Removable solvent-based pressure-sensitive adhesive (PSA)

Abstract

The present invention relates to a solvent-based, peelable pressure-sensitive adhesive composition comprising: a) a (meth)acrylate copolymer formed from monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof; b) an electrolyte selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium methanesulfonate, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, tributyl(ethyl)phosphonium diethylphosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a crosslinker; and d) a solvent.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to a solvent-based pressure-sensitive adhesive composition that can be peeled from the specific substrate to which it is applied. The present invention relates to a peelable solvent-based pressure-sensitive adhesive composition comprising: a) a (meth)acrylate copolymer; b) an electrolyte; c) a crosslinker; and d) a solvent. [Background technology]

[0002] Background of the Invention Adhesive bonds and polymer coatings are often used in the assembly and finishing of manufactured items. They replace mechanical fasteners such as screws, bolts, and rivets, reducing processing costs and providing joints that are more adaptable to the manufacturing process. Adhesive bonds distribute stress evenly, reducing the potential for fatigue and protecting the joint from corrosive agents.

[0003] Thus, while adhesive bonding offers many advantages over mechanical fasteners, adhesively bonded objects tend to be difficult to disassemble when adhesive bonding is required for practical applications. Removal of adhesives by mechanical processes such as sandblasting or wire brushing is often impossible because the adhesive is located between the substrates, making them inaccessible or difficult to polish without damaging the substrate surfaces. Disassembly through the use of chemicals or high temperatures may be effective, but can be time-consuming and complicated to implement. Furthermore, the harsh chemicals and / or harsh conditions required can damage the separating substrates, rendering them unsuitable for subsequent applications.

[0004] These problems have led some researchers to develop electrochemically releasable adhesive compositions in which the bond at the adhesive / substrate interface is broken when an electric current is passed through the dried or cured composition.

[0005] WO2007 / 142600 describes an electrochemically weakened adhesive composition that provides an adhesive bond to an electrically conductive surface and ionically conductive properties sufficient to weaken said adhesive bond upon application of a voltage to the adhesive composition, said composition comprising an amount of at least one ionic compound effective to impart said ionically conductive properties, said ionic compound having a melting point of 120°C or less.

[0006] US2007 / 0269659 describes an adhesive composition that is releasable at two interfaces, which (i) includes a polymer and an electrolyte, (ii) facilitates bonding of two surfaces, and (iii) forms an anodic interface and a cathodic interface in response to a voltage applied to both surfaces, and peels from both the anodic and cathodic surfaces.

[0007] US2008 / 0196828 describes a hot melt adhesive composition comprising a thermoplastic component and an electrolyte, which provides the composition with sufficient ionic conductivity to enable a faradaic reaction at the bond formed between the composition and a conductive surface, allowing the composition to be released from the surface.

[0008] U.S. Patent No. 7,465,492 describes an electrochemically strippable composition comprising a matrix functional group comprising a monomer selected from the group consisting of acrylic, methacrylic, and combinations thereof, a free radical initiator, and an electrolyte, the electrolyte providing the composition with sufficient ionic conductivity to support a Faradaic reaction in the bond formed between the composition and a conductive surface, thereby enabling the composition to be stripped from the surface. In this reference, the electrolyte comprises a salt capable of solvating in the composition, such as perchlorate, tetrafluoroborate, hexafluorophosphate, triflate, and triflimide anions of ammonium (NH4 + ), alkali metal, alkaline earth or rare earth salts.

[0009] EP3363875 provides an electrically peelable adhesive composition that forms an adhesive layer with high adhesive strength that can be easily peeled off by applying a voltage for a short time. The electrically peelable adhesive composition of the present invention contains a polymer and 0.5 to 30 wt % of an ionic liquid based on the weight of the polymer, and the anion of the ionic liquid is a bis(fluorosulfonyl)imide anion.

[0010] WO2017 / 133864 describes a method for reversibly bonding first and second substrates, where at least the first substrate is a non-conductive substrate, the method comprising the steps of: a) coating the surface of the non-conductive substrate with a conductive ink; b) applying an electrically releasable hot melt adhesive composition to the conductive ink-coated surface of the first substrate and / or the second substrate; c) contacting the first substrate with the second substrate, whereby the electrically releasable hot melt adhesive composition is interposed 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 to substantially weaken the adhesion at the interface between the electrically releasable hot melt adhesive composition and the substrate surfaces. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2007 / 142600 [Patent Document 2] US Patent Application Publication No. 2007 / 0269659 [Patent Document 3] US Patent Application Publication No. 2008 / 0196828 [Patent Document 4] U.S. Patent No. 7,465,492 [Patent Document 5] European Patent No. 3363875 [Patent Document 6] International Publication No. 2017 / 133864 Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, there is a need for a releasable solvent-based pressure-sensitive adhesive that provides high stability and high bond strength to metal and glass substrates while providing effective and clean release upon application of voltage. [Means for solving the problem]

[0013] Summary of the Invention The present invention relates to a peelable solvent-based pressure-sensitive adhesive composition comprising: a) a (meth)acrylate copolymer formed from monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof; b) an electrolyte selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium methanesulfonate, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, tributyl(ethyl)phosphonium diethylphosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a crosslinker; and d) a solvent.

