CURABLE ADHESIVE COMPOSITION FOR BONDING ONE OR MORE SUBSTRATES - Patent application

Abstract

A composition that cures upon exposure to actinic radiation. In some embodiments, the curable adhesive composition comprises: a) one or more radiation-curable oligomers or prepolymers containing at least one carbon-carbon double bond-terminated group; b) one or more diluent monomer components containing at least one polymerizable group; c) optionally, one or more organic or inorganic acid acrylic monomer adhesion-promoting additives; and, optionally, one or more rheology modifiers; one or more plasticizers; and one or more additives. The curable composition can be used in adhesives that structurally bond many substrates, including different substrates. In some embodiments, the cured reaction product of the composition has a wide usable temperature range, from -20 to 120°C. The cured reaction product of this embodiment exhibits greater than 50% cohesive failure over this temperature range. The cured composition maintains its adhesive strength even at temperatures above its Tg.

Description

[Technical Field] 【0001】 Field FIELD OF THE DISCLOSURE This disclosure relates generally to compositions that cure upon exposure to actinic radiation, such as ultraviolet (UV) radiation. [Background technology] 【0002】 Brief description of the related art Curable adhesive compositions find widespread application in bonding, particularly in the transportation and electronics industries, which bond many different substrates to form transportation components, such as aircraft, automobile, ship, train, and truck components, and electronic devices, such as computers, cell phones, tablets, etc. Of course, transportation components and electronic devices also include the subcomponents used in those components and devices. 【0003】 One of the most challenging applications of all adhesives is joining substrates with different coefficients of thermal expansion (CTE). Common examples include joining aluminum to glass, glass to plastic, ceramic to plastic, and rubber to metal. Furthermore, the challenging situation can be further complicated by stresses induced by extreme temperatures and thermal cycling during use. 【0004】 This localized material movement, or thermal stress, is concentrated at the bond line between the adhesive and the substrate, and it is important that the adhesive be flexible enough to withstand these movements associated with thermal cycling while still maintaining sufficient bond strength. 【0005】 Bonding dissimilar materials requires an adhesive to bond to multiple surface chemistries and, after curing, to withstand the stresses associated with various thermal expansion coefficients. To minimize stresses due to thermal distortion, it is desirable for the adhesive to be flexible while maintaining sufficient strength for structural durability. In practice, the flexibility of the adhesive can be controlled by the selection and concentration of prepolymers / oligomers, monomers, plasticizers, and filler amounts. 【0006】 The acrylic curable adhesive composition contains several additives that help control the properties in the uncured and cured states. 【0007】 Plasticizers are common ingredients in many adhesive compositions because they allow for easy adjustment of the workability of uncured adhesives and customization of the physical properties of cured adhesives. Plasticizers in cured adhesive compositions function by embedding themselves between polymer chains, increasing segmental mobility and creating a dilution effect within the polymer matrix. By reducing the rotational energy barrier within the polymer matrix, cured compositions benefit from increased flexibility. Modulus, glass transition temperature, tensile strength, and hardness all decrease, but elongation at break increases. Plasticizers add flexibility and softness to adhesives, but this flexibility is not necessarily permanent. Plasticizers tend to migrate from the material, resulting in brittleness. The structure and molecular weight of the plasticizer can be appropriately selected to mitigate plasticizer loss. 【0008】 Diluent monomers are commercially available with a variety of chemical structures and properties and can be used to tailor the bulk and adhesive properties of a composition. For example, using a low Tg and / or low modulus monomer increases flexibility, while using a high Tg monomer increases the stiffness or modulus of a curable adhesive composition. The intended effect can be controlled by varying the amount and combination of diluent monomers. While effective in controlling these properties, there are trade-offs. For example, increasing the concentration of flexibilizing monomers decreases other properties, such as high-temperature toughness and adhesive strength. This can make it difficult to balance the properties of adhesives using monomers to bond different substrates. Summary of the Invention [Problem to be solved by the invention] 【0009】 It remains a challenge to produce flexible adhesive compositions that maintain high bond strength over a wide temperature range for bonding dissimilar substrates. This specification discloses an unexpected method for enhancing flexibility and bond strength over a wide temperature range without using large amounts of plasticizers or other softening monomers in the curable composition. [Means for solving the problem] 【0010】 overview One embodiment of the present disclosure provides a curable adhesive composition comprising: a) one or more radiation-curable oligomers or prepolymers having at least one terminal carbon-carbon double bond-containing group; b) one or more diluent monomer components containing at least one polymerizable group; c) optionally, one or more adhesion promoting additives of organic acid or inorganic acid acrylic monomers; d) optionally, one or more rheology modifiers; e) optionally, one or more plasticizers; and f) optionally, additives such as one or more pigments, dyes, fillers, stabilizers, UV absorbers, antioxidants, processing oils, and the like. 【0011】 One embodiment of the present disclosure provides a curable adhesive composition having a wide operating temperature range of -20 to 120°C. The cured reaction product of this aspect exhibits greater than 50% cohesive failure over this temperature range. The cured composition maintains its adhesive strength even at temperatures above its Tg. 【0012】 One embodiment of the present disclosure provides a curable adhesive composition that structurally bonds dissimilar substrates, such as metal and plastic, particularly aluminum and polycarbonate, which have low surface energies. 