Hardenable adhesive strip based on vinyl aromatic block copolymer

Description

[0001] The invention relates to an adhesive strip based on vinyl aromatic block copolymer, which can be hardened by electron beams and which is particularly suitable for bonding components with a non-polar surface.

[0002] Adhesives and tapes are generally used to join two substrates, creating a durable or permanent bond. Despite the wide variety of adhesives and tapes available, the emergence of new substrates and increasing end-application requirements necessitate the development of new pressure-sensitive adhesives, formulations, and tape designs. For example, it has been found that new automotive interior components, to which adhesive tapes are required to adhere temporarily or permanently, have critical surfaces and pose a bonding challenge. Due to the low surface energy of these components, adhesive tapes specifically developed for these applications are needed.

[0003] The use of adhesive tapes continues to increase due to the ongoing trend in the transport sector, and especially in the automotive industry, to further reduce the weight of vehicles, for example, and thus lower fuel consumption. This leads to adhesive tapes being used for applications for which previous adhesive tape products were neither intended nor developed. In addition to mechanical stress and the challenging substrates for adhesive applications, there are also increasing demands, particularly for permanent bonds, regarding UV and weather resistance.

[0004] Consequently, adhesive tape products must exhibit improved adhesion to low-energy surfaces and maintain excellent performance even under extreme climatic conditions. In particular, the automotive industry demands sufficient cohesion even at high temperatures for permanent exterior bonding (emblems, shock absorbers) as well as permanent interior bonding (doors).

[0005] In addition, the adhesive tape must also meet the demands of the manufacturing processes. Due to the increasing automation of production processes and the desire for more economical manufacturing methods, the adhesive tape, once placed in the correct position, must quickly exhibit sufficiently high adhesion and, in some cases, withstand high shear forces even at this early stage. For this purpose, it is advantageous if the adhesive tapes have a high tack and the adhesive mass releases quickly on various substrates, so that good wetting and thus high adhesive strength are achieved in a very short time.

[0006] Since the last point, namely a tendency to flow quickly onto various surfaces and thus the rapid achievement of constant adhesive strength, is difficult to attain with resin-modified acrylate or pure acrylate pressure-sensitive adhesives, synthetic rubbers or blends containing synthetic rubbers are frequently described as suitable materials for bonding to non-polar surfaces. EP 0 349 216 A1 and EP 0 352 901 A1 describe two-phase blends consisting of a polyacrylate and a synthetic rubber, preferably a styrene block copolymer, which are particularly recommended for bonding to paints and varnishes. However, multi-phase blend systems can have the disadvantage that the morphology of the blend can change over time and / or with increasing temperature, which manifests itself in a macroscopic change in the polymer or product properties.Furthermore, in extreme cases, complete separation of the polymer components can occur, and some blend components can accumulate on surfaces over time, which can alter adhesion. Since considerable effort is generally required, for example through the use of compatibilizers as disclosed in US 6,379,791 A, to produce thermally and long-term stable blends for adhesive applications, these blend systems are not advantageous.

[0007] EP 2 226 369 A1 describes an adhesive tape comprising a viscoelastic acrylic foam carrier laminated with at least one layer of pressure-sensitive adhesive. The adhesive is based on a chemically cross-linked rubber, preferably a synthetic rubber cross-linked by electron beam curing. The tapes described therein exhibit good adhesion to various paint and varnish layers as well as sufficient cohesion at high temperatures. However, it is clearly evident that these tapes exhibit pronounced stretching behavior, meaning that the required high final strengths are only achieved after several days. Therefore, such an adhesive tape is not suitable for rapid manufacturing processes.

[0008] EP 2832780 A1 relates to a pressure-sensitive adhesive foam containing a rubber-based elastomeric material, at least one hydrocarbon adhesive resin, and at least one crosslinking additive selected from the group of multifunctional (meth)acrylate compounds. EP 2832779 A1 relates to a pressure-sensitive adhesive foam containing a rubber-based elastomeric material and at least one hydrocarbon adhesive resin with a volatile organic compound (VOC) value of less than 1000 ppm and a volatile fogging compound (FOG) value of less than 1500 ppm. US 2014 / 0234612 A1 relates to a pressure-sensitive adhesive tape with an acrylic foam carrier and rubber-based adhesive layers on both sides of the carrier, which have a gel content of 40% or more.

[0009] WO 00 / 06637 A1 relates to an article containing a polymer foam with a substantially smooth surface having an Ra value of less than 75 micrometers, wherein the foam contains a plurality of microspheres, at least one of which is an expandable polymer microsphere.

[0010] Foamed pressure-sensitive adhesive systems have been known for some time and are described in the prior art. They have, for example, lower densities than comparable non-foamed systems and are typically characterized by non-destructive removability and repositionability. Polymer foams can generally be produced in two ways. Firstly, by the action of a blowing agent, either added as such or resulting from a chemical reaction; secondly, by incorporating hollow spheres into the material matrix. Foams produced in the latter way are called syntactic foams. In a syntactic foam, hollow spheres such as glass or ceramic hollow spheres (microspheres) or microballoons are embedded in a polymer matrix.In syntactic foams, the cavities are separated from one another, and the substances (gas, air) within these cavities are separated from the surrounding matrix by a membrane. Foams made with microhollow spheres are characterized by a defined cell structure with a uniform size distribution of the foam cells. Microhollow spheres produce closed-cell foams without cavities, which, compared to open-cell variants, offer, among other things, better sealing against dust and liquids. Furthermore, chemically or physically foamed materials are more susceptible to irreversible collapse under pressure and temperature and often exhibit lower cohesive strength. Particularly advantageous properties can be achieved when expandable microspheres (also known as "microballoons") are used for foaming.Due to their flexible, thermoplastic polymer shell, such foams possess a higher adaptability than those filled with non-expandable, non-polymeric microspheres (e.g., glass spheres). They are better suited to compensating for manufacturing tolerances, which are common in injection-molded parts, and, due to their foam-like nature, can also better compensate for thermal stresses.

[0011] DE 10 2008 004 388 A1 relates to an adhesive compound containing expanded microballoons, wherein the adhesive strength of the adhesive compound containing the expanded microballoons is reduced by at most 30%, preferably at most 20%, particularly preferably 10%, compared to the adhesive strength of an adhesive compound with identical basis weight and formulation, which has been defoamed by destroying the cavities created by the expanded microballoons.

[0012] DE 10 2012 212 879 A1 relates to an adhesive compound containing at least 70 wt.%, preferably 80 wt.%, a mixture of (i) Block copolymers consisting of a mixture of block copolymers having the structure I and II I) A'-B' II) ABA, (AB) n , (AB) n X and / or (ABA) n X, where X is the residue of a coupling reagent, n is an integer between 2 and 10, A and A' is a polymer block consisting of a vinyl aromatic, B and B' is a polymer block consisting of butadiene, a mixture of butadiene and isoprene and / or a mixture of butadiene and styrene, and A and A' and B and B' may be the same or different, (ii) at least one adhesive resin, wherein the proportion of block copolymers I) is between 30 and 70 wt% based on the total amount of block copolymers, wherein the proportion A in block copolymers II) is between 25 and 40 wt%, and wherein the AB unit within at least one of the vinyl aromatic block copolymers of structure II has a molecular weight M w of greater than 65,000 g / mol and the molecular weight M w of the total block copolymer II is greater than 130,000 g / mol.

[0013] DE 10 2012 212 883 A1 relates to an adhesive tape with a carrier material made of an acrylate-based foam layer onto which at least one pressure-sensitive adhesive layer is applied, wherein the pressure-sensitive adhesive (a) is composed of a mixture of at least two different synthetic rubbers, in particular based on vinyl aromatic block copolymers, (b) contains a resin which is not soluble in the acrylates forming the foam layer and (c) is chemically uncrosslinked.

[0014] The as yet unpublished DE 10 2016 224 578 relates to a pressure-sensitive adhesive strip consisting of at least three layers, comprising an inner layer F of a non-stretchable film carrier, a layer SK1 of a self-adhesive compound arranged on one of the surfaces of the film carrier layer F and based on a microballoon-foamed vinyl aromatic block copolymer compound, and a layer SK2 of a self-adhesive compound arranged on the surface of the film carrier layer F opposite layer SK1 and based on a microballoon-foamed vinyl aromatic block copolymer compound, wherein the mean diameter of the cavities formed by the microballoons in the self-adhesive compound layers SK1 and SK2 is independently 20 to 60 µm. The pressure-sensitive adhesive strip has high shock resistance.

[0015] The also as yet unpublished DE 10 2016 224 735 relates to a pressure-sensitive adhesive strip comprising at least one SK1 layer of a self-adhesive compound based on a vinyl aromatic block copolymer foamed with microballoons, wherein the mean diameter of the cavities formed by the microballoons in the SK1 self-adhesive layer is 45 to 110 µm. The pressure-sensitive adhesive strip is characterized in particular by a high thermal shear resistance.

[0016] WO 89 / 00106 A1 relates to an adhesive tape with a carrier layer containing an electron beam-cured polymer matrix, approximately 5 to approximately 70 volume percent low-density microspheres and at least one pigment in an amount sufficient to color the tape.

[0017] US 2004 / 0131846 A1 relates to an adhesive tape comprising an electron beam-cured, rubber-based pressure-sensitive core containing polymeric microspheres and an electron beam-cured, rubber-based pressure-sensitive top layer that is substantially free of microspheres.

[0018] DE 10 2008 056 980 A1 relates to a self-adhesive compound consisting of a mixture containing (i) a polymer blend of thermoplastic and / or non-thermoplastic elastomers with at least one vinyl aromatic block copolymer containing a proportion greater than 30 wt.% of 1,2-linked dienes in the elastomer block, at least one adhesive resin, and expanded polymer microspheres. The self-adhesive compound exhibits the advantageous properties of a polymer matrix foamed with expanded microballoons. Furthermore, the vinyl aromatic block copolymer can be crosslinked in the elastomer block by electron beams. It has been shown that this radiation-chemical crosslinking improves the cohesive properties of the foamed self-adhesive compound at high temperatures, while simultaneously maintaining the adhesive properties. The proportion of 1,2-linked dienes in the elastomer block was thereby increased to greater than 30 wt.%.-% was chosen because it is known to those skilled in the art that 1,2-linked diene units (so-called vinyl groups) are more reactive. Elastomer blocks with a low proportion of 1,2-linked diene are correspondingly more difficult to crosslink. However, a disadvantage of the self-adhesive compound is that the high proportion of 1,2-linked diene in the elastomer block (greater than 30 wt%) is simultaneously accompanied by aging instabilities of the vinyl aromatic block copolymer.

[0019] DE 10 2015 220075 A1 discloses a self-adhesive strip containing at least one layer of adhesive compound having at least one elastomer component of the type of a butadiene-vinyl aromatic block copolymer, which has a gripping area at which the adhesive strip can be detached by stretching and pulling.

[0020] From WO 2019 / 020363 A1, a foamed, double-sided adhesive tape with different adhesive properties on each side is known, without the need for additional coatings. This is achieved with a web-shaped, microballoon-foamed adhesive compound containing a blend of at least one poly(meth)acrylate and at least one synthetic rubber, as well as a multitude of expandable microballoons.

[0021] EP 3 336 153 A1 describes a multi-layer pressure-sensitive adhesive system comprising: a foam layer made of special multi-arm block copolymers, polymeric plasticizers and low-emission resins (VOC < 1000 ppm) and a pressure-sensitive adhesive layer consisting of linear block copolymers, (meth)acrylate copolymers and other optional components.

[0022] The object of the present invention is therefore to provide an improved pressure-sensitive adhesive based on vinyl aromatic block copolymers which has higher aging stability and which can be used to produce a pressure-sensitive product with high thermal stability, in particular thermal shear time.