[0014] The present invention also relates to dry films formed from the peelable solvent-based pressure-sensitive adhesive compositions according to the present invention.

[0015] The present invention encompasses the use of a peelable solvent-based pressure-sensitive adhesive composition or dry film according to the present invention in electronic devices.

[0016] The present invention further encompasses an adhesive construction comprising: a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface, wherein a releasable pressure-sensitive adhesive or dry film according to the present invention is disposed between the electrically conductive surfaces of the first and second substrates.

[0017] The present invention also relates to a method for peeling off the bonded structure of the present invention, which comprises: 1) applying a voltage to both surfaces to form an anode interface and a cathode interface, preferably applying a voltage of 0.5 to 200 V for 1 second to 60 minutes; and 2) peeling off the surfaces. [Brief explanation of the drawings]

[0018] [Figure 1] Figure 1 shows the bond structure. [Figure 2] Figure 2 shows the release structure. [Figure 3] Figure 3 shows the bond structure. [Figure 4] Figure 4 shows the release structure. [Figure 5] FIG. 5 shows the force required to separate aluminum foils bonded with the compositions of Examples 1 and 4. [Figure 6] FIG. 6 shows the force required to separate aluminum foils bonded with the compositions of Example 2 and Comparative Example 5. [Figure 7] FIG. 7 shows the force required to separate aluminum foils bonded with the compositions of Example 3 and Comparative Example 6. [Figure 8] FIG. 8 shows the force required to separate aluminum foil adhered with the composition of Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0019] Detailed Description of the Invention The present invention is described in further detail below. Each aspect described in this manner may be combined with other aspects unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0020] In the context of the present invention, the terms used shall be construed in accordance with the following definitions, unless the context dictates otherwise.

[0021] As used herein, the singular forms "a," "an," and "the" include both singular and plural referents unless the context clearly dictates otherwise.

[0022] As used herein, the terms "comprising," "including," and "included in" are synonymous with "including," "includes," or "containing," and "contains," and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps. When used, the phrase "consisting of" is closed-ended and excludes all additional elements. Furthermore, the phrase "consisting essentially of" excludes additional material elements but permits the inclusion of non-material elements that do not materially alter the nature of the invention.

[0023] The recitation of numerical endpoints includes not only the recited endpoint but also the whole number and fractions included in each range.

[0024] All percentages, parts, ratios, etc. referred to herein are by weight unless otherwise stated.

[0025] When an amount, concentration, or other value or parameter is expressed in the form of a range, a preferred range, or an upper preferred value and a lower preferred value, it should be understood that the range obtained by combining the upper or preferred value with the lower or preferred value is specifically disclosed, regardless of whether the resulting range is expressly stated in the context.

[0026] The terms "preferred," "preferably," "desirable," "particularly," and "especially" and their equivalents are frequently used herein to refer to embodiments of the present disclosure that may afford particular benefits, under particular circumstances. However, the recitation of one or more preferred, preferred, desirable, or particular embodiments does not imply that other embodiments are not useful, and is not intended to exclude such other embodiments from the scope of the disclosure.

[0027] The word "may" as used throughout this application is used in a permissive, i.e., possible, sense, rather than a required sense.

[0028] As used herein, the term "electrochemically releasable" means that, after the pressure-sensitive adhesive has cured, the adhesive strength can be weakened by at least 50% when a potential of 30 V is applied for 30 minutes. The pressure-sensitive adhesive is applied between two adhesively joined aluminum foils, allowing an electric current to flow through the adhesive bond line. The adhesive strength is measured by a peel adhesion test (180°) according to FTM-1 of the FINAT Technical Handbook, 9th Edition, with minor modifications, primarily a speed of 200 mm / min, an adhesive thickness of 30 μm, and a sample width of 25 mm.

[0029] As used herein, the term "clean peel" refers to the adhesive composition of the solvent-based pressure-sensitive adhesive being present only on the first substrate or the second substrate after peeling, meaning that there is substantially no adhesive present on either substrate. Here, the term "substantially no adhesive present" means that no more than 5% of the adhesive remains on the substrate after peeling, with visual inspection / assessment preferably less than 3%, more preferably less than 1%.

