Curable adhesive substance with improved punchability

Abstract

The invention relates to a curable adhesive substance comprising the following, in relation to the mass of the curable adhesive substance: a) one or more (meth)acrylate block copolymers X with an A-B-A structure in a combined mass fraction of 20% or more, wherein the A blocks independently represent a poly(meth)acrylate with a glass transition temperature Tg of 50 °C or more, which can be produced by polymerising an A monomer composition formed of A monomers, wherein the B block represents a poly(meth)acrylate with a glass transition temperature Tg of less than 50 °C, which can be produced by polymerising a B monomer composition formed of B monomers; and b) one or more polymerisable compounds Y in a combined mass fraction of 20% or more, and wherein, for the polar fractions (weighted by substance amount) of the Hansen solubility parameters <δp>: i) of the monomer units in the A blocks <δp>(A) derived from A monomers, ii) of the monomer units in the B block <δp>(B) derived from B monomers, and iii) of the polymerisable compounds Y <δp>(Y), the following is true: - |<δp>(A) - <δp>(Y)| > 3.5 MPa0.5, and - |<δp>(B) - <δp>(Y)| < 3.5 MPa0.5.

Description

[0001] Curable adhesive with improved die-cutting properties

[0002] The invention relates to a curable adhesive and a reactive adhesive tape comprising a corresponding curable adhesive. Also disclosed are the use of corresponding curable adhesives and reactive adhesive tapes for bonding two or more components, as well as a process for producing corresponding curable adhesives.

[0003] Joining separate elements is one of the central processes in manufacturing technology. Alongside other methods such as welding and soldering, bonding, i.e. joining using an adhesive, is becoming increasingly important. Adhesive tapes are an alternative to the use of formless adhesives, which are applied from a tube, for example. Pressure-sensitive adhesive tapes are particularly well-known in everyday life. These tapes use a pressure-sensitive adhesive mass that provides the adhesive effect and is permanently tacky and adhesive under normal ambient conditions. Such pressure-sensitive adhesive tapes can be applied to a substrate using pressure and remain there, but can later be removed more or less residue-free.

[0004] However, another type of adhesive tape is also of great importance, particularly for use in industrial manufacturing technology. These adhesive tapes, which are sometimes also referred to as reactive adhesive tapes, use a curable adhesive. In the state intended for application, such curable adhesives have not yet reached their maximum degree of crosslinking and can be cured by external influences by initiating polymerization in the curable adhesive, thereby increasing the degree of crosslinking. This changes the mechanical properties of the now cured adhesive, with particular increases in viscosity, surface hardness, and strength. Curable adhesives are known in the art and can have very different chemical compositions.These curable adhesives have in common that the crosslinking reaction can be triggered by external factors, for example, by the supply of energy, in particular by temperature, plasma, or radiation curing, and / or contact with a polymerization-promoting substance, as is the case, for example, with moisture-curing adhesives. Corresponding adhesives are disclosed, for example, in DE 102015222028 A1, EP 3091059 A1, EP 3126402 B1, EP 2768919 B1, DE 102018203894 A1, and WO 2017174303 A1, US Pat. No. 4,661,542 A.

[0005] The curability of such curable adhesives is typically achieved through the use of polymerizable compounds, particularly crosslinkable monomers or oligomers. These low-molecular-weight polymerizable compounds, which usually need to be used in a significant mass fraction to ensure sufficient curability, are sometimes referred to by those skilled in the art as reactive resins.

[0006] The low molecular weight reactive resins typically used are usually liquids with a low viscosity. In combination with the high mass fraction in curable adhesives, this means that the corresponding curable adhesives themselves usually have a low viscosity. As a result, the processing properties of many state-of-the-art curable adhesives are considered inadequate, and a comparatively high level of effort is required in the typical processing methods used in the adhesives industry to process curable adhesives effectively. In addition to the dimensional stability of the pressure-sensitive adhesives when winding adhesive tapes, their die-cutting properties, i.e. their suitability for separating adhesive elements using a die-cutting process, are regularly rated as inadequate.

[0007] To ensure the best possible processability for the end user, it is generally desirable for curable adhesives to possess at least weak pressure-sensitive adhesive properties. In particular, it is desirable that reactive adhesive tapes can be removed, if necessary, before curing without leaving any residue, for example, if an adhesive tape is incorrectly applied. However, the properties of curable adhesives, which are determined by the high mass fraction of reactive resin, often result in insufficient cohesion in the curable adhesive. Instead of the desired adhesion failure on the substrate, cohesive failure can often occur, leaving residues of the adhesive on the substrate.

[0008] In light of the above, there is continued interest in the field of adhesive technology in improving the processing properties of curable adhesives, with particular emphasis on improving die-cutting properties and increasing the cohesion of the material.

[0009] However, the measures known from the prior art for increasing the cohesion and / or for reducing the viscosity of the curable adhesives often impair the subsequent handling properties of the reactive adhesive tapes, since the flow behavior desired in the application, i.e. the adaptation of the curable adhesive of the reactive adhesive tape to the structure of the substrate, in particular in the case of rough substrate surfaces, is adversely affected, so that after curing, an adhesive strength which does not meet the requirements may be achieved due to insufficient contact with the substrate.Against this background, in the field of curable adhesives, there is regularly a conflict of objectives between sufficient cohesion in the curable adhesive and its processing properties in the production of adhesive tapes on the one hand, and the handling and adhesive properties of the resulting reactive adhesive tapes on the other hand.

[0010] The primary object of the present invention was to eliminate or at least reduce the above-described disadvantages of the prior art.

[0011] In particular, it was the object of the present invention to provide a curable adhesive in which the above-described conflict of objectives between high cohesion and good processability of the adhesive, in particular good die-cutting, on the one hand, and the handling properties and the achievable adhesive strength of the reactive adhesive tape on the other hand, is resolved in the best possible way.

[0012] In this respect, it was the object of the present invention to provide a curable adhesive composition which, despite large mass fractions of reactive resin, shows sufficient cohesion to achieve an essentially adhesive failure upon detachment from the substrate in later use.

[0013] It was an object of the present invention that the curable adhesive compositions to be specified should have advantageous flow behavior and should achieve excellent adhesive strength even on substrates with rough surfaces after curing.

[0014] It was a further object of the present invention that the curable adhesives to be specified should have excellent shock resistance in the cured state.

[0015] It was a supplementary object of the present invention that the pressure-sensitive adhesives to be specified should ideally be producible as far as possible using starting materials and processes which are already used in the field of adhesive technology in order to enable time- and cost-efficient production.

[0016] It was a supplementary object of the present invention to provide an advantageous reactive adhesive tape or pressure-sensitive adhesive tape.

[0017] In addition, it was a secondary object of the present invention to provide a use of the curable adhesives or reactive adhesive tapes to be specified for bonding two or more components and a process for producing corresponding curable adhesives.

[0018] The inventors of the present invention have now found that the objects described above can surprisingly be achieved if, in curable adhesive compositions having a comparatively large mass fraction of reactive resins, significant amounts of a (meth)acrylate block copolymer of the general formula ABA are used, the A and B blocks of which are specifically selected and precisely matched to the reactive resin with regard to their polarity, as defined in the claims.

[0019] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0020] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus very particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred adhesive tapes, uses, and methods emerge from the features of preferred curable adhesive compositions.

[0021] To the extent that both specific amounts or proportions of an element and preferred embodiments of the element are disclosed below for an element, for example for the (meth)acrylate block copolymers or a specific monomer, the specific amounts or proportions of the preferably configured elements are also disclosed in particular. 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 also that preferably configured elements can in turn be present in the specific amounts or proportions within the specific total amounts or total proportions.

[0022] The invention relates to a curable adhesive composition comprising, based on the

[0023] Mass of the curable adhesive composition: a) one or more (meth)acrylate block copolymers X of the structure ABA in a combined mass fraction of 20% or more, wherein the A blocks independently of one another represent a poly(meth)acrylate having a glass transition temperature Tg of 50°C or more, which can be prepared by polymerizing an A monomer composition from A monomers, wherein the B block represents a poly(meth)acrylate having a glass transition temperature Tg of less than 50°C, which can be prepared by polymerizing a B monomer composition from B monomers, and b) one or more polymerizable compounds Y in a combined mass fraction of 20% or more, and wherein for the substance-weighted polar fractions the Hansen solubility parameter <ö p >: i) the monomer units derived from A monomers in the A blocks <ö P >(A), ii) the monomer units derived from B monomers in the B block <ö p>(B), and iii) the polymerizable compounds Y <ö p >(Y), it holds that:

[0024] |<ö p >(A) - <ö p >(Y)| > 3.5 MPa 05 , and

[0025] |<ö p >(B) - <ö p >(Y)| < 3.5 MPa 05 .

[0026] The purely identifying additions X and Y serve to more clearly distinguish them from the A and B blocks and to facilitate reference. These components, defined above, are used as "one or more" in accordance with the expert's understanding. The term "one or more" refers, in accordance with industry practice, to the chemical nature of the corresponding compounds and not to their quantity. For example, the curable adhesive composition may comprise exclusively epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate as polymerizable compounds Y, which would mean that the monomer composition comprises a plurality of the corresponding molecules.

[0027] Typically, the mass fractions are given as combined mass fractions of the one or more components, which expresses that the mass fraction of the correspondingly formed components taken together meets the corresponding criteria, wherein for the (meth)acrylate block copolymers X and the polymerizable compounds Y, the mass of the curable adhesive is the reference system.

[0028] The curable adhesive composition according to the invention is curable. Due to its ability to cure, the curable adhesive composition can function as a structural adhesive after curing. According to DIN EN 923: 2006-01, structural adhesives are adhesives that form adhesive bonds that can maintain a specified strength in a structure for a specified, extended period of time (according to the ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). These are therefore adhesives for bonds subject to high chemical and physical stresses, which, when cured, contribute to the strengthening of the adhesive tapes.

