Radically polymerizable crosslinkers, curable compositions, and adhesives derived therefrom

Abstract

This invention discloses a free radical polymerizable crosslinking agent comprising a divalent segment Z represented by formula (I). Each divalent segment Z is directly bonded to i) two secondary N atoms, each of which is further directly bonded to a divalent segment Z or an X group; ii) two tertiary N atoms, each of which is further directly bonded to p additional divalent segments Z and (2-p) X groups, where p is 0, 1, or 2; or iii) a secondary N atom, which is further directly bonded to one additional divalent segment Z or an X group; and a tertiary N atom, which is further directly bonded to p additional divalent segments Z and (2-p) X groups. 1 This represents an alkyl subgroup having 1 to 4 carbon atoms, where n represents a positive integer. X is represented by formula (II): L represents a covalent bond, O, S, NR. 1 Or a divalent linker having 2 to 8 carbon atoms and at most 3 oxygen atoms. R 2 The X group is a radically polymerizable group selected from ethyleneoxy, allyloxy, methacryloxy, vinylaryl groups having 8 to 12 carbon atoms, and 2-propenylaryl groups having 9 to 13 carbon atoms. No two O, S, or N atoms in the X group are adjacent. The curable composition comprises a monofunctional radically polymerizable monomer, a radical initiator, and a radically polymerizable crosslinking agent. The present invention also discloses reaction products that are at least partially cured. (I)(II)

Description

Technical Field

[0001] This disclosure broadly relates to crosslinking agents, curable compositions, and adhesives that can be polymerized on free radicals. Background Technology

[0002] Adhesives are known to be used to bond one substrate to another, such as bonding metal to metal, metal to plastic, plastic to plastic, and glass to glass. Structural adhesives are an attractive alternative to mechanical joining methods such as riveting or spot welding because they distribute load stress over a larger area rather than concentrating it at a few points. Structural adhesives also produce cleaner and quieter products because they dampen vibrations and reduce noise. Furthermore, structural adhesives can be used to bond a variety of materials, sometimes without requiring extensive surface preparation. Summary of the Invention

[0003] In one aspect, this disclosure provides a crosslinking agent that is capable of free radical polymerization, comprising a divalent segment represented by the following formula:

[0004]

[0005] Each of the two-valent segments Z is directly bonded to:

[0006] i) Two secondary N atoms, each of which is further directly bonded to a divalent segment Z or X group.

[0007] ii) Two tertiary N atoms, each of which is further directly bonded to p additional divalent Z segments and (2-p) X groups, wherein p is 0, 1, or 2; or

[0008] iii) A secondary N atom, which is further directly bonded to: an additional divalent segment Z or X group; and a tertiary N atom, which is further directly bonded to p additional divalent segments Z and (2-p) X groups.

[0009] Each R 1 Independently representing alkyl subgroups having 1 to 4 carbon atoms,

[0010] Each n independently represents a positive integer, and

[0011] Each X group is independently represented by the following formula:

[0012]

[0013] Each L independently represents a covalent bond, O, S, NR. 1 Or having a divalent linker group with 2 to 8 carbon atoms and at most 3 oxygen atoms, and

[0014] Each R 2 Independently, it is a free radical polymerizable group selected from ethoxy, methacryloxy, allyloxy, vinylaryl having 8 to 12 carbon atoms, and 2-propenylaryl having 9 to 13 carbon atoms.

[0015] The prerequisite is that no two O, S, or N atoms in the X group are adjacent.

[0016] In another aspect, this disclosure provides a curable composition comprising:

[0017] At least one monofunctional monomer that can be polymerized by free radicals;

[0018] Free radical initiators; and

[0019] At least one free radical polymerizable crosslinking agent according to the present disclosure.

[0020] In another aspect, this disclosure provides an adhesive comprising at least partially cured reaction products of a curable composition according to this disclosure.

[0021] As used in this article:

[0022] The term "direct bond to" refers to bonding via a single covalent bond;

[0023] The term "radical polymerization" refers to radical homopolymerization and / or radical copolymerization (i.e., with different monomers / oligomers);

[0024] The term "(meth)acryl" refers to acryl (also known in the art as acryloyl and acrylyl) and / or methacryl (also known in the art as methacryloyl and methacrylyl);

[0025] The term "secondary nitrogen" refers to a neutral nitrogen atom covalently bonded to H and two carbon atoms;

[0026] The term "tertiary nitrogen" refers to a neutral nitrogen atom covalently bonded to three carbon atoms; and

[0027] The term "vinyl" and its equivalents do not include the CH2=CH- group within the acryloyl group.

[0028] The features and advantages of this disclosure will be further understood upon consideration of the specific embodiments and the appended claims. Detailed Implementation

[0029] While known structural adhesives can exhibit good high-temperature performance and durability, the rigid bond they produce after curing can lead to poor impact resistance and subsequent bond failure in the bonded components. Furthermore, adhesives with rigid bonds exhibit high and uneven stress distribution throughout the bond, with stress at the bond edges typically higher than in the middle. This high stress in rigid structural adhesives can cause undesirable deformation of the bonded material, known as bond penetration, which can be visually observed, especially when bonding large components such as automotive panels.

[0030] One method used in industry to improve the flexibility and toughness of structural adhesives is by incorporating elastomeric materials that can be dissolved or dispersed in the adhesive composition. Examples of such elastomeric materials include, for instance, methyl methacrylate-butadiene-styrene copolymers (“MBS”), acrylonitrile-styrene-butadiene copolymers, linear polyurethanes, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, butadiene rubber, and natural rubber. However, these elastomeric material additives can result in high viscosity in liquid adhesive compositions, which can lead to handling problems during use. Additionally, with respect to butadiene or other conjugated diene rubbers, elastomeric material additives can reduce the antioxidant resistance of structural adhesives, which can lead to bond failure.