[0030] As used herein, the term "monomer" refers to a substance that can undergo a polymerization reaction to contribute a building block to the chemical structure of a polymer. As used herein, the term "monofunctional" refers to having one polymerizable moiety. As used herein, the term "multifunctional" refers to having more than one polymerizable moiety.

[0031] As used herein, "(meth)acryl" is an abbreviation for "acryl" and / or "methacryl." Thus, the term "(meth)acrylamide" collectively refers to acrylamide and methacrylamide.

[0032] As used herein, the term "pressure sensitive adhesive" or "PSA" refers to a type of adhesive that adheres to a surface and forms a bond when pressure is applied.

[0033] All references cited herein are incorporated by reference in their entirety.

[0034] 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 this invention belongs. For further guidance, definitions of terms are included to better understand the teachings of the present invention.

[0035] The present invention relates to a solvent-based, peelable pressure-sensitive adhesive composition comprising: a) a (meth)acrylate copolymer formed from monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof; b) an electrolyte selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium methanesulfonate, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, tributyl(ethyl)phosphonium diethylphosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a crosslinker; and d) a solvent.

[0036] The releasable solvent-based pressure-sensitive adhesive compositions of the present invention provide high stability and high bond strength to metal, particularly steel, and glass substrates, and allow for efficient and clean removal upon application of voltage.

[0037] The removable solvent-based pressure-sensitive adhesive composition according to the present invention comprises a (meth)acrylate copolymer formed from monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof.

[0038] These monomers are preferred because in combination they provide good adhesive strength and good bond strength to metal and glass substrates.

[0039] In one embodiment, the (meth)acrylate copolymer is formed from three or more monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof. In another embodiment, the (meth)acrylate copolymer is formed from four or more monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof.

[0040] By using three or more or four or more different monomers with different Tg's and / or functional groups, the adhesive strength and bond strength properties of the final (meth)acrylate copolymer can be fine-tuned.

[0041] Commercially available (meth)acrylate monomers suitable for use in the present invention include, but are not limited to, ethyl acrylate and 2-ethylhexyl acrylate from BASF, and 3-epoxypropyl methacrylate from ARPADIS.

[0042] The (meth)acrylate copolymer may be present in the peelable solvent-based pressure-sensitive adhesive composition according to the present invention in an amount of 23 to 55%, preferably 25 to 40%, more preferably 26 to 39%, based on the total weight of the composition.

[0043] Low amounts of (meth)acrylate copolymer can reduce adhesion and adversely affect film forming properties, while too high an amount can reduce processability.

[0044] The (meth)acrylate copolymer may be obtained by known polymerization methods, including solution polymerization in the presence of an organic solvent capable of dissolving the resulting copolymer; suspension polymerization; bulk polymerization; emulsion polymerization; and mini-emulsion polymerization. In the present invention, solution polymerization is preferred from the viewpoints of yield, productivity, and the performance of the coating film obtained from the copolymer. In any of these methods, the polymerization temperature is typically in the range of 30°C to 120°C. This temperature does not need to be maintained constant and may, for example, be increased during polymerization.

[0045] Polymerization is typically carried out using a free radical initiator, typically in an amount of 0.05 to 5% by weight based on the total weight of the monomers used. Suitable free radical initiators include hydrogen peroxide, alkyl hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; persulfates such as NH4 persulfate, K-persulfate, and Na-persulfate; organic peroxides such as acyl peroxides and benzoyl peroxide; dialkyl peroxides such as di-t-butyl peroxide; peroxide esters such as t-butyl perbenzoic acid initiators; and azo-functional hydrogen peroxides such as azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutanenitrile) (AMBN), and 4,4'-azobis(4-cyanovaleric acid).

[0046] The peroxy initiator compounds described above may be advantageously used in combination with a suitable reducing agent to form a redox system. Suitable reducing agents include sodium pyrosulfite, potassium pyrosulfite, sodium bisulfite, potassium bisulfite, acetone bisulfite, hydroxymethanesulfinic acid, and isoascorbic acid. Metal compounds such as Fe, EDTA, etc. may also be useful as part of the initiator's redox system.

[0047] Those skilled in the art will be able to select a suitable regimen for adding the initiator to the polymerization vessel during the course of the polymerization. It can be introduced completely into the polymerization vessel or can be used continuously or in stages depending on the consumption during the free radical polymerization. Preferably, a portion is charged initially and the remainder is fed depending on the consumption of the polymerization.

[0048] A chain transfer agent may also be present in the polymerization mixture, typically in an amount of 0.01 to 1% by weight, based on the total weight of the monomers used. Examples of chain transfer agents include mercaptans such as n-dodecyl mercaptan; thioglycolic acid esters such as octyl thioglycolic acid; α-methylstyrene dimer; and terpinolene.

