Curable adhesives with improved die-cutability and improved impact properties

Abstract

This invention relates to a curable adhesive, which, based on its mass, comprises: a) one or more A-B-A structured (meth)acrylate block copolymers comprising 25% or more by mass, wherein the A blocks independently represent poly(meth)acrylates having a glass transition temperature Tg of 50°C or higher, which can be prepared by polymerization of an A monomer component comprising an A monomer, wherein block B represents poly(meth)acrylates having a glass transition temperature Tg of less than 50°C, which can be prepared by polymerization of a B monomer component comprising a B monomer; b) one or more polymerizable first epoxy compound E1 comprising 5% or more by mass, wherein the first epoxy compound E1 is a solid or a high-viscosity substance at 25°C; and c) one or more polymerizable second epoxy compound E2 comprising 5% or more by mass, wherein the second epoxy compound E2 is a liquid at 25°C, wherein the Hansen solubility parameter of the monomer units from the A monomer in the A blocks is <δ. p The polar component of the substance weighted by the amount of substance (<δ) p >(A)) at 9.0 to 11.0 MPa 0.5 Within the range, and where the Hansen solubility parameter of the monomer unit from monomer B in block B is <δ p The polar component of the substance weighted by the amount of substance (<δ) p >(B)) less than 9.0 MPa 0.5 .

Description

Technical Field

[0001] This invention relates to curable adhesives and reactive tapes comprising such curable adhesives. Furthermore, it discloses the use of such curable adhesives and reactive tapes for bonding two or more components, and a method for manufacturing such curable adhesives. Background Technology

[0002] The connection of individual components is one of the core processes in manufacturing. Besides methods such as soldering and brazing, adhesive bonding, i.e., the use of adhesives for joining, is now particularly valued. An alternative using formless adhesives applied from a tube is, for example, so-called tape. Pressure-sensitive tapes are particularly known in everyday life, where the pressure-sensitive adhesive provides the bonding effect, exhibiting durable tack and adhesiveness under typical environmental conditions. Such pressure-sensitive tapes can be applied to a substrate under pressure and remain adhered there, but can later be removed again with more or less no residue.

[0003] However, there is another type of tape that is particularly important for industrial applications. These tapes, sometimes called reactive tapes, utilize curable adhesives. In their intended application state, these types of curable adhesives have not yet reached their maximum cross-linking degree and can be cured by external influences, where polymerization is initiated within the curable adhesive, subsequently increasing the degree of cross-linking. This is accompanied by changes in the mechanical properties of the cured adhesive, particularly increases in viscosity, surface hardness, and strength.

[0004] Curable adhesives are known in the art and can have very different compositions from a chemical point of view. A common characteristic of these curable adhesives is that the crosslinking reaction can be triggered by external influencing factors, such as energy supply, more particularly by heat, plasma, or radiation curing, and / or by contact with a polymerization-promoting substance, such as in the case of moisture-curing adhesives. Relevant adhesives are disclosed, for example, in DE 102015222028 A1, EP 3091059 A1, EP 3126402 B1, EP 2768919 B1, DE 102018203894 A1, WO 2017174303 A1, and US 4661542 A.

[0005] The curing properties of such curable adhesives are typically achieved through the use of polymerizable compounds, particularly crosslinkable monomers or oligomers. These low-molecular-weight polymerizable compounds (which must usually be used in a fairly large mass fraction to ensure sufficient curing properties) are sometimes referred to by technicians as reactive resins.

[0006] The low molecular weight reactive resins typically used are usually low-viscosity liquids. Combined with a high mass fraction in curable adhesives, this makes the curable adhesive itself typically low in viscosity. Because of this, the processability of many curable adhesives in the prior art is considered inadequate, and proper processing of curable adhesives involves relatively high costs and complexities in typical processing techniques in the adhesive industry. Besides the dimensional stability of pressure-sensitive adhesives during winding, die-cutting capability, in particular, the suitability for dividing bonded elements through die-cutting processes, is often evaluated as inadequate.

[0007] To provide end users with optimal processing quality, curable adhesives generally need to possess at least weak, pronounced pressure-sensitive adhesive properties. Ideally, reactive tapes should be removable before curing, if necessary, in a substantially residue-free manner—for example, if the tape is misapplied. However, the characteristics of curable adhesives, dominated by a high mass fraction of reactive resins, often result in insufficient cohesion within the curable adhesive. Therefore, in many cases, instead of ideal adhesive failure on the substrate, cohesive failure occurs, leaving adhesive residue on the substrate.

[0008] Based on the above opinions, there has been ongoing interest in improving the processing quality of curable adhesives in the field of adhesive technology, with a particular objective of improving die-cutting properties and increasing cohesion in the material.

[0009] However, in many cases, known techniques for increasing cohesion and / or reducing the viscosity of curable adhesives compromise the post-processing quality of reactive tapes. This is because it also adversely affects the desired adaptation behavior in the application (i.e., the adaptation of the curable adhesive in the reactive tape to the structure of the substrate, especially in cases of rough substrate surfaces), and therefore, the peel adhesion achieved after curing may not meet specified requirements due to insufficient contact with the substrate. Against this backdrop, in the field of curable adhesives, there is often an objective conflict between sufficient cohesion in the curable adhesive and its processing quality during tape manufacturing, and between the processing quality and adhesive properties of the resulting reactive tape.

[0010] Furthermore, in the case of known curable adhesives and corresponding reactive tapes in the prior art, the impact resistance is often considered insufficient, and therefore needs to be improved. Summary of the Invention

[0011] The main objective of this invention is to eliminate or at least reduce the disadvantages of the prior art described above.

[0012] More specifically, the object of the present invention is to specify a curable adhesive in which the aforementioned conflict between high cohesiveness and good processing quality, particularly good die-cutting properties of the adhesive, and between the processing quality of reactive tapes and achievable peel adhesion, is optimally resolved.

[0013] Therefore, the object of the present invention is to specify a curable adhesive that, despite having a high mass fraction of reactive resin, still exhibits sufficient cohesive strength to achieve a basic adhesive failure upon separation from the substrate in subsequent use.

[0014] The object of the present invention is to specify a curable adhesive that has favorable adaptability and should achieve excellent peel adhesion after curing, even on substrates with rough surfaces.

[0015] Another object of the present invention is that the specified curable adhesive should have excellent impact resistance in the cured state.

[0016] In this context, a further objective of the present invention is to specify pressure-sensitive adhesives that can ideally be manufactured using as many starting materials and methods as possible already employed in the field of adhesive technology, in order to achieve time-efficient and cost-effective manufacturing.

[0017] A further objective of this invention is to provide advantageous reactive tapes and pressure-sensitive tapes.

[0018] Furthermore, a secondary objective of the present invention is to provide the use of a specified curable adhesive or reactive tape for bonding two or more components, and a method for manufacturing such a curable adhesive.

[0019] The inventors of this invention have now discovered that the above-mentioned objective can be surprisingly achieved if a relatively large amount of a (meth)acrylate block copolymer of the general formula ABA (where blocks A and B are specifically selected as defined in the claims) is used in a curable adhesive employing a specific mixture of liquid epoxy compound and solid or high-viscosity epoxy compound as a reactive resin.

[0020] Therefore, the above-mentioned objective is achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention will become apparent from the dependent claims and the following observations.

[0021] The preferred embodiments specified below combine features of particularly preferred embodiments with features of other preferred embodiments specified below. Therefore, combinations of two or more embodiments specified below as particularly preferred are particularly preferred. Also preferred are embodiments in which features of embodiments specified to some extent are combined with one or more additional features of other embodiments specified to some extent as preferred. The characteristics of preferred tapes, uses, and methods are clear from the features of preferred curable adhesives.

[0022] Therefore, for an element, such as a (meth)acrylate block copolymer or an epoxy compound, not only is the specific amount or fraction of the element disclosed below, but also the preferred embodiment of the element is disclosed, and particularly the specific amount or fraction of the element having its preferred embodiment is disclosed. It is also disclosed that, in the case of a corresponding specific total amount or fraction of the element, at least a portion of the element may be a preferred embodiment, and in particular, elements of preferred embodiments may conversely be present in a specific amount or fraction within a specific total amount or fraction. Detailed Implementation

[0023] This invention relates to a curable adhesive, which, based on its mass, comprises:

[0024] a) Combined (total) mass fraction of 25% or higher of one or more ABA-structured (meth)acrylate block copolymers.

[0025] The A blocks independently represent poly(meth)acrylates with a glass transition temperature (Tg) of 50°C or higher, which can be prepared by polymerization of A monomer components comprising A monomers.

[0026] The B block represents a poly(meth)acrylate with a glass transition temperature Tg of less than 50°C, which can be prepared by polymerization of a B monomer component containing a B monomer.

[0027] b) Combining one or more polymerizable first epoxy compounds E1 at a mass fraction of 5% or higher, wherein the first epoxy compound E1 is a solid at 25°C or a high-viscosity substance having a dynamic viscosity of 50 Pa·s or higher; and

[0028] c) Combining one or more polymerizable second epoxy compounds E2 at a mass fraction of 5% or higher, wherein the second epoxy compound E2 is a liquid with a dynamic viscosity of 40 Pa·s or lower at 25°C.

[0029] The Hansen solubility parameter of the monomer unit from monomer A in block A is <δ p The polar component of the amount-of-substance-weighted (<δ) p >(A)) at 9.0 to 11.0 MPa 0.5 Within the range, and

[0030] The Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ. p > The molar weighted polar component (polar part) (<δ p >(B)) less than 9.0 MPa 0.5 .

[0031] Additives E1 and E2, used purely as labels, are hereby used to more clearly and easily distinguish the two epoxy compounds used in this invention.

[0032] The components defined above are all referred to as "one or more" in their respective contexts, consistent with the understanding of those skilled in the art. In this context, according to industry convention, the designation "one or more" relates to the chemical properties of the compounds in question, rather than their amount. For example, a curable adhesive may include only 3',4'-epoxycyclohexanecarboxylic acid epoxycyclohexylmethyl ester (dynamic viscosity of approximately 0.25 Pa·s at 25°C) as the second epoxy compound E2, which would imply that the curable adhesive incorporates the multiplicity of the relevant molecules.

[0033] Mass fractions are typically reported as a combined mass fraction of one, two, or more components, thus indicating that the combined mass fractions of the respective components conform to the corresponding standards, wherein the mass of the curable adhesive is a reference system for each of the (meth)acrylate block copolymer, the first epoxy compound E1, and the second epoxy compound E2.

[0034] The curable adhesive of this invention is curable. Due to its curing capability, the curable adhesive can function as a structural adhesive after curing. According to DIN EN 923:2006-01, a structural adhesive is defined as an adhesive that forms an adhesive bond that maintains a fixed strength in a structure for a predetermined, relatively long period of time (according to ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). Therefore, they are adhesives for chemically and physically strong bonds that contribute to the reinforcement of the tape in the cured state.

[0035] Block copolymers, both general and specific (meth)acrylate block copolymers, are well known in the art, particularly including block copolymers having an ABA structure. The manufacture of (meth)acrylate block copolymers with, for example, ABA structures is described in the art; for the (meth)acrylate block copolymers to be used in this case, block copolymerization methods known in the art can also be employed in principle. For example, illustrative overviews of block copolymers suitable for use in various adhesives can be found in documents such as US 2011003947 A1, US 20080200589 A1, US 2007078236 A1, US 2007078236A1, US 2012196952A1, US 2016032157A1, US2008146747A1, and US 2016230054 A1.