[0031] This disclosure provides curable compositions that are substantially free of liquid rubber materials and also produce an adhesive structure exhibiting high adhesion (i.e., >1000 psi in a typical lap shear test) (>6.9 MPa), elongation (i.e., values ​​greater than 50%, 100%, or 400%), and impact resistance (i.e., >2 J) due to the inclusion of a novel crosslinking agent, even if the adhesive substrate (e.g., glass, ink-coated glass, metal, polymer) has not undergone surface treatment (e.g., corona, flame, abrasion) prior to bonding. The curable compositions in embodiments of this disclosure further offer the advantages of producing an adhesive structure exhibiting little to no adhesive layer permeability, providing adhesive compositions that exhibit tensile peeling or delamination at slightly elevated temperatures (e.g., less than 70°C), which allows for the reprocessing of parts bonded with these adhesives, and providing a sealant resistant to hydrolysis during heat / humidity aging.

[0032] According to this disclosure, the free radical polymerizable crosslinking agent can be crosslinked by a primary amine group on a polyamine precursor compound with a glycidyl group (i.e., It is prepared by nucleophilic addition of reactant compounds containing radically polymerizable groups that are less reactive with primary amines than glycidyl groups, and which are capable of undergoing free radical polymerization. Examples of such radically polymerizable groups include ethoxy groups (i.e., CH2=CHO-), allyloxy groups (i.e., CH2=CHCH2O-), vinylaryl groups, wherein the aryl group has 6 to 10 carbon atoms (e.g., vinylphenyl); methacryloyloxy, methacrylamide, N-alkylmethacryloyl, and 2-propenylaryl groups, wherein the aryl group has 6 to 10 carbon atoms (e.g., (2-propenyl)phenyl).

[0033] Suitable polyamine precursors may contain a divalent segment Z represented by the following formula:

[0034]

[0035] Each divalent segment Z is directly bonded to two N atoms, and each of the two N atoms is independently further directly bonded to p other divalent segments Z and (2-p) hydrogen atoms, where p is 0, 1 or 2.

[0036] Each R 1 Independently represents an alkylene group having 1 to 4 carbon atoms. Examples include methylene (i.e., -CH2-), ethylene (i.e., -CH2CH2-), propane-2-diyl, propane-1,3-diyl, butane-1,2-diyl, butane-1,3-diyl, and butane-1,4-diyl. Preferably, R 1 It is 1,4-butadiyl (i.e., -CH2CH2CH2CH2-).

[0037] Each n independently represents a positive integer; for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or greater. In a preferred embodiment, n is 1 to 5.

[0038] Suitable polyamine precursors can be obtained from 3M Company, St. Paul, Minnesota, such as DYNAMAR HC-1101, or prepared, for example, as described in U.S. Patent 3,436,359 (Hubin et al.), the disclosure of which is incorporated herein by reference.

[0039] Each R 1 Independently represents an alkylene group having 1 to 4 carbon atoms. Examples include methylene, ethylene, 1,2-propanediyl, 1,3-propanediyl, 1,4-butanediyl, 1,3-butanediyl, and 1,2-butanediyl. Preferably, R 1 It is 1,4-butadiyl (i.e., -CH2CH2CH2CH2-).

[0040] Each n independently represents a positive integer; for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or greater. In a preferred embodiment, n is 1 to 5.

[0041] Each X group is independently represented by the following formula:

[0042]

[0043] Each L independently represents a covalent bond, O, S, NR. 1 Or a divalent linker having 2 to 8 carbon atoms and up to 3 oxygen atoms, wherein each R1 independently represents an alkylene group having 1 to 4 carbon atoms. Examples of L include ethoxy, bis(ethoxy), tri(ethoxy), methyl, ethoxy, prop-1,3-diyl, but-1,4-diyl, hex-1,6-diyl, and oct-1,8-diyl.

[0044] Each R 2 Independently, it is a radically polymerizable group selected from ethoxy, methacryloxy, allyloxy, vinylaryl groups having 8 to 12 carbon atoms (e.g., 4-vinylphenyl, 3-vinylphenyl and 2-vinylphenyl) and 2-propenylaryl groups having 9 to 13 carbon atoms (e.g., 4-(2'-propenyl)phenyl, 3-(2'-propenyl)phenyl and 2-(2'-propenyl)phenyl).

[0045] L and R 2 It is selected such that no two O, S or N atoms in the X group are adjacent (i.e., no OO, OS, ON, NN, NS, SS, N=O or S=O bonds).

[0046] Exemplary suitable reactive compounds may include: glycidyl acrylate / glycidyl methacrylate monomers (e.g., (meth)acrylate); glycidyl vinyl ethers (e.g., glycidyl vinyl ether); glycidyl allyl ethers (e.g., glycidyl allyl ether); vinyl benzyl glycidyl ethers (e.g., 4-vinylbenzyl glycidyl ether, 3-vinylbenzyl glycidyl ether, 2-vinylbenzyl glycidyl ether); vinyl phenyl glycidyl ethers (e.g., 4-vinylphenyl glycidyl ether, 3-vinylphenyl glycidyl ether, 2-vinylphenyl glycidyl ether); (2-propenyl)phenyl glycidyl ethers (e.g., 4-(2-propenyl)phenyl glycidyl ether, 3-(2-propenyl)phenyl glycidyl ether, 2-(2-propenyl)phenyl glycidyl ether).

