Chemical-resistant, reactively curable adhesive and adhesive tape

Abstract

The invention relates to a reactively curable adhesive, to a reactively curable adhesive tape comprising the reactively curable adhesive, and to the use of corresponding adhesives and adhesive tapes for bonding of two or more components. The reactively curable adhesive comprises: (a) one or more (co)polymers; and (b) at least one epoxy compound; and (c) at least one photoinitiator for initiation of a cationic polymerization; and (d) at least one chemical compound comprising at least one phenyl group or a benzene ring-substituted derivative of a phenyl group.

Description

[0001] Chemical-resistant, reactive-curing adhesive and tape

[0002] The invention relates to a reactively curable adhesive composition, a reactively curable adhesive tape comprising the reactively curable adhesive composition and the use of corresponding adhesive compositions and adhesive tapes for bonding two or more components.

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

[0004] However, another type of adhesive tape is also of great importance, particularly for use in industrial manufacturing. These adhesive tapes, which are sometimes also referred to as reactive (pressure-sensitive) adhesive tapes, use a reactively curable adhesive, sometimes also referred to as a reactive adhesive. Such curable adhesives or reactive adhesives have not yet reached their maximum degree of crosslinking in the state intended for application and can be cured by external influences by initiating polymerization in the reactive adhesive, thereby increasing the degree of crosslinking. This changes the mechanical properties of the now cured adhesive, with particular increases in viscosity, surface hardness, and strength.

[0005] Reactive adhesives are known in the art and can have very different chemical compositions. These reactive adhesives have in common that the crosslinking reaction can be triggered by external factors, for example, by the application of energy, particularly by temperature, plasma, or radiation curing, and / or contact with a polymerization-promoting substance, as is the case with moisture-curing adhesives, for example.

[0006] A particularly industrially relevant type of reactive adhesive is that containing cationically curable epoxy components. Due to the handling and application properties, as well as the achievable adhesive properties, such reactive adhesives are considered particularly advantageous for a wide range of industrial applications. Pressure-sensitive adhesive tapes with reactive adhesives containing cationically curable epoxy components are particularly advantageous because they can be applied much more easily and with greater positioning precision than liquid adhesives. Furthermore, such reactive adhesives can function as structural or semi-structural adhesives after curing.According to DIN EN 923: 2006-01, structural adhesives are adhesives that form adhesive bonds that can maintain a specified strength in a structure for a specified, extended period of time (according to the ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). They are therefore adhesives for bonds subject to high chemical and physical stresses, which, when cured, contribute to the strengthening of the adhesive tapes.

[0007] Reactive pressure-sensitive adhesive tapes are well known to those skilled in the art. WO 2023 / 274875 A1 discloses reactive adhesive tapes comprising a film, a first outer reactive adhesive, and a second outer reactive adhesive, wherein at least one of the reactive adhesives comprises a reactive component such as an epoxy resin, a photoinitiator, one or more foaming agents, and more than 60.0 wt. % of a polymer, and wherein the reactive adhesive is foamed. In these adhesive tapes, the die-cutting properties are improved by using a film in combination with a foamed adhesive.

[0008] US 10,676,655 B2 discloses a curable pressure-sensitive adhesive which, upon curing, provides a semi-structural or structural adhesive having improved cold flow properties and exceptional adhesion properties and which comprises (a) a tetrahydrofurfuryl (meth)acrylate copolymer, (b) an epoxy resin, (c) a polyether polyol, (d) a hydroxy-functional film-forming polymer, and (e) a cationic photoinitiator.

[0009] WO 2017 / 174303 A1 describes a pressure-sensitive adhesive tape which contains a radiation-activatable polymerisable composition which in turn contains A 5 to 60 parts by weight of at least one film-forming component;

[0010] B 40 to 95 parts by weight of at least one epoxy component;

[0011] C 0.1 to 10 parts by weight of at least one photoinitiator, and

[0012] D optionally contains 0.1 to 200 parts by weight of at least one additive, based in each case on the radiation-activatable polymerizable composition, wherein the parts by weight of components A and B add up to 100, and which is characterized in that the film-forming component A comprises at least one polyurethane polymer. This radiation-activatable polymerizable composition should have a sufficient open time of at least one minute and exhibit a satisfactory dark reaction after radiation activation, as well as a good final bond strength of at least 2 MPa on steel.

[0013] EP 3091059 A1 discloses a pressure-sensitive adhesive tape comprising a (semi-)structural adhesive composition comprising at least one polymer, optionally an adhesive resin, at least one reactive resin, wherein the adhesive composition contains at least 104 parts of the at least one reactive resin per 100 parts of polymer and adhesive resin, and at least one initiator and / or hardener and / or accelerator, wherein the adhesive tape, after curing, exhibits significantly higher shear strengths than other adhesive tapes / adhesive compositions of the prior art.

[0014] Such reactive adhesives or pressure-sensitive adhesive tapes containing reactive adhesives are particularly suitable for miniaturized applications, such as those required in the electronics industry. Here, it is increasingly important to create highly precise and space-saving connections between components. Furthermore, due to the still significant global demand for communications and entertainment electronics, the performance requirements of the devices are constantly increasing, so the adhesive tapes used are also subject to constantly new, or at least increasingly, performance requirements.In particular, due to the development of wearable electronic devices such as smart watches, it is becoming increasingly important that the adhesives used in these devices, in addition to the high bond strengths expected of (semi-)structural adhesives, also demonstrate high resistance to various chemicals (such as perspiration, skin oils or sebum, sunscreen, or cosmetic skin care products). This resistance to chemicals (so-called "chemical resistance") is simulated by the cured pressure-sensitive adhesive tapes maintaining acceptable bond strength even after prolonged storage in various media and, ideally, exhibiting little to no loss of bond strength. Similar requirements are increasingly being placed on other electronic devices such as smartphones, tablets, notebooks, cameras, video cameras, keyboards, and touchpads.

[0015] Although the adhesive compositions known from the above-mentioned disclosures have a sufficiently high bond strength in the cured state, the resistance to chemicals (chemical resistance) is only present to a low degree, which leads to reduced bond strengths after contact of the adhesive bond with chemicals.

[0016] The present invention is therefore based on the object of eliminating or at least reducing the disadvantages of the prior art described above.

[0017] In particular, the present invention is based on the object of providing a reactively curable adhesive composition and a reactively curable adhesive tape that exhibit improved chemical resistance, for example, to perspiration, skin oils or sebum, sunscreen or cosmetic skin care products, or to a mixture of isopropanol and water. This should be reflected in particular in the bond strengths after contact with chemicals, especially the chemicals mentioned.

[0018] At the same time, the (final) bond strengths before contact with chemicals, the punchability and optionally and preferably the initial adhesive strength should be maintained at least at the same level.

[0019] In adhesive tape development, a 7:3 isopropanol / water mixture is often chosen to optimize adhesives for their chemical resistance to polar solvents. Resistance to this mixture is therefore a crucial test that must be passed before testing the full spectrum of other different chemicals. Therefore, the improved chemical resistance should be demonstrated particularly with a 7:3 isopropanol / water mixture.

[0020] It is a further object of the present invention to provide a reactively curable adhesive composition and a reactively curable adhesive tape which, in addition to sufficient or improved chemical resistance, also have high or improved bond strengths, in particular in the cured state.

[0021] These objects are achieved by the reactively curable adhesive composition according to claim 1 and the reactively curable adhesive tape of the invention. The present invention further provides a method for bonding two substrates using the reactively curable adhesive composition of the invention or the reactively curable adhesive tape of the invention.

[0022] A further object of the invention is the use of the reactively curable adhesive composition according to the invention or the reactively curable adhesive tape according to the invention as an adhesive in the manufacture of electronic, optical or precision mechanical devices.

[0023] In the context of the present invention, the terms "reactive adhesive" or "adhesive" are also used instead of "reactively curable adhesive." This applies analogously to the reactively curable adhesive tape.

[0024] All statements in the description apply to the adhesive composition according to the invention, the adhesive tape according to the invention, the method according to the invention and the use of the adhesive composition according to the invention or the adhesive tape.

[0025] The invention also encompasses all features that are the subject matter of any dependent patent claims. Furthermore, the invention encompasses combinations of individual features with one another, including combinations of different degrees of preference. Thus, for example, the invention encompasses the combination of a first feature designated as "preferred" with a second feature designated as "particularly preferred." This also encompasses subject matter designated as "embodiments" with different degrees of preference.

[0026] Surprisingly, it has been found that by (d) at least one chemical compound comprising at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring, improved chemical resistance is achieved in the adhesive composition according to the invention, which is reflected in comparatively high bond strengths after contact of the adhesive bond with the corresponding chemicals, in particular a mixture of isopropanol / water 7:3.

[0027] The reactively curable adhesive composition according to the invention contains:

[0028] (a) one or more (co-)polymers; and

[0029] (b) at least one epoxy compound; and

[0030] (c) at least one photoinitiator for initiating a cationic polymerization; and

[0031] (d) at least one chemical compound comprising at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring. Reactively curable

[0032] In the context of the present invention, a “reactively curable adhesive” is understood to mean an adhesive which cures by chemical reaction of at least one correspondingly reactive component contained therein and thereby creates the adhesive bond.

[0033] In the context of the present invention, the chemical reaction comprises in particular the cationic polymerization of the epoxy compound(s) (b), which is triggered by the at least one photoinitiator (c) after irradiation with light.

[0034] Curable adhesives in general and curable pressure-sensitive adhesives in particular are, as described at the outset, comprehensively known to the person skilled in the art from the prior art, wherein the individual components specified above are also known in isolation to the person skilled in the art and are commercially available in various variations from various suppliers, wherein preferred and exemplary representatives for the individual components are also disclosed below.

[0035] These components defined above are used as "one or more" in accordance with the understanding of one of ordinary skill in the art. The term "one or more" refers, as is customary in the industry, to the chemical nature of the respective compounds and not to their quantity. For example, the curable pressure-sensitive adhesive may comprise exclusively epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate as the polymerizable epoxy compound, which would mean that the curable pressure-sensitive adhesive comprises a plurality of the respective molecules.

[0036] In accordance with industry practice, the mass fractions are given as combined mass fractions of the one or more components, thereby expressing that the mass fraction of the correspondingly formed components taken together meets the corresponding criteria, whereby, in the absence of other information, the mass of the curable pressure-sensitive adhesive is the reference system.

[0037] The curable adhesive composition according to the invention is curable. Due to its ability to cure, the curable adhesive composition can function as a structural adhesive after curing.