【0013】 One embodiment of the present disclosure provides a highly flexible curable adhesive composition with a tensile modulus of less than 100 and an elongation at break of greater than 200% at 23° C. (ASTM D412). [Brief explanation of the drawings] 【0014】 [Figure 1] The results are for T-type peel adhesive strength (N / mm) (samples 7 to 11) tested at 23°C. [Figure 2] The results are for T-type peel adhesive strength (N / mm) (samples 7 to 11) tested at -20°C. [Figure 3] The results are for T-peel adhesive strength (N / mm) (samples 8, 9 and 12) tested at -20°C. [Figure 4] The graph shows the results of T-type peel adhesive strength (N / mm) (samples 7 to 11) tested at 120°C. [Figure 5] The graph shows the results of T-type peel adhesive strength (N / mm) (samples 7 to 11) after exposure to 85°C / 85% RH for 7 days. [Figure 6] These are the results of the T-type peel adhesion strength of iron (samples 13 to 19). [Figure 7] These are the results of aluminum T-type peel adhesion strength (samples 13 to 19). [Figure 8] These are the results of T-type peel adhesion strength of bright tin-plated cold-rolled steel (samples 13 to 19). [Figure 9] These are the results of T-type peel adhesion strength of copper (samples 13 to 19). DETAILED DESCRIPTION OF THE INVENTION 【0015】 Detailed Description The singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. 【0016】 As used herein, about or "approximately" in reference to a numerical value refers to ±10%, preferably ±5%, more preferably ±1% or less of the numerical value. 【0017】 As used herein, at least one means one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9, or more. When referring to components, the designation refers to the type of component, not the absolute number of molecules. Thus, "at least one polymer," for example, means at least one type of polymer, i.e., one type of polymer or a mixture of several different polymers may be used. 【0018】 As used herein, the terms "comprising," "comprises," and "comprised of" are synonymous with "including," "includes," "containing," or "contains," and are inclusive or open-ended and do not exclude additional, unrecited elements, components, or method steps. 【0019】 When an amount, concentration, dimension, or other parameter is expressed in the form of a range, preferred range, upper limit, lower limit, or preferred upper limit and limit, it should be understood that any range obtained by combining any upper limit or preferred value and any lower limit or preferred value is also considered to be specifically disclosed, regardless of whether the resulting range is expressly stated in the context. 【0020】 The terms "preferred" and "preferably" are frequently used herein to refer to embodiments of the disclosure that may offer certain benefits, under certain circumstances. However, the recitation of one or more "preferred" or "preferred" embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure. 【0021】 Molecular weights referred to herein refer to number average molecular weights (Mn) unless otherwise specified. Molecular weight data can be obtained by gel permeation chromatography (GPC) calibrated against polystyrene standards according to DIN 55672-1:2007-08 at 35°C unless otherwise specified. Weight average molecular weight Mw can be measured by GPC in the same way as Mn. "Polydispersity index" refers to a measure of the distribution of molecular weights within a polymer sample being measured. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn). 【0022】 As used herein, a curable one-component (1K) composition is a single formulation with sufficient commercial stability to be manufactured, stored, and shipped to the end user. A 1K composition can be used without the addition of additional components and will crosslink or cure when exposed to the appropriate conditions. As used herein, a two-component (2K) composition has two or more components. Each component is prepared, stored, and shipped separately from the others. The components are mixed immediately before use. Commercial storage after mixing is not possible because mixing of the components initiates the curing reaction. 【0023】 As used herein, the following definitions apply to the various aspects: 【0024】 Unless otherwise specified, (meth)acrylate refers to at least one of acrylate and methacrylate. A "vinyl group" refers to (CH2=CH-). A "(meth)acryloyl" refers to at least one of acryloyl and methacryloyl, an "acryloyl group" refers to (CH2=CHCO-), and a "methacryloyl group" refers to (CH2=C(CH3)CO-). 【0025】 Actinic radiation includes electron beams, ultraviolet light, visible light, and combinations thereof. Desirably, the wavelength of the actinic radiation used to cure the composition is about 200 nm to about 1,000 nm. Useful ultraviolet (UV) radiation includes, but is not limited to, UVA (about 320 nm to about 410 nm), UVB (about 290 nm to about 320 nm), UVC (about 220 nm to about 290 nm), and combinations thereof. Useful visible light includes, but is not limited to, blue light, green light, and combinations thereof. Such useful visible light has a wavelength of about 450 nm to about 550 nm. 【0026】 Unless otherwise specified, "acyl" refers to a group of the general formula --C(O)alkyl. 【0027】 Unless otherwise specified, "acyloxy" refers to a group of the general formula -O-acyl. 【0028】 Unless otherwise specified, "alcohol" refers to an alcohol of the general formula alkyl-OH. 【0029】 Unless otherwise specified, "alkenyl" or "lower alkenyl" refers to a straight, branched, or cyclic carbon chain having 1 to about 16, preferably 1 to about 6, carbon atoms and having at least one double bond between carbon atoms in the chain. Examples include, for example, ethylene, allene, butene, butadiene, hexene, hexadiene, 5,5-dimethyl-1-hexene, cyclohexene, and the like. Unless otherwise specifically limited, an alkenyl group can be unsubstituted, singly substituted, or multiply substituted with substituents at any position. 【0030】 Unless otherwise specified, "alkoxy" refers to the general formula --O-alkyl. 【0031】 Unless otherwise specified, "alkyl" refers to a straight-chain, branched, or cyclic alkyl group having 1 to about 9 carbon atoms, including, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, tert-butyl, cyclopropyl, cyclohexyl, cyclooctyl, vinyl, and allyl. Unless otherwise specifically limited, cyclic alkyl groups include monocyclic, bicyclic, and polycyclic rings, such as norbornyl, adamantyl, related terpenes, and the like. 【0032】 Unless otherwise specified, "alkylamino" refers to a group of the general formula -(NH)-alkyl. 【0033】 Unless otherwise specified, "dialkylamino" refers to a group of the general formula -N-(alkyl). Unless specifically limited otherwise, dialkylamino includes cyclic amine compounds such as piperidine and morpholine. 【0034】 Unless otherwise specified, "alkylmercapto" refers to a group of the general formula -S-alkyl. 