[0047] These compounds are available from commercial sources and / or prepared by known methods; for example, by the reaction of the corresponding alcohol with epichlorohydrin.

[0048] The X group in a free radical polymerizable crosslinking agent (i.e., The number of X groups will depend on the number of amine groups (especially primary amine groups) in the polyamine. For example, a free radical polymerizable crosslinker may have at least two and at least three, at least four, at least five or more X groups.

[0049] In some embodiments, the free radical polymerizable crosslinking agent has a number-average molecular weight of 4,000 to 54,000 g / mol, as measured relative to a polystyrene standard by gel permeation chromatography at 40°C according to ASTM method D3016-97 (2018). Specifically, the polymer can be analyzed by gel permeation chromatography (GPC) using a Reliant GPC (Waters e2695 pump / autosampler) equipped with a Waters 2424 evaporative light scattering detector and PL-Gel-2 columns; each 300 × 7.5 mm; one 3 μm Mixed-E (nominal MW range up to 30,000 Daltons) and one 5 μm Mixed-D (nominal MW range 200–400,000 Daltons).

[0050] Free radical polymerizable crosslinking agents can be used, for example, in curable compositions (e.g., curable structural adhesives). The curable compositions disclosed herein comprise at least one free radical polymerizable crosslinking agent as described above, at least one monofunctional free radical polymerizable monomer, and at least one free radical initiator. They can be prepared by simply mixing the various components using methods well known to those skilled in the art.

[0051] The curable compositions disclosed herein typically contain 2% to 60% by weight or 5% to 50% by weight of at least one free-radical polymerizable crosslinking agent according to the present disclosure. However, this is not required.

[0052] The curable compositions according to this disclosure further comprise at least one monofunctional free radical polymerizable monomer. Examples include monofunctional (meth)acrylate monomers (e.g., 2-phenoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate), acid-functional monomers (e.g., (meth)acrylate), alkoxylated (meth)acrylate lauryl acrylate, alkoxylated (meth)acrylate phenolic acrylate, alkoxylated (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate caprolactone, cyclotrimethylolpropane methyl acetal acrylate, ethylene glycol methyl ether (meth)acrylate, ethoxylated (meth)acrylate nonylphenol acrylate, (meth)acrylate isodecanyl acrylate, (meth)acrylate isooctyl acrylate, (meth)acrylate isooctyl acrylate, (meth)acrylate lauryl acrylate, (meth)acrylate octadecyl acrylate ((meth)acrylate stearyl acrylate), (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate tridecyl acrylate, (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate allyl acrylate Esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and 3-hydroxypropyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-ethoxypropyl methacrylate or 3-ethoxypropyl methacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, glycidyl methacrylate, phosphonate-functionalized (meth)acrylate monomers (e.g., derived from Solvay Specialty Polymers, USA). Specialty Polymers USA, LLC’s SIPOMER PAM resin or those obtained as MIRAMER SC1400 and MIRAMER SC1400A from Miwon North America (Exton, PA), Pennsylvania, N-(2-(2-oxo-1-imidazolyl)ethyl)-methacrylamide and SIPOMER WAM II from Solvay Specialty Polymers USA, LLC’s methacrylamide ethyl vinyl urea (“MAEEU”), and combinations thereof.

[0053] Specific examples of mono(meth)acrylate monomers that can be used in embodiments of this disclosure include isoborneol acrylate (acquired as SR506 from Sartomer, or as VISIOMER IBOMA from Evonik Performance Materials GmbH), isoborneol methacrylate (acquired as SR423A from Sartomer, or as VISIOMER IBOMA from Evonik Performance Materials GmbH), 2-phenoxyethyl methacrylate (acquired as SR340 from Sartomer), cyclohexyl methacrylate (acquired as VISIOMER c-HMA from Evonik Performance Materials GmbH), benzyl methacrylate (acquired as MIRAMER M1183 from Miwon North America, Exton, Pennsylvania), phenyl methacrylate (acquired as MIRAMER M1041 from Miwon North America), and allyl methacrylate (acquired as VISIOMER...). AMA (purchased from Evonik Performance Materials Co., Ltd.), 2-hydroxyethyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER HEMA 97 and HEMA 98), hydroxypropyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER HPMA 97 and HPMA 98), ultra-high purity 2-hydroxyethyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER UHP HEMA), methyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER MMA), methacrylic acid (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER GMAA), n-butyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER n-BMA), isobutyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER i-BMA), glyceryl methyl acetal methacrylate (purchased from VISIOMER...). GLYFOMA (purchased from Evonik Performance AG, Inc.), 2-(2-butoxyethoxy)ethyl methacrylate (purchased from Evonik Performance AG, Inc. under the name VISIOMER BDGMA), lauryl methacrylate (purchased from BASF, Florham Park, NJ under the name LMA 1214F), propylene glycol monomethacrylate (purchased from Amgen North America, Exton, Pennsylvania under the name MIRAMER M1051), and β-methacryloyloxyethyl hydrosuccinate (purchased from Shin-Nakamura Co., Ltd., Arimoto City, Japan under the name NKESTER SA).2-Isocyanate ethyl methacrylate (purchased from Showa Denko KK (Tokyo, Japan) by KarenzMOI), 2-(methacryloyloxy)ethyl phthalate (HEMA phthalate, purchased from ESSTECH, Inc., Essington, Pennsylvania by product number X-821-2000), 2-(methacryloyloxy)ethyl maleate (HEMA maleate, purchased from ESSTECH, Inc. by product number X-846-0000), methoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. by product number M-20G), methoxytriethylene glycol methyl methacrylate Acrylic ester (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-30G), methoxytetraethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-40G), methoxytripropylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-30PG), butoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under B-20G), phenoxyethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under PHE-1G), phenoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under PHE-2G), dicyclopentadienoxyethyl methacrylate (purchased under FANCRYL) FA-512M was purchased from Hitachi Chemical, Tokyo, Japan; dicyclopentyl methacrylate (FA-513M was purchased from Hitachi Chemical, Tokyo, Japan); isobornylcyclohexyl methacrylate (MM-304 was purchased from DesignMolecular Inc., San Diego, California); 4-methacryloyloxyethyl trimellitic anhydride (A-304 was purchased from DesignMolecular Inc.); 2-methacryloyloxyethyl phenylcarbamate (Polysciences, Inc., Warrington, Pennsylvania, Pennsylvania); and trifluoroethyl methacrylate (Hampford Research Inc., Stratford, Connecticut, USA).(Stratford, Connecticut), methacrylamide (acquired from Evonik Performance AG, Inc. at VISIOMERMAAmide), 2-dimethylaminoethyl methacrylate (acquired from Evonik Performance AG, Inc. at VISIOMERMADAME), 3-dimethylaminopropyl methacrylamide (acquired from Evonik Performance AG, Inc. at VISIOMERDMAPMA), and combinations thereof.