[0029] Block copolymers in general, and (meth)acrylate block copolymers in particular, are generally known from the prior art, especially block copolymers with the ABA structure. The preparation of (meth)acrylate block copolymers, for example with the ABA structure, is described in the prior art, and the block copolymerization processes known from the prior art can also be used for the (meth)acrylate block copolymers used here. An exemplary overview of block copolymers which are used for different purposes, including in various adhesives, can be found, for example, in the documents US 2011003947 A1 , US 20080200589 A1 , US 2007078236 A1 , US 2007078236 A1 , US 2012196952 A1 , US 2016032157 A1 , US 2008146747 A1 and US 2016230054 A1.In the (meth)acrylate block copolymers X of the ABA structure to be used according to the invention, the A blocks have a higher glass transition temperature than the B blocks. In keeping with the terminology also sometimes used for other block copolymers, the A blocks are sometimes referred to as so-called hard blocks, whereas the B block is also referred to as a soft block. In this respect, however, it should be noted that, in the inventors' opinion, higher glass transition temperatures can in principle also be provided in the B block for the (meth)acrylate block copolymers identified by the inventors than for some soft blocks known from the prior art. In accordance with expert understanding, the glass transition temperature of the A blocks or the B block is not determined on the (meth)acrylate block copolymer X, but on the isolated (co)polymers of the respective blocks.

[0030] In the context of the present invention, the glass transition temperature of polymers or of polymer blocks in block copolymers is determined by means of differential scanning calorimetry (DSC), as described in DIN EN ISO 11357. For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 pL) and sealed with a perforated lid. A DSC 204 F1 from Netzsch is used for the measurement. The measurement is carried out under nitrogen for inerting. The sample is 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 is again run at 10 K / min, and the change in heat capacity is recorded. Glass transitions are detected as steps in the thermogram. The determination of the glass transition temperature from the DSC measurements is easily possible for the person skilled in the art and is described in more detail in EP 2832811 A1, for example.

[0031] The two A blocks of the (meth)acrylate block copolymers X are characterized by a common criterion for the glass transition temperature and by their ability to be produced from the same A monomers. Those skilled in the art will understand that the A blocks are very similar in terms of their production, but do not have to be exactly identical due to the nature of the polymerization processes used for production, particularly when two or more different A monomers are used. This applies analogously to the A and B blocks and also to the (meth)acrylate block copolymers themselves, since those skilled in the art in the field of polymeric materials would refer to block copolymers that differ from one another with respect to the A and B blocks only within the scope of production-related variations as a common material, i.e., as a (meth)acrylate block copolymer.

[0032] In accordance with the expert understanding and the usual practice in the field of technology, it is expedient to define polymeric and oligomeric compounds such as the A-blocks and the B-block via the manufacturing process or the starting materials used for the manufacturing, since it is impossible to meaningfully define the corresponding materials otherwise.

[0033] In the curable adhesive compositions according to the invention, (meth)acrylate block copolymers X consisting of poly(meth)acrylate blocks are used. These (meth)acrylate block copolymers X thus consist at least partially of structural units derived from (meth)acrylate monomers, where the term (meth)acrylate encompasses both acrylates and methacrylates in accordance with the understanding of those skilled in the art. It is preferred in this respect if the (meth)acrylate block copolymers and the corresponding blocks were produced predominantly or even substantially entirely from (meth)acrylate monomers.

[0034] In the context of the present invention, the term "poly(meth)acrylates" encompasses, in accordance with the expert understanding, polyacrylates and polymethacrylates as well as copolymers of these polymers. Poly(meth)acrylates may contain minor amounts of monomer units that are not derived from (meth)acrylates. In the context of the present invention, a "poly(meth)acrylate" is understood to mean a (co)polymer whose monomer base consists of a mass fraction of 70% or more, preferably 90% or more, particularly preferably 98% or more, of monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters, based on the mass of the monomer base. The mass fraction of acrylic ester and / or methacrylic ester is preferably 50% or more, particularly preferably 70% or more.Poly(meth)acrylates are generally accessible by radical polymerization of acrylic and / or methacrylic-based monomers and, if appropriate, other copolymerizable monomers.

[0035] Such poly(meth)acrylates can be produced from the respective monomers using conventional processes, in particular by conventional radical polymerizations or controlled radical polymerizations, for example, anionic polymerization, RAFT, NMRP, or ATRP polymerization. The polymers or oligomers can be produced by copolymerization of the monomer components using conventional polymerization initiators and, if appropriate, regulators. Polymerization can be carried out at conventional temperatures, for example, in bulk, in emulsion, e.g., in water or liquid hydrocarbons, or in solution.The poly(meth)acrylates are preferably prepared by polymerization in solvents, particularly preferably in solvents having a boiling point in the range from 50 to 150 °C, particularly preferably in the range from 60 to 120 °C, using the usual amounts of polymerization initiators, the polymerization initiators generally being added to the monomer composition in a proportion of about 0.01 to 5%, in particular from 0.1 to 2%, based on the mass of the monomer composition.

[0036] Suitable polymerization initiators include, for example, radical sources such as peroxides, hydroperoxides, and azo compounds, e.g., dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, or benzpinacol. 2,2'-azobis(2-methylbutyronitrile) or 2,2'-azobis(2-methylpropionitrile) is particularly preferred as the radical polymerization initiator. Suitable solvents include, in particular, alcohols such as methanol, ethanol, n- and iso-propanol, n- and iso-butanol, preferably isopropanol and / or isobutanol, as well as hydrocarbons such as toluene and, in particular, gasolines with a boiling point in the range of 60 to 120 °C. In particular, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate, as well as mixtures of these solvents can be used.

[0037] The curable adhesive according to the invention comprises polymerizable compounds Y. The polymerizable compounds Y in the curable adhesive together form the part of the curable adhesive frequently referred to by those skilled in the art as the reactive resin. The term "polymerizable" refers here, in accordance with the expert's understanding, to the ability of the polymerizable compounds, optionally after suitable activation, to enter into a polymerization reaction. In many cases, polymerizability is made possible, for example, by ethylenically unsaturated groups. However, polymerizability can also arise from the presence of two or more polymerizable compounds Y that are jointly polymerizable, for example, by a polyaddition or a polycondensation. An example of this would be the combination of epoxides with dicyandiamide and / or imidazoles.

[0038] In the curable adhesive composition according to the invention, the polarity of the A and B blocks is specifically matched to the polarity of the polymerizable compounds Y. This is achieved by adjusting the so-called polar portion of the Hansen solubility parameters, the background of which is explained in more detail below. For a fundamental understanding of the invention, it is initially sufficiently clear at this point that the A blocks must differ significantly in terms of their polarity from the polarity of the polymerizable compound Y, which is expressed here by the absolute value of the difference between the corresponding polar portions of the Hansen solubility parameters of monomer units derived from A monomers in the A blocks and those of the polymerizable compounds Y being greater than 3.5 MPa. 05In this case, the definition based on the amount of the difference is useful, since both a positive and a negative deviation are possible, provided the amount is sufficiently large.

[0039] In clear contrast to this, the polarity of the B blocks should be as close as possible to the polarity of the reactive resin, i.e. the polymerizable compounds Y, which is defined here by the difference between the polar portion of the Hansen solubility parameters of the monomer units derived from B monomers in the B block and the corresponding value of the polymerizable compounds Y being less than 3.5 MPa 05 should be.

[0040] The inventors have recognized that this specific matching of the (meth)acrylate block copolymers to the reactive resin used leads to an optimal solution to the conflicting objectives defined above, resulting in a curable adhesive with excellent processing properties and sufficient cohesion, which nevertheless exhibits good flow behavior even on rough substrates and exhibits advantageous adhesive strength after curing. The curable adhesives exhibit excellent shock resistance.

[0041] Without wishing to be bound by this theory, the inventors assume that the adjustment of the polarities described above results in the B block of the (meth)acrylate block copolymers being particularly soluble in the reactive resins used, whereas the A blocks have a particularly low solubility in the reactive resin, which is in particular significantly below the solubility of A blocks known from the prior art and which, in the opinion of the inventors, is responsible for the advantageous cohesion of the curable adhesive, whereas the readily soluble B block ensures the absorption of the (meth)acrylate block copolymers in the reactive resins and thus sufficient compatibility.

[0042] The following section explains the concept of Hansen solubility parameters, their background and their calculation, as well as provides exemplary values ​​for monomers that are regularly used in the field of adhesive technology.

[0043] A well-known description of solubility parameters in the literature is the one-dimensional Hildebrand parameter (δ). However, these one-dimensional δ values ​​are subject to errors, which are often large for polar compounds such as (meth)acrylates or those that can form hydrogen bonds, such as acrylic acid. Since the model of the one-dimensional Hildebrand solubility parameters thus has only limited application, it was further developed by Hansen (see Hansen Solubility Parameters: A User's Handbook, Second Edition; Charles M. Hansen; 2007 CRC Press; ISBN 9780849372483).

[0044] These Hansen solubility parameters, which are widely used today, are three-dimensional solubility parameters that are frequently used, particularly in the field of adhesive formulation, as disclosed, for example, in WO 2019 / 106194 A1 or WO 2019 / 229150 A1. They consist of a disperse component (öd), a component consisting of polar interactions (ö p ) and a portion for hydrogen bonds ( H). The Hansen solubility parameters are related to the Hildebrand parameter ö as follows: ö 2 = ö d 2 + ö p 2 + Students' Union 2 .

[0045] The values ​​for öd, ö pThe solubility parameters H and ÖH cannot be determined directly experimentally for poly(meth)acrylates, but can be calculated using incremental systems. A common method, also used in the present invention, is that of Stefanis / Panayiotou ("Prediction of Hansen Solubility Parameters with a New Group-Contribution Method"; Int. J. Thermophys. (2008) 29:568-585; Emmanuel Stefanis, Costas Panayiotou).