[0049] The releasable solvent-based pressure-sensitive adhesive composition according to the present invention comprises an electrolyte, which comprises or consists of at least one salt according to formula (I) or formula (II). TIFF2025529288000001.tif3675

[0050] In the formula, R 1 ,R 2 ,R 3 ,R 4 and R 5 is hydrogen, C1-C 18 Alkyl, C3-C 18 Cycloralkyl, C6-C 18 Aryl, C7-C 24 Aralkyl, C2-C 20 Alkenyl, -C(O)R q , —C(O)OH, —CN, or —NO2; R q is C1-C6 alkyl; and X - is the counter anion.

[0051] The electrolyte is selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium methanesulfonate, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, tributyl(ethyl)phosphonium diethylphosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof. The above electrodes are preferred because they have good solubility in (meth)acrylate copolymers. Commercially available electrolytes suitable for use in the present invention include, but are not limited to, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM NTF) from Sigma Aldrich, Cyphos IL 109 and Cyphos IL 169 from Solvay, and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide from Iolitec.

[0052] The electrolyte may be present in the peelable, solvent-bonded pressure-sensitive adhesive composition of the present invention in an amount of 0.1 to 12%, preferably 0.4 to 11%, more preferably 0.5 to 11%, and even more preferably 0.75 to 10.75%, based on the total weight of the composition. These electrolyte amounts are preferred because, although a good release effect may be obtained when the electrolyte content exceeds 12%, initial adhesive properties may be adversely affected due to incomplete curing, while amounts below 0.1% may result in essentially no release effect.

[0053] The releasable solvent-based pressure-sensitive adhesive composition of the present invention includes a crosslinker. Preferably, the crosslinker is a metal chelate crosslinker. Suitable crosslinkers for use in the present invention should be stable at temperatures from -20°C to 100°C.

[0054] Crosslinking agents suitable for use in the present invention are preferably i) complexes of a metal selected from the group consisting of Al, Ti, Fe, Co, Ba, Zr, K and Zn; and ii) 1,3-dicarbonyl ligands providing organic compounds.

[0055] The metal is selected from the group consisting of Al, Ti, Fe, Co, Ba, Zr, K and Zn, preferably the metal is Al or Ti. As used herein, an organic compound that provides a 1,3-dicarbonyl ligand is a compound that has at least two carbonyl groups that can participate in chelation with a metal and that are arranged in a 1,3 spatial configuration relative to the carbon atom to which they are attached.

[0056] Exemplary metal chelates of this type include, but are not limited to, metal beta β-ketoesters, such as metal acetoacetates, such as metal ethylacetoacetates (ligand: ethyl acetoacetate); metal malonates, such as metal diethylmalonates; metal acetylacetonates (ligand: acetylacetone); metal formylacetonates (ligand: formylacetone); and metal formylacetophenonates (ligand: formylacetophenone).

[0057] Preferably, the cross-linking agent is selected from the group consisting of aluminum tris-2,4-pentanedionate, titanium diisopropoxide bis(acetylacetonate), and mixtures thereof.

[0058] These cross-linking agents are preferred because they have a positive effect on the final cohesion of the composition before a voltage is applied.

[0059] Commercially available cross-linking agents suitable for use in the present invention include, but are not limited to, aluminum tris-2,4-pentanedionate and titanium diisopropoxide bis(acetylacetonate) from Siccanor.

[0060] The crosslinker may be present in the peelable solvent-based pressure-sensitive adhesive composition of the present invention in an amount of 0.01 to 1.0%, preferably 0.02 to 0.75%, and more preferably 0.03 to 0.65%, based on the total weight of the composition. The amount of crosslinker affects the adhesive and cohesive properties of the composition. Too little crosslinker may result in the PSA being too soft and unable to hold both substrates together. On the other hand, too much crosslinker may result in the PSA being insufficiently flexible and unable to wet the surface and establish good contact.

[0061] The solvent-based peelable pressure-sensitive adhesive composition according to the present invention contains a solvent to reduce viscosity. Preferably, the solvent is a mixture of two or more solvents, more preferably a mixture of three or more solvents. Preferably, the solvent is selected from the group consisting of methyl acetate, ethyl acetate, isobutyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, pentanedione, hexane, heptane, toluene, acetone, and mixtures thereof.

[0062] These solvents are preferred because they maintain the viscosity of the PSA within a target range and aid in the formation of the (meth)acrylate copolymer.

[0063] In one embodiment, the solvent is a mixture of two or more solvents selected from the group consisting of methyl acetate, ethyl acetate, isobutyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, pentanedione, hexane, heptane, toluene, acetone, and mixtures thereof.

[0064] In another embodiment, the solvent is a mixture of three or more solvents selected from the group consisting of methyl acetate, ethyl acetate, isobutyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, pentanedione, hexane, heptane, toluene, acetone, and mixtures thereof.