【0035】 Unless otherwise specified, "alkynyl" or "lower alkynyl" refers to a straight, branched, or cyclic carbon chain having 1 to about 16, preferably 1 to about 6, carbon atoms and having at least one triple bond between carbon atoms within the chain. Examples include ethyne, butyne, hexyne, and the like. Unless otherwise specifically limited, an alkynyl group can be unsubstituted, singly substituted, or multiply substituted with substituents at any available position. 【0036】 Unless otherwise specified, an aromatic ring is an unsaturated ring structure having about 5 to about 6 carbon atom ring members and containing only carbon as ring atoms. Unless otherwise specified, an aromatic ring may be substituted or unsubstituted. 【0037】 Unless otherwise specified, "aryl" refers to a substituted or unsubstituted aromatic ring system containing only carbon ring atoms, for example, phenyl, biphenyl, naphthyl, and the like. 【0038】 Unless otherwise specified, "aroyl" refers to a group of the general formula --C(.dbd.O)-aryl. 【0039】 Unless otherwise specified, a carbocycle is a substituted or unsubstituted ring structure having from about 3 to about 8 ring members, containing only carbon as ring atoms, such as benzene and cyclohexane. 【0040】 The terms "halogen," "halo," or "hal," when used alone or as part of another group, mean chlorine, fluorine, bromine, or iodine. 【0041】 Unless otherwise specified, a heteroaromatic ring is a substituted or unsubstituted unsaturated ring structure having about 5 to about 8 ring members and containing carbon atoms and one or more heteroatoms, including nitrogen and / or sulfur, as ring atoms. A heteroaromatic ring (or group) also includes fused polycyclic ring systems in which one or more monocyclic aromatic rings or monocyclic heteroaromatic rings are fused to another heteroaromatic ring. Examples of heteroaromatic rings (or groups) include, but are not limited to, furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, pyrazole, imidazole, oxadiazole, triazole, tetrazole, pyridine, pyrimidine, pyrazine, purine, benzothiazole, benzimibazole, benzofuran, indole, quinoline, and quinoxaline. 【0042】 Unless otherwise specified, "heteroaryl" refers to an aromatic heterocycle. 【0043】 Unless otherwise specified, a heterocycle is a substituted or unsubstituted saturated ring structure having about 3 to about 8 ring members, with one or more heteroatoms, including carbon, nitrogen, and / or sulfur, as ring atoms. Examples of heterocycles include, but are not limited to, oxetane, thietane, azetidine, diazetidine, tetrahydrofuran, thiolane, pyrrolidine, dioxolane, oxathiolane, imidazolidine, dioxane, piperidine, morpholine, piperazine, and derivatives thereof. Unless otherwise specified, heterocycles include monocyclic, bicyclic, and polycyclic rings, such as azaadamantyl and tropanyl. 【0044】 Unless otherwise specified, the term "phenacyl" refers to the general formula -phenyl-acyl. 【0045】 Room temperature refers to a temperature of approximately 25°C. 【0046】 Unless otherwise specifically limited, the term "substituted" means substituted at any available position or positions with at least one of the substituents described below. Substituents for the above moieties useful in the disclosed compounds are groups that do not significantly reduce the biological activity of the disclosed compounds. Substituents that do not significantly decrease the biological activity of the disclosed compounds include, for example, H, halogen, N3, NCS, CN, NO2, NXIX2, OX3, C(X4)3, OAc, O-acyl, O-aroyl, NH-acyl, NH-aroyl, NHCOalkyl, CHO, C(halogen)3, COOX4, SO3H, PO3H2, SO2NXIX2, CONX1X2, C(O)CF3, alkyl, alcohol, alkoxy, alkylmercapto, alkylamino, dialkylamino, sulfonamido, or thioalkoxy, where X1 and X2 each independently comprise H or alkyl, or where X1 and X2 together comprise a heterocycle having from about 4 to about 7 ring members and, optionally, one additional heteroatom selected from O, N, or S, and where X1 and X2 together comprise from about 5 to about 6 members, and X4 comprises alkyl, lower alkylhydroxy, or alkyl-NXIX2. Unless otherwise specifically limited, a substituent can be present at any possible position, or at multiple possible positions if multiple-substituted. 【0047】 The term "aliphatic" means a saturated or unsaturated, straight-chain, branched or cyclic hydrocarbon group. 【0048】 The term "polymer" refers to a molecule in which a small number of repeating monomer units, such as 10 to 25,000 units, have been polymerized to form the molecule, and includes oligomers and prepolymers, which are subsets of the term polymer, typically having a smaller number of repeating monomer units and degree of polymerization. 【0049】 As used herein, "one or more" means at least one, including 1, 2, 3, 4, 5, 6, 7, 8, 9, or more of the referenced species. Similarly, "at least one" means one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9, or more. As used herein, "at least one" refers to the number of chemically distinct molecules, i.e., the number of different types of the referenced species, with respect to any component, but does not refer to the total number of molecules. For example, "at least one polyol" means that at least one type of molecule that fits the definition of polyol is used, but also means that two or more different polyol types that fit this definition can be present, but does not necessarily mean that only one type of polyol is present. 【0050】 The disclosed compounds include any and all isomers and stereoisomers. In general, unless expressly stated otherwise, the disclosed materials and processes may alternately be formulated to comprise, consist of, or consist essentially of the appropriate components, moieties, or steps disclosed herein. The disclosed materials and processes may additionally or alternatively be formulated to be devoid of, or substantially free of, any components, ingredients, components, adjuvants, moieties, species, and steps that are used in prior art compositions or that are not necessary to achieve the function and / or purpose of the present disclosure. 【0051】 Unless otherwise specified, all percentages quoted in connection with compositions described herein refer to weight percent (wt.%) of the final composition including all components. 【0052】 In one embodiment, the UV-curable adhesive composition comprises a (meth)acrylic prepolymer, a plasticizing adhesion-promoting monomer, an adhesion-promoting diluent monomer, a reactive monomer diluent, a photoinitiator, an optional filler, and optionally one or more additives. The UV-curable adhesive composition is preferably a one-component (1K) system, rather than a two-component (2K) system. 【0053】 (Meth)acrylic prepolymer Useful materials for use as the (meth)acrylic prepolymer include (meth)acrylic-functional siloxanes, polyacrylates, polyurethanes, polyethers, polyolefins, polyesters, copolymers thereof, and combinations thereof. In some embodiments, the (meth)acrylic prepolymer has at least two (meth)acryloyl functional groups, preferably pendant (meth)acryloyl functional groups. Desirably, the pendant (meth)acryloyl groups are -OC(O)C(R 1 )=CH2, where R 1 is hydrogen or methyl. 