[0046] According to the group contribution method according to Stefanis / Panayiotou, the solubility parameters of the monomer units in the polymers attributable to the individual monomers, i.e. those of the repeating unit in a polymer chain (i.e., possibly without the polymerizable double bond of the monomers, but instead taking into account a covalent s-bond as present in the polymer chain), are calculated according to the procedure in the cited document to determine the Hansen solubility parameters for polymers. For each group in the building block, a specific value is required for the disperse fraction (öd), the fraction of polar interactions (ö p ) and the hydrogen bond formation fraction (Ö H ), see “Prediction of Hansen Solubility Parameters with a New Group-Contribution Method”; Int. J. Thermophys. (2008), Tables 3 to 6, pages 578 to 582. Polyacrylic acid, for example, contains the repeating unit:

[0047] -[-CH2-CHC(O)OH-] n -,

[0048] According to the increment system of Stefanis / Panayiotou, the Hansen solubility parameters (one CH2 group, one CH group and one COOH group) for the corresponding building block are: d = 17.7, ö p = 8.6 and Ö H = 11 ,1.

[0049] Polybutylacrylate, for example, contains the repeating unit:

[0050] -[-CH2-CHC(O)O(CH2)3CH3-]n-,

[0051] With four CH2 groups, one CH group, one COO group and one CH3 group, the Hansen solubility parameters for the corresponding building block are ö d = 17.1 , ö p = 8.6 and Ö H = 6.5.

[0052] In the group contribution method according to Stefanis and Panayiotou, more complex organic molecules are described using so-called first- and second-order groups. The first-order groups (n) represent the basic molecular structure. The second-order groups (m) account for the conjugation of the first-order groups and increase the accuracy of the method.

[0053] According to the inventors’ knowledge, only the polar components are relevant for the present invention. p These can be calculated using the following formula:

[0054] Tables 1 and 2 show exemplary calculations for two example reactive resins (epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate and 2-hydroxy-3-phenoxypropyl acrylate). Table 1 - Calculation of the polar part of the Hansen solubility parameters ö p for epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate.

[0055] / N Group C

[0056] 1st order

[0057] 1 1 COO 3.4637

[0058] 2 7 -CH2 -0.3045

[0059] 3 6 -CH< 0.6491

[0060] 4 2 0 3.3432 y M Group D

[0061] 2nd order

[0062] 1 2 C6 ring -3.6437

[0063] Total: 11.9806 MPa 05

[0064] Table 2 - Calculation of the polar part of the Hansen solubility parameters ö p for 2-hydroxy-3-phenoxypropyl acrylate.

[0065] / N Group C

[0066] 1st order

[0067] 1 5 ACH -0.5303

[0068] 2 1 AC 0.6187

[0069] 3 1 CH2O 0.8826

[0070] 4 1 -CH< 0.6491

[0071] 5 1 OH 1 ,1404

[0072] 6 1 -CH2 -0.3045

[0073] 7 1 COO 3.4637

[0074] 8 1 CH2=CH- -2.0035 j M Group D

[0075] 2nd order

[0076] 1 1 AC-OC 0.8153

[0077] Total: 9.9651 MPa 05

[0078] The person skilled in the art understands that the calculation of the Hansen solubility parameters in the context of the present invention for the polymerizable compounds Y can be carried out directly on the monomers, but that the polarity of the A and B blocks is determined via the evaluation of the monomer units, ie the repeating units in the polymer chain, so that compared to the

[0079] monomers used in the production, ie the A monomers and the B monomers, a CH2=CH- group is considered as a -CH2-CH- group. According to the specifications of the calculation method, when using mixtures of polymerizable compounds Y or mixtures of A monomers or B monomers in the production of copolymers, an average value of the polar portion of the Hansen solubility parameters is calculated, wherein the contributions of the individual monomers are weighted by their molar fraction, so that within the scope of the present invention the molar fraction-weighted polar portions of the Hansen solubility parameters <ö p > calculated according to the group contribution method of Stefanis and Panayiotou, as explained above.

[0080] Table 3 shows the polar components of the Hansen solubility parameters as examples for selected monomers that are highly relevant as basic building blocks for polymers in the field of curable adhesives.

[0081] Table 3 - Polar parts of the Hansen solubility parameters ö p for exemplary monomers (rounded). One advantage of the curable adhesives according to the invention is that they are very flexible with regard to the curing mechanism used. The skilled person selects the curing mechanism required essentially in light of the application requirements and adapts the curable adhesive according to the invention to this extent. This is done in accordance with standard industry practice by selecting the appropriate reactive resin and, if appropriate, the necessary initiators and / or co-initiators. For most applications, it will be expedient in practice if the curable adhesive according to the invention additionally comprises one or more initiators.With regard to subsequent handling properties, the inventors believe it is particularly advantageous to use radiation-curing and / or thermally crosslinking systems, with radiation activation in particular providing significant handling advantages. A curable adhesive according to the invention is preferred, wherein the curable adhesive is a radiation-curing and / or thermally curing adhesive, and / or wherein the curable adhesive is curable by polymerization of the polymerizable compounds Y, preferably by radiation activation and / or thermal activation.Thus, preference is given to a curable adhesive according to the invention, wherein the curable adhesive comprises one or more initiators, preferably in a combined mass fraction in the range from 0.05 to 4%, preferably in the range from 0.1 to 3%, based on the mass of the adhesive, and / or wherein the one or more initiators are preferably selected from the group consisting of radiation-activated initiators and thermally activated initiators and / or are selected from the group consisting of initiators for radical polymerization and initiators for cationic polymerization, for example triarylsulfonium hexafluoroantimonate or diisopropylbenzene hydroperoxide in combination with Ru(bipy)a Cl2 hexahydrate.

[0082] As explained above, the initiators used are matched by the person skilled in the art to the polymerizable compounds Y used in each case.

[0083] If the polymerizable compound Y is a radically polymerizable compound (e.g. a (meth)acrylate), light curing or thermal curing can be used, for example. Type I or Type II photoinitiators, as described, for example, in "Industrial Photoinitiators: A technical guide" 2010 by WA Green, are suitable for light curing. Typically, the mass fraction of these photoinitiators in the curable adhesive is not more than 3% but at least 0.1%, and is preferably in the range from 0.5 to 2%. Photoredox catalysts can also be used, particularly in the case of non-transparent substrates, as disclosed, for example, in DE 102019209513 A1.For thermal curing, for example, the polymerization initiators described above are suitable, the mass fraction of these polymerization initiators being not more than 3% but at least 0.1% and preferably in the range from 0.5 to 2%.

[0084] Even if the polymerizable compound Y is a cyclic ether compound (e.g. an epoxy), light curing or thermal curing can be used, for example. So-called hardeners and accelerators are usually used for thermal curing. The hardener causes chemical crosslinking, whereby the accelerators, in the presence of a hardener, increase the reaction rate of the curing reaction and / or the rate of activation of the curing of the epoxy resins. The lists of substances that can be used as hardeners and accelerators overlap, although the individual representatives can also perform both functions simultaneously, so that the transition between hardener and accelerator is generally fluid, without the selection of a suitable system combining hardener and accelerator presenting the expert with any major challenges.Compounds selected from the group consisting of dicyandiamides, imidazoles, anhydrides, epoxy-amine adducts, hydrazides, and reaction products of diacids and multifunctional amines can be used as hardeners and / or accelerators. Examples of suitable reaction products of diacids and multifunctional amines include reaction products of phthalic acid and diethylenetriamine. Stoichiometric hardeners such as dicyandiamide are preferably used relative to the amount of epoxy in the adhesive. Non-stoichiometric hardeners such as imidazoles and epoxy-amine adducts are typically used in proportions of up to 20% relative to the amount of epoxy.

[0085] Sulfonium, iodonium, and metallocene-based systems are particularly suitable as initiators for cationic UV-induced curing of cyclic ether compounds. For examples of sulfonium-based cations, see US Pat. No. 6,908,722 B1. Examples of anions that serve as counterions for the above-mentioned cations include tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate, hexachloroantimonate, tetrakispentafluorophenylborate, tetrakis(pentafluoromethylphenyl)borate, bi(trifluoromethylsulfonyl)amide, and tris(trifluoromethylsulfonyl)methide. Furthermore, especially for iodonium-based initiators, chloride, bromide or iodide are also conceivable as anions, although initiators that are essentially free of chlorine and bromine are preferred.A powerful example of such a system is triphenylsulfonium hexafluoroantimonate. Other initiators are disclosed, for example, in US 3,729,313 A, US 3,741,769 A, US 4,250,053 A, US 4,394,403 A, US 4,231,951 A, US 4,256,828 A, US 4,058,401 A, US 4,138,255 A, and US 2010 / 063221 A1. Photoinitiators are typically used individually or in combinations of two or more photoinitiators. When using photoinitiators, combinations with so-called sensitizers are very helpful for adapting the activation wavelength of the photoinitiation system to the selected emission spectrum. For this purpose, reference is made to literature familiar to those skilled in the art, such as "Industrial Photoinitiators: A Technical Guide" 2010 by AW Green. Typically, in these cases, the mass fraction of photoinitiators in the curable adhesive is not more than 4% but at least 0.1%, and is preferably in the range of 0.5 to 2%.The mass fraction of sensitizers is usually not more than 3% and is preferably in the range of 0.5 to 2%.

[0086] For subsequent use in the final application, it is advantageous for handling properties if the curable adhesive exhibits intrinsic pressure-sensitive adhesive strength and can thus be classified as a pressure-sensitive adhesive. Due to the advantageously high cohesion in curable adhesives of the invention, it is particularly easy to adjust these properties in curable adhesives of the invention. The pressure-sensitive adhesive strength allows reliable and secure application of the reactive adhesive tapes to the substrate before the curable adhesives cure. Therefore, a curable adhesive of the invention is preferred, wherein the curable adhesive is a pressure-sensitive adhesive.

[0087] A pressure-sensitive adhesive (PSA) is, in accordance with expert understanding, 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 pressure-sensitive adhesive tapes can usually be removed from the substrate after use without leaving any residue and are generally permanently tacky even at room temperature, meaning they possess a certain viscosity and initial tack, allowing them to wet the surface of a substrate even under light pressure. The tackiness of a pressure-sensitive adhesive tape results from the fact that a pressure-sensitive adhesive is used as the adhesive.Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be viewed as an extremely viscous liquid with an elastic component, which consequently exhibits characteristic viscoelastic properties that lead to the permanent inherent tack and pressure-sensitive adhesive capacity described above. It is assumed that with corresponding pressure-sensitive adhesives, mechanical deformation leads to both viscous flow processes and the build-up of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are necessary in particular to achieve cohesion. The relationships between rheology and pressure-sensitive tack are 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 characterise the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G") are usually used, which can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189323. In the context of the present invention, an adhesive is preferably understood to be pressure-sensitive and thus 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.

