70° C., preferably greater than or equal to 100° C.The tackifier resins are particularly preferably at least 30% by weight, such as in particular at least 50% by weight, based in each case on the total tackifier resin fraction, of hydrocarbon resins or terpene resins or a mixture of the like.It has been found that, as tackifier resins for the PSA(S), it is possible to use advantageously, in particular, nonpolar hydrocarbon resins, for example hydrogenated and nonhydrogenated polymers of dicyclopentadiene, nonhydrogenated, partially, selectively or fully hydrogenated hydrocarbon resins based on C5, C5 / C9 or C9 monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene. The above-mentioned tackifier resins can be used either alone or in a mixture. Both resins which are solid at room temperature and liquid at room temperature can be used. Tackifier resins, hydrogenated or nonhydrogenated, which also contain oxygen, can optionally preferably be used up to a maximum fraction of 70% by weight, based on the total mass of the resins in the adhesive.In a preferred variant, the proportion of the resins which are liquid at room temperature is up to 15% by weight, preferably up to 10% by weight, based on the total PSA.The PSA of the invention preferably comprises from 20 to 60% by weight, based on the total weight of the PSA, of at least one tackifier resin. It is particularly preferred to comprise from 30 to 50% by weight, based on the total weight of the pressure-sensitive adhesive, of tackifier resins.As further additives, typically use can be made of:• Plasticizing agents, such as for example plasticizing oils, or low molecular weight liquid polymers, such as for example low molecular weight polybutenes, preferably with a proportion of 0.2 to 5 wt.-%, based on the total weight of the pressure sensitive adhesive• Primary antioxidants, such as, for example, sterically hindered phenols, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive• secondary antioxidants, such as phosphites or thioethers, for example, preferably in a fraction of from 0.2 to 1% by weight, based on the total weight of the PSA• Process stabilizers such as, for example, C radical scavengers, preferably in a fraction of from 0.2 to 1% by weight, based on the total weight of the pressure sensitive adhesive• Light stabilizers such as, for example, UV absorbers or sterically hindered amines, preferably in a fraction of from 0.2 to 1% by weight, based on the total weight of the PSA• Processing auxiliaries, preferably in a fraction of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive• endblock enhancer resins, preferably in a fraction of from 0.2 to 10% by weight, based on the total weight of the pressure-sensitive adhesive, and• optionally further polymers of preferably elastomeric nature; correspondingly usable elastomers include, inter alia, those based on pure hydrocarbons, for example unsaturated polydienes such as natural or synthetically produced polyisoprene or polybutadiene, chemically substantially saturated elastomers such as saturated ethylene-propylene copolymers, α-olefin copolymers, polyisobutylene, butyl rubber, ethylene-propylene rubber, and also chemically functionalized hydrocarbons such as, for example, halogen-containing, acrylate-containing, allyl- or vinyl ether-containing polyolefins, preferably with a proportion of 0.2 to 10 wt %, based on the total weight of the PSA.The type and amount of the blend components can be selected as needed.According to the invention, it is also the case that the adhesive composition does not comprise some, preferably all, of the stated additives in each case.In one embodiment of the present invention, the PSA comprises further additives. By way of example, but not limitation, crystalline or amorphous oxides, hydroxides, carbonates, nitrides, halides, carbides or mixed oxide / hydroxide / halide compounds of aluminum, silicon, zirconium, titanium, tin, zinc, iron or the (earth) alkali metals may be mentioned. These are essentially clays, for example aluminas, boehmite, bayerite, gibbsite, diaspora and the like. Sheet silicates such as, for example, bentonite, montmorillonite, hydrotalcite, hectorite, kaolinite, boehmite, mica, vermiculite or mixtures thereof are very particularly suitable. However, carbon blacks or further modifications