Pressure-sensitive adhesive composition

Abstract

The aim of the invention is to provide a pressure-sensitive adhesive composition based on at least one block copolymer, said adhesive composition having good or improved properties, in particular temperature stability and aging stability, and being suitable for use in elevated temperature ranges. This is achieved by a pressure-sensitive adhesive composition based on at least one block copolymer BC, which has at least one polymer block P(A) and at least one polymer block P(B), wherein - P(A), independently of one another, comprise homopolymer or copolymer blocks comprising a total of at least 80 wt. % of monomers A selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group; and - P(B), independently of one another, comprise homopolymer or copolymer blocks comprising a total of at least 80 wt.% of monomers B selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group. The adhesive composition is characterized in that - the monomers A contain a total at least 50 wt. % of one or more acrylate monomers A1 selected from the general structure CH2=C(H)(COOR1); where R1, in each occurrence, is independently selected from a linear or branched hydrocarbon group having 4 to 17 carbon atoms; and - the monomers B comprise a total of at least 60 wt.% of one or more (meth)acrylate monomers B1 selected from the general structure CH2=C(R2)(COOR3); where R2, in each occurrence, is independently selected from H and CH3; and R3, in each occurrence, is independently selected from an optionally substituted, cyclic or polycyclic alkyl group having at least 6 carbon atoms.

Description

[0001] pressure-sensitive adhesive

[0002] The invention relates to pressure-sensitive adhesives based on at least one block copolymer, which are characterized by increased temperature stability and increased cohesion with simultaneously high adhesive strength.

[0003] The demands on the stability of pressure-sensitive adhesives are continually increasing. In particular, these pressure-sensitive adhesives are expected to exhibit excellent adhesive properties even at high temperatures. To meet this demand, (meth)acrylate block copolymers have emerged as a promising solution. These materials combine the advantageous properties of classic (meth)acrylate copolymers, such as aging resistance, water-clear transparency, and inherent pressure-sensitive tack, with the properties of styrene block copolymers, such as thermoreversible physical crosslinking and high cohesion.

[0004] Disadvantages of styrene block copolymer-based pressure-sensitive adhesives (PSAs) include systems that utilize unsaturated polymer chains in the elastomer block, such as styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) block copolymers, and their low resistance to aging, ultraviolet radiation, thermal oxidative degradation, and ozonolysis. This means that the advantage of water-clear, transparent self-adhesive tapes cannot be fully utilized, as the PSA must be protected from light. This is achieved, for example, by light-absorbing additives such as titanium dioxide, the compounding of which results in non-transparent products. Styrene block copolymers with chemically saturated elastomer blocks, e.g.The hydrogenated analogues of SBS and SIS, styrene-ethylene / butylene-styrene (SEBS) and styrene-ethylene / propylene-styrene (SEPS), exhibit significantly improved aging resistance, therefore typically requiring no light-absorbing additives and thus being easier to process into water-clear products. A disadvantage, however, is that they typically do not achieve the good balance of bond strength and low re-peel forces known from SIS- and SBS-based pressure-sensitive adhesives. At the same time, if plasticizers (e.g., liquid resins, aliphatic oils), which are desirable for many formulations, are not used, the selection of sufficiently compatible adhesive resins is noticeably limited compared to, for example, SIS.

[0005] However, commercially available block copolymers based on (meth)acrylates are limited by the choice of monomers from which the various polymer blocks are formed and the resulting glass transition temperature(s) of the polymer blocks. Typically, commercially available block copolymers feature polymethyl methacrylate (PMMA) as the monomer of the hard (polymer) block, i.e., the block with a high glass transition temperature, as well as heat resistance, which is due to the glass transition temperature of PMMA. The limited use of monomers in commercial block copolymers means that the desired properties cannot be fully met at high temperatures. Therefore, there is a need for new, alternative block copolymer systems based on (meth)acrylates that exhibit very good or improved properties, especially at high temperatures.

[0006] Various studies have been conducted on processes that incorporate polar monomers, such as methacrylic acid esters or acrylic acid esters, in anionic polymerization. However, such polar monomers contain a residue, such as a carbonyl group, that is easily subject to nucleophilic attack. Therefore, in the anionic polymerization of a polar monomer, it is relatively difficult to create good conditions for living polymerization because a side reaction of the monomer or an intermolecular cyclization reaction (so-called "backbiting") occurs at the growing end of the resulting polymer. Thus, the choice of monomers is limited, which is why there is a need for alternative block copolymers based on different building blocks. Furthermore, anionic polymerization places very high demands on the reaction conditions and reaction control, as well as the purity of the reactants.

[0007] The object of the invention is to provide a pressure-sensitive adhesive based on at least one block copolymer, which essentially comprises (meth)acrylic acid derivatives, which exhibits good adhesive strengths, in particular on polar adhesive substrates, as well as good shear resistance times. A first and general subject matter of the invention, with which these objects are achieved, is a pressure-sensitive adhesive based on at least one block copolymer BC, which comprises at least one polymer block P(A) and at least one polymer block P(B), wherein

[0008] P(A) independently of one another homo- or copolymer blocks comprising a total of at least 80 wt.% of monomers A selected from the group consisting of methacrylic acid esters, methacrylamides and monomers having at least one polymerizable vinyl group;

[0009] P(B) independently of one another comprise homo- or copolymer blocks comprising a total of at least 80 wt.% of monomers B selected from the group consisting of methacrylic acid esters, methacrylamides and monomers having at least one polymerizable vinyl group; characterized in that the monomers A comprise a total of at least 50 wt.% of one or more acrylate monomers A1 ("monomers A1") selected from the general structure CH2=C(H)(COOR 1 ) include; where R 1 at each occurrence is independently selected from a linear or branched alkyl radical having 4 to 17 carbon atoms (C atoms);

[0010] - the monomers B comprise at least 60 wt.% of one or more (meth-)acrylate monomers B1 (“monomers B1”) selected from the general structure CH2=C(R 2 )(COOR 3 ) include; where R 2 is independently selected at each occurrence from H and CH3; and R 3at each occurrence is independently selected from an optionally substituted, cyclic or polycyclic alkyl radical having at least 6 carbon atoms, preferably having 6 to 14 carbon atoms.

[0011] In one embodiment, the pressure-sensitive adhesive is suitable for use at elevated temperatures, in particular in the temperature range up to 70 °C.

[0012] Details and embodiments of the invention are described below. Those embodiments that are designated as preferred in any form below are combined in particularly preferred embodiments with features of other embodiments that are designated as preferred in any form below. Combinations of two or more of the embodiments that are designated as particularly preferred in any form below are thus very particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment that is designated as preferred to any extent is combined with one or more further features of other embodiments that are designated as preferred to any extent.

[0013] To the extent that both specific amounts or proportions of an element and preferred embodiments of the element are disclosed below, the specific amounts or proportions of the preferably configured elements are also disclosed. Furthermore, it is disclosed that, with the corresponding specific total amounts or total proportions of the elements, at least some of the elements can be preferably configured, and in particular, that preferably configured elements can in turn be present in the specific amounts or proportions within the specific total amounts or total proportions.

[0014] According to expert understanding, a pressure-sensitive adhesive is an adhesive that possesses pressure-sensitive adhesive properties, i.e., the ability to form a permanent bond to a substrate even under relatively light pressure. Such adhesives or pressure-sensitive adhesive tapes are generally permanently tacky even at room temperature, meaning they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even under light pressure. Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be considered an extremely viscous liquid with an elastic component, which consequently possesses characteristic viscoelastic properties that lead to the permanent tackiness and pressure-sensitive adhesive capacity described above.It is assumed that mechanical deformation of pressure-sensitive adhesives results in both viscous flow processes and the buildup of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are particularly necessary to achieve cohesion. The relationships between rheology and pressure-sensitive tack are well known in the art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology", Third Edition, (1999), pages 153 to 203. To characterize the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G") are usually used; these can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer.In the context of the present invention, an adhesive is preferably understood as pressure-sensitive adhesive and thus as a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range from 10° to 10. 1 rad / sec G' and G“ each at least partly in the range of 10 3 up to 10 7 Pa lie.

