Laminate, process and use

Abstract

Laminate comprising the following layers in the specified order: (i) a first pressure-sensitive adhesive layer (11) comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes; (ii) a metal layer (12); (iii) a propellant layer (13); and (iv) a second pressure-sensitive adhesive layer (14) comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes, wherein the metal layer (12) according to (ii) can be inductively heated to a temperature in a range from 50 to 200 °C in a magnetic field with a frequency in a range from 100 Hz to 200 kHz.

Description

[0001] The present invention relates to a laminate. Furthermore, the present invention relates to a method for producing this laminate. Furthermore, the present invention relates to an assembly containing the laminate and a method for detaching the laminate.

[0002] Most adhesive tape solutions are not removable, or only removable without damaging the substrates. Recently, there has been increased interest in "debonding-on-demand" functionalities, which are due to environmental regulations, end-customer awareness of sustainability, and increasing cost pressure during manufacturing. Application scenarios for debonding processes are classified into rework, repair, recycling, and processing aids. The focus of the present invention is the reliable separation of two substrates bonded with a laminate. Some debonding concepts are described by C. Sato in "Recycling and environmental aspects," 2011, 58, 20, pages 1506-1526, and by A. Hutchinson et al. in "Journal of Adhesion," 2016, "Overview of disbonding technologies for adhesive bonded joints," pages 737-755.The DIN Standards Committee Materials Testing (NA 062-10-02 AA Test Methods in Structural Adhesive Bonding Technology) also provides a systematic approach to classifying debonding technologies.

[0003] Debonding technologies aim to achieve a cohesive splitting of the adhesive layer or an adhesive detachment of the adhesive layer from the substrate. While the former requires cleaning of the substrate before rebonding, the latter does not require this. Adhesive-releasing technologies that guarantee the required high and permanently reliable bond strength are generally more difficult to implement or take a very long time to apply, such as debonding using a solvent. For example, cohesive-splitting adhesive bonds are currently predominantly used, particularly in the rework or repair of electronic devices such as smartphones and tablet computers. These adhesive bonds are often designed as pressure-sensitive adhesive tapes whose cohesion is reduced by increasing the temperature to such an extent that manual, cohesive separation of the bond is possible.The result is extensive rework to prepare the substrate surface contaminated with adhesive residues for re-bonding.

[0004] EP 2 493 995 B1 describes a method for bonding a heat-activated bondable surface element to a bonding substrate having a thermal conductivity coefficient of at most 5 W / mK. In the method, surface elements are brought into contact with the adhesive layer and then inductively bonded under pressure in an alternating electromagnetic field at a frequency of 100 Hz to 200 kHz for a maximum duration of 20 s at a pressure of at least 1 MPa.

[0005] EP 1 814 703 B1 describes a process for recycling electrical or electronic components, wherein a bond between two components of the component, which is effected by means of a pressure-sensitive adhesive, is dissolved by expanding expandable particles located in the pressure-sensitive adhesive by the supply of energy and thereby bursting open the adhesive bond.

[0006] EP 2 516 573 B1 describes a method for bonding and detaching two substrate surfaces. A heat-activated bondable surface element with two layers of different heat-activated adhesives is used for the bonding. Bonding takes place at a temperature T1 at which simultaneous heat activation of the two heat-activated adhesives occurs. Detachment takes place at a temperature T2 at which, under specified conditions, only one of the heat-activated layers of the heat-activated bondable surface element loses its adhesive effect in the adhesive bond to such an extent that the adhesive bond separates.

[0007] WO 2021 / 200 789 A1 discloses a double-sided adhesive film consisting of a first adhesive layer (X1), a thermally expandable layer (Y1) arranged thereon, followed by a non-thermally expandable base layer (Y2) and a second adhesive layer (X2), wherein the adhesive layers (X1) and (X2) are composed of an acrylate block copolymer.

[0008] DE 10 2012 223 670 A1 relates to a pressure-sensitive adhesive film strip consisting of three layers, which can be removed again by stretching essentially in the bonding plane without leaving residues or being destroyed, with a carrier on which a first, outer layer of adhesive is present on at least one side.

[0009] JP 6 417 837 B2 discloses a double-sided pressure-sensitive adhesive tape comprising two acrylate-based pressure-sensitive adhesive layers and an intermediate layer comprising a thermoplastic resin and a filler.

[0010] WO 2013 / 019 493 A2 discloses a multilayer pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive film comprises at least two semi-adhesive layers and an intermediate layer with a polymeric foam material.

[0011] US 2013 / 0 335 879 A1 describes a double-sided pressure-sensitive adhesive tape containing a heat-removable pressure-sensitive adhesive layer containing heat-expandable microspheres.

[0012] US 2014 / 0 322 474 A1 discloses an adhesive composition containing an expandable polymer based on a Meldrum's acid derivative. US 2022 / 0 195 250 A1 discloses a damping sheet containing a damping material comprising 10-50 wt.% of a block copolymer elastomer, 5-40 wt.% of a fiber, 5-45 wt.% of a thermoplastic non-elastomeric polymer, and 5-50 wt.% of a tackifier.

[0013] The known detachment mechanisms are usually realized in the adhesive layer itself and / or in the interface between the adhesive and the substrate.

[0014] It is therefore desirable to provide a laminate, a method, and an assembly that avoid, or largely avoid, the disadvantages of the aforementioned laminates, methods, and assemblies. In particular, a laminate should be provided in which the adhesive bond between two substrates and / or a corresponding adhesive tape or a device made of adhesive tapes can be reliably released. This should combine the preservation of a high and permanently reliable bond strength with rapid detachability. Furthermore, the joining partners can be very easily cleaned, allowing them to be reused without effort.

[0015] This object is addressed by a laminate comprising a first pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes, a metal layer heatable by magnetic induction, a blowing agent layer, and a second pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes. At least one pressure-sensitive adhesive layer can be removed by stretching.

[0016] Therefore, the present invention relates to a laminate comprising the following layers in the order: (i) a first pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes; (ii) a metal layer; (iii) a propellant layer; and (iv) a second pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes wherein the metal layer according to (ii) can be inductively heated to a temperature in a range of 50 to 200 °C in a magnetic field of a frequency in a range of 100 Hz to 200 kHz.

[0017] A laminate is a material or product consisting of two or more layers bonded together. These layers can be made of the same or different materials. Laminates can be produced by either lamination or direct coating.

[0018] Preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) comprises an elastomer component (a), an adhesive resin component (b), and optionally a soft resin component (c). Particularly preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) comprises an elastomer component (a), an adhesive resin component (b), and a soft resin component (c).

[0019] Preferably, the elastomer component according to (a) comprises a block copolymer having a structure ABA, (AB)n, (AB)nX or (ABA)nX, preferably a diblock copolymer AB and / or a triblock copolymer ABA, wherein - the blocks A independently of one another form a polymer preparable from a polymerization mixture containing vinylaromatic monomers having 8 to 12 C atoms; - the blocks B independently of one another form a polymer producible from a polymerization mixture containing alkene monomers having 4 to 18 C atoms; - X is a residue of a coupling reagent or initiator and - n ≥ 2, include.

[0020] The coupling agent is used to link two or more vinylaromatic-diene diblocks together. The initiator is used for the preparation of the elastomer component according to (a); this could be, for example, sodium naphthalide, which enables bidirectional chain growth.

[0021] The blocks A can preferably be prepared from a polymerization mixture containing styrene and α-methylstyrene, preferably from a polymerization mixture containing styrene.

