Two component (2K) curable adhesive composition

Abstract

This invention relates to a curable and electrochemically detachable two-component (2K) adhesive composition comprising: a first component comprising: i) at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols; ii) other active hydrogen compounds, if applicable; and iii) a non-polymerizable electrolyte; and a second component comprising at least one polyisocyanate, wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is at least 1:1.

Description

[Technical Field]

[0001] This invention relates to adhesive compositions that are detachable from a particular substrate to which they are applied. More specifically, this invention relates to two-component (2K) curable and electrochemically detachable polyurethane adhesive compositions. [Previous Technology]

[0002] Adhesive bonding and polymer coatings are commonly used in the assembly and post-processing of finished products. They are used to replace mechanical fasteners such as screws, bolts, and rivets to provide a bond with reduced processing costs and greater adaptability in the manufacturing process. Adhesive bonding distributes stress evenly, reduces the possibility of fatigue, and seals joints against corrosive species.

[0003] Although adhesive bonding offers many advantages over mechanical fasteners, it is often difficult to separate adhesively bonded objects when required in practical applications. Removal of the adhesive by mechanical methods (e.g., sandblasting or wire brushing) is generally discouraged, partly because the adhesive is located between substrates and is therefore inaccessible or difficult to abrade without damaging the substrate surfaces. Separation by applying chemicals and / or high temperatures (e.g., as disclosed in U.S. Patent No. 4,171,240 (Wong) and U.S. Patent No. 4,729,797 (Linde et al.)) can be effective, but it can be time-consuming and complex; furthermore, corrosive chemicals and / or the required harsh conditions can damage the separated substrates, rendering them unsuitable for subsequent applications.

[0004] Noticing these problems, some authors have attempted to develop electrochemically detachable adhesive compositions in which an electric current passing through the curing composition disrupts the bond between the adhesive and the substrate interface.

[0005] U.S. Patent No. 7,465,492 (Gilbert) describes an electrochemically degummable composition comprising: a matrix functional comprising a monomer selected from the group consisting of acrylic acid, methacrylic acid, and combinations thereof; a free radical initiator; and an electrolyte, wherein the electrolyte provides the composition with sufficient ionic conductivity to support a faradaic reaction at the junction formed between the composition and a conductive surface, thereby degumming the composition on the surface.

[0006] US 2007 / 0269659 (Gilbert) describes an adhesive composition that is desorbable at two interfaces, the composition: (i) comprises a polymer and an electrolyte; (ii) promotes the bonding of two surfaces; and, (iii) desorbs from both the anode and cathode surfaces in response to a voltage applied to the two surfaces to form an anode interface and a cathode interface.

[0007] WO2007 / 142600 (Stora Enso AB) describes an electrochemically degrading adhesive composition that provides adhesive bonding and sufficient ionic conductivity to a conductive surface to degrade adhesive bonding when a voltage is applied to the adhesive composition, wherein the composition contains at least one effective amount of an ionic compound to provide the ionic conductivity and wherein the ionic compound has a melting point not exceeding 120°C.

[0008] EP 3363875 A (Nitto Denko Corporation) provides an electrically peelable adhesive composition that forms an adhesive layer having high adhesion and being easily peelable when a voltage is applied for a short period of time. The electrically peelable adhesive composition of the present invention comprises a polymer and 0.5 to 30 wt.% of an ionic liquid based on the weight of the polymer, wherein the anion of the ionic liquid is a bis(fluorosulfonyl)imidine anion.

[0009] WO2017 / 133864 (Henkel AG & Co. KGaA) describes a method for reversibly bonding first and second substrates, wherein at least the first substrate is a non-conductive substrate, the method comprising: a) coating the surface of the non-conductive substrate with conductive ink; b) applying an electrically detachable hot melt adhesive composition to the conductive ink-coated surface of the first substrate and / or the second substrate; c) bringing the first and second substrates into contact such that the electrically detachable hot melt adhesive composition is inserted 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 substrate, thereby substantially reducing the adhesive force at the interface between the electrically detachable hot melt adhesive composition and the substrate surface.

[0010] WO2013 / 135677 (Henkel AG & Co. KGaA) describes a hot melt adhesive containing: 20 to 90 wt% of at least one polyamide having a molecular weight (Mw) of 10,000 to 250,000 g / mol; 1 to 25 wt% of at least one organic or inorganic salt; and 0 to 60 wt% of other additives, wherein the adhesive has a softening point of 100°C to 220°C.

[0011] US 2008 / 0196828 (Gilbert) describes a hot melt adhesive composition comprising: a thermoplastic component; and an electrolyte, wherein the electrolyte provides sufficient ionic conductivity to enable a Faraday reaction to occur at the interface formed between the composition and a conductive surface and to desorb the composition from the surface.

[0012] WO2016 / 135341 (Henkel AG & Co. KGaA) describes a reactive hot melt adhesive composition that at least partially loses its adhesiveness upon application of voltage, thereby allowing the detachment of a substrate bonded with the adhesive. More specifically, the reactive hot melt adhesive composition comprises: a) at least one isocyanate-functionalized polyurethane polymer; and b) at least one organic or inorganic salt.

[0013] It is known in this art that the use of polyurethane in structural adhesives offers many advantages. Specifically, the durability, hardness, and modulus of polyurethane can be easily tuned for specific applications. Furthermore, polyurethane can particularly provide: temperature stability; resilience; elastic memory; vibration damping; noise reduction; solvent resistance; hydrolytic stability; and color tolerance. It is well known that the electrochemically detachable adhesive WO2016 / 135341 (Henkel AG & Co. KGaA) applies pre-formed polyurethane polymers to hot-melt adhesives; however, this has the disadvantages of requiring specialized equipment and the adhesive's performance being sensitive to application temperature.

[0014] The industry still needs to provide curable polyurethane adhesive compositions that can be easily applied to the surface of substrates to be bonded, which, after curing, can provide effective bonding in composite structures containing such substrates, but can be effectively detached from such substrates by simply applying a potential to the cured adhesive. [Summary of the Invention]

[0015] According to a first aspect of the present invention, a curable and electrochemically detachable two-component (2K) adhesive composition is provided, comprising: a first component comprising: i) at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols; ii) other active hydrogen compounds, if applicable; and iii) a non-polymerizable electrolyte; and a second component comprising at least one polyisocyanate, wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is at least 1:1. In the case where the molar equivalent ratio is greater than 1:1, the stoichiometric excess of isocyanate (NCO) groups causes the formation of an NCO functional polymer upon reaction of the first and second components.

[0016] A curable and electrochemically detachable two-component (2K) adhesive composition preferably comprises, by weight of the composition: a first component comprising: 20 to 80 wt.%, preferably 20 to 60 wt.%, of i) at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols and polycarbonate polyols; ii) other active hydrogen compounds, where applicable; and 1 to 20 wt.%, preferably 1 to 10 wt.%, of iii) a nonpolymerizable electrolyte; and a second component comprising at least one polyisocyanate, wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is 1:1 to 1.2:1.

[0017] Good results have been obtained in the case where the curable and electrochemically detachable two-component (2K) adhesive composition comprises, based on the weight of the composition, the following: A first component comprising: 20 to 80 wt.%, preferably 20 to 60 wt.%, of i) at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols; ii) other active hydrogen compounds, where applicable; and 1 to 20 wt.%, preferably 1 to 10 wt.%, of iii) a non-polymerizable electrolyte, wherein the electrolyte comprises at least one non-polymerizable salt selected from the group consisting of: ammonium salts; pyridinium salts; phosphonium salts; imidazolium salts; oxazolium salts; guanidineium salts; and thiazolium salts; A second component comprising iv) at least one polyisocyanate, wherein the composition further comprises, based on the weight of the composition, 0.5 to 5 wt.%, of (v) At least one additive selected from the group consisting of: morin (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzofuran-4-one); 3,7-dihydroxy-2-naphthoic acid; gallocarboxylic acid; 3,4-dihydroxy-benzoguanidine-acetic acid; gallocarboxylic acid; p-aminosalicylic acid; 4,4'-methylene-bis(3-hydroxy-2-naphthoic acid); and citric acid; 0.005 to 5 wt.%, preferably 0.1 to 1 wt.%, of a catalyst; and 0.5 to 10 wt.%, of a non-conductive particulate filler, further wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is 1:1 to 1.2:1.

[0018] Although not absolutely necessary, the catalyst mentioned above is usually incorporated into the first polyol component of the composition.

[0019] According to a second aspect of the present invention, a bonding structure is provided, comprising: a first material layer having a conductive surface; and a second material layer having a conductive surface, wherein a cured electrochemically detachable two-component (2K) adhesive composition as defined above and in the appended claims is disposed between the first and second material layers.

[0020] According to a third aspect of the present invention, a method is provided for detaching the bonding structure as defined above and in the appended claims, the method comprising the steps of: i) applying a voltage to two surfaces to form an anode interface and a cathode interface; and ii) detaching the surfaces.

[0021] The step i) of this method is preferably characterized by at least one of the following: a) the applied voltage is from 0.5 to 200 V; b) the duration of the applied voltage is from 1 second to 60 minutes.

