Curable and electrically debondable one-component (1K) structural adhesive composition

Abstract

The present invention relates to a curable and electrochemically debondable one-component (1K) structural adhesive composition comprising: 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) a compound selected from the group consisting of 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, and 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide; the preparation method comprises the following steps of: adding 1-(trifluoromethylsulfonyl) imide, 1-nonyl-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-chloro-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-chloro-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-chloro-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-chloro-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-chloro-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1- an electrolyte comprising a 1-hexadecyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, a 1-octadecyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, a trihexyltetradecyl phosphonium 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 high humidity) while maintaining adhesion and deadhesion properties.

Description

Technical Field

[0001] The present invention relates to curable and electrically debondable one-component (1K) structural adhesive compositions which, after curing, are capable of bonding substrates together and carrying loads in the bonded composite structure, but can also be electrochemically debonded from the particular substrate to which it is applied. Background Art

[0002] Adhesive bonding and polymer coatings are commonly used in the assembly and finishing of manufactured products. They are used to replace mechanical fasteners such as screws, bolts, and rivets to provide bonding with reduced machining costs and greater flexibility in the manufacturing process. Adhesive bonding evens out stresses, reduces the potential for fatigue, and seals joints from corrosive substances.

[0003] While adhesive bonding offers many advantages over mechanical fasteners, certain disadvantages must be acknowledged. First, adhesive bonded articles are often difficult to disassemble where practical applications require disassembly of the adhesive bonded article. Second, when the adhesive cures in situ to bond two substrates together, a cross-linked chemical network is formed: after disassembly of the adhesive bonded article, that chemical network cannot, in most cases, be reused as an adhesive. These disadvantages are particularly prominent in industries where it is advantageous to recycle, reuse or re-purpose manufactured products, which are often resource-intensive.

[0004] As for the first identified disadvantage, adhesive removal by mechanical methods (such as by sandblasting or by wire brushing) is generally excluded, in part because the adhesive is placed between the substrates and is therefore difficult to access or to abrade without damaging the substrate surfaces. Removal by application of chemicals and / or high temperatures may be effective but can be time-consuming and complicated to perform, particularly if one wishes to retain the substrate surfaces with the residual adhesive from which they were removed: the aggressive chemicals and / or harsh conditions required generally remove substantially all of the adhesive and damage the separated substrates, rendering them unsuitable for subsequent applications.

[0005] As an illustrative example, it is clearly desirable to remove, replace, and / or recycle components in electronic devices (e.g., laptops and cell phones) that are attached internally to the device using adhesives. However, such adhesives are typically high strength because they are designed to maintain adhesion during drops or impact events and over a wide range of operating temperatures and other environmental conditions. Therefore, if care is not taken, adhesive-bonded device components can be damaged or destroyed when the components are removed by machining, application of chemicals, or high temperatures.

[0006] With these problems in mind, some authors have attempted to develop debondable adhesive compositions in which an electrical current is passed through the cured composition to disrupt the bond at the interface of the adhesive with the substrate.

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

[0008] US2007 / 0269659 describes an adhesive composition that is debondable at two interfaces, which composition: (i) comprises a polymer and an electrolyte; (ii) promotes bonding of the two surfaces; and (iii) responds to a voltage applied to the two surfaces to form an anode interface and a cathode interface, thereby debonding from both the anode surface and the cathode surface.

[0009] US2008 / 0196828 describes a hot melt adhesive composition comprising: a thermoplastic component; and an electrolyte, wherein the electrolyte provides the composition with sufficient ionic conductivity to enable a Faradaic reaction at a bond formed between the composition and a conductive surface and to enable the composition to be debonded 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 one or more non-conductive substrates with a conductive ink; b) applying an electrically debondable hot melt adhesive composition to the surface of the first substrate and / or the second substrate coated with the conductive ink; c) contacting the first substrate with the second substrate so that the electrically debondable hot melt adhesive composition is placed between the two substrates; d) forming an adhesive bond between the two substrates to provide a bonded substrate; and e) applying a voltage to the bonded substrates, whereby the adhesion force at at least one interface between the electrically debondable hot melt adhesive composition and the substrate surface is significantly weakened.

[0011] WO2021 / 115771A1 relates to a curable one-component (1K) debondable 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 of: e) a combination of a solubilizer and a toughening agent; and f) conductive particles.

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

[0013] Despite the favorable development of electrochemically debondable adhesive compositions, the solvated salts or electrolytes present in electrochemically debondable adhesives are inherently hygroscopic. Therefore, moisture can accumulate to saturation levels within hours or days and affect the long-term stability and performance of the adhesive. Therefore, there is a need for an electrochemically debondable structural adhesive that can withstand harsh conditions (high temperature and humidity) while maintaining bonding and debonding properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A bonded structure according to the present invention is illustrated.

[0015] Figure 2 Initial debonding of a structure when an electric current is passed through the structure is illustrated. Summary of the invention

[0016] The present invention relates to a curable and electrochemically debondable one-component (1K) structural adhesive composition, which comprises: a) a (meth)acrylate monomer selected from hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate and a mixture thereof; b) a (meth)acrylate monomer selected from 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; The invention relates to an electrolyte comprising: 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-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 a mixture thereof; c) a copolymerizable acid; d) an initiator; e) a core-shell toughening agent; and f) a toughening agent.