[0015] Block copolymers are macromolecules consisting of two or more covalently bonded polymer blocks, for example, polymer block A "P(A)" and polymer block B "P(B)". The adjacent polymer blocks consist of constitutional units derived from different monomer species or from the same monomer species, but with a different composition or sequence distribution of constitutional units. The specific molecular structure of the blocks usually results in microphase separation and thus in the formation of nanoscale morphologies.

[0016] The block copolymer according to the invention is a polymer system. The term "polymer system" refers, according to the invention, to both a single polymer and a mixture of two or more different polymers. In accordance with the expert's understanding, a "polymer" or "a single polymer" is understood not only to refer to a single macromolecule, but also to a multitude of macromolecules that originate from one and the same polymerization process and have a specific molecular weight distribution among themselves.

[0017] The pressure-sensitive adhesive of the invention is based on at least one block copolymer BC. "Based on" or "based on" or "based on" means here that the properties of the pressure-sensitive adhesive are determined at least strongly by the fundamental properties of the at least one block copolymer BC, although it is of course not excluded that these properties may be further influenced by the use of modifying auxiliaries or additives in a composition. In particular, this may mean that the proportion of the at least one block copolymer BC in the total mass of the pressure-sensitive adhesive is more than 50 wt. %.

[0018] In one embodiment, the pressure-sensitive adhesive of the invention comprises at least one block polymer BC to an extent of at least 50% by weight, preferably at least 60% by weight, particularly preferably 70% by weight, based on the total weight of the pressure-sensitive adhesive.

[0019] The block copolymer BC comprises at least one polymer block (A) and at least one polymer block P(B). The polymer blocks P(A) independently represent homopolymer or copolymer blocks of monomer A at each occurrence. The polymer blocks P(B) independently represent homopolymer or copolymer blocks of monomer B at each occurrence.

[0020] The polymer blocks P(A), as described in the main claim or in the advantageous embodiments, can be polymer chains of a single monomer type from monomers A or copolymers of monomers of different structures from monomers A. In particular, the monomers A used can vary in their chemical structure and / or in the length of the alkyl radical. The polymer blocks thus span the range from completely homogeneous polymers to polymers from monomers of the same basic chemical structure but different chain lengths and those with the same carbon number but different isomers to randomly polymerized blocks from monomers of different lengths with different isomerism from group A. The same applies to the polymer blocks P(B) with regard to the monomers B, which can differ, for example, in their cyclic or polycyclic alkyl unit.

[0021] An advantageous embodiment is when the block copolymers have a symmetrical structure such that polymer blocks P(A) are identical in chain length and / or chemical structure and / or that polymer blocks P(B) are identical in chain length and / or chemical structure.

[0022] Furthermore, all "unsymmetrical" structures are included, in which all of the polymer blocks P(A) and P(B) meet the above-mentioned criteria, but the chemical or structural identity of the individual building blocks is not required.

[0023] The block copolymer according to the invention, which is present in at least two phases, comprises at least one polymer block P(A) and at least one polymer block P(B). The polymer blocks P(A) represent, at each occurrence, independently of one another, homo- or copolymer blocks of monomers A, where the monomers A comprise one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group. The polymer blocks P(B) represent, at each occurrence, independently of one another, homo- or copolymer blocks of monomers B, where the monomers B comprise one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group.

[0024] The monomers A comprise one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group at least 80 wt.%, alternatively 85 wt.%, more preferably at least 90 wt.%, particularly preferably at least 95 wt.%, in particular at least 98 wt.%. Most preferably, the monomers A comprise exclusively one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group.

[0025] The monomers A according to the invention comprise, in total, at least 50% by weight, based on the total weight of the monomers A, one or more acrylate monomers A1 selected from the general structure CH2=C(H)(COOR 1 ); where R 1at each occurrence is independently selected from a linear or branched alkyl radical having 4 to 17 carbon atoms.

[0026] In further embodiments, the monomers A according to the invention comprise a total of at least 75% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, or 100% by weight, based on the total weight of the monomers A, of one or more monomers A1.

[0027] In one embodiment, the monomers A1 are selected from the group consisting of n-butyl acrylate, iso-butyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 2-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, iso-octyl acrylate, n-nonyl acrylate, isononyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate, isodecyl acrylate, lauryl acrylate, tetradecyl acrylate, heptadecyl acrylate.

[0028] The monomers B comprise one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group at least 80 wt.%, alternatively 85 wt.%, more preferably at least 90 wt.%, particularly preferably at least 95 wt.%, in particular at least 98 wt.%. Most preferably, the monomers B comprise exclusively one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group.

[0029] The monomers B according to the invention comprise at least 60% by weight of one or more (meth)acrylate monomers B1 selected from the general structure CH2=C(R 2 )(COOR 3 ) include; where R 2 is independently selected at each occurrence from H and CH3; and R 3at each occurrence is independently selected from an optionally substituted, cyclic or polycyclic alkyl radical having at least 6 carbon atoms, preferably having 6 to 14 carbon atoms. Thus, the one or more (meth)acrylate monomers B1 as R 3 a cyclic alkyl radical which optionally has further substituents or a polycyclic alkyl radical which optionally has further substituents.

[0030] Polycyclic alkyl radicals R 3Examples include bridged cycloalkyl radicals, such as a norbornyl radical or an isobornyl radical, but also dicyclic and polycyclic radicals such as an adamantyl radical, a tricyclodecanyl radical, or a dicyclopentanyl radical. In this document, the number of C atoms of a substituent refers to the total number of C atoms present in the substituent, including optional additional substituents. Thus, the norbornyl radical is a cyclic carbon radical with 7 C atoms, the isobornyl radical is a cyclic carbon radical with 10 C atoms, the adamantyl radical is a polycyclic radical with 10 C atoms, and the dicyclopentanyl radical is a polycyclic radical with 10 C atoms. In an exemplary substitution of a norbornyl residue with a CN group, this residue would be referred to as a cyclic residue with 8 C atoms.

[0031] R 3may optionally have one or more substituents. For example, the optional substituents are independently selected at each occurrence from the group consisting of CN and halogens. Preferably, the substituent R 3 a cyclic or polycyclic basic structure containing further alkyl radicals, preferably C1-C6 alkyl radicals, particularly preferably methyl or ethyl, most preferably methyl. For example, the isobornyl radical (C10) has the cyclic basic structure of the norbornyl radical (C7), which contains three further methyl groups (3x C1).

[0032] In further embodiments, the monomers B according to the invention comprise a total of at least 75% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, or 100% by weight, based on the total weight of the monomers B, of one or more monomers B1.

[0033] In one embodiment, the monomers B1 are selected from the group consisting of cyclohexyl acrylate, tert-butylcyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl methacrylate, 2-acryloyloxy-2-methyladamantane, norbornyl acrylate, dicyclopentanyl acrylate, tricyclodecanol acrylate and isobornyl acrylate.

[0034] In one embodiment, the monomers B according to the invention comprise at least 60% by weight of one or more (meth)acrylate monomers B1 selected from the general structure CH2=C(R 2 )(COOR 3 ) include; where R 2 is equal to H; and R 3 is independently selected at each occurrence from an optionally substituted, cyclic or polycyclic alkyl radical having at least 6 C atoms.

[0035] In a preferred embodiment, the monomers B1 are selected from the general structure CH2=C(H)(COOR 3 ); where R 3at each occurrence is independently selected from a cyclic or polycyclic alkyl radical which has a basic structure with at least 6 C atoms and optionally has one or more methyl or ethyl substituents, wherein R 3 has a total of 6 to 14, preferably 7 to 12, carbon atoms. In a particularly preferred embodiment, the monomers B1 are selected from the general structure CH2=C(H)(COOR 3 ); where R 3 at each occurrence is independently selected from a cyclic or polycyclic alkyl radical which has a basic structure with at least 6 C atoms and optionally has one or more methyl substituents, where R 3 has a total of 6 to 14, preferably 7 to 12, carbon atoms.

[0036] Surprisingly, good bond strengths and shear strengths were observed for acrylate compounds as monomers B1, which were only achieved with methacrylate compounds or styrene. Furthermore, acrylate compounds are characterized by their good commercial availability.

[0037] In one embodiment, R 3 a cyclic or polycyclic alkyl radical having 6 to 14 C atoms, preferably 7 to 12 C atoms.

[0038] In one embodiment, R 3 a polycyclic alkyl radical with at least 7 C atoms.