[0088] In principle, it is conceivable that low-molecular-weight oligomers can also be used as polymerizable compounds Y, which are then crosslinked with one another during the curing of the curable adhesives. However, in view of the reactive resins used in practice, in the vast majority of cases it is particularly preferred for the polymerizable compounds Y to be polymerizable Y monomers, in particular because the processing properties of such Y monomers can in many cases be adjusted more favorably and precisely than with oligomers. Therefore, a curable adhesive according to the invention is preferred, wherein the polymerizable compounds Y are selected from the group consisting of polymerizable Y monomers.

[0089] According to the inventors' assessment, particularly high-performance curable adhesives can be obtained using cyclic ethers, especially epoxy monomers, and acrylate monomers as reactive resins. In particular, particularly favorable polar fractions of the Hansen solubility parameters, which are neither too high nor too low, are regularly obtained for corresponding monomers, so that sufficient flexibility remains when adjusting the A and B blocks. Preferred is a curable adhesive according to the invention, wherein the polymerizable compounds Y are selected from the group consisting of oxetane compounds, especially oxetane monomers, epoxy compounds, especially epoxy monomers, and (meth)acrylate monomers, preferably epoxy monomers and acrylate monomers.

[0090] In the inventors' opinion, because of the mostly quite different polarities of typical oxetane, epoxy and acrylate monomers, it is sensible to use only one class of these polymerizable compounds Y as the reactive resin, preferably completely, in order to adjust the required polarity differences, whereby the inventors have succeeded in identifying particularly high-performance polymerizable compounds in this respect.

[0091] In principle, suitable reactive monomers include, for example, acrylic acid esters (such as 2-ethylhexyl acrylate), methacrylic acid esters, vinyl compounds and oligomers or polymeric compounds with carbon-carbon double bonds, as well as higher functional (meth)acrylates. Preferred monomers with regard to high bond strength are (meth)acrylic acid esters in which the alcohol part of the ester contains aromatic structural elements, heteroatoms or functional groups. Preference is given to urethane groups, urea groups, oxygen or nitrogen heterocycles, ether groups, ester groups, acid functions and / or hydroxyl functions. With regard to good resistance to humid heat, (meth)acrylic acid esters in which the alcohol part of the ester is a fatty alcohol are also preferred. Furthermore, crosslinking monomers are preferred with regard to a high crosslinking density. Examples of preferred monomers are 2-phenoxyethyl acrylate (CAS No.: 48145-04-6), 2-Phenoxyethyl- methacrylat (CAS-Nr.: 10595-06-9), 2-Hydroxy-3-phenoxy-propylacrylat (CAS- Nr.: 16969-10-1), 2-Hydroxy-3-phenoxy-propylmethacrylat (CAS-Nr.: 16926-87- 7), 2-[2-(Methacryloyloxy)ethoxycarbonyl]benzoesäure (CAS-Nr.: 27697-00-3), 2- [[(Phenylamino)carbonyl]oxy]ethyl methacrylat (CAS-Nr.: 51727-47-0), 2-Tert- butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenylprop-2- enoat (CAS-Nr.: 61167-58-6), (5-Ethyl-1 ,3-dioxan-5-yl)methylacrylat (CAS-Nr. 66492-51-1), (2-Oxo-l ,3-dioxolan-4-yl)methyl methacrylat (CAS-Nr.: 13818-44- 5), Di(ethylenglycol)-2-ethylhexylether acrylat (CAS-Nr.: 117646-83-0), (2,2- Dimethyl-1 ,3-dioxolan-4-yl)methylprop-2-enoat (CAS-Nr.: 13188-82-4),.

[0092] Succinic acid mono-[2-(acryloyloxy)-ethyl ester] (CAS no.: 50940-49-3), succinic acid mono-[2-(methacryloyloxy)ethyl ester] (CAS no.: 20882-04-6), (2,2-pentamethylene-1,3-oxazolidyl-3)ethyl methacrylate (CAS no.: 4203-89-8, 2-Hydroxy-3-(prop-2-enoyloxy)propyl-2-methyl-2-propylhexanoate (CAS No.: 444649-70-1), 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate (CAS No.: 63225-53-6), Stearyl acrylate (CAS No.: 4813-57-4), stearyl methacrylate (CAS No.: 32360-05-7), as well as the crosslinking reactive monomers diurethane dimethacrylate (mixture of isomers) (CAS No.: 72869-86-4), bisphenol A glycerolate dimethacrylate (BIS-GMA, CAS No.: 1565-94-2, e.g. Ebecryl 600), bisphenol A dimethacrylate (BIS-DMA, CAS No.: 3253-39-2), ethylene glycol diacrylate (CAS No.: 2274-11-5), ethylene glycol dimethacrylate (CAS No.: 97-90-5), trimethyloylpropane propoxylate triacrylate (CAS No.: 53879-54-2), trimethyloylpropane triacrylate (CAS No.: 15625-89-5) and / or Di(trimethylolpropane) tetraacrylate (CAS No.: 94108-97-1).Particularly preferred are 2-hydroxy-3-phenoxypropyl acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate and diurethane dimethacrylate.

[0093] In principle, preference is given to a curable adhesive composition according to the invention, wherein the polymerizable compounds Y are selected from the group consisting of (meth)acrylate monomers, preferably acrylate monomers, particularly preferably aromatic acrylate monomers, very particularly preferably 2-hydroxy-3-phenoxypropyl acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate and diurethane dimethacrylate.

[0094] Polymerizable compounds Y based on cyclic ethers are, in particular, epoxides, i.e., compounds that carry at least one oxirane group, or oxetanes. They can be aromatic or, in particular, aliphatic or cycloaliphatic in nature. Epoxy-containing materials or epoxy resins can be used as polymerizable compounds Y, which are any organic compounds with at least one oxirane ring that are polymerizable by a ring-opening reaction. Such materials include both monomeric and polymeric epoxides and can be aliphatic, cycloaliphatic, or aromatic. These materials frequently have, on average, at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule.

[0095] The polymeric epoxides mostly include linear polymers with terminal epoxide groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol), polymers with backbone oxirane units (e.g., polybutadiene polyepoxide), and polymers with pendant epoxide groups (e.g., a glycidyl methacrylate polymer or copolymer). The molecular weight of such epoxy compounds can vary from 58 to about 100,000 g / mol or more. Exemplary epoxy-containing polymerizable compounds Y include, for example, epoxycyclohexanecarboxylates, such as, for example, 4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. Further examples of epoxy-containing polymerizable compounds Y are disclosed, for example, in US 3,117,099 A.Other epoxy-containing polymerizable compounds Y that are particularly useful in the practice of this invention include glycidyl ether monomers, such as those disclosed in US Pat. No. 3,018,262. Examples are the glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin (e.g., the diglycidyl ether of 2,2-bis(2,3-epoxypropoxyphenol)propane). In particular, diglycidyl ethers of bisphenols, such as bisphenol A (4,4'-(propane-2,2-diyl)diphenol). Such reaction products are commercially available in various molecular weights (Type 1 to Type 10 resins). Typical examples of liquid bisphenol A diglycidyl ethers are Epikote 828, DER331 and Epon 828. Typical solid BADGE resins are Araldite GT6071, GT7072, Epon 1001 and DER 662. Other reaction products of phenols with epichlorohydrin are the phenol and cresol novolac resins such asthe Epiclon types or Araldite EPN and ECN types (e.g. ECN 1273).

[0096] Accordingly, a curable adhesive composition according to the invention is preferred, wherein the polymerizable compounds Y are selected from the group consisting of epoxy compounds, in particular epoxy monomers, preferably epoxy monomers comprising at least one cycloaliphatic epoxy group, particularly preferably 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate.

[0097] In this respect, a curable adhesive composition according to the invention is preferred, wherein the curable adhesive composition comprises one or more epoxy compounds, in particular epoxy resins, as polymerizable compound Y, wherein at least one of the epoxy compounds is a solid; in particular a solid having a softening temperature of at least 45°C, or a highly viscous substance, preferably having a dynamic viscosity at 25°C of 50 Pa s or more, particularly preferably 100 Pa s or more, especially preferably 150 Pa s or more (measured according to DIN 53019-1; 25°C, shear rate 1 s -1 ), is.

[0098] Particularly preferred is a curable adhesive according to the invention, wherein the curable adhesive comprises two or more epoxy compounds, in particular epoxy resins, as polymerizable compound Y, wherein at least one epoxy compound is a liquid with a dynamic viscosity of 40 Pa s or less, preferably 20 Pa s or less, at 25°C, and at least one epoxy compound is a solid or a highly viscous substance with a dynamic viscosity of 50 Pa s or more at 25°C. The combined mass fraction of the liquid epoxy compounds, whose dynamic viscosity at 25°C is 40 Pa s or less, in the polymerizable compounds Y is in particular 10 to 90%, preferably 20 to 75%, particularly preferably more than 50%, very particularly preferably more than 70%. The respective difference to 100 wt.% of the epoxy resins is then given by solid or highly viscous epoxy resins.Curable adhesives with such ratios of liquid and solid or highly viscous epoxy components exhibit particularly balanced adhesive properties in the uncured state. If an adhesive tape with particularly good flow properties is desired, the combined mass fraction of liquid epoxy compounds with a dynamic viscosity of 40 Pa s or less at 25 °C is preferably in the range of 50 to 80%. For applications where the adhesive tapes must bear a higher load even in the uncured state, a combined mass fraction of 15 to 45% is particularly preferred.