[0054] In some preferred embodiments, the at least one monofunctional free radical polymerizable monomer is selected from methyl methacrylate, 2-hydroxyethyl methacrylate, methacrylic acid, 2-(2-butoxyethoxy)ethyl methacrylate, glycerol formaldehyde methacrylate, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and combinations thereof.

[0055] In embodiments of this disclosure, the monofunctional monomer typically comprises 49% to 97% by weight of the curable composition; however, this is not required.

[0056] The curable composition according to this disclosure also contains at least one free radical initiator (i.e., an initiator for free radical polymerization).

[0057] In some implementations, the radical initiator is a redox initiator system because single-electron transfer redox reactions can be an efficient method for generating radicals under mild conditions. Redox initiator systems have been described, for example, in Progress in Polymer Science (1999), Vol. 24, pp. 1149–1204.

[0058] In some embodiments, the redox initiator system is a blend of a peroxide and an amine, wherein polymerization is initiated by the decomposition of the organic peroxide, which is activated by a redox reaction with an amine reducing agent. Typically, the peroxide is benzoyl peroxide, and the amine is a tertiary amine. Aromatic tertiary amines are the most efficient compounds for generating primary groups, among which N,N-dimethyl-4-toluidine (“DMT”) is the most common amine reducing agent.

[0059] In some embodiments, the redox curing initiator system comprises a barbituric acid derivative and a metal salt. In some embodiments, the barbituric acid / metal salt curing initiator system may also comprise an organic peroxide, an ammonium chloride salt (e.g., benzyltributylammonium chloride), or a mixture thereof.

[0060] Examples of free radical initiators based on barbituric acid include redox initiator systems having (i) a barbituric acid derivative and / or malonyl sulfonamide and (ii) an organic peroxide selected from monofunctional or polyfunctional carboxylic acid peroxide esters. Barbituric acid derivatives that can be used include, for example, 1,3,5-trimethylbarbituric acid, 1,3,5-triethylbarbituric acid, 1,3-dimethyl-5-ethylbarbituric acid, 1,5-dimethylbarbituric acid, 1-methyl-5-ethylbarbituric acid, 1-methyl-5-propylbarbituric acid, 5-ethylbarbituric acid, 5-propylbarbituric acid, 5-butylbarbituric acid, 1-benzyl-5-phenylbarbituric acid, 1-cyclohexyl-5-ethylbarbituric acid, and thiobarbituric acid, as mentioned in the published German patent application DE42 19 700 A1 (Imai et al.).

[0061] Barbiturates and barbiturates described in U.S. Patents 3,347,954 (Bredereck et al.) and 9,957,408 (Thompson), and malonyl sulfonamides disclosed in European Patent No. EP 0 059 451B1 (Schmitt et al.), can be used in embodiments of this disclosure. Preferred malonyl sulfonamides are 2,6-dimethyl-4-isobutylmalonyl sulfonamide, 2,6-diisobutyl-4-propylmalonyl sulfonamide, 2,6-dibutyl-4-propylmalonyl sulfonamide, 2,6-dimethyl-4-ethylmalonyl sulfonamide, or 2,6-dioctyl-4-isobutylmalonyl sulfonamide.

[0062] Barbiturate-based radical initiators typically comprise monofunctional or polyfunctional carboxylic acid peroxides as organic peroxides. Within the meaning of this disclosure, carbonate peroxides are also included in the category of polyfunctional carboxylic acid peroxides. Suitable examples include diisopropyl carbonate-peroxide diester, neodecanoic acid-tert-butyl-peroxide, neodecanoic acid-tert-amyl-peroxide, maleic acid-tert-butyl-monoperoxide, benzoic acid-tert-butyl-peroxide, 2-ethylhexanoic acid-tert-butyl-peroxide, 2-ethylhexanoic acid-tert-amyl-peroxide, monoisopropyl carbonate-monotert-butyl-peroxide, dicyclohexyl carbonate-peroxide, dimyristyl carbonate-peroxide, and carbonate... Diceryl peroxide, di(2-ethylhexyl)-peroxide, tert-butyl-peroxy-(2-ethylhexyl)-peroxide or 3,5,5-trimethylhexanoic acid-tert-butyl-peroxide, benzoic acid-tert-pentyl-peroxide, acetic acid-tert-butyl-peroxide, di(4-tert-butyl-cyclohexyl)-peroxide, neodecanoic acid-isopropylbenzene-peroxide, neopentanoic acid-tert-pentyl-peroxide and neopentanoic acid-tert-butyl-peroxide.