[0039] In one embodiment, R 3 a bi- or tricyclic alkyl radical with at least 7 C atoms.

[0040] In a preferred embodiment, the monomers B1 are selected from the group consisting of norbornyl acrylate, tricyclodecanol acrylate and dicyclopentanyl acrylate.

[0041] In one embodiment, R 3a tricyclic alkyl radical with 10 C atoms.

[0042] In a preferred embodiment, R 3 a dicyclopentanyl substituent.

[0043] In a particularly preferred embodiment, the monomers B1 are dicyclopentanyl acrylate.

[0044] In one embodiment, the block copolymer comprises less than 17 wt% isobornyl acrylate.

[0045] In a preferred embodiment, the monomers B1 are not isobornyl acrylate. For adhesives containing isobornyl acrylate, allergic contact dermatitis has been observed when applied to the skin and in body-wear applications (such as watches / smartwatches).

[0046] The block copolymer according to the invention is a polymer system which preferably exists in at least two phases. A person skilled in the art understands this to mean that one phase is rich in one component of the block copolymer, for example the polymer block P(A), or consists essentially of this component, and the other phase is rich in another component, for example the polymer block P(B), or consists essentially of this component. The presence of small amounts of one component in the other, which does not preclude the formation of multiphases, is considered irrelevant. If the block copolymer according to the invention has more than two phases, the above applies accordingly to all of these phases.

[0047] The phase separation is particularly preferably realized in such a way that discrete regions (“domains”) that are rich in polymer block P(A) or polymer block P(B) - i.e., are essentially formed from polymer block P(A) or polymer block P(B) - are present in a continuous matrix that is rich in the other polymer block - i.e., is essentially formed from the other polymer block. A block copolymer according to the invention is considered to be present in at least two phases in particular if at least one of the following criteria a) - c) is met: a) Phase boundaries can be identified in a height profile analysis or an analysis of the Young's modulus of an atomic force microscopy (AFM) image of the block copolymer. b) At least two independent glass transition temperatures are obtained from a differential scanning calorimetry (DSC) measurement carried out on the block copolymer.c) At least two tan δ maxima are obtained from a dynamic mechanical analysis (DMA) performed on the block copolymer.

[0048] According to the invention, a block copolymer BC present in at least two phases also comprises a microphase-separated block copolymer, i.e. a polymer system in which the discontinuous phase is present in microscopically fine distribution.

[0049] In one embodiment, the pressure-sensitive adhesive of the invention is based on at least one block polymer BC present in at least two phases.

[0050] The process according to the invention is intended to result in a polymer system consisting of at least two phases. Another aim of the invention was to provide the two- or multi-phase polymer system with the highest possible cohesion. Therefore, it seemed important to consider these and, if necessary, other properties of the final polymer system when selecting the monomers used in the two polymerization steps.

[0051] Monomers with a glass transition temperature of the respective homopolymer of < 0 °C, more preferably < -10 °C, in particular < -20 °C, i.e. monomers which are particularly suitable for the polymer block P(A), are, for example, selected from the group consisting of ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, iso-amyl acrylate, n-hexyl acrylate, 2-heptyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, iso-octyl acrylate, n-nonyl acrylate, iso-nonyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate, iso-decyl acrylate, lauryl acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, 2-cyanoethyl acrylate, 2- (2-Ethoxyethoxy)ethyl acrylate, phenoxyethyl acrylate, iso-stearyl acrylate, docosyl acrylate, and 2-[2-(2-Methoxyethoxy)-ethoxy]ethyl acrylate.

[0052] Monomers with a glass transition temperature of the respective homopolymer of > 50 °C, more preferably > 75 °C, in particular > 100 °C, i.e. monomers which are particularly suitable for the polymer block P(B), are, for example, selected from the group consisting of dicyclopentanyl acrylate, isobornyl acrylate, norbornyl acrylate, benzyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, 4-[(6-acryloyloxy)hexyloxy]4'-cyanobiphenyl, N-succinimidyl acrylate, 1-ethylcyclopentyl acrylate, N-tert-octylacrylamide, N-tert-butylacrylamide, dimethylacrylamide, diethylacrylamide, acrylamide, N-[3-(dimethylamino)propyl]acrylamide, diacetoneacrylamide, N-(butoxymethyl)acrylamide, N-phenylacrylamide, N-[2-(Dimethylamino)ethyl]acrylamide, N-[2-(Diethylamino)ethyl]acrylamide, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, glycerol formal methacrylate, 2-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, 9-anthrylmethyl methacrylate,2-Ethyl-2-adamantylmethacrylat, 2- (Acetoacetyloxy)ethylmethacrylat, 2-lsopropyl-2-methacryloyloxyadamantan, iso- Propylmethacrylat, iso-Butylmethacrylat, tert-Butylmethacrylat, Furfurylmethacrylat, 2- Methacryloyloxy-2-methyladamantan, Phenylmethacrylat, N-Succinimidylmethacrylat, 2-(tert- Butylamino)ethylmethacrylat, 2-Cyclohexylpropan-2-ylmethacrylat, 1 -Adamantylmethacrylat, 1 -Methylcyclopentylmethacrylat, 3-Dimethylaminopropylmethacrylamid, N-tert- Butylmethacrylamid, N-(Methoxymethyl)methacrylamid, N,N-Dimethylmethacrylamid, Methacrylamid, N-Phenylmethacrylamid, N,N-Dimethylmethacrylamid, N-Vinylformamid, N- Vinylpyrrolidon, N-Vinylcaprolactam, N-Vinylcrbazol, N-Vinylimidazol, Vinylmethyloxazolidinon und N-Vinyl-N-methylacetamid.,

[0053] Against this background, in one embodiment of the invention, the monomers A comprise a total of at least 50 wt.%, more preferably a total of at least 60 wt.%, in particular a total of at least 75 wt.% of one or more monomers having a glass transition temperature of the homopolymer in question of <0°C, more preferably of <-10°C, in particular of <-20°C; and the monomers B comprise a total of at least 60 wt.%, more preferably a total of at least 70 wt.%, in particular a total of at least 80 wt.% of one or more monomers having a glass transition temperature of the homopolymer in question of >50°C, more preferably of >75°C, in particular of >100°C, wherein - unless otherwise stated - the glass transition temperatures are determined by means of Method 1 (see section on measurement and test methods).

[0054] In a further development of this embodiment, the monomers A preferably comprise a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight of one or more monomers A1 and the monomers B comprise a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight of one or more monomers B1.

[0055] More preferably, the monomers A comprise a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight of one or more monomers selected from the group consisting of n-butyl acrylate, iso-amyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, iso-octyl acrylate, n-octyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate and isodecyl acrylate; and the monomers B comprise a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight of one or more monomers selected from the group consisting of 3,3,5-trimethylcyclohexyl acrylate, dicyclopentanyl acrylate, isobornyl acrylate, tricyclodecanol acrylate, norbornyl acrylate.

[0056] In a further development of this embodiment, the monomers A preferably comprise a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight of one or more monomers A1, a total of at most 35% by weight, more preferably a total of at most 25% by weight, in particular a total of at most 20% by weight of one or more monomers selected from the group consisting of dicyclopentanyl acrylate, tricyclodecanol acrylate, isobornyl acrylate, norbornyl acrylate, methyl methacrylate, dimethylacrylamide, diethylacrylamide, 4-tert-butylcyclohexyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate and cyclohexyl acrylate and a total of at most 10% by weight of one or more functionalized monomers; and the monomers B comprise a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight.-% one or more monomers B1 ; and a total of not more than 10% by weight of one or more functionalized monomers, wherein the functionalized monomers are selected from the group consisting of hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 4-hydroxyethylacrylamide, acrylic acid, methacrylic acid, 2-acryloyloxyethyl succinate, methacryloxyethyl succinate, sulfoethyl methacrylate, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexyl methyl acrylate, 3,4-epoxycyclohexyl methyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, 4-hydroxybutyl methacrylate glycidyl ether, isocyanatoethyl acrylate, isocyanatoethyl methacrylate, 2-[2-(Methacryloyloxy)ethyloxy]ethyl isocyanate, 2-[2-(Acryloyloxy)ethyloxy]ethyl isocyanate and a, a-dimethyl-m-isopropenyl benzyl isocyanate.