[0099] It can be seen as an advantage of the curable adhesives according to the invention that high cohesion and sufficient die-cutting ability can be achieved even with large mass fractions of liquid polymerizable compounds Y. Accordingly, it is particularly preferred if such liquid reactive resins are also used in the curable adhesive, which is particularly preferred with regard to the flow behavior to be achieved. Preference is therefore given to a curable adhesive according to the invention wherein at least one, preferably all, of the polymerizable compounds Y are liquid at 25°C, preferably with a dynamic viscosity of 40 Pa s or less, more preferably 20 Pa s or less; most preferably 10 Pa s or less.Very particular preference is given to a curable adhesive according to the invention wherein the combined mass fraction of polymerizable compounds Y liquid at 25°C is 15% or more, preferably 25% or more, particularly preferably 35% or more, very particularly preferably 45% or more. As explained above, a particularly advantageous feature of the curable adhesives according to the invention is that even with large mass fractions of reactive resins, which are fundamentally particularly desirable with regard to the subsequent flow behavior and also the adhesive strength to be achieved, curable adhesives with excellent cohesion and processability can be obtained. In light of this circumstance, particularly advantageous curable adhesives also result when correspondingly large mass fractions of the polymerizable compound Y are provided, since the advantages are particularly evident in this case.Accordingly, a curable adhesive according to the invention is preferred, wherein the combined mass fraction of the polymerizable compounds Y in the curable adhesive is 30% or more, preferably 40% or more, and / or wherein the combined mass fraction of the polymerizable compounds Y in the curable adhesive is in the range from 20 to 80%, preferably in the range from 30 to 75%, particularly preferably in the range from 40 to 70%.

[0100] Even though it is in principle possible to produce the A and / or B blocks at least partially from methacrylate monomers, the inventors believe that the use of acrylate monomers is particularly preferred, especially since their processing properties generally favor the production of high-performance curable adhesives. Therefore, preferred for all embodiments is a curable adhesive according to the invention, wherein the one or more (meth)acrylate block copolymers X are acrylate block copolymers, with the A blocks and the B block representing acrylate polymers.

[0101] In the inventors' opinion, it is an advantage of the curable adhesives according to the invention that the favorable cohesive properties arise even at comparatively low mass fractions of the (meth)acrylate block copolymers. In this respect, however, the inventors' experiments show that it is advantageous, particularly with regard to the achievable adhesive strength, to increase the mass fraction of this component. Preference is given to a curable adhesive according to the invention wherein the combined mass fraction of the (meth)acrylate block copolymers X in the curable adhesive is 25% or more, preferably 30% or more, and / or wherein the combined mass fraction of the (meth)acrylate block copolymers X in the curable adhesive is in the range from 20 to 70%, preferably in the range from 25 to 65%, particularly preferably in the range from 30 to 55%.

[0102] In this respect, the inventors have particularly succeeded in identifying suitable ratios of components X and Y. A curable adhesive composition according to the invention is preferred, wherein the ratio of the combined amounts of the (meth)acrylate block copolymers X to the combined amount of the polymerizable compounds Y is in the range from 3:1 to 1:3, preferably in the range from 2:1 to 1:2, particularly preferably in the range from 1.5:1 to 1:1.5.

[0103] In the inventors' estimation, the focus in distinguishing between A and B blocks in the context of the present invention is primarily on the different polarities, which are evaluated as described above. Nevertheless, the glass transition temperature also plays a complementary role; based on the inventors' findings, the limit can be seen as 50 °C, as defined above. However, in the inventors' estimation, it is advantageous for the physicochemical properties to be achieved in the curable adhesive if hard blocks with a comparatively high glass transition temperature are used as A blocks and correspondingly B blocks with a relatively low glass transition temperature are used as soft blocks.Preference is given to a curable adhesive composition according to the invention wherein the A blocks independently of one another represent a poly(meth)acrylate having a glass transition temperature Tg of more than 60°C, preferably more than 70°C, particularly preferably more than 80°C, and / or wherein the B block represents a poly(meth)acrylate having a glass transition temperature Tg of less than 40°C, preferably less than 30°C, particularly preferably less than 20°C.

[0104] As explained above, it is not necessarily necessary, and in light of the typical variance in the production of polymers, also not to be expected, that the A blocks in every (meth)acrylate block copolymer are identical, so that the above definition ultimately only defines a minimum or maximum glass transition temperature and the chemical nature of the monomeric units in the respective (co)polymers. However, the person skilled in the art understands that, particularly with regard to production-related aspects and with regard to the homogeneity of the physico-chemical properties of the curable adhesive that can be produced therewith, those (meth)acrylate block copolymers in which the A blocks are as similar as possible are preferred. It is considered particularly advantageous if the A blocks are produced in such a way that, within the typical variance in polymer chemistry, they are essentially identical or exhibit a low polydispersity.According to the expert's understanding, particularly high-performance (meth)acrylate block copolymers are obtained when the A blocks are prepared from the same A monomer composition under identical polymerization conditions. In this context, a curable adhesive composition according to the invention is preferred, wherein the two A blocks represent poly(meth)acrylates whose glass transition temperature differs by less than 5°C, preferably by less than 3°C, particularly preferably by less than 1°C, wherein the poly(meth)acrylates are preparable by polymerizing the same A monomer composition from A monomers, wherein the A blocks are preferably substantially identical.

[0105] Even if the use of copolymers in the A and B blocks is conceivable in principle, potentially also with at least small proportions of monomers that are not (meth)acrylate-based monomers, in the opinion of the inventors it is preferred for the vast majority of cases if the A or B blocks are as largely (meth)acrylate-based as possible and, in this respect, very preferably consist essentially of one type of acrylate-based monomer.Preference is therefore given to a curable adhesive composition according to the invention, wherein the A monomers comprise one or more monomers, preferably one monomer, which are selected from the group consisting of (meth)acrylate monomers and (meth)acrylic acid, preferably acrylate monomers and acrylic acid, particularly preferably acrylate monomers, wherein the A monomers preferably consist of 90% or more, particularly preferably 95% or more, very particularly preferably 99% or more, most preferably substantially completely, of these monomers, based on the combined mass of the A monomers.Also preferred is a curable adhesive composition according to the invention, wherein the B monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of (meth)acrylate monomers and (meth)acrylic acid, preferably acrylate monomers and acrylic acid, particularly preferably acrylate monomers, wherein the B monomers preferably consist of 90% or more, particularly preferably 95% or more, very particularly preferably 99% or more, and most preferably essentially completely, of these monomers, based on the combined mass of the B monomers. In this respect, it is particularly preferred if the above features are set in the same way for the A monomers and B monomers, and it is particularly preferred if the respective monomers are each formed essentially completely from a corresponding monomer of the specified types.The corresponding (meth)acrylate block copolymers not only result in excellent cohesion in the curable adhesives, but are also particularly easy, reliable and reproducible to produce, so that storage costs can be reduced and the establishment of consistent product quality is made easier.

[0106] Based on the above statements, the inventors have succeeded in identifying particularly suitable monomers for the A monomers and the B monomers, and thus for the chemical nature of the A and B blocks, which, in the inventors' estimation, result in particularly high-performance curable adhesives according to the invention, whereby the above statements regarding the formation of the A and B blocks as largely pure polymers apply accordingly. The A monomers designated as preferred below are particularly advantageous because they exhibit the required difference in the polar portion of the Hansen solubility parameters compared to a wide range of commonly used reactive resins, in particular to typical epoxy monomers with at least one cycloaliphatic epoxy group and aromatic acrylate monomers.In the same way, the B monomers referred to below as preferred are particularly favorable since their polarity lies within the defined range for the two preferred classes of reactive resins.

[0107] Preference is given to a curable adhesive composition according to the invention, wherein the A monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of n-octyl acrylate, 2-ethylhexyl acrylate, propylheptyl acrylate, 2-phenoxyethyl acrylate, isobornyl acrylate, dihydrodicyclopentadienyl acrylate, lauryl acrylate, stearyl acrylate and heptadecyl acrylate, preferably propylheptyl acrylate, 2-phenoxyethyl acrylate, isobornyl acrylate, dihydrodicyclopentadienyl acrylate, lauryl acrylate, stearyl acrylate and heptadecyl acrylate, particularly preferably phenoxyethyl acrylate, isobornyl acrylate and dihydrodicyclopentadienyl acrylate, wherein the A monomers preferably consist of 90% or more, particularly preferably 95% or more, very particularly preferably 99% or more, most preferably substantially completely, of these Monomers consist of the combined mass of the A monomers.Also preferred is a curable adhesive composition according to the invention, wherein the B monomers comprise one or more monomers, preferably one monomer, which are selected from the group consisting of n-octyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methoxyethyl acrylate, ethylene diglycol acrylate, 2-phenoxydiethylene glycol acrylate, methyl acrylate, ethyl acrylate, tert-butyl acrylate, n-butyl acrylate, methyl methacrylate and acrylic acid, preferably from hydroxyethyl acrylate, methoxyethyl acrylate, ethylene diglycol acrylate, 2-phenoxydiethylene glycol acrylate, methyl acrylate, ethyl acrylate, tert-butyl acrylate, n-butyl acrylate, methyl methacrylate and acrylic acid, particularly preferably n-butyl acrylate, ethyl acrylate and acrylic acid, wherein the B monomers preferably comprise 90% or more, particularly preferably 95% or more more, most preferably 99% or more, most preferably substantially completely, of these monomers, based on the combined mass of the B monomers.The overlap in the monomers n-octyl acrylate and 2-ethylhexyl acrylate listed here results from the fact that these monomers are particularly suitable for A or B blocks, depending on the reactive resin used.

[0108] The number average molecular weights M n of the (meth)acrylate block copolymers X are preferably in a range from 20,000 to 2,000,000 g / mol, particularly preferably in a range from 100,000 to 1,500,000 g / mol, and most preferably in a range from 150,000 to 1,000,000 g / mol. The number-average molar mass Mn refers to the determination by gel permeation chromatography (GPC). The determination is carried out on 100 μl of a clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1 vol% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C. The precolumn used is a PSS-SDV column, 5 μm, 10 3Ä, 8.0 mm * 50 mm (information here and below in the order: type, particle size, porosity, inner diameter * length; 1 Ä = 10 -10 m). For separation, a combination of columns of type PSS-SDV, 5 pm, 10 3 Ä and 10 5 Ä and 10 6 Ä with a diameter of 8.0 mm x 300 mm each (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate is 1.0 ml per minute. Calibration is performed for polyacrylates against PMMA standards (polymethyl methacrylate calibration) and for other materials (resins, elastomers) against PS standards (polystyrene calibration).

