Curable, electrically releasable, one-component (1K) structural adhesive composition

Abstract

The present invention relates to a (meth)acrylate monomer selected from the group consisting of: a) hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof; b) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-heptyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-non ...nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methyl The present invention relates to a curable, electrochemically releasable, one-component (1K) structural adhesive composition comprising: a) an electrolyte selected from the group consisting of 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-tetradecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a copolymerizable acid; d) an initiator; e) a core-shell toughening agent; and f) a toughening agent. The composition according to the present invention can withstand harsh conditions (high temperature and humidity) while maintaining adhesion and peel properties.

Description

[Technical Field]

[0001] Technical field of the invention The present invention relates to a curable, electrically releasable, one-component (1K) structural adhesive composition that, after cure, is capable of bonding substrates together and withstanding loads within a bonded composite structure, but is also capable of being electrochemically released from the particular substrate to which it is applied. [Background technology]

[0002] Technical Background of the Invention Adhesive bonds and polymer coatings are commonly used in the assembly and finishing of manufactured products. They replace mechanical fasteners such as screws, bolts, and rivets, providing bonds with reduced machining costs and greater adaptability in the manufacturing process. Adhesive bonds distribute stress evenly, reducing the potential for fatigue and sealing the joint from corrosive species.

[0003] Although adhesive bonding offers many advantages over mechanical fasteners, certain drawbacks must also be acknowledged. First, disassembly of adhesively bonded objects tends to be difficult when practically necessary. Second, when the adhesive is cured in situ to bond two substrates together, a cross-linked chemical network is formed that, in most cases, cannot be reused as an adhesive after disassembly of the adhesively bonded object. These drawbacks are clearly of concern in often resource-intensive industries where it is beneficial to recycle, reuse, or repurpose manufactured products.

[0004] Regarding the first identified drawback, adhesive removal by mechanical processes such as sandblasting or wire brushing is often impossible, in part because the adhesive is deposited between the substrates, making it impossible or difficult to abrade the substrate surfaces without corroding them. While decomposition with chemicals and / or high temperatures may be effective, it can be a time-consuming and complicated process, especially if one wishes to protect the surfaces of the substrates that have adhesive residue after treatment, and the harsh chemicals and / or harsh conditions required often remove virtually all of the adhesive and damage the separated substrates, rendering them unsuitable for further use.

[0005] As an illustrative example, it is clearly desirable to remove, replace, and / or recycle components of electronic devices, such as laptops and phones, that are attached to the device using adhesives. However, such adhesives are typically strong because they are designed to maintain their adhesion during drops and impacts, and over a wide range of operating temperatures and other environmental conditions. Thus, if care is not taken, adhesively bonded device components can be damaged or destroyed during component removal by mechanical handling, application of chemicals, or high temperatures.

[0006] Several authors have addressed these problems and attempted to develop releasable adhesive compositions that act to disrupt the bond at the adhesive / substrate interface when an electric current is passed through the cured composition.

[0007] U.S. Patent No. 7,465,492 describes a strippable composition comprising a matrix function comprising a monomer selected from the group consisting of acrylic, methacrylic, and combinations thereof; a free radical initiator; and an electrolyte, which provides the composition with sufficient ionic conductivity to support a Faradaic reaction in the bond formed between the composition and a conductive surface, thereby enabling the composition to be desorbed from the surface.

[0008] US 2007 / 0269659 describes a releasable adhesive composition at two interfaces that (i) includes a polymer and an electrolyte, (ii) promotes bonding of the two surfaces, and (iii) releases from both the anode and cathode surfaces in response to a voltage applied across both surfaces to form an anode interface and a cathode interface.

[0009] US 2008 / 0196828 describes a hot melt adhesive composition comprising a thermoplastic component and an electrolyte, which provides the composition with sufficient ionic conductivity to allow a faradaic reaction at the bond formed between the composition and the conductive surface and to allow the composition to detach from the surface.

[0010] WO2017 / 133864 describes a method for reversibly bonding a first substrate and a second substrate, wherein at least the first substrate is a non-conductive substrate, the method comprising: a) coating the surface of the non-conductive substrate with a conductive ink; b) applying an electrically releasable hot melt adhesive composition to the conductive ink-coated surface of the first substrate and / or the second substrate; c) contacting the first substrate and the second substrate such that the electrically releasable hot melt adhesive composition is interposed between the two substrates; d) forming an adhesive bond between the two substrates to provide bonded substrates; and e) applying a voltage to the bonded substrates, thereby substantially weakening the adhesion of at least one interface between the electrically releasable hot melt adhesive composition and the substrate surface.

[0011] WO2021 / 115771 A1 relates to a curable, one-component (1K) peelable adhesive composition comprising: a) an epoxy resin; b) a curing agent for the epoxy resin; c) an electrolyte; and d) a non-conductive filler; wherein the composition comprises at least one e) combination of a solubilizer and a toughening agent; and f) conductive particles.

[0012] WO 2022 / 179825 A1 relates to a curable, electrochemically releasable one-component (1K) adhesive composition comprising, based on the weight of the composition, 40 to 90 wt. % of i) at least one ethylenically unsaturated nonionic monomer; 0.1 to 30 wt. % of ii) a non-polymerizable electrolyte; 0.1 to 10 wt. % of iii) at least one radical-generating thermal initiator; 0 to 20 wt. % of iv) a filler; and 0 to 20 wt. % of v) a toughening agent. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 7,465,492 [Patent Document 2] US Patent Application Publication No. 2007 / 0269659 [Patent Document 3] US Patent Application Publication No. 2008 / 0196828 [Patent Document 4] International Publication No. 2017 / 133864 [Patent Document 5] International Publication No. 2021 / 115771 [Patent Document 6] International Publication No. 2022 / 179825 Summary of the Invention [Problem to be solved by the invention]

[0014] Despite the beneficial development of electrochemically releasable adhesive compositions, the solvated salts or electrolytes present in electrochemically releasable adhesives are inherently hygroscopic. Therefore, water accumulates to saturation levels over hours to days, affecting the long-term stability and performance of the adhesive. Therefore, there is a need for electrochemically releasable structural adhesives that can withstand harsh conditions (high temperature and humidity) while maintaining adhesion and release performance.