【0054】 Preferably, the (meth)acrylic prepolymer has the following structure: [ka] wherein each F moiety is a (meth)acryloyl pendant group, —OC(O)C(R 1 )=CH2, and R 1 is hydrogen or methyl] The (meth)acryloyl-terminated polyacrylate prepolymer has the formula: 【0055】 The (meth)acrylic prepolymer desirably has a molecular weight (Mn) of less than 100,000 g / mol, and in some embodiments, from about 3,000 to about 50,000 g / mol. Desirably, the (meth)acrylic prepolymer has a molecular weight greater than about 16,000 g / mol, which increases the elongation and flexibility of the cured reaction product of the adhesive composition. Furthermore, the (meth)acrylic prepolymer desirably has a viscosity at 25°C (77°F) of from about 2,000 Pas (200,000 cPs) to about 8,000 Pas (800,000 cPs), more desirably from about 4,500 Pas (450,000 cPs) to about 5,000 Pas (500,000 cPs). (Meth)acrylic prepolymers are commercially available from Kaneka Corporation of Japan under trade names such as RC220C, RC210C, RC200C, and RC100C. RC220C, RC210C, and RC200C are each believed to be terpolymers of combinations of substituted and unsubstituted alkyl acrylates such as ethyl acrylate, 2-methoxyethyl acrylate, and n-butyl acrylate (depending on molecular weight), while RC100C is a homopolymer of n-butyl acrylate. 【0056】 Plasticizing Adhesion Promoting Monomer The plasticizing adhesion-promoting monomer adds flexibility to the cured reaction product of the adhesive composition and also aids in bonding the cured reaction product of the adhesive composition to the substrate. The plasticizing adhesion-promoting monomer also covalently bonds to the polymer network of the cured composition. Useful plasticizing adhesion-promoting monomers include acrylic acid, methacrylic acid, and combinations thereof. Currently, no other materials known to the inventors can be used as the plasticizing adhesion-promoting monomer in this composition. The use of large amounts of plasticizing adhesion-promoting monomer products is undesirable because they adversely affect the modulus and moisture resistance of the cured product. 【0057】 Adhesion-Promoting Diluent Monomer The adhesion-promoting diluent monomer reduces the viscosity of the uncured adhesive composition and also aids in adhesion between the cured reaction product of the adhesive composition and the substrate. The plasticizing adhesion-promoting monomer also covalently bonds to the polymer network of the cured composition. N,N-dimethylacrylamide has proven useful as an adhesion-promoting diluent monomer. Currently, no other material known to the inventors can be used as an adhesion-promoting diluent monomer in this composition. 【0058】 Reactive Monomer Diluents The reactive monomer diluent adds flexibility to the cured reaction product of the adhesive composition. The reactive monomer diluent is covalently bonded to the polymer network of the cured composition. The reactive monomer diluent is not (meth)acrylic acid or dimethylacrylamide. Useful reactive monomer diluents include monomers having one or more reactive (meth)acrylate groups. Preferably, the reactive monomer diluent is a monofunctional (meth)acrylate, which increases the elongation of the cured reaction product of the composition. Useful monofunctional (meth)acrylates have the general structure CH═C(R)COOR 2 where R is a halogen such as H, CH, CH, or Cl, and R 2 is C 1-8 Mono- or bicycloalkyl, 3- to 8-membered heterocyclic radial with up to two oxygen atoms in the heterocyclic ring, molecular skeleton containing H, alkyl, hydroxyalkyl or aminoalkyl, where the alkyl moiety is C 1-20The alkyl (meth)acrylate monomers are linear, branched, or cyclic carbon atom chains. Particularly desirable monofunctional (meth)acrylate monomers corresponding to some of the above structures include hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, methyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, 2-aminopropyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Additionally, β-carboxyethyl acrylate (e.g., commercially available from Rhodia under the SIPOMER trademark) is also useful in the practice of the present invention. Two or more of the above monofunctional (meth)acrylates can also be used in combination. 【0059】 In some embodiments, it is useful for the reactive monomer diluent to have a high glass transition temperature (Tg) of 50° C. or greater and / or to be hydrophobic. 【0060】 Reactive monomer diluents with high Tg provide increased strength and improved modulus to the cured reaction product of the curable composition. 【0061】 The hydrophobic reactive monomer diluent provides the cured reaction product of the curable composition with improved bond strength durability and moisture resistance in the use environment. One indicator of the hydrophobicity of a reactive monomer diluent is a ratio of C atoms to O atoms in the molecular backbone of greater than 3:1, preferably greater than 4:1. 【0062】 Relationship between plasticizing adhesion-promoting monomers and adhesion-promoting diluent monomers The plasticizing adhesion promoting monomer is used in a weight ratio of 1 part plasticizing adhesion promoting monomer to 4 parts adhesion promoting diluent monomer to 20 parts plasticizing adhesion promoting monomer. The cured reaction product of an adhesive composition prepared using a plasticizing adhesion promoting monomer:adhesion promoting diluent monomer ratio outside these ranges may exhibit insufficient substrate bond strength, tensile modulus, and / or bond durability when exposed to humid environments. 【0063】 The relationship between plasticizing adhesion-promoting monomers and reactive monomer diluents. The adhesion-promoting diluent monomers are used in a weight ratio of 3 parts adhesion-promoting diluent monomer:2 parts reactive monomer diluent to 1 part adhesion-promoting diluent monomer:2 parts reactive monomer diluent. The cured reaction product of an adhesive composition prepared using an adhesion-promoting diluent monomer:reactive monomer diluent ratio outside these ranges may exhibit reduced substrate bond strength and / or bond durability when exposed to humid environments. 【0064】 Photoinitiator Photoinitiators speed up the curing process when the curable composition is exposed to actinic radiation. Desirably, the photoinitiator is added to the composition in an amount effective to respond to actinic radiation and initiate and induce curing of the composition. 