[0023] The problem is surprisingly solved according to the invention with a generic adhesive strip as described in claim 1. Accordingly, the invention relates to an adhesive strip comprising at least one layer SK1 of a self-adhesive compound based on a vinyl aromatic block copolymer and containing adhesive resin, wherein the at least one layer SK1 of the self-adhesive compound contains at least 20 to 60 wt.% of an adhesive resin, based on the total weight of the self-adhesive compound layer, wherein the vinyl aromatic block copolymer comprising at least one polymer block A formed predominantly by polymerization of vinyl aromatics and simultaneously comprising at least one polymer block B formed predominantly by polymerization of conjugated dienes, wherein the proportion of 1,2-linked conjugated diene, determined by the specified test method for <1H NMR, in block B is less than 30 wt.%, preferably less than 20 wt.% (as can be determined, for example, by <1H NMR), and at least layer SK1 has been subjected to electron irradiation with a dose of 10 to 100 kGy.

[0024] According to the invention, the self-adhesive mass of layer SK 1 is foamed.

[0025] In particular, to increase the thermal shear resistance, the SK1 layer of the adhesive strip can be subjected to electron irradiation.

[0026] Advantageous embodiments of the adhesive strip according to claim 1 and advantageous uses are set out in the further claims.

[0027] The adhesive strip according to the invention typically exhibits not only higher aging resistance but also improved mechanical properties (in particular, improved tensile-elongation properties and advantageous glass transition temperatures) as well as good adhesion to both polar and non-polar, i.e., low-energy, surfaces. After electron irradiation, it also surprisingly displays significantly improved thermal stability, especially thermal shear resistance, even without the addition of a crosslinking promoter such as a multifunctional (meth)acrylate to the formulation. It has been shown that irradiation can improve the cohesive properties at high temperatures, while simultaneously, typically, the adhesive properties, such as adhesive strength, and mechanical properties, such as tensile strength, are essentially maintained.The observed improvement in cohesive properties is particularly surprising because the SK1 layer exhibits no gel component after electron irradiation and is therefore not macroscopically or long-range cross-linked. Consequently, the vinyl aromatic block copolymer is not cross-linked after electron irradiation. While not bound by theory, it is hypothesized that electron irradiation does not create a complete network, but does induce local bonds. Surprisingly, even SK1 layers with considerable thicknesses, such as 400 to 1500 µm, can be uniformly irradiated with electrons; that is, electron beam curing (EBC) of even such thick layers can be spatially uniform. Bilateral, i.e., symmetrical, irradiation is advantageous in this regard.

[0028] The SK1 layer is foamed, for example with microballoons. Foaming self-adhesive compounds, especially with microballoons, not only saves on raw material costs, but also typically leads to increased product cohesion, improved adhesion to rough surfaces, and enhanced shock resistance. Alternatively, the SK1 layer can also be unfoamed.

[0029] According to the invention, a self-adhesive composition "based on vinyl aromatic block copolymer" typically means that the polymer in question predominantly performs the function of the elastomer component in the self-adhesive composition. Preferably, the polymer in question is provided as the sole elastomer component in the self-adhesive composition, or at least constitutes at least 50% by weight based on the total proportion of all elastomer components.

[0030] According to the invention, polymer block A of the vinyl aromatic block copolymer is formed predominantly by polymerization of vinyl aromatics. This means that block A typically results from a polymerization in which more than 50 wt.% of the monomers used are vinyl aromatics, i.e., the proportion of vinyl aromatics during polymerization is more than 50 wt.%. Preferably, polymer block A results from a polymerization in which only vinyl aromatics have been used as monomers.

[0031] According to the invention, polymer block B of the vinyl aromatic block copolymer is formed predominantly by polymerization of conjugated dienes. This means that block B typically results from a polymerization in which more than 50 wt.% of the monomers used are conjugated dienes, i.e., the proportion of conjugated diene in the polymerization is more than 50 wt.%. Preferably, polymer block B results from a polymerization in which only conjugated dienes have been used as monomers.

[0032] Furthermore, the proportion of 1,2-linked conjugated diene in the B-block is less than 30 wt.%, preferably less than 20 wt.%, more preferably less than 15 wt.%, and particularly about 10 wt.%. The proportion of 1,2-linked conjugated diene in the B-block refers to the weight fraction of conjugated diene that has been polymerized by 1,2-addition (as opposed to 1,4-addition), based on the total monomer mass used in the production of polymer block B. The 1,2-addition of conjugated diene leads to a vinylic side chain in polymer block B, while the 1,4-addition of conjugated diene leads to vinylic functionality in the main chain of polymer block B.The 1,2-addition of a conjugated diene thus means that the diene functionality is polymerized either at positions C1 and C2, or at positions C3 and C4 (for example in the case of isoprene as a conjugated diene), in contrast to the 1,4-addition of a conjugated diene, where the diene functionality is polymerized at positions C1 and C4.

[0033] In a preferred embodiment, the adhesive strip does not include a (film) carrier. The adhesive strip typically consists of a single layer of self-adhesive compound SK1, making it a single-layer system. Such a single-layer, double-sided adhesive tape is also referred to as "transfer tape." Alternatively, the carrierless adhesive strip can also contain at least one additional layer besides the SK1 layer, which is not a carrier.

[0034] The self-adhesive compound of layer SK1 is a pressure-sensitive adhesive (PSA). The terms "self-adhesive" and "pressure-sensitive" are used synonymously in this document.

[0035] Pressure-sensitive adhesives are, in particular, polymeric compounds that—possibly through the addition of suitable components such as adhesive resins—remain permanently tacky and adhesive at the application temperature (unless otherwise specified, at room temperature) and adhere to a wide variety of surfaces upon contact, especially exhibiting immediate adhesion (a so-called "tack" [tackiness or initial tackiness]). They are capable of sufficiently wetting a substrate to be bonded at the application temperature without activation by solvents or heat—but usually through the influence of a more or less high pressure—so that sufficient interactions can develop between the compound and the substrate to ensure adhesion. Key influencing parameters for this include pressure and contact time.The special properties of pressure-sensitive adhesives are due, among other things, to their viscoelastic properties. For example, weakly or strongly adhesives can be produced; furthermore, those that can only be bonded once or permanently, so that the bond cannot be undone without destroying the adhesive and / or the substrates, or those that are easily removable and, if necessary, can be bonded multiple times.

[0036] Pressure-sensitive adhesives can generally be produced based on polymers of different chemical compositions. Their adhesive properties are influenced, among other things, by the type and proportions of the monomers used in the polymerization of the underlying polymers, their average molar mass and molar mass distribution, as well as by the type and quantity of additives in the adhesive, such as adhesive resins, plasticizers, and the like.

[0037] To achieve the viscoelastic properties, the monomers on which the polymers underlying the pressure-sensitive adhesive are based, as well as any other components of the pressure-sensitive adhesive that may be present, are selected in particular such that the pressure-sensitive adhesive has a glass transition temperature (according to DIN 53765) below the application temperature (i.e. usually below room temperature).

[0038] In some cases, it may be advantageous to increase and / or shift the temperature range in which a polymer compound exhibits pressure-sensitive adhesive properties by means of suitable cohesion-enhancing measures, such as crosslinking reactions (formation of bridge-forming links between the macromolecules). The application range of pressure-sensitive adhesives can thus be optimized by adjusting the flowability and cohesion of the compound.

[0039] An adhesive compound remains permanently tacky at room temperature, meaning it has a sufficiently low viscosity and high initial tack to wet the surface of the substrate even with minimal pressure. The adhesive's bonding ability is based on its adhesive properties, while its removability is due to its cohesive properties. Self-adhesive layers that can be used according to the invention

[0040] The SK1 layer of the adhesive strips according to the invention is based on a vinyl aromatic block copolymer mass.

[0041] Preferably, at least one synthetic rubber in the form of a block copolymer with a structure AB, ABA, (AB) n , (AB) n X or (ABA) n X is used in layer SK1 as a vinyl aromatic block copolymer, wherein The blocks A independently represent a polymer formed by polymerization of at least one vinyl aromatic, the blocks B independently represent a polymer formed by polymerization of conjugated dienes with 4 to 18 C atoms, X represents the remainder of a coupling reagent or initiator, and n represents an integer ≥ 2.

[0042] Particularly preferred are all synthetic rubbers of the self-adhesive layer according to the invention, block copolymers with a structure AB, ABA, (AB) n , (AB) n X or (ABA) n X as described above. The self-adhesive layer according to the invention can therefore also contain mixtures of different block copolymers with a structure as described above.

[0043] Suitable block copolymers (vinyl aromatic block copolymers) thus comprise one or more rubber-like blocks B (soft blocks) and one or more glass-like blocks A (hard blocks). At least one synthetic rubber of the self-adhesive layer according to the invention is particularly preferred as a block copolymer with a structure AB, ABA, (AB) 2 X, (AB) 3 X or (AB) 4 X, wherein A, B and X have the meanings given above. Most particularly preferred are all synthetic rubbers of the self-adhesive layer according to the invention as block copolymers with a structure AB, ABA, (AB) 2 X, (AB) 3 X or (AB) 4 X, wherein A, B and X have the meanings given above. In particular, the synthetic rubber of the self-adhesive layer according to the invention is a mixture of block copolymers having a structure AB, ABA, (AB) 2 X, (AB) 3 X or (AB) 4 X, preferably containing at least diblock copolymers AB and / or triblock copolymers ABA and / or (AB) 2 X.

[0044] Furthermore, a mixture of diblock and triblock copolymers and (AB) n - or (AB) n X-block copolymers with n greater than or equal to 3 is advantageous.

[0045] Furthermore, a mixture of diblock and multiblock copolymers and (AB) n - or (AB) n X-block copolymers with n greater than or equal to 3 is advantageous.

[0046] According to the invention, a mixture of linear block copolymers is used, in particular a mixture of diblock copolymers (AB) and triblock copolymers (ABA). For example, two types of vinyl aromatic block copolymers with different weight ratios of diblock copolymers (AB) and triblock copolymers (ABA) can be used. Particularly preferably, self-adhesive compositions according to the invention are based on styrene block copolymers; for example, the block copolymers of the self-adhesive compositions have polystyrene end blocks.

[0047] Vinyl aromatic block copolymers can thus be, for example, diblock copolymers AB in combination with other of the aforementioned block copolymers. The flow behavior and bond strength of the self-adhesive compounds can be adjusted by varying the proportion of diblock copolymers. The vinyl aromatic block copolymer used according to the invention preferably has a diblock copolymer content of 0 wt.% to 70 wt.%, more preferably 15 wt.% to 65 wt.%, even more preferably 30 wt.% to 60 wt.%, and particularly 40 wt.% to 60 wt.%, such as greater than 51.5 wt.% to 55 wt.%. A higher proportion of diblock copolymer in the vinyl aromatic block copolymer leads to a significant reduction in the cohesion of the adhesive compound.

[0048] Commercially available block copolymer types often contain a combination of polymers with different architectures. For example, Kraton D1101, nominally a linear polystyrene-polybutadiene triblock copolymer, contains 16 wt% diblock copolymer according to the manufacturer (The Global Connection for Polymer and Compound Solution - Product and Application Guide, Kraton Performance Polymers, 2011). Kraton D1118, on the other hand, another polystyrene-polybutadiene block copolymer, contains 78 wt% diblock copolymer.

[0049] The block copolymers resulting from the A and B blocks can contain identical or different B blocks. The block copolymers can have linear ABA structures. Radial block copolymers, as well as star-shaped and linear multiblock copolymers, can also be used. AB two-block copolymers can be present as additional components. All of the aforementioned polymers can be used individually or in mixtures.

[0050] In a vinyl aromatic block copolymer used according to the invention, such as in particular a styrene block copolymer, the proportion of polyvinyl aromatics, such as in particular polystyrene, is preferably at least 12 wt.%, more preferably at least 18 wt.% and particularly preferably at least 25 wt.% and likewise preferably at most 45 wt.% and more preferably at most 35 wt.%.