of the carbon, for example carbon nanotubes, can also be used.The adhesives may also be colored with dyes or pigments. In addition to being transparent, white, black or colored, the adhesives may be colored.Plasticizers which can be added are, for example, (meth)acrylate oligomers, phthalates, cyclohexanedicarboxylic esters, water-soluble plasticizers, soft resins, phosphates or polyphosphates.The addition of silicas, advantageously of precipitated silica surface-modified with dimethyldichlorosilane, can be used to adjust the thermal shear strength of the PSA.In a preferred embodiment of the present invention, the PSA is foamed. Foaming is typically accomplished by the introduction and subsequent expansion of microballoons as described above.The absolute density of a foamed PSA is preferably 220 to 990 kg / m 3, more preferably 300 to 970 kg / m 3, more preferably 450 to 900 kg / m 3, in particular 500 to 850 kg / m 3. The relative density describes the ratio of the density of the foamed PSA to the density of the non-foamed PSA identical in formulation. The specific gravity of a pressure-sensitive adhesive is preferably from 0.20 to 0.99, more preferably from 0.30 to 0.97, in particular from 0.45 to 0.90, such as, for example, from 0.50 to 0.85.In the scope of the present invention, it has surprisingly been found that the adhesive tape is removable again. This was not to be expected in that the carrier used in the adhesive tape has a comparatively high softness, so that it was not expected that it would impart to the adhesive tape the strength required for redetachment achieved by stretching. Therefore, an embodiment is preferred in which the adhesive tape can be redetached, in particular by extensive stretching.The present invention further provides a process for producing the adhesive tape of the invention.Process for Producing the Inventive Adhesive TapeIn a first embodiment of the process of the invention, a mixture comprising a polyurethane and expandable microballoons is (i) extruded onto a temporary carrier and the resulting carrier is combined with at least one PSA or (ii) extruded directly onto a PSA layer to give a carrier and is combined on the opposite side with a further PSA.In a preferred embodiment, the microballoons expand during the extrusion and coating process, so that no subsequent supply of temperature is necessary for the expansion of the microballoons. As described in (ii), it is thus possible to produce a multilayer adhesive tape comprising a foamed PU backing in one operation.If necessary, a subsequent or additional tempering of the multilayer composite can take place in order, for example, to influence the foaming rate of the microballoons or to optimize anchoring at the boundary layers.The adhesive tape of the invention is distinguished by a unique profile of properties which, in addition to residue-free redetachability, is characterized inter alia by the damping capacity. These properties are particularly recommended by the adhesive tape of the invention for bonding sensitive components, as are used, for example, in electronic devices. The present invention therefore further provides for the use of the adhesive tape of the invention for bonding components in electronic devices.The present invention further provides an electronic device comprising a carrier according to the invention or an adhesive tape according to the invention.The present invention is explained in more detail with reference to the following examples and figures, these being in no way to be understood as limiting the concept of the invention.Examples:Table 1 shows the raw materials or materials used in the (comparative) raw materials. Table 1 shows the raw materials or materials used in the (comparative) raw materials.Elastollan 880A12FC (for the preparation of the carrier)BASF Polyurethanes GmbHThermoplastic polyurethane (granulate), Shore A = 80Matsumoto FN-190SSDMatsumoto Yushi-Seiyaku Co., Ltd.Unexpanded, expandable, dry microballoons having a mean diameter after expansion of 15 μm; processing in pure form or as masterbatch in EVAElastollan Konz 917 / .4BASF Polyurethanes GmbHMasterbatch of carbon black and polyurethane, pelletsPO Foam 1HuBei Xiangyuan New Material Technology Inc.Polyolefin Foam - PE / EVASylvare TP 95ArizonaTerpene phenol resin; softening