【0065】 Suitable photoinitiators for ultraviolet (UV) curing monoolefin and polyolefin actinic radiation include free radical generating UV initiators such as substituted benzophenones and acetophenones, benzoin and its alkyl esters, xanthone and substituted xanthones. Photoinitiators include diethoxyacetophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, diethoxyxanthone, chlorothioxanthone, azobisisobutyronitrile, N-methyldiethanolamine benzophenone, and mixtures thereof. Specific examples of photoinitiators suitable for use in the present invention include those commercially available from Ciba Specialty Chemicals under the trade names "IRGACURE" and "DAROCUR," specifically IRGACURE 184 (1-hydroxycyclohexyl phenyl ketone), 907 (1-hydroxycyclohexyl phenyl ketone), and the like. (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one), 369 (2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone), 500 (1-hydroxycyclohexyl phenyl ketone and benzophenone), 651 (2,2-dimethoxy-2-phenylacetophenone), 1700 (bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl)phosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one), 819 [bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide], 2022 [IRGACURE 819 dissolved in DAROCUR 1173 (see below)], and DAROCUR Examples of suitable photoinitiators include, but are not limited to, 1173 (2-hydroxy-2-methyl-1-phenyl-1-propan-1-one) and 4265 (2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one); and visible light (blue) photoinitiators, dl-camphorquinone and IRGACURE 784DC. Of course, combinations of these materials can also be used in the present invention.Other photoinitiators useful in the present invention include alkylpyruvic acids such as methyl, ethyl, propyl, and butyl pyruvates, and arylpyruvic acids such as phenyl, benzyl, and their appropriately substituted derivatives. Photoinitiators particularly suitable for use in the present invention include ultraviolet photoinitiators such as 2,2-dimethoxy-2-phenylacetophenone (e.g., IRGACURE 651), 2-hydroxy-2-methyl-1-phenyl-1-propane (e.g., DAROCUR 1173), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g., IRGACURE 819 and IRGACURE 2022), and the ultraviolet / visible light initiator combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl)phosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one (e.g., IRGACURE 1700), as well as the visible light initiator bis(5-2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (e.g., IRGACURE 784DC). 【0066】 Some applications use LED devices to generate UV radiation to cure compositions. LED devices offer advantages over traditional mercury vapor technology, including lower operating temperatures and reduced energy usage. However, LED devices typically emit UV radiation above 395 nm. In some applications, these high UV radiation wavelengths, when used with traditional photoinitiators, can undesirably reduce the cure rate and level of cure of the composition. Type II photosensitizers, such as Esacure 1001 M, Esacure ONE, and ITX, have proven effective at curing compositions exposed to LED-generated radiation and are suitable for this application. 【0067】 additives The composition may optionally contain one or more additives. Additives useful in the composition include fillers, adhesion promoters such as organofunctional siloxane adhesion promoters, such as 3-aminopropyltrimethoxysilane and / or 3-methacryloxypropyltrimethoxysilane; thixotropes and rheology aids, such as hydrogenated castor oil, fatty acid amides, or swellable plastics, such as PVC; non-reactive diluents; non-reactive plasticizers, such as phthalic acid; acrylic polymers, functional (e.g., containing reactive moieties such as -OH and / or -COOH) acrylic polymers, non-functional acrylic polymers, acrylic block copolymers, tertiary alkyl amide functional groups, and the like. Reactive and non-reactive thermoplastic polymers containing styrene butadiene blocks, such as acrylic polymers, polysiloxane polymers, polystyrene copolymers, divinylbenzene copolymers, polyetheramides, polyvinyl acetals, polyvinyl butyral, polyvinyl chloride, methylene polyvinyl ether, cellulose acetate, styrene acrylonitrile, amorphous polyolefins, olefin block copolymers [OBC], polyolefin plastomers, thermoplastic urethanes, polyacrylonitrile, ethylene acrylate copolymers, ethylene acrylate terpolymers, ethylene butadiene copolymers and / or block copolymers, and Elvacite resins available from Mitsubishi Chemical America; antioxidants such as hindered amines and / or hindered phenols; alkoxysilane moisture scavengers such as vinyltrimethoxysilane; colorants and fluorescent dyes. 【0068】 Additional fillers include, for example, chalk, powdered limestone, precipitated and / or pyrogenic silica, zeolites, bentonite, carbonates such as calcium carbonate and magnesium carbonate, sulfates such as barium sulfate, diatomaceous earth, alumina, clay, titanium oxide, iron oxide, zinc oxide, sand, quartz, flint, mica, powdered glass, metal powders, other ground minerals, inorganic fillers such as silane-treated silica and (meth)acrylate-treated silica, organic materials such as carbon black, graphite, wood fiber, wood flour, sawdust, cellulose, cotton, pulp, wood chips, shredded straw, rice husks, crushed walnut shells and other short-cut organic fibers, short fibers such as glass fiber, glass filaments, polyacrylonitrile, carbon fiber, Kevlar fiber or polyethylene fiber, hollow spheres with mineral or plastic shells, Glass Bubbles®, Expancel®, or Dualite® materials, etc. Combinations of the above fillers may also be useful. 【0069】 In some embodiments, the curable composition has the following components and ranges, where the ranges are in weight percent based on the weight of the composition: TIFF2025526288000003.tif51150 【0070】 In some embodiments, the use of less than 10 wt.% adhesion-promoting diluent monomer weight relative to the curable composition results in reduced bond strength to some plastic substrates. In some embodiments, the use of 25 wt.% or more adhesion-promoting diluent monomer weight relative to the curable composition weight increases the tendency of the curable composition to be hygroscopic. 【0071】 The use of small amounts of plasticizing adhesion-promoting monomer in a curable composition can impart a high modulus and improved moisture resistance to the cured reaction product of the composition. However, using more than about 5 wt. % of plasticizing adhesion-promoting monomer based on the weight of the curable composition increases cost with little or no benefit. In some embodiments, the curable composition contains no more than 5 wt. % of plasticizing adhesion-promoting monomer based on the weight of the composition, preferably no more than 2 wt. %. 【0072】 The components are mixed uniformly to form a curable composition. Typically, mixing begins with the prepolymer and monomer, followed by the addition and mixing of additives, fillers, and photoinitiators. To avoid premature curing, the mixed composition must be packaged to exclude actinic radiation. The uncured composition may have a viscosity of 1 to 100 Pas. In some embodiments where the curable composition is extruded during application, a viscosity of about 5 to 50 Pas is more preferred. Naturally, the viscosity is adjusted to suit the application method and application. 