[0051] Instead of the preferred polystyrene blocks, polymer blocks based on other aromatic-containing homo- and copolymers (preferably C8 to C12 aromatics) with glass transition temperatures above 75 °C, such as α-methylstyrene-containing aromatic blocks, can also be used as vinyl aromatics. Furthermore, identical or different A-blocks can also be included.

[0052] Preferably, the vinyl aromatics used to construct block A comprise styrene, α-methylstyrene, and / or other styrene derivatives. Block A can thus exist as a homopolymer or copolymer. Block A is particularly preferably a polystyrene.

[0053] Preferred conjugated dienes as monomers for soft block B are selected in particular from the group consisting of butadiene, isoprene, ethylbutadiene, phenylbutadiene, pentadiene, hexadiene, ethylhexadiene, dimethylbutadiene, α-farnesene, and β-farnesene, as well as any mixture of these monomers. Block B can also be present as a homopolymer or as a copolymer. Butadiene, isoprene, or a mixture thereof are particularly preferred. Butadiene is used in particular. Polybutadiene exhibits better aging behavior compared to polyisoprene.

[0054] In the context of this invention, A-blocks are also referred to as "hard blocks". B-blocks are correspondingly also called "soft blocks" or "elastomer blocks". This reflects the selection of the blocks according to the invention based on their glass transition temperatures (for A-blocks at least 25 °C, in particular at least 50 °C, and for B-blocks at most 25 °C, preferably at most -25 °C, and in particular at most -50 °C).

[0055] In general, a block architecture as described above can be described as a "hard block-soft block architecture", even if it does not involve vinyl aromatic block copolymers.

[0056] The proportion of vinyl aromatic block copolymers, such as styrene block copolymers in particular, is preferably at least 35% by weight in total, based on the entire self-adhesive layer. An insufficient proportion of vinyl aromatic block copolymers results in relatively low cohesion of the adhesive.

[0057] The maximum total proportion of vinyl aromatic block copolymers, such as styrene block copolymers, in relation to the entire self-adhesive compound is a maximum of 75 wt.%, preferably a maximum of 65 wt.%, and most preferably a maximum of 55 wt.%. An excessively high proportion of vinyl aromatic block copolymers results in the adhesive compound having very little tackiness.

[0058] Accordingly, the proportion of vinyl aromatic block copolymers, such as styrene block copolymers, is preferably at least 35 wt.% and at the same time a maximum of 75 wt.%, more preferably a maximum of 65 wt.%, and most preferably a maximum of 55 wt.%, based on the total self-adhesive mass.

[0059] The tackiness of self-adhesive compounds can be achieved by adding adhesive resins that are miscible with the elastomer phase. In addition to at least one vinyl aromatic block copolymer, self-adhesive compounds typically contain at least one adhesive resin to enhance adhesion as desired. The adhesive resin should be compatible with the elastomer block of the block copolymers.

[0060] According to the general understanding of experts, an "adhesive resin" is understood to be a low-molecular-weight, oligomeric or polymeric resin that increases the adhesion (the tack, the inherent stickiness) of the pressure-sensitive adhesive compared to a pressure-sensitive adhesive that does not contain an adhesive resin but is otherwise identical.

[0061] Preferably, the adhesive resin is selected to comprise at least 75% by weight (based on the total resin content) and has a DACP (diacetone alcohol cloud point) greater than 0 °C, preferably greater than 10 °C, and particularly greater than 30 °C, and a softening temperature (ring and ball) of 70 °C or higher, preferably greater than or higher than 100 °C. Particularly preferably, the adhesive resin also has a DACP value of at most 45 °C if no isoprene blocks are present in the elastomer phase, or at most 60 °C if isoprene blocks are present in the elastomer phase. Particularly preferably, the softening temperature of the adhesive resin is at most 150 °C. According to the invention, the adhesive resins comprise at least 75% by weight (based on the total resin content) of hydrocarbon resins or terpene resins, or a mixture thereof.

[0062] It has been found that nonpolar hydrocarbon resins, such as hydrogenated and non-hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively, or fully hydrogenated hydrocarbon resins based on C5, C5 / C9, or C9 monomer streams, and polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene, are particularly advantageous as tackifiers for the pressure-sensitive adhesive(s). The aforementioned adhesive resins can be used alone or in mixtures. Both solid and liquid resins at room temperature can be used. Optionally, hydrogenated or non-hydrogenated adhesive resins containing oxygen can preferably be used up to a maximum proportion of 25% based on the total mass of the resins in the adhesive, such as rosin and / or rosin ester resins and / or terpene phenolic resins.

[0063] Hydrogenated hydrocarbon resins are particularly suitable according to the invention, since the absence of double bonds prevents crosslinking from being disrupted.

[0064] Furthermore, non-hydrogenated resins can also be used, especially when crosslinking promoters such as multifunctional acrylates are employed. The use of terpene resins based on α-pinene (Piccolyte A-series from Pinova, Dercolyte A-series from DRT) is particularly preferred, as these offer not only high cohesion but also very high adhesion, even at high temperatures. However, other non-hydrogenated hydrocarbon resins, non-hydrogenated analogs of the hydrogenated resins described above, can also be used.

[0065] The self-adhesive layers contain 20 to 60 wt.% of at least one adhesive resin, based on the total weight of the self-adhesive layer, preferably 30 to 50 wt.% of at least one adhesive resin, based on the total weight of the self-adhesive layer.

[0066] To stabilize the pressure-sensitive adhesive against aging, primary antioxidants such as sterically hindered phenols, secondary antioxidants such as phosphites or thioethers, and / or carbon radical scavengers are frequently added. Since the vinyl aromatic block copolymer used according to the invention has a low proportion of 1,2-linked conjugated diene in the B-block, the pressure-sensitive adhesive strip of the present invention is already comparatively age-resistant without the addition of an anti-aging agent. However, the aging stability can be further improved by adding an anti-aging agent. It should be noted, however, that anti-aging agents increase process complexity and, for example, tend to migrate or have a plasticizing effect.

[0067] Other additives that can typically be used include light stabilizers such as UV absorbers and sterically hindered amines, antiozonants, metal deactivators, processing aids and end-block reinforcing resins.

[0068] Plasticizing agents such as liquid resins (soft resins), plasticizer oils, or low-molecular-weight liquid polymers such as low-molecular-weight polyisobutylenes with molar masses of less than 1500 g / mol (number averages) or liquid EPDM types can be used in small quantities of less than 20 wt.%, and in particular less than 5 wt.%, based on the total mass of the self-adhesive compound. Preferably, Piccolyte®< A25 from Pinova, a low-molecular-weight polyterpene resin derived from α-pinene, is used. Plasticizing agents such as soft resins have the particular advantage of increasing the stickiness of the self-adhesive compound. Surprisingly, it has also been found that very good thermal stability, such as thermal shear resistance, can be achieved in the self-adhesive layer according to the invention even when using plasticizing agents after electron beam irradiation.

[0069] Fillers such as silicon dioxide, glass (ground or in the form of spheres), aluminum oxides, zinc oxides, calcium carbonate, titanium dioxide, carbon black, etc., as well as color pigments and dyes (colorants) and optical brighteners, can also be used. Colorant carriers can include, for example, ethylene vinyl acetate copolymer or other, especially thermoplastic, materials; alternatively, aqueous colorants such as colorant dispersions can be used.

[0070] To increase the radiation yield, crosslinking promoters are optionally used for electron beam curing. For example, crosslinking promoters based on multifunctional acrylates or thiols can be employed. However, it was surprisingly found that despite the small proportion of 1,2-linked conjugated diene in polymer block B of the vinyl aromatic block copolymer used, the corresponding self-adhesive layer can be cured by electron beam irradiation even without an additional crosslinking promoter, resulting in a layer with a high thermal shear resistance. Omitting the crosslinking promoter reduces the cost and complexity of manufacturing the pressure-sensitive adhesive strip according to the invention. Therefore, pressure-sensitive adhesive strips that do not contain a crosslinking promoter are preferably used according to the invention.

[0071] According to a preferred embodiment of the invention, the adhesive mass consists only of vinyl aromatic block copolymers, adhesive resins, microballoons and optionally the additives mentioned above.

[0072] Furthermore, the adhesive preferably consists of the following composition: • Vinyl aromatic block copolymers 35 to 65 wt.% • Adhesive resins 34.6 to 45% by weight • Microballoons 0.2 to 10 wt.% • Additive 0.2 to 10 wt.%

[0073] Furthermore, the adhesive preferably consists of the following composition: • Vinyl aromatic block copolymers 35 to 75 wt.% • Adhesive resins 24.8 to 60 wt.% • Microballoons 0.2 to 10 wt.%

[0074] The self-adhesive compound SK1 according to the invention is preferably foamed.

[0075] Foams can generally be produced in two ways. Firstly, by the action of a blowing agent, either added directly or resulting from a chemical reaction; secondly, by incorporating hollow spheres into the material matrix. Foams produced in the latter way are called syntactic foams.

[0076] Physical blowing agents useful in the present application are any naturally occurring atmospheric materials that are gaseous at the temperature and pressure at which the foam exits the nozzle. Physical blowing agents can be introduced, i.e., injected, into the polymer blend material as a gas, as a supercritical fluid, or as a liquid. The choice of physical blowing agent used depends on the desired properties in the resulting foams. Other factors considered in the selection of a blowing agent include its toxicity, vapor pressure profile, ease of handling, and solubility with respect to the polymeric materials used.Flammable propellants such as pentane, butane, and other organic materials like fluorocarbons and chlorofluorocarbons can be used, but non-flammable, non-toxic, non-ozone-depleting propellants are preferred because they are easier to use, e.g., there are fewer environmental concerns, etc. Suitable physical propellants include carbon dioxide, nitrogen, SF6, nitrogen oxides, perfluorinated liquids such as C2F6, noble gases such as helium, argon, and xenon, air (typically a mixture of nitrogen and oxygen), and mixtures of these materials.

[0077] Alternatively, chemical blowing agents can be used in the foam. Suitable chemical blowing agents include a mixture of sodium bicarbonate and citric acid, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, 4-4'-oxybis(benzenesulfonylhydrazide), azodicarbonamide (1,1'-azobisformamide), p-toluenesulfonylsemicarbazide, 5-phenyltetrazol, 5-phenyltetrazol analogues, diisopropylhydrazodicarboxylate, 5-phenyl-3,6-dihydro-1,3,4-oxadiazin-2-one, and sodium borohydride.

[0078] In a syntactic foam, microhollow spheres such as glass or ceramic hollow spheres or microballoons are embedded in a polymer matrix. This means that the cavities in a syntactic foam are separated from each other, and the substances (gas, air) located in the cavities are separated from the surrounding matrix by a membrane.

[0079] Foams made with microhollow spheres are characterized by a defined cell structure with a uniform size distribution of the foam cells. Microhollow spheres produce closed-cell foams without cavities, which, compared to open-cell variants, offer, among other things, better sealing properties against dust and liquids. Furthermore, chemically or physically foamed materials are more susceptible to irreversible collapse under pressure and temperature and often exhibit lower cohesive strength.

[0080] Particularly advantageous properties can be achieved when expandable microspheres (also known as "microballoons") are used as the foaming material. Due to their flexible, thermoplastic polymer shell, such foams exhibit greater adaptability than those filled with non-expandable, non-polymeric hollow microspheres (such as hollow glass spheres). They are better suited to compensating for manufacturing tolerances, which are common in injection-molded parts, and, due to their foam-like nature, can also better compensate for thermal stresses.

[0081] The foaming is therefore preferably carried out by introducing and subsequently expanding microballoons, i.e. the self-adhesive mass of layer SK 1 is preferably foamed with microballoons.