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

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

[0019] The present invention encompasses a bonded structure comprising: a) a first substrate having a conductive surface; and b) a second substrate having a conductive surface; wherein the electrochemically debondable one-component (1K) structural adhesive composition or cured product according to the present invention is placed between the conductive surfaces of the first and second substrates.

[0020] The present invention also encompasses a method for debonding a bonded structure according to the present invention, comprising the steps of: 1) applying a voltage to two surfaces to form an anodic interface and a cathodic interface, preferably applying a voltage of 5 to 70 V for 1 to 60 minutes; and 2) debonding the surfaces. DETAILED DESCRIPTION

[0021] In the following paragraphs, the present invention is described in more detail. Unless explicitly stated otherwise, each aspect described in this way can be combined with any one or more other aspects. In particular, any feature that is indicated as being preferred or advantageous can be combined with any one or more other features that are indicated as being preferred or advantageous.

[0022] In the context of the present invention, the terms used are to be interpreted according to the following definitions, unless the context indicates otherwise.

[0023] As used herein, the singular forms "a," "an," "the," and "said" include singular and plural referents unless the context clearly dictates otherwise.

[0024] As used herein, the terms "comprising" and "including" are synonymous with "containing" or "comprising" and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps. If used, the phrase "consisting of is closed-ended and excludes all additional elements. Furthermore, the phrase "consisting essentially of excludes additional essential elements, but allows for the inclusion of insubstantial elements that do not substantially change the nature of the invention.

[0025] Recitations of numerical endpoints include all numbers and decimals subsumed within the corresponding ranges, as well as the recited endpoints.

[0026] All percentages, parts, ratios, etc. mentioned herein are based on weight unless otherwise specified.

[0027] 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, it should be understood that any range obtained by combining any upper limit or preferred upper value with any lower limit or preferred lower value is specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0028] The terms "preferred," "preferably," "desirably," "particularly," "especially," and their synonyms are often used herein to refer to disclosed embodiments that may provide particular advantages under certain circumstances. However, the listing of one or more preferred, preferred, desirable, or particular embodiments does not mean that other embodiments are not useful, nor is it intended to exclude those other embodiments from the scope of the present disclosure.

[0029] As used throughout this application, the words "may" or "may" are used in a permissive sense (ie, meaning having the possibility), rather than in a mandatory sense.

[0030] As used herein, the term "one-component (1K) composition" refers to a composition in which the components of the composition are mixed together during storage of the composition, but the properties of the composition (including viscosity) remain sufficiently consistent during the storage time to facilitate successful subsequent use of the composition.

[0031] A "two-component (2K) composition" is understood to be a composition in which the first component / part and the second component / part must be stored in separate containers because they are (highly) reactive together. The two components / parts are mixed only shortly before application and then react, usually without additional activation, with the formation of bonds and thus of the polymer network. Here, higher temperatures can be applied to accelerate the crosslinking reaction.

[0032] As used herein, the term "electrochemically debondable" means that after curing of the adhesive, the bond strength is reduced by at least 50% when a potential of 5V to 70V is applied for a duration of 1 to 60 minutes. The cured adhesive is applied between two substrates bonded by the adhesive so that an electric current flows through the adhesive bond line. The bond strength is measured by a tensile lap shear (TLS) test performed at room temperature and based on EN 1465:2009 (German version) based on adhesives-Determination of tensile lap-shear strength of bonded assemblies.

[0033] As used herein, the term "clean debonding" refers to a curable and electrochemically debondable one-component (1K) structural adhesive composition that is only on the first substrate or the second substrate after debonding, which means that one of the substrates is substantially free of adhesive. The term "substantially free of adhesive" herein means that 5% or less of adhesive remains in the substrate after debonding, preferably less than 3% and more preferably less than 1% of adhesive remains, wherein the inspection / assessment is performed visually.

[0034] As used herein, the term "monomer" refers to a substance that can undergo polymerization to contribute structural units to the chemical structure of a polymer. The term "monofunctional" as used herein refers to having one polymerizable moiety. The term "multifunctional" as used herein refers to having more than one polymerizable moiety.

[0035] As used herein, "(meth)acryl" is a shorthand term referring to "acryl" and / or "methacryl." Thus, the term "(meth)acrylamide" refers collectively to acrylamide and methacrylamide.

[0036] As used herein, "structural adhesive" refers to an adhesive that bonds components together in a load-bearing structure. In other words, a structural adhesive can hold two or more substrates together under stress.

[0037] As used herein, "stable under harsh conditions" means that after curing of the adhesive, the bond strength decreases by no more than 50% after storage in a 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.

[0038] As used herein, "core-shell toughener" refers to a rubber particle core formed of a polymer containing an elastomer or rubbery polymer as a main component and a shell layer formed of a polymer graft polymerized onto the core. During the graft polymerization process, the shell layer partially or completely covers the surface of the rubber particle core.

[0039] The entire contents of all references cited in this specification are incorporated herein by reference.

[0040] Unless otherwise defined, all terms (including technical and scientific terms) used in disclosing the present invention have the meaning commonly understood by one of ordinary skill in the art to which the present invention belongs. By way of further guidance, term definitions are included to better understand the teachings of the present invention.