[0015] Brief description of the diagram FIG. 1 shows a bonded structure according to the present invention. FIG. 2 shows the initial delamination of the structure upon passing an electric current across it. [Means for solving the problem]

[0016] Summary of the Invention The present invention relates to a (meth)acrylate monomer selected from the group consisting of: a) hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof; b) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-heptyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-non ...nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methyl and f) a toughening agent.

[0017] The present invention relates to the cured product of the electrochemically releasable one-component (1K) structural adhesive composition according to the present invention.

[0018] The present invention also relates to the use of the electrochemically releasable one-component (1K) structural adhesive composition or cured product according to the present invention in electronic devices.

[0019] The present invention relates to a method for manufacturing a substrate, the method comprising: a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface; wherein an electrochemically releasable one-component (1K) structural adhesive composition or cured product according to the present invention is deposited between electrically conductive surfaces of a first and a second substrate.

[0020] The invention also encompasses a method of peeling off a bonded structure according to the invention, comprising the steps of: 1) applying a voltage across both surfaces to form an anodic interface and a cathodic interface, preferably a voltage of 5 to 70 V for 1 to 60 minutes; and 2) peeling the surfaces. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 shows a bonded structure according to the present invention. [Figure 2] FIG. 2 shows the initial delamination of the structure upon passing an electric current across it. DETAILED DESCRIPTION OF THE INVENTION

[0022] Detailed Description of the Invention The present invention will be described in more detail in the following passages. Each aspect described in this manner may be combined with one or more other aspects, unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with one or more other features indicated as being preferred or advantageous.

[0023] In the context of the present invention, the terms used shall be construed in accordance with the following definitions, unless the context indicates otherwise.

[0024] As used herein, the singular forms "a," "an," and "the" include both the singular and the plural reference unless the context clearly dictates otherwise.

[0025] As used herein, the terms "comprising," "comprises," and "comprised of" are synonymous with "including," "includes," "containing," or "contains" and are inclusive or open-ended and do not exclude additional, unrecited elements, components, or method steps. When used, the term "consisting of" is closed and excludes all additional components. Furthermore, the phrase "consisting essentially of" excludes additional significant components, but allows for the inclusion of minor components that do not materially alter the nature of the invention.

[0026] The recitation of numerical endpoints includes all numbers and fractions subsumed within the respective ranges and includes the recited endpoints.

[0027] All percentages, parts, ratios, etc. set forth herein are by weight unless otherwise specified.

[0028] When an amount, concentration, or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper value and a preferred lower value, any range obtained by combining any upper value or preferred value with any lower value or preferred value should be understood to be expressly disclosed, regardless of whether the resulting range is clearly stated in the context.

[0029] The terms "preferred," "preferably," "desirably," "particularly," "in particular," and their cognates are frequently used herein to draw attention to embodiments of the present disclosure that may offer particular benefits, under certain circumstances. However, the recitation of one or more preferred, desirable, or particular embodiments does not imply that other embodiments are not useful, and is not intended to exclude such other embodiments from the scope of the present disclosure.

[0030] As used throughout this application, the word "may" is used in its permissive, i.e., possible, rather than required, sense.

[0031] As used herein, the term "one-component (1K) composition" refers to a composition in which, during storage of the composition, the composition components are all mixed together, but the properties of the composition, including viscosity, remain consistent enough over the storage period to allow for successful utilization of the composition at a later time point.

[0032] By "two-component (2K) composition" is understood a composition in which the first and second components / parts must be stored in separate containers due to their (high) reactivity. The two components / parts are mixed only immediately before application, and then react, typically without additional activation, to form bonds, thereby forming a polymer network. Here, higher temperatures may be applied to accelerate the crosslinking reaction.

[0033] As used herein, the term "electrochemically releasable" means that, after the adhesive has cured, the bond strength can be weakened by at least 50% when a potential of 5V to 70V is applied for 1 to 60 minutes. The cured adhesive is applied between two substrates bonded by the adhesive, allowing a current to flow through the adhesive bond line. Bond strength is measured at room temperature by a tensile lap shear (TLS) test performed in accordance with EN 1465:2009 (German edition) Based on Adhesives - Determination of tensile lap-shear strength of bonded assemblies.

[0034] As used herein, the term "clean release" refers to the presence of a curable, electrochemically releasable, one-component (1K) structural adhesive composition on either the first or second substrate after peeling, meaning that either substrate is substantially free of adhesive. The term "substantially free of adhesive" as used herein means that no more than 5% adhesive remains on the substrate after peeling, preferably less than 3%, and more preferably less than 1%, upon visual inspection / assessment.

[0035] As used herein, the term "monomer" refers to a substance that can undergo a polymerization reaction to provide a building block for the chemical structure of a polymer. As used herein, the term "monofunctional" refers to having one polymerizable site. As used herein, the term "multifunctional" refers to having two or more polymerizable sites.

[0036] As used herein, "(meth)acryl" is an abbreviation for "acrylic" and / or "methacrylic." Thus, the term "(meth)acrylamide" collectively refers to acrylamide and methacrylamide.

[0037] As used herein, "structural adhesive" refers to an adhesive for bonding components of a load-bearing structure together. In other words, a structural adhesive is capable of holding two or more substrates together under stress.

[0038] As used herein, "stable under harsh conditions" means that after the adhesive has cured, it will not lose more than 50% of its bond strength even if it is stored in an artificial climate chamber at 65°C and 90% relative humidity for 1 week, preferably 2 weeks, more preferably 3 weeks, and even more preferably 3 months.

[0039] As used herein, the term "core-shell toughening agent" refers to a rubber particle core formed from a polymer primarily containing an elastomer or rubber-like polymer and a shell layer formed from a polymer grafted onto the core. The shell layer partially or entirely covers the surface of the rubber particle core during the graft polymerization process.

[0040] All references cited herein are incorporated by reference in their entirety.

[0041] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. For further guidance, definitions of terms are included to better understand the teachings of the present invention.

[0042] The present invention relates to a (meth)acrylate monomer selected from the group consisting of: a) hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof; b) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-heptyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-non ...nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methyl and f) a toughening agent.

[0043] The curable, electrochemically releasable, one-part (1K) adhesive composition of the present invention is a structural adhesive.