point about 95° C.; MW ~ 900 g / mol; hydroxyl value: 40 mgKOH / gErysis GA 240Emerald Performance MaterialsN, N, N', N'-tetrakis(2,3-epoxypropyl)-m-xylenes,a'-diamineVazo 67DuPont2,2'-Azodi(2-methylbutyronitrilePerkadox 16Akzo NobelBis-(4-tert-butylcyclohexanyl) peroxydicarbonateThe following PSAs were used to produce the adhesive tapes:Adhesive 1 (KM1):A conventional 2 L glass reactor suitable for radical polymerizations with evaporative cooling was charged with 300 g of a reaction mixture consisting of 3% by weight of acrylic acid, 67% by weight of n-butyl acrylate, 30% by weight of 2-ethylhexyl acrylate (M n= 64000 g / mol, M w= 1600000 g / mol), and 200 g of acetone:special boiling point spirit 60 / 95 (1:1). After 45 minutes of passage of nitrogen gas with stirring, the reactor was heated to 58°C and 0.15 g of 2,2'-azodi(2-methylbutyronitrile (Vazo 67® Fa. DuPont) dissolved in 6 g of acetone was added. Subsequently, the outer heating bath was heated to 75° C. and the reaction was constantly carried out at this outer temperature. After a reaction time of 1 h, 0.15 g of VAZO 67® dissolved in 6 g of acetone was again added. After 3 hours, it was diluted with 90 g of boiling point spirit 60 / 95.After a reaction time of 5:30 hours, 0.45 g of bis(4-tert-butylcyclohexanyl) peroxydicarbonate (Perkadox 16® Fa Akzo Nobel) dissolved in 9 g of acetone was added. After a reaction time of 7 hours, a further 0.45 g of bis(4-tert-butylcyclohexanyl) peroxydicarbonate (Perkadox 16® Fa Akzo Nobel) dissolved in 9 g of acetone were added. After a reaction time of 10 hours, the mixture was diluted with 90 g of boiling point limit spirit 60 / 95. The reaction was stopped after a reaction time of 24 h and cooled to room temperature.The acrylate content was 45% by weight and it was crosslinked with Erisys GA 240 (0.075% based on the polyacrylate). Kraton D1118 was used as the second polymer component at 20% by weight. Sylvares TP 95 was used as the resin component at 35 wt %.Adhesive 2 (KM2):Preparation of the polyacrylatesA 300 L reactor conventional for radical polymerizations was charged with a total of 100 kg consisting of 47% by weight of n-butyl acrylate, 30% by weight of 2-phenoxyethyl acrylate, 20% by weight of methyl acrylate, 3% by weight of acrylic acid, and 72.4 kg of petroleum / acetone (70:30). After passing nitrogen gas through the reactor for 45 minutes while stirring, the reactor was heated up to 58° C. and 50 g of Vazo® 67 were added. Then, the jacket temperature was heated to 75°C, and the reaction was constantly carried out at this external temperature. After a reaction time of 1 h, 50 g of Vazo® 67 were again added. After 3 hours, dilution was carried out with 20 kg of petrol / acetone (70:30) and after 6 hours with 10.0 kg of petrol / acetone (70:30). To reduce the residual initiators, 0.15 kg of Perkadox® 16 were added in each case after 5.5 and after 7 hours. The reaction was stopped after a reaction time of 24 h and cooled to room temperature. The solution was adjusted to a solids content of 38% by weight. If appropriate, the plasticizer was then incorporated (stirring at room temperature for 24 hours). Finally, 0.075% by weight, based on the polymer, of Erysis GA240 (epoxide cross-linker) were stirred in as cross-linker.The resulting composition was coated in solution by means of a comma doctor blade onto a siliconized PET film. The solvent was removed in a drying channel (20 min, 80° C.). Table 2 shows the formulations of the polyurethane-based supports prepared in the Examples of the present invention. Table 2 shows the formulations of the polyurethane-based supports prepared in the Examples of the present invention.Core layer TPU 1TPU granulesElastollan 880A12FC98,00MicroballoonsMatsumoto FN190-SSD2,00Core layer TPU 2TPU granulesElastollan 880A12FC97,00MicroballoonsMatsumoto FN190-SSD3,00Core layer TPU 3TPU granulesElastollan 880A12FC95,00MicroballoonsMatsumoto FN190-SSD3,00DyeElastollan Konz 917 / .42,00Core Layer PO Foam 1PolyolefinPE / EVA100,00In Comparative Examples 1 and 2, a commercial polyolefin foam was used in a thickness of 200 and 250 μm.Table 3 shows the overview of the adhesive tapes used in the (comparative) examples: <row><cell / ><cell / ><cell / ><cell>[μm]< / cell><cell>[kg / m 3]< / cell><cell>[μm]< / cell><cell>[μm]< / cell>< / row><row><cell>See, for example. 