[0022] Preferably, the blocks B can be prepared from a polymerization mixture containing monomers of 1,3-dienes and isobutylene, more preferably from a polymerization mixture containing butadiene and / or isoprene.

[0023] To impart pressure-sensitive adhesive properties to polydienes, they must be mixed with adhesive resins. This also applies to vinylaromatic block copolymers containing polydiene blocks.

[0024] Preferably, the blocks A have a proportion in the block copolymer in a range from 14 to 35 wt.%, more preferably in a range from 14 to 30 wt.%.

[0025] Preferably, the blocks B have a proportion in the block copolymer in a range of 65 to 86 wt.%.

[0026] In addition to the at least one vinylaromatic block copolymer, the pressure-sensitive adhesive layer comprises at least one adhesive resin component (b) to enhance adhesion as desired. The adhesive resin component (b) should be compatible with the elastomer component (a) of the block copolymers, and in particular with the B blocks of the block copolymers.

[0027] According to the general understanding of those skilled in the art, an “adhesive resin component” is understood to mean an oligomeric or polymeric resin which increases the adhesion (tack, inherent stickiness) of the pressure-sensitive adhesive layer compared to the pressure-sensitive adhesive layer which does not contain an adhesive resin component but is otherwise identical.

[0028] The adhesive resin component according to (b) preferably has a weight-average molecular weight MW, determined according to test method 1, in a range from 400 to 15,000 g / mol, more preferably in a range from 400 to 5,000 g / mol, more preferably in a range from 500 to 2,000 g / mol.

[0029] Preferably, the adhesive resin component according to (b) comprises one or more materials selected from the group consisting of non-hydrogenated, partially or fully hydrogenated resins based on rosin or rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively or fully hydrogenated hydrocarbon resins based on C-5, C-5 / C-9 or C-9 monomer mixtures and polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene.

[0030] The adhesive resin component according to (b) can be used alone or in a mixture.

[0031] Preferably, the soft resin component according to (c) has a softening temperature of < 30 °C, determined according to test method 2.

[0032] Preferably, the soft resin component according to (c) comprises a rosin-, hydrocarbon- or polyterpene-based soft resin.

[0033] Preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) comprises the soft resin component according to (c) in a range from 0.1 to 15 wt.%, more preferably 2 to 10 wt.%.

[0034] Preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) additionally comprises additives (d).

[0035] Preferably, the additives according to (d) comprise one or more materials selected from the group consisting of light stabilizers, flame retardants, fillers, dyes, pigments, plasticizers, antioxidants, process stabilizers, processing aids and endblock reinforcing resins.

[0036] The adhesive layer can be colored in any color or be white, gray or black.

[0037] As such or other additional additives can typically be used: • Light stabilizers such as UV absorbers or sterically hindered amines, preferably in a proportion of 0.2 to 1 wt.% based on the total weight of the pressure-sensitive adhesive layer, • Plasticizers such as low molecular weight liquid polymers, such as low molecular weight polybutenes, preferably in a proportion of 0.2 to less than 5 wt.% based on the total weight of the pressure-sensitive adhesive layer, • Antioxidants, such as primary antioxidants such as sterically hindered phenols, preferably in a proportion of 0.2 to 1 wt.% based on the total weight of the pressure-sensitive adhesive layer, and such as secondary antioxidants such as phosphites or thioethers, preferably in a proportion of 0.2 to 1 wt.% based on the total weight of the pressure-sensitive adhesive layer, • Process stabilizers such as C radical scavengers, preferably in a proportion of 0.2 to 1 wt.% based on the total weight of the pressure-sensitive adhesive layer, • processing aids, preferably in a proportion of 0.2 to 1 wt.% based on the total weight of the pressure-sensitive adhesive layer, • Endblock reinforcing resins, if desired, preferably in a proportion of 0.2 to 10 wt.% based on the total weight of the pressure-sensitive adhesive layer, • optionally further polymers, preferably of an elastomeric nature; correspondingly usable elastomers include, among others, 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 chemically functionalized hydrocarbons such as halogen-containing, acrylate-containing, allyl- or vinyl ether-containing polyolefins, preferably in a proportion of 0.2 to 10 wt.% based on the total weight of the pressure-sensitive adhesive layer.

[0038] The type and amount of additives can be selected as needed. It is also in accordance with the invention if the adhesive layer does not contain some or even all of the additives mentioned.

[0039] There are, in principle, no particular restrictions regarding the thickness of the pressure-sensitive adhesive layer. The first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) preferably has a thickness in a range from 25 to 3000 µm, more preferably in a range from 50 to 1000 µm.

[0040] Preferably, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer in the laminate are identical in composition. Alternatively, they may differ in composition. Furthermore, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer in the laminate preferably have the same thickness. Alternatively, they may differ in thickness.

[0041] Preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) is a pressure-sensitive adhesive layer that can be redetached by stretching in the direction of the bonding plane.

[0042] The first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer is self-adhesive, highly extensible, and largely elastic, and can be removed without residue or damage by stretching in the bonding layer. This property is also referred to as strippability. In order for strippable pressure-sensitive adhesive layers to be easily removed without residue, they must possess certain adhesive properties: During stretching, the tackiness of the pressure-sensitive adhesive layer must decrease significantly. The lower the adhesive strength in the stretched state, the less damage the substrate is subjected to during removal. Further details regarding the pressure-sensitive adhesive layer are disclosed in EP 3 578 618 B1.

[0043] Preferably, the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) has an elongation at break of at least 100%, determined according to test method 3, and a resilience of more than 50%, determined according to test method 4.

[0044] Preferably, the metal layer according to (ii) comprises one or more materials selected from the group consisting of aluminum, copper, nickel, iron and steel, more preferably aluminum and copper.

[0045] In principle, there are no particular restrictions regarding the thickness of the metal layer. The metal layer according to (ii) preferably has a thickness in a range from 1 to 200 µm, more preferably in a range from 5 to 100 µm.

[0046] Preferably, the metal layer according to (ii) additionally comprises a carrier, wherein the carrier comprises one or more materials selected from the group consisting of polyethylene terephthalate, polyethylene, and polypropylene, preferably polyethylene terephthalate. In the presence of a carrier, the propellant layer according to (iii) is preferably arranged on the side of the metal layer.

[0047] The metal layer according to (ii) can be inductively heated to a temperature in a range of 50 to 200 °C, particularly preferably in a range of 70 to 180 °C, in a magnetic field of a frequency in a range of 100 Hz to 200 kHz, preferably in a range of 5 kHz to 50 kHz, particularly preferably in a range of 10 kHz to 30 kHz, further preferably for a time period in a range of 1 to 20 s, particularly preferably in a range of 5 to 15 s.

[0048] Preferably, the blowing agent layer according to (iii) comprises one or more materials selected from the group consisting of azo compounds, hydrazine compounds, sulfonyl semicarbazide compounds, sulfonyl semicarbazide compounds, tetrazole compounds, N-nitroso compounds and carbonate compounds.

[0049] Preferably, the propellant layer according to (iii) comprises expandable, thermoplastic microspheres.

[0050] Preferably, the expandable thermoplastic microspheres comprise a thermoplastic polymer shell and a blowing agent enclosed therein.