【0073】 In use, the curable composition is placed on the surface of a first substrate, and a second substrate is placed on the first substrate at the surface that the applied adhesive contacts. One of the substrates is at least partially transparent to actinic radiation. Actinic radiation is applied through the radiation-transparent substrate to initiate a curing reaction in the curable composition. Preferably, the cured composition has an irreversible solid form that generally feels non-tacky to the touch. Preferably, the cured composition is not a pressure-sensitive adhesive. Once the composition cures, the first and second substrates are bonded. Typical substrates include any combination of ceramic, glass, polymer, and metal. The combination of different monomers makes the curable composition particularly useful for bonding polymeric substrates to non-polymeric substrates, such as metal substrates. 【0074】 In some embodiments, the combination and ratio of monomers and the plasticizing effect of the prepolymer enable the cured reaction product of the curable adhesive composition to retain bonding strength and flexibility over a wide temperature range (-20 to 120°C), making the curable composition suitable for bonding combinations of substrates with different expansion coefficients, such as polymers and metals. 【0075】 In some embodiments, the combination and ratio of monomers and prepolymers allow the cured reaction product to maintain flexibility and bond strength under a variety of humidity conditions. This makes the curable composition suitable for bonding substrates that are exposed to high temperatures and high relative humidity during use. Preferably, the cured composition maintains at least 60% of its normal cured strength after 1 week (7 days) of exposure to 85°C and 85% relative humidity. 【0076】 The following examples are given for illustrative purposes so that the present disclosure may be more readily understood, and are not intended to limit the scope of the disclosure unless specifically indicated otherwise. 【0077】 It should be understood that the procedural descriptions are illustrative and that variations and modifications may be employed without departing from the concept and spirit of the invention as defined in the following claims. 【0078】 Viscosity was tested at 25°C using a parallel plate rheometer or a cone and plate rheometer such as an Anton Paar MCR 302, using a 50 mm diameter cone or 25 mm diameter parallel plates. 【0079】 For the samples, a 1 mm thick spread adhesive layer was prepared between two substrates by spreading the adhesive on one substrate surface with 1 mm glass spacer beads and placing the surface of a second substrate on top of the spread adhesive. The applied adhesive was cured by irradiating it with UV light. After the samples were cured, they were tested. 【0080】 Ultraviolet (UV) curing is approximately 700mW / cm 2 The experiment was carried out using a UV-LED array (375 nm or 405 nm) with the above UV irradiation energy. 【0081】 After curing, some of the cured reaction products were kept in a chamber maintained at 85°C and 85% RH for 7 days (1 week). After this exposure, these samples were further tested. 【0082】 Peel strength is measured using a modification of ASTM D1876. A clear plastic substrate is bonded to a metal substrate with a 1 mm adhesive layer between the substrates. The adhesive is cured by irradiating an LED light source through the plastic substrate for 60 seconds. The light source is 700 mW / cm. 2 It emits light at approximately 405 nm. After curing, the free surface of the plastic substrate is bonded to a metal plate using a structural MMA adhesive such as Loctite AA H3500. Once the adhesive has cured, the metal plate and metal substrate are placed in a tensile tester and pulled at a rate of 50 mm / min. The peel strength is measured and the failure mode is also visually examined by estimating the total bond area where adhesive remains between the plastic and metal substrates. The failure mode is reported as the percentage of cohesive failure. 【0083】 The tensile strength at break, elongation at break, and tensile modulus are evaluated according to ASTM D412. 【0084】 Glass transition temperature (Tg) is determined using ASTM E1640-04 and is the peak tan δ measured using a TA Instruments DMA Q800. There may be multiple Tg peaks in the cured composition, but the relevant Tg is the Tg of the overall cured composition. This is designated Tg2. The addition of some plasticizing adhesion promoters to the composition will lower Tg2. This is called the Tg2 depression effect. 【0085】 Example 1: Prophetic compositions The adhesive composition may be prepared from a mixture of (meth)acrylic prepolymer (300-600 g), adhesion-promoting diluent monomer (100-250 g), reactive monomer diluent (100-250 g), plasticized adhesion-promoting monomer (1-50 g), optional reinforcing filler (20-150 g), and photoinitiator (2-10 grams). In some embodiments, one or more optional additives may be added to the composition, such as a preservative, an antioxidant such as a hindered phenol (0.5-5 g) or a hindered amine (1-50 g), a colorant, pigment, or fluorescent dye (0.01-1 g), or a non-bonding plasticizer such as a phthalate (1-100 g). 【0086】 The Prophetic Example 1 mixture is expected to be a 1k system that will be useful for bonding dissimilar substrates, such as polymers and metals. In one use, the mixture is placed in contact between the bonding surfaces of adjacent substrates and cured to bond the substrates. The Prophetic Example 1 material may be cured by exposure to actinic radiation, such as ultraviolet light, preferably ultraviolet radiation from an LED light source having a wavelength of about 390 nm or greater. The cured reaction product of the Prophetic Example 1 material is expected to have a flexible structure with plasticization by the high Tg reactive monomer diluent, which allows for cohesive failure at low temperatures while helping to maintain toughness at high temperatures. 【0087】 Example 2: Prepolymer type and its effect on physical properties Curable compositions were prepared using various prepolymer types, with and without plasticizing adhesion-promoting monomers. All amounts are expressed as weight percent based on the weight of the composition. Properties such as modulus at 23°C, modulus at 120°C, and glass transition temperature (Tg) were measured to compare the effectiveness of plasticization. The compositions and data are shown in the table below. 