[0065] Commercially available solvents suitable for use in the present invention include, but are not limited to, ethyl acetate from Eastman, isopropanol from Shell, and the like.

[0066] In the solvent-based peelable pressure-sensitive adhesive composition according to the present invention, the solvent may be present in an amount of 43 to 65%, preferably 44 to 62%, more preferably 45 to 60%, based on the total weight of the composition.

[0067] The solvent affects the viscosity of the composition and therefore its processability: too little solvent can result in a viscosity that is too high, which can cause processability problems, while too much solvent can result in a viscosity that is too low, which can adversely affect other properties.

[0068] Commercially available (meth)acrylate copolymers (including solvents and crosslinkers) suitable for use in the present invention include, but are not limited to, LOCTITE DURO-TAK 183A manufactured by Henkel; DURO-TAK 195A manufactured by Henkel; and DURO-TAK AH115 EU manufactured by Henkel.

[0069] The releasable solvent-based pressure-sensitive adhesive compositions of the present invention may further comprise a tackifier, which aids in balancing the adhesive and cohesive properties of the PSA by enhancing the releasability and tack of the PSA.

[0070] Preferably, the tackifier is selected from the group consisting of aliphatic petroleum hydrocarbon resins, alicyclic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins and their hydrogenated derivatives; polycyclopentadiene resins, hydrogenated polycyclopentadiene resins, aromatic-modified hydrogenated polycyclopentadiene resins, terpenes, aromatic terpenes, hydrogenated terpenes; polyterpenes, aromatic-modified polyterpenes and terpene phenols; copolymers of α-methylstyrene and vinyl aromatic monomers; gum rosin, gum rosin esters, wood rosin, wood rosin esters, tall oil rosin, tall oil rosin esters and hydrogenated rosin esters; and mixtures thereof, more preferably the tackifier is selected from the group consisting of glycerol esters of partially hydrogenated gum rosin, aliphatic C5 petroleum hydrocarbon resins, and mixtures thereof.

[0071] These tackifiers are suitable because they are compatible with the (meth)acrylate copolymer and provide ideal adhesion.

[0072] Commercially available tackifiers suitable for use in the present invention include, but are not limited to, Hydrogral G from DRT, and M-110 and M-120 hydrogenated C5 and / or C9 hydrocarbon feedstocks from Arakawa Chemical Industries.

[0073] The tackifier may be present in the peelable solvent-based pressure-sensitive adhesive composition according to the present invention in an amount of 5 to 15%, preferably 7 to 14%, more preferably 9 to 13%, based on the total weight of the composition.

[0074] This amount range has been found to be ideal for the compositions of the present invention, as less than 5% may result in insufficient adhesion, while too much (greater than 15%) may result in excessive adhesion and may adversely affect other properties of the composition.

[0075] The peelable solvent-based pressure-sensitive adhesive composition according to the present invention may further comprise a stabilizer, preferably 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythrityl tetrakis-3(3,5-di-tert-butyl-4-hydroxybenzyl)propionate, n-octadecyl-3(3,5-di-tert-butyl-4-hydroxybenzyl)propionate, 4,4'-methylenebis(2,6-tert-butylphenol), 4,4'-thiobis(6-tert-butyl-o-cresol) , 2,6-tert-butylphenol, 6-(4-hydroxyphenoxy)2,4-bis(n-octylthio)-1,3,5-triazine, di-n-octadecyl 3,5-ditert-butyl-4-hydroxybenzylphosphonate, 2-(n-octylthio)ethyl 3,5-ditert-butyl-4-hydroxybenzoate, and sorbitol hexa([3-(3,5-ditert-butyl-4-hydroxyphenyl)-propionate], and mixtures thereof.

[0076] The above stabilizers have been found to provide good protection for (meth)acrylate copolymers from thermal degradation.

[0077] Commercially available stabilizers suitable for use in the present invention include, but are not limited to, Irganox 1010 and Irganox B225 from BASF.

[0078] The stabilizer may be present in the peelable solvent-based pressure-sensitive adhesive composition according to the present invention in an amount of 0.05 to 0.25%, preferably 0.08 to 0.2%, based on the total weight of the composition. Amounts of stabilizer less than 0.05% may result in insufficient stabilizing properties, while amounts that are too high may adversely affect other properties of the composition.

[0079] The solvent-based pressure-sensitive adhesive compositions according to the present invention may, of course, also contain standard additives such as polar rubbers, pigments, fillers, plasticizers, leveling agents, foam suppressors, and rheology control agents. The selection of suitable additives is limited only by their compatibility with the other components of the composition and their not being detrimental to the use of the composition.

[0080] The present invention relates to dry films formed from the peelable solvent-based pressure-sensitive adhesive compositions according to the present invention.

