Chemical resistant, reworkable cured adhesives and tapes

Abstract

The present invention relates to a reactionally curable adhesive, to a reactionally curable adhesive tape comprising the reactionally curable adhesive, and to the use of the respective adhesive and adhesive tape for bonding two or more components. The reactionally curable adhesive comprises: (a) one or more (co)polymers; and (b) at least one epoxide compound; and (c) at least one photoinitiator for initiating cationic polymerization; and (d) at least one compound comprising at least one phenyl group or phenyl ring-substituted phenyl derivative.

Description

Technical Field

[0001] The present invention relates to reactive curable adhesive compositions, reactive curable tapes comprising reactive curable adhesive compositions, and the use of the corresponding adhesive compositions and tapes for bonding two or more components. Background Technology

[0002] The joining of individual components is one of the core processes in manufacturing. Among other methods such as welding and brazing, bonding, i.e., joining using adhesives, is of particular importance today. Here, the so-called tape is an alternative to using amorphous adhesives, such as those applied from a tube. Pressure-sensitive tape is particularly familiar in everyday life, where the adhesive effect is provided by a pressure-sensitive adhesive composition that is durable and bondable under typical environmental conditions. The corresponding pressure-sensitive tape can be applied to a substrate and remain adhered thereto, but can then be removed again with more or less no residue.

[0003] However, further types of tapes are also of great significance, especially for industrial manufacturing. Among these tapes, sometimes also called reactive (pressure-sensitive) tapes, are reactive curable adhesive compositions, sometimes referred to as reactive adhesive compositions. The corresponding curable / reactive adhesive composition has not yet reached its maximum crosslinking degree in the state intended for application and can be cured by external influences, by initiating polymerization in the reactive adhesive composition and thereby increasing the crosslinking degree. This process alters the mechanical properties of the now-cured adhesive composition, particularly increasing viscosity, surface hardness, and strength.

[0004] Reactive adhesive compositions are known in the art and can have very different compositions from a chemical point of view. What these reactive adhesive compositions have in common is that the crosslinking reaction can be triggered by external influencing factors, such as by supplying energy, especially by curing through temperature, plasma or radiation, and / or by contact with a polymerization-promoting substance, such as in the case of moisture-curing adhesive compositions.

[0005] Compositions containing cationic curable epoxy components are a type of reactive adhesive composition of particular industrial significance. These tapes are considered particularly advantageous for a wide range of industrial applications due to their handling and application properties, as well as the adhesive properties they can achieve. Pressure-sensitive tapes with reactive adhesive compositions containing cationic curable epoxy components are particularly advantageous because they can be applied more easily and with greater positional accuracy than liquid adhesives. Furthermore, these reactive adhesive compositions can be used as structural or semi-structural adhesives after curing. According to DIN EN 923: 2006-01, a structural adhesive is an adhesive that forms a bond that maintains a specified strength within a structure over a specified relatively long period of time (as defined by ASTM: "an adhesive used to transfer the required load between adherends exposed to the typical use environment of the structure in question"). Therefore, it is an adhesive that can withstand high chemical and physical stresses and contributes to enhanced adhesion of the tape in the cured state.

[0006] Reactive pressure-sensitive tapes are well known to those skilled in the art. For example, WO 2023 / 274875 A1 discloses a reactive tape comprising a film, a first external reactive adhesive composition, and a second external reactive adhesive composition, wherein at least one of the reactive adhesive compositions comprises a reactive component such as an epoxy resin, a photoinitiator, one or more foaming agents, and a polymer of greater than 60.0% by weight, and wherein the reactive adhesive composition has been foamed. In the case of these tapes, die-cutting capability is improved by using a film combined with the foamed adhesive composition.

[0007] US 10 676 655 B2 discloses a curable pressure-sensitive adhesive that provides a semi-structural or structural adhesive upon curing, exhibiting improved cold flow properties and excellent adhesion properties, and comprising (a) a tetrahydrofurfuryl (meth)acrylate copolymer, (b) an epoxy resin, (c) a polyether polyol, (d) a hydroxyl-functionalized film-forming polymer, and (e) a cationic photoinitiator.

[0008] WO 2017 / 174303 A1 describes pressure-sensitive adhesive tapes comprising a radiation-activated polymerizable composition, which in turn comprises: A. At least one film-forming agent component, in parts by weight of 5 to 60 parts; B. At least one epoxy component, in parts by weight, from 40 to 95 parts; C 0.1 to 10 parts by weight of at least one photoinitiator, and D. Optional 0.1 to 200 parts by weight of at least one additive, The radiation-activated polymerizable composition, in its respective case, is based on a radiation-activated polymerizable composition wherein the total weight parts of components A and B are 100, and is characterized in that film-forming component A comprises at least one polyurethane polymer. The radiation-activated polymerizable composition shall have a sufficient open time of at least one minute and, upon radiation activation, shall exhibit a satisfactory dark reaction and good final bond strength of at least 2 MPa on steel.

[0009] EP 3091059 A1 discloses a pressure-sensitive 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 comprises at least 104 parts of at least one reactive resin per 100 parts of the polymer and adhesive resin, and at least one initiator and / or curing agent and / or accelerator, wherein the tape, after curing, exhibits significantly higher shear strength than other tape / adhesive compositions of the prior art. Summary of the Invention

[0010] These reactive adhesive compositions and pressure-sensitive tapes containing reactive adhesive compositions are particularly suitable for miniaturized applications, such as those required in the electronics industry. Here, it is increasingly important to achieve connections between components in a highly precise and space-saving manner. Furthermore, due to the continued substantial global demand for communication and consumer electronics products and the ever-increasing demands for device efficiency, the tapes used are constantly facing new, or at least increasingly stringent, performance requirements. In particular, with the development of wearable electronic devices such as smartwatches (so-called wearable devices), the adhesives used are becoming increasingly important, in addition to having high adhesive strength (as desired for (semi-)structural adhesives), as well as high resistance to various chemicals (such as sweat, skin oils or sebum, sunscreen, or skincare products). This chemical resistance (chemical resistance) is simulated by cured pressure-sensitive tapes that retain acceptable adhesive strength even after long-term storage in various media, ideally with only minimal or no loss of adhesive strength. Other electronic devices such as smartphones, tablets, laptops, cameras, camcorders, keyboards, and touchpads are increasingly meeting similar requirements.

[0011] Although the adhesive compositions known from the above disclosure have sufficiently high adhesive strength in the cured state, their resistance to chemicals (chemical resistance) is only limited, resulting in a decrease in adhesive strength after the adhesive bond comes into contact with chemicals.

[0012] Therefore, the object of the present invention is to eliminate or at least reduce the disadvantages of the prior art described above.

[0013] A particular object of the present invention is to provide reactive curable adhesive compositions and reactive curable tapes that have improved chemical resistance, such as resistance to sweat, skin oils or sebum, sunscreens or cosmetic skin care products, and isopropyl alcohol / water mixtures. This improvement should be particularly reflected in the adhesive strength after contact with chemicals, especially the chemicals mentioned above.

[0014] At the same time, the (final) bond strength, die-cutting capability, and optionally, and preferably, the initial pressure-sensitive adhesive tack should remain at at least the same level before contact with chemicals.

[0015] In tape development, a 7:3 isopropanol / water mixture is typically chosen to optimize the adhesive composition's chemical resistance to polar solvents. Therefore, resistance to this mixture is a critical test that must be passed before testing with other chemicals across the full range. Thus, improved chemical resistance should be specifically addressed for the 7:3 isopropanol / water mixture.

[0016] A further object of the present invention is to provide reactive curable adhesive compositions and reactive curable tapes that, in addition to having sufficient or improved chemical resistance, also have high or improved adhesive strength, especially in the cured state.

[0017] These objectives are achieved by the reactive curable adhesive composition according to claim 1 and by the reactive curable tape of the present invention. The present invention also provides a process for bonding two substrates using the reactive curable adhesive composition of the present invention or the reactive curable tape of the present invention.

[0018] The present invention also provides the use of the reactive curable adhesive composition of the present invention or the reactive curable tape of the present invention as an adhesive in the production of electronic, optical or precision mechanical devices. Detailed Implementation

[0019] In the context of this invention, the term "reactive adhesive composition" or "adhesive composition" is used instead of "reactive curable adhesive composition." This usage is similarly applicable to reactive curable tapes.

[0020] All statements in this specification apply to the adhesive compositions, tapes, processes, and uses of the adhesive compositions or tapes of the present invention.

[0021] This invention also covers all features that are the subject matter of any dependent claim. Furthermore, this invention covers combinations of various features with each other, and in this case, also different levels of preference. Thus, this invention covers, for example, combinations of a first feature identified as "preferred" and a second feature identified as "more preferred." This scope also includes subject matter mentioned in the context of "implementations" that also have different levels of preference.

[0022] It has been surprisingly found that (d) at least one chemical compound comprising at least one phenyl or a phenyl derivative substituted on the benzene ring achieves improved chemical resistance in the adhesive compositions of the present invention, which manifests as relatively high adhesive strength after the adhesive bond comes into contact with suitable chemicals, particularly a 7:3 isopropanol / water mixture.

[0023] The reactive curable adhesive composition of the present invention comprises: (a) one or more (co)polymers; and (b) at least one epoxy compound; and (c) at least one photoinitiator for initiating cationic polymerization; and (d) at least one chemical compound comprising at least one phenyl group or a phenyl derivative substituted on a benzene ring.

[0024] Reactive curable

[0025] In the context of this invention, "reactive curable adhesive composition" should be understood to mean an adhesive composition that cures by a chemical reaction of at least one correspondingly reactive component and thereby produces an adhesive bond.

[0026] In the context of this invention, the chemical reaction specifically includes the cationic polymerization of an epoxy compound (b), which is triggered by at least one photoinitiator (c) upon irradiation with light.

[0027] As described in the introduction, those skilled in the art are familiar with general curable adhesive compositions and particular curable pressure-sensitive adhesive compositions from the prior art; the various components specified above are also known to those skilled in the art and are commercially available from different suppliers in various variations, and preferred and exemplary representatives of the various components are also disclosed below.