[0044] The compositions according to the present invention provide good initial adhesive strength and are effectively peelable, while also exhibiting high stability over time, i.e., stability even under high temperature and humidity conditions. The use of a compatible electrolyte in the hydrophobic adhesive matrix does not impair the stability of the final adhesive formulation (avoiding migration of ionic species and phase separation). The applicant has discovered that the combination of the adhesive matrix, electrolyte, and core-shell reinforcement agent and the mixture provides high stability under harsh storage conditions. Accelerated aging tests were carried out for up to three weeks in a climate chamber at 65°C and 90% relative humidity to mimic the conditions typically experienced by electronic devices in high temperature and humidity environments.

[0045] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention comprises a (meth)acrylate monomer.

[0046] The (meth)acrylate monomers form adhesive polymers. The adhesive polymers form linear or crosslinked networks, providing high strength and solvent resistance. The adhesive polymer must support the electrochemical reaction at the interface with the conductive substrate. Therefore, sufficient ion mobility through the polymer matrix is ​​required. In certain embodiments, the adhesive matrix should contain functional groups capable of coordinating ions from the electrolyte, such as alkoxy and / or oligoether groups.

[0047] Examples of (meth)acrylate monomers suitable for use in the present invention include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, tolyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxyethyl (meth)acrylate, 4-methoxyethyl (meth)acrylate, 5-methoxyethyl (meth)acrylate, 6-methoxyethyl (meth)acrylate, 7-methoxyethyl (meth)acrylate, 8-methoxyethyl (meth)acrylate, 9-methoxyethyl (meth)acrylate, 10-methoxyethyl (meth)acrylate, 11-methoxyethyl (meth)acrylate, 12-methoxyethyl (meth)acrylate, 13-methoxyethyl (meth)acrylate, 14-methoxyethyl (meth)acrylate, 15-methoxyethyl (meth)acrylate, 16-methoxyethyl (meth)acrylate, 17-methoxyethyl (meth)acrylate, 18-methoxyethyl (meth)acrylate, 19-methoxyethyl (meth)acrylate, 20-methoxyethyl (meth)acrylate, 21-methoxyethyl (meth)acrylate, 22-methoxyethyl (meth)acrylate, 23-methoxyethyl (meth)acrylate, 24-methoxyethyl (meth)acrylate, 25-methoxyethyl (meth)acrylate, 26-methoxyethyl (meth)acrylate, 27-methoxyethyl (meth)acrylate, 28-methoxyethyl (meth)acrylate, 29-methoxyethyl (meth)acrylate, 29-methoxyethyl (meth)acrylate, 26-methoxyethyl (meth)acrylate, 27-methoxyethyl (meth)acrylate, 2 butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, isobornyl (meth)acrylate, 2-aminoethyl (meth)acrylate, y-(meth)acryloyloxypropyltrimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluorome (meth)acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof.

[0048] The (meth)acrylate monomer is selected from the group consisting of hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof.

[0049] These monomers are preferred as they provide good adhesive strength as well as good bond strength to metal and glass substrates.

[0050] Commercially available (meth)acrylate monomers suitable for use in the present invention include, but are not limited to, methyl methacrylate from Sigma Aldrich, isobornyl acrylate and isobornyl methacrylate from Sartomer, 2-hydroxyethyl methacrylate from Acros Organics, and 2-hydroxypropyl methacrylate from Alfa Aesar.

[0051] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 20 to 55%, preferably 23 to 52%, more preferably 26 to 50% (meth)acrylate monomer based on the total weight of the composition.

[0052] These (meth)acrylate monomer amounts are preferred because they provide desirable viscosity, adhesion, and mechanical properties. Amounts greater than 55% or less than 20% may adversely affect viscosity, adhesion, and mechanical properties.

[0053] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention comprises an electrolyte.

[0054] A suitable electrolyte exhibits good compatibility with the aforementioned polymer matrix. Furthermore, the electrolyte is preferably uniformly dispersed in the polymer matrix. Good dispersion helps achieve better stability against harsh storage conditions. Furthermore, the electrolyte preferably provides sufficient ionic conductivity to support the electrochemical reaction at the interface with the conductive material.

[0055] The electrolyte may be of formula (I) or formula (II): JPEG2025534000000001.jpg2869[In the formula, R 1 , R 2 , R 3 , R 4 and R 5 are independently hydrogen, C1-C 18 Alkyl, C3-C 18 Cycloalkyl, C6-C 18 Aryl, C7-C 24 Aralkyl, C2-C 20 Alkenyl, -C(O)R q , —C(O)OH, —CN, or —NO2; R q is C1-C6 alkyl; and X - is the counteranion] The compound may contain or consist of at least one salt satisfying the following formula:

[0056] The electrolytes were 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-heptyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. midazolium bis(trifluoromethylsulfonyl)imide, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-tetradecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, and mixtures thereof.

[0057] The above electrolytes are preferably used because they are hydrophobic and enhance the stability of the composition under harsh conditions. Furthermore, these electrolytes contain alkyl chains that promote compatibility with the polymer matrix.

[0058] Commercially available electrolytes suitable for use in the present invention include, but are not limited to, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM NTF2) from Sigma Aldrich, Cyphos IL 109 from Solvay, and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide from Iolitec.

[0059] In the curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention, the electrolyte may be present in an amount of 6 to 25%, preferably 7 to 23%, more preferably 10 to 20%, based on the total weight of the composition.

[0060] These electrolyte amounts are preferred because, although a good release effect may be obtained if the amount is more than 25%, curing may be incomplete, which may adversely affect the initial adhesion, while a low amount, mainly 6% or less, may not provide a release effect.

[0061] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention comprises a copolymerizable acid.

[0062] Preferably, the copolymerizable acid is selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate phosphate ester, hydroxypropyl (meth)acrylate phosphate ester, and mixtures thereof.

[0063] The copolymerizable acids described above are preferred as they are believed to improve the adhesive properties of the composition.

[0064] Commercially available copolymerizable acids suitable for use in the present invention include, but are not limited to, methacrylic acid from Sigma Aldrich and 2-hydroxyethyl (meth)acrylate phosphate from Sartomer.