[0022] The adhesiveness of the composition is disrupted by applying a potential along the bonding line between the composition and the conductive surface. Without being bound by theory, it is assumed that a Faraday reaction occurring at the interface between the adhesive composition and the conductive surface disrupts the interaction between the adhesive and the substrate, thereby weakening the bond. This interface disruption can be the result of one or more processes, such as chemical degradation of the detachable material, gas escape from the interface, and / or material embrittlement due to changes in the crosslinking density of the adhesive composition.

[0023] Definition Unless the context clearly indicates otherwise, as used herein, the singular forms “a (a, an)” and “the” include the plural forms.

[0024] As used herein, the terms “comprising, comprises and comprised of” are synonymous with “including, includes” and “containing, contains”, and are inclusive or open-ended, and do not exclude additional, unlisted members, elements or method steps.

[0025] As used herein, the term "composed of" excludes any unspecified element, ingredient, member or method step.

[0026] When equivalents, concentrations, dimensions and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits or preferred upper and lower limits, it should be understood that this also specifically reveals any range that can be obtained by combining any upper or preferred value with any lower or preferred value, whether or not the obtained range is explicitly mentioned in the context.

[0027] Furthermore, according to the standard understanding, the weight range expressed as "from 0 to x" specifically includes 0 wt.%: the component defined by the range may not be in the composition, or may be present in the composition in an amount of up to x wt.%.

[0028] The terms “preferred,” “more preferably,” “desirably,” and “specifically” are used frequently herein to refer to embodiments of the present disclosure that may provide particular benefits in certain circumstances. However, the listing of one or more preferred, preferred, desired, or particular embodiments does not imply that other embodiments are useless, nor is it intended to exclude such other embodiments from the scope of the invention.

[0029] As used throughout this application, the word "may" is used in a permissive sense (meaning that it is possible) rather than a mandatory sense.

[0030] As used herein, room temperature is 23°C ± 2°C. As used herein, "ambient conditions" means the temperature and pressure of the environment in which the composition is situated or the environment in which the coating or the substrate of the coating is situated.

[0031] The molecular weights mentioned in this specification (used to describe the macromolecular, oligomeric, and polymeric components of the curable composition) can be measured using gel permeation chromatography (GPC) with a polystyrene calibration standard, for example, as performed according to ASTM 3536.

[0032] Unless otherwise specified, the viscosity of the coating compositions described herein is measured using a Brookfield viscometer under standard conditions of 20°C and 50% relative humidity (RH). The appropriate calibration method, rotor type, and rotational speed for the Brookfield viscometer to be measured should be selected according to the manufacturer's instructions.

[0033] In the context of this invention, "two-component (2K) composition" is understood to mean that the first component (A) and the second component (B) must be stored in separate containers due to their (high) reactivity. The two components are mixed only just before application and then reacted, typically without additional activation, during which bonds are formed and thus polymeric networks are formed. Higher temperatures may be applied herein to accelerate the crosslinking reaction.

[0034] As used herein, the term "electrochemically detachable" means that after the adhesive has cured, the bond strength is reduced by at least 50% when a potential of 70 V is applied for 20 minutes. The adhesive is applied between two substrates bonded by the adhesive, allowing current to flow through the adhesive bond lines. Bond strength is measured by a tensile lap shear (TLS) test performed at room temperature based on the ASTM D3163-01 Standard Test Method for Determining Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints in Shear by Tension Loading. The bond overlap area is 2.50 cm x 1.25 cm (1" x 0.5"), with a bond thickness of 0.1 cm (40 mil).

[0035] As used herein, the term "monomer" means a substance that can undergo polymerization to provide constituent units to the chemical structure of a polymer. As used herein, the term "monofunctional" means having one polymerizable moiety. As used herein, the term "polyfunctional" means having more than one polymerizable moiety.

[0036] As used herein, the term "equivalent (eq.)" as commonly used in chemical notation refers to the relative number of reactive groups present in a reaction.

[0037] As used herein, an "active hydrogen compound" is a compound having at least one active hydrogen functional group. This functional group includes at least one hydrogen atom that can be readily dissociated from it. Preferably, the hydrogen atom is attached to a nitrogen atom, an oxygen atom, a phosphorus atom, or a sulfur atom, and thus, exemplary active hydrogen functional groups are hydroxyl functional groups, amino functional groups, and thiol functional groups.

[0038] As used herein, “polyol” means any compound containing two or more hydroxyl groups: the term is therefore intended to cover diols, triols and compounds containing four or more -OH groups.

[0039] As used herein, the term "fatty" means any compound containing one or more residues of a fatty acid. "Fatty acid" further means any predominantly unbranched, acyclic (preferably substantially linear) aliphatic carboxylic acid that substantially comprises an aliphatic hydrocarbon chain and at least one carboxyl group, preferably a single terminal carboxyl group, preferably composed of therefrom. Fatty acids may contain a limited number of other substituents (e.g., hydroxyl groups) and may be saturated, monounsaturated, or polyunsaturated.

[0040] The term "electrolyte" is used herein, according to its standard meaning in this art, as a substance containing free ions that can conduct electricity by means of the movement of charged carrier species. The term is intended to cover molten electrolytes, liquid electrolytes, semi-solid electrolytes, and solid electrolytes, wherein at least one of the cation or anionic components of the electrolyte structure is substantially free to move, thereby acting as charge carriers.

[0041] The curable adhesive composition of the present invention and the cured adhesive obtained therefrom have an "electrolyte function" because the adhesive material allows the conduction of ions (i.e., cations, cationic groups, or both). The electrolyte function should be understood as arising from the ability of the composition and the cured adhesive to solubilize ions having at least one polarity.

[0042] The term "Faraday reaction" refers to the electrochemical reaction in which a material is oxidized or reduced.

[0043] As used herein, "(meth)acrylic" is an abbreviation of "acrylic" and / or "methacrylic". Therefore, the term "(meth)acrylate" refers to both acrylate and methacrylate.

[0044] As used herein, "C1-Cn alkyl" refers to a group containing 1 to n carbon atoms, an alkane, and including monovalent groups with straight and branched organic groups. Therefore, "C1-C18 alkyl" refers to a group containing 1 to 18 carbon atoms, an alkane, and including monovalent groups with straight and branched organic groups. Examples of alkyl groups include (but are not limited to): methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; dibutyl; tributyl; n-pentyl; n-hexyl; n-heptyl; and 2-ethylhexyl. In this invention, such alkyl groups may be unsubstituted or may be substituted with one or more halogens. In cases applicable to a given part (R), the tolerance for one or more non-halogen substituents within the alkyl group will be indicated in the specification.

[0045] As used herein, the term "C1-C18 hydroxyalkyl" refers to a HO-(alkyl) having 1 to 18 carbon atoms, wherein the substituents are connected by means of an oxygen atom and the alkyl group is as defined above.

[0046] "Alkoxy" means a monovalent group represented by -OA, wherein A is an alkyl group: non-limiting examples are methoxy, ethoxy and isopropyloxy. As used herein, the term "C1-C18 alkoxyalkyl" means an alkyl group having an alkoxy substituent as defined above, wherein the moiety (alkyl-O-alkyl) comprises a total of 1 to 18 carbon atoms: such groups include methoxymethyl (-CH2OCH3), 2-methoxyethyl (-CH2CH2OCH3) and 2-ethoxyethyl.

[0047] As used herein, the term "C2-C4 alkyl" is defined as a saturated, divalent hydrocarbon group having 2 to 4 carbon atoms.

[0048] The term "C3-C18 cycloalkyl" should be understood to mean a saturated, monocyclic or polycyclic hydrocarbon group having 3 to 18 carbon atoms. In this invention, such cycloalkyl groups may be unsubstituted or substituted with one or more halogens. In cases applicable to a given part (R), the tolerance for one or more non-halogen substituents within the cycloalkyl group will be noted in the specification. Examples of cycloalkyl groups include: cyclopropyl; cyclobutyl; cyclopentyl; cyclohexyl; cycloheptyl; cyclooctyl; adamantane; and norbornene.

[0049] As used herein, "C6-C18 aryl" alone or as part of a larger portion (e.g., in "arylene") refers to monocyclic, bicyclic, and tricyclic systems, wherein the monocyclic system is aromatic or at least one of the bicyclic or tricyclic systems is aromatic. Bicyclic and tricyclic systems include benzo[a]fused 2-3 carbon rings. In this invention, such aryl groups may be unsubstituted or substituted with one or more halogens. In cases applicable to a given part (R), the tolerance for one or more non-halogen substituents within the aryl group will be noted in the specification. Exemplary aryl groups include: phenyl; (C1-C4)alkylphenyl, such as tolyl and ethylphenyl; indenyl; naphthyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthrayl; and anthracel. A preference for phenyl groups is also noted.