[0057] In particular, the monomers A comprise a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight of one or more monomers selected from the group consisting of n-butyl acrylate, iso-amyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, iso-octyl acrylate, n-octyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate and iso-decyl acrylate; to a total of not more than 35 wt.%, more preferably to a total of not more than 25 wt.%, in particular to a total of not more than 20 wt.% of one or more monomers selected from the group consisting of dicyclopentanyl acrylate, isobornyl acrylate, norbornyl acrylate, methyl methacrylate, dimethylacrylamide and to a total of not more than 10 wt.% of one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate,

[0058] Hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3,4-epoxycyclohexyl methyl acrylate, 3,4-epoxycyclohexyl methyl methacrylate, glycidyl acrylate and glycidyl methacrylate; and the monomers B comprise a total of at least 60 wt.%, more preferably a total of at least 70 wt.%, in particular a total of at least 80 wt.% of one or more monomers selected from the group consisting of dicyclopentanyl acrylate, isobornyl acrylate and norbornyl acrylate; and a total of not more than 10 wt.% of one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3,4-epoxycyclohexyl methyl acrylate, 3,4-

[0059] Epoxycyclohexylmethyl methacrylate, glycidyl acrylate and glycidyl methacrylate.

[0060] In one embodiment, monomers A and B comprise a total of not more than 15 wt. %, preferably a total of not more than 10 wt. %, particularly preferably a total of not more than 5 wt. % methyl methacrylate. In a further development of this embodiment, at least monomers B are substantially free of methyl methacrylate; more preferably, they are free of methacrylic acid esters and methacrylamides; in particular, they are free of any methacrylic compounds.

[0061] Preferably, the monomers A are substantially free of methyl methacrylate; more preferably, they are free of methacrylic acid esters and methacrylamides; in particular, they are free of any methacrylic compounds.

[0062] In a further development of these embodiments, monomers A and B are substantially free of methyl methacrylate; more preferably, they are free of methacrylic acid esters and methacrylamides; in particular, they are free of any methacrylic compounds.

[0063] Essentially free of methyl methacrylate means that the monomers (A and / or B) contain less than 1 wt.%, preferably less than 0.5 wt.%, based on the total composition of methyl methacrylate, particularly preferably no methyl methacrylate.

[0064] As has been shown, the exclusion of the above-mentioned compounds has a beneficial effect on the polymerization rate.

[0065] In one embodiment, the block copolymer BC has a weight-average molar mass M w > 200,000 g / mol, preferably M w s 350,000 g / mol, particularly preferably M w s 500,000 g / mol.

[0066] In one embodiment, the block copolymer BC has a polydispersity PD that is greater than 2, alternatively greater than 4 or greater than 6.

[0067] In one embodiment, the at least one polymer block P(A) and / or the at least one polymer block P(B) has a weight-average molar mass Mw > 100,000 g / mol, preferably Mw > 150,000 g / mol, particularly preferably Mw > 200,000 g / mol.

[0068] In one embodiment, the block copolymer BC is present as a multimodal block copolymer. A multimodal block copolymer is defined as a block copolymer with at least a bimodal mass distribution, i.e., a molar mass distribution with at least two maxima.

[0069] In one embodiment, the block copolymer BC comprises polymer blocks P(B) in a proportion of between 5 and 49 wt.%; preferably between 7.5 and 35 wt.%; in particular between 10 and 30 wt.%; based on the total of the polymer blocks P(A) and P(B) of the block copolymer BC. The ratios of the chain lengths of the block copolymers P(A) to those of the block copolymers P(B) are very advantageously selected such that the block copolymers P(B) are present as a disperse phase ("domains") in a continuous matrix of the polymer blocks P(A). This is preferably the case with a content of polymer blocks P(B) of less than approximately 25 wt.%.The formation of hexagonally packed cylindrical domains of the polymer blocks P(B) is also possible within the meaning of the inventive teaching, but is usually less preferable due to the less favorable tensile / elongation characteristics of corresponding materials and the structural anisotropy of the resulting pressure-sensitive adhesives induced by the domain structure. By asymmetrically designing the triblock copolymers, where the block lengths of the terminal polymer blocks P(B) are different in linear systems, the content of polymer blocks P(B) at which the system still forms a spherical morphology can be increased to above approximately 30 wt. %. This is particularly preferable when an increase in the internal strength of the pressure-sensitive adhesive is necessary, as well as to improve the mechanical properties.

[0070] In one embodiment, the structure of at least one block copolymer BC, preferably several or all block copolymers BC, can be achieved by one or more of the following general

[0071] Formulas are described:

[0072] - P(A)-P(B)-P(A) (la),

[0073] - P(B)-P(A)-P(B) (Ib),

[0074] - P(B)-P(A)-P(B)-P(A)-P(B) (Ha),

[0075] - P(A)-P(B)-P(A)-P(B)-P(A) (Hb),

[0076] - [P(A)-P(B)] n X (Illa),

[0077] - [P(B)-P(A)] n X (111b),

[0078] - [P(B)-P(A)-P(B)] n X (IVa),

[0079] - [P(A)-P(B)-P(A)] n X (IVb),

[0080] - [P(A)-P(B)] n X[P(B)] m (Va),

[0081] - [P(B)-P(A)] n X[P(A)] m (Vb), where n = 2 to 12, m = 1 to 12 and X represents a di- or multifunctional branching region.

[0082] The polymer blocks P(A), as described in the main claim or in the advantageous embodiments, can be polymer chains of a single monomer type of monomer A or copolymers of monomers of different structures from monomer A. In particular, the monomers A used can vary in their chemical structure and / or side chain length. The polymer blocks thus span the range from completely homogeneous polymers to polymers of monomers of the same basic chemical structure but different chain lengths and those with the same carbon number but different isomerism to randomly polymerized blocks of monomers of different lengths with different isomerism from group A. The same applies to the polymer blocks P(B) with regard to the monomers from group B.

[0083] The unit P(A)-P(B)-P(A) can be symmetrical [corresponding to P 1 (A)-P(B)-P 2(A) with P 1 (A) = P 2 (A)] as well as asymmetrically [approximately according to the formula P 3 (A)-P(B)-P 4 (A) with P 3 (A) P 4 (A), but both P 3 (A) and P 4 (A) are each polymer blocks in the sense of the definition for P(A)].

[0084] An advantageous embodiment is when at least one block copolymer, preferably several or all block copolymers, have a symmetrical structure such that polymer blocks P(A) are identical in chain length and / or chemical structure and / or that polymer blocks P(B) are identical in chain length and / or chemical structure. P 3 (A) and P 4 (A) may differ in particular in their chemical composition and / or their chain length.

[0085] In a preferred embodiment, at least one block copolymer BC, preferably several or all block copolymers BC, has at least one, particularly preferably two terminal groups P(B).

[0086] For advantageous further development according to the invention, adhesive resins can be admixed with the block copolymer-containing pressure-sensitive adhesives. In principle, all resins soluble in the corresponding polymer block P(A) can be used. Suitable adhesive resins include, among others, rosin and rosin derivatives (rosin esters, including rosin derivatives stabilized by, for example, disproportionation or hydrogenation), polyterpene resins, terpene-phenolic resins, alkylphenol resins, aliphatic, aromatic, and aliphatic-aromatic hydrocarbon resins, to name just a few. Resins that are preferably compatible with the polymer block (A) are primarily selected. The weight fraction of the resins in the block copolymer is typically up to 40 wt. %, more preferably up to 30 wt. %. For a specific embodiment of the invention, resins that are compatible with the polymer block P(B) can also be used.

[0087] Furthermore, plasticizers (plasticizers), fillers (e.g., fibers, carbon black, zinc oxide, titanium dioxide, chalk, solid or hollow glass spheres, microspheres made of other materials, silica, silicates), nucleating agents, blowing agents, compounding agents, and / or anti-aging agents, e.g., in the form of primary and secondary antioxidants or light stabilizers, can optionally be added. The internal strength (cohesion) of the pressure-sensitive adhesive is preferably generated by the physical crosslinking of the polymer blocks P(B). The resulting physical crosslinking is typically thermoreversible. For non-reversible crosslinking, the pressure-sensitive adhesives can additionally be chemically crosslinked. For this purpose, the pressure-sensitive adhesives containing acrylate block copolymers can optionally contain compatible crosslinking substances. Suitable crosslinkers include, for example, metal chelates, multifunctional isocyanates, multifunctional amines, or multifunctional alcohols.Multifunctional acrylates can also be used advantageously as crosslinkers for actinic irradiation.