[0065] In the curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention, the copolymerizable acid can be present in an amount of 5 to 20%, preferably 7 to 18%, more preferably 9 to 16%, based on the total weight of the composition.

[0066] The amount of these copolymerizable acids is preferred because more than 20% can cause corrosion problems, and less can cause incomplete curing and therefore reduced initial adhesive properties.

[0067] Acrylic polymers are formed by radical polymerization, and therefore, the curable, electrochemically releasable, one-component (1K) structural adhesive compositions according to the present invention include an initiator.

[0068] Suitable initiators for use in the present invention are peroxides. While certain peroxides, such as dialkyl and diaryl peroxides, are useful initiators, hydroperoxides are also an important class of initiators for the present invention. In this regard, while hydrogen peroxide itself may be used, it is preferred to use an organic hydroperoxide. While not intending to limit the present invention, representative hydroperoxide compounds have the general formula: R p OOH [In the formula, R p is a hydrocarbon group containing up to 18 carbon atoms, and Preferably, in the formula, R p is C1-C 12 Alkyl, C6-C 18 Aryl or C7-C 18 an aralkyl group] It has.

[0069] Preferably, the initiator is selected from the group consisting of tert-butyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, tert-butyl peroxybenzoate, diacetyl peroxide, benzoyl peroxide, tert-butyl peracetate, lauryl peroxide, and mixtures thereof; more preferably, the initiator is benzoyl peroxide.

[0070] The above initiators are preferred because they function well within the overall composition.

[0071] Commercially available initiators suitable for use in the present invention include, but are not limited to, benzoyl peroxide available from PanReac AppliChem.

[0072] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 0.1 to 7%, preferably 0.5 to 6%, more preferably 1 to 5% initiator, based on the total weight of the composition.

[0073] The amount of these initiators is preferable because if the amount exceeds 7%, the initiator becomes excessive and unwanted reactions may adversely affect the properties of the adhesive composition, whereas if the amount is low, mainly less than 0.1%, it may cause incomplete curing, and therefore, the initial adhesive strength and mechanical properties may be poor.

[0074] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention comprises a core-shell toughening agent.

[0075] The applicant has discovered that the combination of a defined (meth)acrylate monomer and a defined electrolyte with a core-shell toughening agent may improve the stability of the adhesive composition under harsh conditions.

[0076] The core-shell toughening agents suitable for use in the present invention may be a single core-shell toughening agent or a mixture of two or more core-shell toughening agents, preferably having a shell comprised of a polymer or copolymer of one or more monomers selected from the group consisting of methyl methacrylate, styrene, acrylonitrile, acrylic acid, (meth)acrylamide, and mixtures thereof; a homopolymer of butadiene; a homopolymer of isoprene; a copolymer of butadiene and a vinyl aromatic monomer, (meth)acrylonitrile, or (meth)acrylate; a copolymer of isoprene and a vinyl aromatic monomer, (meth)acrylonitrile, or (meth)acrylate; polybutyl acrylate; polydimethylsiloxane; crosslinked polydimethylsiloxane, and mixtures thereof.

[0077] The core-shell tougheners described above are preferred because they impart improved properties.

[0078] Commercially available core-shell tougheners suitable for use in the present invention include, but are not limited to, Paraloid EXL 2650 A, EXL 2655, and EXL2691 A manufactured by Dow Chemical Company, Clearstrength® XT100 manufactured by Arkema Inc., and the Kane Ace® MX series manufactured by Kaneka Corporation.

[0079] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 2 to 15%, preferably 3 to 11%, more preferably 3 to 10% of the core-shell toughening agent based on the total weight of the composition.

[0080] Amounts of core-shell toughener greater than 15% may result in excessive viscosity which may impair the mechanical performance of the composition, while amounts less than 2% may adversely affect aging resistance.

[0081] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention includes a toughening agent. In this regard, it is noted that this toughening agent is distinct from a core-shell toughening agent.

[0082] Furthermore, the applicant has discovered that by combining a defined (meth)acrylate monomer and a defined electrolyte with a toughening agent, the stability of the adhesive composition under harsh conditions can be improved.

[0083] Toughening agents suitable for use in the present invention may be reactive toughening agents, non-reactive toughening agents, or mixtures thereof.

[0084] Suitable non-reactive toughening agents may be selected from the group consisting of methacrylate terminated polybutadiene rubber, carboxyl terminated copolymers of butadiene and acrylonitrile, carboxyl terminated styrene butadiene rubber, carboxyl terminated styrene butadiene styrene rubber, and mixtures thereof.

[0085] Suitable reactive toughening agents may be selected from the group consisting of ethylene / propylene / diene terpolymers; (meth)acrylonitrile-butadiene copolymers; (meth)acrylonitrile-styrene copolymers; (meth)acrylonitrile-butadiene-styrene copolymers; styrene-isoprene-styrene copolymers; styrene-butadiene-styrene copolymers; ABA triblock copolymers in which blocks A and B are composed of C1-C8 alkyl (meth)acrylates, each having a different glass transition temperature (Tg), such as copolymers of polymethyl methacrylate and poly-n-butyl acrylate (PMMA-PnBA-PMMA) and PMMA-(PnBA / 2-EHA)-PMMA; triblock copolymers based on methyl (meth)acrylate (MMA), n-butyl acrylate (nBA) and 2-ethylhexyl acrylate (2-EHA), and mixtures thereof.

[0086] The reactive tougheners described above are preferred because they exhibited good overall performance without adversely affecting other properties.

[0087] Commercially available reactive tougheners suitable for use in the present invention include, but are not limited to, HYPRO 2000X168 LC VTB manufactured by Huntsman.

[0088] Commercially available non-reactive tougheners suitable for use in the present invention include, but are not limited to, Blendex 338 manufactured by Galata Chemicals, Kurarity LA 4285 manufactured by Kuraray, and Nipol 1472X manufactured by Zeon Chemicals.

[0089] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 3 to 35%, preferably 6 to 26%, more preferably 11 to 23% toughener, based on the total weight of the composition.

[0090] Amounts of reactive toughener greater than 35% may result in excessive viscosity which may impair the mechanical performance of the composition, while amounts below 3% may adversely affect aging resistance.