[0028] As understood by those skilled in the art, the components defined above are each used "one or more". According to industry practice, the term "one or more" refers to the chemical properties of the respective compound, not its molar quantity. For example, a curable pressure-sensitive adhesive composition may contain only 3',4'-epoxycyclohexanecarboxylic acid epoxycyclohexyl methyl ester as a polymerizable epoxy compound, meaning that the curable pressure-sensitive adhesive composition contains a large number of the corresponding molecules.

[0029] According to industry practice, mass fraction is specified as the total mass fraction of one or more components, thereby indicating that the combined mass fraction of the corresponding components conforms to the relevant standards; in the absence of other provisions, the mass of the curable pressure-sensitive adhesive composition is used as a reference system in its respective case.

[0030] The curable adhesive composition of the present invention is curable. By virtue of its ability to undergo curing, the curable adhesive composition can be used as a structural adhesive after curing.

[0031] The reactive curable adhesive compositions and tapes of the present invention are preferably used as structural adhesives or semi-structural adhesives after curing. According to DIN EN 923:2016-03, structural adhesives have proven suitable for producing load-bearing structures in which the adhesive bond can withstand a high percentage of stress relative to the maximum breaking force over a long period of time without failure (according to the ASTM definition: "adhesives for transferring the required load between adherends exposed to the typical service environment of the structure in question"). Therefore, they are adhesives that can withstand high chemical and physical stresses and contribute to enhanced adhesion of the tape in the cured state.

[0032] The term "(semi-)structural adhesive" encompasses both "semi-structural adhesive" and "structural adhesive". "Semi-structural adhesive" refers to a cured adhesive (on steel) having an lap shear strength of at least 1.0 MPa, more preferably at least about 1.5 MPa, in its respective case. "Structural adhesive" refers to a cured adhesive (on steel) having particularly high lap shear strength and having an lap shear strength of at least 5 MPa, more preferably at least 7 MPa, and particularly preferably at least 10 MPa, in its respective case.

[0033] Chemical compounds (d)

[0034] The adhesive composition of the present invention comprises (d) at least one chemical compound including at least one phenyl or a phenyl derivative substituted on a benzene ring.

[0035] "Phenyl derivatives substituted on the benzene ring" is understood to mean phenyl compounds with one or more additional substituents, in which the aromatic properties of the benzene ring are preserved.

[0036] Further substituents on the benzene ring are particularly and preferably selected from hydroxyl (OH-), cyano (CN-), preferably hydrocarbon groups having up to seventeen, more preferably up to five, and most preferably up to three carbon atoms, alkoxy groups having up to five, preferably up to three, more preferably methoxy groups, and aldehyde groups.

[0037] Therefore, in the case of derivatives, the chemical compound as a whole is a chemical compound having a benzene ring with at least two substituents.

[0038] According to a preferred embodiment of the invention, it is phenyl, i.e., a single linked benzene ring without any additional substituents.

[0039] Therefore, in these embodiments of the invention, the chemical compound (d) includes at least one phenyl group (Ph-) that is attached to a further atom but does not have additional substituents on the benzene ring.

[0040] Examples of these chemical compounds (d) are particularly and preferably benzyl alcohol, cinnamaldehyde, cinnamyl alcohol, benzyl acetate, benzyl cinnamate, 2-phenoxyethyl acrylate, benzyl acrylate, 2-benzyloxyethanol and 4-benzyloxyphenol.

[0041] Benzyl cinnamate has two phenyl groups.

[0042] In a further preferred embodiment of the invention, it is a phenyl derivative substituted on a benzene ring, i.e., a single-linked benzene ring having at least one further substituent.

[0043] Therefore, in these embodiments of the invention, the chemical compound (d) comprises at least one phenyl group (Ph-) attached to a further atom and having at least one further substituent on the benzene ring. The further substituent is preferably selected from the group described above.

[0044] Examples of these chemical compounds (d) are particularly and preferably 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, eugenol, vanillin, cashew methacrylate, and butoxynol-5 carboxylic acid.

[0045] Based on the mass of the reactive curable adhesive composition, the total mass fraction of chemical compound (d) in the adhesive composition is preferably at least 3%, more preferably 3% to 15%. This means that in the case of two or more chemical compounds (d) as defined more specifically, the total amount corresponds to the mass fraction.

[0046] In a particularly advantageous embodiment, at least one chemical compound (d) comprises at least one phenyl or a phenyl derivative 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, wherein Bz is benzyl and therefore phenylmethylene, O is oxygen and Ph is phenyl.

[0047] The structural units, specially selected from Bz-O- and Ph-O-, surprisingly achieve exceptionally high chemical resistance and high adhesive strength.

[0048] It has been found that when the chemical compound (d) has a molecular weight (M) of less than 500 g / mol, especially less than 300 g / mol, and preferably less than 250 g / mol, it is particularly advantageous. Phenyl-containing additives within this molecular weight range surprisingly achieve exceptionally high adhesive strength and exceptionally high chemical resistance.

[0049] In the context of this invention, polymers containing phenyl groups are not specifically chemical compounds (d), but belong to polymers (a).

[0050] Therefore, the adhesive compositions of the present invention particularly comprise (d) at least one chemical compound including at least one phenyl or a phenyl derivative substituted on a benzene ring, wherein these chemical compounds (d) are not polymers.

[0051] In a particularly advantageous embodiment of the invention, at least one chemical compound (d) is selected from benzyl alcohol (M = 108.14 g / mol), 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]oxetane (CAS 18933-99-8), phenyl ethylene oxide, 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, cashew methacrylate, ω-phenyl oligomeric polyethylene glycol acrylate, 2-benzyloxyethanol, 4-benzyloxyphenol, and butylphenol polyether-5 carboxylic acid.

[0052] Suitable ω-phenyl oligomeric polyethylene glycol acrylates, particularly and for example, phenol (EO)4 acrylates, are available from Miwon Specialty Chemical Ltd. under the trade name Miramer M144.

[0053] More preferably, at least one chemical compound (d) is selected from benzyl alcohol (M = 108.14 g / mol), 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]oxetane (CAS 18933-99-8), phenyl ethylene oxide, phenyl glycidyl ether, benzyl cinnamate (M = 238.28 g / mol), benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol and vanillin.

[0054] Very special preferred ingredients include benzyl cinnamate, vanillin, benzyl alcohol, and cinnamyl alcohol.

[0055] One or more (co)polymers (a)

[0056] The reactive curable adhesive composition of the present invention comprises one or more (co)polymers. Those skilled in the art will understand that, conventionally, the (co)polymer is given the function of a film-forming agent, and therefore it is of particular importance because, in the preferred embodiment, a pressure-sensitive adhesive composition is obtained.

[0057] The curable adhesive composition of the present invention is preferred herein, wherein one or more (co)polymers are selected from poly(meth)acrylate, (meth)acrylate block copolymers, polyurethane, polyvinyl acetal such as polyvinyl butyral, polysiloxane, synthetic rubber, polyester, phenoxy polymer, polyvinyl alcohol, polyvinyl alcohol copolymer and olefin-vinyl ester copolymer, preferably selected from poly(meth)acrylate, (meth)acrylate block copolymer, phenoxy polymer, polyvinyl alcohol, polyvinyl alcohol copolymer, polyvinyl acetal such as polyvinyl butyral, and ethylene-vinyl acetate copolymer (EVA or EVAC, poly(ethylene-copoly-vinyl acetate)), especially selected from poly(meth)acrylate, (meth)acrylate block copolymer and ethylene-vinyl acetate copolymer.

[0058] Alternatively, in addition to (meth)acrylate block copolymers, further block copolymers may be used as (co)polymers.

[0059] Examples of block copolymers, particularly (meth)acrylate block copolymers, are disclosed in US2011003947 A1, US 20080200589 A1, US 2007078236 A1, US 2007078236 A1, US2012196952 A1, US 2016032157 A1, US 2008146747 A1 and US 2016230054 A1.

[0060] In a particularly advantageous embodiment, at least one poly(meth)acrylate is present as a (co)polymer (a).

[0061] The poly(meth)acrylate may, in principle, be any poly(meth)acrylate known to those skilled in the art as suitable for adhesive compositions and tapes.

[0062] According to the present invention, the term "poly(meth)acrylate" covers polymers based on acrylates, polymers based on both acrylates and methacrylates, and polymers based on methacrylates. According to the present invention, the terms "(meth)acrylate ester" and "(meth)acrylate-" respectively cover both esters of acrylic acid and esters of methacrylate, or both acrylates and methacrylates.

[0063] The monomer composition to which the poly(meth)acrylate of the reactive adhesive composition is attributed typically consists of up to 15 different monomers. Preferably, the monomer composition consists of up to 5 different monomers, more preferably 4 different monomers, and even more preferably one to three different monomers.

[0064] In a particularly preferred embodiment, the monomer composition to which the poly(meth)acrylate of the reactive adhesive composition can be attributed consists of three different monomers.

[0065] In a further particularly preferred embodiment, the monomer composition to which the poly(meth)acrylate of the reactive adhesive composition is attributable consists of a single monomer.