[0041] The present invention relates to a curable and electrochemically debondable one-component (1K) structural adhesive composition, which comprises: a) a (meth)acrylate monomer selected from hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate and a mixture thereof; b) a (meth)acrylate monomer selected from 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; The invention relates to an electrolyte comprising: 1-nonyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-nonyl-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 a mixture thereof; c) a copolymerizable acid; d) an initiator; e) a core-shell toughening agent; and f) a toughening agent.

[0042] The curable and electrochemically debondable one-component (1K) adhesive composition according to the invention is a structural adhesive.

[0043] The composition according to the present invention provides good initial bond strength and is effectively debondable while having high aging stability, in other words, stable under high temperature, high humidity conditions. The use of compatible electrolytes in the hydrophobic adhesive matrix does not affect the stability of the final adhesive formulation (avoiding the migration and phase separation of ionic species). The applicant has found that the combination of the adhesive matrix, electrolyte and a mixture of a core-shell toughener and a toughener provides high stability under harsh storage conditions. In order to simulate the conditions that electrical equipment is usually subjected to in a high temperature and high humidity environment, an accelerated aging study of up to 3 weeks was carried out in a climate chamber at 65°C and 90% relative humidity.

[0044] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention comprises a (meth)acrylate monomer.

[0045] (Meth) acrylate monomer forms adhesive polymer. Adhesive polymer forms linear or crosslinked network, which provides high strength and solvent resistivity (solvent resistivity). Adhesive polymer should support electrochemical reaction at the interface with conductive substrate. Therefore, it is necessary to have enough ion mobility by polymer matrix. In a specific embodiment, adhesive matrix should include functional groups that can coordinate ions from electrolyte, such as alkoxy and / or oligoether groups.

[0046] Examples of (meth)acrylate monomers suitable for use in the present invention are 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, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, The invention also includes the following: 1, 2-(meth)acrylate, 4-(meth)acrylate, 5-(meth)acrylate, 6-(meth)acrylate, 8-(meth)acrylate, 1, 2-(meth)acrylate ...

[0047] 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.

[0048] These monomers are preferred because they provide good bonding strength with good cohesive strength on metal and glass substrates.

[0049] 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.

[0050] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the (meth)acrylate monomer present in an amount of 20 to 55%, preferably 23 to 52%, and more preferably 26 to 50%, based on the total weight of the composition.

[0051] These (meth)acrylate monomer amounts are preferred because they provide desirable viscosity, adhesion and mechanical properties. If the amount is greater than 55% or less than 20%, this may negatively affect viscosity, adhesion and mechanical properties.

[0052] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention comprises an electrolyte.

[0053] Suitable electrolytes exhibit good compatibility with the above-mentioned polymer matrix. In addition, it is preferred that the electrolyte is uniformly distributed in the polymer matrix. Good distribution helps to achieve better stability for harsh storage conditions. In addition, it is preferred that the electrolyte provides sufficient ionic conductivity to support the electrochemical reaction at the interface with the conductive substrate.

[0054] The electrolyte comprises or consists of at least one salt according to formula (I) or formula (II):

[0055]

[0056] Where: R 1 , R 2 , R 3 , R 4 and R 5 independently selected from 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;

[0057] R q is a C1-C6 alkyl group; and

[0058] X - as counter anion.

[0059] The electrolyte is selected from 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 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.

[0060] The electrolytes listed above are preferred and used because they have hydrophobic properties, which improves the stability of the composition under harsh conditions. In addition, these electrolytes contain alkyl chains, which promote compatibility with the polymer matrix.

[0061] 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.

[0062] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the electrolyte present in an amount of 6 to 25%, preferably 7 to 23%, and more preferably 10 to 20%, based on the total weight of the composition.

[0063] These electrolyte amounts are preferred because an amount greater than 25% may result in good debonding effect, however curing may not be complete and thus may adversely affect initial adhesive properties, while a small amount (mainly less than 6%) may result in lack of debonding effect.

[0064] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention comprises a copolymerizable acid.

[0065] Preferably, the copolymerizable acid is selected from acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate phosphate, hydroxypropyl (meth)acrylate phosphate, and mixtures thereof.

[0066] The copolymerizable acids mentioned above are preferred because they are believed to improve the adhesive properties of the composition.

[0067] Commercially available copolymerizable acids suitable for use in the present invention include, but are not limited to, methacrylic acid from Sigma Aldrich, 2-hydroxyethyl (meth)acrylate phosphate from Sartomer.

[0068] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the copolymerizable acid present in an amount of 5 to 20%, preferably 7 to 18%, and more preferably 9 to 16%, based on the total weight of the composition.

[0069] These copolymerizable acid amounts are preferred because amounts greater than 20% may cause corrosion problems, whereas lower amounts may result in incomplete curing, thereby reducing initial adhesive properties.

[0070] The acrylic polymer is formed by free radical polymerization, and therefore the curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention includes an initiator.

[0071] Initiators suitable for use in the present invention are peroxides. Although certain peroxides (e.g., dialkyl and diaryl peroxides) are useful initiators, hydroperoxides also represent an important class of initiators for the present invention. In this context, although hydrogen peroxide itself can be used, it is preferred to use organic hydroperoxides. Without intending to limit the present invention, representative hydroperoxide compounds have the general formula:

[0072] R p OOH

[0073] Where: R p is a hydrocarbon group containing not more than 18 carbon atoms, and

[0074] Preferred among them: R p C1-C 12 Alkyl, C6-C 18 Aryl or C7-C 18 Aralkyl.