[0088] In a further embodiment of the pressure-sensitive adhesive composition designed according to the invention, polymer blocks P(A) and / or P(B) are functionalized in such a way that thermally initiated crosslinking can be carried out. Crosslinkers that can be favorably selected include epoxides, aziridines, isocyanates, polycarbodiimides, and metal chelates, to name just a few.

[0089] For optional crosslinking with UV light, UV-absorbing photoinitiators are added to the polyacrylate-containing block copolymers used in the systems according to the invention. Useful photoinitiators that are very easy to use are benzoin ethers, such as benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones, such as 2,2-diethoxyacetophenone (available as Irgacure 651® from Ciba Geigy®), 2,2-dimethoxy-2-phenyl-1-phenylethanone, dimethoxyhydroxyacetophenone, substituted α-ketols, such as 2-methoxy-2-hydroxypropiophenone, aromatic sulfonyl chlorides, such as 2-naphthylsulfonyl chloride, and photoactive oximes, such as benzoin methyl ether and benzoin isopropyl ether. B. 1-Phenyl-1,2-propanedione-2-(0-ethoxycarbonyl)oxime.

[0090] In an alternative embodiment, the pressure-sensitive adhesives of the invention do not contain a crosslinker.

[0091] In a preferred embodiment, the pressure-sensitive adhesive according to the invention has an adhesive strength to steel, determined according to Method 5, of at least 3 N / cm.

[0092] In a preferred embodiment, the pressure-sensitive adhesive according to the invention has a SAFT value, determined according to Method 7, of at least 90 °C, preferably of at least 120 °C.

[0093] In a preferred embodiment, the pressure-sensitive adhesive according to the invention has a shear strength at room temperature, determined by Method 4, of at least 10,000 minutes. In a particularly preferred embodiment, the pressure-sensitive adhesive according to the invention has a shear strength at 70°C, determined by Method 4, of at least 100 minutes, preferably at least 300 minutes.

[0094] Very particularly preferred embodiments of the pressure-sensitive adhesives according to the invention have an adhesive strength to steel, determined by method 5, of at least 3 N / cm; a SAFT value, determined by method 7, of at least 90°C, preferably of at least 120°C; a shear strength at room temperature, determined by method 4, of at least 10,000 minutes and a shear strength at 70°C, determined by method 4, of at least 100 minutes, preferably of at least 300 minutes.

[0095] The invention further provides a process for producing a pressure-sensitive adhesive according to the invention based on at least one block copolymer BC, characterized in that at least one polymerization step takes place in a closed shell and / or at least one polymerization step is a RAFT polymerization.

[0096] To produce the block copolymers BC for the pressure-sensitive adhesive composition of the invention, in principle, all controlled or living polymerization processes can be used, as can combinations of various controlled polymerization processes. Examples of these include, without claiming to be exhaustive, anionic polymerization, ATRP, nitroxide / TEMPO-controlled polymerization, or, more preferably, the RAFT process, i.e., in particular those processes that allow control of block lengths, polymer architecture, or even, but not necessarily, the tacticity of the polymer chain.

[0097] In one embodiment, the block copolymer BC is prepared in two polymerization steps, wherein the first polymerization step is carried out in the presence of a RAFT regulator.

[0098] The process for producing the at least one block copolymer BC comprises the following steps: a) the polymerization of a polymer block from monomers A to form the polymer block P(A) or from monomers B to form the polymer block P(B); and b) the polymerization of a further polymer block from monomers A to form the polymer block (A) or from monomers B to form the polymer block (B) onto the polymer block from step a) to form a block copolymer present in at least two phases; wherein the monomers A and the monomers B are each used in one of the polymerization steps a) or b) and a RAFT regulator is preferably used in step a). In a further development, at least one polymerization step takes place in a closed shell.

[0099] The RAFT polymerization of step a) can, in principle, be carried out in any desired manner. For example, it can be carried out in solvent, particularly in a conventional reactor designed for such polymerizations.

[0100] The RAFT polymerization of step b) can also, in principle, be carried out in any desired manner. For example, it can be carried out in solvent, particularly in a conventional reactor designed for such polymerizations.

[0101] In one embodiment, the polymerization of step a) takes place in a reactor, in particular in a reactor designed for processing highly viscous masses, or in a closed shell; more preferably, it takes place in a planetary mixer or in a closed shell.

[0102] The polymerization of step a) is also preferably carried out in the absence of solvent. Solvent concentrations in very small ranges, e.g., resulting from production residues or in the range of the ubiquitous concentration, are considered to be irrelevant.

[0103] "RAFT polymerization" stands for "reversible addition-fragmentation chain transfer polymerization." This refers to a polymerization in which reaction control is achieved through reversible chain transfer reactions. An active, growing radical chain adds to a special regulator, the so-called RAFT agent, which is already linked to another chain and thus exists as a higher-molecular-weight RAFT agent (macro-RAFT agent). The addition of the active radical chain creates an intermediate whose structure allows it to fragment in various directions. This process again produces a macro-RAFT agent and an active radical chain available for propagation, although the latter does not necessarily have to correspond to the previously active radical chain. In this way, the propagation probability is evenly distributed across all chains, typically resulting in a narrow molecular weight distribution.

[0104] In a preferred embodiment of this invention, the polymerization of step a) and step b) is a controlled radical polymerization, particularly preferably a RAFT polymerization.

[0105] According to the above, at least one of the polymerization steps, preferably all polymerization steps, is carried out in the presence of at least one regulator substance containing at least one sequence -SC(=X)-, wherein X represents S, O or NR', where R' represents an organic radical. The regulator substance containing at least one sequence -SC(=X)- is preferably selected from the group consisting of

[0106] Dithioesters, i.e. compounds of the general structure (1)

[0107] (1 );

[0108] Dithiocarbonates, i.e. compounds of the general structure (2)

[0109] (2);

[0110] Xanthates, i.e. compounds of the general structure (3)

[0111] (3);

[0112] Dithiocarbamates, i.e. compounds of the general structure (4)

[0113] (4);

[0114] Trithiocarbonates, i.e. compounds of the general structure (5)

[0115] (5); and

[0116] Imido-dithiocarbonates, i.e. compounds of the general structure (6) wherein in the general structures (1) to (6), the substituents R each independently represent an organic or inorganic, preferably an organic, radical. In particular, at least one substituent R in the general structures (1) to (6) comprises a polymer chain formed during the polymerization in the relevant step.

[0117] Particularly preferably, the regulator substance contains at least one sequence -SC(=X)- selected from trithiocarbonates and xanthates; in the above sense, therefore, preferably from compounds according to the general structures (3) and (5).

[0118] Very particularly preferably, the regulator substance containing at least one sequence -S- C(X)- in its original state, i.e. still without encompassed growing polymer chains, is selected from the group consisting of dibenzyl trithiocarbonate, O-ethyl-S-(1-methyloxycarbonyl)ethyl xanthate, 1,4-phenylenebis(methylene)didodecyl tricarbonotrithioate, 2,2'-[carbonothioylbis(thio)]bis[2-methylpropanoic acid] and 4-cyano-4-

[0119] (((dodecylthio)carbonothioyl)thio)pentanoic acid.