[0091] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may further comprise a urethane (meth)acrylate oligomer, which improves the mechanical properties of the composition.

[0092] Suitable urethane acrylate oligomers may be di- or tri-functional aliphatic urethane (meth)acrylate oligomers, or di- or tri-functional aromatic urethane (meth)acrylate oligomers.

[0093] The urethane (meth)acrylate oligomer may be prepared by reacting a polyfunctional (meth)acrylate having a hydroxyl group with a polyisocyanate. The polyfunctional isocyanate may include methylene dicyclohexyl isocyanate or 1,6-hexamethylene diisocyanate. The hydroxy-functionalized acrylate may include a hydroxyalkyl acrylate such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, or polyethylene glycol acrylate. In one embodiment, the polyfunctional urethane acrylate oligomer may include the reaction product of a polyester polyol, methylene dicyclohexyl isocyanate, and hydroxyethyl acrylate.

[0094] Commercially available urethane (meth)acrylate oligomers suitable for use in the present invention include, but are not limited to, aliphatic urethane acrylates such as CN-9002, CN9014 NS, CN-980, CN-981, CN-9019, and CN1993CG manufactured by Sartomer Company Inc.; and aromatic urethane triacrylate CN970A60 manufactured by Sartomer.

[0095] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 15-30%, preferably 18-28%, more preferably 20-26% of the urethane (meth)acrylate oligomer based on the total weight of the composition.

[0096] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may further comprise a filler, the presence of which may serve to adjust the viscosity of the composition and to reduce the coefficient of thermal expansion of the adhesive.

[0097] The shape of the particles employed as fillers is not intended to be particularly limited, and acicular, spherical, ellipsoidal, cylindrical, bead-like, cubic, and platelet-like particles may be used alone or in combination. Furthermore, the use of aggregates of multiple particle types is also contemplated. Similarly, the size of the particles employed as fillers is not intended to be particularly limited. However, such fillers have conventionally had an average volume particle size, as measured by laser diffraction / scattering, of 0.01 to 1500 μm, e.g., 0.1 to 1000 μm, or 0.1 to 500 μm.

[0098] Exemplary fillers include, but are not limited to, barium sulfate, calcium carbonate, calcium oxide, calcium metasilicate, silica, fumed silica, sand, quartz, zeolite, bentonite, magnesium carbonate, diatomaceous earth, alumina, clay, talcum, flint, mica, glass powder, zinc oxide, and other ground mineral substances. Short fibers such as glass fiber, glass filament, polyacrylonitrile, carbon fiber, polyethylene fiber, etc. may also be added.

[0099] Preferably, the filler is selected from the group consisting of calcium carbonate; calcium oxide; calcium metasilicate; zinc oxide; talcum; fumed silica; silica; barium sulfate; and mixtures thereof.

[0100] The use of precipitated and / or fumed (pyrogenic) silica as a rheology control agent in the present compositions is particularly preferred, and such precipitated or pyrogenic silica desirably has a viscosity of 25 to 500 m as measured by nitrogen adsorption according to DIN 66131. 2 / g, e.g., 100-250m 2 / g BET surface area.

[0101] Commercially available fillers suitable for use in the present invention include, but are not limited to, Aerosil 200 from Evonik Industries and ZnO from Sigma Aldrich.

[0102] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 0.01 to 10%, preferably 0.05 to 7%, more preferably 0.1 to 6% filler, based on the total weight of the composition.

[0103] These ranges are preferred because they provide the composition with an ideal viscosity: too much filler makes the viscosity too high, and too little makes the viscosity too low.

[0104] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may further comprise a linear block copolymer.

[0105] A suitable linear block copolymer for use in the present invention is based on styrene and butadiene and has 40% by weight bound styrene.

[0106] Commercially available linear block copolymers suitable for use in the present invention include, but are not limited to, Kraton D1155 manufactured by Kraton Corporation.

[0107] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 0.1 to 10%, preferably 1 to 8%, more preferably 2 to 6% of the linear block copolymer based on the total weight of the composition.

[0108] The composition according to the present invention may further comprise a conductive filler. The shape of the particles employed as the conductive filler is not intended to be particularly limited, and acicular, spherical, ellipsoidal, cylindrical, bead-like, cubic, or platelet-like particles may be used alone or in combination. Furthermore, the use of aggregates of multiple particle types is also contemplated. Similarly, the size of the particles employed as the conductive filler is not intended to be particularly limited. However, such conductive fillers conventionally have an average volume particle size of 1 to 500 μm, e.g., 1 to 200 μm, as measured by laser diffraction / scattering.

[0109] Exemplary conductive fillers include, but are not limited to, silver; copper; gold; palladium; platinum; nickel; gold- or silver-coated nickel; carbon black; carbon fiber; carbon nanotubes; graphite; aluminum; indium tin oxide; silver-coated copper; silver-coated aluminum; metal-coated glass spheres; metal-coated fillers; metal-coated polymers; silver-coated fiber; silver-coated spheres; antimony-doped tin oxide; conductive nanospheres; nanosilver; nanoaluminum; nanocopper; nanonickel; carbon nanotubes; and mixtures thereof.

[0110] Preferably, the conductive filler is selected from the group consisting of silver and carbon black and mixtures thereof.

[0111] The curable, electrochemically releasable, one-component (1K) structural adhesive composition according to the present invention may have 0.01 to 10%, preferably 0.05 to 7%, more preferably 0.1 to 6% of conductive filler, based on the total weight of the composition.

[0112] Curable, electrochemically releasable, one-component (1K) structural adhesive compositions according to the present invention may further comprise adjuvants and additives that can impart improved properties to these compositions. For example, the adjuvants and additives may impart one or more of improved elastic properties, improved elastic recovery, longer effective processing time, faster cure time, and lower residual tack. Such adjuvants and additives include solubilizers, plasticizers, stabilizers including UV stabilizers, antioxidants, reactive diluents, drying agents, adhesion promoters, fungicides, flame retardants, color pigments or color pastes, and / or, optionally, minor amounts of non-reactive diluents.