1< / cell><cell>PO Foam 1a< / cell><cell>KM 1< / cell><cell>200< / cell><cell>420< / cell><cell>2x50< / cell><cell>300< / cell>< / row><row><cell>See, for example. 2< / cell><cell>PO Foam 1b< / cell><cell>KM 2< / cell><cell>250< / cell><cell>420< / cell><cell>2x50< / cell><cell>350< / cell>< / row><row><cell>1< / cell><cell>TPU 1< / cell><cell>KM 1< / cell><cell>200< / cell><cell>760< / cell><cell>2x75< / cell><cell>350< / cell>< / row><row><cell>2< / cell><cell>TPU 2< / cell><cell>KM 2< / cell><cell>200< / cell><cell>630< / cell><cell>2x65< / cell><cell>330< / cell>< / row><row><cell>3< / cell><cell>TPU 3< / cell><cell>KM 2< / cell><cell>200< / cell><cell>635< / cell><cell>2x65< / cell><cell>330< / cell>< / row><p xml:id="_3f6cb80396" n="0136">The production of the individual adhesive tapes was carried out as follows:<head xml:id="_3f6cb80397">Production of Adhesive Tapes with TPU Core Layers TPU 1< / head><p xml:id="_3f6cb80398" n="0137">The granules of thermoplastic polyurethane for the production of the supports mentioned as TPU 1 and TPU 2 and TPU 3 (i.e. cores or core layers) are predried in a granular dryer (Somos) at 80° C. for at least 3 hours before processing. The granules of the TPU and of the microballoons prebatch and of all further additives are fed via a simple receiver / hopper via the feed zone to the single-screw extruder (Collin, 25D), referred to below as ESE. The temperature of the ESE is controlled in accordance with the optimum processing temperature of the respective TPU granules. After melting of the granulate, the extrudate is transferred via a hose into a feed block and then into the slot die. Table 4 shows the temperature control of the ESE including the slot die. Table 4: Temperature control of the ESE including the slot die.<title desc="title">Table 4: Temperature control of the ESE including the slot die.[° C.][° C.][° C.][° C.][° C.][° C.][° C.][U / min]*[° C.][° C.][° C.]3016018019020020020015210220220*U / min = Revolutions per minute.The pre-formed melt film is now deposited on a steel roller. Since the TPU variants with a lower Shore hardness are somewhat more pressure-sensitively adhesive and can therefore be released again more poorly from the steel roll, it has proven to be useful to coat directly onto a PET carrier having a release function, i.e. temporary carrier or liner, which is fed via a take-off roll and via the take-off roll which is half wrapped around it and is then wound up. The TPU supports (TPU core layers) produced are free of process auxiliaries and have no crystalline superstructure.After the desired layer thickness has been established, the bale with the PET carrier with release function is replaced at the unwinder with the prefabricated functional layer, i.e. the layer of pressure-sensitive adhesive containing unexpanded microballoons as described above. In this way, coating is carried out directly on the functional layer. Via a further unwinder, the second prefabricated PSA layer (comprising unexpanded microballoons as described above), which has the same thickness as the first PSA layer, is laminated via the guide roll or pressure roll to the open, top TPU layer. This three-layer product is now wound up.Production of Adhesive Tapes with PO Foam Comparative Examples 1 and 2:The PSA layers on PET supports having a release function are laminated on both sides onto the PO foam.Results:Table 5 shows the construction of the adhesive tapes of the (comparative) examples formed by combination of the abovementioned supports from Table 2 and the PSA layer KM1 and KM2. The adhesive tapes are each double-sided, i.e. a PSA layer (of the same thickness) is arranged on both sides of the backing. The table also shows mechanical and adhesive properties of the adhesive tapes. Table 5: Construction of the adhesive tapes of the (comparative) examples and their mechanical and adhesive properties. Table 5: Construction of the adhesive tapes of the (comparative) examples and their mechanical and adhesive properties.10%20%30%40%50%1 - 5[J][J][N]See, for example. 113,931,163,5117,0181,030,740,83250See, for example. 