[0063] Specifically, according to embodiments of this disclosure, tert-butyl-peroxy-(2-ethylhexyl) carbonate (commercially available from Arkema, Inc., King of Prussia, PA, via LUPEROX TBEC) or tert-butyl-peroxide 3,5,5-trimethyl-hexanoic acid (commercially available from Arkema, Inc. via LUPEROX 270) can be used as organic peroxides.

[0064] Metal salts that can be used with barbituric acid derivatives may include transition metal complexes, particularly salts of cobalt, manganese, copper, and iron. When the metal salt is a copper compound, it may have the general formula CuXn, where X is an organic and / or inorganic anion, and n = 1 or 2. Examples of suitable copper salts include copper chloride, copper acetate, copper acetylacetonate, copper naphthenate, copper salicylate, or complexes of copper with thiourea or ethylenediaminetetraacetic acid, and mixtures thereof. In some embodiments, copper naphthenate is particularly preferred.

[0065] Another redox initiator system applicable to embodiments of this disclosure comprises an inorganic peroxide, an amine-based reducing agent, and a promoter, wherein the amine may be an aromatic and / or aliphatic amine, and the polymerization promoter is at least one selected from the group consisting of sodium benzenesulfinate, sodium p-toluenesulfinate, sodium 2,4,6-triisopropylbenzenesulfinate, sodium sulfite, potassium sulfite, calcium sulfite, ammonium sulfite, sodium bisulfate, and potassium bisulfate. Examples of inorganic peroxides that can be used in this system are persulfates, as described in U.S. Patent 8,545,225 (Takei et al.).

[0066] In some embodiments, the curable composition comprises a free radical initiator comprising a metal salt (e.g., copper naphthenate) and an ammonium salt (e.g., benzyltributylammonium chloride). In some embodiments, the curable composition comprises a curing initiator system comprising a barbituric acid derivative and a metal salt, and optionally comprising at least one of an organic peroxide and an ammonium chloride salt.

[0067] The curable composition may contain at least one photoinitiator, alone or in combination with other free radical initiators, which is activated by light (typically ultraviolet (UV) lamps), but other light sources such as LED lamps, xenon flash lamps and lasers may also be used if the photoinitiator is appropriately selected.

[0068] Available photoinitiators include those known to be usable for photocuring free radical polyfunctional (meth)acrylates. Exemplary photoinitiators include benzoin and its derivatives, such as α-methyl benzoin; α-phenylbenzoin; α-allyl benzoin; α-benzyl benzoin; benzoin ethers, such as benzoin dimethyl ketal (e.g., purchased as OMNIRAD BDK from IGM Resins USA Inc., St. Charles, Illinois), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives, such as 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., purchased as OMNIRAD 1173 from IGM Resins USA Inc.) and 1-hydroxycyclohexylphenyl ketone (e.g., purchased as OMNIRAD 184 from IGM Resins USA Inc.); 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone (e.g., purchased as OMNIRAD BDK from IGM Resins USA Inc.) 907 (purchased from IGM Resins, USA); 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholino)phenyl]-1-butanone (e.g., purchased from IGM Resins, USA as OMNIRAD 369); and triarylphosphine and phosphine oxide derivatives, such as ethyl 2,4,6-trimethylbenzoylphenylphosphonate (e.g., purchased from IGM Resins, USA as TPO-L) and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (e.g., purchased from IGM Resins, USA as OMNIRAD 819).

[0069] Other available photoinitiators include, for example, pivaloin ether, anethole ether, anthraquinones (e.g., anthraquinone, 2-ethylanthraquinone, 1-chloroanthraquinone, 1,4-dimethylanthraquinone, 1-methoxyanthraquinone, or benzoanthraquinone), halomethyltriazines, benzophenone and its derivatives, iodonium and sulfonium salts, titanium complexes such as bis(n5-2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrolo-1-yl)phenyl]titanium (e.g., available under the trade name CGI 784DC from BASF, Florem Park, NJ); halomethyl-nitrobenzene (e.g., 4-bromomethylnitrobenzene), and combinations of photoinitiators in which one component is monoacylphosphine oxide or diacylphosphine oxide (e.g., available under the trade names IRGACURE 1700, IRGACURE 1800, and IRGACURE). Purchased in 1850 from BASF, Florem Park, New Jersey, and in OMNIRAD 4265 from IGM Resins USA.

[0070] Free radical initiators can also be thermally activated free radical initiators, such as azo initiators (e.g., azobisisobutyronitrile) or peroxides (e.g., benzoyl peroxide).

[0071] The free radical initiator is present in the curable composition in an amount sufficient to allow the curable composition to have a adequate rate of curing free radical reaction when polymerization is initiated; these amounts can be readily determined by those skilled in the art. In embodiments of this disclosure, the free radical initiator is typically present in the curable composition at a level of 0.1 to 10% by weight, more typically 0.5 to 5% by weight, of the curable free radical polymerization component; however, this is not required.