[0066] In the above embodiments, especially those in which the monomer composition consists of one, two, or three monomers, it is preferred that the one or at least one monomer is selected from the group hereinafter referred to as Group 1, which consists of: benzyl acrylate, phenyl acrylate, 2-phenylethyl acrylate, 3-phenylpropyl acrylate, 4-phenylbutyl acrylate, 5-phenylpentyl acrylate, 6-phenylhexyl acrylate, benzyl methacrylate, phenyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 4-phenylbutyl methacrylate, 5-phenylethyl meth ... 2-Phenylhexyl methacrylate, 2-phenoxyethyl acrylate, 2-phenoxydiethylene glycol acrylate, 2-phenoxytriethylene glycol acrylate, 2-phenoxytetraethylene glycol acrylate, 2-phenoxypentaethylene glycol acrylate, 2-phenoxyhexaethylene glycol acrylate, 2-phenoxyheptaethylene glycol acrylate, 2-phenoxyoctaethylene glycol acrylate, 2-phenoxynonethylene glycol acrylate, 2-phenoxydeethylene glycol acrylate, 2-phenoxyethyl methacrylate, 2-phenoxydiethylene glycol methacrylate, 2-phenoxytriethylene glycol methacrylate Ester, 2-phenoxytetraethylene glycol methacrylate, 2-phenoxypentaethylene glycol methacrylate, 2-phenoxyhexaethylene glycol methacrylate, 2-phenoxyheptaethylene glycol methacrylate, 2-phenoxyoctaethylene glycol methacrylate, 2-phenoxynonethylene glycol methacrylate, 2-phenoxydecaethylene glycol methacrylate, 4-tert-butylphenyl acrylate, 4-tert-butylphenyl methacrylate, 2-(4-tert-butyl)phenoxyethyl acrylate, 2-(4-tert-butyl)phenoxydiethylene glycol acrylate, 2-(4-tert-butyl)phenoxytriethylene glycol Acrylates, 2-(4-tert-butyl)phenoxytetraethylene glycol acrylate, 2-(4-tert-butyl)phenoxypentaethylene glycol acrylate, 2-(4-tert-butyl)phenoxyhexaethylene glycol acrylate, 2-(4-tert-butyl)phenoxyheptaethylene glycol acrylate, 2-(4-tert-butyl)phenoxyoctaethylene glycol acrylate, 2-(4-tert-butyl)phenoxynonethylene glycol acrylate, 2-(4-tert-butyl)phenoxydecaethylene glycol acrylate, 2-(4-tert-butyl)phenoxyethyl methacrylate, 2-(4-tert-butyl)phenoxydiethylene glycol methacrylate, 2-(4-tert-butyl)phenoxytriethylene glycol methacrylate, 2-(4-tert-butyl)phenoxytetraethylene glycol methacrylate, 2-(4-tert-butyl)phenoxypentaethylene glycol methacrylate, 2-(4-tert-butyl)phenoxyhexaethylene glycol methacrylate, 2-(4-tert-butyl)phenoxyheptaethylene glycol methacrylate, 2-(4-tert-butyl)phenoxyoctaethylene glycol methacrylate, 2-(4-tert-butyl)phenoxynonethylene glycol methacrylate, 2-(4-tert-butyl)phenoxydecaethylene glycol methacrylate.

[0067] More preferably, the monomer or at least one monomer is selected from benzyl acrylate, phenyl acrylate, benzyl methacrylate, phenyl methacrylate, 2-phenoxyethyl acrylate, and 2-phenoxyethyl methacrylate.

[0068] In a preferred embodiment where the monomer composition is composed of monomers, the monomers are preferably selected from phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, and benzyl methacrylate. Benzyl acrylate is particularly preferred.

[0069] In a preferred embodiment where the monomer composition consists of three different monomers, a monomer selected from 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, and benzyl methacrylate is preferably present. 2-phenoxyethyl acrylate is particularly preferred.

[0070] In a preferred embodiment where the monomer composition consists of two or more different monomers, the first monomer is preferably selected from group 1 above, and the first monomer is more particularly preferably selected from 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate and benzyl methacrylate.

[0071] At least one further monomer, preferably a second and third monomer in the case of three different monomers, preferably selected from group hereinafter referred to as group 2, which consists of: acrylic acid, cyclohexane-1,4-diethanol monoacrylate, 2,3-dihydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, behenate, behenate methacrylate, cetyl acrylate, ethyl methacrylate, 2-ethyhexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl diethylene glycol acrylate, n-hexyl acrylate, isobutyl acrylate, isobutyl methacrylate, eicosyl acrylate, isononyl acrylate, tetradecyl acrylate, methyl acrylate, methyl methacrylate, stearate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, methacrylic acid Cyclohexyl acrylate, (5-ethyl-1,3-dioxane-5-yl)methyl acrylate, dihydrodicyclopentadienyl acrylate, isoborneol acrylate, isoborneol methacrylate, norborneol acrylate, 4-tert-butylcyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, tert-butylcyclohexyl methacrylate, potassium 3-sulfonate propyl acrylate, 2-(o-[1'-methylpropyleneamino]carboxyamino)ethyl methacrylate, 2-[(3,5-dimethylpyrazolyl)carboxyamino]ethyl methacrylate, ureomethacrylate, methacrylamide, 4-acryloylmorpholine, acrylonitrile, N,N-dimethylacrylamide, N-tert-butylacrylamide, N-hydroxymethylmethacrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, vinylmethyloxazolidinone, maleic anhydride, and vinyl acetate.

[0072] More preferably, the second and third monomers are selected from acrylic acid, stearate acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, dihydrodicyclopentadienyl acrylate, isobornyl acrylate, cyclohexane-1,4-diethanol monoacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, tert-butylcyclohexyl methacrylate, behenyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, ethyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, tert-butylcyclohexyl methacrylate, 3,4-epoxycyclohexyl methacrylate, and glycidyl methacrylate.

[0073] Preferred ingredients include n-butyl acrylate, 2-ethylhexyl acrylate, and methyl acrylate.

[0074] In the context of this invention, polymers containing phenyl groups, such as polymers of aromatic acrylate monomers listed herein, are included in (co)polymers (a) rather than chemical compounds (d).

[0075] Poly(meth)acrylate is produced in a manner known to those skilled in the art.

[0076] Poly(meth)acrylates can, in principle, be produced using any free radical or free radical-controlled polymerization, as well as combinations of different polymerization processes. These include, in addition to conventional free radical polymerization, processes such as ATRP, nitroxide radical / TEMPO controlled polymerization, or RAFT. Poly(meth)acrylates can be produced using conventional polymerization initiators and optional chain transfer agents via copolymerization of (co)monomers, with polymerization taking place at normal temperatures in the bulk material, in an emulsion such as in water or liquid hydrocarbons, or in solution. Polymerization can be carried out in polymerization reactors typically equipped with agitators, multiple feed vessels, reflux condensers, heating and cooling systems, and facilities for operation under N2 atmosphere and overpressure. Free radical polymerization is carried out in the presence of one or more organic solvents and / or in the presence of water or in the bulk material. The aim here is to keep the amount of solvent used as low as possible. Polymerization time is typically between 6 and 48 hours, depending on conversion and temperature.

[0077] For solution polymerization, the solvents used are preferably 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), boiling gasoline, or mixtures of these solvents. An acetone-isopropanol solvent mixture having an isopropanol content between 1 and 10% by weight is preferred. The polymerization initiators used are typically conventional free radical-forming compounds, such as peroxides and azo compounds. Initiator mixtures may also be used. Thiols may also be used as chain transfer agents for polymerization to reduce molecular weight and polydispersity. For example, alcohols and ethers can be used as further so-called polymerization chain transfer agents.

[0078] In one embodiment, poly(meth)acrylate is obtained via a so-called "syrup process." In this process, the monomer composition is prepolymerized into a syrup in an upstream step. This syrup is then used to formulate a reactive adhesive composition and, after a coating step, is reacted to completion, for example, using light of a wavelength that is not activated by a cationic initiator. The tape of the present invention can be obtained via this process.

[0079] In a particularly advantageous embodiment, at least one (meth)acrylate block copolymer is present as (co)polymer (a).

[0080] (Meth)acrylate block copolymers may, in principle, be any (meth)acrylate block copolymer known to those skilled in the art.

[0081] As understood by those skilled in the art, (meth)acrylate block copolymers consist of poly(meth)acrylate blocks, and therefore of structural units derived from (meth)acrylate monomers. As understood by those skilled in the art, the term "(meth)acrylate" encompasses both acrylates and methacrylates. In this respect, it is preferred that the (meth)acrylate block copolymers and the corresponding poly(meth)acrylate blocks are produced primarily or even substantially entirely from (meth)acrylate monomers, and therefore primarily or even substantially entirely from correspondingly derived monomer units.

[0082] In the context of this invention and in accordance with the understanding of those skilled in the art, the term "poly(meth)acrylate" for use with poly(meth)acrylate blocks encompasses polyacrylates and polymethacrylates, as well as copolymers of these polymers. Poly(meth)acrylates and corresponding poly(meth)acrylate blocks may, in principle, contain smaller amounts of monomer units not derived from (meth)acrylates, particularly employing (meth)acrylic acid as a further component; strictly speaking, it is not "(meth)acrylate" in the narrow sense. Therefore, in the context of this invention, "poly(meth)acrylate" is understood to mean a (co)polymer for which, based on the mass of the monomer base, the monomer base consists of monomers selected from acrylic acid, methacrylic acid, acrylates, and methacrylates at a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, and very particularly preferably substantially 100% by mass. The mass fraction of acrylates and / or methacrylates is preferably 50% or more, more preferably 70% or more, and most preferably 90% or more.

[0083] Preferably, 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 (meth)acrylate.

[0084] The hard block P(A) is preferably a (meth)acrylate polymer having a glass transition temperature of 30°C or higher, particularly preferably 60°C or higher, very particularly preferably 70°C or higher, or even more particularly preferably 90°C or higher.

[0085] The soft block P(B) is preferably a (meth)acrylate polymer having a glass transition temperature of less than 20°C, more preferably less than 0°C, and even more preferably less than -20°C (negative 20 degrees Celsius).

[0086] In the context of this invention, the glass transition temperature of the polymer blocks in a polymer or block copolymer is determined by differential scanning calorimetry (DSC) as described in DIN EN ISO 11357. For this purpose, approximately 5 mg of untreated polymer sample is weighed into an aluminum crucible (25 µL volume) and sealed with a perforated cap. Measurements are performed using a Netzsch DSC 204 F1 instrument. The measurement is performed under nitrogen to achieve inertization. The sample is first cooled to -150°C, then heated to +150°C at a heating rate of 10 K / min, and then cooled again to -150°C. A subsequent second heating curve is run again at 10 K / min, and the change in heat capacity is recorded. The glass transition is detected as a step in the thermogram. The determination of the glass transition temperature can be performed without problem by those skilled in the art using DSC measurement, and this determination is described in more detail, for example, in EP 2832811 A1.

[0087] The monomers of the hard block P(A) are preferably selected from methyl methacrylate, methyl acrylate, tert-butyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl acrylate, isobornyl methacrylate, dihydrodicyclopentadienyl acrylate, hydroxyethyl methacrylate, cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, glycidyl methacrylate, ethyl methacrylate, and benzyl methacrylate.

[0088] In a particularly advantageous embodiment, it includes at least one hard block of a homopolymer of methyl methacrylate (MMA).