214,124,547,293,4155,210,700,70391125,238,954,274,6107,841,231,45200222,936,852,172,1105,351,551,55382323,237,652,972,9105,951,551,55364The adhesive tapes of all examples of the invention meet the set z-direction impact strength requirements according to the DuPont z- and xy-direction test of at least 0.8 J. Similarly, they each have good redetachability (i.e., (a) substantially no tears and at most light adhesive residues that are easily removable with ethanol, which in our test corresponds to a value of at least 4, or even no tears and no residues and no peel angle dependence, which in our test corresponds to a value of at least 5). Comparative Examples 1 and 2 do not have sufficient redetachability.The compressibility, i.e. the force to be applied when the adhesive tapes are compressed in the examples according to the invention, is particularly suitable for use in electronic components in order to ensure sufficient shock absorption. The force required in Comparative Examples 1 and 2 is comparatively too high with already low compressions of 30%.In addition, the examples according to the invention are each characterized by a push-out strength of at least 150 N.DESCRIPTION OF THE FIGURESFIG. 1 shows the results of measuring the compressive strength of the supports produced according to the examples after one cycle (FIG. 1 a) and after 4 cycles (FIG. 1 b). As can be seen, the supports according to the invention made of foamed TPU (diamond) according to Example 1 have a significantly lower hardness than conventional supports made of foamed polyethylene (circle). Whereas in the case of the conventional carriers a force of up to 180 N / cm 2 has to be applied in order to achieve a compression of 50%, this is to be achieved with a significantly lower force exertion in the case of the carriers according to the invention. The compressive strength of the supports according to the invention also shows a clearly more linear profile.Surprisingly, the force increases with increasing compression of the inventive carriers only slightly and almost linearly compared to the PE / EVA-based adhesive tapes, thus producing a significantly better damping capacity of the inventive carriers.Test MethodsCompressive Hardness Based on ISO 3386The measurement method is used for characterizing and quality controlling foams. The compressive strength is the compressive stress in N / cm 2. determined in the case of a fixed deformation of the foam in the z direction during the loading process.Test specimens are cut to size 30 x 30 mm from the material to be tested and are stacked to a height of 15 mm. The cut samples must then be conditioned under the test climate for 24 hours. A sample of the foam to be tested is compressed by means of a pressure testing machine under specified conditions of 5X. During the last upsetting process, both the deformation diagram is recorded and the compressive stress is determined in the case of the predetermined deformation. In addition, if required, the force is also determined during the first upsetting operation. 5 samples per sample or product are tested.Push-out StrengthBy means of the push-out test, statements can be obtained about how high the resistance of an adhesive bond of a component in a frame-shaped body, for example a window in a housing, is.A rectangular, frame-shaped sample was cut out of the adhesive tape to be tested (external dimensions 43 mm x 33 mm; web width 2.0 mm each, internal dimensions (window cutout) 39 mm x 29 mm, adhesive surface on the top and bottom sides 288 mm each 2). This sample was bonded to a rectangular ABS plastic frame (ABS=acrylonitrile-butadiene-styrene copolymers) (external dimensions 50 mm x 40 mm, web width of the long webs 8 mm each; web width of the short webs 10 mm each; internal dimensions (window cutout) 30 mm x 24 mm; thickness 3 mm). A rectangular PMMA disc (PMMA=polymethyl methacrylate) with the dimensions 45 mm x 35 mm was bonded to the other side of the sample of the double-sided adhesive tape. The full available adhesive area of the adhesive tape was used. The bonding of the ABS frame, adhesive tape sample and PMMA window was carried out in such a way that the geometric centers, the bisector of the acute diagonal angles and the bisector of the obtuse diagonal angles of the rectangles each lie one above the other (corner-on-corner, long sides on long sides, short sides on short sides). The bond area was 360 mm 2. The bond was pressed for 5 s at 10 bar