[0081] The thickness of the dry film according to the present invention is preferably from 2 μm to 150 μm.

[0082] The dry film is obtained by applying the composition to a release liner such as silicone foil and then heating for 3 minutes at 110° C. The solvent evaporates during the heating process, leaving the dry film substantially solvent-free.

[0083] The term substantially solvent-free means that the dry film contains less than 1.5%, preferably less than 1.0%, more preferably less than 0.1%, and even more preferably less than 0.01% of solvent by total weight of the dry film. The present invention relates to the use of a peelable solvent-based pressure-sensitive adhesive composition or dry film according to the present invention in electronic devices.

[0084] Non-limiting examples of suitable electronic devices include smartphones, tablets, computers, other handheld devices, displays, and the like.

[0085] Non-limiting examples of potential applications include frame to housing (front glass to back glass) applications and battery removal applications.

[0086] The present invention relates to an adhesive structure comprising: a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface; wherein a peelable solvent-based pressure-sensitive adhesive composition or dry film according to the present invention is disposed between the electrically conductive surfaces of the first substrate and the second substrate.

[0087] When the peelable solvent-based pressure-sensitive adhesive composition is placed between the conductive surfaces of a first and second substrate, it is first placed on the conductive surface of the first substrate and dried at 110° C. for 3 minutes to obtain a dry pressure-sensitive adhesive film. The conductive surface of the second substrate is then placed on the dried pressure-sensitive adhesive film and pressure is applied to form an adhesive structure.

[0088] As shown in accompanying Figure 1, a bonded structure is provided in which a layer of a releasable solvent-based pressure-sensitive adhesive composition (10) is disposed between two electrically conductive substrates (11). Each layer of the electrically conductive substrate (11) is in electrical contact with a power source (13), which may be a battery or an AC-powered direct current (DC) power source. While the positive and negative terminals of the power source (13) are shown in one fixed position, those skilled in the art will understand that the polarity of the system can be reversed.

[0089] The two conductive substrates (11) are shown in the form of layers composed of, among others, metal films, metal sheets, metal meshes or grids, deposited metal particles, resin materials rendered conductive by the presence of conductive elements, or conductive oxide layers. Exemplary conductive elements include silver filaments, single-walled carbon nanotubes, and multi-walled carbon nanotubes. Examples of conductive oxides include doped indium oxides, such as indium tin oxide (ITO); doped zinc oxide; antimony tin oxide; cadmium stannate; and zinc stannate. Aside from the choice of conductive material, those skilled in the art will recognize that the effectiveness of the peeling operation may be reduced if the conductive substrate (11) is in the form of a grid or mesh that limits contact with the cured adhesive layer (10).

[0090] The present invention relates to a method for peeling off the bonded body (bonded structure) of the present invention, which includes the steps of: 1) applying a voltage to both surfaces to form an anode interface and a cathode interface, preferably applying a voltage of 0.5 to 200 V for 1 second to 60 minutes; and applying 200 V for 1 second to 60 minutes; and 2) peeling off the surfaces.

[0091] When a voltage is applied between the conductive substrates (11), a current is supplied to the peelable solvent-based pressure-sensitive adhesive composition (10) disposed therebetween. This induces an electrochemical reaction at the interface between the substrate (11) and the adhesive composition, which is believed to involve an oxidation reaction at the positively charged anodic interface and a reduction reaction at the negatively charged cathodic interface. This reaction is believed to weaken the adhesive bond with the substrate, allowing the peelable composition to be easily removed from the substrate.

[0092] As shown in Figure 2, delamination occurs at the positive electrode interface between the releasable solvent-based pressure-sensitive adhesive composition (10) and the conductive surface in electrical contact with the positive electrode (11). Reversing the direction of the current flow prior to separation of the substrates can weaken the adhesive bond at both interfaces of the substrates.

[0093] It should be noted, however, that the composition of the pressure-sensitive adhesive layer may be adjusted so that delamination occurs simultaneously from either the positive or negative interface, or from both. In some embodiments, when a voltage is applied to both surfaces to form an anodic and cathodic interface, delamination occurs simultaneously at both the anodic adhesive / substrate interface and the cathodic adhesive / substrate interface. In another embodiment, if the composition does not respond to direct current at both interfaces, reverse polarity can be used to simultaneously delaminate both the substrate and adhesive interfaces. The current can be applied in any suitable waveform, provided that the total time is sufficient for delamination to occur at each polarity. In this regard, sine waves, square waves, and triangular waves may be suitable and may be applied from a controlled voltage source or a controlled current source.