[0089] The monomers of the soft block P(B) are preferably selected from n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, isooctyl acrylate, 2-phenoxyethyl acrylate, propylheptyl acrylate, ethyl acrylate, lauryl acrylate, lauryl methacrylate, hydroxyethyl acrylate, methoxyethyl acrylate, heptadecanyl methacrylate, heptadecanyl acrylate, ethylene glycol acrylate, and stearyl methacrylate.

[0090] In a particularly advantageous embodiment, it includes at least one soft block of a homopolymer of n-butyl acrylate (BA).

[0091] In a further advantageous embodiment, it comprises at least one soft block of a copolymer of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA).

[0092] In a particularly advantageous embodiment, the (meth)acrylate block copolymer is a triblock copolymer having a block sequence P(A)-P(B)-P(A), wherein P(A) and P(B) are hard and soft blocks as defined above.

[0093] The two A blocks of an ABA-type (meth)acrylate block copolymer are characterized by a common standard that allows them to be produced from the same A monomers, and preferably also by a standard related to the glass transition temperature. Those skilled in the art will understand that, due to their production method, as a result of the nature of the polymerization process used for production, especially when using two or more different A monomers, the A blocks are highly similar, but not necessarily identical. Similar to the A and B blocks, this also applies to the (meth)acrylate block copolymer itself, because block copolymers that differ from each other only to the extent of production-related variations in the A and B blocks are referred to by those skilled in the art of polymer materials as a common material, i.e., a (meth)acrylate block copolymer. Therefore, even if the A blocks differ in terms of glass transition temperature, the differences are only slight. Thus, the curable adhesive composition of the present invention is a composition in which the poly(meth)acrylate of the A blocks can be produced by polymerization of the same A monomers, preferably substantially identical. For example, in this respect, the curable pressure-sensitive adhesive composition of the present invention is additionally or alternatively a composition in which the two A blocks are poly(meth)acrylates having a glass transition temperature difference of less than 5°C, preferably less than 3°C, more preferably less than 1°C.

[0094] In the inventors' view, it is generally preferred that block A be implemented as polymethacrylate and block B as polyacrylate. Therefore, the curable adhesive composition of the present invention is preferred, wherein block A is a methacrylate polymer and block B is an acrylate polymer. Most preferably, it is a curable adhesive composition wherein block A is polymethyl methacrylate and block B is poly(n-butyl acrylate) or poly(2-ethylhexyl acrylate) or a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate.

[0095] Preferably, P(A) is a homopolymer of MMA and P(B) is a homopolymer of BA or a copolymer of BA and 2-EHA, and more preferably, the soft block is a homopolymer of BA.

[0096] Suitable (meth)acrylate block copolymers are available, for example, under the trade name Kurality™ LA 3320.

[0097] (Meth)acrylate block copolymers are produced in other ways known to those skilled in the art.

[0098] Preferably, regarding the mass fractions of blocks A and B, according to the inventors, selecting a not-too-low mass fraction of block A is particularly advantageous. Based on experiments conducted by the inventors, it appears that the presence of a sufficient proportion of hard blocks has a particularly positive effect on favorable adhesive strength at elevated temperatures, which is particularly surprising, as the use of PMMA alone did not produce any improvement in this regard. The inventors consider it preferable that the curable adhesive composition of the present invention contains a total mass fraction of block A of 15% or more, preferably 25% or more, more preferably 35% or more, and most preferably 45% or more, based on the mass of the (meth)acrylate block copolymer.

[0099] Regarding the length of the (meth)acrylate block copolymer, a curable adhesive composition is preferred, wherein the number-average molar mass M of the (meth)acrylate block copolymer is... n The concentration is in the range of 20,000 to 1,000,000 g / mol, preferably in the range of 30,000 to 500,000 g / mol, and more preferably in the range of 50,000 to 350,000 g / mol.

[0100] In a particularly advantageous embodiment, at least one olefin-vinyl ester copolymer is present as (co)polymer (a).

[0101] Olefin-vinyl ester copolymers with a relatively high vinyl ester content are particularly preferred because the corresponding olefin-vinyl ester copolymers have an advantageously low crystallinity, which has proven particularly advantageous in experiments conducted by the inventors. At least one olefin-vinyl ester copolymer is preferably an ethylene-vinyl ester copolymer with a vinyl ester content of 60% or more, particularly 70% or more, based on the mass of the copolymer.

[0102] The ethylene-vinyl acetate copolymer is preferably an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content of 60% or more, preferably 70% or more, based on the weight of the copolymer. Suitable ethylene-vinyl acetate copolymers are available from Arlanxeo under the trade name Levamelt® 700, having a vinyl acetate content of 70 percent by weight.

[0103] In a preferred embodiment, the number-average molar mass M of the (co)polymer, and more specifically all the listed poly(meth)acrylates, is... n The number-average molar mass M is within the range of 50,000 to 10,000,000 g / mol, more preferably within the range of 100,000 to 5,000,000 g / mol, and most preferably within the range of 150,000 to 2,000,000 g / mol. nThe values ​​were determined by gel permeation chromatography (GPC). 100 µl of filtered, clarified sample (sample concentration 4 g / L) was analyzed. The eluent used was tetrahydrofuran containing 0.1 vol% trifluoroacetic acid. Measurements were performed at 25°C. The pre-column used was a PSS-SDV type column, 5 µm, 10 3 Å, 8.0 mm 50 mm (The data here and below are in the following order: type, particle size, porosity, inner diameter) Length; 1 Å = 10 –10 Separation was performed using a combination of PSS-SDV type columns, 5 µm, 10 m. 3 Å, 10 5 Å and 10 6 Å, each 8.0 mm 300 mm column (column from Polymer Standards Service; measured using a Shodex RI71 differential refractometer). Flow rate: 1.0 ml / min. Calibration was performed using the commercially available ReadyCal Kit Poly(styrene) high from PSS Polymer Standards Service GmbH, Mainz, or Agilent. Data were universally converted to polymethyl methacrylate (PMMA) based on Mark-Houwink parameters K and alpha, so that data are reported in PMMA mass equivalents. Polyacrylate was calibrated against PMMA standards (PMMA calibration), and other types (resins, elastomers) were calibrated against PS standards (polystyrene calibration).

[0104] Alternatively or alternatively, it is preferred that the present (co)polymer has at least 100, preferably at least 500, more preferably at least 1000 repeating units, i.e., monomer units.

[0105] Regardless of the specific copolymer selected, the reactive curable adhesive composition of the present invention is preferred, wherein the total mass fraction of the copolymer in the curable adhesive composition is in the range of 20% to 55%, preferably in the range of 20% to 50%, particularly preferably in the range of 25% to 50%, very particularly preferably in the range of 25% to 50%, and most preferably in the range of 35% to 50%, based on the mass of the curable adhesive composition.

[0106] At least one epoxy compound (b)

[0107] The curable adhesive composition of the present invention comprises not only a (co)polymer but also at least one epoxy compound. The epoxy compounds collectively form components of a curable adhesive composition commonly referred to by those skilled in the art as reactive resins. Therefore, at least one epoxy compound (d) is more specifically a polymerizable epoxy compound. As understood by those skilled in the art, the term "polymerizable" refers to the ability of these compounds to undergo polymerization reactions, if necessary, after appropriate activation. In the case of polymerizable epoxy compounds, polymerizability is made possible, for example, through epoxy groups.

[0108] During the curing reaction of reactive adhesive compositions, the conversion of epoxy compounds is achieved, in particular, via cationic polymerization of epoxy groups. Epoxy compounds can be used to produce adhesives with exceptionally high shear strength. Furthermore, the crosslinking reaction is easily initiated and controlled. Reactive adhesive compositions produced using epoxy compounds exhibit sufficient storage stability in the uncured state.

[0109] As understood by those skilled in the art, an epoxy compound is a compound having at least one ethylene oxide group.

[0110] Epoxy compounds can be aromatic or aliphatic, especially alicyclic. They can encompass both monomeric and oligomeric or polymeric epoxides. Epoxy compounds typically have an average of at least two epoxy groups per molecule, preferably more than two. 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.

[0111] Oligomeric or polymeric epoxy compounds typically comprise linear polymers with terminal epoxy groups (e.g., diglycidyl ethers of polyoxyalkylene glycols), polymers with structural ethylene oxide units (e.g., polybutadiene polyepoxides), and polymers with epoxy side groups (e.g., glycidyl methacrylate polymers or copolymers). The reaction of epoxy resins with CTBN yields so-called epoxy-terminated nitrile butadiene rubber (ETBN). These ETBNs are commercially available from Huntsman International, for example, under the name Hypro ETBN, such as Hypro 1300X40 ETBN, Hypro 1300X63 ETBN, and Hypro 1300X68 ETBN.

[0112] The at least one epoxy compound present in the photocurable adhesive composition of the present invention, or the molecular weight of the epoxy compound, can vary from 58 to about 100,000 g / mol, and molecular weight is an important control variable for adjusting dynamic viscosity. Examples of epoxy compounds include cyclohexane esters of epoxy, such as 4-epoxycyclohexanecarboxylic acid methyl ester, 3,4-epoxy-2-methylcyclohexanecarboxylic acid methyl ester, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid ester. Further examples of epoxy compounds are disclosed, for example, in US 3,117,099 A. Further suitable epoxy compounds particularly useful in the application of the present invention include, for example, glycidyl ether monomers disclosed in US 3,018,262 A. Examples include glycidyl ethers of polyphenols (e.g., diglycidyl ethers of 2,2-bis(2,3-epoxypropoxyphenol)propane) obtained by reacting polyphenols with excess chlorohydrins such as epichlorohydrin. 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 their hydrogenated variants. These reaction products are commercially available in various molecular weights and states (e.g., so-called type I to type I0 BADGE resins). Typical examples of liquid bisphenol A diglycidyl ethers include Epitoke 828, DER331, and Epon 828, and an example of liquid hydrogenated bisphenol A diglycidyl ether is Eponex 1510. Typical solid BADGE resins are Araldite GT6071, GT7072, Epon 1001, and DER 662. Further reaction products of phenols with epichlorohydrin are phenol and cresol phenolic resins, such as the Epiclon series or the Araldite EPN and ECN series (e.g., ECN1273). Further suitable epoxy compounds are epoxy resins obtained from renewable raw materials, such as those obtained from oils, such as epoxidized linseed oil or epoxidized soybean oil, or those obtained from cashew nut shells, such as epoxidized cashew phenol, or epoxy resins containing glycerol, such as bisphenol A reacted with epichlorohydrin obtained from glycerol.