[0113] Such adjuvants and additives can be used in any desired combination and proportion, provided that they do not adversely affect the properties and essential characteristics of the composition. Although there may be some exceptions, these adjuvants and additives should not comprise more than 20% by weight of the composition as a whole, and preferably should not comprise more than 10% by weight of the composition.

[0114] To form a curable, electrochemically releasable one-component (1K) structural adhesive composition, the ingredients listed above are mixed together. To form a one-component (1K) curable composition, the components of the composition are combined and intimately mixed under conditions that inhibit or prevent reaction of the reactive components. This may include mixing conditions that limit or prevent exposure to moisture, heat, or radiation, or that limit or prevent activation of the constituent latent catalysts. Therefore, the components are mechanically mixed in predetermined amounts under anhydrous conditions, without intentional heating or light exposure, using a static or dynamic mixer, for example.

[0115] The present invention relates to the cured product of the electrochemically releasable one-component (1K) structural adhesive composition according to the present invention.

[0116] Curing of the applied compositions according to the invention typically occurs at temperatures ranging from 80°C to 140°C, preferably from 100°C to 120°C. Curing times are from 10 to 120 minutes, preferably from 30 to 60 minutes. The appropriate temperature will depend on the particular compounds present and the desired cure rate, and can be determined in each individual case by one skilled in the art, using simple preliminary tests if necessary.

[0117] Electrochemically releasable one-component (1K) structural adhesive compositions or cured products thereof according to the present invention can be used in electronic devices.

[0118] Non-limiting examples of electrical devices include handheld devices, laptops, white goods, automotive applications, and aerospace applications.

[0119] The present invention also relates to a bonded structure comprising: a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface, wherein an electrochemically releasable one-component (1K) structural adhesive composition or cured product is deposited between the electrically conductive surfaces of the first and second substrates.

[0120] The initial use of one-component (1K) curable compositions in forming bonded structures will now be described. The aforementioned compositions are applied to a material layer and then cured in situ. It is often desirable to pretreat the relevant surface to remove foreign matter before applying the composition; this step can promote subsequent adhesion of the composition thereto, if applicable. Such treatments are known in the art and can be carried out in a single or multi-step process, consisting of, for example, etching with an acid suitable for the substrate and, optionally, an oxidizing agent; ultrasonic treatment; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric plasma treatment, and flame plasma treatment; immersion in an aqueous alkaline degreasing bath; treatment with an aqueous cleaning emulsion or solution; treatment with a cleaning solvent, such as carbon tetrachloride or trichloroethylene or alcohols such as hexanol and isopropanol or hydrocarbons such as ethyl acetate; and rinsing, preferably with deionized or demineralized water. If an aqueous alkaline degreasing bath is used, any remaining degreaser on the surface is preferably removed by rinsing the substrate surface with deionized or demineralized water.

[0121] In some embodiments, adhesion of the coating composition of the present invention to a preferably pretreated substrate can be promoted by applying an initiator thereto. Indeed, an initiator composition may be necessary to ensure effective fixing and / or cure time of the adhesive composition to an inert substrate.

[0122] The composition according to the invention is then applied to the surface of the preferably pre-treated, optionally primed substrate by conventional application methods such as bead dispensing, brushing, roll coating, doctor blade application and printing methods.

[0123] As described above, the present invention provides a bonded structure comprising a first substrate having an electrically conductive surface and a second substrate having an electrically conductive surface, wherein a cured electrochemically releasable one-component (1K) adhesive composition as defined herein and in the appended claims is deposited between the first and second substrates. To produce such a structure, the adhesive composition may be applied to at least one inner surface of the first and / or second substrates, after which the two layers may be subsequently brought into contact, optionally under pressure, so that the electrically releasable adhesive composition is interposed between the two substrates.

[0124] It is recommended that the composition be applied to the surface at a wet film thickness of 10 to 500 μm.

[0125] The initial bonding and subsequent debonding of the compositions of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a bonded structure according to the present invention; and Figure 2 shows the initial debonding of the structure by passing an electric current across the structure.

[0126] As shown in accompanying Figure 1, a bonded structure is provided in which a cured adhesive layer (10) is deposited between two conductive substrates (11). Each layer of conductive substrate (11) is in electrical contact with a power source (13), which may be a battery or a direct current (DC) alternating current power source. While the positive and negative poles of the power source (13) are shown in one fixed position, those skilled in the art will of course recognize that the polarity of the system can be reversed.

[0127] The two conductive substrates (11) are shown in the form of layers that can be composed of, among other things, metal films; metal sheets; metal meshes or grids; vapor-deposited metal particles; resin materials rendered conductive by virtue of conductive elements disposed therein; or conductive oxide layers. Exemplary conductive elements include silver filaments, single-walled carbon nanotubes, and multi-walled carbon nanotubes. Exemplary conductive oxides include doped indium oxides such as indium tin oxide (ITO); doped zinc oxide; antimony tin oxide; cadmium stannate; and zinc stannate. Regardless of the choice of conductive material, those skilled in the art will recognize that the effectiveness of the peeling operation may be reduced if the conductive substrate (11) is in the form of a grid or mesh, which limits contact with the cured adhesive (10) layer.

[0128] The present invention also relates to a method for peeling a bonded structure, the method comprising the steps of: 1) applying a voltage, preferably 5 to 70 V, to both surfaces to form an anodic interface and a cathodic interface for 1 to 60 minutes, and 2) peeling the surfaces. Preferably, the applied voltage is 20 to 50 V for 10 to 300 minutes.

[0129] When a voltage is applied between the conductive substrates (11), a current is supplied to the adhesive composition (10) deposited therebetween. This induces an electrochemical reaction at the interface of the substrates (11) and the adhesive composition, which is understood to be oxidative at the positively charged anodic interface and reductive at the negatively charged or cathodic interface. This reaction is believed to weaken the adhesive bond between the substrates, allowing for easy removal of the strippable composition from the substrates.

[0130] However, it should be noted that the composition of adhesive layer (10) can be tailored so that delamination occurs from either the positive or negative interface, or both simultaneously. In some embodiments, applying a voltage across the surfaces to form an anodic and cathodic interface results in delamination at both the anodic and cathodic adhesive / substrate interfaces simultaneously. In other embodiments, reversing the polarity can result in delamination at both substrate / adhesive interfaces simultaneously.