and stored conditioned at 23° C. / 50% relative humidity for 24 hours. Immediately after storage, the adhesive bond comprising ABS frame, adhesive tape and PMMA pane was placed with the protruding edges of the ABS frame on a frame frame (sample holder) in such a way that the bond was oriented horizontally and the PMMA pane was oriented downward in a freely hanging manner.A printing die is now moved at a constant speed of 10 mm / s vertically from above through the window of the ABS frame, so that it presses centrally onto the PMMA plate, and the respective force (determined from the respective pressure and contact surface between the die and the plate) is recorded as a function of the time from the first contact of the die with the PMMA plate until shortly after it has dropped (measurement conditions 23° C., 50% relative humidity).The force acting immediately before the adhesive bond between the PMMA plate and the ABS frame fails (maximum force F max in the force-time diagram in N) is recorded as a response of the push-out test. A five-fold determination is made.Breakdown Toughness: DuPont Z-plane and xy-plane TestA square, frame-shaped sample is cut out of the adhesive tape to be tested (external dimensions 33 mm x 33 mm, web width 2.0 mm, internal dimensions (window cut-out) 29 mm x 29 mm). This sample is bonded to a polycarbonate (PC) frame (outer dimensions 45 mm x 45 mm, web width 10 mm, inner dimensions (window cutout) 25 mm x 25 mm; thickness 3 mm). On the other side of the double-sided adhesive tape, a PC window of 35 mm x 35 mm is adhered. The bonding of PC frames, adhesive tape frames and PC windows is effected in such a way that the geometric centers and the diagonals are each located one above the other (corner-on-corner). The bond area is 248 mm 2. The bond is pressed at 248 N for 5 s and stored conditioned at 23° C. / 50% relative humidity for 24 hours.Immediately after storage, the adhesive composite comprising PC frame, adhesive tape and PC window is clamped into a sample holder in such a way that for testing in the z-plane the composite is aligned horizontally (for testing in the xy-direction vertical alignment of the composite). The PC frame rests flat on the protruding edges on the sample holders, so that the PC window below the PC frame is present in a suspended manner (held by the adhesive tape pattern). The sample holder is then inserted centrally into the provided receptacle of the "DuPont Impact Tester". The cuboid impact head with the impact geometry 3 mm x 20 mm is placed flush on the edge of the PC window that is freely accessible from above.On the thus arranged composite of sample holder, sample and impact head, a weight guided on two guide rods with a mass of 150 g is dropped vertically from a height of 5 cm (measurement conditions 23° C., 50% relative humidity). The height of the falling weight is increased in 5 cm steps until the impact energy introduced destroys the sample by the breakdown load and the PC window detaches from the PC frame.In order to compare experiments with different samples, the energy is calculated as follows:Five samples per product are tested and the mean energy value is reported as the index for the breakdown toughness.Redetachability - Tear testA strip-shaped sample having a width of 10 mm is cut out of the double-sided adhesive tape to be tested. This sample is adhered to a cleaned SUS steel plate of outer dimensions 200 mm x 50 mm x 3 mm). Three individual strips are to be bonded together parallel at a distance of at least 1 cm. The covering of the double-sided tapes should not be removed in this case. The adhesive tape ends at the substrate edge. The bonds are activated with a 4 kg steel roll with at least 5 double strokes at 10 m / min and conditioned for 72 hours at 85° C. / 85% relative humidity. After storage, the test specimen is cooled at RT for two hours and the bond is likewise removed manually at RT. During removal, the inspector makes an evaluation. Test specimens are examined for each sample 3, the re-releasability is assessed in school notes of 1 to 5. numeral 5 represents the best result.5 (Best result)No tear and no residue and no peel angle dependence4No tears and light residue easily removable with ethanol and there is no peel angle dependence.3Moderate risk of tear and there is