[0120] For advantageous further development according to the invention, initiator systems can also be used in the production process, in particular thermally decomposing radical-forming azo or peroxo initiators. In principle, however, all conventional initiators known for acrylates are suitable. The production of C-centered radicals is described in Houben-Weyl, Methods of Organic Chemistry, Vol. E19a, p. 60ff. These methods are preferably used. Examples of radical sources are peroxides, hydroperoxides, and azo compounds. Some non-exclusive examples of typical radical initiators are: potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, cyclohexylsulfonylacetyl peroxide, di-tert-butyl peroxide, azodiisobutyronitrile, diisopropyl percarbonate, tert-butyl peroctoate, and benzpinacol.In a very preferred variant, 1,1'-azobis(cyclohexylnitrile) (Vazo 88®, DuPont®) or 2,2-azobis(2-methylbutanenitrile) (Vazo 67®, DuPont®) is used as the radical initiator. Photoinitiators can also be used as radical sources. A "photoinitiator" is understood to be a substance that forms radical species under the influence of light of certain wavelengths, usually at least under the action of UV radiation, optionally also UV radiation in the wavelength range of visible light (approx. 300 - 500 nm). The photoinitiator forming at least one radical is preferably selected from the group consisting of 1-hydroxycyclohexylphenyl ketone and 2,2-dimethoxy-2-acetophenone.To produce an adhesive, in particular a pressure-sensitive adhesive, in an extrusion process, the polymer system of the invention, optionally present in the closed shell, is heated in the extruder to a temperature at which the shell material melts and can thus be homogeneously incorporated into the polymer system. As has been shown, the influence of the shell material on the properties of the adhesives produced with the polymer system of the invention lies below the limit of technical relevance. The polymer system is heated to such an extent that it is deformable, in particular flowable. As has been established, the specific polymer systems of the present invention frequently have lower viscosities and thus better deformability and flowability than conventional polymers used, in particular, for the production of pressure-sensitive adhesives.The polymer system according to the invention can thus be processed into an adhesive in an extruder under the influence of heat and shear, optionally also with the incorporation of additional components, and finally molded. The temperatures typically used do not lead to the decomposition of the regulator substances incorporated into the polymer frameworks and thus also do not lead to polymer degradation. A key advantage of the invention is that prior to processing the polymer systems in the extruder, there is no need to remove solvents, which regularly leads to the degradation processes just described.

[0121] Further process steps, such as mixing with additives, filtration, or degassing, can also take place in the extruder. The resulting adhesive, in particular the pressure-sensitive adhesive, can be formed into a desired layer shape, for example, using a calender onto a carrier or a release liner. During the processing of the polymer system into an adhesive, in particular a pressure-sensitive adhesive, the polymer system can be mixed with further components. These further components can be selected from the group consisting of further polymers; bond-strengthening resins; fillers, for example electrically conductive fillers, thermally conductive fillers, and the like; flame retardants, for example ammonium polyphosphate and its derivatives; foaming agents; anti-aging agents; light stabilizers; plasticizers, and compounding particles.

[0122] The pressure-sensitive adhesive of the invention can be used as such, e.g., in the form of a laminate or a carrier-free layer of the pressure-sensitive adhesive of the invention, which is also referred to as a "transfer adhesive tape." Such a transfer adhesive tape is preferably applied only to a material that temporarily serves to protect the adhesive surface, facilitate handling, and facilitate the application of the pressure-sensitive adhesive. Such materials are also referred to as release liners or simply "liners" and are generally easily removable, particularly by means of suitable surface coatings. The second side of the transfer adhesive tape can also be provided with a liner.

[0123] The release liners are, in particular, carrier materials that are anti-adhesive (coated or treated) on one or, preferably, both sides. Various papers, optionally in combination with a stabilizing extrusion coating, can be used as carrier materials for release liners. Other suitable liner carrier materials are films, particularly polyolefin films, for example, based on ethylene, propylene, butylene, and / or hexylene. Preferred carrier materials are papers, such as glassine papers. Papers are also preferred because the concept of the origin of the components from renewable raw materials can thus be extended to the auxiliary materials of the adhesive tape.

[0124] Silicone systems are often used as anti-adhesive release coatings. Commonly used liners include siliconized papers and siliconized films.

[0125] To use the transfer tape for bonding to a substrate surface, the liner(s) are removed so that the two adhesive sides make direct contact with the substrate surfaces to be bonded. The liner therefore does not represent a productive component and is therefore not considered part of the adhesive tape, but rather merely serves as an aid for handling it.

[0126] The pressure-sensitive adhesive of the invention can furthermore be used in the construction or for the production of multilayer adhesive tapes. Corresponding multilayer adhesive tapes typically comprise at least one carrier layer and can have an outer layer of a pressure-sensitive adhesive of the invention on one or both sides. In the case of adhesive tapes with adhesive on both sides, either one of the outer layers or both outer layers can be pressure-sensitive adhesives of the invention. In the latter case, the pressure-sensitive adhesive layers can differ with regard to their chemical composition and / or their chemical and / or physical properties and / or their geometry (e.g., layer thickness), but they are particularly preferably identical with regard to their chemical composition and / or their chemical and / or physical properties.Even with multilayer adhesive tapes, one or both outer layers of the pressure-sensitive adhesive can be covered with liners. The adhesive tapes can have additional layers, such as additional carrier layers, functional layers, or the like.

[0127] Bio-based materials are preferably selected as carrier materials for the multilayer adhesive tape, for example those selected from the list consisting of paper; bio-based fabrics or nonwovens, for example made of cotton or viscose; cellophane; cellulose acetate; bio-based polyethylene (PE) and polypropylene (PP) films; films made of thermoplastic starch; bio-based polyester films, e.g., films made of polylactide (PLA; polylactic acid), polyethylene terephthalate (PET), polyethylene tetrahydrofuranoate (PEF), or polyhydroxyalkanoate (PHA). The carrier material is particularly preferably a PET film. PET films are preferred, for example, because they can be used as recycled material and thus take sustainability into account.

[0128] To anchor the pressure-sensitive adhesive to the carrier or another substrate, it can be advantageous if the adhesive and / or the substrate are treated with corona or plasma prior to coating. Furthermore, chemical anchoring, e.g., via a primer, can be advantageous for anchoring the pressure-sensitive adhesive layer to other layers, especially to a carrier layer.

[0129] Examples

[0130] Measurement and testing methods:

[0131] Method 1 - Determination of the glass transition temperature of polymers

[0132] The static glass transition temperature of the polymers was determined using dynamic scanning calorimetry (DSC). For this purpose, 5 mg of an untreated sample of the polymer in question was weighed into an aluminum crucible (volume 25 pl) and sealed with a perforated lid. A DSC 204 F1 from Netzsch was used for the measurement. The measurement was carried out under nitrogen for inerting. The sample was first cooled to -150 °C, then heated at a heating rate of 10 K / min to +150 °C and cooled again to -150 °C. The subsequent second heating curve was again run at 10 K / min and the change in heat capacity was recorded. Glass transitions are detected as steps in the thermogram (heat flow-temperature diagram, see Figure 1).

[0133] The glass transition temperature T g is obtained as follows (see Figure 1 ):

[0134] The linear sections of the measurement curve before and after the step are extended in the direction of increasing (area before the step) or decreasing (area after the step) temperatures (extension lines © and ®). In the step region, a best-fit line ® is placed parallel to the ordinate so that it intersects the two extension lines, creating two areas ® and @ (between the extension line, the best-fit line, and the measurement curve) of equal area. The intersection point of the best-fit line positioned in this way with the measurement curve yields the glass transition temperature.

[0135] Method 2 - Determination of molecular masses

[0136] The weight-average molecular weight M wThe measurements in this document refer to the conventional method of determination by gel permeation chromatography (GPC). The determination is carried out on 100 μl of a clear-filtered sample (sample concentration 3 g / l). Tetrahydrofuran is used as the eluent. The measurement is carried out at 25 °C.

[0137] The guard column is a column type PSS-SDV, 5 pm, 10 3 Ä, 8.0 mm * 50 mm (information here and below in the order: type, particle size, inner diameter * length; 1 Ä = 10 -1 ° m). For separation, a combination of columns of the type PSS SDV, 5 pm, 10 3 Ä and 10 5 Ä and 10 6 Ä with 8.0 mm * 300 mm each (columns from Agilent; detection by means of differential refractometer PSS SECcurity 2). The flow rate is 1.0 ml per minute. Calibration is performed using the commercially available ReadyCal Poly(styrene) high kit from Agilent. This is universally converted to polymethyl methacrylate (PMMA) using the Mark-Houwink parameters K and alpha, so that the data are expressed in PMMA mass equivalents.

[0138] The weight-average molecular weight M w is determined by gel permeation chromatography (GPC). THF is used as the eluent. The measurement is carried out at 23 °C. The precolumn used is PSS-SDV, 5 p, 10 3 Ä, ID 8.0 mm x 50 mm. For separation, columns PSS-SDV, 5 p, 10 3 Ä as well as 104 Ä and 106 Ä, each with an ID of 8.0 mm x 300 mm, were used. The sample concentration is 4 g / l, and the flow rate is 1.0 ml per minute. Calibration is performed using the commercially available ReadyCal Kit Poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz.