[0050] As used herein, "C2-C24 alkenyl" refers to a hydrocarbon group having 2 to 24 carbon atoms and at least one alkene unsaturated unit. The alkenyl group may be straight-chain, branched, or cyclic and may be substituted with one or more halogens, as appropriate. In cases applicable to a given part (R), the tolerance for one or more non-halogen substituents within the alkenyl group will be specified in the specification. The term "alkenyl" also encompasses groups having "cis" and "trans" configurations or alternatively "E" and "Z" configurations, as understood by those skilled in the art. However, in general, attention should be paid to the preference for unsubstituted alkenyl groups containing 2 to 10 (C2-10) or 2 to 8 (C2-8) carbon atoms. Examples of such C2-C12 alkenyl groups include (but are not limited to): -CH═CH2; -CH═CHCH3; -CH2CH═CH2; -C(═CH2)(CH3); -CH═CHCH2CH3; -CH2CH═CHCH3; -CH2CH2CH═CH2; -CH═C(CH3)2; -CH2C(═CH2)(CH3); -C(═CH2)CH2CH3; -C(CH3)═CHCH3; -C(CH3)CH═CH2; -CH═CHCH2CH2CH3; - CH2CH═CHCH2CH3;-CH2CH2CH═CHCH3;-CH2CH2CH2CH═CH2;-C(═CH2)CH2CH2CH3;-C(CH3)═CHCH2CH3;-CH(CH3)CH═CHCH;-CH(CH3)CH2CH═CH2;-CH2CH═C(CH3)2;1-Cyclopent-1-enyl;1-Cyclopent-2-enyl;1-Cyclopent-3-enyl;1-Cyclohex-1-enyl;1-Cyclohex-2-enyl;and 1-Cyclohexyl-3-enyl。

[0051] As used herein, "alkylaryl" means an aryl group substituted with an alkyl group, both of which are as defined above. Furthermore, as used herein, "aralkyl" means an alkyl group substituted with an aryl group as defined above.

[0052] As used herein, the term "hetero" refers to a group or part containing one or more heteroatoms (e.g., N, O, Si, and S). Thus, for example, "heterocyclic" refers to a cyclic group having, for example, N, O, Si, or S as part of its ring structure. "Heteroalkyl," "heterocycloalkyl," and "heteroaryl" portions are, as defined above, alkyl, cycloalkyl, and aryl groups containing N, O, Si, or S as part of their structure.

[0053] The compositions of the present invention may be defined herein as "substantially free" of certain compounds, elements, ions, or other similar components. The term "substantially free" is intended to mean that the compounds, elements, ions, or other similar components are not intentionally added to the composition and are present at most in trace amounts that should have no (adverse) effect on the desired properties of the coating. An exemplary trace amount is less than 1000 ppm by weight of the composition. The term "substantially free" covers examples where the specified compounds, elements, ions, or other similar components are not present in the composition at all or in any amount that can be measured by techniques commonly used in this art.

Implementation Method

[0055] 1. A first component of a two-component (2K) composition. The first component of the composition comprises: i) at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols; ii) other active hydrogen compounds, if applicable; and iii) a non-polymerizable electrolyte. It is reiterated that the composition of the present invention is characterized in that the molar equivalent ratio of the NCO group (the reactant provided by the second part of the composition) to the active hydrogen atom is at least 1:1, for example, from 1:1 to 1.5:1, and preferably from 1:1 to 1.2:1. The first component of the composition may further be characterized in that it comprises 20 to 80 wt.%, for example, 20 to 60 wt.%, of i) the at least one polyol selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols.

[0056] i) At least one reactant polyol in the polyol bicomponent (2K) composition must be selected from the group consisting of: fatty alcohols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols. This polyol or polyols preferably have a number average molecular weight (Mn) of 200 to 50,000 g / mol, for example, 200 to 8,000 g / mol. Alternatively, or in addition to this molecular weight characterization, the hydroxyl value of the reactant polyol preferably has a value of 2 to 850 mg KOH / g, for example, 25 to 500 mg KOH / g.

[0057] Polycarbonate diols can be obtained by reacting a carbonate derivative with a diol. Exemplary carbonate derivatives include diaryl carbonates (including, but not limited to, diphenyl carbonates), di(C1-C6) alkyl carbonates, and phosgene. Exemplary diols include, but are not limited to: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,3-butanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; cyclohexanediol; diethylene glycol; dipropylene glycol; neopentanediol; and mixtures thereof.

[0058] Polyester diols can be obtained by reacting the diol with an aliphatic, aromatic, or cycloaliphatic dicarboxylic acid, or in some cases, their corresponding anhydrides: the reaction can be carried out in the presence of an esterification catalyst, if appropriate. Examples of suitable dicarboxylic acids include (but are not limited to): adipic acid; glutaric acid; pimelic acid; octanoic acid; azelaic acid; decanedicarboxylic acid; succinic acid; maleic acid; sebacic acid; azelaic acid; terephthalic acid; isophthalic acid; phthalic acid; tetrahydrophthalic acid; hexahydrophthalic acid; trimellitic acid; and 1,4-cyclohexanedicarboxylic acid. Examples of suitable anhydrides include succinic anhydride, phthalic anhydride, and trimellitic anhydride. It should be noted that various commercially available dimer fatty acids in saturated (hydrogenated) or unsaturated forms can also be used as dicarboxylic acids. Furthermore, examples of suitable diols for preparing polyester diols include: ethylene glycol; di, tri, or tetraethylene glycol; 1,2-propanediol; di, tri, or tetrapropanediol; 1,3-propanediol; 1,4-butanediol; 1,3-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,5-pentanediol; 2,2-dimethyl-1,3-propanediol (neopentanediol); 1,4-dihydroxycyclohexane; 1,4-dimethylcyclohexane; 1,8-octanediol; 1,10-decanediol; 1,12-decanediol; 2,2,4- and / or 2,4,4-trimethyl-1,3-pentanediol; and mixtures thereof.

[0059] Other useful polyester glycols are those obtained by polymerization of hydroxycarboxylic acids or their lactones containing 2 to 12 carbon atoms, starting from a glycol. The hydroxycarboxylic acid may be saturated or unsaturated, linear or branched, and examples include: glycolic acid; lactic acid; 5-hydroxyvalerate; 6-hydroxyhexanoic acid; ricin oleic acid; 12-hydroxystearic acid; 12-hydroxydodecanoic acid; 5-hydroxydodecanoic acid; 5-hydroxydecanoic acid; and 4-hydroxydecanoic acid. Examples of suitable lactones are β-propiolactone, δ-valerate, (C1-C6)alkyl-valerate, ε-caprolactone, and (C1-C6)alkyl-ε-caprolactone.

[0060] Examples of commercially available polyether-polyester polyols that are effective in this invention include Solvermol® 805 and Solvermol® 750, which are available from BASF.

[0061] In addition to the above, preferably at least one polyol-based polyether polyol derived from polyurethane, particularly polyether polyols with a polydispersity (PD) of less than 2, more preferably less than 1.5, and even more preferably less than 1.3. For completeness, "polyether" is understood for the purposes of this invention as a polymer in which the repeating unit contains an ether functional COC in the main chain. Therefore, polymers having lateral ether groups (e.g., cellulose ethers, starch ethers, and vinyl ether polymers, as well as polyacetals) are not included in this definition. Desiredly, the polyether polyol is a polyoxyalkylene glycol and specifically a polyoxyalkyl (C2-C3)alkylene glycol. For completeness, the term polyoxyalkyl (C2-C3)alkylene refers to a polyether group derived from ethylene oxide, propylene oxide, or both ethylene oxide and propylene oxide.

[0062] In some embodiments of the present invention, the first component comprises at least one fatty polyol. Suitable fatty polyols include, for example, fatty acids, fatty acid esters, fatty acid amides, and their fatty acid dimers, trimers, oligomers, or polymers, provided that such compounds have two or more hydroxyl groups. The hydroxyl functional groups of suitable fatty polyols may be located on fatty acid residues, other parts of the molecule, or both.

[0063] As exemplary fatty polyols, references may be made to: castor oil; hydroxylated products of unsaturated or polyunsaturated natural oils; hydrogenated products of unsaturated or polyunsaturated polyhydroxy natural oils; polyhydroxy esters of alkyl hydroxy fatty acids; polymerized natural oils; and alkyl hydroxylated amides of fatty acids. Note the preference for the following, used alone or in combination: castor oil; hydroxylated soybean oil; hydrogenated castor oil; polymerized castor oil; hydroxyethyl ricinoleate; and hydroxyethyl ricinoleate amide.

[0064] ii) Optional other active hydrogen compounds: Some polyols can act not only as reactants in the synthesis of polyurethanes, but also as solubilizers for non-polymerizable electrolytes. In a broader sense, solubilizers have the function of promoting the miscibility of electrolytes in adhesive compositions formed by mixing their two components: therefore, solubilizers are preferably polar compounds and are expected to be liquid at room temperature.

[0065] In this category, references may be made to: polyoxyalkylene glycols; polyols; and sugars. Although polyoxyalkylene glycols have been mentioned above, it should be noted that this solubilizing function can be specifically obtained by using polyoxyalkyl (C2-C3) alkylene glycols with a weight average molecular weight of 200 to 10,000 g / mol, for example, 200 to 2,000 g / mol.

[0066] Polyols and sugars that have the effect of acting as a solubilizer and can be used alone or in combination: including (but not limited to): ethylene glycol, 1,3-propanediol, cyclohexanediol, hydroquinone, catechol, resorcinol, phloroglucinol, gallol, hydroxyhydroquinone, serotonin, serotonin having three methyl or ethyl substituents bonded to the remaining benzene carbon atom, isosorbide, dehydromannitol, isoidide, glycerol, cyclohexane-1,2,4-triol, 1,3,5-cyclohexane Triols, pentane-1,2,3-triols, hexane-1,3,5-triols, erythritol, 1,2,4,5-tetrahydroxybenzene, threitol, arabinitol, xylitol, ribitol, mannitol, sorbitol, inositol, fructose, glucose, mannose, lactose, 1,1,1-tris(hydroxymethyl)propane, 1,1,1-tris(hydroxymethyl)ethane, trimethylolpropane, di(trimethylolpropane), trimethylolpropane ethoxylate, 2-hydroxymethyl-1,3-propanediol, neopentyltetrol allyl ether, and neopentyltetrol.