[0113] The preferred reactive curable adhesive composition of the present invention comprises one or more polymerizable epoxy compounds selected from polymerizable epoxy compounds having a weight-average molar mass Mw in the range of 300 to 2000 g / mol, preferably in the range of 300 to 1500 g / mol, more preferably in the range of 350 to 1300 g / mol, wherein Mw is measured by GPC.

[0114] Alternatively or alternatively, it is also particularly preferred that the reactive curable adhesive composition comprises one or more polymerizable epoxy compounds selected from those having a weight-average molar mass Mw of 2000 g / mol or less, Mw being measured by GPC.

[0115] Polymerizable epoxy compounds can be, for example, aromatic or aliphatic, especially alicyclic.

[0116] Preferably, at least one epoxy compound (b) is selected from alicyclic epoxy resins such as 3',4'-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl ester, bisphenol A diglycidyl ether (BADGE) resin, hydrogenated bisphenol A diglycidyl ether (BADGE) resin, epoxy-terminated nitrile rubber (ETBN), and epoxy-terminated butadiene rubber (EBN), more preferably selected from bisphenol A diglycidyl ether and hydrogenated bisphenol A diglycidyl ether.

[0117] Further preferred are the reactive pressure-sensitive tapes of the present invention, wherein the reactive adhesive composition comprises two or more epoxy compounds, particularly epoxy resins, wherein at least one of the epoxy compounds is a solid, particularly a solid having a softening temperature of at least 45°C, or a highly viscous substance, preferably having a dynamic viscosity of 50 Pas or higher at 25°C, more preferably 100 Pas or higher, and especially preferably 150 Pas or higher (measured according to DIN 53019-1 2008; 25°C, shear rate 1 s⁻¹).

[0118] Particularly preferred are the reactive curable adhesive compositions of the present invention, which comprise two or more epoxy compounds, especially epoxy resins, wherein at least one epoxy compound (b1) is a liquid with a dynamic viscosity of 40 Pas or less, preferably 20 Pas or less, at 25°C, and at least one epoxy compound (b2) is a solid or a high-viscosity substance with a dynamic viscosity of 50 Pas or more at 25°C. The reactive adhesive compositions comprising liquid and solid or high-viscosity epoxy compounds exhibit a particularly good balance of adhesive properties in the uncured state.

[0119] In a preferred embodiment, the total weight ratio of the liquid epoxy compound (b1) with a dynamic viscosity of 40 Pas or less at 25°C to the total weight of the solid epoxy compound (b2) (a solid having a softening temperature of at least 45°C or a highly viscous substance having a dynamic viscosity of 50 Pas or higher at 25°C) in the reactive adhesive composition is 1:2 to 5:1, and more preferably 1.5:1 to 3:1.

[0120] Surprisingly, it has been found that reactive pressure-sensitive adhesives containing 3',4'-epoxycyclohexanecarboxylic acid methyl ester, which is very commonly used in UV-cured epoxy adhesives, exhibit relatively low chemical resistance in most cases. For this reason, the reactive adhesive composition of the reactive pressure-sensitive tape of the present invention preferably contains bisphenol A diglycidyl ether or hydrogenated bisphenol A diglycidyl ether or a mixture thereof as a liquid epoxy compound.

[0121] In a preferred embodiment, the total weight ratio of the liquid epoxy compound (b1) having a dynamic viscosity of 40 Pas or less at 25°C to the total weight of the solid epoxy compound (b2) (a solid having a softening temperature of at least 45°C or a highly viscous substance having a dynamic viscosity of 50 Pas or higher at 25°C) in the reactive adhesive composition is 1:2 to 5:1, and more preferably 1.5:1 to 3:1, wherein the liquid epoxy compound (b1) comprises at least one or more liquid hydrogenated bisphenol A diglycidyl ethers.

[0122] Regardless of the specific polymerizable epoxy compound selected, the curable adhesive composition of the present invention is preferred, wherein the total mass fraction of the epoxy compound, more specifically the polymerizable epoxy compound, in the curable adhesive composition is in the range of 30% to 60%, preferably in the range of 30% to 55%, more preferably in the range of 35% to 55%, and most preferably in the range of 35% to 50%, based on the mass of the curable adhesive composition.

[0123] At least one photoinitiator (c) for initiating cationic polymerization

[0124] When at least one epoxy compound is used in the reactive adhesive composition contemplated in this context, polymerization occurs, in particular, via cationic polymerization. Therefore, the reactive adhesive composition includes an initiator for cationic polymerization. Since the polymerization is to be activated by radiation, a photo-activated initiator is accordingly referred to as a photoinitiator.

[0125] Photoinitiators are understood to be compounds that can initiate chemical reactions under the influence of high-energy radiation. UV initiators are preferred. UV initiators are generally known to those skilled in the art.

[0126] Systems based on sulfonium, iodonium, and metallocene are particularly useful as initiators for these cationic radiation-based, i.e., typically UV-induced, curing of epoxy compounds.

[0127] For examples of sulfonium-based cations, see the disclosure in US 6,908,722 B1.

[0128] Examples of anions used as counterions to the aforementioned cations include tetrafluoroborate, tetraphenylborate, hexafluorophosphate, perchlorate, tetrachloroferrate, hexafluoroarsenate, hexafluoroantimonate, pentafluorohydroxyantimonate, hexachloroantimonate, tetra(pentafluorophenylborate), tetra(pentafluoromethylphenyl)borate, bis(trifluoromethanesulfonyl)amino anion, and tri(trifluoromethanesulfonyl)methyl anion. Furthermore, chloride, bromide, and iodide ions can also be conceived as anions, particularly for iodonium-based initiators, but initiators substantially free of chloride and bromine are preferred. An effective example of these systems is, for instance, 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.

[0129] Specific examples of sulfonium salts that may be used are, in particular, triarylsulfonium salts, which may be substituted with an acetyl or methyl group, such as those optionally substituted accordingly: triarylsulfonium hexafluorophosphate, triarylsulfonium tetrapentafluorophenylboronic acid, triphenylsulfonium hexafluoroarsenate, triphenylsulfonium hexafluoroboronic acid, triphenylsulfonium tetrafluoroboronic acid, triphenylsulfonium tetra(pentafluorobenzyl)boronic acid, methyl diphenylsulfonium tetrafluoroboronic acid, methyl diphenylsulfonium tetra(pentafluorobenzyl)boronic acid, dimethyl phenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonyate, diphenylnaphthylsulfonium hexafluoroarsenic acid, trimethylmethylsulfonium hexafluorophosphate, anisyl diphenylsulfonium hexafluoroantimonyate, 4-butoxyphenyl diphenylsulfonium tetrafluoroboronic acid, 4-chlorophenyl diphenylsulfonium hexafluoroantimonyate, tri(4-phenoxyphenyl)sulfonium hexafluorophosphate, and triphenylarsenic acid. Di(4-ethoxyphenyl)methylsulfonium, 4-acetylphenyl diphenylsulfonium tetrafluoroborate, 4-acetylphenyl diphenylsulfonium tetra(pentafluorobenzyl)borate, tris(4-thiomethoxyphenyl)sulfonium hexafluorophosphate, di(methoxysulfonylphenyl)methylsulfonium hexafluoroantimonate, di(methoxynaphthyl)methylsulfonium tetrafluoroborate, di(methoxynaphthyl)methylsulfonium tetra(pentafluorobenzyl)borate, di(methoxycarbonylphenyl)methylsulfonium hexafluorophosphate, (4-octyloxyphenyl)diphenylsulfonium tetra(3,5-bis(trifluoromethylphenyl)borate), tris[4-(4-acetylphenyl)thiophenyl]sulfonium tetra(pentafluorophenyl)borate, tris(dodecylphenyl)sulfonium tetra(3,5-bis(trifluoromethylphenyl)borate), 4-acetaminophenyl diphenylsulfonium tetrafluoroborate Tetra(pentafluorobenzyl)boronic acid 4-acetamidophenyl diphenylsulfonium, hexafluorophosphate dimethylnaphthylsulfonium, tetrafluoroboronic acid trifluoromethyl diphenylsulfonium, tetra(pentafluorobenzyl)boronic acid trifluoromethyl diphenylsulfonium, hexafluorophosphate phenylmethyl benzylsulfonium, hexafluorophosphate 5-methylthiaanthraquinone, hexafluorophosphate 10-phenyl-9,9-dimethylthiaanthraquinone, tetrafluoroboronic acid 10-phenyl-9-oxothiaanthraquinone, tetra(pentafluorobenzyl)boronic acid 10-phenyl-9-oxothiaanthraquinone, tetra(pentafluorobenzyl)boronic acid 5-methyl-10-oxothiaanthraquinone, tetra(pentafluorobenzyl)boronic acid 5-methyl-10,10-dioxothiaanthraquinone and hexafluorophosphate 5-methyl-10,10-dioxothiaanthraquinone.