[0139] The polydispersity (PDI) is determined in a manner known to the person skilled in the art as the quotient of the weight-average and number-average molecular weight.

[0140] Method 3 - Dynamic Mechanical Analysis (DMA)

[0141] G' and G" are determined using a rheometer. The material under test is subjected to a sinusoidal oscillating shear stress in a plate-on-plate arrangement. Shear stress-controlled devices measure the deformation as a function of time and the temporal offset of this deformation relative to the application of the shear stress. This temporal offset is referred to as the phase angle δ.

[0142] The storage modulus G' is defined as follows: G' = (i / y) * cos(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G" is: G" = (i / y) * sin(ö) (T = shear stress, y = deformation, ö = phase angle = phase shift between shear stress and deformation vector). tan ö = G“ / G'.

[0143] Device: MCR 302e Rheometer (Anton Paar), plate-plate, o 12 mm

[0144] Deformation: Dynamic adaptation

[0145] Measuring frequency: 1 Hz

[0146] Measurement method: Frequency sweep

[0147] Measuring range: 10 5 — 10 2 Hz TI

[0148] Method 4 - Determination of static shear strength (shear life; SSZ)

[0149] The shear strength is a measure of the internal strength of the adhesive and was tested in the so-called static shear test as follows:

[0150] The test was carried out under standard conditions (23 °C, 50% relative humidity; SSZ (RT) 1 kg) using a weight of 1 kg. A 1.3 cm wide strip of the sample (50 μm polymer layer on 36 μm etched PET film) was bonded to a polished steel plate over a length of 2 cm by rolling over it with a 2 kg roller (twice back and forth). The platelets were equilibrated for 30 minutes under test conditions but without load. The test weight (1 kg) was then suspended so that a shear stress was created parallel to the bonding surface, and the time until the bond failed was measured. The measurement result is given in minutes. It is the median of three individual measurements. A good result is considered to be a shear time at room temperature of at least 10,000 min.

[0151] The shear stability time is determined under a test environment of 70 + / -1 °C and 10% + / - 10% relative humidity ("SSZ (70°C) 0.5 kg") in a similar manner to the above procedure, whereby the prepared plate was equilibrated under the test conditions at 70 °C for 30 minutes before suspending a 0.5 kg weight. A shear stability time at 70 °C of at least 100 minutes is considered a good result for temperature stability. A shear stability time at 70 °C of at least 300 minutes is considered a very good result for temperature stability.

[0152] Method 5 - Adhesive strength steel

[0153] The adhesive strength was determined under a test environment of 23 °C + / - 1 °C and 50% + / - 5% relative humidity. The samples were cut to a width of 20 mm and adhered to a steel plate (ASTM). The steel plate was cleaned and conditioned prior to bonding. To do this, the plate was first wiped with solvent and then left to air for 5 minutes to allow the solvent to evaporate. The side of the adhesive tape facing away from the test substrate was then covered with 25 μm thick, etched PET film, which prevented the sample from stretching during the measurement. The test sample was then rolled onto the substrate. For this purpose, the tape was rolled back and forth five times using a 4 kg roller at a winding speed of 10 m / min. One minute after rolling, the plate was pushed into a special holder.The adhesive strength was measured using a Zwick tensile testing machine; the samples were pulled at an angle of 180° at a speed of 300 mm / min. The measurement results are given in N / cm and are averaged from three individual measurements. A good result is considered to be an adhesive strength of at least 3 N / cm.

[0154] Method 6 - Determination of tack

[0155] In this test, a steel ball weighing 5.6 g rolled from a 65 mm high ramp (inclination angle 21°) onto a horizontal strip of the adhesive under test. The distance until the ball came to a stop was measured (test climate 23 °C, 50% relative humidity). A maximum distance of 300 mm is considered a good result.

[0156] Before the measurement, the spheres were cleaned with cellulose and acetone and conditioned in the test atmosphere for 30 minutes.

[0157] The adhesive was conditioned in the test climate for 1 day before the measurement.

[0158] Method 7 - Determination of Shear Adhesion Failure Temperature (SAFT)

[0159] The SAFT was determined as follows: A polished steel surface served as the defined adhesion substrate. The bondable surface element to be tested was cut to a width of 10 mm and a length of approximately 5 cm and immediately afterwards pressed three times onto the selected adhesion substrate with an area of ​​10 x 13 mm using a 2 kg steel roller at a feed rate of 10 m / min. Immediately afterwards, the previously bonded surface element was loaded with 0.5 N at an angle of 180° and subjected to a temperature ramp of 9°C / min. The temperature at which the sample covered a sliding distance of 1 mm was measured. The measured value (in °C) is the average of two individual measurements. A SAFT value of over 90 °C is considered a good result, and a SAFT value of over 120 °C is considered a very good result.

[0160] Preparation of polymer A

[0161] A 3 L vessel conventional for radical polymerizations was charged with 900 g of n-butyl acrylate (nBA), 3.933 g of 1,4-phenylenebis(methylene) didodecyl dicarbonotrithioate (BM1812; CAS 960256-58-0), and 900 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes with stirring, the reactor contents were heated to 58°C, and 0.229 g of Vazo® 67 was added. The reactor contents were then heated further to 65°C. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >95%, and the proportion of polymer A in the polymer solution was 50 wt.%.

[0162] The polymer A has a weight-average molecular weight M w of 238,000 g / mol and a polydispersity PDI of 1.46.

[0163] Preparation of polymer B

[0164] A 3 L vessel conventional for radical polymerizations was charged with 810 g of 2-ethylhexyl acrylate, 90 g of acrylic acid, 3.159 g of 1,4-phenylenebis(methylene)didodecyl dicarbonotrithioate (BM1812; CAS 960256-58-0), and 900 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes with stirring, the reactor contents were heated to 58°C, and 0.092 g of Vazo® 67 was added. The reactor contents were then heated further to 65°C. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >95%, and the proportion of polymer A in the polymer solution was 50 wt.%.

[0165] The polymer B has a weight-average molecular weight M w of 481,000 g / mol and a polydispersity PDI of 2.6.

[0166] Preparation of polymer C

[0167] A 3 L vessel conventional for radical polymerizations was charged with 900 g of n-butyl acrylate (nBA), 24.516 g of 1,4-phenylenebis(methylene)didodecyl dicarbonotrithioate (BM1812; CAS 960256-58-0), and 900 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes with stirring, the reactor contents were heated to 58°C, and 0.715 g of Vazo® 67 was added. The reactor contents were then heated further to 65°C. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >95%, and the proportion of polymer A in the polymer solution was 50 wt.%.

[0168] The polymer C has a weight average molecular weight M w of 37,200 g / mol and a polydispersity PDI of 1.2. Preparation of the block copolymer BC1

[0169] A 3 L vessel conventional for radical polymerizations was charged with 1350 g of the polymer solution of Polymer A, 225 g of isobornyl acrylate (IBOA), and 225 g of ethyl acetate (EtAc). After 45 minutes of nitrogen gas flow with stirring, the reactor contents were heated to 58°C, and 0.172 g of Vazo® 67 was added. The reactor contents were then further heated to 65°C. After 3 h, the mixture was diluted with 300 g of ethyl acetate, and after 5 h, again with 300 g of ethyl acetate. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >98%.

[0170] The block copolymer BC1 has a weight average molecular weight M w of 706,000 g / mol and a polydispersity PDI of 10.2.

[0171] Production of the block copolymer BC2

[0172] A 3 L vessel conventional for radical polymerizations was charged with 1350 g of the polymer solution of Polymer A, 225 g of dicyclopentanyl acrylate (DCPA), and 225 g of ethyl acetate (EtAc). After 45 minutes of nitrogen gas flow with stirring, the reactor contents were heated to 58°C, and 0.172 g of Vazo® 67 was added. The reactor contents were then further heated to 65°C. After 3 h, the mixture was diluted with 300 g of ethyl acetate, and after 5 h, again with 300 g of ethyl acetate. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >98%.