[0038] The reactively curable adhesives and adhesive tapes according to the invention preferably function as structural adhesives or semi-structural adhesives after curing. According to DIN EN 923:2016-03, structural adhesives are demonstrably suitable for the production of load-bearing structures in which the adhesive bond can be subjected to a high percentage of the maximum breaking force over extended periods without failure (according to the ASTM definition: "bonding agents used for transferring required loads between adherends exposed to service environments typical for the structure involved"). They are therefore adhesives for bonds subject to high chemical and physical stresses, which contribute to the strengthening of the adhesive tapes when cured.

[0039] The term “(semi-)structural adhesive” or “(semi-)structural adhesives” encompasses “semi-structural adhesives” and “structural adhesives.” “Semi-structural adhesives” are those cured adhesives that exhibit a tensile shear strength of at least 1.0 MPa and more preferably at least about 1.5 MPa (each on steel) in the tensile shear test. “Structural adhesives” or “structural adhesives” are those cured adhesives that exhibit a particularly high tensile shear strength and that exhibit a tensile shear strength of at least 5 MPa, more preferably at least 7 MPa, and particularly preferably at least 10 MPa (each on steel) in the tensile shear test.

[0040] Chemical compound (d)

[0041] The adhesive composition according to the invention contains (d) at least one chemical compound which comprises at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring.

[0042] A “phenyl group-substituted derivative on the benzene ring” is understood to mean a phenyl group which additionally carries one or more further substituents, whereby the aromatic character of the benzene ring is retained.

[0043] The further substituent on the benzene ring is in particular and preferably selected from the group consisting of hydroxy groups (OH-), cyano groups (CN-), hydrocarbon-containing groups with preferably up to seventeen, particularly preferably up to five, very particularly preferably up to three carbon atoms, alkoxy groups with up to five, preferably up to three, particularly preferably methoxy groups, and aldehyde groups.

[0044] In the case of derivatives, the chemical compound as a whole is therefore a chemical compound that has a benzene ring with at least two substituents.

[0045] According to preferred embodiments of the invention, it is a phenyl group, i.e. a singly bonded benzene ring without additional substituents.

[0046] According to these embodiments of the invention, the chemical compound (d) thus comprises at least one phenyl group (Ph-) which is bonded to another atom but has no additional substituent on the benzene ring.

[0047] Examples of such chemical compounds (d) are in particular and preferably benzyl alcohol, cinnamaldehyde, cinnamyl alcohol, benzyl acetate, benzyl cinnamate, 2-phenoxyethyl acrylate, benzyl acrylate, 2-benzyloxyethanol and 4-benzyloxyphenol.

[0048] Benzyl cinnamate has two phenyl groups. According to further preferred embodiments of the invention, it is a derivative of a phenyl group substituted on the benzene ring, i.e., a singly bonded benzene ring with at least one additional substituent.

[0049] According to these embodiments of the invention, the chemical compound (d) thus comprises at least one phenyl group (Ph-) bonded to another atom and additionally has at least one further substituent on the benzene ring. The further substituent is preferably selected from the above-mentioned group.

[0050] Examples of such chemical compounds (d) are in particular and preferably 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, eugenol, vanillin, cardanol methacrylate and butoxynol-5-carboxylic acid.

[0051] The combined mass fraction of the chemical compounds (d) in the adhesive is preferably at least 3%, particularly preferably 3 to 15%, based on the mass of the reactively curable adhesive. This means that in the case of two or more chemical compounds (d) as defined in more detail, the total amount corresponds to the stated mass fractions.

[0052] According to particularly advantageous embodiments, the at least one chemical compound (d) comprises the at least one phenyl group or the derivative of a phenyl group substituted on the benzene ring in a structural unit selected from Bz-O-, Ph-O- and derivatives of Bz-O- and Ph-O- substituted on the benzene ring, where Bz is benzyl and thus phenylmethylene, O is oxygen and Ph is phenyl.

[0053] In particular, with a structural unit selected from Bz-O- and Ph-O-, a particularly high chemical resistance and high bonding strengths are surprisingly achieved.

[0054] It has been found to be particularly advantageous if the chemical compound (d) has a molecular mass (M) of less than 500 g / mol, in particular less than 300 g / mol, preferably less than 250 g / mol. Phenyl-containing additives in the stated molecular mass range surprisingly achieve particularly high bond strengths and particularly high chemical resistance.

[0055] Within the scope of the present invention, polymers bearing phenyl groups are in particular not chemical compounds (d), but are classified as polymers (a). Thus, the adhesive composition of the invention contains, in particular, (d) at least one chemical compound comprising at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring, wherein these chemical compounds (d) are not polymers.

[0056] According to particularly advantageous embodiments of the invention, the at least one chemical compound (d) is selected from the group consisting of benzyl alcohol (M = 108.14 g / mol), 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane (CAS 18933-99-8), phenyloxirane, phenyl glycidyl ether, benzyl cinnamate (M = 238.28 g / mol), benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol, vanillin, 2-phenoxyethyl acrylate, benzyl acrylate, cardanol methacrylate, w-phenyl oligoethylene glycol acrylate, 2-benzyloxyethanol, 4-benzyloxyphenol and butoxynol-5-carboxylic acid.

[0057] A suitable w-phenyl oligoethylene glycol acrylate is, in particular, and for example, Phenol(EO)4Acralyt, which is available under the trade name MIRAMER M144, Miwon Specialty Chemical C., Ltd.

[0058] Particularly preferably, the at least one chemical compound (d) is selected from the group consisting of benzyl alcohol (M = 108.14 g / mol), 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane (CAS 18933-99-8), phenyloxirane, phenyl glycidyl ether, benzyl cinnamate (M = 238.28 g / mol), benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol and vanillin.

[0059] Benzyl cinnamate, vanillin, benzyl alcohol and cinnamyl alcohol are particularly preferred.

[0060] One or more (co-)polymers (a)

[0061] The reactively curable adhesive composition of the invention comprises one or more (co)polymers. Those skilled in the art will understand that the (co)polymers typically play the role of film former, which is particularly important since, according to preferred embodiments, a pressure-sensitive adhesive is to be obtained.

[0062] Preference is given to a curable adhesive composition according to the invention, wherein the one or more (co)polymers are selected from the group consisting of poly(meth)acrylates, (meth)acrylate block copolymers, polyurethanes, polyvinyl acetals, such as polyvinyl butyral, polysiloxanes, synthetic rubbers, polyesters, phenoxy polymers, polyvinyl alcohols, polyvinyl alcohol copolymers, and alkene-vinyl ester copolymers, preferably selected from the group consisting of poly(meth)acrylates, (meth)acrylate block copolymers, phenoxy polymers, polyvinyl alcohols, polyvinyl alcohol copolymers, polyvinyl acetals, such as polyvinyl butyral, and ethylene-vinyl acetate copolymers (EVA or EVAC, poly(ethylene-co-vinyl acetate)), in particular selected from the group consisting of poly(meth)acrylates, (meth)acrylate block copolymers and ethylene-vinyl acetate copolymers.

[0063] Additionally or alternatively, other block copolymers can be used as (co)polymers in addition to (meth)acrylate block copolymers.

[0064] Examples of block copolymers, in particular (meth)acrylate block copolymers, are disclosed in the documents US 201 1003947 A1 , US 20080200589 A1 , US 2007078236 A1 , US 2007078236 A1 , US 2012196952 A1 , US 2016032157 A1 , US 2008146747 A1 and US 2016230054 A1.

[0065] According to particularly advantageous embodiments, at least one poly(meth)acrylate is contained as (co)polymer (a).

[0066] The poly(meth)acrylate can in principle be any poly(meth)acrylate known to the person skilled in the art which is suitable for adhesives and adhesive tapes.

[0067] According to the invention, the term "poly(meth)acrylate" encompasses polymers based on acrylic acid esters, as well as those based on acrylic acid and methacrylic acid esters, and those based on methacrylic acid esters. The terms "(meth)acrylic acid ester" and "(meth)acrylate" encompass both acrylic acid esters and methacrylic acid esters, or both acrylates and methacrylates, respectively.

[0068] The monomer composition to which the poly(meth)acrylate(s) of the reactive adhesive are attributed typically consists of up to 15 different monomers. Preferably, the monomer composition consists of up to 5 different monomers, more preferably of 4 different monomers, and even more preferably of one to three different monomers.

[0069] According to particularly preferred embodiments, the monomer composition to which the poly(meth)acrylate or poly(meth)acrylates of the reactive adhesive are attributable consists of 3 different monomers.

[0070] According to further particularly preferred embodiments, the monomer composition to which the poly(meth)acrylate or poly(meth)acrylates of the reactive adhesive are attributable consists of one monomer. According to the above embodiments, in particular in which the monomer composition consists of one, two or three monomers, the one or at least one monomer is preferably selected from the group, hereinafter referred to as Group 1, consisting of benzyl acrylate, phenyl acrylate, 2-phenylethyl acrylate, 3-phenylpropyl acrylate, 4-phenylbutyl acrylate, 5-phenylpentyl acrylate, 6-phenylhexyl acrylate, benzyl methyl acrylate, phenyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate,

[0071] 4-Phenylbutylmethacrylat, 5-Phenylpentylmethacrylat, 6-Phenylhexylmethacrylat, 2-Phenoxyethylacrylat, 2-Phenoxydiethyleneglycolacrylat, 2-Phenoxytriethyleneglycolacrylat, 2-Phenoxytetraethyleneglycolacrylat, 2-Phenoxypentaethyleneglycolacrylat, 2-phenoxyhexaethyleneglycolacrylat, 2-Phenoxyheptaethyleneglycolacrylat, 2-Phenoxyoctaethyleneglycolacrylat, 2-Phenoxynonaethyleneglycolacrylat, 2-Phenoxydecaethyleneglycolacrylat, 2-Phenoxyethylmethacrylat, 2-Phenoxydiethyleneglycolmethacrylat, 2-Phenoxytriethyleneglycolmethacrylat, 2-Phenoxytetraethyleneglycolmethacrylat, 2-Phenoxypentaethyleneglycolmethacrylat, 2-Phenoxyhexaethyleneglycolmethacrylat, 2-Phenoxyheptaethyleneglycolmethacrylat, 2-Phenoxyoctaethyleneglycolmethacrylat, 2-Phenoxynonaethyleneglycolmethacrylat, 2-Phenoxydecaethyleneglycolmethacrylat, 4-tert.-Butylphenylacrylat,

[0072] 4-tert.-Butylphenylmethacrylat, 2-(4-tert.-Butyl)phenoxyethylacrylat, 2-(4-tert.- Butyl)phenoxydiethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxytriethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxytetraethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxypentaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxyhexaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxyheptaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxyoctaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxynonaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxydecaethyleneglycolacrylat, 2-(4-tert.-Butyl)phenoxyethylmethacrylat, 2-(4-tert.-Butyl)phenoxydiethyleneglycolmethacrylat, 2-(4-tert.-Butyl)phenoxytriethyleneglycolmethacrylat,

[0073] 2-(4-tert.-Butyl)phenoxytetraethyleneglycolmethacrylat,

[0074] 2-(4-tert.-Butyl)phenoxypentaethyleneglycolmethacrylat,

[0075] 2-(4-tert.-Butyl)phenoxyhexaethyleneglycolmethacrylat,

[0076] 2-(4-tert.-Butyl)phenoxyheptaethyleneglycolmethacrylat,

[0077] 2-(4-tert-butyl)phenoxyoctaethylene glycol methacrylate,

[0078] 2-(4-tert-butyl)phenoxynonaethylene glycol methacrylate,

[0079] 2-(4-tert-butyl)phenoxydecaethylene glycol methacrylate. Particularly preferred is the one or at least one monomer selected from the group consisting of benzyl acrylate, phenyl acrylate, benzyl methacrylate, phenyl methacrylate, 2-phenoxyethyl acrylate, and 2-phenoxyethyl methacrylate.