[0130] Specific examples of iodonium salts that can be used include diphenyliodonium tetrafluoroborate, di(4-methylphenyl)iodonium tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate, di(4-chlorophenyl)iodonium hexafluorophosphate, dinaphthyliodonium tetrafluoroborate, di(4-trifluoromethyl-phenyl)iodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, di(4-methylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, di(4-phenoxyphenyl)iodonium tetrafluoroborate, and phenyl-2-thienyliodonium hexafluorophosphate. 3,5-Dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimony, 2,2'-diphenyliodonium tetrafluoroborate, di(2,4-dichlorophenyl)iodonium hexafluorophosphate, di(4-bromophenyl)iodonium hexafluorophosphate, di(4-methoxyphenyl)iodonium hexafluorophosphate, di(3-carboxyphenyl)iodonium hexafluorophosphate, di(3-methoxycarbonylphenyl)iodonium hexafluorophosphate, di(3-methoxysulfonylphenyl)iodonium hexafluorophosphate, di(4-acetaminophenyl)iodonium hexafluorophosphate Iodonium, di(2-benzothiophene)iodonium hexafluorophosphate, trifluoromethanesulfonylmethyl anion diaryliodonium, such as diphenyliodonium hexafluoroantimonate, diaryliodonium tetra(pentafluorophenyl)borate, such as diphenyliodonium tetra(pentafluorophenyl)borate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium hexafluoroantimonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluoromethanesulfonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium hexafluorophosphate ... trifluoromethanesulfonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluorophosphate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluoromethanesulfonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluorophosphate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluoromethanesulfonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium trifluoromethanesulfonate, [4-[(2-hydroxy-n-tetradecyl)oxy]phenyl]-phenyliodonium [4-[(2-hydroxy-tetradecyl)oxy]phenyl]-phenyliodonium, bis(4-tert-butylphenyl)iodonium hexafluoroantimonate, bis(4-tert-butylphenyl)iodonium hexafluorophosphate, bis(4-tert-butylphenyl)iodonium trifluorosulfonic acid, bis(4-tert-butylphenyl)iodonium tetrafluoroborate, bis(4-tert-butylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium trifluoromethanesulfonate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium trifluoromethanesulfonate, diphenyliodonium hydrogen sulfate, 4,4'-dichlorodiphenyliodonium hydrogen sulfate, 4,4'-dibromodiphenyliodonium hydrogen sulfate, 3,3'-dinitrodiphenyliodonium hydrogen sulfate, 4,4'-dimethyldiphenyliodonium hydrogen sulfate, 4,4'-dimethyldiphenyliodonium hydrogen sulfate, 4, 4'-bissuccinimide diphenyliodonium, 3-nitrodiphenyliodonium hydrogen sulfate, 4,4'-dimethoxydiphenyliodonium hydrogen sulfate, bis(dodecylphenyl)iodonium tetra(pentafluorophenyl)boronic acid, (4-octyloxyphenyl)-phenyliodonium tetra(3,5-bistrifluoromethylphenyl)boronic acid, and (tolylcumyl)iodonium tetra(pentafluorophenyl)boronic acid and ferrocene salts (see, for example, EP0 542 716 B1), such as η5-(2,4-cyclopentadien-1-yl)-[(1,2,3,4,5,6,9)-(1-methylethyl)-phenyl]iron.

[0131] These cationic photoinitiators are typically used alone or in combination of two or more photoinitiators. When using photoinitiators in existing curable adhesive compositions, combination with so-called sensitizers is also very helpful, particularly for tuning the activation wavelength of the photoinitiation system to a selected emission spectrum, as disclosed, for example, in AW Green's 2010 textbook, *Industrial Photoinitiators: A Technical Guide*.

[0132] Some cationic photoinitiators, such as those commercially available under the trade name Deuteron UV 1242, react only in a relatively short wavelength range of 220 to 250 nm. Here, activation cannot be achieved using typical UV-LEDs, which would be strongly preferred from an application technology perspective, or at least cannot be effectively achieved, because the emission maximum of typical UV-LEDs is at a wavelength of approximately 365 nm. Nevertheless, to enable activation of these cationic photoinitiators with typical UV LEDs, the concept of "radical accelerator cationic curing" as described in the literature is used. For this purpose, a radical initiator, such as those commercially available under the trade names Omnirad BDK or Irgacure 651, is added as a sensitizer, which decomposes upon excitation at a higher wavelength, such as the typical 365 nm wavelength of a UV LED. The radicals or other active species formed in this manner activate the cationic initiator, which ultimately initiates the curing of the epoxide. Typically, in these cases where a sensitizer is used, the mass fraction of the cationic photoinitiator in the curable adhesive composition is no more than 4% but at least 0.1%, and preferably in the range of 0.5% to 2%. The mass fraction of the sensitizer is usually no more than 3%, and preferably in the range of 0.5% to 2%.

[0133] In the context of this invention, cationic photoinitiators are preferably selected from the group described above, and particularly from sulfonium salts and iodonium salts.

[0134] In a particularly preferred embodiment, the total mass fraction of cationic photoinitiator in the curable adhesive composition is preferably 0.5% to 7%, particularly preferably 0.5% to 4%, very particularly preferably 0.5% to 3%, and even more preferably 0.5% to 2%, based on the mass of the curable adhesive composition.

[0135] In a particularly advantageous embodiment, the photoinitiator cation is selected from triarylsulfonium substituted with acetyl or methyl groups and commercially available, for example, under the names Omnicat 270 (IGM resins), QL 211, QL212 (Quang Li Chem.) and Irgacure 290 (BASF), or diaryliodonium substituted with a phenyl group, commercially available, for example, under the names Omnicat 250 (IGM resins), Speedcure 939, Speedcure 938, Speedcure 937 (Arkema), Deuteron 1240 and Deuteron 1242 (Deuteron).

[0136] In a particularly advantageous embodiment, at least one sulfonium salt is used as a cationic photoinitiator, such as, and especially, acetyl-substituted triarylsulfonium hexafluorophosphate (CAS: 953084-13-4) or acetyl-substituted triarylsulfonium tetrapentafluorophenylboronic acid or tri(4-(4-acetylphenyl)thiophenyl)tetra(pentafluorophenyl)boronic acid.

[0137] In a preferred embodiment, the reactive curable adhesive composition of the present invention comprises: 30% to 55% of at least one (co)polymer (a); 5% to 30%, especially 10% to 20%, of at least one liquid epoxy compound (b1); 5% to 30%, especially 10% to 20%, of at least one solid epoxy compound (b2); 0.5% to 7% of at least one photoinitiator (c) for initiating cationic polymerization; 3% to 15% of at least one chemical compound comprising at least one phenyl group or a phenyl derivative substituted on the benzene ring (d).

[0138] In a preferred embodiment of the invention, the polymer of the reactive curable adhesive composition is substantially inert relative to at least one epoxy compound and correspondingly relative to at least one reactive resin, relative to an initiator, relative to a phenyl compound, and relative to other optionally present substances.

[0139] In this context, "inert" means that, prior to photocuring, the polymerizable compound, the initiator, and other present substances do not substantially react with the polymer under appropriately selected conditions, particularly at room temperature (23°C). In particular, such reactions should not occur during the production, processing (e.g., coating), and curing of the adhesive film.

[0140] These inert polymers serve to form a film-forming matrix, which is an inert scaffold for the reactive resin, allowing the resin to be incorporated into the membrane or sheet rather than in a liquid form. This incorporation ensures easier handling. The polymer on which the film-forming matrix is ​​based is capable of forming a self-supporting membrane through sufficient interactions between macromolecules, for example—not intended to unnecessarily limit the scope of the invention—by forming a network based on physical and / or chemical crosslinking.

[0141] Further additives

[0142] The reactive curable adhesive composition of the present invention may optionally contain further additives and / or auxiliaries known in the prior art. If present, the proportion of the further additives and / or auxiliaries is preferably in the range of 0.1% to 50%, more preferably 0.2% to 40%, especially 0.2% to 20%, to 15%, even more preferably to 10%, and most preferably to 5% by mass based on the curable adhesive composition.

[0143] Examples of further additives and / or auxiliaries include reactive monomers, fillers, dyes, nucleating agents, further photoinitiators, rheology modifiers (e.g., fumed silica), foaming agents, adhesive-enhancing additives (adhesives, especially silanes and adhesive resins), compounding agents, plasticizers and / or aging, light and UV stabilizers, for example in the form of primary and secondary antioxidants.

[0144] In particular, and in a preferred embodiment, the proportion of filler such as glass beads or SiLibeads® 5211 is up to 50%, and more particularly up to 40%.

[0145] Particularly preferred additives are silane tackifiers or open-time additives. Silane tackifiers include, for example, 3-trimethoxysilylpropyl methacrylate (CAS No.: 2530-85-0), which can be traded under the name Dynasylan. ®MEMO is obtained from 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.

[0146] As open-time additives, the reactive curable adhesive compositions of the present invention preferably contain at least one substance selected from polyethylene glycol (PEG), polypropylene glycol (PPG), tertiary amines, and crown ethers (e.g., 18-crown-6); particularly at least one substance selected from PEG having a weight-average molecular weight of 400 to 10,000 g / mol, for example, up to 5,000 g / mol, very particularly preferably up to 1,000 g / mol, as determined above, and especially PEG 600. These substances have the effect that, after the curing initiation of the reactive adhesive composition, there is still a so-called open time during which curing has not yet begun or at least not significantly begun, and thus this means that these substances can be called "open-time additives". As shown, the open-time additives listed herein enable, particularly for UV-curable reactive adhesive compositions, an open time of at least one minute, typically 1 to 5 minutes, to be achieved after 24 hours of dark reaction at 25°C. For the purposes of this invention, the reaction is referred to as "completed" when the adhesive strength of the reactive pressure-sensitive tape is at least 2 MPa after 24 hours.

[0147] The reactive curable adhesive composition of the present invention may, in principle, contain one or more open time additives. If present, the aforementioned open time additives are preferably present in the adhesive composition at a total mass fraction of 0.1% to 10%, more preferably 0.2% to 5%, and particularly 0.3% to 4%.

[0148] Pressure-sensitive adhesive

[0149] To ensure the best possible processability for the end user, the reactive adhesive compositions of the present invention have pressure-sensitive adhesive properties or inherent pressure-sensitive adhesiveness.

[0150] Therefore, the reactive curable adhesive composition of the present invention is preferably a pressure-sensitive adhesive composition. Therefore, the reactive curable tape of the present invention is preferably a reactive curable pressure-sensitive tape.

[0151] Pressure-sensitive adhesive properties allow reactive pressure-sensitive tapes to be reliably and firmly applied to the substrate before curing.

[0152] As understood by those skilled in the art, a pressure-sensitive adhesive composition is an adhesive composition possessing pressure-sensitive adhesive properties, i.e., the ability to maintain a durable bond with the substrate even under relatively weak contact pressure. Corresponding pressure-sensitive tapes typically detach from the substrate substantially without residue after use and generally remain self-adhesive even at room temperature, implying a certain viscosity and tackiness that allows them to wet the substrate surface even under slight contact pressure. The pressure-sensitive adhesiveness of pressure-sensitive tapes derives from the use of a pressure-sensitive adhesive composition as the adhesive composition. Without wishing to be bound by this theory, it is generally assumed that the pressure-sensitive adhesive composition can be considered a highly viscous liquid with an elastic component and correspondingly possessing the characteristic viscoelastic properties that result in the aforementioned durable self-adhesion and pressure-sensitive adhesiveness. This assumption is that in the corresponding pressure-sensitive adhesive composition, mechanical deformation leads to both a viscous flow process and the accumulation of elastic restoring forces. The viscous flow component is used to achieve adhesion, while the elastic restoring force component is particularly necessary for achieving cohesion. The relationship between rheological properties and pressure-sensitive adhesive properties is known in the prior art and is described, for example, in "Satas, Technical Handbook of Pressure-Sensitive Adhesives", 3rd Edition, (1999), pp. 153-203.