no peel angle dependence and residue is easily removable with ethanol2High risk of tear and residue are removable with ethanol1High numbers of tears and / or it is impossible to remove the tape from the substrate and / or cohesive failure of the adhesive which are not removable with ethanolShore A hardnessShore A hardness of a sample is determined according to ASTM D 2240.Modulus at 100% elongationThe modulus at 100% elongation of a sample is determined in accordance with DIN 53504.Thickness: ThicknessThe thickness of an adhesive layer can be determined by determining the thickness of a portion, defined with respect to its length and its width, of such an adhesive layer applied to a liner, minus the (known or separately determinable) thickness of a portion of the same dimensions of the liner used. The thickness of the adhesive layer can be determined with precisions of less than 1 μm deviation using commercially available thickness measurement devices (probe testing devices). If thickness variations are detected, the mean value of measurements is given at at least three representative points, i.e. in particular not measured at creases, folds, specks and the like.As already the thickness of an adhesive layer, the thickness of an adhesive tape (adhesive strip) or of a carrier can also be determined analogously by means of commercially available thickness measurement devices (probe testing devices) with precisions of less than 1 μm deviation. If thickness variations are detected, the mean value of measurements is given at at least three representative points, i.e. in particular not measured at creases, folds, specks and the like.Density: DensityThe density of adhesive layers is determined by quotient formation of the application of adhesive and the thickness of the adhesive layer applied to a liner.The coatweight can be determined by determining the coatweight of a section of this type of adhesive layer applied to a liner, which section is defined with respect to its length and its width, minus the (known or separately determinable) coatweight of a section of the same dimensions of the liner used.The thickness of an adhesive layer can be determined by determining the thickness of a portion, defined with respect to its length and its width, of such an adhesive layer applied to a liner, minus the (known or separately determinable) thickness of a portion of the same dimensions of the liner used. The thickness of the adhesive layer can be determined with precisions of less than 1 μm deviation using commercially available thickness measurement devices (probe testing devices). If thickness variations are detected, the mean value of measurements is given at at least three representative points, i.e. in particular not measured at creases, folds, specks and the like.The density of a support can be determined analogously.Static glass transition temperature TgThe glass transition temperature of polymers can be determined by means of dynamic scanning calorimetry (DSC, to DIN 53765). For this purpose, about 5 mg of the untreated polymer samples are weighed into an aluminum crucible (volume 25 μl) and sealed with a perforated lid. For the measurement, a DSC 204 F1 from Netzsch is used, which is operated under nitrogen for inertization. The sample is first cooled to -150° C., then heated to +150° C. at a heating rate of 10 K / min and cooled again to -150° C. The subsequent second heating curve is again run at 10 K / min and the change in the heat capacity is recorded. Glass junctions are characterized as steps in the thermogram. The glass transition temperature is determined as follows. A tangent is applied to the baseline of the thermogram before the stage. In the region of the step, a compensation line is placed parallel to the ordinate in such a way that it intersects the two tangents, namely in such a way that two regions of equal content (between each tangent, the compensation line and the measurement curve) are produced. The intersection of the compensation straight line positioned in this way with the measurement curve yields the glass transition temperature.Molecular weight Mn, MwThe data on the number-average molecular weight M n or weight-average molecular weight M w in this specification relate to determination by gel permeation chromatography (GPC). The