[0082] The term "microballoons" refers to elastic, and therefore expandable in their ground state, microhollow spheres with a thermoplastic polymer shell. These spheres are filled with low-boiling liquids or liquefied gas. Polyacrylonitrile, PVDC, PVC, or polyacrylates are particularly suitable shell materials. Low-boiling liquids such as isobutane or isopentane, which are contained as a liquefied gas under pressure within the polymer shell, are especially suitable.

[0083] When the microballoons are subjected to stress, particularly heat, the outer polymer shell softens. Simultaneously, the liquid propellant inside the shell transitions into a gaseous state. This causes the microballoons to expand irreversibly and three-dimensionally. The expansion ceases when the internal and external pressures equalize. Because the polymer shell remains intact, this process results in a closed-cell foam.

[0084] A wide variety of unexpanded microballoon types are commercially available, differing primarily in their size and the initial expansion temperatures required (75 to 220 °C). An example of commercially available unexpanded microballoons are the Expancel® DU types (DU = dry unexpanded) from Akzo Nobel. In the type designation Expancel xxx DU yy (Dry unexpanded), "xxx" represents the composition of the microballoon mixture, and "yy" represents the size of the microballoons in their expanded state.

[0085] Unexpanded microballoon types are also available as aqueous dispersions with a solids or microballoon content of approximately 40 to 45 wt.%, and furthermore as polymer-bound microballoons (masterbatches), for example in ethylene vinyl acetate with a microballoon concentration of approximately 65 wt.%. Both the microballoon dispersions and the masterbatches, like the DU types, are suitable for producing a foamed self-adhesive compound according to the invention.

[0086] A foamed self-adhesive compound SK1 according to the invention can also be produced using so-called pre-expanded microballoons. With this group, expansion takes place before the microballoons are mixed into the polymer matrix. Pre-expanded microballoons are commercially available, for example, from Akzo Nobel under the name Dualite® or with the type designation Expancel xxx DE yy (Dry Expanded). "xxx" represents the composition of the microballoon mixture, and "yy" represents the size of the microballoons in the expanded state.

[0087] When processing pre-expanded microballoon types, the microballoons may tend to flotation in the polymer matrix into which they are to be incorporated due to their low density. This means they rise to the top of the polymer matrix during processing. This leads to an uneven distribution of microballoons within the layer. More microballoons are found in the upper part of the layer (z-direction) than in the lower part, resulting in a density gradient across the layer thickness.

[0088] To largely or almost completely prevent such a density gradient, according to the invention, microballoons that are not or only slightly pre-expanded are preferably incorporated into the polymer matrix of layer SK1. The microballoons are expanded only after being incorporated into the layer. This results in a more uniform distribution of the microballoons in the polymer matrix.

[0089] Preferably, the microballoons are selected such that the ratio of the density of the polymer matrix to the density of the microballoons to be incorporated into the polymer matrix (which are not or only slightly pre-expanded) is between 1 and 1:6. Expansion then takes place only after or immediately during incorporation. In the case of solvent-containing compounds, the microballoons are preferably expanded only after incorporation, coating, and drying (solvent evaporation). According to the invention, DU types are therefore preferably used.

[0090] According to the invention, the mean diameter of the cavities formed by the microballoons in the foamed self-adhesive layer SK1 is preferably 20 to 150 µm, more preferably 20 to 50 µm, such as 40 to 45 µm. In the range of 20 to 50 µm, the microballoons result in particularly high shock resistance of the self-adhesive layers.

[0091] Since the diameters of the cavities formed by the microballoons in the foamed self-adhesive layers are being measured, the diameters in question are those of the cavities formed by the expanded microballoons. The mean diameter is the arithmetic mean of the diameters of the cavities formed by the microballoons in the respective SK1 self-adhesive layer.

[0092] When foaming is achieved using microballoons, the microballoons can be added to the formulation as a batch, paste, or as an unblended or blended powder. They can also be present suspended in a solvent.

[0093] According to a preferred embodiment of the invention, the proportion of microballoons in the self-adhesive layer SK1 is up to 12 wt.%, preferably between 0.25 wt.% and 5 wt.%, more preferably between 0.5 and 4 wt.%, even more preferably between 1 and 3.5 wt.%, and particularly between 2.0 and 3.0 wt.%, in each case based on the total composition of the self-adhesive layer. Within these ranges, self-adhesive layers can be provided which typically exhibit a particularly good balance between adhesion and cohesion.

[0094] A self-adhesive compound SK1 according to the invention containing expandable microhollow spheres may additionally also contain non-expandable microhollow spheres. The decisive factor is only that virtually all gas-containing cavities are closed by a permanently sealed membrane, regardless of whether this membrane consists of an elastic and thermoplastically stretchable polymer mixture or, for example, of elastic and – within the temperature range possible in plastics processing – non-thermoplastic glass.

[0095] Suitable for the self-adhesive compound according to the invention are also - independently selected from other additives - polymer solid spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres and / or carbon solid spheres ("Carbon Micro Balloons").

[0096] The absolute density of a foamed self-adhesive layer SK1 according to the invention is preferably 400 to 990 kg / m 3< , more preferably 450 to 800 kg / m 3< , even more preferably 500 to 700 kg / m 3< and in particular 500 to 600 kg / m 3< . Design and manufacture of the adhesive strip 1. Design of the adhesive strip:

[0097] Preferably, all layers of the adhesive strip have essentially the shape of a cuboid. Furthermore, preferably, all layers are bonded together across their entire surface. This bond can be optimized by pretreating the film surfaces.

[0098] The general term "adhesive strip" (self-adhesive strip), also synonymous with "adhesive tape" (self-adhesive tape), encompasses, within the meaning of this invention, all planar structures such as films or film sections extended in two dimensions, tapes with extended length and limited width, tape sections and the like, ultimately also die-cut pieces or labels.

[0099] The adhesive strip thus has a longitudinal extent (x-direction) and a lateral extent (y-direction). The adhesive strip also has a thickness (z-direction) perpendicular to both of these extents, with the lateral and longitudinal extents being many times greater than the thickness. The thickness is as uniform as possible, preferably exactly uniform, over the entire surface area of ​​the adhesive strip, which is defined by its length and width.

[0100] The adhesive strip according to the invention is in particular in the form of a web. A web is understood to be an object whose length (extension in the x-direction) is many times greater than its width (extension in the y-direction) and whose width preferably remains approximately the same along its entire length.

[0101] Typical packaging forms of the adhesive strips according to the invention are adhesive tape rolls in any conceivable dimension, spools with long running lengths and various widths, bales, rods and adhesive strips, such as those obtained in the form of die-cut pieces.

[0102] Preferably, die-cut parts are available in all conceivable sizes and shapes, for example, as solid die-cut parts with equal or different edge lengths, rounded or sharp corners, or even specially adapted shapes, but also as die-cut frames in all conceivable sizes, shapes, and web widths. The holding force of each connection point can be adjusted by the size of the die-cut part. The die-cut parts can be placed directly on the liner without being covered on the other side by another liner and are thus fed into the processing process. In this case, the component should be processed immediately. Alternatively, the die-cut parts can be provided with an additional adapted liner on the open side, with or without a finger lift. In this case, storage, shipping, or similar operations can take place.

[0103] Generally, it is advisable to apply or bond die-cut parts to components using automated machine processes. Any existing liner can be removed if necessary.

[0104] Furthermore, the adhesive tape can be supplied pre-cut into segments on rolls, for example, for mounting wiring in the automotive sector. This allows individual pieces to be peeled off the liner. Unlike the usual die-cut pieces, however, the pieces here lie adjacent to each other on the liner and are therefore always rectangular.

[0105] Adhesive tapes according to the invention, which are coated with adhesives on one or both sides, are usually wound into a roll in the form of an Archimedean spiral at the end of the manufacturing process. To prevent the adhesive layers of double-sided adhesive tapes from coming into contact with each other, or to ensure easier unwinding of single-sided adhesive tapes, the adhesive is covered with a release liner (also called a release material) before the tape is wound. Such release liners are known to those skilled in the art as release liners or simply liners. In addition to covering single- or double-sided adhesive tapes, liners are also used to cover labels. A liner (release paper, release film) is not a component of the adhesive tape itself, but merely an aid in its manufacture, storage, and / or further processing by die-cutting.Furthermore, unlike a tape backing, a liner is not permanently bonded to an adhesive layer. Release liners also prevent contamination of the adhesive before application. Additionally, release liners can be customized by adjusting the type and composition of the release materials to allow the tape to be unwound with the desired force (easy or difficult). For double-sided adhesive tapes, the release liners also ensure that the correct adhesive side is exposed first during unwinding.

[0106] Release liners are typically paper or film substrates coated on one or, in particular, both sides with an adhesive coating (also known as a deadhesive or anti-adhesive compound) to reduce the tendency of adhesive products to stick to these surfaces (release function). A variety of substances can be used as adhesive coatings, also called release coatings: waxes, fluorinated or partially fluorinated compounds, and especially silicones, as well as various copolymers containing silicone. In recent years, silicones have become widely established as release materials in adhesive tape applications due to their good processability, low cost, and broad property profile.

[0107] To facilitate the removal of a release liner from the adhesive tape, which usually takes place immediately before application, the liners are sometimes provided with gripping aids, so-called "tabs," on their reverse side (the unwind side). These facilitate peeling the liner because it is not necessary to first penetrate between the liner and the adhesive to grasp a section of the liner and then continue peeling it off; rather, simply gripping the tab is sufficient to remove the liner without difficulty. For this purpose, the tabs are welded or glued to the reverse side of the liner in such a way that a grippable part of the tab is not connected to the liner but protrudes from its surface or rests loosely on it. Such gripping aids are described, for example, in EP 2 426 185 A1.

[0108] Double-sided adhesive tapes are wound into a cross-wound long roll, also called a spool, as needed. Therefore, during their manufacture and storage, they are often provided with an additional release liner on one side. This additional release liner, often referred to as an "auxiliary liner" or "interliner," typically extends beyond the width of the adhesive tape on both sides and can thus prevent, among other things, the edges of the wound tape from sticking together, a phenomenon also known as blocking.

[0109] The adhesive tape according to the invention can also be a double-sided adhesive tape comprising an adhesive layer SK1 according to the invention, as defined above, and a heat-activated adhesive layer, wherein the adhesive layer is covered with a release liner. Such double-sided adhesive tapes with a heat-activated adhesive layer are generally wound into a cross-wound long roll or spool as described above, with the interliner typically located on the side of the heat-activated layer.

[0110] Various product structures are conceivable with regard to the adhesive strip. At least one layer SK1 of a self-adhesive compound according to the invention is always present. The SK1 layer can have a thickness of 15 to 5000 µm, preferably 50 to 3000 µm, more preferably 100 µm to 2000 µm, even more preferably 150 µm to 2000 µm, and even more preferably 400 to 1500 µm, particularly 400 to 900 µm, such as 500 to 800 µm. The adhesive strip can contain further layers, such as additional adhesive layers. Furthermore, non-adhesive layers, which are understood to be, in particular, carrier layers with low elasticity (ε max < 100%) or elasticity (ε max at least 100%), can be contained in the adhesive strip.

[0111] The release liner according to the invention preferably exhibits a balanced ratio of strength and flexibility. On the one hand, its strength should counteract overstretching or stretching of the adhesive tape during processing and application, while on the other hand, it should also be flexible enough to allow the adhesive tape with the release liner to be applied even in curved shapes without wrinkling. Preferably, the release liner is also dimensionally stable at elevated temperatures. This makes it possible, among other things, to coat the release liner with a hot-melt adhesive immediately after processing without adverse changes in the shape of the release liner; i.e., such a release liner can be coated directly. An example of such a release liner for use on pressure-sensitive adhesives is a release liner comprising the following layers: an outer silicone release layer (SR), a layer (POL) containing in each of its layers a total of at least 50 wt%, based on the total weight of the layer, one or more polyolefins, wherein the layer (POL) contains at least 60 wt%, based on the total weight of the layer (POL), polypropylene, and an outer layer (PER) containing at least 80 wt%, based on the total weight of the layer (PER), polyethylene, wherein the layer (PER) is bonded by an adhesive to the next layer in the structure of the release liner.