[0080] According to preferred embodiments in which the monomer composition consists of one monomer, the monomer is preferably selected from the group consisting of phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, and benzyl methacrylate. Benzyl acrylate is most preferred.

[0081] According to preferred embodiments in which the monomer composition consists of three different monomers, a monomer selected from the group consisting of 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, and benzyl methacrylate is preferably included. 2-phenoxyethyl acrylate is most preferred.

[0082] According to preferred embodiments in which the monomer composition consists of two or more different monomers, the first monomer is preferably selected from the above-mentioned group 1, wherein the first monomer is particularly preferably selected from the group consisting of 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate and benzyl methacrylate.

[0083] The at least one further monomer, preferably the second and third monomer in the case of three different monomers, is or are preferably selected from the group, hereinafter referred to as Group 2, consisting of acrylic acid, 1,4-cyclohexanedimethanol monoacrylate, 2,3-dihydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, behenyl acrylate, behenyl methacrylate, cetyl acrylate, ethyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl diglycol acrylate, n-hexyl acrylate, isobutyl acrylate, isobutyl methacrylate, icosyl acrylate, isononyl acrylate, tetradecyl acrylate, methyl acrylate, methyl methacrylate, stearyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, Cyclohexyl methacrylate, (5-ethyl-1,3-dioxan-5-yl)methyl acrylate, dihydrodicyclopentadienyl acrylate, isobornyl acrylate, isobornyl methacrylate, norbornyl acrylate, 4-tert-butylcyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate,

[0084] Tert.-Butylcyclohexylmethacrylat, Kalium-3-sulphonatopropylacrylat,

[0085] 2-(0-[1 ’-Methylpropylideneamino]carboxyamino)ethylmethacrylat, 2-[(3,5-Dimethylpyrazolyl)carboxyamino]ethylmethacrylat, Ureidomethacrylat, Methacrylamid, 4-Acryloylmorpholin, Acrylnitril, N,N-Dimethylacrylamid, N-tert. -Butylacrylamid, N-

[0086] Methylolmethacrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, vinylmethyloxazolidinone, maleic anhydride and vinyl acetate. Particularly preferably, the second and third monomers are selected from the group consisting of acrylic acid, stearyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, dihydrodicyclopentadienyl acrylate, isobornyl acrylate, 1,4-cyclohexanedimethanol monoacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, tert-butylcyclohexyl methacrylate, behenyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, ethyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate,

[0087] Glycidyl methacrylate.

[0088] Particularly preferred are n-butyl acrylate, 2-ethylhexyl acrylate and methyl acrylate.

[0089] Polymers carrying phenyl groups, such as the polymer of the above-mentioned aromatic acrylate monomers, are considered (co)polymers (a) and not chemical compounds (d) in the context of the present invention.

[0090] The poly(meth)acrylate or poly(meth)acrylates are prepared in a manner known to the person skilled in the art.

[0091] In principle, all radical or radical-controlled polymerization processes can be used to produce poly(meth)acrylates, as can combinations of different polymerization processes. In addition to conventional free radical polymerization, these include, for example, ATRP, nitroxide / TEMPO-controlled polymerization, or the RAFT process. The poly(meth)acrylates can be produced by copolymerizing the (co)monomers using conventional polymerization initiators and, if appropriate, regulators. Polymerization takes place at conventional temperatures in bulk, in emulsion, for example, in water or liquid hydrocarbons, or in solution. Polymerization can be carried out in polymerization reactors, which are generally equipped with a stirrer, several feed vessels, a reflux condenser, heating, and cooling, and are designed for operation under N2 atmosphere and overpressure.Radical polymerization is carried out in the presence of one or more organic solvents and / or in the presence of water, or in bulk. The aim is to keep the amount of solvent used as low as possible. The polymerization time is typically between 6 and 48 hours, depending on conversion and temperature.

[0092] For solvent polymerization, preferred solvents are esters of saturated carboxylic acids (e.g., ethyl acetate), aliphatic hydrocarbons (e.g., n-hexane or n-heptane), ketones (e.g., acetone or methyl ethyl ketone), special-boiling-point spirit, or mixtures of these solvents. A solvent mixture of acetone and isopropanol is preferred, with the isopropanol content being between 1 and 10 percent by weight. Conventional free-radical-forming compounds, such as peroxides and azo compounds, are usually used as polymerization initiators. Initiator mixtures can also be used. Thiols can also be used as regulators during polymerization to lower molecular weight and reduce polydispersity. Other polymerization regulators that can be used include alcohols and ethers.

[0093] In one embodiment, the poly(meth)acrylates are obtained via the so-called "syrup process." For this purpose, the monomer composition is prepolymerized to a syrup in a preliminary step. This syrup is then used in the formulation of the reactive adhesive and, after the coating step, is allowed to react completely, for example, with light of a wavelength that does not activate the cationic initiator. The adhesive tapes of the invention can be obtained by this process.

[0094] According to particularly advantageous embodiments, at least one (meth)acrylate block copolymer is present as (co)polymer (a).

[0095] The (meth)acrylate block copolymers can in principle be any (meth)acrylate block copolymers known to the person skilled in the art.

[0096] According to the expert's understanding, (meth)acrylate block copolymers consist of poly(meth)acrylate blocks and thus of building units derived from (meth)acrylate monomers, whereby the term (meth)acrylate encompasses acrylates and methacrylates according to the expert's understanding. It is preferred in this respect if the (meth)acrylate block copolymers and the corresponding poly(meth)acrylate blocks were produced predominantly or even substantially entirely from (meth)acrylate monomers and thus consist predominantly or even substantially entirely from the correspondingly derived monomer units.

[0097] In the context of the present invention, the term "poly(meth)acrylate" for the poly(meth)acrylate blocks encompasses, in accordance with the expert's understanding, polyacrylates and polymethacrylates, as well as copolymers of these polymers. Poly(meth)acrylates or the corresponding poly(meth)acrylate blocks can, in principle, contain minor amounts of monomer units that are not derived from (meth)acrylates, with (meth)acrylic acid, in particular, being used as an additional constituent, which, strictly speaking, is not a "(meth)acrylate" in the narrower sense.For the purposes of the present invention, a "poly(meth)acrylate" is understood to mean a (co)polymer whose monomer base consists of 80% or more by mass, preferably 90% or more, particularly preferably 95% or more, and very particularly preferably essentially 100%, of monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters, based on the mass of the monomer base. The mass fraction of acrylic ester and / or methacrylic ester is preferably 50% or more, particularly preferably 70% or more, and very particularly preferably 90% or more.

[0098] Preferably, the at least one (meth)acrylate block copolymer comprises at least one so-called hard block P(A) and at least one so-called soft block P(B). Each block P(A) and P(B) is preferably a homopolymer of a (meth)acrylate.

[0099] Hard blocks P(A) are preferably polymers of (meth)acrylates having a glass transition temperature of 30 °C or more, particularly preferably of 60 °C or more, very particularly preferably of 70 °C or more, again preferably of 90 °C or more.

[0100] Soft blocks P(B) are preferably polymers of (meth)acrylates with a glass transition temperature of less than 20 °C, particularly preferably less than 0 °C, and even more preferably less than -20 (minus twenty) °C.

[0101] In the context of the present invention, the glass transition temperature of polymers or of polymer blocks in block copolymers is determined by means of differential scanning calorimetry (DSC), as described in DIN EN ISO 11357. For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 pL) and sealed with a perforated lid. A DSC 204 F1 from Netzsch is used for the measurement. The measurement is carried out under nitrogen for inerting. The sample is first cooled to -150 °C, then heated at a heating rate of 10 K / min to +150 °C and cooled again to -150 °C. The subsequent second heating curve is again run at 10 K / min, and the change in heat capacity is recorded. Glass transitions are detected as steps in the thermogram. The determination of the glass transition temperature from the DSC measurements is easily possible for the person skilled in the art and is described in more detail in EP 2832811 A1, for example.

[0102] Monomers of the hard block(s) P(A) are preferably selected from the group consisting of methyl methacrylate, methyl acrylate, t-butyl acrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, isobornyl acrylate, isobornyl methacrylate, dihydrodicyclopentadienyl acrylate, hydroxyethyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, glycidyl methacrylate, ethyl methacrylate, and benzyl methacrylate. According to particularly advantageous embodiments, at least one hard block is comprised, which is a homopolymer of methyl methacrylate (MMA).

[0103] Monomers of the soft block(s) P(B) are preferably selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, i-octyl acrylate, 2-phenoxyethyl acrylate, propylheptyl acrylate, ethyl acrylate, lauryl acrylate, lauryl methacrylate, hydroxyethyl acrylate, methoxyethyl acrylate, heptadecyl methacrylate, heptadecyl acrylate, ethylene glycol acrylate and stearyl methacrylate.

[0104] According to particularly advantageous embodiments, at least one soft block is included, which is a homopolymer of n-butyl acrylate (BA).

[0105] According to further advantageous embodiments, at least one soft block is included, which is a copolymer of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA).