[0075] Preferably, the initiator is selected from 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.

[0076] The above-mentioned initiators are preferred because they perform well in the overall composition.

[0077] Commercially available initiators suitable for use in the present invention include, but are not limited to, benzoyl peroxide available from PanReac AppliChem.

[0078] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have an initiator present in an amount of 0.1 to 7%, preferably 0.5 to 6%, and more preferably 1 to 5%, based on the total weight of the composition.

[0079] These initiator amounts are preferred because amounts greater than 7% may result in an excess of initiator and unwanted reactions may adversely affect the properties of the adhesive composition, whereas small amounts (mainly less than 0.1%) may result in incomplete curing and, therefore, poor initial adhesion and mechanical properties.

[0080] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention comprises a core-shell toughening agent.

[0081] Applicants have discovered that by combining defined (meth)acrylate monomers and defined electrolytes with core-shell toughening agents, the stability of adhesive compositions under harsh conditions can be improved.

[0082] The core-shell toughening agent suitable for use in the present invention includes a single core-shell toughening agent, or a mixture of two or more core-shell toughening agents; preferably, the core-shell toughening agent has: a shell comprising a polymer or copolymer formed by one or more monomers selected from methyl methacrylate, styrene, acrylonitrile, acrylic acid, (meth)acrylamide and mixtures thereof; and a core comprising a homopolymer or copolymer selected from butadiene homopolymer, isoprene homopolymer, copolymer of butadiene and vinyl aromatic monomer, (meth)acrylonitrile or (meth)acrylate, copolymer of isoprene and vinyl aromatic monomer, (meth)acrylonitrile or (meth)acrylate, polybutylacrylate, polydimethylsiloxane, cross-linked polydimethylsiloxane and mixtures thereof.

[0083] The core-shell toughening agents mentioned above are preferred because they provide improved properties.

[0084] Commercially available core-shell toughening agents suitable for use in the present invention include, but are not limited to: Paraloid EXL 2650A, EXL 2655 and EXL2691 A from The Dow Chemical Company; XT100, and Kane from Kaneka Corporation MX series.

[0085] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the core-shell toughening agent present in an amount of 2 to 15%, preferably 3 to 11%, and more preferably 3 to 10%, based on the total weight of the composition.

[0086] If the amount of the core-shell toughening agent is greater than 15%, this may result in too high a viscosity and may affect the mechanical properties of the composition; while an amount less than 2% may adversely affect aging resistance.

[0087] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention comprises a toughening agent. Note that in this context, a toughening agent is different from a core-shell toughening agent.

[0088] Furthermore, the applicant has discovered that by combining defined (meth)acrylate monomers and defined electrolytes with toughening agents, the stability of the adhesive composition under harsh conditions can be improved.

[0089] Tougheners suitable for use in the present invention may be reactive tougheners or non-reactive tougheners or mixtures thereof.

[0090] Suitable non-reactive toughening agents may be selected from methacrylate terminated polybutadiene rubber, carboxyl terminated butadiene-acrylonitrile copolymer, carboxyl terminated styrene-butadiene rubber, carboxyl terminated styrene-butadiene-styrene rubber, and mixtures thereof.

[0091] Suitable reactive toughening agents can be selected from: 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 having blocks A and B respectively composed of C1-C8 alkyl (meth)acrylates having different glass transition temperatures (Tg), such as copolymers of polymethyl methacrylate and polyn-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.

[0092] The reactive toughening agents mentioned above are preferred because they provide good overall performance without adversely affecting other properties.

[0093] Commercially available reactive toughening agents suitable for use in the present invention include, but are not limited to, HYPRO 2000X168LC VTB from Huntsman.

[0094] Commercially available non-reactive toughening agents suitable for use in the present invention include, but are not limited to, Blendex 338 from Galata Chemicals, Kurarity LA 4285 from Kuraray, and Nipol 1472X from Zeon Chemicals.

[0095] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have a toughening agent present in an amount of 3 to 35%, preferably 6 to 26%, and more preferably 11 to 23%, based on the total weight of the composition.

[0096] If the amount of the reactive toughening agent is greater than 35%, this may result in excessively high viscosity and may impair the mechanical properties of the composition; whereas an amount less than 3% may adversely affect aging resistance.

[0097] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may further comprise a urethane (meth)acrylate oligomer. The urethane (meth)acrylate oligomer improves the mechanical properties of the composition.

[0098] 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.

[0099] Urethane (meth) acrylate oligomers can be prepared by the reaction of a multifunctional (meth) acrylate with a hydroxyl group and a polyisocyanate. The multifunctional isocyanate may include methylene dicyclohexyl isocyanate or 1,6-hexamethylene diisocyanate. Hydroxyl functionalized acrylates may include: hydroxyalkyl acrylates, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate; or polyethylene glycol acrylate. In one embodiment, the multifunctional urethane acrylate oligomer may include a reaction product of a polyester polyol, methylene dicyclohexyl isocyanate, and hydroxyethyl acrylate.