[0036] In the ABA-structured (meth)acrylate block copolymers used in this invention, block A has a higher glass transition temperature than block B. Block A is sometimes referred to as a hard block, and block B as a soft block, according to terminology sometimes used also for other block copolymers. However, it should be noted accordingly that, for the (meth)acrylate block copolymers identified by the inventors, the B block can also provide a fundamentally higher glass transition temperature compared to some soft blocks known in the prior art, according to the inventors' estimates. It is understood by those skilled in the art that the glass transition temperatures of blocks A and B are not determined by the (meth)acrylate block copolymer itself, but by the individual (co)polymerization of each block.

[0037] For the purposes of this invention, the glass transition temperature of the polymer blocks in a polymer or block copolymer is determined by dynamic scanning calorimetry (DSC), as described in DIN EN ISO 11357. To perform this determination, approximately 5 mg of untreated polymer sample is weighed into an aluminum crucible (25 μL volume) and sealed with a perforated lid. For the measurement, a Netzsch DSC 204F1 is used. For inertization, the operation is performed under nitrogen. The sample is first cooled to -150°C, then heated to +150°C at a heating rate of 10 K / min, and then cooled again to -150°C. A subsequent second heating curve is run again at 10 K / min, and the change in heat capacity is recorded. The glass transition is identified as steps on the thermogram. Determining the glass transition temperature by DSC measurement is readily available to those skilled in the art, as described in more detail, for example, in EP 2832811 A1.

[0038] The two A blocks of a (meth)acrylate block copolymer are characterized by a common standard of glass transition temperature and a common possibility of being manufactured from the same monomer A. Those skilled in the art will understand that, in terms of their manufacturing properties, the A blocks have a high degree of similarity, but not necessarily identicalness, due to the nature of the polymerization methods used in their manufacture, particularly when two or more different monomers A are used. Similar to the A and B blocks, the (meth)acrylate block copolymer itself is also like this, because those skilled in the art of polymer materials will designate such block copolymers—in terms of the A and B blocks, which differ from each other only in the range of manufacturing-related variations—as common materials, namely, (meth)acrylate block copolymers.

[0039] It is very useful, according to the understanding of those skilled in the art and customary practice in the field, to define polymeric and oligomer compounds, such as A-block and B-block compounds, by means of the manufacturing process and / or the starting materials used in their manufacture, which would otherwise be impossible to provide a reasonable definition for the corresponding materials.

[0040] In the curable adhesives of the present invention, (meth)acrylate block copolymers composed of poly(meth)acrylate blocks are employed. Therefore, these (meth)acrylate block copolymers are at least partially composed of structural units derived from (meth)acrylate monomers—the term "(meth)acrylate" is consistent with the understanding of those skilled in the art, encompassing both acrylates and methacrylates. Therefore, it is preferred that the (meth)acrylate block copolymers and the corresponding blocks are primarily or substantially entirely composed of (meth)acrylate monomers.

[0041] In the context of this invention, as understood by those skilled in the art, the term "poly(meth)acrylate" encompasses polyacrylates and polymethacrylates, as well as copolymers of these polymers. Poly(meth)acrylates may contain relatively small amounts of monomer units not derived from (meth)acrylates. Therefore, in the context of this invention, "poly(meth)acrylate" refers to a (co)polymer whose monomer base consists of 70% or more, preferably 90% or more, more preferably 98% or more by mass fraction of monomers selected from acrylic acid, methacrylic acid, acrylates, and methacrylates, based on the mass of the monomer base. The mass fraction of acrylates and / or methacrylates is preferably 50% or more, more preferably 70% or more. Poly(meth)acrylates are generally obtained by free radical polymerization of monomers based on acrylic acid and / or methacrylic acid, and optionally additional polymerizable monomers.

[0042] The production of this poly(meth)acrylate from its respective monomers can be carried out by conventional methods, particularly by conventional free radical polymerization or controlled free radical polymerization—such as anionic polymerization or RAFT-, NMRP or ATRP polymerization.

[0043] Polymers and / or oligomers can be manufactured by copolymerizing monomer components using conventional polymerization initiators and optionally chain transfer agents; polymerization can be carried out at conventional temperatures, for example in bulk, in emulsions such as in water or liquid hydrocarbons, or in solution. Poly(meth)acrylates are preferably manufactured by polymerization in a solvent, more preferably in a solvent having a boiling temperature in the range of 50 to 150°C, more preferably in the range of 60 to 120°C, using a conventional amount of polymerization initiator; the polymerization initiator is generally added to the monomer composition in fractions of about 0.01 to 5%, more preferably 0.1 to 2%, based on the mass of the monomer component.

[0044] Suitable polymerization initiators are, for example, free radical sources such as peroxides, hydroperoxides, and azo compounds, such as benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-tert-butyl peroxide, cyclohexylsulfonylacetyl peroxide, diisopropyl percarbonate, tert-butyl peroctanoate, or benzylpinacol. Particularly preferred free radical polymerization initiators are 2,2'-azobis(2-methylbutyronitrile) or 2,2'-azobis(2,4-dimethylpentanonitrile). Suitable solvents particularly include alcohols such as methanol, ethanol, n-propanol and isopropanol, n-butanol and isobutanol, preferably isopropanol and / or isobutanol, and hydrocarbons such as toluene, especially benzenes (volatile oils) having a boiling temperature in the range of 60 to 120°C. Ketones, such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and esters, such as ethyl acetate, and mixtures of these solvents can be used in particular.

[0045] The (meth)acrylate block copolymers in the curable adhesives used in this invention have a specific polarity difference between the A-block and the B-block, which, within the scope of this invention, is conventionally expressed by the Hansen solubility parameter <δ of the monomer units present in the A- and B-blocks. p The substance is represented by a weighted polar component; for block A, these components must be within a relatively narrow range, yet higher than the corresponding values ​​for block B.

[0046] The resulting (meth)acrylate block copolymers with corresponding polar profiles are well known to those skilled in the art as individual components, and in particular the so-called MMA-BA-MMA block copolymers, i.e. ABA block copolymers having a polymethyl methacrylate A block and a polybutyl acrylate B block, are commercially available and used in many fields.

[0047] In addition, other representatives of these (meth)acrylate block copolymers are also commercially available, such as MMA-BA / 2-EHA-MMA block copolymer, which is an ABA block copolymer having an A block of polymethyl methacrylate and a B block of a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate.

[0048] In the field of adhesive technology, (meth)acrylate block copolymers with corresponding polar characteristics, particularly MMA-BA-MMA block copolymers, have sometimes been used as additives in adhesives, where they typically function as so-called impact modifiers. Despite their potentially beneficial effect on impact strength, the addition of these components is generally not considered advantageous to key technical adhesive properties, and in some cases, is actually detrimental. Therefore, the mass fraction of these impact modifiers is often minimized and typically not exceeds 20%. Particularly in curable adhesives (which, due to their nature, comprise a large fraction of polymerizable compounds, particularly liquid polymerizable compounds), the use of large quantities of (meth)acrylate block copolymers with corresponding polar characteristics is often accompanied by a lack of sufficient cohesive strength and / or a lack of satisfactory adaptive behavior in the adhesive.

[0049] This situation has always been considered unfavorable, especially considering the fundamentally positive properties of these (meth)acrylate block copolymers with corresponding polar characteristics. Therefore, it is particularly surprising, as the inventors now recognize, that adhesives with good cohesive strength and favorable adaptive behavior can be obtained by using specific reactive resins comprising a combination of solid or high-viscosity epoxy compounds and liquid epoxy compounds. These adhesives, surprisingly, can even be implemented as pressure-sensitive adhesives due to their favorable cohesive strength—unexpectedly, even with high mass fractions of these (meth)acrylate block copolymers, the resulting adhesives are curable. It is also particularly surprising that large mass fractions of the corresponding (meth)acrylate block copolymers do not have an adverse effect in this case; on the contrary, favorable behavior arises from the objective conflict between cohesive strength and adaptive behavior, which synergistically combines with favorable impact resistance. The inventors have found here that the implementation, particularly of the polymer as the block copolymer, plays a crucial role, because the advantages observed when using statistically distributed polymers (which otherwise comprise the same monomers to construct the blocks in the same proportions), particularly those related to improved cohesive strength, are surprisingly not apparent. Therefore, it is surprising that excellent impact resistance can be achieved even without the use of polyols (as additives for open time), which are known to those skilled in the art for improving the impact properties of adhesives.

[0050] The following text clarifies the concept, background, and calculation method of the Hansen solubility parameter, and points out illustrative values ​​for monomers frequently used in the field of adhesive bonding.

[0051] One known description of solubility parameters in the literature is the use of a one-dimensional Hildebrand parameter (δ). However, these one-dimensional δ values ​​are subject to error, which is typically large in the case of polar compounds such as (meth)acrylates, or compounds capable of forming hydrogen bonds such as acrylic acid. Because the one-dimensional Hildebrand solubility parameter model thus found only limited applications, it was further developed by Hansen (Hansen Solubility Parameters: A User's Handbook, 2nd Edition; Charles M. Hansen; 2007 CRC Press; ISBN 9780849372483).

[0052] The Hansen solubility parameters widely used today are three-dimensional solubility parameters, which are frequently referenced, particularly in the field of adhesive formulation, as disclosed in, for example, WO 2019 / 106194 A1 or WO 2019 / 229150 A1. They are determined by the dispersion component (δ... d ), the component originating from polar interactions (δ) p ) and the hydrogen bond component (δH The composition is as follows. The relationship between the Hildebrand parameter δ and the Hansen solubility parameter is as follows:

[0053] δ 2 =δ d 2 +δ p 2 +δ H 2 .

[0054] δ d δ p and δ H The specific parameters of poly(meth)acrylate cannot be determined directly by experimental means, but can be calculated via an incremental system. The usual method, and the method used in the context of this invention, is Stefanis / Panayiotou’s (“Prediction of Hansen Solubility Parameters with a New Group-Contribution Method”; Int. J. Thermophys. (2008) 29: 568-585; Emmanuel Stefanis, Costas Panayiotou).

[0055] According to the Stefanis / Panayiotou group contribution method, the Hansen solubility parameter of the polymer is determined by calculating the solubility parameters of those units in the polymer that can be attributed to individual monomers, in other words, those repeating units in the polymer chain (i.e., where appropriate, without monomeric polymerizable double bonds, but taking into account covalent s-bonding as present in the polymer chain). In this scheme, for each group in the building block, there exists a parameter for the dispersion component (δ). d ), polar interaction component (δ) p ) and hydrogen bonding component (δ H The specific values ​​listed are shown in the table; see “Prediction of Hansen Solubility Parameters with a New Group-Contribution Method”; Int. J. Thermophys. (2008), Tables 3 to 6, pp. 578-582.

[0056] For example, polyacrylic acid contains repeating units:

[0057] -[-CH2-CHCOOH-] n -

[0058] According to the Stefanis / Panayiotou incremental system, the Hansen solubility parameters for the constructed blocks discussed (one CH2 group, one CH group, and one COOH group) are δ. d =17.7, δ p =8.6 and δ H =11.1.

[0059] For example, polybutyl acrylate contains repeating units having four CH2 groups, one CH group, one COO group, and one CH3 group:

[0060] -[-CH2-CHCOO(CH2)3CH3-] n -

[0061] The Hansen solubility parameter for the constructed blocks discussed is δ. d =17.1, δ p =8.6 and δ H =6.5.

[0062] In Stefanis and Panayiotou's group contribution method, more complex organic molecules are described using so-called first-order and second-order groups. The first-order group (n) is a model of the basic molecular structure. The second-order group (m) takes into account the conjugation of the first-order group and improves the accuracy of the method.