[0106] According to particularly advantageous embodiments, the (meth)acrylate block copolymer is a triblock copolymer having the block sequence P(A)-P(B)-P(A), where P(A) and P(B) stand for hard and soft blocks as defined above.

[0107] The two A blocks of the (meth)acrylate block copolymers of type ABA are characterized by a common criterion: their ability to be produced from the same A monomers, and preferably also by a glass transition temperature criterion. Those skilled in the art will understand that the A blocks are very similar in terms of their production, but do not have to be exactly identical due to the nature of the polymerization processes used for production, particularly when two or more different A monomers are used. This applies analogously to the A and B blocks and also to the (meth)acrylate block copolymers themselves, since those skilled in the art in the field of polymeric materials would refer to block copolymers that differ from one another with regard to the A and B blocks only within the scope of production-related variations as a common material, i.e., as a (meth)acrylate block copolymer.Accordingly, the A blocks do not differ, or differ only slightly, with regard to their glass transition temperatures. This therefore relates to a curable adhesive according to the invention, wherein the poly(meth)acrylates of the A blocks are preparable by polymerizing the same A monomer composition from A monomers, wherein the A blocks are preferably substantially identical. An additional or alternative example in this regard is a curable pressure-sensitive adhesive according to the invention, wherein the two A blocks are poly(meth)acrylates whose glass transition temperatures differ by less than 5°C, preferably by less than 3°C, particularly preferably by less than 1°C. In the inventors' opinion, it is generally preferable to embody the A blocks as polymethacrylates and to use polyacrylates for the B blocks. Consequently, preference is given to a curable adhesive according to the invention wherein the A blocks are methacrylate polymers and the B block is an acrylate polymer.Very particular preference is given to a curable adhesive composition in which the A blocks are polymethyl methacrylates and the B block is a poly(n-butyl acrylate), or poly(2-ethylhexyl acrylate) or a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate.

[0108] Preferably, P(A) is a homopolymer of MMA and P(B) is a homopolymer of BA or a copolymer of BA and 2-EHA, with a homopolymer of BA being particularly preferred as a soft block.

[0109] A suitable (meth)acrylate block copolymer is available, for example, under the trade name KURARITY™ LA 3320.

[0110] The (meth)acrylate block copolymer(s) are otherwise prepared in a manner known to the person skilled in the art.

[0111] With regard to the mass fractions of the A and B blocks, the inventors consider it particularly advantageous not to select too low a mass fraction of the A blocks. Based on the inventors' experiments, the presence of a sufficient proportion of the hard block in particular appears to have a particularly positive influence on the advantageous bond strength at elevated temperatures, which is particularly surprising since the exclusive use of PMMA did not result in an improvement in this respect. In the inventors' opinion, a curable adhesive composition according to the invention is preferred, wherein the combined mass fraction of the A blocks is 15% or more, preferably 25% or more, more preferably 35% or more, most preferably 45% or more, based on the mass of the (meth)acrylate block copolymers.

[0112] With regard to the length of the (meth)acrylate block copolymers, a curable adhesive is preferred, wherein the number-average molecular weights M n the (meth)acrylate block copolymers is in the range from 20,000 to 1,000,000 g / mol, preferably in the range from 30,000 to 500,000 g / mol, particularly preferably in the range from 50,000 to 350,000 g / mol.

[0113] According to particularly advantageous embodiments, at least one alkene-vinyl ester copolymer is present as (co)polymer (a).

[0114] Alkene-vinyl ester copolymers with a comparatively high vinyl ester content are particularly preferred, since corresponding alkene-vinyl ester copolymers result in an advantageously low degree of crystallinity, which has proven particularly advantageous in the inventors' experiments. Preferably, the at least one alkene-vinyl ester copolymer is an ethylene-vinyl ester copolymer with a vinyl ester content of 60% or more, in particular 70% or more, based on the mass of the copolymers.

[0115] The ethylene-vinyl ester copolymer is preferably an ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of 60% or more, preferably 70% or more, based on the mass of the copolymer. A suitable ethylene-vinyl acetate copolymer is available from Arlanxeo under the trade name Levamelt® 700 with a vinyl acetate content of 70% by weight.

[0116] The number average molecular masses M nof the (co)polymers, in particular of all of the poly(meth)acrylates mentioned, are, according to preferred embodiments, in a range from 50,000 to 10,000,000 g / mol, particularly preferably in a range from 100,000 to 5,000,000 g / mol, very particularly preferably in a range from 150,000 to 2,000,000 g / mol. The data on the number-average molar mass M n refer to the determination by gel permeation chromatography (GPC). The determination is carried out on 100 μl of a clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1 vol. % trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C. A PSS-SDV column, 5 μm, 10 3 Ä, 8.0 mm * 50 mm (information here and below in the order: type, particle size, porosity, inner diameter * length; 1 Ä = 10 -10 m). For separation, a combination of columns of type PSS-SDV, 5 pm, 10 3 Ä and 10 5 Ä and 10 6Ä with 8.0 mm * 300 mm each were used (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate was 1.0 ml per minute. Calibration was carried out using the commercially available ReadyCal kit Poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz, or Agilent. This was universally converted to polymethyl methacrylate (PMMA) using the Mark-Houwink parameters K and alpha, so that the data were given in PMMA mass equivalents. Calibration was carried out for polyacrylates against PMMA standards (polymethyl methacrylate calibration) and for other materials (resins, elastomers) against PS standards (polystyrene calibration).

[0117] It is additionally or alternatively preferred that the (co)polymer(s) contained have(s) at least 100, preferably at least 500, particularly preferably at least 1000, repeating units, i.e. monomer building blocks.

[0118] Regardless of the specific selection of the (co)polymers, preference is given to a reactively curable adhesive according to the invention, wherein the combined mass fraction of the (co)polymers in the curable adhesive is in the range from 20 to 55%, preferably in the range from 20 to 50%, particularly preferably in the range from 25 to 50%, very particularly preferably in the range from 25 to 50%, extremely preferably in the range from 35 to 50%, based on the mass of the curable adhesive.

[0119] At least one epoxy compound (b)

[0120] The curable adhesive composition according to the invention comprises, in addition to the (co)polymers, at least one epoxy compound. The epoxy compounds together form the part of the curable adhesive composition frequently referred to by those skilled in the art as the reactive resin. The at least one epoxy compound (d) is thus, in particular, a polymerizable epoxy compound. The term "polymerizable" refers, in accordance with the expert's understanding, to the ability of these compounds to enter into a polymerization reaction, optionally after suitable activation. In the case of polymerizable epoxy compounds, the polymerizability is enabled, for example, by the epoxy groups.

[0121] The conversion of the epoxy compounds during the curing reaction of the reactive adhesive occurs primarily through cationic polymerization via the epoxy groups. Epoxy compounds can be used to produce adhesives with particularly high shear strength. Furthermore, the crosslinking reactions are easy to initiate and manage. In the uncured state, reactive adhesives produced using epoxy compounds have sufficient storage stability.

[0122] In accordance with the expert understanding, epoxy compounds are those compounds that carry at least one oxirane group.

[0123] They can be aromatic or aliphatic, especially cycloaliphatic, in nature. Epoxy compounds can include both monomeric and oligomeric or polymeric epoxy compounds. Epoxy compounds often have an average of at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule. The "average" number of epoxy groups per molecule is defined as the number of epoxy groups in the epoxy-containing material divided by the total number of epoxy molecules present.

[0124] The oligomeric or polymeric epoxy compounds mostly include linear polymers with terminal epoxy groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol), polymers with backbone oxirane units (e.g., polybutadiene polyepoxide), and polymers with side epoxy groups (e.g., a glycidyl methacrylate polymer or copolymer). By reacting epoxy resins with CTBN, so-called epoxy-terminated nitrile rubbers (ETBN) are obtained. Such ETBNs are commercially available, for example, from Huntsman International under the name HYPRO ETBN—such as Hypro 1300X40 ETBN, Hypro 1300X63 ETBN, and Hypro 1300X68 ETBN.

[0125] The molecular weight of the at least one epoxy compound or compounds present in the light-curing adhesive composition of the invention can vary from 58 to about 100,000 g / mol, with the molecular weight being an important variable for adjusting the dynamic viscosity. Exemplary epoxy compounds include epoxycyclohexanecarboxylates, such as 4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. Further examples of epoxy compounds are disclosed, for example, in US Pat. No. 3,117,099. Other suitable epoxy compounds that are particularly useful in the practice of this invention include glycidyl ether monomers, as disclosed, for example, in US Pat. No. 3,018,262.Examples include the glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin (e.g., the diglycidyl ether of 2,2-bis(2,3-epoxypropoxyphenol)propane). In particular, diglycidyl ethers of bisphenols, such as bisphenol A (4,4'-(propane-2,2-diyl)diphenol) and bisphenol F (bis(4-hydroxyphenyl)methane), and hydrogenated variants thereof. Such reaction products are commercially available in various molecular weights and aggregate states (e.g., so-called Type 1 to Type 10 BADGE resins). Typical examples of liquid bisphenol A diglycidyl ethers are Epikote 828, DER331 and Epon 828, and examples of liquid hydrogenated bisphenol A diglycidyl ethers is Eponex 1510. Typical solid BADGE resins are Araldite GT6071, GT7072, Epon 1001 and DER 662. Other reaction products of phenols with epichlorohydrin are the phenol and cresol novolac resins such asthe Epiclon types or Araldite EPN and ECN types (e.g., ECN1273). Other suitable epoxy compounds are epoxy resins obtained from renewable raw materials, such as oils, such as epoxidized linseed oil, epoxidized soybean oil, or from cashew shells, such as epoxidized cardanols, or epoxy resins containing glycerin, such as bisphenol A, which is reacted with epichlorohydrin, which is derived from glycerin.

[0126] Preference is given to a reactively curable adhesive composition according to the invention which contains one or more polymerizable epoxy compounds which are selected from the group consisting of polymerizable epoxy compounds having a weight-average molecular weight Mw, measured by GPC, in the range from 300 to 2000 g / mol, preferably in the range from 300 to 1500 g / mol, particularly preferably in the range from 350 to 1300 g / mol.

[0127] It is particularly preferred, additionally or alternatively, for the reactively curable adhesive to contain one or more polymerizable epoxy compounds selected from the group consisting of polymerizable epoxy compounds with a weight-average molecular weight Mw, measured by GPC, of ​​2000 g / mol or less. The polymerizable epoxy compounds can, for example, be aromatic or aliphatic, in particular cycloaliphatic, in nature.