[0109] Even if the limit value of 3.5 MPa defined above 05According to the inventors' knowledge, this is the sensible dividing line for distinguishing suitable A and B blocks, it is particularly advantageous, in the inventors' estimation, to choose the polarity difference for the A blocks as large as possible and to aim for a polarity with the B blocks that is as close as possible to that of the polarizable compounds Y. Therefore, a curable adhesive composition according to the invention is preferred, wherein for the substance-weighted polar components the Hansen solubility parameter <ö p > it holds that |<Ö P >(A) - <Ö P >(Y)| > 3.8 MPa 05 , preferably |<Ö P >(A) - <Ö P >(Y)| > 4.5 MPa 05 , especially preferred |<ö p >(A) - <Ö P >(Y)| > 5.2 MPa 05 , and / or where for the molar mass weighted polar fractions the Hansen solubility parameter <ö p > it holds that |<ö p >(B) - <Ö P >(Y)| < 3.4 MPa 05 , preferably |<Ö P >(B) - <ÖP >(Y)| < 2.8 MPa 05 , particularly preferred |<öp>(B) - <ö p >(Y)| < 2.2 MPa 05 .

[0110] In the course of developing the invention, the inventors have succeeded in identifying suitable ranges for the absolute polar fractions of the Hansen solubility parameter of the A monomers and the B monomers as well as of the polymerizable compounds Y, with which particularly high-performance curable adhesives can be realized. The ranges identified in this regard are, in the opinion of the inventors, particularly helpful in quickly and reliably designing new (meth)acrylate block copolymers for the respective applications, since the corresponding polar fractions of the Hansen solubility parameters can be looked up, for example, from tabulated values ​​in light of this disclosure. Preference is given to a curable adhesive according to the invention wherein the substance-weighted polar fraction of the Hansen solubility parameter of the monomer units derived from A monomers in the A blocks is <ö p >(A) in the range of 0.5 to 7.5 MPa05 , preferably in the range of 1.0 to 7.0 MPa 05 , particularly preferably in the range of 1.5 to 6.5 MPa 05 , and / or wherein the molar mass-weighted polar fraction of the Hansen solubility parameter of the monomer units derived from B monomers in the B block <ö p >(B) in the range of 8.0 to 13.0 MPa 05 , preferably in the range of 8.5 to 12.0 MPa 05 , particularly preferably in the range of 9.0 to 11.0 MPa 05 , and / or wherein the substance-weighted polar portion of the Hansen solubility parameter of the polymerizable compounds Y in the curable adhesive is <ö p >(Y) in the range of 8.5 to 13.0 MPa 05 , preferably in the range of 9.0 to 12.5 MPa 05 , particularly preferably in the range of 9.5 to 12.0 MPa 05 , lies.

[0111] Finally, it can be seen as an advantage of curable adhesives according to the invention that they are very flexible with regard to the use of typical additives, so that the physicochemical properties can be further adapted specifically to the requirements of the respective application. Thus, a curable adhesive is preferred, wherein the curable adhesive comprises one or more further additives, preferably in a combined mass fraction in the range of 0.1 to 50%, preferably 0.2 to 40%, based on the mass of the adhesive, and / or wherein the one or more further additives are preferably selected from the group consisting of tackifier resins, anti-aging agents, light stabilizers, UV absorbers, and rheological additives.

[0112] A special case of the additional components that serve to adjust the properties of adhesives are insoluble fillers that can be added to the curable adhesive to obtain a filled curable adhesive. These are particulate fillers with an average particle diameter (D50) of 5 μm or more, preferably 10 μm or more, particularly preferably 20 μm or more, which are insoluble in the curable adhesive and are accordingly present therein as a dispersion, as well as macroscopic fillers such as, for example, fibers. The insoluble fillers are preferably selected from the group consisting of particulate fillers. The insoluble fillers are particularly preferably selected from the group consisting of expandable hollow polymer spheres, non-expandable hollow polymer spheres, solid polymer spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres and / or solid carbon spheres.However, fibers, scrims, platelets, and rods made of materials that are insoluble in the curable adhesive can also be considered as insoluble fillers. Due to their partially already macroscopic dimensions and their lack of solubility, these essentially have no influence on the above-disclosed relationships in the compositional chemistry of the curable adhesives, but rather are present in a heterogeneous mixture with the curable adhesive. Accordingly, these insoluble fillers are not attributed to the curable adhesive in the context of the present invention and are accordingly not taken into account when calculating mass fractions relative to the mass of the curable adhesive. As described above, it is rather defined in the context of the present invention that the addition of insoluble fillers to a curable adhesive according to the invention results in a filled curable adhesive, i.e.a filled curable adhesive composition comprising: x) a curable adhesive composition according to the invention, preferably as disclosed above as preferred, and y) one or more insoluble fillers.

[0113] The combined mass fraction of the insoluble fillers is particularly preferably in the range from 1 to 50%, preferably in the range from 2 to 40%, particularly preferably in the range from 5 to 30%, based on the mass of the filled curable adhesive.

[0114] Disclosed below are exemplary curable adhesives which, in the opinion of the inventors, are particularly advantageous and which describe particularly preferred combinations of features, with particular preference being given to curable adhesives according to the invention which comprise two or more of the exemplary curable adhesives.Preference is given to a first thermally curable adhesive composition according to the invention based on radically curing polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 30 to 55%, ii) a liquid acrylate monomer, for example phenoxyethyl acrylate, in a mass fraction in the range from 20 to 35%, iii) a highly viscous acrylate oligomer, for example Ebecryl 600 (viscosity at 25 °C of more than 150 Pa s), in a mass fraction in the range from 20 to 35%, and iv) a thermal radical initiator, for example benzpinacol, in a mass fraction in the range from 0.5 to 5%.

[0115] Also preferred is a second UV-curable adhesive composition according to the invention based on radically curing polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 25 to 45%, ii) a liquid acrylate monomer, for example phenoxyethyl acrylate, in a mass fraction in the range from 20 to 40%, iii) a highly viscous acrylate oligomer, for example Ebecryl 600 (viscosity at 25 °C of more than 150 Pa s), in a mass fraction in the range from 20 to 40%, iv) a radical initiator, for example diisopropylbenzene hydroperoxide, in a mass fraction in the range from 0.5 to 5%, and v) a photoredox catalyst, for example (Ru(bypy)s Ch), in a mass fraction in the range from 0.01 to 2 %.

[0116] Also preferred is a third UV-curable adhesive composition according to the invention based on radically curing polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 40 to 60%, ii) a liquid acrylate monomer, for example phenoxyethyl acrylate, in a mass fraction in the range from 10 to 35%, iii) a highly viscous acrylate oligomer, for example Ebecryl 600 (viscosity at 25 °C of more than 150 Pa s), in a mass fraction in the range from 10 to 35%, iv) a radical initiator, for example diisopropylbenzene hydroperoxide, in a mass fraction in the range from 0.5 to 5%, and v) a photoredox catalyst, for example (Ru(bypy)s Ch), in a mass fraction in the range from 0.01 to 2 %.

[0117] Also preferred is a fourth UV-curable adhesive composition according to the invention based on radically curing polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 25 to 45%, ii) a liquid acrylate monomer, for example phenoxyethyl acrylate, in a mass fraction in the range from 10 to 30%, iii) a highly viscous acrylate oligomer, for example Ebecryl 600 (viscosity at 25°C of more than 150 Pa s), in a mass fraction in the range from 10 to 30%, iv) a filler, for example Silibeads 5211, in a mass fraction of 25%, v) a radical initiator, for example diisopropylbenzene hydroperoxide, in a mass fraction in the range from 0.5 to 5%, and vi) a Photoredox catalyst, for example (Ru(bypy)s Ch), in a mass fraction in the range of 0.01 to 2%.

[0118] Also preferred is a fifth UV-curable adhesive according to the invention based on free-radically curing polymerizable compounds Y, comprising, based on the mass of the adhesive: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 25 to 45%, ii) a liquid acrylate monomer, for example phenoxyethyl acrylate, in a mass fraction in the range from 20 to 40%, iii) a polymeric additive, for example poly-N-vinylpyrrolidone, in a mass fraction in the range from 10 to 30%, iv) a free-radical initiator, for example diisopropylbenzene hydroperoxide, in a mass fraction in the range from 0.5 to 5%, and v) a photoredox catalyst, for example (Ru(bypy)s Ch), in a mass fraction in the range from 0.01 to 2%.

[0119] Also preferred is a sixth thermally curable adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 30 to 45%, ii) a liquid epoxy, for example Epikote828, in a mass fraction in the range from 20 to 35%, iii) a solid epoxy, for example Araldite ECN 1273, in a mass fraction in the range from 20 to 35%, iv) a hardener, for example dicyandiamide, in a mass fraction in the range from 2 to 6%, and v) an accelerator, for example Curezol MZ-A, in a mass fraction in the range from 0.01 to 0.5%.

[0120] Also preferred is a seventh thermally curable adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 45 to 60%, ii) a liquid epoxy, for example Epikote828, in a mass fraction in the range from 15 to 30%, iii) a solid epoxy, for example Araldite ECN 1273, in a mass fraction in the range from 15 to 30%, iv) a hardener, for example dicyandiamide, in a mass fraction in the range from 2 to 5%, and v) an accelerator, for example Curezol MZ-A, in a mass fraction in the range from 0.01 to 0.5%.

[0121] Also preferred is an eighth thermally curable adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 20 to 50%, ii) a liquid epoxy, for example Epikote828, in a mass fraction in the range from 10 to 25%, iii) a solid epoxy, for example Araldite ECN 1273, in a mass fraction in the range from 10 to 25%, iv) a hardener, for example dicyandiamide, in a mass fraction in the range from 2 to 5%, v) an accelerator, for example Curezol MZ-A, in a mass fraction in the range from 0.01 to 0.5%, and vi) a filler, for example Silibeads 5211, in a mass fraction of 30%.