[0063] For this invention, based on the inventors' understanding, only the polar component δp needs to be considered. These components can be calculated using the following formula:

[0064]

[0065] Tables 1 and 2 show example calculations for two illustrative compounds (3',4'-epoxycyclohexanecarboxylic acid methyl epoxycyclohexyl ester and 2-hydroxy-3-phenoxypropyl acrylate).

[0066] Table 1—Calculation of the polar component δp of the Hansen solubility parameter for 3',4'-epoxycyclohexanecarboxylic acid epoxycyclohexylmethyl ester.

[0067] Table 2—Calculation of the polar component δp of the Hansen solubility parameter for 2-hydroxy-3-phenoxypropyl acrylate.

[0068]

[0069]

[0070] Those skilled in the art will understand that, in the context of this invention, the Hansen solubility parameters of blocks A and B are calculated by evaluating the monomer units, i.e., repeating units in the polymer chain, and therefore the CH2=CH- group is considered to be a -CH2-CH- group relative to the monomers used for preparation, i.e., monomers A and B.

[0071] According to the calculation method, when preparing copolymers using a mixture of monomer A and / or monomer B, the average value of the polar components of the Hansen solubility parameter is formed, where the contribution of each monomer is weighted by its molar fraction. Therefore, this invention considers the molar-weighted polar component of the Hansen solubility parameter <δ p As mentioned above, it was calculated based on Stefanis and Panayiotou's group contribution method.

[0072] Table 3 reproduces, illustratively, the polar components of the Hansen solubility parameters for the selected monomers, which are highly relevant as fundamental building blocks of polymers in the field of curable adhesives.

[0073] Table 3—Polar components δ of Hansen solubility parameters for illustrative monomers p (rounding).

[0074]

[0075]

[0076] According to the inventors' assessment, when distinguishing between A-blocks and B-blocks in the context of this invention, the main focus is on their different polarities, evaluated as described above. However, the glass transition temperature is also of supplementary importance; according to the inventors' understanding, the limit can be considered, as defined above, at 50°C. However, according to the inventors' assessment, it is advantageous for the physicochemical properties achieved in the curable adhesive if the A-blocks used include hard blocks with relatively high glass transition temperatures and the soft blocks used include B-blocks with relatively low glass transition temperatures. A preferred curable adhesive of the invention is one in which the A-blocks are independently poly(meth)acrylates having a glass transition temperature Tg greater than 60°C, preferably greater than 70°C, more preferably greater than 80°C, and / or where the B-blocks are poly(meth)acrylates having a glass transition temperature Tg less than 40°C, preferably less than 30°C, more preferably less than 20°C.

[0077] As explained above, it is not absolutely necessary, and given the typical differences in polymer preparation, it is not expected that the A blocks in each (meth)acrylate block copolymer be identical. Thus, the above definition ultimately defines only the minimum or maximum glass transition temperature and the chemical properties of the monomer units in each (co)polymer. However, those skilled in the art will understand that, particularly in manufacturing and in terms of the uniformity of the physicochemical properties of the curable adhesives made therefrom, preferred (meth)acrylate block copolymers are those in which the A blocks are as similar as possible; it is considered particularly advantageous if the A blocks are prepared such that they are substantially identical or exhibit low polydispersity within the typical range of differences in polymer chemistry. It is understood by those skilled in the art that if the A blocks are prepared from the same A monomer component under the same polymerization conditions, particularly effective (meth)acrylate block copolymers will be produced. In this context, the preferred curable adhesive of the present invention is a poly(meth)acrylate in which the two A blocks are glass transition temperatures that differ by less than 5°C, preferably less than 3°C, more preferably less than 1°C, wherein the poly(meth)acrylate can be prepared by polymerization of the same A monomer component from the A monomer, and wherein the A blocks are preferably substantially the same.

[0078] While the use of copolymers in blocks A and B is conceivable in principle, and it is also possible to have monomers containing at least a small fraction of non-meth)acrylate-based monomers, according to the inventors' assessment, in most cases it is preferred that either block A or block B be as predominantly (meth)acrylate-based as possible, and therefore very preferably composed primarily of one type of (meth)acrylate-based monomer. Therefore, the curable adhesive of the present invention is preferably considered as follows, wherein monomer A comprises one or more monomers, preferably one monomer selected from (meth)acrylate monomers and (meth)acrylic acid, preferably methacrylate monomers, wherein monomer A preferably comprises 90% or more, more preferably 95% or more, very preferably 99% or more, and most preferably substantially entirely of these monomers, based on the combined mass of monomer A. Also preferred are the curable adhesives of the present invention described below, wherein monomer B comprises one or more monomers, preferably one monomer selected from (meth)acrylate monomers and (meth)acrylic acid, more preferably acrylate monomers and acrylic acid, more preferably acrylate monomers, wherein monomer B is preferably composed of 90% or more, more preferably 95% or more, very preferably 99% or more, and most preferably substantially entirely of these monomers, based on the combined mass of monomer B. Therefore, it is particularly preferred that the above-described characteristics of monomers A and B are determined in the same manner and / or with the same degree of preference, and especially preferred that each monomer is formed substantially entirely of the corresponding monomer of the specified type in its respective case. In this case, the corresponding (meth)acrylate block copolymer not only produces excellent cohesion in the curable adhesive, but can also be manufactured particularly easily, reliably, and repeatedly, thus particularly reducing storage costs and complexity, and making it easier to establish stable product quality.

[0079] Based on the above observations, the inventors have successfully identified monomers particularly suitable for monomers A and B, and thus determined the chemical properties of blocks A and B. According to the inventors' assessment, these monomers result in the particularly high-performance curable adhesive of the present invention, wherein the above observations are correspondingly applicable to the formation of blocks A and B as substantially pure polymers. In practice, the curable adhesive of the present invention is preferably considered as follows, wherein the monomer A component comprises one or more monomers selected from methyl methacrylate, ethyl acrylate, methyl acrylate, 2-phenoxydiethylene glycol acrylate, and tert-butyl acrylate, preferably composed of methyl methacrylate and ethyl acrylate, more preferably methyl methacrylate, and / or wherein the monomer A component comprises methyl methacrylate in a mass fraction of 80% or higher, preferably 90% or higher, more preferably 95% or higher, very preferably 98% or higher, particularly preferably 99% or higher, more preferably substantially 100%, based on the mass of the monomer A component, and / or wherein blocks A independently represent polymethyl methacrylate. Additionally or alternatively, the curable adhesive of the present invention is preferably considered as follows, wherein the B monomer component comprises one or more B monomers selected from n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isobornyl acrylate, 2-phenoxyethyl acrylate, propylheptaacrylate, and acrylic acid, preferably n-butyl acrylate, 2-phenoxyethyl acrylate, and 2-ethylhexyl acrylate, more preferably n-butyl acrylate and 2-ethylhexyl acrylate, very preferably n-butyl acrylate, and / or the B monomer component comprises 80% or higher, preferably 90% or higher, more preferably 95% or higher, very preferably 98% or higher, particularly preferably 99% or higher, more preferably substantially 100% by mass fraction of n-butyl acrylate and / or 2-ethylhexyl acrylate, preferably n-butyl acrylate, based on the mass of the B monomer component, and / or wherein the B block is polybutyl acrylate.

[0080] (Meth)acrylate block copolymers, number average molecular weight M n Preferably in the range of 20,000 to 1,000,000 g / mol, more preferably in the range of 90,000 to 500,000 g / mol, and most preferably in the range of 105,000 to 150,000 g / mol. The weight average molecular weight M of the (meth)acrylate block copolymer. w Preferably, the concentration is in the range of 20,000 to 1,000,000 g / mol; more preferably, in the range of 100,000 to 500,000 g / mol; and most preferably, in the range of 115,000 to 150,000 g / mol. The inventors unexpectedly determined that impact resistance can be improved by using relatively high molecular weight (meth)acrylate block copolymers in the adhesives of the present invention. The number-average molecular weight M is considered very preferably... nWithin the range of 105,000 to 150,000 g / mol and with a weight-average molecular weight M w (Meth)acrylate block copolymers in the range of 115,000 to 150,000 g / mol. In this case, (meth)acrylate block copolymers having less than 20% A block or poly(meth)acrylate fraction are particularly advantageous.

[0081] These are related to the number-average molar mass M n and weight average molecular weight M w The statement is based on a determination performed by gel permeation chromatography (GPC). 100 μL of clarified, filtered sample (sample concentration 4 g / L) was analyzed. The eluent used was tetrahydrofuran containing 0.1 vol% trifluoroacetic acid. The measurement was performed at 25 °C. The pre-column used was a PSS-SDV type column, 5 μm. 8.0mm x 50mm (The data here and below are in the following order: type, particle size, porosity, inner diameter * length; Separation was performed using the following combination: PSS-SDV column, 5 μm. as well as and Each column is 8.0 mm x 300 mm (from Polymer Standards Service). Alternatively, two PLgel 5 μm MIXDED-D columns from Agilent can be used. Assays were performed using a Shodex RI71 differential refractometer at a flow rate of 1.0 ml / min. Calibration was performed using PS standards (polyethylene calibration).

[0082] As part of the development of this invention, the inventors have successfully determined particularly suitable ranges for the absolute polarity components of the Hansen solubility parameters of monomers A and B, using which particularly high-performance curable adhesives can be achieved; in particular, it is also considered advantageous if the polarity of block B is not significantly different from that of block A. According to the inventors' assessment, the correspondingly determined ranges are particularly useful for the rapid and reliable design of new (meth)acrylate block copolymers for their respective applications, since the corresponding polarity components of the Hansen solubility parameters can be looked up in tables, for example, in the context of this disclosure. A preliminary preferred curable adhesive of the invention is one in which the Hansen solubility parameter of the monomer unit from monomer A in block A is <δ p The polar component of the substance weighted by the amount of substance (<δ) p >(A)) at 9.0 to 11.0 MPa 0.5 Within the range, preferably between 9.2 and 9.5 MPa0.5 Within the range, more preferably between 9.3 and 9.4 MPa 0.5 Within the range. Furthermore, additionally or alternatively, the curable adhesive of the present invention is preferably considered first, wherein the Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ. p The polar component of the substance weighted by the amount of substance (<δ) p >(B)) at 6.0 to 8.0 MPa 0.5 Within the range, preferably between 6.5 and 8.8 MPa 0.5 Within the range, more preferably between 7.0 and 8.7 MPa 0.5 Within the range, and / or the molar-weighted polar component of the Hansen solubility parameter <δp> of the monomeric unit from monomer B in the B block (<δp>(B)) is greater than 6.0 MPa. 0.5 Preferably, it exceeds 7.0 MPa 0.5 More preferably exceeding 8.0 MPa 0.5 According to the inventors' assessment, it is particularly advantageous that the polarity difference is within a defined, relatively narrow range. Therefore, the preferred curable adhesive of the present invention is one where the difference is <δ p >(A)-<δ p (B) At 0.2 to 2.0 MPa 0.5 Within the range, preferably from 0.4 to 1.5 MPa 0.5 Within the range, more preferably from 0.6 to 1.0 MPa 0.5 That kind of range.

[0083] The curable adhesive of the present invention, in addition to (meth)acrylate block copolymers, includes at least two different polymerizable epoxy compounds, namely at least one first epoxy compound E1 and at least one second epoxy compound E2, and optionally additional polymerizable compounds. This portion of the curable adhesive, formed together by these compounds, is often referred to by those skilled in the art as a reactive resin.

[0084] In this context, and as understood by those skilled in the art, the expression "polymerizable" refers to the ability of these compounds to potentially undergo a polymerization reaction upon appropriate activation. With regard to polymerizable epoxides, polymerizability is achieved, for example, by epoxide groups. Polymerizability can also arise from the fact that two or more polymerizable compounds exist, which can be co-polymerized, for example, through addition polymerization or condensation polymerization. An illustrative example in this case is a combination of an epoxide with dicyandiamide and / or imidazole.