[0051] Expandable, thermoplastic microspheres, also known as microballoons or microspheres, are commercially available, for example, under the brand name EXPANCEL®. In such microspheres, the blowing agent is typically a liquid with a boiling point no higher than the softening temperature of the thermoplastic polymer shell. The softening temperature of the polymer shell, usually corresponding to its glass transition temperature T g , is preferably within the range of 0 to 140 °C, more preferably 30 to 100 °C. Upon heating, the propellant evaporates, increasing the internal pressure, and simultaneously softens the shell, leading to a significant enlargement of the microspheres. The temperature at which expansion begins is called T start , while the temperature at which the maximum expansion is reached is called T max is referred to. T startfor the expandable, thermoplastic microspheres is preferably from 40 to 140 °C, most preferably from 50 to 100 °C. T max of the expandable, thermoplastic microspheres is higher than T start and preferably from 80 to 200 °C, more preferably from 100 to 170 °C.

[0052] In principle, there are no particular restrictions regarding the thickness of the propellant layer. The propellant layer according to (iii) preferably has a thickness in a range from 10 to 150 µm, more preferably in a range from 25 to 100 µm.

[0053] The propellant layer according to (iii) particularly preferably contains expandable, thermoplastic microspheres which, in the unexpanded state at 25°C, have an average diameter of 3 µm to 30 µm, more preferably 5 µm to 20 µm, and / or, after expansion, an average diameter of 10 µm to 200 µm, preferably 15 µm to 90 µm. The average diameter of the unexpanded microspheres is preferably below the layer thickness of the propellant layer.

[0054] Preferably, the blowing agent layer according to (iii) comprises at least 50% by weight, more preferably at least 90% by weight of a thermoplastic polyurethane.

[0055] The thermoplastic polyurethane preferably comprises at least one polyisocyanate component and at least one polyol component.

[0056] Preferably, the thermoplastic polyurethane comprises a thermoplastic polyurethane dispersion.

[0057] As polyurethane dispersion in the sense of the present invention, the following dispersions can be used in particular, optionally in combination: • Anionically stabilized aliphatic polyester-polyurethane dispersions (dispersions based on polyester and aliphatic anionic isocyanate-polyurethane). These include the following products marketed by Covestro AG: Impranil® LP RSC 1380, DL 1537 XP, DL 1554 XP, • anionically stabilized aliphatic polyether polyurethane dispersions. These include the following products, marketed by Covestro AG: Impranil® 25 LP DSB 1069, • anionically stabilized aliphatic polycarbonate-polyester-polyurethane dispersions. These include the following products marketed by Covestro AG: Impranil®DLU and • Anionically stabilized polycarbonate polyurethane dispersions. These include the following products, marketed by Covestro AG: Impranil® DL 2288 XP.

[0058] The thermoplastic polyurethane can preferably be produced from a polymerization mixture containing at least one diisocyanate, at least one polyester polyol and optionally at least one alkanediol.

[0059] Preferably, the at least one diisocyanate is selected from the group consisting of toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), 4,4'-diphenylmethane diisocyanate (MDI), p,p'-bisphenyl diisocyanate (BPDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), or 4,4'-diisocyanatodicyclohexylmethane (H12MDI), preferably toluene diisocyanate (TDI).

[0060] Diisocyanates with substituents in the form of halo, nitro, cyano, alkyl, alkoxy, haloalkyl, hydroxyl, carboxy, amido, amino or combinations thereof are also possible.

[0061] Overall, all known aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyfunctional isocyanates can be used.

[0062] Specifically, the following may be mentioned as examples: alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecane diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate, and preferably hexamethylene 1,6-diisocyanate;cycloaliphatic diisocyanates such as cyclohexane-1,3-diisocyanate and cyclohexane-1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate and any mixtures of these isomers, 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate and any mixtures of these isomers, and preferably aromatic di- and polyisocyanates, such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates, Polyphenylpolymethylene polyisocyanates, mixtures of 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (crude MDI), and mixtures of crude MDI and toluene diisocyanates. The organic di- and polyisocyanates can be used individually or as mixtures.

[0063] The polyisocyanate component preferably has a number-average molecular weight M n , determined according to test method 1, in a range from 60 to 50,000 g / mol, more preferably in a range from 400 to 10,000 g / mol, more preferably in a range from 400 to 6,000 g / mol.

[0064] So-called modified polyfunctional isocyanates, i.e. products obtained by chemical conversion of organic di- and / or polyisocyanates, are also frequently used. Examples include di- and / or polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione and / or urethane groups. Specifically, the following are suitable: organic, preferably aromatic, polyisocyanates containing urethane groups and having NCO contents of 33.6 to 15% by weight, preferably 31 to 21% by weight, based on the total weight. Examples include crude MDI or 2,4- or 2,6-tolylene diisocyanate modified with low molecular weight diols, triols, dialkylene glycols, trialkylene glycols or polyoxyalkylene glycols with number-average molecular weights of up to 6,000 g / mol, in particular up to 1,500 g / mol. Examples of suitable di- orPolyoxyalkylene glycols include diethylene, dipropylene, polyoxyethylene, polyoxypropylene, and polyoxypropylenepolyoxyethylene glycols, triols, and / or tetrols. Also suitable are NCO-containing prepolymers with NCO contents of 25 to 3.5 wt.%, preferably 21 to 14 wt.%, based on the total weight, prepared from polyester and / or preferably polyether polyols and 4,4'-diphenylmethane diisocyanate, mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate, or crude MDI. Liquid polyisocyanates containing carbodiimide groups and / or isocyanurate rings and having NCO contents of 33.6 to 15% by weight, preferably 31 to 21% by weight, based on the total weight, for example based on 4,4'-, 2,4'- and / or 2,2'-diphenylmethane diisocyanate and / or 2,4- and / or 2,6-toluene diisocyanate, have also proven suitable.

[0065] The modified polyisocyanates can be mixed with each other or with unmodified organic polyisocyanates such as 2,4'-, 4,4'-diphenylmethane diisocyanate, crude MDI, 2,4- and / or 2,6-toluene diisocyanate.

[0066] Diphenylmethane diisocyanate isomer mixtures or crude MDI, and in particular crude MDI with a diphenylmethane diisocyanate isomer content of 30 to 55 wt.%, as well as urethane group-containing polyisocyanate mixtures based on diphenylmethane diisocyanate with an NCO content of 15 to 33 wt.%, have proven particularly suitable as isocyanates.

[0067] Preferably, the polyol component comprises one or more materials selected from the group consisting of alkanediols, polyetherdiols, polyesterdiols, polycarbonatediols, polycaprolactone polyols and polyacrylate polyols, preferably polyetherdiols, polyesterdiols and polycarbonatediols.

[0068] More preferably, the polyol component comprises one or more materials selected from the group consisting of glycol, propanediol, butanediol, pentanediol, hexanediol, cyclohexanediol, cyclohexyldimethanol, octanediol, neopentyl glycol, diethylene glycol, triethylene glycol, trimethylpentanediol, benzenedimethanol, benzenediol, methylbenzenediol, bisphenol A, poly(butanediol-co-adipate) glycol, poly(hexanediol-co-adipate) glycol, poly(ethanediol-co-adipate) glycol, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, preferably butanediol.

[0069] The polyol component preferably has a number-average molecular weight M n , determined according to test method 1, in a range from 60 to 50,000 g / mol, more preferably in a range from 400 to 10,000 g / mol, more preferably in a range from 400 to 6,000 g / mol. Further details regarding the blowing agent layer are disclosed in DE102020210503A1.