[0173] The block copolymer BC2 has a weight average molecular weight M w of 657,000 g / mol and a polydispersity PDI of 8.2.

[0174] Production of the block copolymer BC3

[0175] A 3 L vessel conventional for radical polymerizations was charged with 1417 g of the polymer solution of Polymer A, 192 g of norbornyl acrylate, and 192 g of ethyl acetate (EtAc). After 45 minutes of nitrogen gas flow with stirring, the reactor contents were heated to 58°C, and 0.181 g of Vazo® 67 was added. The reactor contents were then further heated to 65°C. After 3 h, the mixture was diluted with 300 g of ethyl acetate, and after 5 h, again with 300 g of ethyl acetate. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >98%.

[0176] The block copolymer BC3 has a weight average molecular weight M w of 696,000 g / mol and a polydispersity PDI of 7.0. Preparation of the block copolymer BC4

[0177] A 3 L vessel conventional for radical polymerizations was charged with 1494 g of the polymer solution of Polymer B, 153 g of dicyclopentanyl acrylate (DCPA), and 153 g of ethyl acetate (EtAc). After 45 minutes of nitrogen gas flow with stirring, the reactor contents were heated to 58°C, and 0.052 g of Vazo® 67 was added. The reactor contents were then further heated to 65°C. After 3 h, the mixture was diluted with 300 g of ethyl acetate, and after 5 h, again with 300 g of ethyl acetate. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >98%.

[0178] The block copolymer BC4 has a weight average molecular weight M w of 801,000 g / mol and a polydispersity PDI of 13.7.

[0179] Preparation of the block copolymer BC5 (Comparative Example 2)

[0180] A 3 L vessel conventional for radical polymerizations was charged with 1340 g of the polymer solution of Polymer C, 230 g of dicyclopentanyl acrylate (DCPA), and 230 g of ethyl acetate (EtAc). After 45 minutes of nitrogen gas flow with stirring, the reactor contents were heated to 58°C and 0.532 g of Vazo® 67 was added. The reactor contents were then further heated to 65°C. After 5 h, the mixture was diluted with 300 g of ethyl acetate. After a reaction time of 24 h, the reactor contents were cooled to 35°C. The conversion was >98%.

[0181] The block copolymer BC5 has a weight average molecular weight M w of 52,700 g / mol and a polydispersity PDI of 1.5.

[0182] Propene preparation for measurement and test methods

[0183] Unless otherwise stated, the prepared block copolymers were coated from solution onto a siliconized release film (50 μm polyester) using a doctor blade and then dried (coating speed 2.5 m / min, drying tunnel 15 m, temperatures Zone 1: 40 °C, Zone 2: 70 °C, Zone 3: 95 °C, Zone 4: 105 °C). The coating weight after drying was 50 g / m 2 . Table 1 : Adhesive strength and shear time of the block copolymers

[0184] The commercially available LA2330 (Kuraray Co., LTD.; Comparative Example 1) is an n-butyl acrylate-based block copolymer which has a PMMA content of approximately 20 wt.%.

[0185] Comparative Example 2 exhibits cohesive failure in the bond strength test. Due to the insufficient cohesion, Comparative Example 2 is unsuitable as a pressure-sensitive adhesive.

[0186] For samples BC2 and BC4, the SAFT value and shear strength at 70°C [SSZ (70°C) 0.5 kg] were determined. BC2 exhibits a SAFT value of 173°C and a shear strength at 70°C [SSZ (70°C) 0.5 kg] of 1801 minutes. BC4 exhibits a SAFT value of 140°C and a shear strength at 70°C [SSZ (70°C) 0.5 kg] of 350 minutes.

Claims

Patent claims 1. Pressure-sensitive adhesive based on at least one block copolymer BC, which has at least one polymer block P(A) and at least one polymer block P(B), wherein P(A) independently of one another homo- or copolymer blocks comprising a total of at least 80% by weight of monomers A selected from the group consisting of methacrylic acid esters, methacrylamides and monomers having at least one polymerizable vinyl group; P(B) independently of one another comprise homo- or copolymer blocks comprising a total of at least 80% by weight of monomers B selected from the group consisting of methacrylic acid esters, methacrylamides and monomers having at least one polymerizable vinyl group; characterized in that the monomers A comprise a total of at least 50% by weight of one or more acrylate monomers A1 selected from the general structure CH2=C(H)(COOR 1 ) include; where R 1at each occurrence is independently selected from a linear or branched alkyl radical having 4 to 17 carbon atoms; the monomers B comprise, to a total of at least 60% by weight, one or more (meth)acrylate monomers B1 selected from the general structure CH2=C(R 2 )(COOR 3 ) include; where R 2 is independently selected at each occurrence from H and CH3; and R 3 is independently selected at each occurrence from an optionally substituted, cyclic or polycyclic alkyl radical having at least 6 carbon atoms.

2. Pressure-sensitive adhesive according to claim 1, characterized in that the monomers B1 each have a glass transition temperature of the homopolymer in question which is greater than or equal to 90°C, preferably greater than or equal to 100°C, in particular greater than or equal to 105°C.

3. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers A1 each have a glass transition temperature of the homopolymer in question which is less than or equal to 0 °C, more preferably less than or equal to -10 °C, particularly preferably less than or equal to -20 °C.

4. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the block copolymer BC has a weight-average molar mass M w > 200,000 g / mol, preferably M w > 350,000 g / mol, particularly preferably M w > 500,000 g / mol.

5. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the block copolymer BC has a polydispersity of greater than 2, preferably greater than 4, particularly preferably greater than 6.

6. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the polymer blocks P(B) are present in a proportion of between 5 and 49 wt.%; preferably between 7.5 and 35 wt.%; in particular between 10 and 30 wt.%; based on the totality of the polymer blocks P(A) and P(B) of the block copolymer BC.

7. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the block copolymer BC can be described by one or more of the following general formulas: P(A)-P(B)-P(A) (la) P(B)-P(A)-P(B) (lb) P(B)-P(A)-P(B)-P(A)-P(B) (Ha) P(A)-P(B)-P(A)-P(B)-P(A) (Hb) [P(A)-P(B)] n X (Hla) [P(B)-P(A)] n X (Hlb) [P(B)-P(A)-P(B)] n X (IVa) [P(A)-P(B)-P(A)] n X (IVb) [P(A)-P(B)] n X[P(B)] m (Va) [P(B)-P(A)] n X[P(A)] m(Vb) where n = 2 to 12, m = 1 to 12 and X is a di- or multifunctional represents the branching area.

8. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the polymer blocks P(A) and P(B) are not homogeneously miscible with one another.

9. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers A1 are selected from the group consisting of n-butyl acrylate, iso-butyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 2-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, iso-octyl acrylate, n-nonyl acrylate, iso- Nonyl acrylate, 2-propylheptyl acrylate, n-decyl acrylate, isodecyl acrylate, lauryl acrylate, tetradecyl acrylate, heptadecyl acrylate.

10. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers B1 are selected from the general structure CH2=C(R 2 )(COOR 3 ); where R 2is equal to H; and R 3 at each occurrence is independently selected from cyclic or polycyclic alkyl radicals having 6 to 14 carbon atoms, preferably 7 to 12 carbon atoms.

11. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers B1 are not isobornyl acrylate.

12. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers B1 are selected from the group consisting of norbornyl acrylate, tricyclodecanol acrylate and dicyclopentanyl acrylate, preferably the monomers B1 are dicyclopentanyl acrylate.

13. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers A and monomers B comprise a total of not more than 15% by weight, preferably a total of not more than 10% by weight, particularly preferably a total of not more than 5% by weight of methyl methacrylate.

14. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomers A and / or monomers B are substantially free of methyl methacrylate; more preferably free of methacrylic acid esters and methacrylamides; in particular free of any methacrylic compounds.

15. Pressure-sensitive adhesive according to one of the preceding claims, comprising at least one block polymer BC to at least 50% by weight, preferably to at least 60% by weight, particularly preferably to 70% by weight, based on the total weight of the pressure-sensitive adhesive.

16. Adhesive tape comprising a pressure-sensitive adhesive according to any one of claims 1 to 15.

17. A process for producing a pressure-sensitive adhesive according to any one of claims 1 to 15, characterized in that at least one polymerization step takes place in a closed shell and / or is a RAFT polymerization.

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