【0088】 [Table 1-1] 【0089】 [Table 1-2] 【0090】 Example 2 demonstrates the effect of using acrylic acid in the above composition to reduce the modulus and Tg of the reaction product. Six different prepolymers were used to compare the effect of prepolymers without acrylic acid (series a) and with acrylic acid (series b). In general, the effect is greater when polymer systems containing molecular weights of 16 kDa (Mn) or greater are used. 【0091】 Sample 1: When an aliphatic polyurethane is used as the prepolymer, the acrylic acid monomer decreases the modulus at 23°C, but increases the Tg as expected. 【0092】 Sample 2: Telechelic polybutadiene with a MW of 4450 Da does not show any softening effect. 【0093】 Sample 3: Telechelic polyacrylate with MW 13600 does not show any softening effect. 【0094】 Sample 4: Telechelic polyacrylate with MW 16700 does not show any softening effect. 【0095】 Sample 5: A telechelic polyacrylate with a MW of 25200 exhibits a surprising and unexpected softening effect when acrylic acid is added to the composition. The material softens below its Tg and hardens above its Tg. 【0096】 Sample 6: A telechelic polyacrylate with a MW of 32600 exhibits a surprising and unexpected softening effect when acrylic acid is added to the composition. The material softens below its Tg and hardens above its Tg. 【0097】 Example 3: Plasticization of (meth)acrylic prepolymers with different materials Curable compositions were prepared using the same (meth)acrylic prepolymer, a plasticizing adhesion-promoting monomer, and different candidate plasticizing materials. Example 3 compares the plasticizing effect of various materials incorporated into curable adhesive systems containing (meth)acrylic prepolymers ranging from 3 to 33 kDa. To evaluate the plasticizing effect, Tg, modulus, and peel behavior were tested. All amounts listed below are in grams. 【0098】 [Table 2] 【0099】 Sample 7 is a composition with no plasticizer added to establish a baseline. 【0100】 Sample 8 is a baseline composition that further includes acrylic acid as a plasticizing adhesion-promoting monomer. The results for Sample 8, compared to Sample 7, show that acrylic acid lowers the Tg of the cured composition, making the cured reaction product softer at temperatures below Tg and harder at temperatures above Tg. 【0101】 Sample 9 is a baseline composition that further includes 2-carboxyethyl acrylate (beta CEA) as a potential plasticizing adhesion-promoting monomer. Beta CEA is a carboxylic acid-containing monomer having a homopolymer with a Tg of approximately 15.4°C (measured by DSC). Beta CEA also lowered the Tg of the cured reaction product, which is expected for a monomer with a lower Tg than the baseline composition. What is surprising about Sample 9 is the powerful effect of beta CEA in lowering the Tg to a greater extent than would be expected if another low Tg monomer were used at the same loading (see Sample 11). 【0102】 Sample 10 is a baseline composition that further contains tricresyl phosphate as a known plasticizer. The cured reaction product of the composition of Sample 10 showed no change in Tg and little change in modulus. 【0103】 Sample 11 is a baseline composition further containing isooctyl acrylate. Isooctyl acrylate was chosen because it has a low homopolymer Tg of -54°C and is used in the art as a substitute for plasticizers to lower the Tg of adhesive compositions, e.g., by acting as a plasticizing monomer due to its low Tg. The cured reaction product of the composition of Sample 11 showed minimal change in Tg compared to the control, suggesting that isooctyl acrylate does not exhibit the unique and powerful Tg-depressing effect observed with acrylic acid or beta-CEA in Samples 8 and 9. 【0104】 The T-peel adhesion strength of the composition prepared in Example 3 was 0.8 W / cm when applied between a metal substrate and a UV-transmitting plastic substrate.2 The adhesive was tested on 1 mm of adhesive cured with 405 nm LED irradiation at 1000 kJ / min for 60 seconds. The following metal substrates were tested: single-side polished iron, grade RS-14 ("Iron"), obtained from Q-Lab; aluminum, 2024T3 bare grade AR-14 ("Aluminum"), obtained from Q-Lab; bright tin-plated cold rolled steel (CRS), 0.002 inch minimum plating ("Bright Tin-Plated Cold Rolled Steel"), obtained from ACT Test Panels LLC; and copper sheet C110 ("Copper"), obtained from Online Metals. The UV-transmitting plastic substrate used for bonding to the metal substrate was Sabic Lexan LS2-111 Polycarbonate, obtained from Standard Plaque Inc. Ambient temperature (23°C) T-peel adhesion data for the composition of Example 3 are reported below. All values are reported in N / mm. The results are also shown in Figure 1. 【0105】 [Table 3] 【0106】 At 23°C, Samples 8 and 9, which contain plasticizing adhesion-promoting monomers, exhibit the highest bond strengths. Sample 7, which contains no plasticizer components, exhibits similar bond strengths to steel and aluminum, but exhibits reduced bond strength between bright tin-plated cold-rolled steel and copper. Samples 10 and 11 demonstrate that the addition of other types of plasticizers, whether reactive or non-reactive, results in an overall decrease in bond strength at this test temperature. 【0107】 In addition to performance at room temperature (23°C), adhesives must be able to function over a wide temperature range that varies depending on the exposure conditions of the target application. To demonstrate the superior performance of compositions containing plasticizing adhesion-promoting monomers, T-peel adhesion tests were performed at -20°C and 120°C. 【0108】 [Table 4] The results are shown in Figure 2. 【0109】 When tested at -20°C, the plasticized adhesion promoting monomers of Samples 8 and 9 provide more than double the bond strength compared to the baseline and other plasticizer additives. 【0110】 To further emphasize the importance of the surprising plasticizing properties of (meth)acrylic acid and B-CEA, the T-peel adhesion is compared to Sample 12, which contains a baseline composition that further includes 2-hydroxyethyl methacrylate phosphate ester (HEMA phosphate). This is a common adhesion promoter in the art, but does not impart the surprising Tg lowering properties of (meth)acrylic acid or B-CEA. The overall modulus of the cured composition is lower than the baseline, but the Tg is higher. All amounts listed below are in grams. 【0111】 [Table 5] 【0112】 The T-peel adhesion of Sample 12 at -20°C is compared to Samples 8 and 9 and the results are shown in the table below. 【0113】 [Table 6] The results are also shown in Figure 3. 【0114】 At -20°C, Sample 12 is brittle and does not exhibit peel adhesion strength to iron or aluminum. Adhesion to tin-plated CRS and copper is reduced compared to Samples 8 and 9. Therefore, the surprising decrease in Tg observed in Samples 8 and 9 is a property that impacts low-temperature peel adhesion strength. 