[0094] Without intending to limit the invention, it is believed that the peeling operation can be effectively performed when at least one, and preferably both, of the following conditions are met: a) an applied voltage of 0.5 to 200 V; and b) the voltage is applied for 1 second to 60 minutes. When detaching the conductive substrate from the pressure-sensitive adhesive is facilitated by applying force, for example, via a weight or spring, the potential may only need to be applied for a few seconds. In some embodiments, a potential of 5 V for 10 minutes can achieve peeling, while in some embodiments, a potential of 3.5 V for 30 minutes is sufficient.

[0095] After peeling, it is desirable that the pressure-sensitive adhesive composition be only on the first substrate or the second substrate, meaning that one of the substrates is substantially free of adhesive. [Example]

[0096] Example The following chemicals were used in the examples: Duro-Tak 195A manufactured by Henkel Duro-Tak AH115 manufactured by Henkel Duro-Tak 183 manufactured by Henkel 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM NTF) from Sigma Aldrich

[0097] Example 1 The composition was prepared according to 1.

[0098] TIFF2025529288000002.tif79163

[0099] The composition was prepared by mixing the above ingredients. The composition was applied to a release liner (silicone foil) and then heated at 110°C for 3 minutes to form a pressure-sensitive film. The resulting 120 μm-thick PSA film was transferred to an approximately 90 μm-thick aluminum foil (25 mm × 200 mm). A second piece of aluminum foil was pressed against the PSA film to form an adhesive structure (Figure 2). T-peel tests were performed according to ASTM D1876 using a separation speed of 200 mm / min on samples with an effective area of ​​2.5 cm × 20 cm; the results are shown in Table 2.

[0100] TIFF2025529288000003.tif49162

[0101] As shown in FIG. 4, the bonded structures of Examples 1, 2, and 3 peeled off after electrochemical peeling. Figures 5, 6, and 7 all show force measurements as the aluminum foils were pulled apart along the path in mm during the measurement, with the force required recorded in Newtons. Figure 5 shows the force required to pull apart the aluminum foils bonded together in Example 1 and Comparative Example 4. Figure 6 shows the force required to pull apart the aluminum foils bonded together in Example 2 and Comparative Example 5. Figure 7 shows the force required to pull apart the aluminum foils bonded together in Example 3 and Comparative Example 6.

[0102] Example 2 Different amounts of electrolyte were tested. The compositions were prepared according to Table 3.

[0103] TIFF2025529288000004.tif59141

[0104] The compositions were prepared by mixing the above ingredients. The compositions were coated onto a release liner (silicone foil) and then heated at 110°C for 3 minutes to form pressure-sensitive films. The resulting 120 μm-thick PSA film was transferred onto an approximately 80 μm-thick aluminum foil (25 mm × 200 mm). A second piece of aluminum foil was pressed onto the PSA film to form an adhesive structure (Figure 2). T-peel tests were performed according to ASTM D1876 at a separation rate of 200 mm / min on samples with an effective area of ​​2.5 cm × 20 cm. As shown in Figure 4, the adhesive structures of Examples 7 to 11 peeled off after electrochemical peeling. The results are shown in Table 4.

[0105] TIFF2025529288000005.tif43141

[0106] Example 3 The stability of PSA films formed from the composition of Example 7 was tested, and the results are shown in Table 7.

[0107] TIFF2025529288000006.tif97111

[0108] The 180° peel was measured according to FTM-1 of the FINAT Technical Handbook, 9th edition. The loop tack was measured according to DIN EN 1719.

[0109] Static shear was measured according to FTM-8 of the FINAT Technical Handbook, 9th edition.

[0110] The shear adhesive failure temperature (SAFT) was measured as follows: The thermal failure temperature of PSA compositions under shear was tested according to ASTM D4498 using an ES 07-II apparatus commercially available from Elastocon. Each adhesive component was cut into a 25 mm x 25 mm film and laminated to a standardized substrate using two passes of a 2 kg roller at a speed of 10 mm / s. A weight (1 kg) was attached to each component, and the temperature was increased from room temperature at a controlled rate (0.5 °C / min) until 200 °C was reached or the adhesive component failed.

[0111] FIG. 8 shows the force required to separate the aluminum foils bonded together in Example 7.

[0112] The test results demonstrate that pressure-sensitive adhesive tapes made from the compositions of the present invention have good stability.

Claims

1. a) a (meth)acrylate copolymer formed from monomers selected from the group consisting of ethyl (meth)acrylate, methyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-epoxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydrogenated polybutadiene (meth)acrylate, glacial acrylic acid, vinyl acetate, and mixtures thereof; b) an electrolyte selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-vinylimidazolium methanesulfonate, 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, tributyl(ethyl)phosphonium diethylphosphate, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide, and mixtures thereof; c) a cross-linking agent; and d) Solvent 1. A peelable solvent-based pressure-sensitive adhesive composition comprising:

2. 2. The peelable solvent-based pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylate copolymer is present in an amount of 23 to 55%, preferably 25 to 40%, more preferably 26 to 39%, based on the total weight of the composition.