[0072] In some embodiments, the curable composition comprises, based on the total weight of the curable composition, 49% to 97% by weight of at least one monofunctional free radical polymerizable monomer, 0.1% to 10% by weight of at least one free radical initiator, and 2.9% to 50.9% by weight of at least one free radical polymerizable crosslinking agent.

[0073] The curable composition may also contain other compounds having two or more free radical polymerizable groups (e.g., hexanediol diacrylate or trimethylolpropane triacrylate); however, this is generally not preferred.

[0074] The curable composition may optionally contain one or more conventional additives. Additives may include, for example, tackifiers, plasticizers, dyes, pigments, antioxidants, UV stabilizers, corrosion inhibitors, dispersants, wetting agents, adhesion promoters, and fillers.

[0075] The fillers that can be used in the embodiments of this disclosure include, for example, fillers selected from: microfibrillated polyethylene, pyrolytic silica, talc, wollastonite, aluminosilicate clay (e.g., hydrous kaolin), phlogopite, calcium carbonate, kaolin, metal oxides (e.g., barium oxide, calcium oxide, magnesium oxide, zirconium oxide, titanium oxide, zinc oxide), nanoparticle fillers (e.g., nano silica, nano zirconium oxide), and combinations thereof.

[0076] Curable compositions may be provided as single- or two-part compositions, depending, for example, on the free radical initiator selected.

[0077] The curable compositions according to this disclosure can be at least partially cured by exposure to photochemical electromagnetic radiation (e.g., ultraviolet and / or visible light), thermal energy (e.g., in an oven, infrared radiation, or thermal conduction), by exposure to oxygen, by combining two portions of a two-part composition, or any combination thereof.

[0078] After at least partial curing, a crosslinked composition is typically obtained, and if fully cured, it can be suitable as a structural adhesive for bonding two adherends. In this application, the curable composition is typically sandwiched between the adherends and at least partially cured, for example, to the point where at least the desired level of bond strength is achieved.

[0079] The purposes and advantages of this disclosure are further illustrated by the following non-limiting embodiments, but the specific materials and quantities referenced in these embodiments, as well as other conditions and details, should not be construed as undue limitation of this disclosure.

[0080] Free radical polymerizable crosslinking agents can be used, for example, in curable compositions (e.g., curable structural adhesives). The curable compositions disclosed herein comprise at least one free radical polymerizable crosslinking agent as described above, at least one monofunctional free radical polymerizable monomer, and at least one free radical initiator. They can be prepared by simply mixing the various components using methods well known to those skilled in the art.

[0081] The curable compositions disclosed herein typically contain 2% to 60% by weight or 5% to 50% by weight of at least one free-radical polymerizable crosslinking agent according to the present disclosure. However, this is not required.

[0082] The curable compositions according to this disclosure further comprise at least one monofunctional free radical polymerizable monomer. Examples include monofunctional (meth)acrylate monomers (e.g., 2-phenoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate), acid-functional monomers (e.g., (meth)acrylate), alkoxylated (meth)acrylate lauryl acrylate, alkoxylated (meth)acrylate phenolic acrylate, alkoxylated (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate caprolactone, cyclotrimethylolpropane methyl acetal acrylate, ethylene glycol methyl ether (meth)acrylate, ethoxylated (meth)acrylate nonylphenol acrylate, (meth)acrylate isodecanyl acrylate, (meth)acrylate isooctyl acrylate, (meth)acrylate isooctyl acrylate, (meth)acrylate lauryl acrylate, (meth)acrylate octadecyl acrylate ((meth)acrylate stearyl acrylate), (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate tridecyl acrylate, (meth)acrylate tetrahydrofurfuryl acrylate, (meth)acrylate allyl acrylate Esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and 3-hydroxypropyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-ethoxypropyl methacrylate or 3-ethoxypropyl methacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, glycidyl methacrylate, phosphonate-functionalized (meth)acrylate monomers (e.g., derived from Solvay Specialty Polymers, USA). Specialty Polymers USA, LLC’s SIPOMER PAM resin or those obtained as MIRAMER SC1400 and MIRAMER SC1400A from Miwon North America (Exton, PA), Pennsylvania, N-(2-(2-oxo-1-imidazolyl)ethyl)-methacrylamide and SIPOMER WAM II from Solvay Specialty Polymers USA, LLC’s methacrylamide ethyl vinyl urea (“MAEEU”), and combinations thereof.