[0070] Preferably, the propellant layer according to (iii) is removable at a temperature in a range of 40 to 200 °C, more preferably in a range of 50 to 120 °C.

[0071] Furthermore, the present invention relates to a process for producing the laminate as described herein, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) is applied by direct coating or by lamination, preferably hot lamination.

[0072] The propellant layer is preferably coated directly onto the metal layer. The propellant layer can be coated onto the metal layer from either a solution or a dispersion. Doctor blade coating, nozzle coating, roller bar coating, extrusion die coating, casting die coating, and casting processes can be used to apply the propellant layer. Also within the scope of the invention are application methods such as roller coating, printing, screen printing, anilox roller coating, inkjet coating, and spraying. Application using a hot melt adhesive is possible, but care must be taken to ensure that the coating temperature is lower than the temperature required to expand the layer.

[0073] If the metal layer contains another layer, such as a plastic layer for easier processing, the propellant layer should be coated onto the metal side to achieve better heat transfer. Transfer coating, first onto a liner and then lamination onto the metal layer, is only possible if the propellant layer has a certain level of tackiness.

[0074] The pressure-sensitive adhesive layer can be produced and processed from solution or from the melt. The pressure-sensitive adhesive layer can be applied by direct coating or by lamination, particularly hot lamination. Doctor blade coating, nozzle coating, roller bar coating, extrusion die coating, casting die coating, and casting die coating can be used to apply the pressure-sensitive adhesive layer. Also within the scope of the invention are application methods such as roller coating, printing, screen printing, anilox roller coating, inkjet coating, and spraying. Hot melt processes (extrusion, nozzle coating) are preferred.

[0075] The coating can be applied directly to the metal layer or the propellant layer, or it can be coated first onto a liner and then the adhesive can be applied to the metal layer or the propellant layer by lamination.

[0076] Liners in this context can be films or papers with a non-stick coating. Siliconized films are often used as liners. Coating a liner and then laminating it to the metal or propellant layer has the advantage that neither the propellant layer nor the metal layer needs to be exposed to elevated temperatures during this process.

[0077] If necessary, additional layers or material plies are then laminated or coated inline or offline so that multi-layer product structures can also be created.

[0078] Furthermore, the present invention relates to a use of the laminate as described herein in an arrangement with at least one substrate, preferably with at least two substrates, more preferably the laminate, as described herein, is located between two substrates.

[0079] Furthermore, the present invention relates to a use of the laminate as described herein in a detachment process, wherein the detachment process comprises: - Providing an arrangement comprising a laminate as described herein and at least one substrate, preferably comprising at least two substrates, more preferably the laminate as described herein is located between two substrates; - subjecting the arrangement to inductive heating in an alternating magnetic field having a frequency in a range of 100 Hz to 200 kHz, preferably in a range of 5 kHz to 50 kHz, particularly preferably in a range of 10 kHz to 30 kHz; and - exposing the assembly to a temperature in a range of 40 to 200 °C, preferably 50 to 120 °C; and - Separating the laminate from at least one substrate, preferably from at least two substrates.

[0080] Preferably, the separation comprises an expansion of the propellant layer according to (iii).

[0081] After the laminate is separated by the expansion of the foaming agent layer, one substrate contains laminate residue with the metal layer, and the other substrate contains laminate residue without the metal layer. The remaining adhesive parts of the laminate on the side with the metal layer can be easily removed by peeling. The metal layer ensures that the laminate layers are strong enough not to tear during peeling. The special type of pressure-sensitive adhesive layer, thanks to its high cohesion, ensures that no adhesive residue remains on the substrate.

[0082] The other side, without the metal layer, can be easily removed by stretching. Stretching reduces the bond strength of the pressure-sensitive adhesive layer, including the residues of the foaming agent layer, allowing the remaining laminate residue to be removed without leaving any residue.

[0083] The ability to remove the laminate without leaving any residue eliminates the need for extensive cleaning if the substrates are to be reused. Rebonding is possible with little or no cleaning effort.

[0084] Furthermore, the separation preferably comprises an elongating stretching in the direction of the bonding plane of the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv).

[0085] Preferably, by stretching in the direction of the bonding plane, the adhesive residues of the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) can be detached from the substrate without leaving any residue or almost without leaving any residue.

[0086] Furthermore, the present invention relates to the use of the laminate as described herein in electronic devices, automobiles, medical devices and dental devices.