[0112] Preferably, the release liner is also provided with a gripping aid and can be easily peeled off the adhesive using this aid. For example, one or more gripping tabs, e.g., made of a PET / PE or an aluminum / PET / PE composite, can optionally be thermally welded to the release liner according to the invention. Such a liner can then be easily peeled off pressure-sensitive adhesives without affecting the bond between the gripping tab and the liner or the layer bond of the liner.

[0113] If the diblock content within the elastomer component is below 50%, then products are also available, in particular transfer tapes, which can be removed from an adhesive joint or from a surface essentially without residue by stretching. For the state of the art with regard to products that can be removed by stretching, reference is made to WO 2017 / 064167 A1 and the documents cited therein. 2. Production of the adhesive strip:

[0114] The production of the adhesive tape according to the invention, as defined in claim 1, can be carried out from either the solution or the melt. The application of the self-adhesive compound SK1, which can be used according to the invention, to a liner can be achieved by direct coating or by lamination, in particular hot lamination. In an exemplary solvent process for producing a transfer tape according to the invention, i.e., an adhesive tape made from a single layer of self-adhesive compound SK1, all components of the adhesive compound are dissolved in a solvent mixture such as gasoline / toluene / acetone. If microballoons are to be used, they are typically suspended in gasoline and stirred into the dissolved adhesive compound. For this purpose, the known compounding and stirring units can generally be used, taking care to ensure that the microballoons do not expand during mixing.Once the microballoons are homogeneously distributed in the solution, the adhesive can be coated using state-of-the-art coating systems. For example, the coating can be applied to a conventional PET liner using a doctor blade. In the next step, the coated adhesive is dried, for example, at 100 °C for 15 minutes. The drying temperature is specifically chosen to be lower than the expansion temperature to prevent the microballoons from expanding during drying. Therefore, the microballoons do not expand in any of the aforementioned steps. After drying, the adhesive layer is covered with a second layer of liner, such as a PET liner, and foamed in an oven within a suitable temperature-time window, for example, for 5 minutes at 150 °C or for 1 minute at 170 °C, with the foaming process taking place between the two liners to create a particularly smooth surface.

[0115] Alternatively, a transfer tape according to the invention can be produced from the melt. With the hot melt processes according to the invention, all previously known components of adhesives, especially self-adhesive ones, described in the literature, can be processed without solvents. Below, some hot melt processes for producing a transfer tape according to the invention are presented as examples, each of which is foamed with microballoons.

[0116] The invention thus comprises a method for producing a transfer tape according to the invention, wherein The components for forming an adhesive mass, such as polymers, resins or fillers and unexpanded microballoons, are mixed in a first mixing unit and heated under overpressure to expansion temperature. The microballoons are expanded upon exiting the mixing unit. The adhesive mass mixture, together with the expanded microballoons, is formed into a layer in a roller coating unit. The adhesive mass mixture, together with the expanded microballoons, is optionally applied to a web-shaped release material.

[0117] Also according to the invention is a method for producing a transfer tape according to the invention, wherein The components for forming an adhesive mass, such as polymers, resins and, if applicable, fillers, are mixed in a first mixing unit, and unexpanded microballoons, and, if applicable, also fillers, are mixed in a second mixing unit and heated under overpressure to expansion temperature in the second mixing unit. The microballoons are expanded upon exiting the mixing unit, the adhesive mass mixture together with the expanded microballoons is formed into a layer in a roller coating unit, and the adhesive mass mixture together with the expanded microballoons is, if necessary, applied to a web-shaped release material.

[0118] A particularly preferred method is one in which one of the units is a planetary roller extruder, which is also equipped with at least one degassing device in the form of a gas-permeable side arm extruder. Optionally and preferably, the planetary roller extruder has a further additional degassing device upstream of the first degassing device at the point where the components are added to form the adhesive mass. Surprisingly, such a unit offers advantages when processing block copolymers, such as styrene block copolymers (SBCs). Block copolymers soften above the melting or softening temperature of their hard blocks and then have a low viscosity, so that degassing in the highly liquefied state does not seem practical, as excessive leakage from the side arm extruder would be expected.Surprisingly, the planetary roller extruder with degassing device offers sufficient cooling capacity to compound and degas block copolymers, such as styrene block copolymers, within a single planetary roller extruder. A particularly advantageous method involves setting the wall temperature in a first processing zone above the melting or softening temperature (measured by DSC) of the styrene blocks, and in a subsequent, at least second, zone below the melting or softening temperature of the styrene blocks. The temperature of the central spindle can be selected appropriately, but is usually between these temperatures or below the melting or softening temperature of the styrene blocks. It is reasonable to assume that this method is also suitable for other, comparable block copolymers with a hard-block-soft-block architecture, provided the hard block is softenable.This method is particularly suitable when the proportion of such block copolymers is at least 35 wt.% in the adhesive formulation, and most preferably at least 40 wt.%, and / or at least one tackifying resin is included.

[0119] A method for producing an adhesive compound, preferably a pressure-sensitive adhesive compound, such as in particular a self-adhesive compound as defined in claim 1, based on block copolymers with a hard-block-soft-block architecture, is particularly preferred, wherein the hard blocks are softenable or meltable at a temperature T (measured by DSC), wherein the process is carried out on a planetary roller extruder, and wherein in a first process zone of the planetary roller extruder a wall temperature is set above the melting or softening temperature T of the hard blocks, and in a subsequent at least second process zone a wall temperature is set below the melting or softening temperature T of the hard blocks, and wherein the planetary roller extruder has a degassing device in the form of a gas-permeable side arm extruder downstream of the addition of the components of the adhesive.

[0120] Particularly preferred is a method for producing an adhesive compound, preferably a pressure-sensitive adhesive compound, such as in particular a self-adhesive compound as defined in claim 1, based on block copolymers with a hard-block-soft-block architecture, wherein the hard blocks are softenable or meltable at a temperature T (measured by DSC), wherein the process is carried out on a planetary roller extruder, and wherein in a first process zone of the planetary roller extruder a wall temperature is set above the melting or softening temperature T of the hard blocks, and wherein expandable microballoons are added before or in this zone, which foam up in this zone, and wherein in a subsequent at least second process zone a wall temperature is set below the melting or softening temperature T of the hard blocks, and wherein the planetary roller extruder has a degassing device in the form of a gas-permeable side arm extruder downstream of the addition of the components of the adhesive mass.

[0121] In particular, these above methods are preferably used in the production of the adhesive strip according to the invention in its various embodiments.

[0122] Furthermore, the invention comprises a method for producing a transfer tape according to the invention, wherein The components for forming an adhesive mass, such as polymers, resins or fillers and unexpanded microballoons, are mixed in a first mixing unit and heated to expansion temperature; the microballoons expand at least partially, preferably completely, during mixing; the adhesive mass mixture together with the expanded microballoons is formed into a layer in a roller coating unit; the adhesive mass mixture together with the expanded microballoons is optionally applied to a web-shaped release material.

[0123] The invention also includes a method for producing a transfer tape according to the invention, wherein The components for forming an adhesive mass, such as polymers, resins, or fillers, are mixed with unexpanded microballoons in a first mixing unit under overpressure and tempered to a temperature below the expansion temperature of the microballoons. The mixed, in particular homogeneous, adhesive mass is transferred from the first mixing unit to a second unit and then heated to the expansion temperature. The microballoons are expanded in the second unit or upon exiting the second unit. The adhesive mass mixture, together with the expanded microballoons, is formed into a layer in a roller coating unit. The adhesive mass mixture, together with the expanded microballoons, is optionally applied to a web-shaped release material.

[0124] The invention also relates to a method for producing a transfer tape according to the invention, wherein The components for forming an adhesive mass, such as polymers, resins, or fillers, are mixed in a first mixing unit; the mixed, in particular homogeneous, adhesive mass is transferred from the first mixing unit to a second mixing unit, into which the unexpanded microballoons are also placed; the microballoons are expanded in the second mixing unit or upon exiting the second mixing unit; the adhesive mass mixture together with the expanded microballoons is formed into a layer in a roller coating unit; the adhesive mass mixture together with the expanded microballoons is optionally applied to a web-shaped release material.

[0125] In the described hot melt processes for producing a transfer tape according to the invention, the self-adhesive layer can optionally be covered with a web-shaped release material, i.e., a liner. Preferably, the self-adhesive layer is covered with a liner on both surfaces (subsequently, the transfer tape is subjected to electron beam curing).

[0126] Many machines are known for the continuous production and processing of solvent-free polymer systems. Screw extruders, such as single-screw and twin-screw extruders of varying process lengths and configurations, are most commonly used. However, continuously operating kneaders of various designs, including combinations of kneaders and screw extruders, as well as planetary roller extruders, are also employed for this task.

[0127] For example, it is advantageous if the first mixing unit is a continuous unit, in particular a planetary roller extruder, a twin-screw extruder or a pin extruder, the first mixing unit is a discontinuous unit, in particular a Z-kneader or an internal mixer, the second mixing unit is a planetary roller extruder, a single-screw or twin-screw extruder or a pin extruder and / or the forming unit in which the adhesive mass together with the expanded microballoons is formed into a carrier layer, is a calender, a roller applicator or a gap formed by a roller and a stationary doctor blade.

[0128] Optional degassing ideally takes place immediately before the roller coating unit at mixing temperature and a differential pressure to ambient pressure of at least 200 mbar.

[0129] A particularly preferred method is one in which the first mixing unit is a planetary roller extruder and the second mixing unit is a twin screw extruder.

[0130] It can be particularly advantageous if the second mixing unit, according to one of the methods listed above, is a planetary roller extruder with a degassing device in the form of a gas-permeable side arm extruder.

[0131] A particularly preferred method involves a planetary roller extruder as the first mixing unit and a planetary roller extruder with a degassing device in the form of a gas-permeable side-arm extruder as the second mixing unit. Planetary roller extruders have been known for some time and were initially used in the processing of thermoplastics such as PVC, where they were primarily used to feed downstream units such as calenders or rolling mills. Due to their advantages of large surface renewal for material and heat exchange, which allows the energy introduced via friction to be dissipated quickly and effectively, as well as their short residence time and narrow residence time range, their application has recently expanded to include compounding processes, which require particularly precise temperature control.

[0132] Planetary roller extruders are available in various designs and sizes, depending on the manufacturer. Depending on the desired throughput, the diameter of the roller cylinders typically ranges from 70 mm to 400 mm.

[0133] Planetary roller extruders typically have a filling section and a compounding section.

[0134] The filling section consists of a screw conveyor onto which all solid components are continuously metered. The screw conveyor then transfers the material to the compounding section. The area of ​​the filling section containing the screw is preferably cooled to prevent material buildup on the screw. However, there are also embodiments without a screw conveyor, in which the material is fed directly between the central and planetary spindles. This is not significant for the effectiveness of the process according to the invention.

[0135] The compounding unit consists of a driven central spindle and several planetary spindles that rotate around the central spindle within one or more roller cylinders with internal helical gearing. The rotational speed of the central spindle, and thus the rotational speed of the planetary spindles, can be varied and is therefore an important parameter for controlling the compounding process.

[0136] The materials are circulated between central and planetary spindles or between planetary spindles and the helical gearing of the roller part, so that under the influence of shear energy and external temperature control the dispersion of the materials into a homogeneous compound takes place.