[0128] It is preferred that the at least one epoxy compound (b) is selected from the group consisting of cycloaliphatic epoxy resins, such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bisphenol A diglycidyl ether (BADGE) resins, hydrogenated bisphenol A diglycidyl ether (BADGE) resins, epoxy-terminated nitrile rubbers (ETBN) and epoxy-terminated butadiene rubbers (EBN), particularly preferably from the group consisting of bisphenol A diglycidyl ethers and hydrogenated bisphenol A diglycidyl ethers.

[0129] Also preferred is a reactive pressure-sensitive adhesive tape according to the invention, wherein the reactive adhesive comprises two or more epoxy compounds, in particular epoxy resins, wherein at least one of the epoxy compounds is a solid; in particular a solid having a softening temperature of at least 45°C, or a highly viscous substance, preferably having a dynamic viscosity at 25°C of 50 Pa s or more, particularly preferably 100 Pa s or more, especially preferably 150 Pa s or more (measured according to DIN 53019-1 from 2008; 25°C, shear rate 1 s-1).

[0130] Particularly preferred is a reactively curable adhesive composition according to the invention which comprises two or more epoxy compounds, in particular epoxy resins, wherein at least one epoxy compound (b1) is a liquid with a dynamic viscosity of 40 Pa s or less, preferably 20 Pa s or less, at 25°C, and at least one epoxy compound (b2) is a solid or a highly viscous substance with a dynamic viscosity of 50 Pa s or more at 25°C. Reactive adhesive compositions with liquid and solid or highly viscous epoxy compounds exhibit particularly balanced adhesive properties in the uncured state.

[0131] In a preferred embodiment, in the reactive adhesive, the weight ratio of the total of the liquid epoxy compounds (b1), whose dynamic viscosity at 25 °C is 40 Pa s or less, to the total of the solid epoxy compounds (b2) (solid with a softening temperature of at least 45 °C or a highly viscous substance with a dynamic viscosity at 25 °C of 50 Pa s or more) is 1:2 to 5:1 and more preferably 1.5:1 to 3:1. Surprisingly, it has been found that reactive pressure-sensitive adhesives which contain 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, which is very frequently used in light-curing epoxy adhesives, show lower chemical resistance in most cases. For this reason, the reactive adhesive of the reactive pressure-sensitive adhesive tape according to the invention preferably contains bisphenol A diglycidyl ether or hydrogenated bisphenol A diglycidyl ether or mixtures thereof as liquid epoxy compound.

[0132] In a preferred embodiment, in the reactive adhesive, the weight ratio of the total of the liquid epoxy compounds (b1) whose dynamic viscosity at 25 °C is 40 Pa s or less to the total of the solid epoxy compounds (b2) (solid with a softening temperature of at least 45 °C or a highly viscous substance with a dynamic viscosity at 25 °C of 50 Pa s or more) is 1:2 to 5:1 and more preferably 1.5:1 to 3:1, wherein the liquid epoxy compounds (b1) comprise at least one or more liquid hydrogenated bisphenol A diglycidyl ethers.

[0133] Regardless of the specific selection of the polymerizable epoxy compounds, preference is given to a curable adhesive according to the invention, wherein the combined mass fraction of the epoxy compounds, in particular polymerizable epoxy compounds, in the curable adhesive is in the range from 30 to 60%, preferably in the range from 30 to 55%, particularly preferably in the range from 35 to 55%, very particularly preferably in the range from 35 to 50%, based on the mass of the curable adhesive.

[0134] At least one photoinitiator for initiating a cationic polymerization (c)

[0135] With the presently proposed use of at least one epoxy compound in the reactive adhesive, polymerization occurs primarily by cationic polymerization. Therefore, the reactive adhesive includes an initiator for cationic polymerization. Since the polymerization is intended to be radiation-activated, the corresponding light-activated initiator is referred to as a photoinitiator.

[0136] A photoinitiator is a compound that can initiate a chemical reaction under the influence of high-energy radiation. The photoinitiator is preferably a UV initiator. UV initiators are generally known to those skilled in the art.

[0137] Sulfonium, iodonium, and metallocene-based systems are particularly suitable as initiators for such cationic radiation-based, i.e., often UV-induced, curing of epoxy compounds. For examples of sulfonium-based cations, see US Pat. No. 6,908,722 B1.

[0138] Examples of anions that serve as counterions for the above-mentioned cations are tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate,

[0139] Examples include hexachloroantimonate, tetracispentafluorophenyl borate, tetracis(pentafluoromethylphenyl)borate, bi(trifluoromethylsulfonyl)amide, and tris(trifluoromethylsulfonyl)methide. Chloride, bromide, or iodide are also conceivable as anions, particularly for iodonium-based initiators, although initiators that are essentially free of chlorine and bromine are preferred. A powerful example of such a system is triphenylsulfonium hexafluoroantimonate. Further suitable initiators are disclosed, for example, in US 3,729,313 A, US 3,741,769 A, US 4,250,053 A, US 4,394,403 A, US 4,231,951 A, US 4,256,828 A, US 4,058,401 A, US 4,138,255 A and US 2010 / 063221 A1.

[0140] Specific examples of usable sulfonium salts are in particular triarylsulfonium salts, which can be substituted with aceto or methyl groups, for example optionally substituted accordingly: Triarylsulfonium hexafluorophosphate,

[0141] T riarylsulfoniumtetrakispentafluorophenylborat, T riphenylsulfoniumhexafluoroarsenat,

[0142] T riphenylsulfoniumhexafluoroborat, T riphenylsulfoniumtetrafluoroborat,

[0143] Triphenylsulfoniumtetrakis(pentafluorobenzyl)borat, Methyldiphenylsulfonium-itetrafluoroborat, Methyl-idi-iphenylsulfoniumtetrakis-

[0144] (pentafluorobenzyl)-borat, Dimethylphenyl-isulfoniumhexafluorophosphat,

[0145] T riphenyl-isulfoniumhexafluoro-iphosphat, T riphenyl-sulfoniumhexa-ifluoroantimo-inat,

[0146] Diphenylnaphthylsulfoniumhexafluoro-iarsenat, Tritolyl-isulfoniumhexa-fluorophosphat, Anisyldiphenyl-isulfonium-ihexafluoro-iantimonat, 4-Butoxyphenyldiphenyl-iSulfoniumtetra-iflu-oroborat, 4-Chlorophenyl-idiphenylsulfonium-ihexafluoroantimonat, Tris-(4-phenoxyphe-inyl)-sulfonium-hexafluoro-iphosphat, Di-(4-ethoxyphenyl)- methylsulfonium-ihexafluoroarse-inat, 4-Acetylphenyl-diphenylsulfonium-itetrafluoroborat, 4-Acetylphenyl-idiphenyl-iSulfonium-itetrakis-(pentafluorobenzyl)-borat, Tris-(4-thiomethoxyphenyl)-sulfonium-ihexa-ifluoro-iphos-iphat, Di-(methoxysulfonylphenyl)- methylsulfonium-hexafluoro-iantimonat, Di-(methoxy-inaphthyl)- methylsulfoniumtetrafluoro-iborat, Di-(methoxy-inaphthyl)-methylsulfo-iniumetrakis-(penta- fluorobenzyl)-borat, Di-(carbomethoxy-iphenyl)-methylsulfoniumhexa-fluorophosphat, (4-Octyloxyphenyl)-diphenyl-iSulfonium-itetrakis-(3,5-bis-trifluoromethyl-iphenyl)-borat, Tris-[4-(4-acetylphenyl)-thio-iphenyl]-sulfoniumtetrakis-(pentafluorophenyl)-borat,Tris-(dodecyl-phenyl)-sulfoniumtetrakis-(3,5-bis-trifluoromethylphenyl)-borat, 4-AceHamidphenyldiphe-nylsulfonium-tetrafluoroborat, 4-Acetamidphenyldiphenylsulfoniumtetra-ikis-(penta-ifluoro-benzyl)-borat, Dimethyl- naphthylsulfonium-ihexafluoro-iphosphat, Trifluoro^methyl-idiphenyl- sulfoniumtetrafluoroborat, Trifluoro-methyldiphenyl-isulfonium-itetrakis-(penta-ifluorobenzyl)- borat, Phenyl-imethylbenzylsulfonium-ihexafluoro-phosphat, 5-Methylthian-ithreniumhexa- fluorophosphat, 10-Phenyl-9,9-dimethyHthioxanthenium-hexafluorophosphat, 10-Phenyl-9- oxothioxanthenium-itetrafluoro-iborat, 10-Phenyl-9-oxothioxantheniumtetrakis-(pentafluoro- benzyl)-borat, 5-Methyl-10-oxothianthreniumtetrafluoroborat, 5-Methyl-10-oxothianthreni- umtetrakis-(pentafluorobenzyl)-borat und 5-Methyl-10,10-dioxothian-ithrenium- hexa-ifluorophosphat.,

[0147] Specific examples of usable iodonium salts are 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,

[0148] 2,2'-Diphenyliodonium-itetra-fluoroborat, Di-(2,4-dichlorphenyl)-iodoniumhexafluorophosphat, Di-(4-bromphenyl)-iodoniumhexafluorophosphat, Di-(4-methoxyphenyl)- iodoniumhexa-ifluoro-iphosphat, Di-(3-carboxyphenyl)-iodoniumhexafluorophosphat, Di-(3-methoxycarbonylphenyl)-iodoniumhexafluorophosphat, Di-(3-methoxysulfonyl-iphenyl)- iodoniumhexafluorophosphat, Di-(4-acetamidophenyl)-iodonium-ihexa-ifluoro-phosphat, Di-(2-benzothienyl)-iodoniumhexafluorophosphat, Diaryl- iodoniumtristrifluormethylsulfonylmethid wie Diphenyliodoniumhexafluoro-iantimonat, Diaryliodoniumtetrakis-(pentafluorophenyl)-borat wie Diphenyl-iiodoniumtetrakis- (pentafluorophenyl)-borat, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]- phenyliodoniumhexafluoroantimonat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-pheny- liodoniumtrifluoromethylsulfonat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium- hexafluorophosphat, [4-[(2-Hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodoniumtetrakis- (pentafluorophenyl)-borat,Bis-(4-tert-butylphenyl)-iodonium-ihexa-ifluoroantimonat, Bis-(4- tert-butylphenyl)-iodoniumhexa-ifluoro-iphosphat, Bis-(4-tert-butylphenyl)- iodoniumtrifluorosulfonat, Bis-(4-tert-butylphenyl)-iodoniumtetrafluoroborat, Bis- (dodecylphenyl)-iodoniumhexa-ifluoro-iantimonat, Bis-(dodecylphenyl)- iodoniumtetrafluoroborat, Bis-(dodecyl-iphenyl)-iodonium-ihexa-ifluorophosphat, Bis-(dodecylphenyl)-iodoniumtrifluoro-imethylsulfonat, Di-(dodecylphenyl)- iodoniumhexafluoroantimonat, Di-(dodecyHphenyl)-iodoniumtriflat, Diphenyliodoniumbisulfat, 4,4'-Dichlorodiphenyl-iiodoniumbisulfat, 4,4'-Dibromodiphenyliodoniumbisulfat,