[0083] Specific examples of mono(meth)acrylate monomers that can be used in embodiments of this disclosure include isoborneol acrylate (acquired as SR506 from Sartomer, or as VISIOMER IBOMA from Evonik Performance Materials GmbH), isoborneol methacrylate (acquired as SR423A from Sartomer, or as VISIOMER IBOMA from Evonik Performance Materials GmbH), 2-phenoxyethyl methacrylate (acquired as SR340 from Sartomer), cyclohexyl methacrylate (acquired as VISIOMER c-HMA from Evonik Performance Materials GmbH), benzyl methacrylate (acquired as MIRAMER M1183 from Miwon North America, Exton, Pennsylvania), phenyl methacrylate (acquired as MIRAMER M1041 from Miwon North America), and allyl methacrylate (acquired as VISIOMER...). AMA (purchased from Evonik Performance Materials Co., Ltd.), 2-hydroxyethyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER HEMA 97 and HEMA 98), hydroxypropyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER HPMA 97 and HPMA 98), ultra-high purity 2-hydroxyethyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER UHP HEMA), methyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER MMA), methacrylic acid (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER GMAA), n-butyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER n-BMA), isobutyl methacrylate (purchased from Evonik Performance Materials Co., Ltd. as VISIOMER i-BMA), glyceryl methyl acetal methacrylate (purchased from VISIOMER...). GLYFOMA (purchased from Evonik Performance AG, Inc.), 2-(2-butoxyethoxy)ethyl methacrylate (purchased from Evonik Performance AG, Inc. under the name VISIOMER BDGMA), lauryl methacrylate (purchased from BASF, Florlem Park, NJ under the name LMA 1214F), propylene glycol monomethacrylate (purchased from Amgen North America, Exton, Pennsylvania under the name MIRAMER M1051), and β-methacryloyloxyethyl hydrosuccinate (purchased from Shin-Nakamura Co., Ltd., Arihon City, Japan under the name NK ESTER SA).2-Isocyanate ethyl methacrylate (purchased from Showa Denko KK (Tokyo, Japan) by KarenzMOI), 2-(methacryloyloxy)ethyl phthalate (HEMA phthalate, purchased from ESSTECH, Inc., Essington, Pennsylvania by product number X-821-2000), 2-(methacryloyloxy)ethyl maleate (HEMA maleate, purchased from ESSTECH, Inc. by product number X-846-0000), methoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. by product number M-20G), methoxytriethylene glycol methyl methacrylate Acrylic ester (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-30G), methoxytetraethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-40G), methoxytripropylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under M-30PG), butoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under B-20G), phenoxyethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under PHE-1G), phenoxydiethylene glycol methacrylate (purchased from Shin-Nakamura Chemical Industry Co., Ltd. under PHE-2G), dicyclopentadienoxyethyl methacrylate (purchased under FANCRYL) FA-512M was purchased from Hitachi Chemical, Tokyo, Japan; dicyclopentyl methacrylate (FA-513M was purchased from Hitachi Chemical, Tokyo, Japan); isobornylcyclohexyl methacrylate (MM-304 was purchased from Design Molecular Inc., San Diego, California); 4-methacryloyloxyethyl trimellitic anhydride (A-304 was purchased from Design Molecular Inc.); 2-methacryloyloxyethyl phenylcarbamate (Polysciences, Inc., Warrington, Pennsylvania, Pennsylvania); and trifluoroethyl methacrylate (Hampford Research Inc., Stratford, Connecticut, USA).(Stratford, Connecticut), methacrylamide (acquired from Evonik Performance AG under the name VISIOMER MAAmide), 2-dimethylaminoethyl methacrylate (acquired from Evonik Performance AG under the name VISIOMER MADAME), 3-dimethylaminopropyl methacrylamide (acquired from Evonik Performance AG under the name VISIOMER DMAPMA), and combinations thereof.

[0084] In some preferred embodiments, the at least one monofunctional free radical polymerizable monomer is selected from methyl methacrylate, 2-hydroxyethyl methacrylate, methacrylic acid, 2-(2-butoxyethoxy)ethyl methacrylate, glycerol formaldehyde methacrylate, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and combinations thereof.

[0085] In embodiments of this disclosure, the monofunctional monomer typically comprises 49% to 97% by weight of the curable composition; however, this is not required.

[0086] The curable composition according to this disclosure also contains at least one free radical initiator (i.e., an initiator for free radical polymerization).

[0087] In some implementations, the radical initiator is a redox initiator system because single-electron transfer redox reactions can be an efficient method for generating radicals under mild conditions. Redox initiator systems have been described, for example, in Progress in Polymer Science (1999), Vol. 24, pp. 1149–1204.

[0088] In some embodiments, the redox initiator system is a blend of a peroxide and an amine, wherein polymerization is initiated by the decomposition of the organic peroxide, which is activated by a redox reaction with an amine reducing agent. Typically, the peroxide is benzoyl peroxide, and the amine is a tertiary amine. Aromatic tertiary amines are the most efficient compounds for generating primary groups, among which N,N-dimethyl-4-toluidine (“DMT”) is the most common amine reducing agent.

[0089] In some embodiments, the redox curing initiator system comprises a barbituric acid derivative and a metal salt. In some embodiments, the barbituric acid / metal salt curing initiator system may also comprise an organic peroxide, an ammonium chloride salt (e.g., benzyltributylammonium chloride), or a mixture thereof.

[0090] Examples of free radical initiators based on barbituric acid include redox initiator systems having (i) a barbituric acid derivative and / or malonyl sulfonamide and (ii) an organic peroxide selected from monofunctional or polyfunctional carboxylic acid peroxide esters. Barbituric acid derivatives that can be used include, for example, 1,3,5-trimethylbarbituric acid, 1,3,5-triethylbarbituric acid, 1,3-dimethyl-5-ethylbarbituric acid, 1,5-dimethylbarbituric acid, 1-methyl-5-ethylbarbituric acid, 1-methyl-5-propylbarbituric acid, 5-ethylbarbituric acid, 5-propylbarbituric acid, 5-butylbarbituric acid, 1-benzyl-5-phenylbarbituric acid, 1-cyclohexyl-5-ethylbarbituric acid, and thiobarbituric acid, as mentioned in the published German patent application DE42 19 700 A1 (Imai et al.).