[0131] After peeling, it is desirable that the adhesive composition be located only on the first substrate or the second substrate, with one substrate being substantially free of adhesive. [Example]

[0132] Example Methyl methacrylate (MMA) from Sigma Aldrich Methacrylic acid (MAA) from Sigma Aldrich 2-Hydroxyethyl Methacrylate (HEMA) from Acros Organics 2-Hydroxypropyl methacrylate (HPMA) from Alfa Aesar Isobornyl acrylate (IBOA) from Sartomer Isobornyl methacrylate (IBOMA) from Sartomer Difunctional aliphatic urethane methacrylate oligomer CN1993CG from Sartomer 2-Hydroxyethyl methacrylate phosphate SR9054 from Sartomer Clearstrength XT core-shell toughener (methyl methacrylate-butadiene-styrene, MBS) from Arkema Inc. A toughening agent based on the ABS terpolymer Blendex 338 from Galata Chemicals Toughening agent based on acrylonitrile butadiene rubber Nipol 1472X from Zeon Chemicals A reactive toughening agent based on Huntsman's methacrylate-terminated polybutadiene HYPRO 2000X168 LC A toughening agent based on Kurarity LA 4285, an acrylic block copolymer manufactured by Kuraray. Kraton D1155, a styrene and butadiene-based linear block copolymer with 40% styrene by weight, manufactured by Kraton Corporation Zinc oxide ZnO from Sigma Aldrich Aerosil 200 hydrophilic fumed silica from Evonik Industries Benzoyl Peroxide BPO from PanReac AppliChem 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide BMIM NTf2 from Sigma Aldrich Trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide Cyphos IL 109 from Solvay 1-Dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide DDMIM NTf2 from Iolitec

[0133] Example 1 The compositions were prepared according to Table 1. All compositions according to Compositions 1 to 3 had a hydrophobic final matrix.

[0134] First, the tougheners Blendex 338 and Nipol 1472X were dissolved in the respective acrylic monomers overnight. A stirring plate may be used to facilitate dissolution. All other ingredients were added, and BMIM NTf2 and DDMIM NTf2 were used as reference electrolytes, which showed good stability characteristics based on compositions 1 to 3. The final mixture was obtained by speed-mixing all ingredients in one pot at once at 3000 rpm for 1 minute three times in a row, with a 5-minute delay to allow the mixture to cool.

[0135] [Table 1]

[0136] The substrate used for all formulations was aluminum (AA6016). The aluminum was cut into pieces measuring 2.5 cm x 10 cm and 1.25 mm thick. Glass beads (100-200 microns in diameter) were used as spacers to control the thickness of the coating composition applied between the two substrates. Tensile lap shear (TLS) was measured at room temperature according to EN 1465:2009 (German version) Based on Adhesives - Determination of tensile lap-shear strength of bonded assemblies.

[0137] The adhesive overlap area for each substrate listed was 2.5 cm x 1.0 cm, with a 0.1 cm (40 mil) adhesive thickness. The applied adhesive composition was cured at 80°C for 30 minutes and then 120°C for 30 minutes in the overlap area. The bonded structures were then stored at room temperature for 24 hours before initial tensile testing, or stored in a climate chamber at 65°C and 90% relative humidity for accelerated aging testing. After 24 hours of storage, the tensile lap shear strength was measured before and after applying a constant potential of 50 V to the adhesive layer for 30 minutes, and after storage in a climate chamber at 65°C and 90% relative humidity. The results are shown in Table 2 below.

[0138] [Table 2]

[0139] Compositions 1 to 3 all exhibited good performance. In particular, Compositions 2 and 3 all exhibited excellent stability and peeling performance even after storage at 65°C and a relative humidity of 90% for one week.

[0140] Example 2 Compositions were prepared according to Table 3. Compositions 4 and 5 additionally contained an impact modifier and a tackifier. Additionally, acid acrylic phosphate SR9054 was replaced with methacrylic acid. Again, to obtain a hydrophobic final matrix, a mixture of MMA and HPMA was tested. The toughening agents Blendex 338, Clearstrength XT 100, and Nipol 1472X were first dissolved in HPMA, while Kurarity LA 4285 and Kraton D1155 were separately dissolved in MMA. A stir plate may be used to expedite the dissolution process. After dissolution, both mixtures were combined in one pot, and all other ingredients were added. DDMIM NTf2 was used as a reference electrolyte, demonstrating good hydrophobicity based on compositions 1-3. The final mixture was obtained by speed-mixing all ingredients in one pot at once for 1 minute at 3000 rpm three times in succession, with a 5-minute delay to allow the mixture to cool.

[0141] [Table 3]

[0142] The substrate used for all formulations was aluminum (AA6016). The aluminum was cut into pieces measuring 2.5 cm x 10 cm and 1.25 mm thick. Glass beads (100-200 microns in diameter) were used as spacers to control the thickness of the coating composition applied between the two substrates. Tensile lap shear (TLS) was measured at room temperature according to EN 1465:2009 (German version) Based on Adhesives - Determination of tensile lap-shear strength of bonded assemblies.

[0143] The adhesive overlap area for each substrate listed was 2.5 cm x 1.0 cm, with a bond thickness of 0.1 cm (40 mils). The applied adhesive composition was cured in the overlap area at temperatures of 80°C for 30 minutes and 120°C for 30 minutes. The bonded structures were then stored at room temperature for 24 hours before initial tensile testing or in a climate chamber at 65°C and 90% relative humidity for accelerated aging testing. After 24 hours of storage, tensile lap shear strength values ​​were measured before and after applying a constant potential of 50 V to the adhesive layer for 30 minutes, and after storage in a climate chamber at 65°C and 90% relative humidity. The results are shown in Table 4 below.

[0144] [Table 4]

[0145] Both formulations of Compositions 4 and 5 were extremely stable. Composition 4, when MAA was used, exhibited slightly lower early strength compared to Composition 5, but remained more stable after storage at 65°C and 90% relative humidity for up to 3 weeks. Electrochemical stripping performance was excellent for both compositions.

[0146] Example 3 The composition was prepared according to Table 5. All ingredients were added together and speed mixed at 3000 rpm for 1 minute three times in succession with a 5 minute delay to allow the preparation to cool.