[0149] 3,3'-Dinitrodiphenyl-iiodoniumbisulfat, 4,4'-Dimethyldiphenyliodoniumbisulfat,

[0150] 4,4'-Bis-succinimido-idiphenyliodoniumbisulfat, 3-Nitrodiphenyliodoniumbisulfat,

[0151] 4,4'-Dimethoxy-idiphenyl-iiodoniumbisulfat, Bis-(dodecylphenyl)-iodoniumtetrakis-

[0152] (pentafluoro-iphenyl)-borate, (4-octyloxyphenyl)-phenyliodoniumtetrakis-(3,5-bis-trifluoro-methyl-iphenyl)-borate and (tolylcumyl)-iodoniumtetrakis-(pentafluorophenyl)-borate, and ferrocenium salts (see for example EP 0 542 716 B1 ) such as r|5-(2,4-cyclopentadien-1 -yl)-[(1,2,3,4,5,6,9)-(1-methylethyl)-benzene]-iron.

[0153] Such cationic photoinitiators are typically used individually or in combinations of two or more photoinitiators. When using photoinitiators in state-of-the-art curable adhesives, combinations with so-called sensitizers are particularly helpful for adapting the activation wavelength of the photoinitiation system to the selected emission spectrum. These combinations are disclosed, for example, in the 2010 textbook "Industrial Photoinitiators: A Technical Guide" by AW Green.

[0154] Some cationic photoinitiators, for example the photoinitiator commercially available under the trade name Deuteron UV 1242, only react at relatively short wavelengths in the range of 220 to 250 nm. Activation using a typical UV LED, which would be highly preferred from an application-related perspective, is not possible here, or at least not efficiently, since the emission maximum of typical UV LEDs is at a wavelength of approximately 365 nm. In order to nevertheless activate these cationic photoinitiators with typical UV LEDs, the concept of "radical promoter cationic curing" described in the literature is used. For this purpose, a radical initiator, such as those commercially available under the trade name Omnirad BDK or Irgacure 651, is added as a sensitizer. This radical initiator decomposes upon excitation at higher wavelengths, for example at a wavelength of 365 nm, which is typical for UV LEDs.The radicals or other active species formed in this way activate the cationic initiator, which ultimately initiates the epoxy curing process. Typically, in these cases where sensitizers are used, the mass fraction of cationic photoinitiators in the curable adhesive is not more than 4% but at least 0.1%, and is preferably in the range from 0.5 to 2%. The mass fraction of sensitizers is usually not more than 3% and is preferably in the range from 0.5 to 2%. Within the scope of the present invention, the cationic photoinitiator is preferably selected from the above-mentioned groups, and in particular selected from sulfonium salts and iodonium salts.

[0155] According to particularly preferred embodiments, the combined mass fraction of cationic photoinitiators in the curable adhesive is preferably 0.5 to 7%, particularly preferably 0.5 to 4%, very particularly preferably 0.5 to 3%, again preferably 0.5 to 2%, based on the mass of the curable adhesive.

[0156] In a particularly advantageous embodiment, the cation of the photoinitiator is selected from aceto- or methyl-substituted triarylsulfonium and is commercially available, for example, under the names Omnicat 270 (IGM resins), QL 21 1 and QL212 (Quang Li Chem.), Irgacure 290 (BASF) or diaryliodonium substituted on the phenyl groups, which are commercially available, for example, under the names Omnicat 250 (IGM resins), Speedcure 939, Speedcure 938, Speedcure 937 (Arkema), Deuteron 1240, Deuteron 1242 (Deuteron).

[0157] According to particularly advantageous embodiments, at least one sulfonium salt is used as cationic photoinitiator, such as, for example and in particular, aceto-substituted triarylsulfonium hexafluorophosphate (CAS: 953084-13-4) or aceto-substituted triarylsulfonium tetrakispentafluorophenylborate or (tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate).

[0158] According to preferred embodiments, the reactively curable adhesive composition according to the invention contains

[0159] 30 to 55% of at least one (co)polymer (a);

[0160] 5 to 30%, in particular 10 to 20%, of at least one liquid epoxy compound (b1);

[0161] 5 to 30%, in particular 10 to 20%, of at least one solid epoxy compound (b2);

[0162] 0.5 to 7% of at least one photoinitiator for initiating a cationic polymerization (c);

[0163] 3 to 15% of at least one chemical compound comprising at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring (d).

[0164] According to preferred embodiments of the invention, the polymer a) of the reactively curable adhesive is substantially inert towards the at least one epoxy compound and thus the at least one reactive resin b) and the initiator c) as well as the phenyl compound d) and any other substances.

[0165] In this context, inert means that the polymerizable compounds, the initiator, and the other substances do not react with the polymer before light curing under appropriately selected conditions, especially at room temperature (23 °C). In particular, no such reaction should occur during production, processing (such as coating), and curing of the adhesive film.

[0166] The inert polymer in this sense serves to form a film-forming matrix, which serves as an inert framework for the reactive resins. This ensures that the reactive resins are not liquid but embedded in a film or foil. This ensures easier handling. The polymers underlying the film-forming matrix are capable of forming a self-supporting film through sufficient interactions between the macromolecules, for example—without wishing to unnecessarily limit the scope of the invention—by forming a network through physical and / or chemical crosslinking.

[0167] Other additives

[0168] The reactively curable adhesive composition of the invention may optionally contain further additives and / or auxiliaries known in the art. The proportion of the further additives and / or auxiliaries, if present, is preferably in a combined mass fraction in the range from 0.1 to 50%, particularly preferably in the range from 0.2 to 40%, in particular 0.2 to 20%, up to 15%, more preferably up to 10%, and most preferably up to 5%, based on the mass of the curable adhesive composition.

[0169] Other additives and / or auxiliaries include, for example, reactive monomers, fillers, dyes, nucleating agents, other photoinitiators, rheological additives (for example fumed silica), blowing agents, adhesive-enhancing additives (adhesion promoters, in particular silanes and tackifier resins), compounding agents, plasticizers and / or anti-aging, light and UV protection agents, for example in the form of primary and secondary antioxidants.

[0170] In particular and according to preferred embodiments, the proportion of fillers, such as glass beads or SiLibeads® 521 1 , is up to 50%, in particular up to 40%.

[0171] Particularly preferred additives are silane coupling agents or open-time additives. An example of a silane coupling agent is 3-trimethoxysilylpropyl methacrylate (CAS No.: 2530-85-0), available under the trade name Dynasylan® MEMO (Evonik AG, Essen, Germany). Suitable open-time additives are polyethylene glycol 400 (PEG 400) CAS: 25322-68-3 or polyethylene glycol 600 (PEG 600) CAS: 25322-68-3. As an open-time additive, the reactively curable adhesive composition of the invention preferably comprises at least one substance selected from the group consisting of polyethylene glycol (PEG), polypropylene glycol (PPG), tertiary amines, and crown ethers (such as 18-crown-6). in particular at least one substance selected from PEG having a weight-average molecular weight, determined as described above, of 400 to 10,000 g / mol, for example up to 5,000 g / mol, most preferably up to 1,000 g / mol, and in particular PEG 600.These substances ensure that, after the initiation of curing of the reactive adhesives, a so-called open time remains during which curing has not yet begun, or at least not yet begun to a significant extent. They can therefore be referred to as "open time additives." As has been shown, with the open time additives listed here, particularly for UV-curable reactive adhesives, open times of at least one minute, frequently from 1 to 5 minutes, can be achieved, with the dark reaction being completed after 24 hours at a temperature of 25°C. A reaction within the meaning of this invention is referred to as "completed" if the bond strength of the reactive pressure-sensitive adhesive tape after 24 hours is at least 2 MPa.

[0172] The reactively curable adhesive composition of the invention can in principle comprise one or more open-time additives. The above-mentioned open-time additives, if included, are preferably present in the adhesive composition in a combined mass fraction of 0.1 to 10%, particularly preferably 0.2 to 5%, in particular 0.3 to 4%.

[0173] Adhesive adhesion

[0174] For the purpose of the best possible processability by the end user, the reactive adhesive of the present invention has pressure-sensitive adhesive properties or an intrinsic pressure-sensitive adhesiveness.

[0175] The reactively curable adhesive of the invention is thus preferably a pressure-sensitive adhesive. The reactively curable adhesive tape of the invention is thus preferably a reactively curable pressure-sensitive adhesive tape.

[0176] The adhesive strength allows reliable and safe application of the reactive pressure-sensitive adhesive tapes to the substrate before curing.

[0177] A pressure-sensitive adhesive (PSA) is, in accordance with expert understanding, an adhesive that possesses pressure-sensitive adhesive properties, i.e., the ability to form a permanent bond to a substrate even under relatively light pressure. Such pressure-sensitive adhesive tapes can usually be removed from the substrate after use without leaving any residue and are generally permanently tacky even at room temperature, meaning they possess a certain viscosity and initial tack, allowing them to wet the surface of a substrate even under light pressure. The tackiness of a pressure-sensitive adhesive tape results from the fact that a pressure-sensitive adhesive is used as the adhesive.Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be viewed as an extremely viscous liquid with an elastic component, which consequently exhibits characteristic viscoelastic properties that lead to the permanent inherent tack and pressure-sensitive adhesive capacity described above. It is assumed that with corresponding pressure-sensitive adhesives, mechanical deformation leads to both viscous flow processes and the build-up of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are necessary in particular to achieve cohesion. The relationships between rheology and pressure-sensitive tack are known in the art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology", Third Edition, (1999), pages 153 to 203.

[0178] For a more precise description and quantification of the degree of elastic and viscous components, as well as the relationship between the components, the storage modulus (G') and loss modulus (G"), which can be determined using Dynamic Mechanical Analysis (DMA), are used. G' is a measure of the elastic component, G" a measure of the viscous component of a material. Both parameters depend on the deformation frequency and the temperature.