[0085] As understood by those skilled in the art, epoxy compounds are compounds having at least one ethylene oxide group. They can be aromatic or aliphatic, more particularly alicyclic. Polymerizable epoxy compounds can include not only monomers but also oligomeric or polymeric epoxy compounds. Polymerizable epoxy compounds typically have at least two epoxide groups per molecule on average, preferably more than two epoxide groups per molecule. Accordingly, the curable adhesive of the present invention is preferred, wherein one or two or more first epoxy compounds E1 and / or one or two or more second epoxide compounds E2, preferably first epoxide compounds E1 and second epoxide compounds E2, are selected from epoxy compounds having two or more epoxide groups, preferably two epoxide groups.

[0086] Oligomeric or polymeric epoxy compounds primarily include linear polymers with terminal epoxide groups (such as diglycidyl ethers of polyoxyalkylene glycols), polymers with skeletal ethylene oxide units (such as polybutadiene polyepoxides), and polymers with epoxide side groups (such as glycidyl methacrylate polymers or copolymers). The molecular weight of such epoxy compounds can be from 58 to approximately 100,000 g / mol or greater, where molecular weight is an important parameter for adjusting dynamic viscosity. Illustrative polymerizable epoxy compounds include cyclohexane esters of epoxy, such as 4-epoxycyclohexanecarboxylic acid methyl ester, 3,4-epoxy-2-methylcyclohexanecarboxylic acid methyl ester, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid ester. Further examples of polymerizable epoxy compounds are disclosed, for example, in US 3,117,099 A. Other polymerizable epoxy compounds particularly useful in the application of this invention include glycidyl ether monomers, such as those disclosed in US 3,018,262. Examples include the reaction of polyhydroxyphenols with an excess of a chlorohydrin, such as epichlorohydrin, to obtain glycidyl ethers of polyhydroxyphenols (e.g., diglycidyl ethers of 2,2-bis(2,3-epoxypropoxyphenol)propane). More particularly, diglycidyl ethers of bisphenols, such as bisphenol A (4,4′-(propane-2,2-diyl)diol) and bisphenol F (bis(4-hydroxyphenyl)methane). These reaction products are commercially available in various molecular weights and physical states (e.g., so-called type I to type X BADGE resins). Typical examples of liquid bisphenol A diglycidyl ethers are Epikote 828, DER331, and Epon 828. Typical solid BADGE resins are Araldite GT 6071, GT7072, Epon 1001, and DER662. Other reaction products of phenol with epichlorohydrin are phenol and cresol phenolic resins (novolac resins), such as Epiclon products or Araldite EPN and ECN products (e.g., ECN1273).

[0087] Based on the above observations, the inventors have successfully identified polymerizable epoxy compounds that achieve particularly good results in resolving the conflict between cohesive and adaptive behaviors. Accordingly, the following durable adhesive of the invention is preferred, wherein one or more first epoxy compounds E1 and / or one or more second epoxy compounds E2, preferably first epoxy compounds E1 and second epoxy compounds E2, are selected from epoxy compounds having at least one cycloaliphatic group, more particularly cyclohexyl or dicyclopentadiene group, and / or wherein the curable adhesive comprises at least one first epoxy compound E1 and / or at least one second epoxy compound E2, preferably at least one first epoxy compound E1 and at least one second epoxy compound E2, selected from epoxy compounds having at least one cycloaliphatic group, more particularly cyclohexyl or dicyclopentadiene group. Additionally or alternatively, the curable adhesive of the present invention is preferably as follows, wherein one or more first epoxy compounds E1 and / or one or more second epoxy compounds E2, preferably the first epoxy compounds E1 and the second epoxy compounds E2, are selected from bisphenol A diglycidyl ether and bisphenol F diglycidyl ether, preferably bisphenol A diglycidyl ether, and / or wherein the curable adhesive comprises at least one first epoxy compound E1 and / or at least one second epoxy compound E2, preferably at least one first epoxy compound E1 and at least one second epoxy compound E2, which are selected from bisphenol A diglycidyl ether and bisphenol F diglycidyl ether, preferably bisphenol A diglycidyl ether.

[0088] Therefore, it is particularly preferred that the two aforementioned characteristics of epoxy compounds are combined simply by obtaining an epoxy compound having at least one cyclic aliphatic group through hydrogenation of the corresponding bisphenol compound, because curable adhesives that achieve the above-mentioned objectives can be obtained particularly well, especially when at least one such epoxy compound is used, particularly as a liquid epoxy compound. Here, the inventors have unexpectedly determined that these types of hydrogenated epoxy compounds possess relatively high bond strength. Therefore, the curable adhesive of the present invention is particularly preferred as follows, wherein one or two or more first epoxy compounds E1 and / or one or two or more second epoxy compounds E2, preferably the second epoxy compound E2, are selected from hydrogenated bisphenol A diglycidyl ether and hydrogenated bisphenol F diglycidyl ether, preferably hydrogenated bisphenol A diglycidyl ether, and / or wherein the curable adhesive comprises at least one first epoxy compound E1 and / or at least one second epoxy compound E2, preferably at least one second epoxy compound E2, which is selected from hydrogenated bisphenol A diglycidyl ether and hydrogenated bisphenol F diglycidyl ether, preferably hydrogenated bisphenol A diglycidyl ether.

[0089] The first polymerizable epoxy compound E1 is selected from compounds that are solid or high-viscosity substances at 25°C, the latter being defined in the context of this invention by the lower limit of dynamic viscosity at 25°C. Those skilled in the art will understand that the distinction between solid and correspondingly high-viscosity substances is useful in practical applications, since the viscosity of a solid is inherently a multiple of the aforementioned dynamic viscosity value, but in practice it is often hardly worth determining, and therefore it is sufficient to determine that it is a solid. Advantageously, by the chosen definition, it is not necessary to distinguish whether a substance is solid at 25°C or a high-viscosity substance with a corresponding dynamic viscosity. Conversely, the second polymerizable epoxy compound E2 is a low-viscosity liquid, which, in the context of this invention, is defined by the upper limit of dynamic viscosity at 25°C. For the purposes of this invention, this dynamic viscosity is based on DIN 53019-1 2008 at 25°C and using 1s… -1 The shear rate was determined.

[0090] The inventors have recognized that it is particularly advantageous if the difference in viscosity between the polymerizable epoxy compounds is relatively large. Therefore, the curable adhesive of the present invention is preferably considered as follows: at least one, preferably all, of the first epoxy compound E1 has a dynamic viscosity of 100 Pas or higher, preferably 150 Pas or higher at 25°C; and / or at least one, preferably all, of the second epoxy compound E2 has a dynamic viscosity of 30 Pas or lower, preferably 20 Pas or lower, and very preferably 10 Pas or lower at 25°C. In this case, it is particularly preferred to combine the respective preferred ranges with each other.

[0091] As can also be seen from the above observations, considering the significant differences in dynamic viscosity, the use of a solid epoxy compound as the first epoxy compound E1 is particularly preferred. Therefore, the following curable adhesive of the present invention is particularly preferred, wherein one or two or more of the first epoxy compounds E1 are solids having a softening temperature of 45°C or higher, and / or at least one, preferably all, of the first epoxy compounds E1 are solids having a softening temperature of 45°C or higher.

[0092] One advantage of the curable adhesives of the present invention is the great flexibility in the selection of catalysts, particularly regarding the nature of the curing process. Those skilled in the art can tailor the catalyst system used for curing according to application requirements and the polymerizable compound employed. Therefore, for most relevant applications, it would be advantageous in practice if the curable adhesives of the present invention further comprised one or more initiators.

[0093] Considering future processing performance, according to the inventors' evaluation, it is particularly advantageous to use radiation crosslinking and / or thermal crosslinking systems, with radiation activation offering significant advantages in terms of processing. Accordingly, the curable adhesive of the present invention is preferably considered as follows: the curable adhesive is a radiation-curing and / or thermal-curing adhesive, and / or the curable adhesive can be cured by polymerization of a first epoxy compound E1 and a second epoxy compound E2, preferably by radiation activation and / or thermal activation.

[0094] Therefore, the curable adhesive of the present invention is preferred in principle as follows, wherein the curable adhesive comprises one or more initiators, preferably in a combined mass fraction in the range of 0.05 to 4%, more preferably in the range of 0.1 to 3%, based on the mass of the curable adhesive, and / or one or more of the initiators are preferably selected from radiation-activated initiators and thermally activated initiators.

[0095] In the current envisioned use of polymerizable epoxy compounds in reactive resins, polymerization is preferably carried out via cationic polymerization. Therefore, the following curable adhesive of the present invention is preferred, wherein one or more initiators are selected from radiation-activated initiators and thermally activated initiators. Therefore, the following curable adhesive of the present invention is also preferred, wherein one or more initiators are selected from initiators used for cationic polymerization. Therefore, the following curable adhesive of the present invention is particularly preferred in combination, wherein one or more initiators are selected from radiation-activated initiators used for cationic polymerization, an example being triarylsulfonium hexafluoroantimonyate.

[0096] For thermosetting, so-called curing agents and accelerators are typically used. In the context of this invention, the term "curing agent" as used herein, according to DIN 55945:1999-07, refers to a compound added to a polymerizable compound to achieve crosslinking of the curable adhesive—as an adhesive. Curing agents cause chemical crosslinking, and correspondingly, in the presence of a curing agent, accelerators increase the reaction rate in the curing reaction and / or the activation rate of epoxy resin curing. The curing reaction can be fundamentally determined as a peak value in dynamic scanning calorimetry (DSC). Compounds understood as accelerators are specifically those whose addition shifts the curing peak value of a particular curing agent towards lower temperatures. The collective term for curing agents and accelerators is also referred to by those skilled in the art as a curing agent.

[0097] The lists of substances that can be used as curing agents and accelerators overlap, with some individual representatives capable of performing both functions simultaneously in certain situations; therefore, the transition between curing agents and accelerators is generally fluid, where selecting a suitable curing agent and accelerator system is not particularly challenging for those skilled in the art. Compounds selected from, for example, dicyandiamide, imidazole, acid anhydrides, epoxide amine adducts, acyl hydrazides, and reaction products of diacids and polyfunctional amines can be used as curing agents and / or accelerators. Examples of reaction products of diacids and polyfunctional amines considered include the reaction product of phthalic acid and diethylenetriamine. Stoichiometric curing agents such as dicyandiamide are preferably used based on the amount of epoxide in the adhesive. Non-stoichiometric curing agents such as imidazole and epoxide amine adducts are typically used, for example, at a maximum fraction of 20%, based on the epoxide fraction.

[0098] Cationic UV-induced curing initiators useful for epoxy compounds are particularly sulfonium, iodonium, and metallocene-based systems. For examples of sulfonium-based cationic initiators, see the observations in US 6908722 B1.

[0099] Examples of anions used as counterions to the aforementioned cations include tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate, hexachloroantimonate, tetrapentafluorophenylborate, tetra(pentafluoromethylphenyl)borate, bis(trifluoromethanesulfonyl)amide, and tri(trifluoromethanesulfonyl)methyl compounds. Furthermore, chlorine, bromine, or iodide anions are conceivable, particularly for iodonium-based initiators, although initiators substantially free of chlorine and bromine are preferred. A high-performance example of such a system is, for instance, triphenylsulfonium hexafluoroantimonate. Other suitable initiators are disclosed in US 3729313A, US 3,741,769 A, US 4,250,053 A, US 4,394,403A, US 4,231,951 A, US 4,256,828 A, US 4,058,401 A, US 4,138,255 A and US 2010 / 063221A1.