[0100] Commercially available urethane (meth)acrylate oligomers suitable for use in the present invention include, but are not limited to: aliphatic urethane acrylates CN-9002, CN9014 NS, CN-980, CN-981, CN-9019, CN1993CG from Sartomer Company Inc; and aromatic urethane triacrylate CN970A60 from Sartomer.

[0101] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the urethane (meth)acrylate oligomer present in an amount of 15 to 30%, preferably 18 to 28%, and more preferably 20 to 26%, based on the total weight of the composition.

[0102] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may further comprise a filler. The presence of the filler in the composition can be used to adjust the viscosity of the composition and reduce the thermal expansion coefficient of the adhesive.

[0103] There is no particular intention to limit the shape of the particles used as fillers: needle-shaped, spherical, ellipsoidal, cylindrical, beaded, cubic or platelet-shaped particles can be used alone or in combination. In addition, it is envisaged that agglomerates of more than one particle type can be used. Likewise, there is no particular intention to limit the size of the particles used as fillers. However, such fillers typically have an average volume particle size measured by laser diffraction / scattering methods of 0.01 to 1500 μm, such as 0.1 to 1000 μm or 0.1 to 500 μm.

[0104] Exemplary fillers include, but are not limited to, barium sulfate, calcium carbonate, calcium oxide, calcium metasilicate, silicon dioxide, fumed silica, sand, quartz, zeolite, bentonite, magnesium carbonate, diatomaceous earth, alumina, clay, talc, flint, mica, glass powder, zinc oxide, and other ground mineral substances. Short fibers, such as glass fibers, glass filaments, polyacrylonitrile, carbon fibers, and polyethylene fibers may also be added.

[0105] Preferably, the filler is selected from the group consisting of calcium carbonate, calcium oxide, calcium metasilicate, zinc oxide, talc, fumed silica, silicon dioxide, barium sulfate and mixtures thereof.

[0106] The use of precipitated and / or fumed (pyrogenic) silica as rheology control agent in the compositions of the invention is particularly preferred: such precipitated or pyrogenic silica should advantageously have a viscosity of 25 to 500 m 2 / g, preferably 100 to 250m 2 / g of BET surface area measured by nitrogen adsorption in accordance with DIN 66131.

[0107] Commercially available fillers suitable for use in the present invention include, but are not limited to, Aerosil 200 available from Evonik Industries and ZnO from Sigma Aldrich.

[0108] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have a filler present in an amount of 0.01 to 10%, preferably 0.05 to 7%, and more preferably 0.1 to 6%, based on the total weight of the composition.

[0109] These ranges are preferred because they will provide the composition with the desired viscosity. If the filler level is too high, the viscosity may be too high, while too low an amount may result in a viscosity that is too low.

[0110] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may further comprise a linear block copolymer.

[0111] A linear block copolymer suitable for use in the present invention may be based on styrene and butadiene having 40 mass % bound styrene.

[0112] Commercially available linear block copolymers suitable for use in the present invention include, but are not limited to, Kraton D1155 from Kraton Corporation.

[0113] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the linear block copolymer present in an amount of 0.1 to 10%, preferably 1 to 8%, and more preferably 2 to 6%, based on the total weight of the composition.

[0114] The composition according to the invention may further comprise a conductive filler. There is no particular intention to limit the shape of the particles used as conductive fillers: needle-shaped, spherical, ellipsoidal, cylindrical, beaded, cubic or plate-shaped particles may be used alone or in combination. In addition, it is envisaged that agglomerates of more than one particle type may be used. Likewise, there is no particular intention to limit the size of the particles used as conductive fillers. However, such conductive fillers typically have an average volume particle size measured by a laser diffraction / scattering method of 1 to 500 μm, for example 1 to 200 μm.

[0115] Exemplary conductive fillers include, but are not limited to, silver, copper, gold, palladium, platinum, nickel, nickel coated with gold or silver, carbon black, carbon fibers, 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 fibers, silver-coated spheres, antimony-doped tin oxide, conductive nanospheres, nanosilver, nanoaluminum, nanocopper, nanonickel, carbon nanotubes, and mixtures thereof.

[0116] Preferably, the conductive filler is selected from the group consisting of: silver and carbon black and mixtures thereof.

[0117] The curable and electrochemically debondable one-component (1K) structural adhesive composition according to the present invention may have the conductive filler present in an amount of 0.01 to 10%, preferably 0.05 to 7%, and more preferably 0.1 to 6%, based on the total weight of the composition.

[0118] The curable and electrochemically debondable one-component (1K) structural adhesive compositions according to the present invention may further comprise adjuvants and additives that may impart improved properties to these compositions. For example, adjuvants and additives may impart one or more of the following: improved elastic properties, improved elastic recovery, longer enabled processing time, faster curing time and lower residual viscosity. Such adjuvants and additives include: solubilizers, plasticizers, stabilizers (including UV stabilizers), antioxidants, reactive diluents, desiccants, adhesion promoters, bactericides, flame retardants, pigments or color pastes; and / or optionally also non-reactive diluents to a small extent.

[0119] Such adjuvants and additives may be used in desired combinations and proportions, provided that they do not adversely affect the properties and essential characteristics of the composition. Although there may be exceptions in some cases, these adjuvants and additives should not total more than 20% by weight of the total composition, and preferably should not account for more than 10% by weight of the composition.