[0087] The present invention, as described above, is further described by the following set of embodiments and combinations of embodiments, wherein the combinations result from the corresponding dependencies and references. In particular, it should be noted that in those places where a range of embodiments is mentioned—for example, in connection with an expression such as "laminate according to any one of embodiments 1 to 5"—each individual embodiment in this range is explicitly disclosed to the person skilled in the art, and this expression is therefore understood by the person skilled in the art as synonymous with the expression "laminate according to any one of embodiments 1, 2, 3, 4, and / or 5."Furthermore, it should be explicitly pointed out that the following set of embodiments does not represent the set of patent claims determining the scope of protection, but rather a suitably structured part of the description directed to general and preferred aspects of the present invention. 1. Laminate comprising the following layers in the specified order: (i) a first pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes; (ii) a metal layer; (iii) a propellant layer; and (iv) a second pressure-sensitive adhesive layer comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes, wherein the metal layer according to (ii) can be inductively heated to a temperature in a range from 50 to 200 °C in a magnetic field of a frequency in a range from 100 Hz to 200 kHz. 2. Laminate according to embodiment 1, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) comprises an elastomer component (a), an adhesive resin component (b) and optionally a soft resin component (c), preferably an elastomer component (a), an adhesive resin component (b) and a soft resin component (c). 3. Laminate according to embodiment 2, wherein the elastomer component according to (a) is a block copolymer having a structure ABA, (AB) n , (AWAY) n X or (ABA) nX, preferably a diblock copolymer AB and / or a triblock copolymer ABA, wherein - the blocks A independently of one another form a polymer preparable from a polymerization mixture containing vinylaromatic monomers having 8 to 12 C atoms; - the blocks B independently of one another form a polymer producible from a polymerization mixture containing alkene monomers having 4 to 18 C atoms; - X comprises a residue of a coupling reagent or initiator and - n ≥ 2. 4. Laminate according to embodiment 3, wherein the blocks A can be produced from a polymerization mixture containing styrene and α-methylstyrene, preferably from a polymerization mixture containing styrene. 5. Laminate according to embodiment 3 or 4, wherein the blocks B are producible from a polymerization mixture containing monomers of 1,3-diene and isobutylene, preferably producible from a polymerization mixture containing butadiene and / or isoprene. 6. Laminate according to one of embodiments 3 to 5, wherein the blocks A have a proportion in the block copolymer in a range from 14 to 35 wt.%, preferably in a range from 14 to 30 wt.%. 7. Laminate according to any one of embodiments 3 to 6, wherein the blocks B have a proportion in the block copolymer in a range of 65 to 86 wt.%. 8. Laminate according to any one of embodiments 2 to 7, wherein the adhesive resin component according to (b) has a weight-average molecular weight M w , determined according to test method 1 in a range of 400 to 15,000 g / mol, preferably in a range of 400 to 5,000 g / mol, more preferably in a range of 500 to 2,000 g / mol. 9. Laminate according to any one of embodiments 2 to 8, wherein the adhesive resin component according to (b) comprises one or more materials selected from the group consisting of non-hydrogenated, partially or fully hydrogenated resins based on rosin or rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively or fully hydrogenated hydrocarbon resins based on C-5, C-5 / C-9 or C-9 monomer mixtures and polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene. 10. Laminate according to any one of embodiments 2 to 9, wherein the soft resin component according to (c) has a softening temperature of < 30 °C, determined according to test method 2. 11. Laminate according to any one of embodiments 2 to 10, wherein the soft resin component according to (c) comprises a rosin-, hydrocarbon- or polyterpene-based soft resin. 12. Laminate according to any one of embodiments 2 to 11, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) comprises the soft resin component according to (c) in a range from 0.1 to 15 wt.%, preferably in a range from 2 to 10 wt.%. 13. Laminate of any of embodiments 1 to 12, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) additionally comprises additives (d). 14. Laminate according to embodiment 13, wherein the additive according to (d) comprises one or more materials selected from the group consisting of light stabilizers, flame retardants, fillers, dyes, pigments, plasticizers, antioxidants, process stabilizers, processing aids and endblock reinforcing resins. 15. Laminate according to one of embodiments 1 to 14, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) has a thickness in a range from 25 to 3000 µm, preferably in a range from 50 to 1000 µm. 16. Laminate according to any one of embodiments 1 to 15, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) is a pressure-sensitive adhesive layer that can be redetached by stretching in the direction of the bonding plane. 17. Laminate according to any one of embodiments 1 to 16, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) has an elongation at break of at least 100%, determined according to test method 3, and a resilience of more than 50%, determined according to test method 4. 18. Laminate according to any one of embodiments 1 to 17, wherein the metal layer according to (ii) comprises one or more materials selected from the group consisting of aluminum, copper, nickel, iron and steel, preferably aluminum and copper. 19. Laminate according to any one of embodiments 1 to 18, wherein the metal layer according to (ii) has a thickness in a range from 1 to 200 µm, preferably in a range from 5 to 100 µm. 20. Laminate according to any one of embodiments 1 to 19, wherein the metal layer according to (ii) additionally comprises a carrier, wherein the carrier comprises one or more materials selected from the group consisting of polyethylene terephthalate, polyethylene and polypropylene, preferably polyethylene terephthalate. 21. Laminate according to any one of embodiments 1 to 20, wherein the metal layer according to (ii) can be inductively heated to a temperature in a range from 70 to 180 °C, in a magnetic field with a frequency in a range from 5 kHz to 50 kHz, particularly preferably in a range from 10 kHz to 30 kHz, further preferably for a period of time in a range from 1 to 20 s, particularly preferably in a range from 5 to 15 s. 22. Laminate according to any one of embodiments 1 to 21, wherein the blowing agent layer according to (iii) comprises one or more materials selected from the group consisting of azo compounds, hydrazine compounds, sulfonyl semicarbazide compounds, sulfonyl semicarbazide compounds, tetrazole compounds, N-nitroso compounds and carbonate compounds. 23. Laminate according to any one of embodiments 1 to 22, wherein the blowing agent layer according to (iii) comprises expandable, thermoplastic microspheres. 24. The laminate of embodiment 23, wherein the expandable thermoplastic microspheres comprise a thermoplastic polymer shell and a blowing agent encased therein. 25. Laminate according to any one of embodiments 1 to 24, wherein the propellant layer according to (iii) has a thickness in a range from 10 to 150 µm, preferably in a range from 25 to 100 µm. 26. Laminate according to any one of embodiments 1 to 25, wherein the blowing agent layer according to (iii) comprises at least 50 wt.%, preferably at least 90 wt.% of a thermoplastic polyurethane. 27. The laminate according to embodiment 26, wherein the thermoplastic polyurethane comprises at least one polyisocyanate component and at least one polyol component. 28. The laminate according to embodiment 26 or 27, wherein the thermoplastic polyurethane comprises a thermoplastic polyurethane dispersion. 29. Laminate according to any one of embodiments 26 to 28, wherein the thermoplastic polyurethane is preparable from a polymerization mixture comprising at least one diisocyanate, at least one polyester polyol and optionally at least one alkanediol. 30. Laminate according to embodiment 29, wherein the at least one diisocyanate is selected from the group consisting of toluene diisocyanate (TDI), p-

[0088] Phenylene diisocyanate (PPDI), 4,4'-diphenylmethane diisocyanate (MDI), p,p'-bisphenyl diisocyanate (BPDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), or 4,4'-diisocyanatodicyclohexylmethane (H12MDI), preferably toluene diisocyanate (TDI). 31. Laminate according to any one of embodiments 27 to 30, wherein the polyisocyanate component has a number-average molecular weight M n, determined according to test method 1, in a range of 60 to 50,000 g / mol, preferably in a range of 400 to 10,000 g / mol, more preferably in a range of 400 to 6,000 g / mol. 32. Laminate according to any one of embodiments 27 to 31, wherein the polyol component comprises one or more materials selected from the group consisting of alkanediols, polyetherdiols, polyesterdiols, polycarbonatediols, polycaprolactone polyols and polyacrylate polyols, preferably polyetherdiols, polyesterdiols and polycarbonatediols. 33. Laminate according to embodiment 32, wherein the polyol component comprises one or more materials selected from the group consisting of glycol, propanediol, butanediol, pentanediol, hexanediol, cyclohexanediol, cyclohexyldimethanol, octanediol, neopentyl glycol, diethylene glycol, triethylene glycol, trimethylpentanediol, benzenedimethanol, benzenediol, methylbenzenediol, bisphenol A, poly(butanediol-co-adipate) glycol, poly(hexanediol-co-adipate) glycol, poly(ethanediol-co-adipate) glycol, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, preferably butanediol. 34. Laminate according to any one of embodiments 27 to 33, wherein the polyol component has a number average molecular weight M n , determined according to test method 1 in a range of 60 to 50,000 g / mol, preferably in a range of 400 to 10,000 g / mol, more preferably in a range of 400 to 6,000 g / mol. 35. Laminate according to any one of embodiments 1 to 34, wherein the propellant layer according to (iii) is removable at a temperature in a range from 40 to 200 °C, preferably from 50 to 120 °C. 36. A process for producing the laminate according to any one of claims 1 to 35, wherein the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) is applied by direct coating or by lamination, preferably hot lamination. 37. Use of the laminate according to any one of embodiments 1 to 35 in an arrangement with at least one substrate, preferably with at least two substrates, more preferably the laminate according to any one of embodiments 1 to 36 is located between two substrates. 38. Use of the laminate according to any one of embodiments 1 to 35 in a detachment process, wherein the detachment process comprises: - Providing an arrangement with a laminate according to one of embodiments 1 to 35 and at least one substrate, preferably with at least two substrates, more preferably the laminate according to one of embodiments 1 to 35 is located between two substrates; - subjecting the arrangement to inductive heating in an alternating magnetic field having a frequency in a range of 100 Hz to 200 kHz, preferably in a range of 5 kHz to 50 kHz, particularly preferably in a range of 10 kHz to 30 kHz; and - exposing the assembly to a temperature in a range of 40 to 200 °C, preferably in a range of 50 to 120 °C; and - Separating the laminate from at least one substrate, preferably from at least two substrates. 39. Use according to embodiment 38, wherein the separating comprises an expansion of the propellant layer according to (iii). 40. Use according to embodiment 39, wherein the separating comprises an elongating stretching in the direction of the bonding plane of the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv). 41. Use according to embodiment 40, wherein the adhesive residues of the first pressure-sensitive adhesive layer according to (i) and / or the second pressure-sensitive adhesive layer according to (iv) can be detached from the substrate without leaving any residue or almost without leaving any residue by the stretching in the direction of the bonding plane. 42. Use of the laminate according to any one of embodiments 1 to 35 in electronic devices, automobiles, medical devices and dental devices. Short description of the characters

[0089] Further details and features of the present invention will become apparent from the description of the figures and exemplary embodiments. The respective features can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. The exemplary embodiments are illustrated schematically in the figures. The same reference numerals in the individual figures designate identical or functionally identical elements, or elements that correspond to one another in terms of their functions.