[0067] It should be noted that at least one monohydric alcohol is preferably used as an alternative active hydrogen reaction ii) in the synthesis of polyurethanes. For example, monofunctional hydrophilic polyoxyethylene (e.g., polyethylene oxide or oxypropylene oxide) can be incorporated into polyurethanes as a means of modifying the properties of latex and improving its emulsion-forming ease. When included, the monohydric alcohol should be based on i) the presence of the at least one polyhydric alcohol in an amount of 0.1 to 5 wt.% by weight.

[0068] This invention does not exclude the presence of a chain extender in the first component, particularly with respect to embodiments in which the NCO functional compound of the second component comprises an NCO functional prepolymer or is composed thereof. As those skilled in the art know, typical chain extenders have a weight average molecular weight (Mw) of 18 to 500 g / mol and have at least two groups containing active hydrogen. Although water can therefore be used as a chain extender, it is preferred that the two-component (2K) composition is substantially anhydrous. However, the use of polyamines may be suggested, and as examples of polyamines that can be used alone or in combination, the following may be mentioned: amination of polypropylene glycol, such as Jeffamine D-400 available from Huntsman Chemical Company; hydrazine; hexahydropyrazine; aminoethylhexahydropyrazine; 2-methylhexahydropyrazine; 1,5-diamino-3-methyl-pentane; isophorone diamine; ethylenediamine; diaminobutane; hexanediamine; hexamethylenediamine; tetramethyltetramine; aminoethylpropyltrimethoxysilane; diethyltriamine; triethyltetramine; triethylpentamine; ethanolamine; and lysine.

[0069] In the case of chain extenders, the amount added is constrained by the molar equivalent ratio of the active hydrogen atoms to the NCO groups mentioned above in the two-component (2K) composition.

[0070] iii) Non-polymerizable electrolyte: Based on the weight of the two-component (2K) composition, the composition contains 1 to 20 wt.% of a non-polymerizable electrolyte: the electrolyte preferably constitutes 1 to 10 wt.% of the composition, for example 2 to 10 wt.%.

[0071] Important electrolytes include non-polymerizable salts of the following: ammonium; pyridinium; phosphorus; imidazolium; oxazolium; guanidineium; and thiazolylium. More specifically, the electrolyte of the present invention shall comprise at least one salt having a formula selected from the group consisting of: wherein: R1, R2, R3, R4, R5 and R6 are independently selected from hydrogen, C1-C18 alkyl, C3-C18 cycloalkyl, C6-C18 aryl, C7-C24 aralkyl, C2-C20 alkenyl, -C(O)Rq, -C(O)OH, -CN and -NO2; and Rq is a C1-C6 alkyl.

[0072] When using ammonium salts, the following restrictions apply: at most three of the groups R1 to R4, and preferably at most two, can be hydrogen.

[0073] Regarding these portions R1 to R6, the terms C1-C18 alkyl, C3-C18 cycloalkyl, C6-C18 aryl, C7-C24 aralkyl, and C2-C20 alkenyl explicitly include groups in which one or more hydrogen atoms are substituted with a halogen atom (e.g., C1-C18 haloalkyl) or a hydroxyl group (e.g., C1-C18 hydroxyalkyl). Specifically, preferably, R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, C1-C12 alkyl, C1-C12 haloalkyl, C1-C12 hydroxyalkyl, and C3-C12 cycloalkyl. For example, R1, R2, R3, R4, R5, and R6 may be independently selected from hydrogen, C1-C6 alkyl, C1-C6 haloalkyl, and C1-C6 hydroxyalkyl.

[0074] This is not intended to specifically limit the counter anions (X-) that can be used in electrolytes. Exemplary anions may be selected from: • Halogen ions; • Pseudohalogen ions and halogen-containing compounds of the formulas PF6-, CF3SO3-, (CF3SO3)2N-, CF3CO2-, and CCl3CO2-; • CN-, SCN-, and OCN-; • Phenate; • Sulfate, sulfite, and sulfonate of the general formulas SO42-, HSO4-, SO32-, HSO3-, RaOSO3-, and RaSO3-; • Phosphate of the general formulas PO43-, HPO42-, H2PO4-, RaPO42-, HRaPO4-, and RaRbPO4-; • Phosphate and phosphinate of the general formulas RaHPO3-, RaRbPO2-, and RaRbPO3-; Phosphite anions of general formulas: PO33-, HPO32-, H2PO3-, RaPO32-, RaHPO3-, and RaRbPO3-; phosphite and phosphinite anions of general formulas: RaRbPO2-, RaHPO2-, RaRbPO-, and RaHPO-; carboxylic acid anions of general formula RaCOO-; hydroxycarboxylic acid anions and glycoacid anions; glycoacid anions (salts of o-benzoic acid sulfadiazine); borate anions of general formulas: BO33-, HBO32-, H2BO3-, RaRbBO3-, RaHBO3-, RaBO32-, B(ORa)(ORb)(ORc)(ORd)-, B(HSO4)-, and B(RaSO4)-; phosphate anions of general formulas: RaBO22- and RaRbBO-; • Carbonates and carbonates of general formulas HCO3-, CO32-, and RaCO3-; • Silicates and silicates of general formulas SiO44-, HSiO43-, H2SiO42-, H3SiO4-, RaSiO43-, RaRbSiO42-, RaRbRcSiO4-, HRaSiO42-, H2RaSiO4-, and HRaRbSiO4-; • Alkyl and aryl silicates of general formulas RaSiO33-, RaRbSiO22-, RaRbRcSiO-, RaRbRcSiO3-, RaRbRcSiO2-, and RaRbSiO32-; • Pyridates and pyrimidates; Carboxylic acid imines, bis(sulfonyl)imines, and sulfonylimines of the following general formulas: • Methylates of the following general formulas: • Alkoxides and aromatic oxides of general formula RaO-; and • Sulfides, hydrogen sulfides, polysulfides, polysulfides, and thiols of general formulas S2-, HS-, [Sv]2-, [HSv]-, and [RaS]-, where v is a positive integer from 2 to 10 in the general formula.Ra, Rb, Rc, and Rd are independently selected from hydrogen, C1-C12 alkyl, C5-C12 cycloalkyl, C5-C12 heterocycloalkyl, C6-C18 aryl, and C5-C18 heteroaryl.

[0075] Based on the definitions in the above list, preferred anions are selected from the group consisting of: halide ions; pseudohalides and halogenated compounds as defined above; carboxylic acid anions, particularly formate, acetate, propionate, butyrate and octanoate; hydroxycarboxylic acid anions, such as lactate; pyridylate and pyrimidineate; carboxylic acid imine, bis(sulfonyl)imine and sulfonylimine; sulfate, methyl sulfate anion and ethyl sulfate anion; sulfite; sulfonate, particularly methanesulfonate; and phosphate, particularly dimethyl phosphate anion, diethyl phosphate anion and di-(2-ethylhexyl) phosphate anion.

[0076] The electrolyte in Part 1 is preferably selected from the group consisting of: 1-ethyl-3-methyl-1H-imidazol-3-onthium methanesulfonate, 1-ethyl-3-methyl-1H-imidazol-3-onthium methylsulfate, 2-(2-fluoroanilino)pyridine-1-hexyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium nitriloimide, 2-(2-fluoroanilino)pyridine-1-butyl-1-methyl-pyrrolidone, 1-butyl-1-methyl-pyrrolidone nitriloimide, 2-(2-fluorophenylene) Trihexyl(tetradecyl)phosphonium (amino)-pyridine, cyclohexyltrimethylammonium bis(trifluoromethanesulfonyl)imine, di(2-hydroxyethyl)ammonium trifluoroacetate, N,N-dimethyl(2-hydroxyethyl)ammonium octanoate, methyltrioctylammonium bis(trifluoromethanesulfonyl)imine, N-ethyl-NNNN-tetramethylguanidine trifluoromethanesulfonate, guanidine trifluoromethanesulfonate, 1-butyl-4-methylpyridinium bromide, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-3-hydroxymethylpyridinium ethylsulfate Pyridium, 1-Butyl-1-methylpyrrolidone bis(trifluoromethylsulfonylmethylene)imidine, 1-Butyl-methylpyrrolidone (pentafluoroethyl)trifluorophosphate, 3-methylimidazolium ethylsulfate, 1-Ethyl-3-methylimidazolium chloride, 1-Ethyl-3-ethyl-methylimidazolium bromide, 1-Butyl-3-methylimidazolium chloride, 1-Hexyl-3-methylimidazolium chloride, 1-Octyl-3-methylimidazolium chloride, 1-Methyl-3-octylimidazolium chloride, 1-Propyl-3-methylimidazolium iodide Imidazolium, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-butylimidazolium, 1-methylimidazolium tetrafluoroborate, tetrabutylphosphonium trifluorophosphate (pentafluoroethyl)trifluorophosphate, trihexyl(tetradecyl)phosphonium tetrafluoroborate, and mixtures thereof. A particular preference may be mentioned for the use of at least one of the following: 1-ethyl-3-methyl-1H-imidazol-3-onium methanesulfonate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and 1-ethyl-3-methyl-1H-imidazol-3-onium methylsulfate.