[0120] To form a curable and electrochemically debondable one-component (1K) structural adhesive composition, the ingredients described above are brought together and mixed. To form a one-component (1K) curable composition, the ingredients of the composition are brought together and uniformly mixed under conditions that inhibit or prevent the reactive components from reacting: this may include mixing conditions that limit or prevent exposure to moisture, heat or radiation or limit or prevent activation of latent catalysts of the components. Thus, the ingredients are mixed in predetermined amounts by a machine (e.g., a static or dynamic mixer) under anhydrous conditions without intentional heating or light radiation.

[0121] The present invention relates to a cured product of an electrochemically debondable one-component (1K) structural adhesive composition according to the present invention.

[0122] The curing of the application composition according to the invention generally takes place at a temperature in the range of 80° C. to 140° C., preferably 100° C. to 120° C. The curing time is 10 to 120 minutes, preferably 30 to 60 minutes. Suitable temperatures depend on the specific compounds present and the desired curing rate and can be determined in the individual case by the person skilled in the art, if necessary using simple preliminary tests.

[0123] The electrochemically debondable one-component (1K) structural adhesive composition or cured product according to the present invention can be used in electronic devices.

[0124] Non-limiting examples of electronic devices may be the mentioned handheld devices, laptop computers, white goods, automotive applications and aerospace applications.

[0125] The present invention also relates to a bonded structure comprising: a) a first substrate having a conductive surface; and b) a second substrate having a conductive surface; wherein the electrochemically debondable one-component (1K) structural adhesive composition or cured product is placed between the conductive surfaces of the first and second substrates.

[0126] The initial use of a one-component (1K) curable composition in the formation of a bonded structure will now be described. The composition described above is applied to one or more material layers and then cured in situ. Before applying the composition, it is generally advisable to pre-treat the relevant surface to remove foreign matter therefrom: this step (if applicable) can facilitate the subsequent bonding of the composition thereto. Such treatments are known in the art and can be carried out in a single-stage or multi-stage manner consisting of, for example, etching treatment with an acid suitable for the substrate and an optional oxidizing agent; ultrasonic treatment; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric pressure 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 (e.g., carbon tetrachloride or trichloroethylene or alcohols such as hexanol and isopropanol or hydrocarbons such as ethyl acetate); and water rinsing, preferably with deionized or demineralized water. In those cases where an aqueous alkaline degreasing bath is used, any degreasing agent remaining on the surface should desirably be removed by rinsing the substrate surface with deionized or demineralized water.

[0127] In some embodiments, the adhesion of the coating composition of the present invention to the preferably pretreated substrate can be promoted by applying a primer thereto. In fact, a primer composition may be required to ensure effective fixation and / or curing time of the adhesive composition on the inactive substrate.

[0128] The composition according to the invention is then applied to the preferably pretreated, optionally primed surface of the substrate by conventional application methods, such as: bead dispensing; brushing; roller coating; doctor blade application; and printing methods.

[0129] As described above, the present invention provides a bonded structure comprising: a first substrate having a conductive surface; and a second substrate having a conductive surface, wherein a cured electrochemically debondable one-component (1K) adhesive composition as defined above and in the appended claims is placed between the first substrate and the second substrate. To produce such a structure, the adhesive composition can be applied to at least one inner surface of the first substrate and / or the second substrate, and then the two layers are subsequently contacted, optionally under applied pressure, so that the electrically debondable adhesive composition is placed between the two substrates.

[0130] It is recommended to apply the composition to the surface at a wet film thickness of 10 to 500 μm.

[0131] The initial bonding and subsequent debonding of the composition of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 A bonded structure according to the present invention is illustrated. Figure 2 Initial debonding of a structure when an electric current is passed through the structure is illustrated.

[0132] As attached Figure 1 As shown in , a bonded structure is provided in which a cured adhesive layer (10) is placed between two conductive substrates (11). Each conductive substrate (11) layer is in electrical contact with a power source (13), which can be a battery or an AC-driven direct current (DC) source. The positive and negative poles of the power source (13) are shown in a fixed position, but those skilled in the art will of course recognize that the polarity of the system can be reversed.

[0133] The two conductive substrates (11) are shown in the form of layers, which may be composed, inter alia, of: a metal film; a metal sheet; a metal mesh or grid; placed metal particles; a resin material, which is made conductive by a conductive element disposed therein; or a conductive oxide layer. As exemplary conductive elements, silver filaments, single-walled carbon nanotubes and multi-walled carbon nanotubes may be mentioned. As exemplary conductive oxides, doped indium oxides, such as indium tin oxide (ITO); doped zinc oxide; antimony tin oxide; cadmium stannate; and zinc stannate may be mentioned. In addition to the choice of conductive material, a person skilled in the art will recognize that in the case where the conductive substrate (11) is in the form of a grid or mesh, which provides limited contact with the cured adhesive layer (10), the effectiveness of the debonding operation may be reduced.

[0134] The present invention also relates to a method for debonding a bonded structure, the method comprising the steps of: 1) applying a voltage to two surfaces to form an anodic interface and a cathodic interface, preferably applying a voltage of 5 to 70 V for 1 to 60 minutes; and 2) debonding the surfaces. Preferably, the applied voltage is 20 to 50 V for 10 to 300 minutes.