[0090] In detail: Fig. 1: a laminate according to an embodiment of the present invention comprising a first pressure-sensitive adhesive layer 11, a metal layer 12, a propellant layer 13 and a second pressure-sensitive adhesive layer 14; Fig.2: an arrangement according to an embodiment of the present invention comprising two substrates 10 and 15, a first pressure-sensitive adhesive layer 11, a metal layer 12, a propellant layer 13 and a second pressure-sensitive adhesive layer 14; Fig. 3: a method for detaching the laminate, wherein the separation between the metal layer 12 and the propellant layer 13 takes place in a magnetic field; Description of the embodiments

[0091] Further details and features of the present invention will become apparent from the description of exemplary embodiments. The respective features can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. Test methods:Test method 1: Molecular weight M n and M w

[0092] The number average molecular weight M nor weight-average molecular weight M w in this document refer to the determination by gel permeation chromatography (GPC). The determination is carried out on 100 µl of a clear-filtered sample (sample concentration 3 g / l). Tetrahydrofuran with 0.1 vol.% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C. The pre-column used is a PSS-SDV column, 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 the separation, a combination of the PSS-SDV columns, 5 µm, 10 3 Å and 10 5 Å and 10 6Å columns with a diameter of 8.0 mm x 300 mm each were used (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate was 1.0 ml per minute. Calibration was performed against PMMA standards (polymethyl methacrylate calibration) for polar molecules, such as the starting materials for polyurethane, and against PS standards (polystyrene calibration) for other molecules. Test method 2: Softening temperature

[0093] The softening temperature is determined according to the relevant methodology known as Ring & Ball, standardized according to ASTM E28, version ASTM E28-18. Test method 3: Elongation at break

[0094] The elongation at break was measured in accordance with DIN 53504 (2017-03) using S3-sized shoulder bars at a separation speed of 300 mm per minute. The test conditions were 23 °C and 50% relative humidity. Test method 4: resilience

[0095] To measure resilience, the pressure-sensitive adhesive strips were stretched to 100%, held at this stretch for 30 seconds, and then relaxed. After a waiting time of 1 minute, the length was measured again.

[0096] The resilience is now calculated as follows: RV=((L100−Lend) / L0)*100 with RV = resilience in % L 100 : Length of the adhesive strip after stretching by 100% L0: Length of the adhesive strip before stretching L end : Length of the adhesive strip after relaxation of 1 min.

[0097] The resilience corresponds to the elasticity. Test method 5: Glass transition temperature T g

[0098] The glass transition temperature of polymers is determined using dynamic scanning calorimetry (DSC). For this purpose, approximately 5 mg of the untreated polymer sample is weighed into an aluminum crucible (volume 25 µL) and sealed with a perforated lid. A Netzsch DSC 204 F1 is used for the measurement and operated under nitrogen for inerting. The sample is first cooled to -150 °C, heated at a heating rate of 10 K / min to +150 °C, and then cooled again to -150 °C. The subsequent second heating curve is run at 10 K / min, and the change in heat capacity is recorded. Glass transitions are recognized as steps in the thermogram. The glass transition temperature is evaluated as follows: A tangent is drawn to the baseline of the thermogram before and after step 1 of the step.In the step area, a best-fit line 3 is placed parallel to the ordinate so that it intersects the two tangents, creating two areas 4 and 5 (between the tangent, the best-fit line, and the measured curve) of equal area. The intersection point of the best-fit line positioned in this way with the measured curve gives the glass transition temperature. Test method 6: Push-out test (z-plane)

[0099] The push-out test provides information about how resistant the bonding of a component is in a frame-shaped body, such as a window or a display in a housing.

[0100] A rectangular, frame-shaped sample was cut out of the adhesive tape to be tested (external dimensions 33 mm × 33 mm; edge width 2.0 mm each; internal dimensions (window opening) 29 mm × 29 mm, adhesive surface 248 mm 2on the top and bottom sides, respectively). This sample was bonded to a rectangular PC plastic frame (PC = polycarbonate) (external dimensions 40 mm × 40 mm; edge width of the long edges 8 mm each; edge width of the short edges 10 mm each; internal dimensions) (window opening 24 mm × 24 mm; thickness 3 mm). A rectangular PC film measuring 35 mm × 35 mm was bonded to the other side of the double-sided adhesive tape sample. The full adhesive surface of the available adhesive tape was utilized. The PC frame, adhesive tape sample, and PC window were bonded such that the geometric centers, the angle bisectors of the acute diagonals, and the angle bisectors of the obtuse diagonals of the rectangles were aligned (corner to corner, long sides to long sides, short sides to short sides). The bonding area was 248 mm 2The bond was pressed with 248 N for 5 s and stored for 24 hours under conditioning at 23°C / 50% relative humidity.

[0101] Immediately after storage, the adhesive composite consisting of PC frame, adhesive tape and PC window was placed with the protruding edges of the PC frame onto a frame construction (sample holder) in such a way that the composite is horizontal and the PC window is oriented downwards, freely hanging.

[0102] A pressure piece is then moved vertically from above at a constant speed of 10 mm / s through the window of the PC frame, pressing centrally onto the PC plate. The respective force (determined from the respective pressure and contact area between the pressure piece and plate) is measured as a function of time from the first contact of the pressure piece with the PC plate until shortly after the plate falls (measurement conditions: 23 °C, 50% relative humidity). The response of the push-out test is the force acting immediately before the failure of the adhesive bond between the PC plate and the PC frame (maximum force F max in the force-time diagram in N). Materials used: Elastomer component: Kraton D1152: Styrene-butadiene-styrene elastomer consisting mainly of 2 and 3 styrene-butadiene blocks with a styrene content of 30% and a 2-block content of 15%, from Kraton Europrene Sol T 190: Styrene-isoprene-styrene block copolymer consisting mainly of 2- and 3-blocks of styrene-isoprene with a styrene content of 16% and a 2-block content of 25% from Versalis Adhesive resin component: Dercolyte A 115: Terpene resin consisting mainly of alpha-pinene with a softening point of 115°C available from DRT Foralyn 110: Rosin resin with a softening point of 110°C available from Eastman Regalite R 1100: Hydrogenated C9-based hydrocarbon resin with a softening point of 100°C available from Eastman Soft resin component: Wingtack 10: Liquid resin based on non-hydrogenated hydrocarbons available from Goodyear Plasticizers: TerPib 2600:TerHell Low molecular weight liquid polyisobutylene distributed by Antioxidants: Irganox 1010: Primary antioxidant from BASF Polyurethane dispersion: Impranil DL 116: anionically stabilized polyester PU dispersion from Covestro Microspheres: Expancel 920 DU20: expandable, thermoplastic microspheres (microballoons) with a size after expansion of approximately 20µm from Nuryon Examples:Example 1:

[0103] The following materials are used as adhesive for the first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer: 48.5 wt% Kraton D 1152 48.5 wt.% Dercolyte A 115 2.5 wt% Wingtack 10 0.5 wt% Irganox 1010.