[0137] The number of planetary spindles rotating in each roller cylinder can be varied and thus adapted to the requirements of the process. The number of spindles influences the free volume within the planetary roller extruder, the residence time of the material in the process, and also determines the surface area for heat and material exchange. The number of planetary spindles affects the compounding result via the shear energy introduced. With a constant roller cylinder diameter, a larger number of spindles results in better homogenization and dispersion performance, or a higher product throughput.

[0138] The maximum number of planetary spindles that can be installed between the central spindle and the roller cylinder depends on the diameter of the roller cylinder and the diameter of the planetary spindles used. When using larger roller diameters, as required to achieve production-scale throughput rates, or smaller diameters for the planetary spindles, the roller cylinders can be equipped with a greater number of planetary spindles. Typically, up to seven planetary spindles are used with a roller diameter of D = 70 mm, while, for example, ten planetary spindles can be used with a roller diameter of D = 200 mm, and, for example, 24 planetary spindles can be used with a roller diameter of D = 400 mm.

[0139] According to the invention, it is proposed to carry out the coating of the optionally foamed adhesive compounds solvent-free using a multi-roller coating unit. This coating unit can consist of at least two rollers with at least one roller gap and up to five rollers with three roller gaps.

[0140] Coating plants such as calenders (I,F,L-calender) are also conceivable, so that the foamed adhesive mass is formed to the desired thickness as it passes through one or more roller gaps.

[0141] The preferred 4-roll coating unit consists of a metering roll, a doctor blade roll which determines the thickness of the coating on the substrate and is arranged parallel to the metering roll, and a transfer roll located below the metering roll. The coating material and the web-shaped material are combined on the transfer roll, which together with the transfer roll forms a second roll gap.

[0142] To improve the transfer behavior of the formed layer of material from one roller to another, rollers with anti-adhesive coatings or anilox rollers can be used. To produce a sufficiently precisely formed adhesive film, the peripheral speeds of the rollers can be adjusted.

[0143] Depending on the type of web-shaped substrate material to be coated, the coating can be carried out using a synchronous or counter-rotating process.

[0144] The forming unit can also be formed by a gap between a roller and a stationary doctor blade. The stationary doctor blade can be a knife blade or a stationary (half) roller.

[0145] The preferred two-roll coating unit consists of two co-rotating rollers, each of which is fed with an anti-adhesive film, release paper, or other release or carrier material. The compound is then formed between these release or carrier materials. For example, these could be siliconized 50 µm thick PET films. The two release or carrier materials can be the same or different. A rotating compound pool is typically formed in the coating gap. The compound can be fed into the roller gap via one or more pipe feeds, which may be stationary or moving. Alternatively, the compound can be introduced via a pre-distribution nozzle. Optionally, the compound is deposited, with or without a free-flowing tail, onto one of the webs entering the roller gap.The formed product can be wound up with both sides covered, or one of the release or carrier materials can be uncovered again. These and other release or carrier materials can also be exchanged or re-covered inline. 3. Electron beam curing of the adhesive strip:

[0146] The adhesive strip according to claim 1 is then subjected to electron beam curing with a dose of 10 to 100 kGy, using a system from ELECTRON CROSSLINKING AB (Halmstad, Sweden), at an accelerating voltage of 220 keV (adjusted as needed to the desired penetration depth and density of the product) and a suitable dose of 10 to 100 kGy. Doses of less than 75 kGy as well as greater than 75 kGy are therefore conceivable. Typically, the self-adhesive layer is irradiated with electrons from both sides, i.e., symmetrically, to ensure uniform curing. This is particularly advantageous for thicker self-adhesive layers. For thin samples with a thickness of, for example, 50 µm, irradiation can be performed on one side only.Preferably, the liner is removed from the relevant side before irradiation, particularly to avoid radiation loss and damage to the liner. Damage to the liner can, in particular, prevent it from being peeled off the self-adhesive layer after irradiation. With suitable technical implementation, the irradiation process can be carried out inline or as a single step in the manufacturing process.

[0147] Accordingly, the present invention also relates to a method for producing an adhesive strip as defined above, in which the self-adhesive mass is processed from the solution or from the melt to form layer SK1, and layer SK1 is optionally subsequently subjected to electron irradiation. The method can be carried out without the use of a crosslinking promoter, which reduces the cost and complexity of producing the adhesive strip according to the invention. Use of the adhesive strip according to the invention

[0148] In contrast to spot welding, the adhesive strip according to the invention allows for the simple joining of both identical and dissimilar materials. When joining two different plastics or other materials with different melting points by welding, weak points can occur in the material due to burning, or the joining may be incomplete because one material does not flow sufficiently into the weld point and bond with the other. When joining with the adhesive strip according to the invention, differing material properties are no longer relevant.

[0149] The adhesive strip according to the invention (unirradiated or irradiated with electrons) is particularly effective not only for its good adhesion to polar surfaces but also for its good adhesion to low-energy, i.e., non-polar surfaces (LSE (low surface energy) surfaces). Since no adhesion promoter or primer is required, bonding can be performed without substrate pretreatment. It can therefore be used, in particular, for bonding non-polar surfaces, i.e., surfaces with a surface energy of 50 mN / m or less, preferably less than 40 mN / m, and especially less than 35 mN / m. Especially in automotive applications, plastics are increasingly being used instead of metals. These typically have a low surface energy, which often makes bonding to these substrates difficult. The adhesive strip according to the invention can remedy this problem.Examples of nonpolar surfaces that can be bonded according to the invention include those based on fluorinated polymers such as Teflon, organosilicon polymers, polyolefins such as polyethylene, polypropylene, EPDM or a polypropylene-EPDM composite, ethylene-vinyl acetate copolymers, polyvinyl aromatics such as polystyrene or copolymers based on styrene (e.g., styrene-butadiene block copolymers, acrylonitrile-butadiene-styrene copolymers), polyvinyl acetate, polyacrylates such as polymethyl methacrylate, polycarbonates, polyurethanes, polyamides, polyesters such as polyethylene terephthalate, cellulose acetate, ethylcellulose, or based on polymers containing segments of the aforementioned polymers, or those based on a mixture of the aforementioned polymers, optionally with other polymers. In this context, the phrase "based on the polymer" usually means that the polymer in question predominantly performs the function of the surface material.Typically, the polymer in question is the sole polymer in the surface material, or at least constitutes at least 50% by weight of the total polymer content. Resins are not considered polymers in this context. However, the adhesive strip is also suitable for bonding substrates other than polymers, such as glass or ceramics, metals like stainless steel, metal oxides, or combinations thereof. The materials can be in pure form or blended or filled with other materials. Furthermore, the material can be recycled or a functional substance, for example, to increase or decrease conductivity or haptics.

[0150] The adhesive strip according to the invention is suitable for permanently bonding two molded parts made of the same or different materials. All conceivable materials can be used, preferably those listed above. Stiff materials such as metals or plastics with a high modulus of stiffness, or plastics reinforced with, for example, glass fibers or other reinforcing materials, are preferred.

[0151] The adhesive strip according to the invention is therefore suitable for a wide variety of industrial applications, preferably for indoor applications, and in particular in the construction, automotive or electronics sectors.

[0152] The adhesive strip can be used, for example, in automotive interiors, particularly in doors, such as interior doors, cockpits, center consoles, seats, and other parts whose basic structure or individual components need to be joined together. It can also be used, for example, on automotive body side moldings, rearview mirrors, exterior trim panels, weatherstripping, road signs, trade signs, structures, control cabinets, shell molds, machine parts, junction boxes, or backsheet solutions for photovoltaic modules (i.e., in the solar cell industry). Furthermore, it can be used for bonding to automotive clearcoat surfaces, especially clearcoats for vehicles like cars. The substrate onto which the adhesive strip can be applied is selected depending on the specific application. For example, the adhesive strip can be applied to film products (e.g.,It can be applied to decorative graphics and reflective products), label material, and tape carriers. Furthermore, it can be applied directly to other substrates, such as a metal plate (e.g., a vehicle registration plate) or a glass window, allowing another substrate or object to be attached to the plate or window.

[0153] According to the invention, semi-finished products or add-on parts are equipped with an adhesive strip according to the invention. If the semi-finished products or add-on parts are prepared accordingly, their integration into the final bonding process in the production line is particularly efficient.

[0154] When the adhesive strip is laminated onto the substrate, it may be desirable to treat the surface of the substrate and / or the adhesive strip to further improve adhesion. Such treatments are typically selected based on the type of materials in the adhesive strip and the substrate and include priming and surface modifications, such as corona treatment and surface abrasion. In particular, the adhesive strip and / or the surfaces to be bonded may be coated with a primer to achieve better adhesion of the adhesive strip to the surfaces to be bonded. The substrate and / or the adhesive strip may also have undergone plasma treatment. However, due to the good adhesion of the adhesive strip according to the invention not only to polar but also to non-polar surfaces, this is generally not necessary.The adhesive strip according to the invention therefore has the advantage that it can typically be used to bond different surfaces without the use of a primer.

[0155] The bonding of surfaces, particularly low-energy surfaces, can surprisingly be carried out even at low temperatures using the adhesive strip according to the invention, such as at a temperature of no more than 10 °C, preferably no more than 5 °C, and particularly no more than 0 °C. Thus, surfaces can be conveniently bonded even in cold environments using the adhesive strip according to the invention, for example, in production halls or workshops. In particular, two components can be joined, i.e., bonded. Preferably, the components have different surface energies. The surprising suitability for bonding at low temperatures is explained in the examples.

[0156] The invention further relates to a method for joining components, in which the components are mechanically joined, for example by welding, and simultaneously bonded by means of an adhesive strip according to the invention.

[0157] Due to its excellent conformability, the adhesive strip is particularly suitable for bonding over steps, welds, and other surface textures. Its high initial tack and good resistance to peeling ensure a secure bond even over such challenging surfaces.

[0158] Furthermore, the adhesive strip according to the invention exhibits very high tensile, tensile shear, and end-face tensile strength. For example, in a tensile or shear test of two 3 mm thick PP / EPDM test substrates bonded with the adhesive strip according to the invention, the test substrate can be deformed or destroyed before the bond fails.

[0159] In addition to bonding non-polar substrates or coatings, the adhesive tape according to the invention is particularly suitable for bonding oil-contaminated substrates such as metal sheets. It is especially important that there is no reduction in adhesive strength on such critical substrates, and therefore cross-linking of the adhesive tape does not appear obvious or feasible. At the same time, high thermal shear strength is generally required for structural bonding of, for example, metal sheets. The surprising suitability for bonding to oiled sheets is illustrated in the examples.

[0160] Another preferred option is the bonding of two components that have additional positioning pins within the molded parts, but are held together by the adhesive tape.

[0161] The tape's very fast initial adhesion to various substrates, even low-energy surfaces, enables rapid, automated application, including on plastics. Such plastics are particularly common in automotive interiors, especially in doors, interior doors, cockpits, center consoles, seats, and other components whose basic structure or individual parts need to be joined together. The tape is also suitable for bonding add-on or decorative parts that are mounted inside or outside the vehicle. Typically, this involves bonding a plastic part to a painted surface, such as an EPDM add-on with a low-energy clear coat on a metal sheet. figure

[0162] The figure described below illustrates a particularly advantageous embodiment of the invention, without unnecessarily restricting the invention.

[0163] In Figure 1The schematic structure of a single-layer adhesive strip according to the invention, consisting of a layer 2, is shown as a cross-section.

[0164] The strip comprises a self-adhesive adhesive layer 2 (layer SK1). In the exemplary embodiment shown, the self-adhesive adhesive layer 2 (layer SK1) is covered with a liner 4, 5.