[0077] 2. The second component of the two-component (2K) composition iv) The second component of the polyisocyanate composition comprises at least one polyisocyanate. As used herein, "polyisocyanate" means a compound containing at least two -N=C=O functional groups, for example, 2 to 5 or 2 to 4 -N=C=O functional groups. Suitable polyisocyanates include aliphatic, cycloaliphatic, aromatic and heterocyclic isocyanates, their dimers and trimers and mixtures thereof.

[0078] Aliphatic and cycloaliphatic polyisocyanates may comprise 6 to 100 carbon atoms linked in a straight chain or cyclized, each having at least two isocyanate reactive groups. Examples of suitable aliphatic isocyanates include (but are not limited to) straight-chain isocyanates, such as ethyl diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,6,11-undecane triisocyanate, 1,3,6-hexamethylene triisocyanate, bis(ethyl isocyanate) carbonate, and bis(ethyl isocyanate) ether. Examples of cycloaliphatic polyisocyanates include (but are not limited to) dicyclohexylmethane 4,4′-diisocyanate (H12MDI), 1-isocyanomethyl-3-isocyano-1,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), cyclohexane 1,4-diisocyanate, hydrogenated phenyl dimethyl diisocyanate (H6XDI), 1-methyl-2,4-diisocyano-cyclohexane, m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-TMXDI), and dimer fatty acid diisocyanates.

[0079] The term “aromatic polyisocyanate” is used herein to describe an organic isocyanate in which the isocyanate group is directly linked to a ring of a mononuclear or polynuclear aromatic hydrocarbon group. Furthermore, a mononuclear or polynuclear aromatic hydrocarbon group means a basic planar cyclic hydrocarbon moiety of a conjugated double bond, which may be a monocyclic or may include multiple condensed or covalently linked rings. The term aromatic also includes alkylaryl. Typically, the hydrocarbon (main) chain comprises 5, 6, 7 or 8 main chain atoms in a ring. Examples of such planar cyclic hydrocarbon moiety include (but are not limited to) cyclopentadienyl, phenyl, naphthyl-,

[10] arunenyl- (1,3,5,7,9-cyclopentadecanyl-),

[12] arunenyl-, [8] arunenyl-, phenaene (benzonaphthalene), 1,9-dihydropyrene and β (1,2-benzophenanthrene). Examples of alkylaryl moiety are benzyl, phenethyl, 1-phenylpropyl, 2-phenylpropyl, 3-phenylpropyl, 1-naphthylpropyl, 2-naphthylpropyl, 3-naphthylpropyl and 3-naphthylbutyl.

[0080] Exemplary aromatic polyisocyanates include (but are not limited to): all isomers of toluene diisocyanate (TDI), in isomeric pure form or as a mixture of several isomers; naphthalene 1,5-diisocyanate; diphenylmethane 4,4′-diisocyanate (MDI); diphenylmethane 2,4′-diisocyanate and mixtures of diphenylmethane 4,4′-diisocyanate with 2,4′ isomers or mixtures thereof with oligomers of higher functionality (so-called crude MDI); xylene dimethyl diisocyanate (XDI); diphenyl-dimethylmethane 4,4′-diisocyanate; di- and tetraalkyl-diphenylmethane diisocyanate; dibenzyl 4,4′-diisocyanate; xylene 1,3-diisocyanate; and xylene 1,4-diisocyanate.

[0081] If necessary, the polyisocyanate can be biureted and / or isocyanurized by methods commonly known, such as those described in British Patent No. 889,050.

[0082] The term "polyisocyanate" is also intended to cover prepolymers obtained by partially reacting the aliphatic, cycloaliphatic, aromatic and heterocyclic isocyanates mentioned above with polyols to obtain isocyanate-functionalized oligomers, which may be used alone or in combination with free isocyanates. When used, the NCO-functionalized prepolymer is preferably characterized by at least one of the following: a) an NCO content of 5 to 30%, preferably 10 to 25 wt.%, based on the weight of the prepolymer; b) an NCO functionality of 2.2 to 3.0, preferably 2.2 or 2.4 to 2.9; c) a viscosity of 300 to 35,000 mPa·s, preferably 1,000 to 10,000 mPa·s at 20°C; d) a number average molecular weight (Mn) of 500 to 30,000, for example 500 to 15,000 or 500 to 10,000 g / mol. For completeness, these characteristics a) to d) are not intended to be mutually exclusive: in fact, the prepolymer may conform to one, two, three or four of the characteristics described herein.

[0083] Commercially available examples of suitable polyisocyanates include (but are not intended to limit the invention) the Desmodur product family, such as Desmodur E 744, available from Covestro Deutschland; Hysol HF6005 isocyanate, available from Henkel Corporation; the Isonate M product family, available from The Dow Chemical Company; the Lupronat product family, available from BASF; and the Suprasec product family, available from Huntsman.

[0084] Additives and Additives The compositions obtained in this invention will generally further comprise adjuvants and additives that impart modified properties to the compositions. For example, adjuvants and additives may impart one or more of the following: modified elastic properties; modified elastic recovery; longer start-up time; faster curing time; and lower residual tack. Such adjuvants and additives include: catalysts; solubilizers; toughening agents; conductive particles; non-conductive fillers; plasticizers; stabilizers, including UV stabilizers; antioxidants; reactive diluents; desiccants or humectants; adhesion promoters; fungicides; flame retardants; rheology adjuvants; pigments or color pastes; solvents; and non-reactive diluents.

[0085] These adjuvants and additives may be used as desired in these combinations and proportions, provided that they do not adversely affect the properties and fundamental properties of the composition. Although there may be exceptions in some cases, the total amount of these adjuvants and additives should not exceed 40 wt.% of the total composition, and preferably should not exceed 30 wt.% of the composition.

[0086] For completeness, it should be noted that, generally speaking, additives and adjuvants containing reactive groups should be incorporated into appropriate portions of the two (2K) component composition to ensure its storage stability. Non-reactive materials may be formulated into one or both of the two components.

[0087] The composition, and conventionally, its first component may contain a standard catalyst for the reaction between the polyisocyanate and the active hydrogen compound, as known in the art. Such catalysts include (but are not limited to): stannous salts of carboxylic acids, such as stannous octoate, stannous oleate, stannous acetate, and stannous laurate; dialkyltin dicarboxylic acids, such as dibutyltin dilaurate and dibutyltin diacetate; tertiary amines; alkanolamine compounds; 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine; tetraalkylammonium hydroxide; alkali metal hydroxides; alkali metal alkoxides; tin alkoxylates, such as dibutyldimethoxytin, dibutyldiphenoxytin, and dibutyldiisopropoxytin; tin oxides, dibutyl... Tin oxide and dioctyltin oxide; reaction products of dibutyltin oxide and phthalates; tin thiolates; alkyl titanates; organoaluminum compounds, such as aluminum triacetylpyruvate, aluminum triacetyl ethyl acetate, and aluminum diisopropoxyacetyl ethyl acetate; chelate compounds, such as zirconium tetraacetylpyruvate and titanium tetraacetylpyruvate; organosilicon titanium compounds; bismuth tris-2-ethylhexanoate, bismuth neodecanoate complexes, and bismuth complexes with hydroxypropyl ethylenediamine and hydroxyethyl ethylenediamine, as Bicat® catalysts from Everchem Acquired from Specialty Chemicals; acid compounds, such as phosphoric acid and p-toluenesulfonic acid; triphenylborane; triphenylphosphine; 1,8-diazabicycloundec-7-ene (DBU); 1,5-diazabicyclo[4.3.0]non-5-ene; 1,4-diazabicyclo[2.2.2]octane; 4-dimethylaminopyridine; 1,5,7-trizabicyclo[4.4.0]dec-5-ene; 7-methyl-1,5,7-trizabicyclo[4.4.0]dec-5-ene; 1,8-bis(tetramethylguanidine)naphthalene; and 2-tert-butyl-1,1,3,3-tetramethylguanidine. Depending on the nature of the isocyanate, the amount of catalyst used is typically in the range of 0.005 to 5 wt.%, for example, 0.1 to 1 wt.%, of the two-component (2K) composition.

[0088] As described above, the solubilizer has the function of promoting the miscibility of the electrolyte within the adhesive composition formed when the two components are mixed: the solubilizer may or may not form part of the polymer matrix formed when the adhesive composition cures, but it does facilitate ion transfer therein. Therefore, the solubilizer is preferably a polar compound and preferably should be a liquid at room temperature.

[0089] In addition to the polyol solubilizers mentioned above, suitable categories of solubilizers without hydroxyl functionality include: polyphosphazenes; polymethylene sulfides; polyethyleneimine; polysiloxane surfactants and fluorinated polysiloxane surfactants, such as fluorinated polysilanes, polyalkylsiloxanes and polyoxyethylene-modified polydimethylsiloxanes; and copolymers of functionalized polyalkylsiloxanes with epoxy resins, such as copolymers of polydimethylsiloxane (PDMS) and epoxy resins. Based on the weight of the composition, such non-hydroxyl functional solubilizers may generally be included in the two-component (2K) composition in an amount of 0 to 5 wt.%.