[0122] Also preferred is a ninth thermally curable adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 20 to 35%, ii) a liquid epoxy, for example Epikote 828, in a mass fraction in the range from 0 to 25%, iii) a solid epoxy, for example Araldite ECN 1273, in a mass fraction in the range from 10 to 40%, iv) a high-viscosity epoxy, for example Struktol PD3611 (viscosity at 25°C of more than 150 Pa s), in a mass fraction in the range from 10 to 40%, v) a hardener, for example dicyandiamide, in a mass fraction in the range from 2 to 7%, and vi) an accelerator, for example Curezol MZ-A, in a mass fraction in the range of 0.01 to 0.7%.

[0123] Also preferred is a tenth thermally curable adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 20 to 35%, ii) a solid epoxy, for example Araldite ECN 1273, in a mass fraction in the range from 10 to 60%, iii) a highly viscous epoxy, for example Struktol PD3611 (viscosity at 25 °C of more than 150 Pa s), in a mass fraction in the range from 10 to 60%, iv) a hardener, for example dicyandiamide, in a mass fraction in the range from 2 to 7%, and v) an accelerator, for example Curezol MZ-A, in a mass fraction in the range from 0.01 to 0.7%.

[0124] Also preferred is an eleventh light-curing adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 45 to 60%, ii) an epoxide obtained from the reaction of an alcohol with epichlorohydrin, for example Epikote828 (liquid) or Araldite GT7072 (solid), in a mass fraction in the range from 15 to 35%, iii) a cycloaliphatic epoxide, for example Uvacure 1500, in a mass fraction in the range from 15 to 35%, iv) an open-time additive, for example polyethylene glycol (Mn~400g / mol), in a mass fraction in the range from 0.5 to 10%, and v) a photoinitiator, for example a triarylsulfonium antimonate salt, in a mass fraction in the range from 0.3 to 2%.

[0125] Also preferred is a twelfth light-curing adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 25 to 50%, ii) an epoxide obtained from the reaction of an alcohol with epichlorohydrin, for example Epikote828 (liquid) or Araldite GT7072 (solid), in a mass fraction in the range from 15 to 45%, iii) a cycloaliphatic epoxide, for example Uvacure 1500, in a mass fraction in the range from 15 to 45%, iv) an open-time additive, for example polyethylene glycol (Mn~400g / mol), in a mass fraction in the range from 0.5 to 10%, and v) a photoinitiator, for example a triarylsulfonium antimonate salt, in a mass fraction in the range from 0.3 to 2%.

[0126] Also preferred is a thirteenth light-curing adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 20 to 50%, ii) an epoxide obtained from the reaction of an alcohol with epichlorohydrin, for example Epikote828 (liquid) or Araldite GT7072 (solid), in a mass fraction in the range from 15 to 35%, iii) a cycloaliphatic epoxide, for example Uvacure 1500, in a mass fraction in the range from 15 to 35%, iv) an open-time additive, for example polyethylene glycol (Mn~400g / mol), in a mass fraction in the range from 0.5 to 10%, v) a photoinitiator, for example a triarylsulfonium antimonate salt, in a mass fraction in the range from 0.3 to 2% and vi) a filler, for example glass beads or Silibeads 5211, in a mass fraction of 30%.

[0127] Also preferred is a fourteenth light-curing adhesive composition according to the invention based on cyclic ether compounds as polymerizable compounds Y, comprising, based on the mass of the adhesive composition: i) a corresponding (meth)acrylate block copolymer X1 of the structure ABA in a mass fraction in the range from 20 to 50%, ii) a liquid epoxy, for example bisphenol A diglycidyl ether (e.g. Epikote828) or cycloaliphatic epoxides (e.g. Uvacure 1500) in a mass fraction in the range from 10 to 45%, iii) a solid epoxy, for example bisphenol A diglycidyl ether (e.g. Araldite GT7072) or epoxy-cresol or epoxy phenol novolaks (e.g.Araldite ECN 1273), in a mass fraction in the range of 10 to 45%, iv) an open time additive, for example polyethylene glycol (Mn~400g / mol), in a mass fraction in the range of 0.5 to 10%, and v) a photoinitiator, for example a triarylsulfonium antimonate salt, in a mass fraction in the range of 0.3 to 2%, and optionally vi) a polyol, for example polycaprolactone (e.g. Capa2000) in a mass fraction in the range of 5 to 15%.

[0128] Curable adhesives according to the invention can, for example, be used directly as adhesives, and depending on the application method, they can also be provided, for example, in the form of tapes. However, with a view to the most favorable handling properties possible, particularly advantageous results are generally achieved when curable adhesives according to the invention are used as the adhesive layer of a single- or double-sided adhesive tape that also comprises a carrier layer. The invention thus also relates to an adhesive tape, in particular a reactive adhesive tape, comprising a curable adhesive according to the invention as the adhesive layer, wherein the adhesive tape preferably comprises a carrier layer.

[0129] The term "adhesive tape" is familiar to those skilled in the field of adhesive technology. Within the context of the present invention, the term "tape" refers to all thin, flat structures, i.e., structures with a predominantly two-dimensional extension, in particular films, film sections, and labels, preferably tapes with an extended length and a limited width, as well as corresponding tape sections.

[0130] The carrier layer usually refers to the layer of such a multilayer adhesive tape that significantly determines the mechanical and physical properties of the adhesive tape, such as tear resistance, stretchability, insulation, or resilience. Typical materials for the carrier layer include fabrics, scrims, and plastic films, such as PET films and polyolefin films. However, the carrier layer itself can also be pressure-sensitively adhesive. In a preferred embodiment, the adhesive tape according to the invention can be a double-sided adhesive tape whose carrier layer is provided on both sides with a curable adhesive according to the invention.

[0131] In adhesive tapes according to the invention, the adhesive layers can be covered with a so-called release liner to enable smooth unwinding and protect the pressure-sensitive adhesive from contamination. Such release liners typically consist of a single- or double-sided siliconized plastic film (e.g., PET or PP) or a siliconized paper carrier.

[0132] Starting from the curable adhesive composition according to the invention and the adhesive tape according to the invention, the use of a curable adhesive composition according to the invention or an adhesive tape according to the invention for bonding two or more components by curing the curable adhesive composition is also disclosed.

[0133] Finally, a process for producing a curable adhesive according to the invention is also disclosed, comprising the process steps: a) producing or providing an A monomer composition from A monomers, b) polymerizing the A monomer composition using a RAFT initiator to obtain an A poly(meth)acrylate, c) producing or providing a B monomer composition from B monomers, d) mixing the A poly(meth)acrylate with the B monomer composition and copolymerizing the mixture to obtain a (meth)acrylate block copolymer X of structure ABA, and e) mixing the (meth)acrylate block copolymer X with one or more polymerizable compounds Y and one or more initiators, and optionally one or more further additives, to obtain the curable adhesive, wherein the polymerization in process step b) and the copolymerization in process step d) takes place by means of RAFT polymerization.

[0134] In light of the above disclosure, it is clear to the person skilled in the art that the invention also relates to two specific aspects, each of which is of central importance to the invention and to which the above disclosures concerning preferred curable adhesive compositions apply accordingly.

[0135] The first aspect relates to a curable adhesive composition, comprising, based on the mass of the curable adhesive composition: a) one or more (meth)acrylate block copolymers X of the structure ABA in a combined mass fraction of 20% or more, wherein the A blocks independently of one another represent a poly(meth)acrylate having a glass transition temperature Tg of 50°C or more, which can be prepared by polymerizing an A monomer composition from A monomers, wherein the B block represents a poly(meth)acrylate having a glass transition temperature Tg of less than 50°C, which can be prepared by polymerizing a B monomer composition from B monomers, and b) one or more polymerizable epoxy compounds Y, in particular epoxy resins, in a combined mass fraction of 20% or more, and wherein for the substance amount-weighted polar fractions the Hansen solubility parameter <ö p >: i) the monomer units derived from A monomers in the A blocks <ö P>(A), ii) the monomer units derived from B monomers in the B block <ö p >(B), and iii) the polymerizable epoxy compounds Y <ö p >(Y), it holds that:

[0136] |<ö p >(A) - <ö p >(Y)| > 3.5 MPa 05 , and

[0137] |<ö p >(B) - <ö p >(Y)| < 3.5 MPa 05 .

[0138] The second aspect relates to a curable adhesive composition, comprising, based on the mass of the curable adhesive composition: a) one or more (meth)acrylate block copolymers X of the structure ABA in a combined mass fraction of 20% or more, wherein the A blocks independently of one another represent a poly(meth)acrylate having a glass transition temperature Tg of 50°C or more, which can be prepared by polymerizing an A monomer composition from A monomers, wherein the B block represents a poly(meth)acrylate having a glass transition temperature Tg of less than 50°C, which can be prepared by polymerizing a B monomer composition from B monomers, and b) one or more polymerizable (meth)acrylate monomers Y in a combined mass fraction of 20% or more, and wherein for the substance-weighted polar fractions the Hansen solubility parameter <ö p >: i) the A monomers in the A monomer composition <ö p>(A), ii) the B monomers in the B monomer composition <ö p >(B), and iii) the polymerizable (meth)acrylate monomers Y <ö p >(Y), it holds that:

[0139] |<ö p >(A) - <ö p >(Y)| > 3.5 MPa 05 , and

[0140] |<ö p >(B) - <ö p >(Y)| < 3.5 MPa 05 .

[0141] Preferred embodiments of the invention are further explained and described below with reference to experiments. A. Preparation of the (meth)acrylate block copolymers X of structure ABA:

[0142] General experimental conditions:

[0143] The reactions were carried out under a nitrogen atmosphere at room temperature (25 °C) in a 60 ml EPA screw-top bottle. The radiation sources were two Skymore 110W UV LED nail dryer lamps, each with a power of 110 W and an emitted wavelength of 365 nm. The lamps were positioned so that the reaction vessel could be placed 2 cm from the LEDs.