determination is carried out on 100 μl of clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1% by volume trifluoroacetic acid is used as the mobile phase. The measurement is carried out at 25° C. The precolumn used is a column type PSS-SDV, 5 μm, 103 Å, 8.0 mm*50 mm (details here and below in the order: type, particle size, porosity, internal diameter*length; 1 Å=10 -10 m). For separation, a combination of the columns of the type PSS-SDV, 5 μm, 10 3 Å and 10 5 Å and 10 6 Å with in each case 8.0 mm*300 mm is used (columns from Polymer Standards Service; detection by means of a differential refractometer Shodex RI71). The flow rate is 1.0 ml per minute. The calibration is carried out with polar molecules, such as the starting materials of the polyurethane, or with polyacrylates against PMMA standards (polymethyl methacrylate calibration) and otherwise against PS standards (polystyrene calibration).Tackifier Resin Softening TemperatureThe tackifier resin softening temperature is carried out according to the relevant methodology known as Ring & Ball and standardized according to ASTM E 28.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2015 / 135134 A1

[0003] EP 3 757 157 A1

[0004] DE 43 13 008 A1

[0085] Cited Non-Patent Literaturehttps: / / www.tesa.com / en / industry / electronics / solutions / pe-foam-tapes),

[0004] DIN 53765

[0166]

Claims

Carrier for an adhesive tape, wherein the carrier comprises at least one closed-cell layer foamed with microballoons and based on a thermoplastic polyurethane, wherein the carrier has a compressive hardness of at least 50% at a maximum force of 140 N / cm 2, preferably at a maximum force of 120 N / cm 2, more preferably at a maximum force of 100 N / cm 2 determined according to DIN EN ISO 3386-2.The carrier according to claim 1, characterized in that the carrier has a density of 300 to 1200 kg / m 3, preferably 400 to 900 kg / m 3 particularly preferably 500 to 800 kg / m 3.The carrier according to at least one of the preceding claims, characterized in that the polyurethane is selected from the group consisting of aromatic polyurethanes, aliphatic polyurethanes, polyester-polyol-based polyurethanes, polyether-polyol-based polyurethanes, polycarbonate-based polyurethanes and hybrids and mixtures thereof.Carrier according to at least one of the preceding claims, characterized in that the polyurethane is crosslinked or uncrosslinked.Support according to at least one of the preceding claims, characterized in that the support has a thickness of 20 to 2500 μm, preferably 150 to 1000 μm.The carrier according to at least one of the preceding claims, characterized in that the carrier has a breakdown strength of 0.3 to 1.5 J, determined by means of DuPont.Adhesive tape comprising a backing according to at least one of the preceding claims, where the backing is coated at least on one side with a pressure-sensitive adhesive.Adhesive tape according to Claim 7, characterized in that it is removable again.Adhesive tape according to at least one of Claims 7 or 8, characterized in that at least one of the PSA layers consists of a PSA based on vinylaromatic block copolymer.Adhesive tape according to at least one of Claims 7 to 9, characterized in that at least one of the PSA layers consists of a polyacrylate-based PSA.Adhesive tape according to at least one of Claims 7 to 10, characterized in that at least one of the PSA layers is foamed, preferably by microballoons.Process for producing an adhesive tape according to at least one of Claims 7 to 11, in which a mixture of a polyurethane and expandable microballoons is (i) extruded onto a temporary carrier and the resulting carrier is combined with a pressure-sensitive adhesive, or (ii) extruded onto a pressure-sensitive adhesive layer to give a carrier, the carrier being combined on the side opposite the pressure-sensitive adhesive layer with a further pressure-sensitive adhesive, the carrier being foamed during or after the extrusion and / or coating process.Use of an adhesive tape according to at least one of Claims 7 to 11 for bonding components in electronic devices.Electronic device comprising a carrier according to at least one of Claims 1 to 6 and / or an adhesive tape according to at least one of Claims 7 to 11.

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