[0090] In some cases, the presence of a toughening agent in the composition may facilitate the release of the cured adhesive. Without being bound by theory, the toughening agent may promote phase separation within the cured adhesive at the applied potential. In exemplary embodiments, the adhesive of the present invention may therefore contain 0.1 to 10 wt.% of a polybutadiene-based toughening agent based on the weight of the composition. Exemplary commercially available polybutadiene-based toughening agents include Poly bd® R20 LM and Poly bd® 15 HT, available from Cray Valley.

[0091] The compositions of the present invention may contain conductive particles. For example, based on the weight of the composition, the composition may contain 0 to 10 wt.% or 0 to 5 wt.% conductive particles.

[0092] In a broad sense, there is no specific intention to limit the shape of the particles used as conductive fillers: needle-like, spherical, elliptical, cylindrical, bead-like, cubic, or plate-like particles may be used alone or in combination. Furthermore, it is conceivable to use aggregates of more than one particle type. Similarly, there is no specific intention to limit the size of the particles used as conductive fillers. However, these conductive fillers conventionally have an average volume particle size of 0.1 to 1500 μm, or 1 to 1250 μm, as measured by laser diffraction / scattering methods.

[0093] Exemplary conductive particulate fillers include (but are not limited to): silver; copper; gold; palladium; platinum; nickel; gold or silver coated nickel; carbon black; carbon fiber; 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; nano-silver; nano-aluminum; nano-copper; nano-nickel; carbon nanotubes; and mixtures thereof. The use of particulate silver and / or carbon black as conductive fillers is preferred.

[0094] The compositions of the present invention may, as appropriate, contain non-conductive particulate fillers. For example, based on the weight of the composition, the composition may contain 0 to 10 wt.%, such as 0.5 to 10 wt.% or 0.5 to 5 wt.% of non-conductive particulate fillers.

[0095] In a broad sense, there is no specific intention to limit the shape of the particles used as non-conductive fillers: needle-like, spherical, elliptical, cylindrical, bead-like, cubic, or plate-like particles may be used alone or in combination. Furthermore, it is conceivable to use aggregates of more than one particle type. Similarly, there is no specific intention to limit the size of the particles used as non-conductive fillers. However, these non-conductive fillers conventionally have an average volume particle size of 0.1 to 1500 μm, or 1 to 1250 μm, as measured by laser diffraction / scattering methods.

[0096] Example non-conductive fillers include (but are not limited to) calcium carbonate, calcium oxide, calcium hydroxide (lime powder), precipitated and / or pyrolytic silicic acid, zeolite, bentonite, wollastonite, magnesium carbonate, diatomaceous earth, barium sulfate, alumina, clay, talc, titanium dioxide, iron oxide, zinc oxide, sand, quartz, flint, mica, glass beads, glass powder, and other ground minerals. Organic fillers may also be used, specifically wood fibers, wood flour, sawdust, cellulose, cotton, pulp, wood chips, shredded straw, grain husks, ground walnut shells, and other shredded fibers. Short fibers, such as glass fibers, glass filaments, polyacrylonitrile, carbon fibers, Kevlar fibers, or polyethylene fibers, may also be added.

[0097] Pyrolytic and / or precipitated silica advantageously has a BET surface area of ​​10 to 90 m² / g. When used, it does not cause any additional increase in the viscosity of the compositions of the present invention, but does help to strengthen the cured compositions.

[0098] It is also conceivable to use pyrolytic and / or precipitated silica with a higher BET surface area of ​​advantageously 100 to 250 m2 / g as a filler: due to the larger BET surface area, the effect of strengthening the curing composition can be achieved with a smaller weight proportion of silica.

[0099] Hollow spheres with mineral or plastic shells are also suitable as non-conductive fillers. These may be, for example, hollow glass spheres commercially available under the trademark Glass Bubbles®. Plastic-based hollow spheres (e.g., Expancel® or Dualite®) may be used and are described in EP 0 520 426 B1: which are made of inorganic or organic materials and each has a diameter of 1 mm or less, preferably 500 µm or less.

[0100] Non-conductive fillers that impart rheological properties to the composition may be preferred for many applications: such fillers are also described as rheology adjuvants, such as hydrogenated castor oil, fatty acid amides or expandable plastics, such as PVC.

[0101] The desired viscosity of the resulting curable composition determines the amount of filler used. Considering the latter, the total amount of filler (conductive and non-conductive) present in the composition should not prevent the composition from being easily applied to a substrate by a selected application method. For example, a curable composition intended to be extruded from a suitable dispensing device (e.g., a tube) should have a viscosity of 1,000 to 150,000, preferably 10,000 to 100,000 mPas.

[0102] Adding certain additives can promote the adhesion of the coating composition to a specific substrate. In this regard, based on the weight of the composition, the composition of the present invention may contain 0 to 5 wt.%, for example 0.5 to 5 wt.%, of the following: (v) at least one additive selected from the group consisting of: morin (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzofuran-4-one); 3,7-dihydroxy-2-naphthoic acid (3,7-dihydroxynaphthoic acid); gallophenolic acid (2,3,4-trihydroxybenzoic acid); 3,4-dihydroxy-benzoguanidine-acetic acid; gallic acid (3,4,5-trihydroxybenzoic acid); p-aminosalicylic acid (4-amino-2-hydroxybenzoic acid, PAS); flutter acid (4,4'-methylene-bis(3-hydroxy-2-naphthoic acid)); and citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid). Among these compounds, a preference may be mentioned for the use of citric acid, gallic acid, and specifically para-aminosalicylic acid (PAS), either alone or in combination.

[0103] For the purposes of this invention, a "plasticizer" is a substance that reduces the viscosity of a composition and thus promotes its processability. Based on the total weight of the composition, the plasticizer herein may constitute up to 10 wt.% or up to 5 wt.%, and is preferably selected from the group consisting of: diaminocarbamates; ethers of monofunctional, linear, or branched C4-C16 alcohols, such as Cetiol OE (available from BASF); esters of pinoresinic acid, butyric acid, thiobutyric acid, acetic acid, propionic acid, and citric acid; esters based on nitrocellulose and polyvinyl acetate; fatty acid esters; dicarboxylic acid esters; esters of fatty acids carrying OH groups or epoxidized fatty acids; glycolates; benzoates; phosphate esters; sulfonates; trimellitates; polyether plasticizers, such as end-capped polyethylene or polypropylene glycol; polystyrene; hydrocarbon plasticizers; chlorinated paraffins; and mixtures thereof. It should be noted that phthalates can be used as plasticizers in principle, but due to their toxicological potential, they are not preferred.

[0104] For the purposes of this invention, "stabilizer" should be understood as an antioxidant, heat stabilizer, or hydrolytic stabilizer. In this document, based on the total weight of the composition, the stabilizer may constitute a total of up to 10 wt.% or up to 5 wt.%. Standard commercially available examples of suitable stabilizers include: sterically hindered phenols; thioethers; benzotriazoles; benzophenone; benzoate esters; cyanoacrylates; acrylates; amines of the hindered amine light stabilizer (HALS) type; phosphorus; sulfur; and mixtures thereof.

[0105] To further enhance storage life, it is generally advisable to further stabilize the stability of the composition of the present invention in terms of moisture penetration by using a desiccant. Examples of suitable desiccants or dehumidifiers include (but are not limited to): silicone; anhydrous calcium sulfate (hard gypsum); calcium sulfate dihydrate (gypsum); calcium oxide; montmorillonite clay; molecular sieves, such as those including natural or synthetic zeolites; and activated alumina.

[0106] Sometimes it is also necessary to reduce the viscosity of the adhesive composition of the present invention for a particular application by using a reactive diluent. The total amount of reactive diluent present will typically be 0 to 10 wt.%, for example 0 to 5 wt.%, based on the total weight of the composition.

[0107] The presence of solvents and non-reactive diluents in the compositions of the present invention is not excluded, wherein such solvents can effectively adjust the viscosity. For example, but only for illustration, the compositions may contain one or more of the following: alkyl acetate solvents, such as ethyl acetate, n-propyl acetate, butyl acetate, n-butyl acetate, propylene glycol monomethyl ether acetate, and methoxypropyl acetate (MPA); alkyl propionate solvents, such as n-butyl propionate and n-pentyl propionate; diesters, such as dimethyl succinate, dimethyl glutarate, and dimethyl adipate; dialkyl carbonate solvents, such as ethylene carbonate, propylene carbonate (PC), dimethyl carbonate (DMC), ethyl ester methyl carbonate (EMC), and diethyl carbonate (DEC); ethers, such as tetrahydrofuran, dioxane, and dimethoxyethane; glycol ether solvents, such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, and ethylene glycol diethyl ether. Phenyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol di-n-butyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether and dipropylene glycol di-n-butyl ether; acetamide solvents dimethyl acetamide and N-methylpyrrolidone; ketone solvents, such as acetone, diisobutyl ketone, isobutylheptyl ketone, isophorone, methyl ethyl ketone, methyl n-pentyl ketone and methyl isobutyl ketone; toluene; xylene; diphenylmethane; diisopropylnaphthalene; petroleum fractions, such as Solvesso® products (available from Exxon); and chlorinated solvents, such as 4-chlorotrifluorotoluene and 3,4-bis(dichloro)trifluorotoluene.