[0179] The parameters can be determined using a rheometer. The material under test is subjected to a sinusoidal oscillating shear stress, for example in a plate-on-plate arrangement. With shear stress-controlled devices, the deformation is measured as a function of time and the temporal offset of this deformation compared to the application of the shear stress. This temporal offset is referred to as the phase angle θ. The storage modulus G' is defined as follows: G' = (i / y) * cos(θ) (T = shear stress, y = deformation, θ = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G" is: G" = (T / y) • sin(θ) (T = shear stress, y = deformation, θ = phase angle = phase shift between shear stress and deformation vector).

[0180] In the context of the present invention, an adhesive is preferably understood as pressure-sensitive adhesive and thus as a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range of 10° to 10 1 rad / sec both G' and G“ are at least partly in the range of 10 3 up to 10 7 Pa. “Partially” means that at least a section of the G' curve lies within the window defined by the deformation frequency range from 10° to 10 1 rad / sec (abscissa) and the range of G' values ​​from 10 3 up to and including 10 7Pa (ordinate), and if at least one section of the G" curve also lies within the corresponding window. For simplification, the inventors define that a reactive pressure-sensitive adhesive tape in the sense of the present invention has an adhesive strength in the uncured state of at least 1 N / cm and that it can be removed almost residue-free (i.e., adhesive failure in the test). The adhesive strength is determined on steel analogously to ISO 29862:2007 (Method 3) at 23 °C and 50% relative humidity at a peel speed of 300 mm / min and a peel angle of 180°. An etched PET film with a thickness of 36 pm, as available from Coveme (Italy), is used as the reinforcing film. The bonding of a 2 cm wide measuring strip is carried out using a 4 kg rolling machine at a temperature of 23 °C. The adhesive tape is immediately after application deducted.The measured value (in N / cm) is the average of three individual measurements. Cohesive failure in this test is demonstrated by adhesives or adhesive tapes that are tacky at room temperature and whose cohesion is insufficient for residue-free removal. Such adhesives or adhesive tapes are not considered pressure-sensitive adhesives within the meaning of the invention.

[0181] Reactive curing adhesive tape

[0182] The reactively curable adhesive tape according to the invention comprises at least one layer of a reactively curable adhesive composition according to the invention.

[0183] In a preferred embodiment, the reactively curable adhesive tape of the invention consists of the layer of the reactively curable adhesive composition of the invention and has no carrier layer. This embodiment is thus a carrierless reactive transfer adhesive tape.

[0184] In a further preferred embodiment, the reactive adhesive tape is characterized in that, in addition to the adhesive layer, it also comprises a carrier layer. This includes single-sided adhesive tapes as well as double-sided adhesive tapes comprising at least one outer layer consisting of the reactive adhesive composition of the invention.

[0185] In the case of double-sided adhesive tapes, it is preferred that they have a 3-layer structure (reactive adhesive - carrier layer - reactive adhesive), whereby the reactive adhesive on both sides of the carrier layer is preferably the same reactive adhesive.

[0186] The term "adhesive tape" is familiar to those skilled in the field of adhesive technology. Within the context of the present invention, the term "tape" refers to all thin, flat structures, i.e., structures with a predominantly two-dimensional extension, in particular films, film sections, and labels, preferably tapes with an extended length and a limited width, as well as corresponding tape sections.

[0187] The carrier layer usually refers to the layer of such a multilayer adhesive tape that largely determines the mechanical and physical properties of the adhesive tape, such as tear resistance, stretchability, insulation, or resilience. Common carrier materials are familiar to those skilled in the art and include fabrics, scrims, and plastic films, such as PET and polyolefin films. However, the carrier layer itself can also be pressure-sensitively adhesive.

[0188] In the reactive adhesive tapes according to the invention, especially pressure-sensitive adhesive tapes, the adhesive layers can be covered with a so-called release liner for transport, storage, or die-cutting. This release liner enables, for example, trouble-free unwinding and protects the (pressure-sensitive) adhesive from contamination. Such release liners typically consist of a plastic film (e.g., PET or PP) siliconized on one or both sides, or a siliconized paper carrier.

[0189] The layer thickness of the adhesive layer made of the reactive adhesive in the reactive adhesive tape according to the invention is preferably 5 μm to 400 μm (measured using a commercially available thickness gauge, e.g., DM 2000 from Wolf Messtechnik GmbH). More preferred is a layer thickness of 10 μm to 300 μm, even more preferred is a layer thickness of 30 μm to 200 μm, and most preferred is a layer thickness of 50 μm to 110 μm. Greater layer thicknesses, e.g., of up to 1000 μm, are conceivable and can be realized using the reactive adhesive of the present invention. This is especially the case when components with larger gaps are installed. Preferred layer thicknesses here are up to 1000 μm, more preferably up to 900 μm, and even more preferably up to 800 μm. Such adhesive tapes are often provided with a carrier layer inside to ensure internal strength before curing, so that in exceptional cases activation on both sides may be necessary.

[0190] Particularly for applications in the electronics industry, where delicate punched parts are required, adhesive tapes with a carrier layer are preferred and are preferably in the form of double-sided adhesive tapes with a three-layer structure (reactive adhesive - carrier layer - reactive adhesive) and preferably in layer thicknesses between 40 μm and 400 μm. The reactive adhesive on both sides of the carrier layer is preferably the same reactive adhesive. Starting from the reactive adhesive according to the invention and the reactive adhesive tape according to the invention, the use of the reactively curable adhesive according to the invention or the reactively curable adhesive tape according to the invention for bonding two or more components or substrates, preferably at room temperature, by curing the reactive adhesive is also disclosed.

[0191] The process according to the invention for bonding two substrates, preferably at room temperature, using the reactively curable adhesive composition according to the invention or the reactively curable adhesive tape according to the invention, which in this process is designed as a double-sided adhesive tape, comprises the following steps

[0192] A) Applying the reactively curable adhesive or the reactively curable adhesive tape to a first substrate

[0193] B) Activation of the reactive curing adhesive or the reactive curing adhesive tape by irradiation with UV light, preferably from a LIV-LED lamp.

[0194] C) Joining a second substrate to which the activated reactive curable adhesive or the activated reactive curable adhesive tape is applied.

[0195] In this process, irradiation is preferably carried out at a wavelength of 365 nm or 385 nm, more preferably at 365 nm. Suitable LIV-LED lamps are available from specialist retailers, for example the LED Cube from Hönle (Dr. Hönle AG, Gilching, Germany). Furthermore, the process according to the invention can be characterized in that the activation lasts less than 45 seconds, preferably less than 30 seconds, more preferably less than 15 seconds, even more preferably less than 10 seconds, in particular less than 7 seconds. In particular, an activation / irradiation time of less than 15 seconds or 10 seconds has proven to be excellently suitable in this process and is particularly advantageous because it enables very short cycle times in industrial processes.

[0196] A further subject matter of the invention is the use of the reactively curable adhesive composition according to the invention or the reactively curable adhesive tape according to the invention as an adhesive in the production of electronic, optical or precision mechanical devices, in particular portable electronic, optical or precision mechanical devices.

[0197] Such portable devices include in particular:

[0198] Still cameras, digital cameras, photographic accessories (such as light meters, flash units, apertures, camera housings, lenses, etc.), film cameras, video cameras, small computers (mobile computers, pocket computers, calculators), laptops, notebooks, netbooks, ultrabooks, tablet computers, handhelds, electronic diaries and organizers (so-called "electronic organizers" or "personal digital assistants", PDAs, palmtops), modems;

[0199] Computer accessories and control units for electronic devices, such as mice, drawing pads, graphics tablets, microphones, speakers, game consoles, gamepads, remote controls, remote controls, touchpads;

[0200] Monitors, displays, screens, touch-sensitive screens (sensor screens, "touchscreen devices"), projectors;

[0201] Readers for electronic books ("e-books");

[0202] Small televisions, pocket televisions, film players, video players, radios (including small and pocket radios), walkmen, discos, music players for example for CDs, DVDs, Blu-rays, cassettes, USB, MP3, headphones, cordless telephones, mobile phones, smartphones, walkie-talkies, hands-free devices, personal call devices (pagers, beepers);

[0203] Mobile defibrillators, blood glucose meters, blood pressure monitors, pedometers, heart rate monitors;

[0204] flashlights, laser pointers;

[0205] Mobile detectors, optical magnifiers, long-range vision devices, night vision devices, GPS devices, navigation devices, portable satellite communication interface devices;

[0206] Data storage devices (USB sticks, external hard drives, memory cards); and wristwatches, digital watches, pocket watches, chain watches, stopwatches.

[0207] Experimental part:

[0208] A. Raw materials used:

[0209] EEW: “epoxy equivalent weight” = epoxy equivalent weight

[0210] B. Production of poly(meth)acrylates:

[0211] Table 1 - Composition of poly(meth)acrylates and comparative polymers

[0212] The polymers P1 and P4 were prepared as follows.

[0213] A 4 L reactor conventional for radical polymerizations was charged with 320 g of the

[0214] The reactor was charged with a mixture of monomers specified in Table 1 and 273 g of ethyl acetate / isopropanol (96 / 04). After 45 minutes of nitrogen gas being passed through it with stirring, the reactor was heated to 58 °C and 0.2 g of 2,2'-azobis(2-methylbutyronitrile) was added. A further 480 g of the monomer mixture specified in Table 1 and 377 g of ethyl acetate were added continuously over a period of 2 hours. The external heating bath was then heated to 65 °C and the reaction was carried out at a constant external temperature. After 1 h and after 1.5 h of reaction time, 0.3 g and 0.3 g of 2,2'-azobis(2-methylbutyronitrile) were added, respectively. To reduce the residual monomers, 0.12 g of di(4-tert-5-butylcyclohexyl)peroxydicarbonate was added after 6 h and after 7.5 h. The mixture was diluted once with 160 g of ethyl acetate after 2 h and 4 h. The reaction was stopped after 24 h and cooled to room temperature.

[0215] C. Production of reactive adhesives:

[0216] The reactive adhesives were prepared in the laboratory according to the quantities listed in the tables below. The epoxy compounds were added to the polymer in solvent, followed by the photoinitiator, while stirring.