[0135] When a voltage is applied between each conductive substrate (11), current is supplied to the adhesive composition (10) placed therebetween. This initiates an electrochemical reaction at the interface of the substrate (11) and the adhesive composition, which is understood to be oxidative at the positively charged interface or anodic interface and reductive at the negatively charged interface or cathodic interface. This reaction is believed to weaken the adhesive bond between the substrates, thereby allowing the debondable composition to be easily removed from the substrates.

[0136] However, it should be noted that the composition of the adhesive layer (10) can be adjusted so that debonding occurs at the positive electrode interface or the negative electrode interface or from both simultaneously. For some embodiments, the voltage applied to the two surfaces to form the anode interface and the cathode interface will cause debonding to occur simultaneously at the anode and cathode adhesive / substrate interfaces. In alternative embodiments, reversed polarity can be used to debond both substrate / adhesive interfaces simultaneously.

[0137] Desirably, after debonding, the adhesive composition is disposed only on the first substrate or the second substrate, meaning that one of the substrates is substantially free of adhesive.

[0138] Example

[0139] Methyl methacrylate (MMA) from Sigma Aldrich

[0140] Methacrylic acid (MAA) from Sigma Aldrich

[0141] 2-Hydroxyethyl Methacrylate (HEMA) from Acros Organics

[0142] 2-Hydroxypropyl Methacrylate (HPMA) from Alfa Aesar

[0143] Isobornyl acrylate (IBOA) from Sartomer

[0144] Isobornyl methacrylate (IBOMA) from Sartomer

[0145] Difunctional aliphatic urethane methacrylate oligomer CN1993CG from Sartomer

[0146] 2-Hydroxyethyl Methacrylate Phosphate SR9054 from Sartomer

[0147] Core-shell toughener (methyl methacrylate-butadiene-styrene, MBS) Clearstrength XT from Arkema Inc.

[0148] ABS terpolymer-based toughener Blendex 338 from Galata Chemicals

[0149] Acrylonitrile butadiene rubber-based toughener Nipol 1472X from Zeon Chemicals

[0150] Reactive toughener HYPRO2000X168 LC from Huntsman based on methacrylate-terminated polybutadiene

[0151] Kurarity LA 4285, an acrylic block copolymer-based toughener from Kuraray

[0152] Kraton D1155, a linear block copolymer based on styrene and butadiene with 40% by mass of bound styrene from Kraton Corporation

[0153] Zinc Oxide ZnO from Sigma Aldrich

[0154] Hydrophilic fumed silica Aerosil 200 from Evonik Industries

[0155] Benzoyl Peroxide BPO from PanReac AppliChem

[0156] 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide BMIMNTf2 from Sigma Aldrich

[0157] Trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide Cyphos IL 109 from Solvay

[0158] 1-Dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide DDMIMNTf2 from Iolitec

[0159] Example 1

[0160] The compositions were prepared according to Table 1. The compositions according to compositions 1 to 3 all had a hydrophobic final matrix.

[0161] First, tougheners Blendex 338 and Nipol 1472X were dissolved overnight in the corresponding acrylic monomers. A stirring plate can be used to accelerate the dissolution process. 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 mixing all ingredients in a pot at 3000 rpm for 1 minute, 3 times in a row, and delaying for 5 minutes to cool the formulation.

[0162] Table 1

[0163]

[0164]

[0165] The application substrate for all formulations was aluminum (AA6016). The aluminum was cut into pieces with a size of 2.5 cm×10 cm and a thickness of 1.25 mm. Glass beads (diameter of 100 to 200 microns) 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 the determination of the tensile lap shear strength of adhesive-bonded assemblies.

[0166] The bonding overlap area of ​​each substrate is 2.5cm×1.0cm, and the bonding thickness is 0.1cm (40mil). The applied adhesive composition is cured in the overlapping area by applying a temperature of 80°C for 30 minutes and applying a temperature of 120°C for 30 minutes. Subsequently, they are stored at room temperature for 24 hours before the initial tensile test or the bonded structure is stored in a climate chamber for accelerated aging research at 65°C and 90% relative humidity. After the 24-hour storage period, before and after applying a constant potential of 50V to the adhesive layer for a duration of up to 30 minutes, and after storage in a climate chamber at 65°C and 90% relative humidity, the tensile lap shear strength values ​​are measured respectively. The results are recorded in Table 2 below in this article.

[0167] Table 2

[0168]

[0169] Compositions 1 to 3 all exhibited good properties. In particular, compositions 2 and 3 exhibited excellent stability and delamination properties even after storage at 65° C. and 90% relative humidity for 1 week.

[0170] Example 2

[0171] Compositions were prepared according to Table 3. Additional impact modifiers and tackifiers were included in compositions 4 and 5. In addition, the acidic acrylic phosphate SR9054 was exchanged with methacrylic acid. Mixtures of MMA and HPMA were tested, again in an effort to obtain a hydrophobic final matrix. Tougheners Blendex 338, Clearstrength XT 100, and Nipol 1472X were first dissolved in HPMA, while Kurarity LA 4285 and Kraton D1155 were dissolved separately in MMA. A stirring plate can be used to accelerate the dissolution process. After dissolution, the two mixtures were added to a pot, all other ingredients were added, and DDMIM NTf2 was used as a reference electrolyte, which showed good hydrophobic properties based on compositions 1 to 3. The final mixture was obtained by mixing all ingredients in a pot at 3000 rpm for 1 minute, 3 times in a row, and delaying for 5 minutes to cool the formulation down.