[0100] Specific examples of usable sulfonium salts include triphenylsulfonium hexafluoroarsenate, triphenylsulfonium hexafluoroborate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetra(pentafluorobenzyl)borate, methyl diphenylsulfonium tetrafluoroborate, methyl diphenylsulfonium tetra(pentafluorobenzyl)borate, dimethylphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, diphenylnaphthylsulfonium hexafluoroarsenate, trimethylmethylsulfonium hexafluorophosphate, methoxyphenyl diphenylsulfonium hexafluoroantimonate, and 4-butoxyphenyl diphenylsulfonium tetrafluoroborate. 4-Chlorophenyl diphenylsulfonium hexafluoroantimonate, tris(4-phenoxyphenyl)sulfonium hexafluorophosphate, di(4-ethoxyphenyl)methylsulfonium hexafluoroarsenate, 4-acetylphenyl diphenylsulfonium tetrafluoroborate, 4-acetylphenyl diphenylsulfonium tetra(pentafluorobenzyl)borate, tris(4-thiomethoxyphenyl)sulfonium hexafluorophosphate, di(methoxysulfonylphenyl)methylsulfonium hexafluoroantimonate, di(methoxynaphthyl)methylsulfonium tetrafluoroborate, di(methoxynaphthyl)methylsulfonium tetra(pentafluorobenzyl)borate, di(methyl ester) (Phenyl)methylsulfonium hexafluorophosphate, (4-octyloxyphenyl)diphenylsulfonium tetra(3,5-bis(trifluoromethylphenyl)borate, tris[4-(4-acetylphenyl)thiophenyl]sulfonium tetra(pentafluorophenyl)borate, tris(dodecylphenyl)sulfonium tetra(3,5-bis(trifluoromethylphenyl)borate, 4-acetamidophenyl diphenylsulfonium tetrafluoroborate, 4-acetamidophenyl diphenylsulfonium tetra(pentafluorobenzyl)borate, dimethylnaphthylsulfonium hexafluorophosphate, trifluoromethyl diphenylsulfonium tetrafluoroborate, trifluoromethyl Diphenylsulfonium tetra(pentafluorobenzyl)borate, phenylmethylbenzylsulfonium hexafluorophosphate, 5-methylthiaanthraquinone hexafluorophosphate, 10-phenyl-9,9-dimethylthiaanthraquinone hexafluorophosphate, 10-phenyl-9-oxythiaanthraquinone tetrafluoroborate, 10-phenyl-9-oxythiaanthraquinone tetra(pentafluorobenzyl)borate, 5-methyl-10-oxythiaanthraquinone tetra(pentafluorobenzyl)borate, 5-methyl-10-oxythiaanthraquinone tetra(pentafluorobenzyl)borate and 5-methyl-10,10-dioxythiaanthraquinone hexafluorophosphate.

[0101] Specific examples of usable iodonium salts include diphenyliodonium tetrafluoroborate, di(4-methylphenyl)iodonium tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate, di(4-chlorophenyl)iodonium hexafluorophosphate, dinaphthyliodonium tetrafluoroborate, di(4-trifluoromethylphenyl)iodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, di(4-methylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, di(4-phenoxyphenyl)iodonium tetrafluoroborate, phenyl-2-thienyliodonium hexafluorophosphate, 3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, 2,2'-diphenyliodonium tetrafluoroborate, and di(2,4-dichlorophenyl)iodonium hexafluorophosphate. , bis(4-bromophenyl)iodonium hexafluorophosphate, bis(4-methoxyphenyl)iodonium hexafluorophosphate, bis(3-carboxyphenyl)iodonium hexafluorophosphate, bis(3-methoxycarbonylphenyl)iodonium hexafluorophosphate, bis(3-methoxysulfonylphenyl)iodonium hexafluorophosphate, bis(4-acetamidophenyl)iodonium hexafluorophosphate, bis(2-benzothiophene)iodonium hexafluorophosphate, diaryliodonium tritrifluoromethylsulfonylmethylate and diphenyliodonium hexafluoroantimonate, diaryliodonium tetra(pentafluorophenyl)borate such as diphenyliodonium tetra(pentafluorophenyl)borate, [4-(2-hydroxy-n-tetradesiloxy))phenyl]phenyliodonium hexafluoroantimonate ... [4-(2-hydroxy-n-tetradesiloxy)phenyl]phenyliodonium trifluorosulfonate, [4-(2-hydroxy-n-tetradesiloxy)phenyl]phenyliodonium hexafluorophosphate, [4-(2-hydroxy-n-tetradesiloxy)phenyl]phenyliodonium tetra(pentafluorophenyl)borate, bis(4-tert-butylphenyl)iodonium hexafluoroantimonate, bis(4-tert-butylphenyl)iodonium hexafluorophosphate, bis(4-tert-butylphenyl)iodonium trifluorosulfonate, bis(4-tert-butylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium trifluoromethanesulfonate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium trifluoromethanesulfonate, diphenyliodonium hydrogen sulfate, 4,4'-dichlorodiphenyliodonium hydrogen sulfate, 4,4'-dibromodiphenyliodonium hydrogen sulfate, 3,3'-dinitrodiphenyliodonium hydrogen sulfate, 4,4'-dimethyldiphenyliodonium hydrogen sulfate, 4,4'-bissuccinimidediphenyliodonium hydrogen sulfate, 3-nitrodiphenyliodonium hydrogen sulfate, 4,4'-dimethoxydiphenyliodonium hydrogen sulfate, bis(dodecylphenyl)iodonium tetra(pentafluorophenyl)borate, (4-octyloxyphenyl)phenyliodonium tetra(3,5-bis(trifluoromethylphenyl)borate and (tolylcumyl)iodonium tetra(pentafluorophenyl)borate; and ferrocene salts (see, for example, EP 0542716B1) such as n5-(2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6,9)(1-methylethyl)benzene]iron.

[0102] Photoinitiators are typically used alone or in combination of two or more photoinitiators. When using photoinitiators, combination with so-called sensitizers is very helpful in adapting the activation wavelength of the photoinitiation system to the selected emission spectrum; for this purpose, refer to literature known to those skilled in the art, such as AW Green's "Industrial Photoinitiators: A technical guide", 2010. Typically in these cases, the mass fraction of the photoinitiator in the curable adhesive does not exceed 4%, but is at least 0.1%, and preferably in the range of 0.5% to 2%. The mass fraction of the sensitizer typically does not exceed 3%, and preferably in the range of 0.5% to 2%.

[0103] Regarding the components of the curable adhesive used in this invention, the inventors have successfully determined particularly advantageous mass fractions that, when implemented, enable the production of curable adhesives with exceptionally high performance. Surprisingly, even relatively large amounts of the (meth)acrylate block copolymer have a beneficial effect on adhesive properties. Therefore, the curable adhesive of this invention is preferred in which the combined mass fraction of the (meth)acrylate block copolymer in the curable adhesive is 28% or more, preferably 30% or more, more preferably 33% or more, and / or where the combined mass fraction of the (meth)acrylate block copolymer in the curable adhesive is in the range of 28% to 80%, preferably in the range of 30% to 65%, more preferably in the range of 33% to 55%.

[0104] Additionally or alternatively, the curable adhesive of the present invention is preferred in which the combined mass fraction of the first epoxide compound E1 in the curable adhesive is 10% or more, preferably 15% or more, more preferably 20% or more, and / or in which the combined mass fraction of the first epoxide compound E1 in the curable adhesive is in the range of 5% to 50%, preferably in the range of 10% to 40%, more preferably in the range of 15% to 30%. Additionally or alternatively, the curable adhesive of the present invention is also preferred in which the combined mass fraction of the second epoxide compound E2 in the curable adhesive is 10% or more, preferably 20% or more, more preferably 30% or more, and / or in which the combined mass fraction of the second epoxide compound E2 in the curable adhesive is in the range of 10% to 60%, preferably in the range of 20% to 55%, more preferably in the range of 30% to 45%.

[0105] In this case, it is particularly preferred to establish the same preferred range for two or three components, preferably three components.

[0106] The curing rate or open time of the curable adhesive of the present invention can be adjusted by adding an open time additive. The curable adhesive of the present invention preferably has an open time of at least one minute, or at least three minutes, more particularly at least five minutes. Generally, the combined mass fraction of the open time additive is in the range of 0 to 15%, preferably in the range of 0 to 10%. Commonly used open time additives are polyols having two or more free hydroxyl functional groups, such as polyethylene glycol 400 (PEG 400), hereinafter referred to as "polyol open time additives". However, there are other known types of open time additives (hereinafter referred to as "non-polyol open time additives") or open time additives without free hydroxyl functional groups. These include, for example, polyethylene glycol dimethyl ether 500. The ether group has a retarding effect on curing comparable to that of polyethylene glycol polyols; however, due to the presence of methyl groups at the beginning and end, it is not a polyol that can be introduced into the network and thus increase the elasticity of the epoxide network. Other non-polyol open time additives are known to those skilled in the art from, for example, WO 02 / 61010A2, EP 276 716A2 and EP 661 324A1, and are also available.

[0107] The inventors have unexpectedly determined that the following curable adhesives of the present invention also exhibit excellent impact resistance, said curable adhesives comprising a polyol open-time additive at a combined mass fraction of less than 0.9%, or excluding the polyol open-time additive (i.e., a combined mass fraction of less than 0.001%), and therefore excluding the polyol open-time additive. Therefore, the curable adhesives of the present invention preferably comprise a polyol open-time additive at a combined mass fraction of less than 0.9%, or excluding the polyol open-time additive (i.e., a combined mass fraction of less than 0.001%). To further improve impact resistance, non-polyol open-time additives are suitable, for example, polyethylene glycol dimethyl ether 500. In these cases, the retardation effect of the ether group on curing is comparable to that of the polyol open-time additive; however, due to the presence of methyl groups at the beginning and end, the compounds in question are not polyols introduced into the polymer network and thus increase the elasticity of the epoxide network. Particularly preferred are the following curable adhesives of the present invention, which include non-polyol open-time additives at a combined mass fraction ranging from 0.5% to 15%.

[0108] Additionally or alternatively, a particularly preferred curable adhesive of the present invention is the following, wherein the combined mass fraction of the second epoxy compound E2 is greater than the combined mass fraction of the first epoxy compound E1. The inventors have surprisingly determined that a higher amount of solid or high-viscosity first epoxy compound E1 is not necessary to achieve sufficient cohesion (initially before curing). Insufficient amount of solid epoxy resin often results in a "muddy" adhesive, which tends to lead to cohesive failure. Surprisingly, no such observation has been made in this case, and therefore it is preferred that the combined mass fraction of the first epoxy compound E1 in the curable adhesive does not exceed 30%, more preferably not more than 25%, and / or that the combined mass fraction of the first epoxy compound E1 in the curable adhesive is in the range of 15% to 30%, more preferably in the range of 20% to 25%. In this case, the combined mass fraction of the second epoxy compound E2 in the curable adhesive is 10% or more, and / or the combined mass fraction of the second epoxy compound E2 in the curable adhesive is in the range of 10% to 60%, more preferably in the range of 30% to 50%.

[0109] If the adhesive is formed from most of the above-mentioned components, a particularly advantageous curable adhesive can be obtained. Therefore, the curable adhesive of the present invention is preferred, wherein the combined mass fraction of the (meth)acrylate block copolymer, the first epoxy compound E1, and the second epoxy compound E2 in the curable adhesive is 80% or more, preferably 90% or more, more preferably 95% or more.