[0165] The invention is explained in more detail below by means of examples. The examples described below illustrate particularly advantageous embodiments of the invention without unnecessarily limiting its scope. Examples

[0166] The raw materials used are characterized as follows: Kraton® < D1101: Styrene-butadiene-styrene triblock copolymer from Kraton Polymers with 16 wt% diblock, block polystyrene content: 31 wt%, proportion of 1,2-linked conjugated diene in the butadiene block: 10 wt% Kraton® < D1118: Styrene-butadiene-styrene triblock copolymer from Kraton Polymers with 78 wt% diblock, block polystyrene content: 33 wt%, proportion of 1,2-linked conjugated diene in the butadiene block: 10 wt% Dercolyte A115: Solid α-pinene adhesive resin with a ring and ball softening temperature of 115 °C and a DACP of 35 °C Piccolyte® < A25: Polyterpene resin based on α-pinene with a ring and Ball softening temperature of 22 to 28 °C. Escorez 2203: C5 and C9-based hydrocarbon resin with low aromatic content, softening point (ring & ball) 95 °C. Expancel 920 DU40, Expancel 920 DU80: unexpanded microballoons. Ebecryl 140: di(trimethylolpropane)tetraacrylate

[0167] Table 1 shows the composition of the adhesive formulations used. Table 1: Composition of the adhesive formulations used (data in parts by weight). R1 R2 R3 R4 Kraton D 1101 25 25 20 20 Kraton D 1118 25 25 30 30 Escorez 2203 50 Dercolyte A115 50 48 50 Piccolyte A25 2 Expandel 920DU40 3 3 Expandel 920DU80 3 3 Method V1 (solvent method):

[0168] For this purpose, a 40 wt% adhesive solution in gasoline / toluene / acetone was first prepared according to the specified formula. The weight percentages of the dissolved components refer to the dry weight of the resulting solution.

[0169] The solution was then mixed with unexpanded microballoons as needed, the microballoons being used as a slurry in gasoline. The weight fraction of the microballoons refers to the dry weight of the solution to which they were added (i.e., the dry weight of the solution is set to 100%). The resulting mixture was then spread with a brush onto a PET liner coated with a separating silicone to the desired layer thickness. Subsequently, the solvent was evaporated at 100 °C for 15 minutes, thus drying the adhesive layer. A second PET liner of the same type was then laminated onto the exposed surface of the prepared and dried adhesive layer, and the adhesive layer was subsequently foamed between the two liners in an oven at 150 °C for 5 minutes, resulting in an approximately 100 µm thick adhesive strip according to the invention.If necessary, the target thickness was achieved by multiple laminations of this layer. The desired dimensions were then obtained by die-cutting. Procedure V2 (Hotmelt procedure):

[0170] The elastomer components were added in the feed section of the PWE (planetary roller extruder), which comprised a feed area and two process sections. The guide rings had an increasing diameter in the process direction. Although various spindle configurations were suitable, configurations were preferred in which at least ¾ of the maximum number of spindles was used in the first process section. The resin components were melted and added in the second process section of the PWE. A resin split was particularly suitable for producing homogeneous mixtures, in which part of the resin was added in the first process section and the remainder downstream in the second. Adding both components in liquid form via side feed or guide rings was particularly effective, with the first component comprising approximately 10% of the total resin quantity. Unless otherwise specified, the process was carried out in this manner.Adding the first resin component directly into the PWE feed or via side feed in the first process stage would also be suitable. The compounded mass was transferred to the twin-screw extruder via a heated hose.

[0171] Microballoons were fed via a side feed into the first third of the twin-screw extruder and foamed there, so that the foaming was essentially complete before exiting the unit. Due to frictional heat, the melt temperature in the twin-screw extruder was always above the set wall temperatures. A vacuum was applied at a suitable point at the end of the twin-screw extruder. The melt exit temperature was approximately 130°C. The melt was then transferred via a pre-distribution die (coat hanger die) into a two-roll calender and formed between two 50 µm PET films coated with silicon on both sides. This advantageous process consistently achieved roughness values ​​Ra < 5 µm (measured by white light interferometry).

[0172] Table 2 shows the parameters of the hot melt process. Table 2: Parameters of the hot melt process (L / D = length / diameter). Total throughput of elastomer components 20 kg / h Diameter of roller cylinders 70 mm Temp. PWE central spindle 50 °C Temp. PWE Zones 90°C / 90°C / 90°C / 90°C PWE speed 100 / min Diameter of DSE screws and L / D 42 mm, 36 L / D Temp. DSE Zones 20°C / 50°C / 80°C / 80°C DSE speed 100 / min Vacuum DSE 200 mbar Temp. Calender rolls 120 °C / 120 °C

[0173] The following describes the production of an adhesive strip according to the invention, consisting of a single foamed self-adhesive layer SK1 (transfer tape) based on microballoon-foamed vinyl aromatic block copolymer. The self-adhesive layer SK1 can be produced without the use of a soft resin (Example B1) or using such a resin (Example B2). Example B3 corresponds to B2, but produced using the hot melt process V2. Example B4 corresponds to B3, but with the resin Escorez 2203 and a different elastomer mixture. Example B5 corresponds to B3, but with a different elastomer mixture; see also the explanations below.

[0174] Table 3 provides an overview of examples B1 to B5 as combinations of different recipes and procedures. Table 3: Overview of the recipes and manufacturing processes used in examples B1 to B5. Example Recipe Proceedings B1 R1 V1 B2 R2 V1 B3 R2 V2 B4 R3 V2 B5 R4 V2

[0175] Subsequently, the self-adhesive layer SK1 was irradiated with electrons as described. Example B1:

[0176] The adhesive strip was manufactured according to process V1 using formulation R1, resulting in a thickness of approximately 1000 µm. This thickness always refers to the adhesive strip without the PET liner. Example B2:

[0177] The production of the adhesive strip from Example B2 differs from the production of the adhesive strip from Example B1 only in that the 40 wt.% adhesive solution used further contains 2 wt.% Piccolyte ®< A25, based on the dry weight of the resulting solution. Examples B3 - B5:

[0178] Example B3 was produced using the same recipe as B2, but with the hot melt process V2. Examples B4 and B5 were produced like B3, but with the recipes listed in Table 3. Irradily with electrons of examples B1 to B5:

[0179] The SK1 self-adhesive layer of the pressure-sensitive adhesive strip from examples B1-B5 was subsequently subjected to electron beam curing using a system from ELECTRON CROSSLINKING AB (Halmstad, Sweden). The accelerating voltage was 220 keV. The dose was varied in increments of 10 kGy from 10 to 100 kGy. The self-adhesive layer was irradiated symmetrically from both sides to ensure uniform curing. Before irradiation, the liner was removed from the side to be irradiated. An unirradiated reference sample was always produced as well. Results for examples B1 to B5: Example 1:

[0180] The adhesive strip (containing no soft resin) from Example B1, subjected to the specified doses of electron radiation, was tested for its thermal shear life using the static shear test (test strip dimensions: 25 mm length, 25 mm width, test temperature: 80 °C, load: 500 g). Without electron irradiation, the thermal shear life was already more than 2,000 min; with a radiation dose of 40 or 60 kGy, it was approximately 2,600 min; with a radiation dose of 80 kGy, it was approximately 8,000 min; and with a radiation dose of 100 kGy, the test strip had still not sheared even after 10,000 min. The thermal shear life could therefore be increased with increasing irradiation intensity, resulting in very good thermal shear life (even without an additional crosslinking promoter). The gel content of the self-adhesive layer SK1 was determined to be 0 wt% at all irradiation intensities, i.e., no macroscopic cross-linking could be detected.

[0181] The adhesive strength of the unirradiated adhesive strip was approximately 28 N / cm. Furthermore, the adhesive strength (as well as the tensile strength) of the adhesive strip remained essentially unchanged upon irradiation with electrons (of varying doses). Example 2:

[0182] The adhesive strip (containing Piccolyte®< A25 as a soft resin) from Example B2, which was subjected to the specified doses of electron radiation, was also tested for its thermal shear life using the static shear test (test strip dimensions: 13 mm length, 20 mm width, test temperature: 70 °C, load: 500 g). Without electron irradiation, this life was already approximately 3,400 minutes. Even at a radiation dose of 10 kGy (and up to a radiation dose of 100 kGy), the test strip had not sheared off even after 10,000 minutes. The slip distance of the test sample after 10,000 minutes was, for example, 4.8 mm, 2.8 mm, 2.7 mm, and 2.0 mm at radiation doses of 10 kGy, 20 kGy, 30 kGy, and 40 kGy, respectively. The heat resistance of an adhesive strip containing soft resin could therefore be increased with increasing irradiation intensity, resulting in very good heat resistances (even without an additional crosslinking promoter).The gel content of the SK1 self-adhesive layer was determined to be 0 wt% in each case, meaning that no macroscopic cross-linking could be observed. Therefore, the use of soft resin does not preclude the achievement of high heat resistance.

[0183] The adhesive strength of the unirradiated adhesive strip was approximately 34 N / cm, meaning it could be increased by using soft resin. Furthermore, the adhesive strength (as well as the tensile strength) of the adhesive strip remained essentially unchanged after irradiation with electrons (of varying doses). Example B3:

[0184] Example B3 was tested in the same way as Example B2. The gel content was also determined to be 0 wt% after ESH irradiation with the specified doses. Without ESH irradiation, the thermal shear life in the static shear test at 70°C was 4000 min. From a dose of 20 kGy, the shear life was >10,000 min. Example B4:

[0185] Example B4 was tested in the same way as Example B2. The gel content was also determined to be 0 wt% after ESH irradiation with the specified doses. Without ESH irradiation, the thermal shear life in the static shear test at 70°C was 1200 min. From a dose of 20 kGy, the shear life was >10,000 min. Example B5:

[0186] Example B5 was tested in the same way as Example B2. The gel content was also determined to be 0 wt% after ESH irradiation with the specified doses. Without ESH irradiation, the thermal shear life in the static shear test at 70°C was 5400 min. From a dose of 20 kGy, the shear life was >10,000 min. Examples 6 to 8 (including results):

[0187] The following describes the production of a foamed self-adhesive layer SK1 according to the invention with a thickness of approximately 500 µm, which in examples B6 - B8 was produced with formulation R1 according to the hot melt process V2. These examples contained the proportion of crosslinking promoter Ebecryl 140 specified in Table 4. Examples B6 - B8 were produced both with and without electron beam irradiation, as specified in Table 4. Table 4: Overview of examples 6 to 8 (including results). SSZ = Shear life. KK = Adhesive strength. Basic recipe Networking promoter Manufacturing process ESH dose [kGy, at 170kV] SSZ 70°C [min] KK 90° ASTM [N / cm] Value B6 R1 0% V2 0 4592 22,7 0% B6 R1 0% V2 50 10.000 17,3 0% B7 R1 1% V2 0 3564 20,8 0% B7 R1 1% V2 50 10.000 13,0 1,5% B8 R1 3% V2 0 460 18,6 0% B8 R1 3% V2 50 10.000 11,2 11%

[0188] This table shows that a high shear strength at 70°C can be achieved using ESH even without a crosslinking promoter, and furthermore, that the use of a crosslinking promoter is disadvantageous because the adhesive strength is noticeably reduced even at low gel values ​​(11% or less). The pressure-sensitive adhesives according to the invention therefore preferably have a gel value of 0% after ESH treatment. In particular, with the ESH treatment according to the invention without a crosslinking promoter, the adhesive strength after ESH treatment reaches at least 75% of the initial value without ESH treatment, and / or the dose of ESH treatment is selected such that the adhesive strength after ESH treatment reaches at least 75% of the initial value without ESH treatment. Bonding to oiled surfaces:

[0189] To verify their suitability for bonding to oiled substrates, the adhesive tapes were bonded to steel sheets with 4 g / m² of oil (Quaker 61AUS) as specified in Table 5. Comparison tape 1 is a 500 µm thick double-sided acrylic tape, manufactured according to the MT15 example from DE 10 2009 048036 A1. Comparison tape 2 is the commercially available product tesa © 4954, i.e., an approximately 430 µm thick double-sided adhesive tape with natural rubber adhesives.