[0104] The materials shown above are dissolved in toluene, adjusting the solids content to 35 wt.%. The resulting mixture is then spread onto a PET liner coated with a silicone release agent using a spreader bar, resulting in a layer thickness of 50 µm after drying at 110 °C.

[0105] The following materials are used to produce the propellant layer: PU dispersion Impranil DL 1116 99.5% by weight Thickener Borchi Gel 0625 0.5% by weight.

[0106] The polyurethane dispersion is mixed with the thickener using a conventional vertical stirring apparatus with a Visco Jet stirrer.

[0107] Impranil DL 1116 (99.5 wt.%) and the thickener Borchi Gel 0625 (0.5 wt.%) are placed in a container and stirred gently. The formation of whirlpools or any incorporation of air should be avoided throughout the mixing process. Once a homogeneous mixture has been achieved, 20 parts of unexpanded microspheres (microballoons) (Expancel 920 DU20) are added to 100 parts of dispersion (calculated on a solid basis), with the addition taking place as a slurry in water. Production of the laminate:

[0108] The resulting mixture is then spread onto a composite of 12 µm aluminum and 12 µm PET with a doctor blade and dried, coating the aluminum side of the composite. After drying at 110 °C, at which the microballoons are not yet expanded, a layer thickness of 30 µm is achieved.

[0109] The adhesive for the pressure-sensitive adhesive layer is then laminated to both the polyurethane side of the blowing agent layer and the PET side of the newly formed composite. This creates a double-sided adhesive laminate with a layer thickness of approximately 155 µm.

[0110] This laminate is bonded between two PC (polycarbonate) surfaces as described under Push-Out Test.

[0111] The push-out force is then measured.

[0112] The laminate between the two PC plates is then stored in a magnetic field at 25 kHz for 10 s.

[0113] The sample is then removed and the push-out force is measured again.

[0114] The results are summarized in Table 1.

[0115] After separating the two substrates, the remaining adhesive residues can be easily removed. The break occurs between the PU layer (propellant layer) and the aluminum layer. The remnants of the laminate with the aluminum layer can be easily removed by peeling, leaving no adhesive residue on the PC substrate.

[0116] The other side can be easily removed by stretching the remaining adhesive residues of the pressure-sensitive adhesive layer, including the polyurethane of the foaming agent layer, starting from one corner. Here, too, the residues can be removed without leaving any residue, allowing the PC bodies to be reused without cleaning. Example 2:

[0117] The following materials are used as adhesive for the first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer: 50 wt.% Europrene Sol T 190 47% by weight Foralyn 110 2.5 wt% TerPib 2600 0.5 wt% Irganox 1010. The materials shown above are dissolved in toluene, adjusting the solids content to 40 wt.%. The resulting mixture is then spread onto a PET liner coated with a silicone release agent using a spreader bar, resulting in a layer thickness of 50 µm after drying at 110 °C.

[0118] The propellant layer is the same as in Example 1.

[0119] The resulting mixture is then spread onto a 20 µm-thick aluminum foil with a doctor blade and dried. After drying at 110 °C, at which the microspheres (microballoons) are not yet expanded, a layer thickness of 30 µm is achieved.

[0120] The adhesive for the pressure-sensitive adhesive layer is then laminated to both the polyurethane side of the foaming agent layer and the aluminum side of the newly formed composite. This creates a double-sided adhesive laminate with a layer thickness of approximately 150 µm.

[0121] This laminate is bonded between two PC (polycarbonate) surfaces as described under Push-Out Test.

[0122] The push-out force is then measured.

[0123] The laminate between the two PC plates is then stored in a magnetic field at 30 kHz for 5 s.

[0124] The sample is then removed and the push-out force is measured again.

[0125] The results can be found in Table 1.

[0126] After separating the two substrates, the remaining adhesive residues can be easily removed. The break occurs between the PU layer (propellant layer) and the aluminum layer. The remnants of the laminate with the aluminum layer can be easily removed by peeling, leaving no adhesive residue on the PC substrate.

[0127] The other side can be easily removed by stretching the remaining adhesive residues of the pressure-sensitive adhesive layer, including the polyurethane of the foaming agent layer, starting from one corner. Here, too, the residues can be removed without leaving any residue, allowing the PC bodies to be reused without cleaning. Example 3:

[0128] The following materials are used as adhesive for the first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer: 24 wt% Kraton D1152 24 wt. % Europrene Sol T 190 49 wt% Regalite R 1100 2.5 wt% Wingtack 10 0.5 wt% Irganox 1010.

[0129] The materials described above are dissolved in toluene, adjusting the solids content to 35 wt.%. The resulting mixture is then spread onto a PET liner coated with a silicone release agent using a spreader bar, resulting in a layer thickness of 50 µm after drying at 110 °C.

[0130] The same materials are used to produce the propellant layer as in the previous examples, but only 15 parts of unexpanded microspheres (microballoons) (Expancel 920 DU20) are added.

[0131] The resulting mixture is then spread onto a composite of 12 µm aluminum and 12 µm PET with a doctor blade and dried, coating the aluminum side of the composite. After drying at 110 °C, at which the microballoons are not yet expanded, a layer thickness of 30 µm is achieved.

[0132] The adhesive is then laminated to both the polyurethane side of the propellant layer and the PET side of the newly formed composite. This creates a double-sided adhesive laminate with a layer thickness of approximately 155 µm.

[0133] This laminate is again glued between two PC (polycarbonate) surfaces as described in the push-out test.

[0134] The push-out force is then measured.

[0135] The laminate between the two PC plates is then stored in a magnetic field at 30 kHz for 10 s.

[0136] The sample is then removed and the push-out force is measured again.

[0137] The results are summarized in Table 1.

[0138] After separating the two substrates, the remaining adhesive residues can be easily removed. The break occurs between the PU layer (propellant layer) and the aluminum layer. The remnants of the laminate with the aluminum layer can be easily removed by peeling, leaving no adhesive residue on the PC substrate.

[0139] The other side can be easily removed by stretching the remaining adhesive residues of the pressure-sensitive adhesive layer, including the polyurethane of the foaming agent layer, starting from one corner. Here, too, the residues can be removed without leaving any residue, allowing the PC bodies to be reused without cleaning. Comparison examples:Comparison example V1:

[0140] As in example 1, but using an acrylate adhesive instead of an adhesive based on vinyl aromatic block copolymers.

[0141] A reactor conventional for radical polymerizations is charged with 47.5 kg of 2-ethylhexyl acrylate, 47.5 kg of n-butyl acrylate, 5 kg of acrylic acid, and 66 kg of benzine / acetone (70 / 30). After 45 minutes of nitrogen gas flow with stirring, the reactor is heated to 58 °C, and 50 g of AIBN is added. The external heating bath is then heated to 75 °C, and the reaction is carried out at this constant external temperature. After 1 h, another 50 g of AIBN is added, and after 4 h, the reaction is diluted with 20 kg of benzine / acetone. After 5.5 and 7 h, the reaction is reinitiated with 150 g of bis(4-tert-butylcyclohexyl)peroxydicarbonate. After a reaction time of 22 h, the polymerization is terminated, and the reaction is cooled to room temperature. The polyacrylate has an average molecular weight of Mw = 386,000 g / mol and a polydispersity of PD (Mw / Mn) of 7.6. A 50 µm layer is applied.