[0110] In addition to the absolute mass fraction, the inventors are also able to determine the relative mass ratios of the components forming the advantageous curable adhesive. Therefore, the curable adhesive of the present invention is preferred in which the combined mass ratio of the (meth)acrylate block copolymer in the curable adhesive to the combined mass ratio of the first epoxy compound E1 and the second epoxy compound E2 is in the range of 0.35:1 to 4:1, preferably in the range of 0.40:1 to 2:1, and more preferably in the range of 0.45:1 to 1.2:1. Additionally or alternatively, the curable adhesive of the present invention is preferred in which the combined mass ratio of the first epoxy compound E1 to the combined mass ratio of the second epoxy compound E2 in the curable adhesive is in the range of 1:10 to 10:1, preferably in the range of 1:5 to 2:1, and more preferably in the range of 1:3 to 1:1. Additionally or alternatively, the curable adhesive of the present invention is particularly preferred in which the combined mass ratio of the second epoxy compound E2 is greater than the combined mass ratio of the first epoxy compound E1. In this case, the ratio of the combined mass of the first epoxy compound E1 to the combined mass of the second epoxy compound E2 in the curable adhesive is between 1:1.5 and 1:2.5; most preferably, the ratio of the combined mass of the first epoxy compound E1 to the combined mass of the second epoxy compound E2 is 1:2.

[0111] Finally, an advantage of the curable adhesives of the present invention is their great flexibility in the use of typical additives, allowing for further adjustment of physicochemical properties according to the requirements of a specific end use. Therefore, curable adhesives comprising one or more additional additives, preferably in a combined mass fraction ranging from 0.1% to 50%, preferably 0.2% to 40%, based on the mass of the adhesive, and / or one or more of these additional additives are preferably selected from tackifying resins, aging inhibitors, light stabilizers, UV absorbers, and rheology modifiers.

[0112] A special case of additional components used to adjust the properties of adhesives is insoluble fillers, which can be added to curable adhesives to obtain filled curable adhesives. These insoluble fillers are particulate fillers having an average particle size (D50) of 5 μm or larger, preferably 10 μm or larger, more preferably 20 μm or larger, which are insoluble in the curable adhesive and are present therein in the form of a dispersion; and macroscopic fillers such as fibers. The insoluble fillers are preferably selected from particulate fillers. More preferably, the insoluble fillers are selected from 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. Also suitable as insoluble fillers are, for example, small pieces and rods of materials insoluble in curable adhesives, fibers, and loosely laid fabrics. Because they already possess macroscopic dimensions and lack solubility in some cases, these fillers essentially have no effect on the compositional chemistry of the disclosed curable adhesives, but rather exist as a heterogeneous mixture with the curable adhesives. Accordingly, in the context of this invention, these insoluble fillers are not considered part of the curable adhesive and are consequently ignored when calculating their mass fraction relative to the mass of the curable adhesive. As stated above, the definition in the context of this invention is, rather, that the addition of insoluble fillers to the curable adhesives of this invention results in a filled curable adhesive, i.e., a filled curable adhesive comprising the following:

[0113] x) The curable adhesive of the present invention, preferably as disclosed above as preferred, and

[0114] y) One or more insoluble fillers.

[0115] More preferably, in this case, the combined mass fraction of the insoluble filler is in the range of 1 to 50%, preferably in the range of 2 to 40%, and more preferably in the range of 5 to 30%.

[0116] For future use in the final application, it is advantageous to have good handling performance if the curable adhesive has inherent pressure-sensitive adhesive properties and can therefore be classified as a pressure-sensitive adhesive. These properties are particularly easy to establish in the curable adhesive of the present invention due to the advantageous high cohesiveness. The pressure-sensitive adhesive properties allow for reliable and stable application of reactive adhesive tapes to the substrate prior to curing. Therefore, the curable adhesive of the present invention, wherein the curable adhesive is a pressure-sensitive adhesive, is preferred.

[0117] According to the understanding of technicians, pressure-sensitive adhesives (PSA) are adhesives that possess pressure-sensitive adhesive properties, meaning they can form a durable bond with a substrate even under relatively weak applied pressure. Correspondingly, pressure-sensitive tapes can typically be peeled off from the substrate without residue after use and generally possess permanent intrinsic tack even at room temperature, meaning they have a certain viscosity and contact tack, thus wetting the surface of the substrate even under low applied pressure. The pressure-sensitive adhesiveness of pressure-sensitive tapes is a result of using pressure-sensitive adhesives as adhesives. Without being bound by this theory, PSA is often considered as a fluid with an extremely high viscosity and an elastic component, thus possessing characteristic viscoelastic properties, which lead to the aforementioned durable intrinsic tack and pressure-sensitive adhesive ability. It is believed that for such PSAs, there is a viscous flow process and the formation of elastic restoring forces during mechanical deformation. The viscous flow component is used to achieve adhesion, while the elastic restoring force component is particularly needed to achieve cohesion. The relationship between rheology and pressure-sensitive adhesive properties is known in the prior art and is described, for example, in Satas, “Handbook of PressureSensitive Adhesives Technology”, 3rd edition, (1999), pp. 153-203.

[0118] To characterize the degree of elasticity and viscous components, storage modulus (G') and loss modulus (G'') are typically used, which can be determined by dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed in WO2015 / 189323. For the purposes of this invention, when at a temperature of 23°C and 10 0 Up to 10 1 Within the deformation frequency range of arcs per second, G' and G” are each at least partially located at 10 3 Up to 10 7 When Pa is within a certain range, the adhesive is preferably understood to have pressure-sensitive adhesive properties and is therefore PSA.

[0119] The following discloses an illustrative curable adhesive that, according to the inventors’ assessment, is particularly advantageous and describes a particularly preferred combination of features, wherein the curable adhesive of the present invention comprising two or more illustrative curable adhesives is particularly preferred.

[0120] The first thermosetting adhesive of the present invention is initially preferred, comprising, based on the mass of the adhesive, the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 30 to 45%; ii) a liquid epoxide, such as Epikote 828, in a mass fraction ranging from 20 to 35%; iii) a solid epoxide, such as Araldite ECN 1273, in a mass fraction ranging from 20 to 35%; iv) a curing agent, such as dicyandiamide, in a mass fraction ranging from 2 to 6%; and v) an accelerator, such as Curezol MZ-A, in a mass fraction ranging from 0.01 to 0.5%.

[0121] Also preferred is the second thermosetting adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 45% to 60%; ii) a liquid epoxide, such as Epikote 828, in a mass fraction ranging from 15% to 30%; iii) a solid epoxide, such as Araldite ECN 1273, in a mass fraction ranging from 15% to 30%; iv) a curing agent, such as dicyandiamide, in a mass fraction ranging from 2% to 5%; and v) an accelerator, such as Curezol MZ-A, in a mass fraction ranging from 0.01% to 0.5%.

[0122] Also preferred is the third thermosetting adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 25% to 50%; ii) a liquid epoxide, such as Epikote 828, in a mass fraction ranging from 10% to 25%; iii) a solid epoxide, such as Araldite ECN 1273, in a mass fraction ranging from 10% to 25%; iv) a curing agent, such as dicyandiamide, in a mass fraction ranging from 2% to 5%; v) an accelerator, such as Curezol MZ-A, in a mass fraction ranging from 0.01% to 0.5%; and vi) a filler, such as Silibeads 5211, in a mass fraction of 30%.

[0123] Also preferred is the fourth thermosetting adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 25% to 35%; ii) a liquid epoxide, such as Epikote 828, in a mass fraction ranging from 10% to 25%; iii) a solid epoxide, such as Araldite ECN 1273, in a mass fraction ranging from 10% to 40%; iv) a high-viscosity epoxide, such as Struktol PD3611 (viscosity exceeding 150 Pa·s at 25°C), in a mass fraction ranging from 10% to 40%; v) a curing agent, such as dicyandiamide, in a mass fraction ranging from 2% to 7%; and vi) an accelerator, such as Curezol MZ-A, in a mass fraction ranging from 0.01% to 0.7%.

[0124] Also preferred is the fifth thermosetting adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 25% to 50%; ii) a liquid epoxide, such as bisphenol A diglycidyl ether (e.g., Epikote 828) or a cycloaliphatic epoxide (e.g., Uvacure 1500), in a mass fraction ranging from 10% to 45%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT 7072) or epoxy cresol and / or epoxy phenol phenolic varnish (novolacs) (e.g., Araldite ECN 1273), in a mass fraction ranging from 10% to 45%; iv) optionally a polyol open time additive, such as polyethylene glycol (M nThe photocurable adhesive of the present invention comprises (v) a polyol open time additive (vi) in a mass fraction ranging from 0.5% to 15%, more particularly from 0.5% to 10% or 5% to 15%, and (v) a photoinitiator, such as triarylsulfonium antimonate, in a mass fraction ranging from 0.3% to 2%. Particularly preferred are the photocurable adhesives of the present invention comprising (vi) a polyol open time additive (vi) in a combined mass fraction of less than 0.9% (i.e., less than 0.001% in a combined mass fraction), and thus being free of polyol open time additive (vi). Therefore, the photocurable adhesive of the present invention is particularly preferred, which, based on the mass of the adhesive, comprises or consists of the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 25% to 50%; ii) a liquid epoxide, such as (optionally hydrogenated) bisphenol A diglycidyl ether (e.g., Epikote 828 or HBE-100) or a cycloaliphatic epoxide (e.g., Uvacure 1500), in a mass fraction ranging from 10% to 45%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT 7072) or epoxy cresol and / or epoxy phenol novolacs (e.g., Araldite ECN). 1273), in a mass fraction ranging from 10% to 45%; and v) an initiator, such as triarylsulfonium antimonate, in a mass fraction ranging from 0.3% to 2%.

[0125] Also preferred is the sixth thermosetting adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 45% to 70%; ii) a liquid epoxide, such as bisphenol A diglycidyl ether (e.g., Epikote 828) or a cycloaliphatic epoxide (e.g., Uvacure 1500), in a mass fraction ranging from 10% to 45%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT 7072) or epoxy cresol and / or epoxy phenol phenolic varnish (novolacs) (e.g., Araldite ECN 1273), in a mass fraction ranging from 10% to 45%; iv) optionally a polyol open time additive, such as polyethylene glycol (M nThe ingredients are: (v) a polyol open time additive (vi) or polycaprolactone (e.g., Capa2000) in a mass fraction ranging from 0.5% to 15%, more particularly from 0.5% to 10% or 5% to 15%; and (v) a photoinitiator, such as triarylsulfonium antimonate, in a mass fraction ranging from 0.3% to 2%. Particularly preferred are the photocurable adhesives of the present invention comprising (vi) a polyol open time additive in a combined mass fraction of less than 0.9% (i.e., less than 0.001% in a combined mass fraction), and therefore free of polyol open time additive (vi). Therefore, the photocurable adhesive of the present invention is particularly preferred, which, based on the mass of the adhesive, comprises or consists of the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 45% to 70%; ii) a liquid epoxide, such as (optionally hydrogenated) bisphenol A diglycidyl ether (e.g., Epikote 828 or HBE-100) or a cycloaliphatic epoxide (e.g., Uvacure 1500), in a mass fraction ranging from 10% to 45%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT 7072) or epoxy cresol and / or epoxy phenol novolacs (e.g., Araldite ECN). 1273), in a mass fraction ranging from 10% to 45%; and v) an initiator, such as triarylsulfonium antimonate, in a mass fraction ranging from 0.3% to 2%.