[0144] Synthesis of homopolymers (HP1 to HP4) and comparison copolymer (VP1):

[0145] To synthesize the homopolymers HP1 to HP4 and VP1, a mixture of DBTTC (S,S-dibenzyltrithiocarbonate), IBOA (isobornyl acrylate), (and for VP1 also BA; n-butyl acrylate), and toluene was homogenized according to the detailed instructions in Table 4 and then purged with nitrogen for 10 min. The RAFT polymerization was initiated by UV irradiation of the reaction mixture. To terminate the reaction, the irradiation was interrupted, and the highly viscous reaction mixture was dissolved in THF, precipitated dropwise in an excess of cold methanol, and the resulting precipitate was filtered. The homopolymers isolated in this way (HP1 to HP4) can be converted into block copolymers by chain extension as macrointerferons, whereas VP1 serves as a reference polymer. Information on the resulting homopolymers is summarized in Table 4.

[0146] Table 4 - Overview of homopolymers (HP1 to HP4) and comparative co-

[0147] Polymer (VP1)

[0148] The concentrations of macroiniferter and butyl acrylate specified in Table 5 were dissolved in toluene and purged with nitrogen for 10 min. Polymerization was then initiated by switching on the radiation source. After irradiation, the reaction mixture was dissolved in toluene. Using an automatic film applicator, the solution was coated onto a siliconized PET film and then removed from toluene and residual monomer at 120 °C in an oven for 20 min, yielding the ABA triblock copolymer. Information on the resulting (meth)acrylate block copolymers is summarized in Table 5.

[0149] Table 5 - Overview of (meth)acrylate block copolymers (P1 to P4)

[0150] Abbreviation Iniferter sentence

[0151] P1 HP1 4.56 7.33 622 8.7 97

[0152] P2 HP2 5.56 2.29 2428 4.1 82

[0153] P3 HP3 5.56 14.7 378 9.0 96

[0154] P4 HP4 5.56 5.7 975 6.5 90

[0155] The A blocks of the (meth)acrylate block copolymers P1 to P4 made of IBOA (öp = 6.10 MPa 05 ) and the monomer units derived from them in VP1 have the required minimum distances in polarity to the reaction resins used (5.88 MPa 05 for epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate or 3.87 MPa 05 for HPPA).

[0156] The B blocks of the (meth)acrylate block copolymers P1 to P4 made of BA (öp = 8.60 MPa 05 ) and the monomer units derived from them in VP1, however, show a small difference in polarity to the reaction resins used (3.38 MPa 05 for epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate or 1.37 MPa 05 for HPPA).

[0157] As an additional comparison polymer (VP2), a commercially available (meth)acrylate block copolymer (Kurarity LA2250) was used, whose A blocks consisted of MMA (methyl methacrylate; öp = 9.31 MPa 05 ) do not meet the required minimum polarity distances to the reaction resins used (2.67 MPa 05 for epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate or 0.66 MPa 05 for HPPA). The properties of the polymers used are summarized in Table 6 below.

[0158] Table 6 - Properties of polymers

[0159] Abbreviation Type A-Monomer B-Monomer Mass fraction Mn

[0160] A-Block / % / (g / mol)

[0161] P1 block copolymer isobornyl acrylate butyl acrylate 30 150000

[0162] P2 block copolymer isobornyl acrylate butyl acrylate 30 370000

[0163] P3 block copolymer isobornyl acrylate butyl acrylate 45 100000

[0164] P4 block copolymer isobornyl acrylate butyl acrylate 45 220000

[0165] VP1 Statistical isobornyl acrylate butyl acrylate 30 330000

[0166] VP2 block copolymer methyl methacrylate butyl acrylate 30 -50000

[0167] Adhesives were obtained from the polymers by mixing them with the other components in the usual way. The composition of the adhesives is summarized in Table 7. Adhesive tapes with a thickness of approximately 100 μm were produced from the adhesives by spreading and evaporating the solvent.

[0168] Table 7 - Composition of adhesives and solvents, all data in parts by weight

[0169] B. Adhesive experiments:

[0170] The bond strengths were determined analogously to ISO 29862 (Method 3) at 23 °C and 50% relative humidity, at a peel speed of 300 mm / min and a peel angle of 180°. The thickness of the adhesive layer was 100 μm in each case. An etched PET film with a thickness of 50 gm, available from Coveme (Italy), was used as the reinforcing film. Steel plates in accordance with the standard were used as the substrate. The uncured test strip was bonded using a 4 kg rolling machine at a temperature of 23 °C. The adhesive tapes were removed immediately after application. The measured value (in N / cm) was the average of three individual measurements, and the failure pattern was documented as follows: adhesive failure (A) or cohesive failure (K).

[0171] In addition, the tensile shear strength of the cured adhesives was determined. The bond strength was quantitatively determined in a dynamic tensile shear test based on DIN EN 1465 at 23 °C and 50% relative humidity for a test speed of 1 mm / min (results in N / mm 2 = MPa). Steel test specimens were used, which were cleaned with acetone before bonding. The layer thicknesses of the adhesive tapes corresponded to the specifications above. Before joining the test specimens, the adhesive tapes were irradiated with suitable light after removing the second liner, and the test specimens were joined immediately thereafter. The measurements were taken after 7 days of storage at 23 °C and 50% relative humidity. The mean value of three measurements is given. The results of the experiments are summarized in Table 8.

[0172] Table 8 - Summary of the bonding experiments

[0173] A: adhesive failure; K: cohesive failure

[0174] The fracture pattern in the adhesive strength test demonstrates the advantageous cohesion-enhancing effect of the (meth)acrylate block copolymers used in the adhesive compositions according to the invention.

[0175] Although the adhesives contain almost 50% of a liquid reactive resin, they are sufficiently cohesive to allow for adhesive failure, as is typical for pressure-sensitive adhesives. In contrast, comparative examples C1 and C2 are pasty, non-cohesive adhesives that exhibit cohesive cleavage in the bond strength test.

[0176] The tensile shear tests after curing show that the adhesives cure and achieve good bond strengths, which indicates sufficient flow behavior. The advantage of the adhesives according to the invention is particularly evident in the positive combination of properties before and after curing.

Claims

Patent claims: Curable adhesive, comprising, with respect to the mass of the curable adhesive: a) one or more (meth)acrylate block copolymers X of structure AB-A in a combined mass fraction of 20% or more, wherein the A-blocks independently represent a poly(meth)acrylate with a glass transition temperature Tg of 50 °C or more, which can be produced by polymerization of an A- Monomer composition of A monomers, wherein the B block represents a poly(meth)acrylate with a a) glass transition temperature Tg of less than 50 °C, which can be produced by polymerization of a B-monomer composition from B-monomers, and b) one or more polymerizable compounds Y in a combined mass fraction of 20% or more, and wherein for the molar-weighted polar components of the Hansen solubility parameter <θ p >: i) the monomer units derived from A monomers in the A blocks <ö p>(A), ii) the monomer units derived from B monomers in the B-block <Ö P >(B), and iii) the polymerizable compounds Y <ö p >(Y), it holds that: |<ö p >(A) - <ö p >(Y)| > 3.5 MPa 05 , and |<ö p >(B) - <ö p >(Y)| < 3.5 MPa 05 . Curable adhesive according to claim 1, wherein the polymerizable compounds Y are selected from the group consisting of epoxy compounds, in particular epoxy monomers, and (meth)acrylate monomers. Curable adhesive according to claim 1 or 2, wherein the combined mass fraction of the polymerizable compounds Y in the curable adhesive is 30% or more, preferably 40% or more. Curable adhesive according to any one of claims 1 to 3, wherein the combined mass fraction of the (meth)acrylate block copolymers X in the curable adhesive is in the range of 20% to 70%, preferably in the range of 25% to 65%, and particularly preferably in the range of 30% to 55%.Curable adhesive according to any one of claims 1 to 4, wherein the A monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of (meth)acrylate monomers and (meth)acrylic acid, and / or wherein the B monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of (meth)acrylate monomers and (meth)acrylic acid. Curable adhesive according to claim 5, wherein the A monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of n-octyl acrylate, 2-ethylhexyl acrylate, propylheptyl acrylate, 2-phenoxyethyl acrylate, isobornyl acrylate, dihydrodicyclopentadienyl acrylate, lauryl acrylate, stearyl acrylate, and heptadecyl acrylate. Curable adhesive compound according to any one of claims 1 to 6, wherein the two A-blocks represent poly(meth)acrylates which can be produced by Polymerization of the same A-monomer composition from A-monomers, wherein the A-blocks are preferably identical. Curable adhesive according to any one of claims 5 to 7, wherein the B-monomers comprise one or more monomers, preferably one monomer, selected from the group consisting of n-octyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methoxyethyl acrylate, ethylene diglycol acrylate, 2-phenoxydiethylene glycol acrylate, methyl acrylate, ethyl acrylate, tert-butyl acrylate, n-butyl acrylate, methyl methacrylate, and acrylic acid. Curable adhesive according to any one of claims 1 to 8, wherein the molar-weighted polar component of the Hansen solubility parameter of the monomer units derived from A-monomers in the A-blocks <θ p >(A) in the range of 0.5 to 7.5 MPa 05 preferably in the range of 1.0 to 7.0 MPa 05 , particularly preferably in the range of 1.5 to 6.5 MPa 05, lies, and / or where the mole-weighted polar component of the Hansen solubility parameter of the monomer units derived from B monomers in the B-block <ö p >(B) in the range of 8.0 to 13.0 MPa 05 preferably in the range of 8.5 to 12.0 MPa 05 , particularly preferably in the range of 9.0 to 11.0 MPa 05 , lies, and / or where the mole-weighted polar component of the Hansen solubility parameter of the polymerizable compounds Y in the curable adhesive mass <ö p >(Y) in the range of 8.5 to 13.0 MPa 05 preferably in the range of 9.0 to 12.5 MPa 05 , particularly preferably in the range of 9.5 to 12.0 MPa 05 , lies. Adhesive tape comprising as an adhesive layer a curable adhesive compound according to any one of claims 1 to 9.

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