[0153] The storage modulus (G') and loss modulus (G''), which can be determined by dynamic mechanical analysis (DMA), provide a more precise description and quantification of the degree of elastic and viscous components and the ratios between them. G' is a measure of the elastic component of a substance, and G'' is a measure of the viscous component. Both variables depend on the deformation frequency and temperature.

[0154] These variables can be measured using a rheometer. For example, the material under test is exposed to sinusoidal oscillating shear stress in a plate-plate assembly. In the case of a shear stress-controlled device, what is measured is the deformation as a function of time and the time delay of this deformation relative to the introduction of the shear stress. This time delay is called the phase angle δ. The storage modulus G' is defined as follows: G' = (τ / γ) cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between the shear stress vector and the deformation vector). The loss modulus G'' is defined as: G'' = (τ / γ) sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress vector and deformation vector).

[0155] In the context of this invention, when at a temperature of 23°C, at 10 0 Up to 10 1 Within the rad / sec deformation frequency range, both G' and G'' are at least partially within 10 3 Up to 107 When the Pa range is within a certain range, the adhesive composition is preferably understood to have pressure-sensitive adhesive properties and is therefore a pressure-sensitive adhesive composition. "Partially" means that at least a portion of the G' curve lies within the range of exactly 10... 0 Up to exactly 10 1 The distorted frequency range (x-axis) in rad / sec and from exactly 10 3 Up to exactly 10 7 The range of G' values ​​(vertical axis) of Pa is within the window that it spans, and at least a portion of the G'' curve also lies within the corresponding window.

[0156] For simplicity, the inventors define, for the purposes of this invention, a reactive pressure-sensitive adhesive tape as an adhesive tape having an adhesive strength of at least 1 N / cm in its uncured state and being removed with virtually no residue (i.e., adhesive failure in the test). Here, the adhesive strength was determined on steel at 23°C and 50% relative humidity, at a peel rate of 300 mm / min and a peel angle of 180°, according to ISO 29862:2007 (Method 3). The reinforcing film used was an etched PET film with a thickness of 36 µm, such as that available from Coveme (Italy). Adhesion of a 2 cm wide measuring strip was achieved using a 4 kg roller applicator at 23°C. The tape was peeled off immediately after application. The measured values ​​(in N / cm) are the average of three separate measurements. Cohesive failure in this test indicates an adhesive or tape that is adhesive at room temperature but whose cohesiveness is insufficient for residue-free removal. For the purposes of this invention, these adhesives or tapes are not pressure-sensitive adhesives.

[0157] Reactive curable tape

[0158] The reactive curable tape of the present invention comprises at least one layer of the reactive curable adhesive composition of the present invention.

[0159] In a preferred embodiment, the reactive curable tape of the present invention consists of layers of the reactive curable adhesive composition of the present invention and does not have a carrier layer. Therefore, in this embodiment, the tape is a carrier-free reactive transfer tape.

[0160] In a further preferred embodiment, the reactive tape is characterized in that, in addition to the adhesive layer, it also comprises a carrier layer. This includes both single-sided and double-sided tapes, which comprise at least one outer layer composed of the reactive adhesive composition of the present invention.

[0161] In the case of double-sided tapes, it is preferable that these tapes have a three-layer structure (reactive adhesive composition - carrier layer - reactive adhesive composition), wherein the reactive adhesive compositions on both sides of the carrier layer are preferably the same reactive adhesive composition.

[0162] The term "tape" will be clear to those skilled in the art of adhesives. In the context of this invention, the term "tape" refers to all thin, sheet-like structures, i.e., structures having a primary extension in two dimensions, particularly films, film segments, and labels, preferably tapes and corresponding tape segments having an extended length and a finite width.

[0163] The carrier layer typically refers to a layer in a multilayer adhesive tape that decisively determines the tape's mechanical and physical properties, such as tear strength, ductility, insulation capability, or resilience. Conventional carrier materials are well-known to those skilled in the art and include, for example, woven fabrics, loosely woven fabrics, and plastic films, such as PET and polyolefin films. However, the carrier layer itself can also possess pressure-sensitive adhesive properties.

[0164] In the reactive tapes of the present invention, particularly pressure-sensitive tapes, the adhesive layer may be covered with a so-called release liner for transport, storage, or die-cutting. This release liner allows for trouble-free unwinding, for example, and protects the (pressure-sensitive) adhesive composition from contamination. These release liners typically consist of a silicone-coated plastic film (e.g., PET or PP) or a silicone-coated paper carrier on one or both sides.

[0165] The thickness of the adhesive layer in the reactive adhesive composition of the reactive tape of the present invention is preferably from 5 μm to 400 μm (measured using a commercially available thickness gauge, such as the DM2000 from Wolf Messtechnik GmbH). A layer thickness of 10 μm to 300 μm is more preferred, 30 μm to 200 μm is even more preferred, and 50 μm to 110 μm is most preferred. Higher layer thicknesses, such as up to 1000 μm, are conceivable and can be achieved with the reactive adhesive composition of the present invention. This is especially true when mounting components with large gap dimensions. The preferred layer thickness here is up to 1000 μm, more preferably up to 900 μm, and even more preferably up to 800 μm. To ensure internal strength before curing, these tapes typically have an internal carrier layer, which means that activation on both sides may be required in certain cases.

[0166] Especially for applications in the electronics industry that require precision die-cut parts, tapes with a carrier layer are preferred, preferably double-sided tapes with a three-layer structure (reactive adhesive composition - carrier layer - reactive adhesive composition), and preferably with a layer thickness between 40 µm and 400 µm.

[0167] The reactive adhesive compositions on both sides of the carrier layer are preferably the same reactive adhesive compositions.

[0168] Starting from the reactive adhesive compositions and reactive tapes of the present invention, the use of the reactive curable adhesive compositions or reactive curable tapes of the present invention for bonding two or more components or substrates, preferably at room temperature, by curing the reactive adhesive compositions is further disclosed.

[0169] The present invention describes a process for bonding two substrates, preferably at room temperature, using the reactive curable adhesive composition or the reactive curable tape of the present invention, wherein the tape is in the form of double-sided tape in this process, comprising the following steps: Apply a reactive curable adhesive composition or a reactive curable tape to a first substrate. The reactive curable adhesive composition or reactive curable tape is activated by irradiation with UV light, preferably UV light from a UV-LED lamp. The second substrate is bonded to an activated reactive curable adhesive composition or an activated reactive curable tape.

[0170] The irradiation in this process is preferably performed at a wavelength of 365 nm or 385 nm, more preferably at 365 nm. The corresponding UV-LED lamps are available from specialty retailers, such as LED Cube from Hönle (Dr. Hönle AG, Gilching, Germany). Furthermore, the process of this invention is characterized by an activation duration of less than 45 seconds, preferably less than 30 seconds, more preferably less than 15 seconds, even more preferably less than 10 seconds, and particularly less than 7 seconds. In particular, it has been found that activation / irradiation times of less than 15 seconds or 10 seconds are extremely suitable in this process, and these times are particularly advantageous because they allow for very short cycle times in industrial processes.

[0171] The present invention also provides the use of the reactive curable adhesive composition of the present invention or the reactive curable tape of the present invention as an adhesive in the production of electronic, optical or precision mechanical devices. In particular, portable electronic, optical or precision mechanical devices.

[0172] These portable devices are specifically designed for: Cameras, digital cameras, camera accessories (such as exposure meters, flash units, apertures, camera housings, lenses, etc.), movie cameras, video cameras, small computers (mobile computers, pocket computers, calculators), laptop computers, notebook computers, netbooks, ultrabooks, tablet computers, handheld devices, electronic diaries and notebooks (also known as electronic notebooks or personal digital assistants, PDAs, handheld computers), modems. Computer accessories and control units for electronic devices, such as mice, drawing tablets, graphics input tablets, microphones, speakers, game consoles, game controllers, remote control systems, remote controls, and touchpads; Monitors, displays, screens, touchscreens (touchscreen devices), projectors; Readers for e-books; Small television sets, pocket television sets, movie players, video players, radios (including small radios and pocket radios), portable player (Walkman) devices, portable CD player (Discman) devices, music players for CDs, DVDs, Blu-rays, cassette tapes, USB and MP3s, headphones, cordless phones, mobile phones, smartphones, two-way wireless devices, hands-free phones, pagers; Portable defibrillators, blood glucose monitors, blood pressure monitors, pedometers, and pulse monitors; Flashlight, laser pointer; Mobile detectors, optical magnifying glasses, telescopic devices, night vision devices, GPS devices, navigation devices, portable satellite communication interface devices; Data storage devices (USB sticks, external hard drives, memory cards); and wristwatches, digital watches, pocket watches, chain watches, stopwatches.

[0173] Experimental section: A. Raw materials used:

[0174] EEW: Epoxy Equivalent Weight

[0175] B. Production of poly(meth)acrylates: Table 1 – Composition of poly(meth)acrylates and comparative polymers

[0176] Polymers P1 and P4 are produced as follows.

[0177] 320 g of the monomer mixture specified in Table 1 and 273 g of ethyl acetate / isopropanol (96 / 04) were charged into a standard 4 L reactor for free radical polymerization. After purging the reactor with nitrogen for 45 min under 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 2 h. The reactor was then heated to 65°C in an external heating bath and the reaction was carried out at a constant temperature corresponding to this external temperature. 0.3 g of 2,2'-azobis(2-methylbutyronitrile) was added after 1 h of reaction time, and a further 0.3 g was added after 1.5 h. To reduce residual monomer, 0.12 g of di(4-tert-5-butylcyclohexyl) peroxydicarbonate was added after 6 h and again after 7.5 h. The mixture was diluted once with 160 g of ethyl acetate after 2 h and 4 h. The reaction was terminated after a 24-hour reaction time and cooled to room temperature.