[0172] Table 3

[0173]

[0174] The application substrate for all formulations was aluminum (AA6016). The aluminum was cut into pieces with a size of 2.5 cm×10 cm and a thickness of 1.25 mm. Glass beads (diameter of 100 to 200 microns) 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 the determination of the tensile lap shear strength of adhesive-bonded assemblies.

[0175] The bonding overlap area of ​​each substrate is 2.5cm×1.0cm, and the bonding thickness is 0.1cm (40mil). The applied adhesive composition is cured in the overlapping area by applying a temperature of 80°C for 30 minutes and applying a temperature of 120°C for 30 minutes. Subsequently, they are stored at room temperature for 24 hours before the initial tensile test or before the bonded structure is stored in a climate chamber for accelerated aging research at 65°C and 90% relative humidity. After the 24-hour storage period, before and after applying a constant potential of 50V to the adhesive layer for a duration of up to 30 minutes, and after storage in a climate chamber at 65°C and 90% relative humidity, the tensile lap shear strength values ​​are measured respectively. The results are recorded in Table 4 below in this article.

[0176] Table 4

[0177]

[0178] Both formulations of Compositions 4 and 5 were very stable. The use of MAA in Composition 4 showed slightly lower initial strength compared to Composition 5, however it remained more stable after storage at 65°C and 90% relative humidity for up to 3 weeks. The electrochemical delamination performance was excellent in both compositions.

[0179] Example 3

[0180] The compositions were prepared according to Table 5. All ingredients were added together and speed mixed at 3000 rpm for 1 minute, 3 times with a delay of 5 minutes to allow the formulation to cool down.

[0181] Table 5

[0182]

[0183] The application substrate for all formulations was aluminum (AA6016). The aluminum was cut into pieces with a size of 2.5 cm×10 cm and a thickness of 1.25 mm. Glass beads (diameter of 100 to 200 microns) 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 the determination of the tensile lap shear strength of adhesive-bonded assemblies.

[0184] The bond overlap area of ​​each substrate was 2.5 cm x 1.0 cm and the bond thickness was 0.1 cm (40 mil). The applied adhesive composition was cured in the overlap area by applying a temperature of 80° C. for 30 minutes and a temperature of 120° C. for 30 minutes. Subsequently, they were stored at room temperature for 24 hours before the initial tensile test or the bonded structures were stored in a climate chamber for accelerated aging studies at 65° C. and 90% relative humidity. The tensile lap shear strength values ​​are recorded in Table 6 below herein.

[0185] Table 6

[0186]

[0187] Composition 6, which does not contain a core-shell toughener and a toughening agent, does not show good stability after storage at 65° C. and 90% relative humidity for 1 day.

Claims

1. A curable and electrochemically debondable one-component (1K) structural adhesive composition comprising: a) a (meth)acrylate monomer selected from hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methyl methacrylate and mixtures thereof; b) is selected from 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- Electrolytes of 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) copolymerizable acids; d) initiator; e) a core-shell toughening agent; and f) Toughening agent.

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

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

4. The curable and electrochemically debondable one-component (1K) structural adhesive composition according to any one of claims 1 to 3, wherein the copolymerizable acid is selected from acrylic acid, methacrylic acid, 2-hydroxyethyl (meth)acrylate phosphate, hydroxypropyl (meth)acrylate phosphate, and mixtures thereof.

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

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

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

8. A curable and electrochemically debondable one-component (1K) structural adhesive composition according to any one 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, the core-shell toughening agent has: a shell comprising a polymer or copolymer formed from one or more monomers selected from methyl methacrylate, styrene, acrylonitrile, acrylic acid, (meth)acrylamide and mixtures thereof; and a core comprising a homopolymer or copolymer selected from butadiene homopolymers, isoprene homopolymers, copolymers of butadiene and vinyl aromatic monomers, (meth)acrylonitrile or (meth)acrylates, copolymers of isoprene and vinyl aromatic monomers, (meth)acrylonitrile or (meth)acrylates, polybutylacrylate, polydimethylsiloxane, cross-linked polydimethylsiloxane and mixtures thereof.

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

10. A curable and electrochemically debondable one-component (1K) structural adhesive composition according to any one of claims 1 to 9, wherein the toughening agent is selected from: methacrylate terminated polybutadiene rubber, carboxyl terminated butadiene-acrylonitrile copolymer, 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, ABA triblock copolymer having blocks A and B consisting of C1-C8 alkyl (meth)acrylate, triblock copolymers based on methyl (meth)acrylate (MMA), n-butyl acrylate (nBA) and 2-ethylhexyl acrylate (2-EHA), and mixtures thereof.

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

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

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

14. A bonded structure comprising: a) a first substrate having a conductive surface; as well as b) a second substrate having a conductive surface; The electrochemically debondable one-component (1K) structural adhesive composition according to any one of claims 1 to 11 or the cured product according to claim 12 is placed between the conductive surfaces of the first and second substrates.

15. A method of debonding a bonded structure according to claim 14, the method comprising the steps of: 1) applying a voltage on both surfaces to form an anode interface and a cathode interface, preferably applying a voltage of 5 to 70 V for 1 to 60 minutes; as well as 2) Debonding the surface.

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