[0126] Also preferred is the seventh photocurable adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 30% to 60%; ii) a liquid epoxide, such as (optionally hydrogenated) bisphenol A diglycidyl ether (e.g., Epikote 828 or HBE-100) or a cycloaliphatic epoxide (e.g., Uvacure 1500), in a mass fraction ranging from 20% to 45%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT7072) or epoxy cresol and / or epoxy phenolic varnish (novolacs) (e.g., Araldite ECN 1273), in a mass fraction ranging from 10% to 40%; iv) optionally a polyol open time additive, such as polyethylene glycol (M nThe open time additives are: (v) a non-polyol open time additive (e.g., polyethylene glycol dimethyl ether 500, ~400 g / mol) in the range of 0.5 to 10% by mass; and (v) an initiator, e.g., triarylsulfonium antimonate, in the range of 0.3 to 2% by mass. For this photocurable adhesive of the invention, it is particularly preferred to include a polyol open time additive with a combined mass fraction of less than 0.9% or to contain no polyol open time additive (i.e., less than 0.001% by mass), and therefore to be free of polyol open time additives.

[0127] Also preferred is the eighth photocurable adhesive of the present invention, which, based on the mass of the adhesive, comprises the following: i) a corresponding ABA-structured (meth)acrylate block copolymer, such as Kuraire LA2140, LA2250, or LA3320, in a mass fraction ranging from 30% to 60%; ii) a liquid epoxide, (e.g., Epikote 828 or HBE-100), more preferably hydrogenated bisphenol A diglycidyl ether or hydrogenated bisphenol F diglycidyl ether (e.g., HBE-100), in a mass fraction ranging from 20% to 50%; iii) a solid epoxide, such as bisphenol A diglycidyl ether (e.g., Araldite GT 7072) or epoxy cresol and / or epoxy phenol phenolic varnish (novolacs) (e.g., Araldite ECN1273), in a mass fraction ranging from 20% to 40%; iv) optionally a polyol open time additive, such as polyethylene glycol (M n The open time additives are: (v) a non-polyol open time additive (e.g., polyethylene glycol dimethyl ether 500, ~400 g / mol) in the range of 0.5 to 10% by mass; and (v) an initiator, e.g., triarylsulfonium antimonate, in the range of 0.3 to 2% by mass. For this photocurable adhesive of the invention, it is particularly preferred to include a polyol open time additive with a combined mass fraction of less than 0.9% or to contain no polyol open time additive (i.e., less than 0.001% by mass), and therefore to be free of polyol open time additives.

[0128] The curable adhesives of the present invention can be used, for example, directly as adhesives; depending on the application method, they can also be provided, for example, in the form of tapes. However, to obtain highly advantageous processing quality, particularly favorable results are usually achieved when the curable adhesives of the present invention are used as adhesive layers in single-sided or double-sided tapes that further include a carrier layer. Therefore, the present invention also relates to tapes, more particularly reactive tapes, which include the curable adhesives of the present invention as adhesive layers, wherein the tape preferably includes a carrier layer.

[0129] The term "tape" is clear to those skilled in the art of adhesive bonding. In the context of this invention, the term "tape" refers to all thin, sheet-like structures, i.e., structures having a primary extent in two dimensions, more specifically, films, film portions, and labels, preferably tapes having an extended length and a finite width, and corresponding tape portions.

[0130] The carrier layer typically refers to the lower layer of such a multilayer adhesive tape, and it critically determines the tape's mechanical and physical properties, such as tear resistance, stretchability, insulation, or resilience. Examples of conventional carrier layer materials are woven fabrics, loosely laid cloths, and polymer films, such as PET and polyolefin films. However, the carrier layer itself can also be a pressure-sensitive adhesive. In a preferred embodiment, the tape of the present invention can be a double-sided tape, with the curable adhesive of the present invention applied to both sides of the carrier layer.

[0131] In the tape of this invention, the adhesive layer can be lined with a so-called release liner to allow for unobstructed unfolding and to protect the PSA from soiling. This release liner typically consists of a single- or double-sided siliconized polymer film (such as PET or PP) or a siliconized paper carrier.

[0132] Starting with the curable adhesive and the tape of the present invention, the use of the curable adhesive or the tape of the present invention for bonding two or more components by curing the curable adhesive is further disclosed.

[0133] Finally, a method for manufacturing the curable adhesive of the present invention is also disclosed, comprising the following steps:

[0134] a) Prepare or provide ABA-structured (meth)acrylate block copolymers, and

[0135] b) Mixing (meth)acrylate block copolymers with one or more first epoxy compounds E1 and one or more second epoxy compounds E2 and one or more initiators, and optionally one or more additional additives, to obtain a curable adhesive.

[0136] The preferred embodiments of the present invention will be further explained and described below with reference to experiments.

[0137] A. Manufacturing of curable adhesives:

[0138] Synthesis of random contrast copolymer (VP1):

[0139] The reaction was carried out at room temperature (25°C) under a nitrogen atmosphere in a screw-top EPA bottle with a volume of 60 ml. The radiation sources used included two Skymore 110W UV LED nail drying lamps, each with a power of 110W and an emission wavelength of 365nm, positioned such that the reaction vessel was 2 cm away from the LEDs.

[0140] 320 mg of S,S-dibenzyl trithiocarbonate (DBTTC) and 16 g of methyl methacrylate (MMA,δ) were added. p =9.31MPa 0.5 ), 24g n-butyl acrylate (BA,δ) p =8.60MPa 0.5 The mixture of 9 g of toluene and 9 g of methanol was homogenized and then purged with nitrogen for 10 minutes. Polymerization was initiated by irradiating the reaction mixture. To terminate the reaction, irradiation was stopped, and the high-viscosity reaction mixture was dissolved in THF, precipitated by adding excess cold methanol dropwise, and filtered to collect the precipitate. The random contrast copolymer VP1 has a molecular weight of 120,000 g / mol.

[0141] Manufacturing of curable adhesives:

[0142] Random contrast copolymer VP1 and commercially available ABA (meth)acrylate block copolymers (P1, Kuraire LA2250 (M) with the same basic monomer composition were obtained from random contrast copolymer VP1 and commercially available ABA (meth)acrylate block copolymers (P1, Kuraire LA2250 (M)). n Approximately 60,000 g / mol, and M w (approximately 66,000 g / mol) or P2, Kuraire LA3320 (M n Approximately 108,000 g / mol and M w (Approximately 119,000 g / mol), wherein block A is composed of polymethyl methacrylate (δ-methyl methacrylate). p =9.31MPa 0.5 The B block is composed of polybutylene acrylate (δ-butylene acrylate). p =8.60MPa 0.5 It is composed of [components], which, through mixing with other components, yield a curable adhesive in a conventional manner.

[0143] As the first epoxide compound E1, a commercially available solid bisphenol A diglycidyl ether (E1a, DER662E or E1b, Araldite GT 7072) is used. As the second epoxide compound E2, a commercially available liquid cyclic aliphatic epoxide (E2a, 3',4'-epoxycyclohexanecarboxylic acid epoxycyclohexyl methyl ester; Uvacure 1500) or a commercially available liquid bisphenol A diglycidyl ether (E2b, Epikote 828 or E2d, Araldite GY 250) or a commercially available liquid hydrogenated bisphenol A diglycidyl ether (E2c, HBE-100) is used.

[0144] Polyethylene glycol 400 (PEG 400) or polyethylene glycol dimethyl ether 500 (CAS: 24991-55-7) was used as an open time additive, and triarylsulfonium hexafluoroantimonate (CAS: 109037-75-4) was used as an initiator.

[0145] Table 4 summarizes the composition of the adhesive. A tape with a thickness of approximately 100 μm was manufactured from the adhesive by coating and evaporating the solvent.

[0146] Table 4—Composition and Solvents of Adhesives; All figures are weight percentages.

[0147]

[0148] B. Adhesion Experiment:

[0149] Peel adhesion was determined according to ISO 29862 (Method 3) at 23°C and 50% relative humidity, with a removal speed of 300 mm / min and a removal angle of 180°. The adhesive layer had a thickness of 100 μm in each case. The reinforcing film used was an etched PET film with a thickness of 50 μm, available from Coveme (Italy). The substrates used included compliant steel sheets. The uncured measuring tape was bonded using a 4 kg roll-on machine at 23°C. The tape was removed immediately after application. The measurements (in N / cm) are the average of three individual measurements, and the failure modes are recorded as follows: adhesive failure (A) or cohesive failure (C).

[0150] The lap-shear strength of the cured adhesive was also determined. Adhesive strength was determined in a dynamic lap-shear test at 23°C and 50% relative humidity according to DIN-EN 1465 at a test speed of 1 mm / min, and the results were quantitative in each case (results in N / mm² = MPa). The test bars used were steel bars cleaned with acetone before bonding. The tape layer thickness was consistent with the details described above in each case. In this case, the tape was irradiated with appropriate light before assembling the test bars but after removing the second backing, and then the test samples were assembled immediately. Measurements were taken after storage at 23°C and 50% relative humidity for 7 days. The reported results are the average of three measurements.

[0151] In addition, the impact resistance of the cured adhesive was investigated. The impact test used for this purpose provides information on the adhesive strength of the adhesive product in the direction normal to the adhesive layer. For this test, a first substrate (1) (polycarbonate, Makrolon 099, 3 mm thick) with a diameter of 21 mm and a second substrate (2) (polycarbonate, Makrolon 099, 3 mm thick) was provided in a square shape with a side length of 40 mm and a circular opening (drilled hole) with a diameter of 9 mm arranged in the center; and an adhesive film sample for investigation, which was also produced in a circular shape with a diameter of 21 mm (cut or die-cut to size).

[0152] Test elements were generated from the corresponding three components by first accurately bonding the adhesive film sample to the substrate (1) on a free surface. The temporary protective film (silicified PET liner) was then removed, and the test element was illuminated by a 365nm UV-LED at at least 1000mJ / cm². 2 Irradiation is applied to activate the curable adhesive. Then, within two minutes, the assembly thus manufactured is concentrically applied to substrate 2 through the now exposed adhesive product side, concentric meaning that the circular cutout in substrate 2 is precisely positioned in the center of the circular first substrate 1 (thus creating a 282mm diameter). 2 The adhesive area is compressed with a force of at least 280N for at least 10 seconds to produce a test element.

[0153] After pressing, the test element was conditioned at 23°C and 50% relative humidity for 72 hours.

[0154] After appropriate storage, the test elements are clamped into the sample holders, arranging the assemblies horizontally. The test element with the polycarbonate plate (substrate 1) is inserted downwards into the sample holder. The sample holder is then inserted centered into the support provided by the equipment used ("DuPont Impact Tester", from Cometech, Taiwan, model QC-641). The impact head is inserted so that a circular impact geometry with a diameter of 5 mm is positioned at the center of the adhesive surface of substrate 1 and flush with it. A weight (cart) with a mass of 307 g, guided on two guide rods, is dropped vertically from an initial height of 5 cm onto the prepared assembly containing the sample holder, test element, and impact head (measurement conditions: 23°C, 50% relative humidity). The height (h) of the weight drop is increased in 5 cm steps until, as a result of the impact load, the introduced impact energy destroys the test element, and the polycarbonate plate (substrate 1) detaches from the base plate (substrate 2). To compare the experiments with different test elements, the energy is calculated as follows.

[0155] DuPont impact [mJ / cm] 2 ]=(m(cart)[kg]*9.81[kg / m*s 2 ]*h[m]) / A(adhesive area)[cm 2 ].

[0156] Five samples were tested for each adhesive, and the average energy was calculated and reported as an indicator of impact strength. The experimental results are summarized in Table 5.