[0190] It can be seen that the adhesive tape according to the invention, as shown in example B6 (but produced with an irradiation intensity of 20 kGy), has excellent adhesive strength on the oiled substrate. Table 5: Adhesive strength on oiled surfaces. Adhesive strength 90° [N / cm] Winding time [min] Comparison adhesive tape 1 Comparison adhesive tape 2 B6 with ESH 20 kGy 2 0,02 0,23 0,80 60 0,05 0,77 3,85 240 0,24 1,30 9,23 Bonding at low temperatures:

[0191] To verify their suitability for bonding at low temperatures, the adhesive tapes were bonded to ASTM steel at 0 °C as specified in Table 6. Comparison tape 1 is a 500 µm thick double-sided acrylic tape, manufactured according to the MT15 example from DE 10 2009 048036 A1. The adhesive strengths were measured as described in the test methods, except that the application time and the measurement were both performed at 0 °C.

[0192] It can be seen that the adhesive tape according to the invention, as shown in example B5, has excellent adhesive strength at 0 °C. Table 6: Bonding at 0 °C. Adhesive strength 90° [N / cm], measured at 0°C Winding time at 0°C Comparison adhesive tape 1 B5 with ESH 20 kGy 2 min 1 31 24 h 19 37 Testing methods

[0193] Unless otherwise stated, all measurements were taken at 23 °C and 50% relative humidity.

[0194] The mechanical and adhesive properties were determined as follows: DACP

[0195] Weigh 5.0 g of the test substance (the adhesive resin sample to be examined) into a dry vial and add 5.0 g of xylene (isomer mixture, CAS [1330-20-7], ≥ 98.5%, Sigma-Aldrich #320579 or equivalent). Dissolve the test substance at 130 °C and then cool to 80 °C. Any evaporated xylene is replenished with more xylene to restore the total amount to 5.0 g. Next, add 5.0 g of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone, CAS [123-42-2], 99%, Aldrich #H41544 or equivalent). Shake the vial until the test substance is completely dissolved. To achieve this, heat the solution to 100 °C. The sample vial containing the resin solution is then placed in a Novomatics Chemotronic Cool cloud point meter and heated to 110 °C. Cooling is performed at a rate of 1.0 K / min. The cloud point is then detected optically.The temperature at which the turbidity of the solution reaches 70% is recorded. The result is given in °C. The lower the DACP value, the higher the polarity of the test substance. Adhesive resin softening temperature

[0196] The softening temperature of an adhesive resin is determined according to the relevant methodology known as Ring & Ball, which is standardized according to ASTM E28. diameter

[0197] The determination of the mean diameter of the cavities formed by microballoons in a self-adhesive layer is carried out using cryogenic fracture edges of the adhesive strip under a scanning electron microscope (SEM) at 500x magnification. The diameter of each microballoon visible in SEM images of five different cryogenic fracture edges of the adhesive strip in the self-adhesive layer under investigation is determined graphically. The arithmetic mean of all diameters determined in the five SEM images represents the mean diameter of the cavities formed by the microballoons in the self-adhesive layer as defined in the present application.The diameters of the microballoons visible in the images are determined graphically by taking the maximum extent in any (two-dimensional) direction from the SEM images for each individual microballoon of the self-adhesive layer under investigation and considering it as its diameter. density

[0198] The density of an adhesive layer is determined by calculating the ratio of the amount of adhesive applied to the thickness of the adhesive layer applied to a substrate or liner.

[0199] The mass application can be determined by determining the mass of a section of such an adhesive mass layer applied to a substrate or liner, defined in terms of its length and width, minus the (known or separately determinable) mass of a section of the same dimensions of the substrate or liner used.

[0200] The thickness of an adhesive layer can be determined by measuring the thickness of a section of such an adhesive layer applied to a substrate or liner, defined in terms of its length and width, and subtracting the (known or separately determinable) thickness of a section of the substrate or liner of the same dimensions. The thickness of the adhesive layer can be determined using commercially available thickness gauges (probe gauges) with accuracies of less than 1 µm deviation. The present application uses the precision thickness gauge Mod. 2000 F, which has a circular probe with a diameter of 10 mm (flat). The measuring force is 4 N. The value is read 1 s after the load is applied. If thickness variations are detected, the mean value of measurements taken at at least three representative locations is given, specifically excluding measurements taken at creases, folds, spots, and the like. thickness

[0201] Just as the thickness of an adhesive layer can be determined, the thickness of a pressure-sensitive adhesive strip, a film carrier layer, or a liner can also be determined using commercially available thickness gauges (probe gauges) with accuracies of less than 1 µm deviation. The present application uses the precision thickness gauge Mod. 2000 F, which has a circular probe with a diameter of 10 mm (flat). The measuring force is 4 N. The value is read 1 s after the load is applied. If thickness variations are detected, the mean value of measurements at at least three representative locations is given, specifically excluding measurements taken at creases, folds, spots, and the like. Static glass transition temperature Tg, melting temperature, softening temperature

[0202] Glass transition points – also known as glass transition temperatures – particularly of polymers or polymer blocks, are determined by measurements using Dynamic Scanning Calorimetry (DSC) according to DIN 53 765, specifically sections 7.1 and 8.1, but with uniform heating and cooling rates of 10 K / min in all heating and cooling steps (see DIN 53 765; section 7.1; note 1). The sample weight is 20 mg. The melting point or softening point of polymers or polymer blocks is also determined in this way. proportion of 1,2-linked conjugated diene

[0203] The proportion of 1,2-linked conjugated diene in the B-block of vinyl aromatic block copolymer can be determined by 1H NMR. The following instrument was used for the spectroscopic investigation: 1H NMR: Bruker AMX 500 (500.14 MHz). The solvent signal δ(CHCl3) = 7.24 served as the standard. Chemical shifts are always given in ppm. Coupling constants J are given in Hertz [Hz]. The signal patterns are indicated as follows: s (singlet), bs (broad singlet), d (doublet), dd (doublet of the doublet), t (triplet), q (quintet), m (multiplet). Surface energies

[0204] Surface energies (surface tensions) are determined according to DIN ISO 8296. Test inks from Softal, for example, can be used for this purpose. These inks are available in the range of 30 to 72 mN / m. The ink is applied to the surface with a single stroke at 23 °C and 50% relative humidity. If the ink stroke contracts in less than 2 seconds, the measurement is repeated with an ink of lower surface energy until 2 seconds are reached. If the ink stroke remains unchanged for more than 2 seconds, the measurement is repeated with an ink of higher surface energy until 2 seconds are reached. The value indicated on the corresponding ink bottle then corresponds to the surface energy of the substrate. Thermal shear life - Static shear test SSZ

[0205] To determine the thermal shear life, also known as thermal shear strength, an adhesive strip is applied to a predetermined, rigid substrate (here, steel) in a climate chamber heated to 70 °C or 80 °C and subjected to a constant shear load. The holding time is measured in minutes. The temperatures used are given in the examples.

[0206] A double-sided adhesive strip, either 13 mm long and 20 mm wide or 25 mm long and 25 mm wide, is manually applied to a polished steel plate (test substrate) with a hole at one end. An identical steel plate is then manually applied in reverse orientation. The resulting bond is pressed with a force of 100 N / cm² for 60 seconds (0.260 kN for a 20 x 13 mm geometry and 0.625 kN for a 25 x 25 mm geometry).

[0207] The curing time between rolling and loading should be 24 hours, unless otherwise specified in the examples. Before loading, the sample is tempered in a heating oven for 15 minutes. The weight is then attached using S-shaped hooks and was 500g unless otherwise specified. The loads used, in kPa or N / cm² of the bonded area, are given in the examples.

[0208] An automatic counter now determines the time of shearing off the test specimens. The measurement is terminated after 10,000 minutes. For test specimens that have not yet fallen off after 10,000 minutes, the quality of the cohesive properties under heat can be further quantified by determining the slip distance or the deflection without slippage of the test specimen after 10,000 minutes using a displacement sensor.

[0209] The average of three measurements is determined. 90° adhesive strength (KK)

[0210] Unless otherwise specified, the adhesive strength is determined at 90° on steel under a test climate of 23 °C ± 1 °C and 50% ± 5% relative humidity. The samples are cut to a width of 20 mm and adhered to the steel substrate. Unless otherwise specified, the substrate is cleaned and conditioned before measurement. For this, the plate is first wiped with acetone and then left to air dry for 5 minutes to allow the solvent to evaporate. The side of the adhesive tape facing away from the test substrate is then covered with a 50 µm aluminum foil to prevent the sample from stretching during measurement. The test sample is then rolled onto the test substrate. For this, the tape is rolled back and forth five times with a 2 kg roller at a rolling speed of 10 m / min.Immediately after being rolled onto the substrate, it is inserted into a special holder, which allows the pattern to be peeled off vertically upwards at a 90° angle. Adhesive strength is measured using a Zwick tensile testing machine. The results are given in N / cm and are averaged from three measurements. Determination of the gel content

[0211] The carefully dried, solvent-free adhesive samples are sealed in a polyethylene (Tyvek) nonwoven bag. The gel value, i.e., the fraction of the polymer by weight that is not soluble in the mixture, is determined from the difference in sample weights before and after extraction with a mixture of gasoline / toluene / acetone. Additives that are not incorporated into the network even after ESH irradiation must be subtracted from the total sample weight before extraction.

Claims

1. Pressure-sensitive adhesive strip containing at least one layer SK1 of a self-adhesive composition based on vinylaromatic block copolymer and containing tackifying resin, wherein the at least one layer SK1 of the self-adhesive composition contains 20% to 60% by weight of at least one tackifying resin, based on the total weight of the self-adhesive composition layer, where the tackifying resin of layer SK1 comprises, to an extent of at least 75% by weight, hydrocarbon resin or terpene resin or a mixture of these, where the vinylaromatic block copolymer • is a mixture of linear block copolymers, • contains at least one polymer block A formed predominantly by polymerization of vinylaromatics, and • simultaneously contains at least one polymer block B formed predominantly by polymerization of conjugated dienes, where the proportion of 1,2-bonded conjugated diene, determined by the test method specified for 1H NMR, in the B block is less than 30% by weight, and • at least layer SK1 has been subjected to irradiation with electrons with a dose of 10 to 100 kGy, characterized in that the self-adhesive composition of layer SK1 has been foamed.

2. Pressure-sensitive adhesive strip according to either of the preceding claims, characterized in that the absolute density of the self-adhesive composition layer SK1 is 400 to 990 kg / m3.

3. Pressure-sensitive adhesive strip according to at least one of Claims 1 and 2, characterized in that the proportion of microballoons in the foamed layer SK1 is up to 12% by weight, based on the overall composition of the layer.

4. Process for producing a pressure-sensitive adhesive strip according to Claims 1 to 3, in which the self-adhesive composition is processed from solution or from the melt to give layer SK1, and layer SK1 is subjected to irradiation with electrons.

5. Use of a pressure-sensitive adhesive strip according to any of Claims 1 to 3 for bonding of surfaces having a surface energy, determined to DIN ISO 8296, of 50 mN / m or less.

6. Use of a pressure-sensitive adhesive strip according to any of Claims 1 to 3 for bonding of two surfaces, where one of the surfaces has a surface energy, determined to DIN ISO 8296, of 50 mN / m or less and the other surface has a surface energy of 35 mN / m or more.

7. Use of a double-sided pressure-sensitive adhesive strip according to any of Claims 1 to 3 for bonding of two components, where the bonding takes place at a temperature of not more than 10°C and where the components have different surface energies.

8. Use of a pressure-sensitive adhesive strip according to any of Claims 1 to 3 in a method of bonding components, in which the components are simultaneously mechanically bonded and adhesive-bonded by means of the pressure-sensitive adhesive strip.

9. Use of a pressure-sensitive adhesive strip according to any of Claims 1 to 3 for bonding of oil-contaminated substrates.