[0108] In addition to the above, based on the total weight of the composition, the preferred solvent and non-reactive diluent constitute a total of less than 15 wt.%, specifically less than 10 wt.%.

[0109] Method and application: To form the defined two-component (2K) curable composition, reactive components are brought together and mixed in a manner that induces curing. The reactive compounds should be mixed under sufficient shear force to obtain a homogeneous mixture. This is thought to be achievable without special conditions or equipment. In other words, suitable mixing apparatus may include: static mixing apparatus; magnetic stirring rod apparatus; agitator apparatus; auger; batch mixer; planetary mixer; CW Brabender or Banburry® type mixer; and high-shear mixers, such as blade mixers and rotary impellers.

[0110] For small-scale applications where the volume is typically less than 2 liters, a preferred packaging for the two-component (2K) composition is a side-by-side twin-cylinder or coaxial cylinder, wherein two tubular chambers (usually of equal volume) are arranged side-by-side or internally within each other and sealed with pistons: the actuation of these pistons allows the portions to be advantageously extruded from the cylinder by means of a tightly fitted static or dynamic mixer. For larger-volume applications, the two components of the composition can be advantageously stored in cylinders or drums: in this case, the two components are supplied via a hydraulic press, specifically by means of extrusion from a plate, and via piping to a mixing device that ensures a fine and highly uniform mixing of the two components. In any case, for any packaging, it is important that the components are provided with an airtight and moisture-proof seal so that both components can be stored for extended periods, ideally 12 months or longer.

[0111] Non-limiting examples applicable to the two-part dispensing apparatus and method of the present invention include those set forth in U.S. Patent Nos. 6,129,244 and 8,313,006.

[0112] The first and second components of the composition are conventionally mixed in an amount (by weight) to achieve a desired ratio of NCO groups to active hydrogen atoms. For example, the weight ratio of the first component to the second component may be in the range of 4:1 to 1:4, preferably 2:1 to 1:2, for example 1:1.

[0113] Where applicable, the two-component (2K) curable composition should be extensively formulated to exhibit an initial viscosity of less than 200,000 mPa·s, for example less than 100,000 mPa·s at 25°C (measured immediately after mixing, for example, at most two minutes after mixing). Independent of or apart from this viscosity characteristic, the two-component (2K) composition should be formulated to be free of air bubbles (foam) during mixing and subsequent curing.

[0114] According to the most extensive process configuration of the present invention, the above composition is applied to a material layer and then cured in situ. Pretreatment of the relevant surfaces before application of the composition is generally recommended to remove foreign matter; if applicable, this step can promote the subsequent adhesion of the composition to it. Such treatments are known in the art and can be performed by, for example, using one or more of the following single-stage or multi-stage methods: etching treatment using an acid suitable for the substrate and, where appropriate, 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; treatment with a cleaning solvent, such as acetone, carbon tetrachloride, or trichloroethylene; and rinsing with water, preferably deionized water or demineralized water. In the case of using an aqueous alkaline degreasing bath, any degreasing agent remaining on the surface should be removed by rinsing the substrate surface with deionized water or demineralized water.

[0115] In some embodiments, adhesion of the coating composition of the present invention to the preferred pretreated substrate can be facilitated by applying an underlayer thereon. In practice, an underlayer composition may be required to ensure effective fixation and / or curing time of the adhesive composition on an inactive substrate. While those skilled in the art will be able to select a suitable underlayer, guiding references for selecting an underlayer include (but are not limited to): U.S. Patent No. 3,855,040; U.S. Patent No. 4,731,146; U.S. Patent No. 4,990,281; U.S. Patent No. 5,811,473; GB 2502554; and U.S. Patent No. 6,852,193.

[0116] The composition is then applied to the substrate by conventional application methods, such as brushing, rolling, doctor blade application, printing, and spraying, including (but not limited to) air atomizing spraying, air-assisted spraying, airless spraying and large-volume low-pressure spraying.

[0117] As described above, the present invention provides a bonding structure comprising: a first material layer having a conductive surface; and a second material layer having a conductive surface, wherein a curable electrochemically detachable two-part (2K) adhesive composition as defined above and in the appended claims is disposed between the first and second material layers. To produce this structure, an adhesive composition may be applied to at least one inner surface of the first and / or second material layers, and then the two layers may be subsequently brought into contact under applied pressure, such that the electrochemically detachable adhesive composition is inserted between the two layers.

[0118] It is recommended that the composition be applied to the surface with a wet film thickness of 10 to 500 μm. Applying thinner layers within this range is more economical and provides the possibility of reducing harmful thick cured areas. However, strict control must be exercised when applying thinner coatings or layers to avoid the formation of discontinuous cured films.

[0119] The curing of the composition applied according to the present invention generally occurs at a temperature in the range of 20°C to 80°C. A suitable temperature depends on the specific compound present and the desired curing rate, and can be determined in individual cases by a person skilled in the art using simple preliminary tests, if necessary. Of course, curing at lower temperatures within the range mentioned above is advantageous because it eliminates the need to substantially heat or cool the mixture from the generally prevailing ambient temperature. However, where applicable, the temperature of the mixture formed from the individual portions of the two (2K) fractional composition can be increased above the mixing temperature and / or the application temperature using conventional methods, including microwave induction.

[0120] As shown in Figure 1a, a bonding structure is provided in which a cured adhesive layer (10) is disposed between two conductive substrates (11). A non-conductive material layer (12) may be disposed on the conductive substrates (11) to form a more complex bonding structure, as illustrated in Figure 1b. Each conductive substrate layer (11) is in electrical contact with a power source (13), which may be a battery or an AC-driven direct current (DC) power source. The positive and negative terminals of the power source (13) are shown in a fixed position, but those skilled in the art will recognize that the polarity of the system can be reversed.

[0121] The two conductive substrates (11) are shown in the form of layers, which may be composed of, in particular, a metal film; a metal mesh or grid; deposited metal particles; a resin material that is conductive by means of conductive elements disposed therein; or a conductive oxide layer. As exemplary conductive elements, silver wires, 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 selection of conductive materials, those skilled in the art will recognize that when the conductive substrate (11) is in the form of a mesh or grid that provides limited contact with the cured adhesive layer (10), the efficiency of disengagement may be reduced.

[0122] When a voltage is applied between each conductive substrate (11), current is supplied to the adhesive composition (10) disposed therebetween. This initiates an electrochemical reaction at the interface between the substrate (11) and the adhesive composition. Such electrochemical reactions are understood to be oxidation at a positively charged or anodic interface and reduction at a negatively charged or cathode interface. It is believed that these reactions weaken the adhesive bonding between the substrates, thereby allowing easy removal of the detachable composition from the substrate.

[0123] As shown in Figures 2a and 2b, detachment occurs at the positive electrode interface, that is, the interface between the adhesive composition (10) and the conductive surface (11) that is in electrical contact with the positive electrode. By reversing the current direction before separating the substrates, the adhesive bonding at the interface of the two substrates can be weakened.

[0124] However, it should be noted that the composition of the adhesive layer (10) can be moderated so that detachment occurs at the positive or negative interface or simultaneously from both. In some embodiments, a voltage applied to both surfaces to form an anodic and cathode interface will result in simultaneous detachment at the anodic and cathode adhesive / substrate interfaces. In alternative embodiments, if the composition is unresponsive to direct current at both interfaces, reverse polarity can be used to simultaneously de-adhese at the substrate / adhesive interface. The current can be applied with any suitable waveform, provided that the total time for each polarity is sufficient for detachment to occur. In this regard, sinusoidal, rectangular, and triangular waveforms are appropriate and can be applied from a controlled voltage or controlled current source.

[0125] Without limiting the invention, it is believed that the release operation can be effectively carried out under at least one, and preferably both, of the following conditions: a) the applied voltage is 0.5 to 200 V, for example 10 to 100 V; and b) the duration of the applied voltage is 1 second to 120 minutes, for example 1 second to 60 minutes. In cases where the release of the conductive substrate from the cured adhesive is facilitated by applying force (e.g., via a weight or spring), it may only require applying a potential for a few seconds.