3. 3. The peelable solvent-based pressure-sensitive adhesive composition of claim 1, wherein the electrolyte is present in an amount of 0.1 to 12%, preferably 0.4 to 11%, more preferably 0.5 to 11%, and even more preferably 0.75 to 10.75%, based on the total weight of the composition.

4. 4. The solvent-based peelable pressure-sensitive adhesive composition according to claim 1, wherein the crosslinking agent is a complex of a metal selected from the group consisting of Al, Ti, Fe, Co, Ba, Zr, K, and Zn with an organic compound providing 1,3-dicarbonyl ligands, and preferably the crosslinking agent is selected from the group consisting of aluminum tris-2,4-pentanedionate, titanium diisopropoxide bis(acetylacetonate), and mixtures thereof.

5. 5. The peelable solvent-based pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the crosslinker is present in an amount of 0.01 to 1.0%, preferably 0.02 to 0.75%, more preferably 0.03 to 0.65%, based on the total weight of the composition.

6. 6. The peelable solvent-based pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the solvent is a mixture of two or more solvents, preferably a mixture of three or more solvents, selected from the group consisting of methyl acetate, ethyl acetate, isobutyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, pentanedione, hexane, heptane, toluene, acetone, and mixtures thereof.

7. 7. The peelable solvent-based pressure-sensitive adhesive composition of claim 1, wherein the solvent is present in an amount of 43 to 65%, preferably 44 to 62%, more preferably 45 to 60%, based on the total weight of the composition.

8. 8. The peelable solvent-based pressure-sensitive adhesive composition according to any one of claims 1 to 7, further comprising a tackifier, preferably selected from the group consisting of aliphatic petroleum hydrocarbon resins, alicyclic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins and their hydrogenated derivatives, polycyclopentadiene resins, hydrogenated polycyclopentadiene resins, aromatic-modified hydrogenated polycyclopentadiene resins; terpenes, aromatic terpenes, hydrogenated terpenes; polyterpenes, aromatic-modified polyterpenes, and terpene phenols; copolymers of α-methylstyrene and vinyl aromatic monomers; and gum rosin, gum rosin esters, wood rosin, wood rosin esters, tall oil rosin, tall oil rosin esters, hydrogenated rosin esters, and mixtures thereof, more preferably the tackifier is selected from the group consisting of glycerol esters of partially hydrogenated gum rosin, aliphatic C5 petroleum hydrocarbon resins, and mixtures thereof.

9. 9. The peelable solvent-based pressure-sensitive adhesive composition of claim 8, wherein the tackifier is present in an amount of from 5 to 15%, more preferably from 7 to 14%, and even more preferably from 9 to 13%, based on the total weight of the composition.

10. Furthermore, stabilizers, preferably 1,3,5-trimethyl-2,4,6-tris(3,5-ditert-butyl-4-hydroxybenzyl)benzene, pentaerythrityl tetrakis-3(3,5-ditert-butyl-4-hydroxybenzyl)propionate, n-octadecyl-3(3,5-ditert-butyl-4-hydroxybenzyl)propionate, 4,4′-methylenebis(2,6-tert-butylphenol), 4,4′-thiobis-(6-tert-butyl-o-cresol), 2,6-tert-butylphenol, 10. The peelable solvent-based pressure-sensitive adhesive composition of any one of claims 1 to 9, comprising a stabilizer selected from the group consisting of 6-(4-hydroxyphenoxy)2,4-bis(n-octylthio)-1,3,5-triazine, di-n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2-(n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, and sorbitol hexa([3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate]), and mixtures thereof.

11. 11. The peelable solvent-based pressure-sensitive adhesive composition of claim 10, wherein the stabilizer is present in an amount of from 0.05 to 0.25%, more preferably from 0.08 to 0.2%, based on the total weight of the composition.

12. A dry film formed from the peelable solvent-based pressure-sensitive adhesive composition of any one of claims 1 to 11.

13. Use of the peelable solvent-based pressure-sensitive adhesive composition according to any one of claims 1 to 11 or the dry film according to claim 12 in electronic devices.

14. a) a first substrate having an electrically conductive surface; and b) a second substrate having an electrically conductive surface; 14. An adhesive structure comprising the peelable solvent-based pressure-sensitive adhesive composition of any one of claims 1 to 11 or the dry film of claim 12 disposed between electrically conductive surfaces of a first and a second substrate.

15. 15. A method for peeling a bonded structure according to claim 14, comprising the steps of: 1) applying a voltage to both surfaces to form an anodic interface and a cathodic interface, preferably between 0.5 and 200 V for 1 second to 60 minutes; and 2) peeling the surface A method comprising:

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