[0147] [Table 5]

[0148] The substrate used for all formulations was aluminum (AA6016). The aluminum was cut into pieces measuring 2.5 cm x 10 cm and 1.25 mm thick. Glass beads (100-200 microns in diameter) were used as spacers to control the thickness of the coating composition applied between the two substrates. Tensile lap shear (TLS) was measured at room temperature according to EN 1465:2009 (German version) Based on Adhesives - Determination of tensile lap-shear strength of bonded assemblies.

[0149] The adhesive overlap area for each substrate listed was 2.5 cm x 1.0 cm, with a bond thickness of 0.1 cm (40 mils). The applied adhesive composition was cured in the overlap area at 80°C for 30 minutes and 120°C for 30 minutes. The bonded structures were then stored at room temperature for 24 hours before initial tensile testing or in a climate chamber at 65°C and 90% relative humidity for accelerated aging testing. Tensile lap shear strength values ​​are reported in Table 6 below.

[0150] [Table 6]

[0151] The core-shell toughening agent and composition 6 without toughening agent did not exhibit good stability after storage at 65° C. and 90% relative humidity for 1 day.

Claims

1. a) a (meth)acrylate monomer selected from the group consisting of hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate, and mixtures thereof; b) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-heptyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-decyl-3-methylimidazolium an electrolyte selected from the group consisting of 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-octadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a copolymerizable acid; d) initiator; e) a core-shell toughening agent; and f) Reinforcing Agents 1. A curable, electrochemically releasable, one-component (1K) structural adhesive composition comprising:

2. 10. The curable electrochemically releasable one-component (1K) structural adhesive composition of claim 1, wherein the (meth)acrylate monomer is present in an amount of 20-55%, preferably 23-52%, and more preferably 26-50%, based on the total weight of the composition.

3. 3. The curable electrochemically releasable one-component (1K) structural adhesive composition of claim 1 or 2, wherein the electrolyte is present in an amount of 6 to 25%, preferably 7 to 23%, more preferably 10 to 20%, based on the total weight of the composition.

4. 4. The curable, electrochemically releasable, one-component (1K) structural adhesive composition of claim 1, wherein the copolymerizable acid is selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate phosphate ester, hydroxypropyl (meth)acrylate phosphate ester, and mixtures thereof.

5. 5. The curable electrochemically releasable one-component (1K) structural adhesive composition according to any of claims 1 to 4, wherein the copolymerizable acid is present in an amount of 5 to 20%, preferably 7 to 18%, more preferably 9 to 16%, based on the total weight of the composition.

6. 6. The curable electrochemically releasable one-component (1K) structural adhesive composition according to any of claims 1 to 5, wherein the initiator is a peroxide, preferably selected from the group consisting of tert-butyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, tert-butyl peroxybenzoate, diacetyl peroxide, benzoyl peroxide, tert-butyl peracetate, lauryl peroxide, and mixtures thereof; more preferably the initiator is benzoyl peroxide.

7. 7. The curable electrochemically releasable one-component (1K) structural adhesive composition according to any of claims 1 to 6, wherein the initiator is present in an amount of 0.1 to 7%, preferably 0.5 to 6%, more preferably 1 to 5%, based on the total weight of the composition.

8. 8. The curable, electrochemically releasable one-component (1K) structural adhesive composition of any of claims 1 to 7, wherein the core-shell toughening agent comprises a single core-shell toughening agent or a mixture of two or more core-shell toughening agents, preferably having a shell comprising a polymer or copolymer of one or more monomers selected from the group consisting of methyl methacrylate, styrene, acrylonitrile, acrylic acid, (meth)acrylamide, and mixtures thereof; and a core comprising a homopolymer or copolymer selected from the group consisting of a homopolymer of butadiene; a homopolymer of isoprene; a copolymer of butadiene and a vinyl aromatic monomer, (meth)acrylonitrile, or (meth)acrylate; a copolymer of isoprene and a vinyl aromatic monomer, (meth)acrylonitrile, or (meth)acrylate; polybutyl acrylate; polydimethylsiloxane; crosslinked polydimethylsiloxane, and mixtures thereof.

9. 9. The curable, electrochemically debondable, one-component (1K) structural adhesive composition of any of claims 1 to 8, wherein the core-shell toughening agent is present in an amount of 2-15%, preferably 3-11%, more preferably 3-10%, based on the total weight of the composition.

10. The toughening agent may be methacrylate-terminated polybutadiene rubber, carboxyl-terminated copolymer of butadiene and acrylonitrile, carboxyl-terminated styrene butadiene rubber, carboxyl-terminated styrene butadiene styrene rubber, ethylene / propylene / diene terpolymer, (meth)acrylonitrile-butadiene copolymer, (meth)acrylonitrile-styrene copolymer, (meth)acrylonitrile-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, C １ -C ８ 10. The curable, electrochemically releasable one-component (1K) structural adhesive composition according to any of claims 1 to 9, wherein the curable, electrochemically releasable one-component (1K) structural adhesive composition is selected from the group consisting of A-B-A triblock copolymers having blocks A and B consisting of alkyl (meth)acrylates, triblock copolymers based on methyl (meth)acrylate (MMA), n-butyl acrylate (nBA) and 2-ethylhexyl acrylate (2-EHA), and mixtures thereof.

11. 11. The curable electrochemically releasable one-component (1K) structural adhesive composition of claim 10, wherein the toughening agent is present at 3-35%, preferably 6-26%, more preferably 11-23%, based on the total weight of the composition.

12. A cured product of the electrochemically releasable one-component (1K) structural adhesive composition of any of claims 1-11.

13. Use of the electrochemically releasable one-component (1K) structural adhesive composition according to any one of claims 1 to 11, or the cured product according to claim 12, in an electronic device.

14. a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface; 13. A bonded structure comprising the electrochemically releasable one-component (1K) structural adhesive composition of any of claims 1 to 11, or the cured product of claim 12, deposited between electrically conductive surfaces of first and second substrates.

15. 1) applying a voltage across both surfaces to form an anodic interface and a cathodic interface, preferably between 5 and 70 V for 1 to 60 minutes; and 2) peeling the surface; 15. The method of claim 14, comprising:

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