[0157] Table 5—Summary of Adhesion Experiments

[0158]

[0159] *A: Adhesive failure; C: Cohesive failure

[0160]

[0161] Based on the fracture modes in the peel adhesion test, the advantageous cohesive strengthening effect of the (meth)acrylate block copolymers used in the adhesives of the present invention can be demonstrated, advantageously even when using large amounts of reactive resin. Furthermore, experiments combining the (meth)acrylate block copolymers with specific reactive resins show that reactive adhesives with significantly improved impact resistance can be obtained. In this regard, Examples B5 to B7 demonstrate that impact resistance can be improved by using relatively high molecular weight (meth)acrylate block copolymers (such as Kurairel LA3320) in the adhesives of the present invention. This effect may not only be attributed to the higher molecular weight of LA3320 (Mw: about 119,000 g / mol) compared to LA2250 (Mw: about 66,000 g / mol). Unwilling to be confined to a specific theory, the inventors believe that the lower hard block fraction (proportion) of MMA in LA3320, slightly below 20%, coupled with the increased molecular weight, suggests better phase separation in the intermediate blocks of the cured epoxy tape, thus having a stronger positive impact on impact performance. In further experiments, the inventors have determined that this surprising effect even occurs in comparisons with the more similar LA2330 and LA3320, leading to an improvement in impact resistance (over 50 mJ / cm²). 2 ).

[0162] Compared to existing technologies, it has been surprisingly found that in the curable adhesives of the present invention, a significantly higher amount of (meth)acrylate block copolymers is not only excellently suited for obtaining good pressure-sensitive adhesives in the uncured state (where the adhesive fails in peel adhesion tests), but also for obtaining strong adhesion in the cured state. If a person skilled in the art uses the amount of (meth)acrylate block copolymers known in principle in other adhesive systems, as shown in V3, the resulting adhesives tend to be paste-like and lack suitability as pressure-sensitive adhesives.

[0163] The lap-shear test after curing shows that the adhesive of the present invention can achieve good bond strength after curing, which is an indicator of adequate adaptability. The advantages of the adhesive of the present invention are particularly evident in the combination of its properties before and after active curing.

[0164] Furthermore, Examples B3, B5, and B7 clearly demonstrate that the hydrogenated epoxy compounds in the adhesives of the present invention result in higher adhesive strength.

Claims

1. A curable adhesive, comprising, based on the mass of the curable adhesive: a) Combining one or more ABA-structured (meth)acrylate block copolymers with a mass fraction of 28% or higher. The A blocks independently represent poly(meth)acrylates with a glass transition temperature (Tg) of 50°C or higher, which can be prepared by polymerization of A monomer components containing A monomers. The B block represents a poly(meth)acrylate with a glass transition temperature Tg of less than 50°C, which can be prepared by polymerization of a B monomer component containing a B monomer. b) Combining one or more polymerizable first epoxy compounds E1 with a mass fraction of 5% or higher, wherein the first epoxy compound E1 is a solid at 25°C or a high viscosity material with a dynamic viscosity of 50 Pa s or higher. and c) Combining one or more polymerizable second epoxy compounds E2 at a mass fraction of 5% or higher, wherein the second epoxy compound E2 is a liquid with a dynamic viscosity of 40 Pa s or lower at 25°C. The Hansen solubility parameter of the monomer unit from monomer A in block A is <δ. p The polar component of the substance weighted by the amount of substance <δ p (A) Between 9.0 and 11.0 MPa 0.5 Within the range, The Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ. p The polar component of the substance weighted by the amount of substance <δ p >(B) Less than 9.0 MPa 0.5 ,and in - The combined mass fraction of the first epoxide compound E1 is 20% or higher; and / or The combined mass fraction of the (meth)acrylate block copolymer, the first epoxy compound E1, and the second epoxy compound E2 is 90% or more.

2. The curable adhesive according to claim 1, wherein the Hansen solubility parameter of the monomer unit from monomer A in block A is <δ p The polar component of the substance weighted by the amount of substance <δ p (A) Between 9.1 and 10.0 MPa 0.5 Within the range.

3. The curable adhesive according to claim 1, wherein the Hansen solubility parameter of the monomer unit from monomer A in block A is <δ p The polar component of the substance weighted by the amount of substance <δ p (A) Between 9.2 and 9.5 MPa 0.5 Within the range.

4. The curable adhesive according to claim 1, wherein the Hansen solubility parameter of the monomer unit from monomer A in block A is <δ p The polar component of the substance weighted by the amount of substance <δ p (A) Between 9.3 and 9.4 MPa 0.5 Within the range.

5. The curable adhesive according to any one of claims 1 to 4, wherein the Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ p The polar component of the substance weighted by the amount of substance <δ p (B) Between 6.0 and 8.9 MPa 0.5 Within the range.

6. The curable adhesive according to any one of claims 1 to 4, wherein the Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ p The polar component of the substance weighted by the amount of substance <δ p (B) Between 6.5 and 8.8 MPa 0.5 Within the range.

7. The curable adhesive according to any one of claims 1 to 4, wherein the Hansen solubility parameter of the monomer unit from monomer B in the B block is <δ p The polar component of the substance weighted by the amount of substance <δ p (B) Between 7.0 and 8.7 MPa 0.5 Within the range.

8. The curable adhesive according to any one of claims 1 to 4, wherein the A monomer component comprises one or more A monomers selected from methyl methacrylate, ethyl acrylate, methyl acrylate, 2-phenoxydiethylene glycol acrylate and tert-butyl acrylate.

9. The curable adhesive according to any one of claims 1 to 4, wherein the B monomer component comprises one or more B monomers selected from n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isobornyl acrylate, 2-phenoxyethyl acrylate, propylheptyl acrylate, and acrylic acid.

10. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the (meth)acrylate block copolymer in the curable adhesive is 30% or higher.

11. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the (meth)acrylate block copolymer in the curable adhesive is 33% or higher.

12. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the first epoxy compound E1 in the curable adhesive is 10% or higher.

13. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the first epoxy compound E1 in the curable adhesive is 15% or higher.

14. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the first epoxy compound E1 in the curable adhesive is 20% or higher.

15. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the second epoxy compound E2 in the curable adhesive is 10% or higher.

16. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the second epoxy compound E2 in the curable adhesive is 20% or higher.

17. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass fraction of the second epoxy compound E2 in the curable adhesive is 30% or higher.

18. The curable adhesive according to any one of claims 1 to 4, wherein one or more first epoxy compounds E1 and / or one or more second epoxy compounds E2 are selected from epoxy compounds having at least one cycloaliphatic group.

19. The curable adhesive according to any one of claims 1 to 4, wherein one or more first epoxy compounds E1 and / or one or more second epoxy compounds E2 are selected from epoxy compounds having cyclohexyl groups or dicyclopentadienyl groups.

20. The curable adhesive according to any one of claims 1 to 4, wherein the two A blocks are poly(meth)acrylates with a glass transition temperature difference of less than 5°C, wherein the poly(meth)acrylates can be prepared by polymerization of the same A monomer component from the A monomer.

21. The curable adhesive according to claim 20, wherein the glass transition temperatures of the poly(meth)acrylates differ by less than 3°C.

22. The curable adhesive according to claim 20, wherein the glass transition temperatures of the poly(meth)acrylates differ by less than 1°C.

23. The curable adhesive according to claim 20, wherein the A blocks are substantially the same.

24. The curable adhesive according to any one of claims 1 to 4, wherein monomer A comprises one or more monomers selected from (meth)acrylate monomers and (meth)acrylic acid.

25. The curable adhesive of claim 24, wherein monomer A comprises a monomer.

26. The curable adhesive according to claim 24, wherein one or more monomers are selected from methacrylate monomers.

27. The curable adhesive of claim 24, wherein monomer A is composed of 90% or more of these monomers, based on the combined mass of monomer A.

28. The curable adhesive of claim 24, wherein monomer A is composed of 95% or more of these monomers, based on the combined mass of monomer A.

29. The curable adhesive of claim 24, wherein monomer A is composed of 99% or more of these monomers, based on the combined mass of monomer A.

30. The curable adhesive of claim 24, wherein monomer A is substantially entirely composed of these monomers, based on the combined mass of monomer A.

31. The curable adhesive according to any one of claims 1 to 4, wherein monomer B comprises one or more monomers selected from (meth)acrylate monomers and (meth)acrylic acid.

32. The curable adhesive according to claim 31, wherein monomer B comprises a monomer.

33. The curable adhesive according to claim 31, wherein one or more monomers are selected from acrylate monomers and acrylic acid.

34. The curable adhesive according to claim 31, wherein one or more monomers are selected from acrylate monomers.

35. The curable adhesive of claim 31, wherein monomer B is composed of 90% or more of these monomers, based on the combined mass of monomer B.

36. The curable adhesive of claim 31, wherein monomer B is composed of 95% or more of these monomers, based on the combined mass of monomer B.

37. The curable adhesive of claim 31, wherein monomer B is composed of 99% or more of these monomers, based on the combined mass of monomer B.

38. The curable adhesive of claim 31, wherein monomer B is substantially entirely composed of these monomers, based on the combined mass of monomer B.

39. The curable adhesive according to any one of claims 1 to 4, wherein the number average molecular weight M of the (meth)acrylate block copolymer is... n In the range of 20,000 to 1,000,000 g / mol.

40. The curable adhesive according to any one of claims 1 to 4, wherein the number average molecular weight M of the (meth)acrylate block copolymer is... n In the range of 90,000 to 500,000 g / mol.

41. The curable adhesive according to any one of claims 1 to 4, wherein the number average molecular weight M of the (meth)acrylate block copolymer is... n In the range of 105,000 to 150,000 g / mol.

42. The curable adhesive according to any one of claims 1 to 4, wherein the weight average molecular weight M of the (meth)acrylate block copolymer is... w In the range of 20,000 to 1,000,000 g / mol.

43. The curable adhesive according to any one of claims 1 to 4, wherein the weight average molecular weight M of the (meth)acrylate block copolymer is... w In the range of 100,000 to 500,000 g / mol.

44. The curable adhesive according to any one of claims 1 to 4, wherein the weight average molecular weight M of the (meth)acrylate block copolymer is... w In the range of 115,000 to 150,000 g / mol.

45. The curable adhesive according to any one of claims 1 to 4, wherein the ratio of the combined mass of the (meth)acrylate block copolymer in the curable adhesive to the combined mass of the first epoxy compound E1 and the second epoxy compound E2 is in the range of 0.35:1 to 4:

1.

46. ​​The curable adhesive according to any one of claims 1 to 4, wherein the ratio of the combined mass of the (meth)acrylate block copolymer in the curable adhesive to the combined mass of the first epoxy compound E1 and the second epoxy compound E2 is in the range of 0.40:1 to 2:

1.

47. The curable adhesive according to any one of claims 1 to 4, wherein the ratio of the combined mass of the (meth)acrylate block copolymer in the curable adhesive to the combined mass of the first epoxy compound E1 and the second epoxy compound E2 is in the range of 0.45:1 to 1.2:

1.

48. The curable adhesive according to any one of claims 1 to 4, wherein the ratio of the combined mass of the first epoxy compound E1 to the combined mass of the second epoxy compound E2 in the curable adhesive is in the range of 1:10 to 10:

1.

49. The curable adhesive according to any one of claims 1 to 4, wherein the combined mass ratio of the first epoxy compound E1 to the combined mass ratio of the second epoxy compound E2 in the curable adhesive is in the range of 1:5 to 2:

1.

50. The curable adhesive according to any one of claims 1 to 4, wherein the ratio of the combined mass of the first epoxy compound E1 to the combined mass of the second epoxy compound E2 in the curable adhesive is in the range of 1:3 to 1:

1.

51. A tape comprising a curable adhesive as an adhesive layer according to any one of claims 1 to 50.

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