[0142] The composite of adhesive, metal layer (with PET), expandable propellant layer and adhesive is produced again as described in Example 1.

[0143] After bonding between the two PC substrates, the push-out force of the composite is measured again before and after applying a magnetic field.

[0144] After removing the bond, the adhesive residue isn't as easy to remove this time. When peeling one side, adhesive residue remains on the substrate. Removing it by stretching the other side isn't possible, as a lot of adhesive residue remains there as well. Comparison example V2:

[0145] As example 1, except that no microballoons are incorporated into the polyurethane layer.

[0146] This shows that the reduction in push-out force is significantly lower than in example 1. If the push-out value is too high, it can happen that a component is bent or otherwise damaged when it is removed. Comparison example V3:

[0147] As in example 1, but without the aluminum layer. Pure PET is used as the carrier.

[0148] In this case, the tape does not heat up and the push-out force is not reduced by the magnetic field.

[0149] The following Table 1 shows the results of the measured push-out force. Example Push-out after bonding [N] Push-out after exposure to the magnetic field [N] Removability of adhesive tape residue 1 74,4 18,3 No residue 2 63,8 15,0 No residue 3 70,9 20,5 No residue V1 62,6 19,1 Heavy residues V2 72,8 55,0 No residue V3 76,8 75,9 No residue

[0150] Examples 1 to 3 demonstrate that high bond strength can be achieved, as evidenced by the high values ​​in the push-out test after bonding. The effect of the magnetic field (induction) and the expansion of the blowing agent layer can significantly reduce the bond strength. A force of less than 30 N is advantageous to prevent deformation of the components during separation. In all three examples 1 to 3, the laminate residues could be easily removed without residue by peeling or stretching.

[0151] In contrast, comparative example 1 shows that the use of a different adhesive, in this case an acrylate adhesive, can lead to the fact that, despite easy separation of the bond, residue-free removal of the adhesive tape residues is not possible.

[0152] Comparative Example 2 shows that the foaming agent layer is necessary for a significant reduction in bond strength. While the push-out force decreases slightly as the adhesives are heated and thus softened, the push-out force is significantly higher than 30 N, posing a risk of damage to the bonded substrates or components.

[0153] Comparative Example 3 shows that without a metal layer, the induction has no effect and the bonding strength cannot be reduced by the magnetic field. List of reference symbols 10 first substrate 11 first adhesive layer 12 metal layer 13 Propellant layer 14 second adhesive layer 15 second substrate

Claims

[1] Laminate comprising the following layers in the given order: (i) a first pressure-sensitive adhesive layer (11) comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes; (ii) a metal layer (12); (iii) a propellant layer (13); and (iv) a second pressure-sensitive adhesive layer (14) comprising a block copolymer containing at least one polymer block formed from vinyl aromatics and at least one polymer block formed from alkenes, wherein the metal layer (12) according to (ii) can be inductively heated to a temperature in a range from 50 to 200 °C in a magnetic field with a frequency in a range from 100 Hz to 200 kHz. [2] Laminate according to claim 1, wherein the first pressure-sensitive adhesive layer (11) according to (i) and / or the second pressure-sensitive adhesive layer (14) according to (iv) comprises an elastomer component (a), an adhesive resin component (b) and optionally a soft resin component (c), preferably an elastomer component (a), an adhesive resin component (b) and a soft resin component (c). [3] Laminate according to claim 2, wherein the elastomer component according to (a) is a block copolymer having a structure ABA, (AB) n , (AWAY) n X or (ABA) n X, preferably a diblock copolymer AB and / or a triblock copolymer ABA, wherein - the blocks A independently of one another form a polymer preparable from a polymerization mixture containing vinylaromatic monomers having 8 to 12 C atoms; - the blocks B independently of one another form a polymer producible from a polymerization mixture containing alkene monomers having 4 to 18 C atoms; - X is a residue of a coupling reagent or initiator and - n ≥ 2, include. [4] Laminate according to claim 3, wherein the blocks A can be produced from a polymerization mixture containing styrene and α-methylstyrene, preferably from a polymerization mixture containing styrene. [5] Laminate according to claim 3 or 4, wherein the blocks B can be prepared from a polymerization mixture containing monomers of 1,3-dienes and isobutylene, preferably from a polymerization mixture containing butadiene and / or isoprene. [6] Laminate according to one of claims 3 to 5, wherein the blocks A have a proportion in the block copolymer in a range of 14 to 35 wt.%, preferably in a range of 14 to 30 wt.%, and / or wherein the blocks B have a proportion in the block copolymer in a range of 65 to 86 wt.%. [7] Laminate according to one of claims 1 to 6, wherein the first pressure-sensitive adhesive layer (11) according to (i) and / or the second pressure-sensitive adhesive layer (14) according to (iv) has a thickness in a range of 25 to 3000 µm, preferably in a range of 50 to 1000 µm. [8] Laminate according to one of claims 1 to 7, wherein the first pressure-sensitive adhesive layer (11) according to (i) and / or the second pressure-sensitive adhesive layer (14) according to (iv) is a pressure-sensitive adhesive layer which can be redetached by stretching in the direction of the bonding plane. [9] Laminate according to one of claims 1 to 8, wherein the metal layer (12) according to (ii) comprises one or more materials selected from the group consisting of aluminum, copper, nickel, iron and steel, preferably aluminum and copper. [10] Laminate according to one of claims 1 to 9, wherein the metal layer (12) according to (ii) can be inductively heated to a temperature in a range of 70 to 180 °C, in a magnetic field of a frequency in a range of 5 kHz to 50 kHz, particularly preferably in a range of 10 kHz to 30 kHz, further preferably for a time period in a range of 1 to 20 s, particularly preferably in a range of 5 to 15 s. [11] Laminate according to one of claims 1 to 10, wherein the blowing agent layer (13) according to (iii) comprises expandable thermoplastic microspheres. [12] Laminate according to one of claims 1 to 11, wherein the blowing agent layer (13) according to (iii) comprises at least 50 wt.%, preferably at least 90 wt.% of a thermoplastic polyurethane. [13] A process for producing the laminate according to any one of claims 1 to 12, wherein the first pressure-sensitive adhesive layer (11) according to (i) and / or the second pressure-sensitive adhesive layer (14) according to (iv) is applied by direct coating or by lamination, preferably hot lamination. [14] Use of the laminate according to one of claims 1 to 12 in an arrangement with at least one substrate (10), preferably with at least two substrates (10, 15), more preferably the laminate according to one of claims 1 to 12 is located between two substrates (10, 15). [15] Use of the laminate according to any one of claims 1 to 12 in a release process, the release process comprising: - Providing an arrangement with a laminate according to one of claims 1 to 12 and at least one substrate (10), preferably with at least two substrates (10, 15), more preferably the laminate according to one of claims 1 to 12 is located between two substrates (10, 15); - subjecting the arrangement to inductive heating in an alternating magnetic field having a frequency in a range of 100 Hz to 200 kHz, preferably in a range of 5 kHz to 50 kHz, particularly preferably in a range of 10 kHz to 30 kHz; and - exposing the assembly to a temperature in a range of 40 to 200 °C, preferably in a range of 50 to 120 °C; and - separating the laminate from at least one substrate (10), preferably from at least two substrates (10, 15). [16] Use of the laminate according to any one of claims 1 to 12 in electronic devices, automobiles, medical devices and dental devices.

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