[0126] The following examples are used to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0127] The following materials were used in this example: Rizinusol Q1: Partially dehydrated castor oil, purchased from BASF. Voranol CP 1050: Glyceryl propoxylated polyether homopolymer triol, purchased from Dow Chemical. PES 216: Liquid polyester polyol (based on adipic acid, neopentyl glycol, 1,6-hexanediol and polypropylene glycol), purchased from Henkel Germany. Isonate M 143: Diphenylmethane diisocyanate, purchased from Dow Chemical. Basionics BC 01: 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate, purchased from BASF. TIB-Kat 216: Dioctyltin dilaurate (in butyl acetate, 5% by weight), purchased from TIB Chemicals. Sylosiv 3A: Micronized zeolite molecular sieve powder, purchased from WR Grace. Desmophen 4011T: Trifunctional polyether polyol, purchased from Covestro. Aerosil R202: Fuming silica treated with polydimethylsiloxane, purchased from Evonik Industries. 4-Aminosalicylic acid: Purchased from Alfa Aesar. Propylene carbonate: Purchased from Alfa Aesar. Glass microspheres: Particle size less than 100 micrometers, purchased from Sigma Aldrich. The formulations of this example are described in Table 1 below: Table 1 Components Element quantity (g) quantity (wt.%, based on the weight of the composition) First Component Rizinusol 1.52 16.9 Voranol CP 1050 0.76 8.5 PES 216 0.76 8.5 Basionics BC 01 0.45 5.0 4-Aminosalicylic acid 0.18 2.0 Desmophen 4011T 0.81 9.0 Propylene carbonate 0.45 5.0 Aerosil R202 0.25 2.8 Sylosiv 3A 0.35 3.9 TIB-Kat 216 0.028 0.3 Glass microspheres 0.27 3.0 Second component Isonate M 143 2.97 33.0 Aerosil R202 0.19 2.1

[0128] In preparing the first component, all components—polyol compound, 4-aminosalicylic acid, Basionic BC 01, propylene carbonate, Desmophen 4011T, and fuming silicon dioxide—were weighed into a beaker with a rod stirrer to dissolve the soluble components. Then, zeolite powder, glass microspheres, and a catalyst were added, and the mixture was homogenized in a high-speed mixer (1200 rpm, 1 minute).

[0129] In preparing the second component, the isocyanate and fuming silicon dioxide were mixed separately in a high-speed mixer (1200 rpm; 1 minute). Then the first and second components were mixed in a high-speed mixer (1200 rpm; 1 minute) with stirring.

[0130] The test substrate was made of stainless steel (1.4301), and its surface was cleaned with acetone paper towels. A 0.1-inch thick substrate was provided and cut into six 2.5 cm x 10 cm (1" x 4") samples for tensile testing. The tensile lap-shear (TLS) test was performed at room temperature based on the ASTM D3163-01 Standard Test Method for Determining Strength of Adhesively Bonded Rigid Plastic Lap-Shear Joints in Shear by Tension Loading. The bond overlap area of ​​each substrate was 2.50 cm x 1.25 cm (1" x 0.5"), with a bond thickness of 0.1 cm (40 mil).

[0131] The applied two-component (2K) adhesive composition was cured in the overlapping area by applying a temperature of 80°C for 120 minutes. The bonded structure was then stored overnight at 30°C and 55% relative humidity before the initial tensile test.

[0132] For each bonded substrate, the tensile lap shear strength was studied before and after the 24-hour storage period, prior to and after a constant potential of 70V was applied to the adhesive layer for 20 minutes. The average results are recorded in Table 2 below. Table 2 substrate Initial bonding strength (MPa) Bond strength (MPa) after 70 V for 20 minutes Stainless steel 8.48 1.56

[0133] In view of the foregoing description and examples, it will be obvious to those skilled in the art that equivalent modifications can be made without departing from the scope of the patent application. [Simplified Explanation of the Diagram]

[0054] The present invention will be described with reference to the accompanying drawings, in which: FIG1a illustrates a bonding structure according to a first embodiment of the present invention. FIG1b illustrates a bonding structure according to a second embodiment of the present invention. FIG2a illustrates the initial disengagement of the structure of the first embodiment when current passes through the other structure. FIG2b illustrates the initial disengagement of the structure of the second embodiment when current passes through the other structure.

Claims

1. A curable and electrochemically detachable two-component (2K) adhesive composition comprising: a first component comprising, based on the weight of the composition: 20 to 80 wt.% of i) at least one polyol selected from the group consisting of: aliphatic polyols, polyester polyols, polyether polyols, polyether-polyester polyols, and polycarbonate polyols; ii) other active hydrogen compounds, if applicable; and 1 to 20 wt.% of iii) a non-polymerizable electrolyte, wherein the electrolyte comprises a non-polymerizable salt selected from the group consisting of: ammonium salts; pyridinium salts; phosphonium salts; imidazolium salts; oxazolium salts; guanidineium salts; and thiazolium salts; and a second component comprising at least one polyisocyanate, wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is at least 1:

1.

2. The curable and electrochemically detachable two-component (2K) adhesive composition of claim 1, wherein, based on the weight of the composition, the composition comprises: a first component comprising: 20 to 60 wt.% of i) at least one polyol selected from the group consisting of: aliphatic polyols, polyester polyols, polyether polyols, polyether-polyester polyols and polycarbonate polyols; ii) other active hydrogen compounds, where applicable; and 1 to 10 wt.% of iii) a nonpolymerizable electrolyte; and a second component comprising at least one polyisocyanate, wherein the composition is characterized in that the molar equivalent ratio of NCO groups to active hydrogen atoms is 1:1 to 1.2:

1.

3. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in claim 1, wherein the portion i) of the or each polyol is characterized in that the number average molecular weight (Mn) is 200 to 50,000 g / mol.

4. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, wherein the portion i) of the or each polyol is characterized by a hydroxyl value of 2 to 850 mg KOH / g.

5. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any one of claims 1 to 3, wherein part i) comprises at least one fatty polyol.

6. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, wherein the ammonium salt has the following chemical formula; wherein: R1, R2, R3, and R4 are independently selected from hydrogen, C1-C18 alkyl, C3-C18 cycloalkyl, C6-C18 aryl, C7-C24 aralkyl, C2-C20 alkenyl, -C(O)Rq, -C(O)OH, -CN, and -NO2; Rq is a C1-C6 alkyl, and X- is a counter anion. In addition, up to three of the groups R1 to R4 can be hydrogen.

7. A curable and electrochemically degradable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, wherein the electrolyte is selected from the group consisting of: 1-ethyl-3-methyl-1H-imidazolium methanesulfonic acid, 1-ethyl-3-methyl-1H-imidazolium methylsulfate, 2-(2-fluoroanilino)-pyridine-1-hexyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium nitriloimide, 2-(2-fluoroanilino)-pyridine-1-butyl-1-methyl-pyrrolidone, 1- Butyl-1-methylpyrrolidinium nitriloimide, 2-(2-fluoroaniline)pyridinetrihexyl(tetradecyl)phosphonium, cyclohexyltrimethylammonium bis(trifluoromethanesulfonyl)nitriloimide, di(2-hydroxyethyl)ammonium trifluoroacetate, N,N-dimethyl(2-hydroxyethyl)ammonium octanoate, methyltrioctylammonium bis(trifluoromethanesulfonyl)nitriloimide, N-ethyl-NNNN-tetramethylguanidine trifluoromethanesulfonate, guanidine trifluoromethanesulfonate, 1-butyl-4-methylpyridinium bromide, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-Butyl-3-hydroxymethylpyridinium ethyl sulfate, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonylmethane)imidine, 1-Butyl-3-methylpyrrolidinium trifluorophosphate (pentafluoroethyl)trifluorophosphate, 3-methylimidazolium ethyl sulfate, 1-Ethyl-3-methylimidazolium chloride, 1-Ethyl-3-ethyl-methylimidazolium bromide, 1-Butyl-3-methylimidazolium chloride, 1-Hexyl-3-methylimidazolium chloride, 1-Octyl-3-methylimidazolium chloride, 1-Methyl-3-octylimidazolium chloride, 1-Iodide 1- Propyl-3-methylimidazolium, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butylimidazolium hexafluorophosphate, 1-butylimidazolium, 1-methylimidazolium tetrafluoroborate, tetrabutylphosphonium trifluorophosphate (pentafluoroethyl)trifluorophosphate, trihexyl(tetradecyl)phosphonium tetrafluoroborate, and mixtures thereof.

8. A curable and electrochemically degradable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, wherein the electrolyte is selected from the group consisting of 1-ethyl-3-methyl-1H-imidazol-3-onium methanesulfonic acid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonic acid, 1-ethyl-3-methyl-1H-imidazol-3-onium methylsulfate, and mixtures thereof.

9. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, comprising 0.5 to 5 wt.% (v) of at least one additive selected from the group consisting of: morin (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzofuran-4-one); 3,7-dihydroxy-2-naphthoic acid; gallocarboxylic acid; 3,4-dihydroxy-benzoguanidine-acetic acid; gallocarboxylic acid; p-aminosalicylic acid; 4,4'-methylene-bis(3-hydroxy-2-naphthoic acid); and citric acid.

10. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, comprising 0.5 to 5 wt.% of para-aminosalicylic acid (PAS) based on the weight of the composition.

11. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, comprising 0.005 to 5 wt.% of a catalyst based on the weight of the composition.

12. A curable and electrochemically detachable two-component (2K) adhesive composition as claimed in any of claims 1 to 3, comprising 0.5 to 10 wt.% of non-conductive particulate filler based on the weight of the composition.

13. A bonding structure comprising a first material layer having a conductive surface; a second material layer having a conductive surface; wherein a cured electrochemically detachable two-component (2K) adhesive composition as defined in any one of claims 1 to 12 is disposed between the first and second material layers.

14. A method for detaching the bonded structure as described in claim 13, the method comprising the steps of: 1) applying a voltage to two surfaces to form an anode interface and a cathode interface; and 2) detaching the surfaces, wherein the voltage applied in step 1 is from 0.5 to 200 V and is applied for from 1 second to 60 minutes.

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