[0178] C. Production of reactive adhesive compositions: The reactive adhesive composition was produced in the laboratory according to the amounts specified in the table below. An epoxy compound was added to the polymer present in a solvent, followed by the addition of a photoinitiator by stirring.

[0179] D. Production of reactive adhesive tapes as pressure-sensitive tapes: To produce reactive adhesive composition layers, i.e., carrier-free pressure-sensitive tapes, various reactive adhesive compositions were applied from solution to a conventional backing (silicone-coated polyester film) using laboratory coating equipment and then dried. The adhesive composition layers were approximately 21 cm × 30 cm in size and had a thickness of 100 ± 5 μm after drying. Drying was performed first at RT for 15 minutes and then at 120°C for 15 minutes in a laboratory drying oven, respectively. Immediately following drying, a second backing (silicone-coated polyester film with lower peel strength) was laminated onto the open side of the dried adhesive composition layer, respectively.

[0180] E. Testing Methods

[0181] Room temperature (RT) launch – Initial: The test provides information about the adhesive strength of the adhesive product in a direction perpendicular to the bonded surface. The test is provided with 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 central opening (hole) with a diameter of 9 mm, and a sample of the adhesive tape to be tested (in this case, the adhesive product), which is die-cut into the shape of a ring with an outer diameter of 18 mm and an inner diameter of 13 mm, thereby forming a ring with a bridge width of 5 mm.

[0182] Test specimens were produced from the three components described above by attaching the adhesive product to the center of the substrate (1) with the adhesive surface free. The temporary protective film (silicified PET liner) was then removed, and the specimens were tested using a 365 nm UV LED (Hönle AG) with a power of at least 4500 mJ / cm². 2 Activate the sample. Apply the composite concentrically to the substrate (2) with the now exposed side of the adhesive product within 2 minutes, i.e., in such a way that the circular holes in the substrate (2) are arranged exactly above the center of the circular first substrate 1 (thus the adhesive area is 151 mm). 2 The sample is then pressed under a pressure of at least 10 bar for at least 10 seconds to form a test specimen.

[0183] After pressing, the test specimens were conditioned at 23°C / 50% relative humidity (RH) for 72 hours. After storage, the adhesive bond was clamped into the sample holder, ensuring the adhesive level was aligned. The test specimens were inserted into the sample holder with the substrate (1) facing down, and the adhesive strength was measured in Zwick [Z020]. For the test, a steel punch with a diameter of 7 mm was passed through a circular opening in the substrate (2), and the force required to separate the circular substrate (1) from the square substrate (2) was measured. As an output value, the measured force was divided by the adhesive surface area, and the force was specified in MPa.

[0184] Three samples were tested for each product, and the average value was reported as a measure of adhesive strength.

[0185] Launch (Al-Al and SUS-SUS) – after 72 h in isopropanol / water at 40°C: To determine the chemical resistance of the adhesive, the ejection test specimen, constructed as further described above, was placed in a warm (40°C) isopropanol / water (70 / 30, i.e., 70% by volume to 30% by volume) bath for 72 h. After removal, the test specimen was readjusted at 23°C and 50% RH for one hour. The adhesive strength was then measured as described in the ejection – initial section.

[0186] To determine the adhesion strength (Al-Al) to aluminum, a 1 mm thick circular aluminum disc (21 mm in diameter) was selected as the substrate (1), and a 2 mm thick square aluminum substrate with a side length of 40 mm and a circular central opening (hole) with a diameter of 9 mm was selected as the substrate (2). The aluminum substrate was anodized E6 EV1 (alloy 5005A [AlMg1]).

[0187] To determine the adhesion strength to steel (SUS-SUS), a 3 mm thick circular steel disc (21 mm in diameter) was selected as the substrate (1), and a 2 mm thick square steel substrate with a side length of 40 mm and a circular central opening (hole) with a diameter of 9 mm was selected as the substrate (2). The steel substrates were made of VA-1.4301 steel (one side mirror polished).

[0188] F. Results

[0189] Table 2 – Comparison of the composition (all values ​​are parts by weight) and adhesive strength as an indicator of chemical resistance of reactive adhesive composition C1 and reactive adhesive compositions I1 to I4 of the present invention:

[0190] Table 3 – Comparison of the composition (all values ​​are parts by weight) and adhesive strength as an indicator of chemical resistance of reactive adhesive composition C2 and reactive adhesive compositions I5 to I7 of the present invention:

[0191] nd = not determinable.

[0192] Table 4 – Comparison of the composition (all values ​​are parts by weight) and adhesive strength as an indicator of chemical resistance of reactive adhesive composition C3 and reactive adhesive compositions I8 to I16 of the present invention:

[0193] In further experiments based on Example I9, the amount of benzyl cinnamate was increased to more than 15%, that is, to 17%.

[0194] In this case, the initial bond strength (room temperature roll-out – initial) for Al-Al and SUS-SUS was already so low that – understandably – no further experiments were conducted.

[0195] Table 5 – Comparison of the composition (all values ​​are parts by weight) and adhesive strength as an indicator of chemical resistance of reactive adhesive composition C4 and reactive adhesive compositions I17 to I18 of the present invention:

[0196] nd = unmeasurable.

[0197] All adhesive compositions I1 to I18 of the present invention exhibit sufficient to excellent initial bond strength (room temperature launch – initial), not listed in the table.

[0198] In particular, as can be seen from Tables 2 to 5, the embodiments of the present invention, however, exhibit sufficient to excellent adhesive strength even after immersion in a mixture of isopropanol and water for 72 hours.

[0199] Therefore, the adhesive compositions I1 to I18 of the present invention exhibit good to very good chemical resistance, which is generally improved compared to the comparative examples. Table 4 shows that the adhesive strength to steel is improved for all embodiments of the present invention, while it is equally (I10, I13 to I15) or similarly improved on aluminum. In Table 4, Examples I8, I9, I11 and I12 are particularly advantageous embodiments.

[0200] Compared to adhesive compositions C2 and C4, which exhibit acceptable initial bond strength in the push-out test, no chemical resistance is indicated because the bond failed during the immersion time in the isopropanol / water mixture, or at the latest by the time the sample used for the push-out test was prepared after removal from the mixture. Therefore, these values ​​are undeterminable (nd).

Claims

1. A reactive curable adhesive composition, comprising... (a) One or more (co)polymers; and (b) at least one epoxy compound; and (c) at least one photoinitiator for initiating cationic polymerization; and (d) At least one chemical compound comprising at least one phenyl group or a phenyl derivative substituted on a benzene ring.

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

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

4. The reactive curable adhesive composition according to any one of claims 1 to 3, characterized in that, The at least one chemical compound (d) includes the at least one phenyl group, or a phenyl derivative substituted on a benzene ring in a structural unit selected from Bz-O-, Ph-O- and derivatives of Bz-O- and Ph-O- substituted on a benzene ring, wherein Bz is benzyl and therefore phenylmethylene, O is oxygen and Ph is phenyl.

5. The reactive curable adhesive composition according to any one of claims 1 to 4, characterized in that, The at least one chemical compound (d) is selected from benzyl alcohol, phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane, phenyl ethylene oxide, phenyl glycidyl ether, benzyl cinnamate, benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol, vanillin, 2-phenoxyethyl acrylate, benzyl acrylate, cashew methacrylate, ω-phenyl oligoethylene glycol acrylate, 2-benzyloxyethanol, 4-benzyloxyphenol and butylphenol polyether-5 carboxylic acid, and preferably selected from benzyl alcohol, 2-phenoxyethanol, 3-ethyl-3-[(phenylmethoxy)methyl]-oxetane, phenyl ethylene oxide, phenyl glycidyl ether, benzyl cinnamate, benzyl acetate, 4-hydroxybenzyl alcohol, 4-methylbenzyl alcohol, cinnamaldehyde, cinnamyl alcohol, eugenol and vanillin, and more preferably selected from benzyl cinnamate, vanillin, benzyl alcohol and cinnamyl alcohol.

6. The reactive curable adhesive composition according to any one of claims 1 to 5, characterized in that, It is a reactive curable pressure-sensitive adhesive composition.

7. The reactive curable adhesive composition according to any one of claims 1 to 6, characterized in that, The one or more (co)polymers (a) are selected from poly(meth)acrylates, (meth)acrylate block copolymers, polyurethanes, polyvinyl acetals such as polyvinyl butyral, polysiloxanes, synthetic rubbers, polyesters, phenoxy polymers, polyvinyl alcohol, polyvinyl alcohol copolymers, and olefin-vinyl ester copolymers, preferably selected from poly(meth)acrylates, (meth)acrylate block copolymers, phenoxy polymers, polyvinyl alcohol, polyvinyl alcohol copolymers, polyvinyl acetals such as polyvinyl butyral, and ethylene-vinyl acetate copolymers (EVA or EVAC, poly(ethylene-copoly-vinyl acetate)), particularly selected from poly(meth)acrylates, (meth)acrylate block copolymers, and ethylene-vinyl acetate copolymers.

8. The reactive curable adhesive composition according to any one of claims 1 to 7, characterized in that, The at least one epoxy compound (b) is selected from alicyclic epoxy resins such as 3',4'-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl ester, bisphenol A diglycidyl ether (BADGE) resin, hydrogenated bisphenol A diglycidyl ether (BADGE) resin, epoxy-terminated nitrile rubber (ETBN), and epoxy-terminated butadiene rubber (EBN), more preferably selected from bisphenol A diglycidyl ether and hydrogenated bisphenol A diglycidyl ether.

9. The reactive curable adhesive composition according to any one of claims 1 to 8, characterized in that, The at least one photoinitiator (c) used to initiate cationic polymerization is selected from sulfonium salts and iodonium salts, wherein the cation of the photoinitiator is preferably selected from triarylsulfonium substituted with acetyl or methyl groups and diaryliodonium substituted on the phenyl group.

10. A reactive curable tape comprising at least one layer of a reactive curable adhesive composition according to any one of claims 1 to 9.

11. The reactive curable tape according to claim 10, characterized in that, It additionally includes a carrier layer and preferably includes another reactive curable adhesive composition according to any one of claims 1 to 9.

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

13. Use as an adhesive in the production of electronic, optical, or precision mechanical devices by any of the reactive curable adhesive compositions according to any one of claims 1 to 9 or the reactive curable tape according to claim 10 or 11.

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