【0115】 At 120°C, the moduli of all compositions are roughly equivalent except for Sample 8, which contains acrylic acid monomers and is particularly surprising for its high base modulus at elevated temperatures, resulting in excellent bond strength. Sample 9 behaves as expected at this temperature. 【0116】 [Table 7] The results are shown in Figure 4. 【0117】 In addition to wide temperature performance, the cured composition of Sample 8 retains adhesive strength after 7 days of exposure to 85°C and 85% relative humidity (RH) compared to the baseline and a similar composition without (meth)acrylic acid. 【0118】 [Table 8] The results are also shown in FIG. 【0119】 Example 3 demonstrates that acrylic acid, utilized as a plasticizing adhesion-promoting monomer in a curable composition, has the unique and surprising ability to promote flexibility in the cured reaction product and maintain the adhesive strength of the cured composition over a wide temperature range. This is unexpected since acrylic acid has a Tg of about 106°C. Even more surprising is the ability of acrylic acid to impart these benefits even after the cured composition has been exposed to high temperature and humidity environments for extended periods of time. 【0120】 Example 4: Ratio of Adhesion Promoting Diluent Monomer to Reactive Monomer Diluent Curable compositions were prepared from the same (meth)acrylic prepolymer and acrylic acid with plasticized adhesion-promoting monomer, varying the ratio of adhesion-promoting diluent monomer to reactive monomer diluent while keeping the total monomer concentration constant. 【0121】 Cured T-peel adhesion specimens were prepared and tested with and without exposure to 85°C / 85% relative humidity for 7 days. The same substrate specimens as in Example 3 were used to prepare the specimens for Example 4. All quantities listed below are in grams. 【0122】 [Table 9] Adhesion strength values are reported in N / mm depending on the metal substrate. 【0123】 [Table 10] The results are also shown in Figure 6 (T-peel strength of iron), Figure 7 (T-peel strength of aluminum), Figure 8 (T-peel strength of bright tin-plated cold-rolled steel), and Figure 9 (T-peel strength of copper). 【0124】 For the metal substrates tested, the optimum ratio of adhesion-promoting diluent monomer to reactive monomer diluent is 1:1 to 2:1, preferably 3:2. If the concentration of adhesion-promoting diluent monomer deviates from this ratio, the cured reaction product exhibits reduced peel strength after one week of exposure at 85°C and 85% relative humidity.

Claims

[Claim 1] (Meth)acrylic prepolymer 10% to 99% by weight; Adhesion-promoting diluent monomer 1% to 50% by weight; Plasticizing adhesion promoting monomer 0.01% to 20% by weight; Reactive monomer diluent 0% to 50% by weight; Photoinitiators; and Optionally, one or more additives; A radiation-curable adhesive composition comprising, Here, the weight percentage is based on the weight of the adhesive composition, and the total is 100, a radiation-curable adhesive composition. [Claim 2] The composition according to claim 1, wherein the plasticizing adhesion promoting monomer is used in a weight ratio of plasticizing adhesion promoting monomer 1: adhesion promoting dilution monomer 4 to plasticizing adhesion promoting monomer 1: adhesion promoting dilution monomer 20. [Claim 3] The composition according to claim 1, wherein the adhesion-promoting diluent monomer is used in a weight ratio of adhesion-promoting diluent monomer 3:reactive monomer diluent 2 to adhesion-promoting diluent monomer 1:reactive monomer diluent 2. [Claim 4] The composition according to claim 1, wherein the adhesion-promoting diluent monomer is N,N-dimethylacrylamide. [Claim 5] The composition according to claim 1, wherein the plasticizing adhesion promoting monomer is (meth)acrylic acid. [Claim 6] The composition according to claim 1, wherein the monofunctional reactive monomer diluent is isobornyl acrylate. [Claim 7] (Meth)acrylic prepolymer 20% to 50% by weight; N,N-dimethylacrylamide 15% to 30% by weight as adhesion-promoting diluent monomer; As a plasticizing adhesion promoting monomer, 0.1% to 5% by weight of (meth)acrylic acid; and Monofunctional reactive monomer diluent 5% to 25% by weight The composition according to claim 1, comprising: [Claim 8] The composition according to claim 1, comprising at least 0.1% by weight of an additive. [Claim 9] A curing reaction product of a radiation-curable adhesive composition according to any one of claims 1 to 8. [Claim 10] An article comprising a radiation-curable adhesive composition extruded between a first substrate and a second substrate, Adhesive composition, (Meth)acrylic prepolymer 10% to 99% by weight; Adhesion-promoting diluent monomer 1% to 50% by weight; Plasticizing adhesion promoting monomer 0.01% to 20% by weight; Monofunctional reactive monomer diluent 0% to 50% by weight; and Photoinitiator; Includes, Here, the weight percentage is based on the weight of the adhesive composition, and the total is 100. [Claim 11] The article according to claim 10, wherein the plasticizing adhesion promoting monomer is used in a weight ratio of plasticizing adhesion promoting monomer 1: adhesion promoting dilution monomer 4 to plasticizing adhesion promoting monomer 1: adhesion promoting dilution monomer 20. [Claim 12] The article according to claim 10 or 11, wherein the adhesion-promoting diluent monomer is used in a weight ratio of adhesion-promoting diluent monomer 3:reactive monomer diluent 2 to adhesion-promoting diluent monomer 1:reactive monomer diluent 2. [Claim 13] The article according to claim 10 or 11, wherein the adhesion-promoting diluent monomer is N,N-dimethylacrylamide. [Claim 14] The article according to claim 10 or 11, wherein the plasticizing adhesion promoting monomer is (meth)acrylic acid. [Claim 15] The article according to claim 10 or 11, wherein the first base material is a polymer and the second base material is a metal. [Claim 16] The article according to claim 10 or 11, wherein the radiation-curable adhesive composition comprises at least one additive. [Claim 17] The article according to claim 10 or 11, wherein either the first substrate or the second substrate is transparent to chemical rays. [Claim 18] The article according to claim 10 or 11, which is a transport component or an electronic device. [Claim 19] The use of radiation-curable adhesive compositions for joining transport components or electronic devices, Composition: (Meth)acrylic prepolymer 10% to 99% by weight; Adhesion-promoting diluent monomer 1% to 50% by weight; Plasticizing adhesion promoting monomer 0.01% to 20% by weight; Reactive monomer diluent 0% to 50% by weight; Photoinitiator; and One or more additives of any choice; Includes, Here, the weight percentage is based on the weight of the adhesive composition, and the total is 10.

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