[0217] D. Production of reactive adhesive tapes as pressure-sensitive adhesive tapes:

[0218] To produce the reactive adhesive layers, i.e., the carrier-free pressure-sensitive adhesive tapes, the various reactive adhesives were applied from a solution to a conventional liner (siliconized polyester film) using a laboratory coating device and dried. The adhesive layer size was approximately 21 cm x 30 cm, and the adhesive layer thickness after drying was 100 ± 5 μm. Drying was carried out first at room temperature for 15 minutes and then for 15 minutes at 120 °C in a laboratory drying cabinet. Immediately after drying, the dried adhesive layers were laminated to a second liner (siliconized polyester film with lower release force) on the open side.

[0219] E. Test methods

[0220] Push-Out Room Temperature (RT) - initial:

[0221] The push-out test provides information about the bond strength of an adhesive product in the direction of the adhesive layer normal. A circular first substrate (1) with a diameter of 21 mm, a square second substrate (2) with a side length of 40 mm and a circular, centrally located opening (bore) of 9 mm in diameter, and the adhesive tape sample to be tested (here, the adhesive product) are provided, which was punched into a ring with an outer diameter of 18 mm and an inner diameter of 13 mm, resulting in a ring with a web width of 5 mm.

[0222] A test specimen is produced from the three components mentioned above by bonding the adhesive product with the free surface centered on the substrate (1). Then, the temporary protective film (siliconized PET liner) is removed and subjected to at least 4500 mJ / cm 2a 365 nm LIV-LED (Hönle AG). This bond is applied concentrically to the substrate (2) within 2 minutes with the now exposed side of the adhesive product, i.e., such that the circular recess of the substrate (2) is positioned exactly centrally above the circular first substrate 1 (the bonding area is thus 151 mm 2 ) and pressed with a pressure of at least 10 bar for at least 10 seconds, producing the test specimen.

[0223] After pressing, the test specimens are conditioned for 72 hours at 23 °C / 50 % relative humidity (RH). After storage, the adhesive bond is clamped in a specimen holder so that the bond is aligned horizontally. The test specimen is placed in the specimen holder with the substrate (1) facing down and the bond strength is measured in a Zwick [Z020]. For this purpose, a steel punch with a diameter of 7 mm is moved through the circular opening in substrate (2) and the force required to separate the circular substrate (1) from the square substrate (2) is determined. The determined force is divided by the bonded area and the force is given in MPa as the output value.

[0224] Three samples per product are tested and the mean value is given as an indicator for the bond strength.

[0225] Push-Out (Al-Al and SUS-SUS) - after 72h at 40°C in isopropanol / water:

[0226] To determine the chemical resistance of the bond, push-out test specimens constructed as described above were placed in a 40°C bath of isopropanol / water (70 / 30, i.e. 70% by volume to 30% by volume) for 72 hours. After removal, the test specimens were re-conditioned at 23°C and 50% RH for one hour. The bond strength was then measured as described under Push-Out - initial. To determine the bond strength on aluminum (Al-Al), a 1 mm thick circular aluminum disc (21 mm diameter) was chosen as substrate (1), and a 2 mm thick square aluminum substrate with 40 mm sides and a circular, centrally located opening (bore) with a diameter of 9 mm was chosen as substrate (2). The aluminum substrates are anodized E6 EV1 (alloy 5005A [AIMgl ]).

[0227] To determine the bond strength on steel (SUS-SUS), a 3 mm thick circular steel disc (21 mm diameter) was chosen as substrate (1), and a 2 mm thick square steel substrate with 40 mm sides and a circular, centrally located opening (bore) of 9 mm diameter was chosen as substrate (2). The steel substrates are made of VA-1.4301 steel (mirror polished on one side).

[0228] F. Results

[0229] Table 2 - Composition of the reactive comparative adhesive V1 and the reactive adhesives E1 to E4 according to the invention (all data in parts by weight) as well as bond strengths as an indicator of chemical resistance:

[0230] Table 3 - Composition of the reactive comparative adhesive V2 and the reactive adhesives E5 to E7 according to the invention (all data in parts by weight) as well as bond strengths as an indicator of chemical resistance: nb = not determinable. Table 4 - Composition of the reactive comparative adhesive V3 and the inventive reactive adhesives E8 to E16 (all data in parts by weight) and bond strengths as an indicator of chemical resistance:

[0231] In a further experiment, starting from Example E9, the amount of benzyl cinnamate was increased to more than 15%, namely to 17%.

[0232] Here, the initial bond strengths for Al-Al and SUS-SUS (Push Out RT -initial) were already so low that no further tests were carried out.

[0233] Table 5 - Composition of the reactive comparative adhesive V4 and the reactive adhesives E17 to E18 according to the invention (all data in parts by weight) and bond strengths as an indicator of chemical resistance: nb = not determinable.

[0234] All adhesives E1 to E18 according to the invention show sufficient to excellent initial bond strengths (Push-Out RT - initial), not listed in the tables.

[0235] In particular, however, as can be seen from Tables 2 to 5, the examples according to the invention show sufficient to excellent bond strengths even after immersion in a mixture of isopropanol and water for 72 hours.

[0236] The inventive adhesives E1 to E18 thus exhibit good to very good chemical resistance, which is overall improved compared to the comparative examples. Table 4 shows an improvement in bond strength on steel for all inventive examples, while on aluminum it is the same (E10, E13 to E15) or also improved. Examples E8, E9, E11, and E12 in Table 4 represent particularly advantageous examples.

[0237] Although the reference adhesives V2 and V4 demonstrated acceptable initial bond strengths in the push-out test, they did not demonstrate chemical resistance, as the bonds failed during the immersion time in the isopropanol-water mixture or, at the latest, during sample preparation for the push-out tests after removal from the mixture. Thus, the values ​​could not be determined (n.d.).

Claims

Patent claims 1 . Reactive curing adhesive containing (a) one or more (co-)polymers; and (b) at least one epoxy compound; and (c) at least one photoinitiator for initiating a cationic polymerization; and (d) at least one chemical compound comprising at least one phenyl group or a derivative of a phenyl group substituted on the benzene ring.

2. Reactively curable adhesive composition according to claim 1, characterized in that the combined mass fraction of the chemical compound (d) in the adhesive composition is at least 3%, preferably 3 to 15%, based on the mass of the reactively curable adhesive composition.

3. Reactively curable adhesive composition according to claim 1 or 2, characterized in that the at least one chemical compound (d) has a molecular mass (M) of less than 500 g / mol, in particular less than 300 g / mol, preferably less than 250 g / mol.

4. Reactively curable adhesive composition according to one of claims 1 to 3, characterized in that the at least one chemical compound (d) comprises the at least one phenyl group or the derivative of a phenyl group substituted on the benzene ring in a structural unit which is selected from Bz-O-, Ph-O- and derivatives of Bz-O- and Ph-O- substituted on the benzene ring, where Bz stands for benzyl and thus phenylmethylene, O stands for oxygen and Ph stands for phenyl.

5. Reactively curable adhesive composition according to one of claims 1 to 4, characterized in that the at least one chemical compound (d) is selected from the group consisting of benzyl alcohol, phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane, phenyloxirane, phenyl glycidyl ether, benzyl cinnamate, benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol, vanillin, 2-phenoxyethyl acrylate, benzyl acrylate, cardanol methacrylate, w-phenyl oligoethylene glycol acrylate, 2-benzyloxyethanol, 4-benzyloxyphenol and butoxynol-5-carboxylic acid and is preferably selected from the group consisting of benzyl alcohol, 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane, phenyloxirane, phenyl glycidyl ether, Benzyl cinnamate, benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol and vanillin, and is particularly preferably selected from the group consisting of benzyl cinnamate, vanillin, benzyl alcohol and cinnamyl alcohol.

6. Reactively curable adhesive according to one of claims 1 to 5, characterized in that it is a reactively curable pressure-sensitive adhesive.

7. Reactively curable adhesive composition according to one of claims 1 to 6, characterized in that the one or more (co)polymers (a) are selected from the group consisting of poly(meth)acrylates, (meth)acrylate block copolymers, polyurethanes, polyvinyl acetals, such as polyvinyl butyral, polysiloxanes, synthetic rubbers, polyesters, phenoxy polymers, polyvinyl alcohols, polyvinyl alcohol copolymers, and alkene-vinyl ester copolymers, preferably selected from the group consisting of poly(meth)acrylates, (meth)acrylate block copolymers, phenoxy polymers, polyvinyl alcohols, polyvinyl alcohol copolymers, polyvinyl acetals, such as polyvinyl butyral, and ethylene-vinyl acetate copolymers (EVA or EVAC, poly(ethylene-co-vinyl acetate)), in particular selected from the group consisting of poly(meth)acrylates, (Meth)acrylate block copolymers and ethylene-vinyl acetate copolymers.

8. Reactively curable adhesive according to one of claims 1 to 7, characterized in that the at least one epoxy compound (b) is selected from the group consisting of cycloaliphatic epoxy resins, such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bisphenol A diglycidyl ether (BADGE) resins, hydrogenated bisphenol A diglycidyl ether (BADGE) resins, epoxy-terminated nitrile rubbers (ETBN) and epoxy-terminated butadiene rubbers (EBN), particularly preferably from the group consisting of bisphenol A diglycidyl ethers and hydrogenated bisphenol A diglycidyl ethers.

9. Reactively curable adhesive composition according to one of claims 1 to 8, characterized in that the at least one photoinitiator for initiating a cationic polymerization (c) is selected from the group consisting of sulfonium salts and iodonium salts, wherein the cation of the photoinitiator is preferably selected from aceto- and methyl-substituted triarylsulfonium and diaryliodonium substituted on the phenyl groups.

10. Reactively curable adhesive tape comprising at least one layer of a reactively curable adhesive composition according to one of claims 1 to 9. 1 1. Reactively curable adhesive tape according to claim 10, characterized in that it additionally comprises a carrier layer and preferably a further reactively curable adhesive composition according to one of claims 1 to 9.

12. A method for bonding two substrates using a reactively curable adhesive composition according to one of claims 1 to 9 or a reactively curable adhesive tape according to claim 10 or 11, wherein the adhesive tape is a double-sided adhesive tape, comprising the steps A) Applying the reactively curable adhesive or the reactively curable adhesive tape to a first substrate B) Activation of the reactive curing adhesive or the reactive curing adhesive tape by irradiation with UV light, preferably from a LIV-LED lamp. C) Joining a second substrate to the activated reactive curable adhesive or the activated reactive curable adhesive tape.

13. Use of the reactively curable adhesive composition according to one of claims 1 to 9 or of the reactively curable adhesive tape according to claim 10 or 11 as an adhesive in the manufacture of electronic, optical or precision mechanical devices.

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