[0091] Barbiturates and barbiturates described in U.S. Patents 3,347,954 (Bredereck et al.) and 9,957,408 (Thompson), and malonyl sulfonamides disclosed in European Patent No. EP 0 059 451B1 (Schmitt et al.), can be used in embodiments of this disclosure. Preferred malonyl sulfonamides are 2,6-dimethyl-4-isobutylmalonyl sulfonamide, 2,6-diisobutyl-4-propylmalonyl sulfonamide, 2,6-dibutyl-4-propylmalonyl sulfonamide, 2,6-dimethyl-4-ethylmalonyl sulfonamide, or 2,6-dioctyl-4-isobutylmalonyl sulfonamide.

[0092] Barbiturate-based radical initiators typically comprise monofunctional or polyfunctional carboxylic acid peroxides as organic peroxides. Within the meaning of this disclosure, carbonate peroxides are also included in the category of polyfunctional carboxylic acid peroxides. Suitable examples include diisopropyl carbonate-peroxide diester, neodecanoic acid-tert-butyl-peroxide, neodecanoic acid-tert-amyl-peroxide, maleic acid-tert-butyl-monoperoxide, benzoic acid-tert-butyl-peroxide, 2-ethylhexanoic acid-tert-butyl-peroxide, 2-ethylhexanoic acid-tert-amyl-peroxide, monoisopropyl carbonate-monotert-butyl-peroxide, dicyclohexyl carbonate-peroxide, dimyristyl carbonate-peroxide, and carbonate... Diceryl peroxide, di(2-ethylhexyl)-peroxide, tert-butyl-peroxy-(2-ethylhexyl)-peroxide or 3,5,5-trimethylhexanoic acid-tert-butyl-peroxide, benzoic acid-tert-pentyl-peroxide, acetic acid-tert-butyl-peroxide, di(4-tert-butyl-cyclohexyl)-peroxide, neodecanoic acid-isopropylbenzene-peroxide, neopentanoic acid-tert-pentyl-peroxide and neopentanoic acid-tert-butyl-peroxide.

[0093] Specifically, according to embodiments of this disclosure, tert-butyl-peroxy-(2-ethylhexyl) carbonate (commercially available from Arkema, Inc., King of Prussia, PA, via LUPEROX TBEC) or tert-butyl-peroxide 3,5,5-trimethyl-hexanoic acid (commercially available from Arkema, Inc. via LUPEROX 270) can be used as organic peroxides.

[0094] Metal salts that can be used with barbituric acid derivatives may include transition metal complexes, particularly salts of cobalt, manganese, copper, and iron. When the metal salt is a copper compound, it may have the general formula CuXn, where X is an organic and / or inorganic anion, and n = 1 or 2. Examples of suitable copper salts include copper chloride, copper acetate, copper acetylacetonate, copper naphthenate, copper salicylate, or complexes of copper with thiourea or ethylenediaminetetraacetic acid, and mixtures thereof. In some embodiments, copper naphthenate is particularly preferred.

[0095] Another redox initiator system applicable to embodiments of this disclosure comprises an inorganic peroxide, an amine-based reducing agent, and a promoter, wherein the amine may be an aromatic and / or aliphatic amine, and the polymerization promoter is at least one selected from the group consisting of sodium benzenesulfinate, sodium p-toluenesulfinate, sodium 2,4,6-triisopropylbenzenesulfinate, sodium sulfite, potassium sulfite, calcium sulfite, ammonium sulfite, sodium bisulfate, and potassium bisulfate. Examples of inorganic peroxides that can be used in this system are persulfates, as described in U.S. Patent 8,545,225 (Takei et al.).

[0096] In some embodiments, the curable composition comprises a free radical initiator comprising a metal salt (e.g., copper naphthenate) and an ammonium salt (e.g., benzyltributylammonium chloride). In some embodiments, the curable composition comprises a curing initiator system comprising a barbituric acid derivative and a metal salt, and optionally comprising at least one of an organic peroxide and an ammonium chloride salt.

[0097] The curable composition may contain at least one photoinitiator, alone or in combination with other free radical initiators, which is activated by light (typically ultraviolet (UV) lamps), but other light sources such as LED lamps, xenon flash lamps and lasers may also be used if the photoinitiator is appropriately selected.

[0098] Available photoinitiators include those known to be usable for photocuring free radical polyfunctional (meth)acrylates. Exemplary photoinitiators include benzoin and its derivatives, such as α-methyl benzoin; α-phenylbenzoin; α-allyl benzoin; α-benzyl benzoin; benzoin ethers, such as benzoin dimethyl ketal (e.g., purchased as OMNIRAD BDK from IGM Resins USA Inc., St. Charles, Illinois), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives, such as 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., purchased as OMNIRAD 1173 from IGM Resins USA Inc.) and 1-hydroxycyclohexylphenyl ketone (e.g., purchased as OMNIRAD 184 from IGM Resins USA Inc.); 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone (e.g., purchased as OMNIRAD BDK from IGM Resins USA Inc.) 907 (purchased from IGM Resins, USA); 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholino)phenyl]-1-butanone (e.g., purchased from IGM Resins, USA as OMNIRAD 369); and triarylphosphine and phosphine oxide derivatives, such as ethyl 2,4,6-trimethylbenzoylphenylphosphonate (e.g., purchased from IGM Resins, USA as TPO-L) and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (e.g., purchased from IGM Resins, USA as OMNIRAD 819).

[0099] Other available photoinitiators include, for example, pivaloin ether, anethole ether, anthraquinones (e.g., anthraquinone, 2-ethylanthraquinone, 1-chloroanthraquinone, 1,4-dimethylanthraquinone, 1-methoxyanthraquinone, or benzoanthraquinone), benzophenone and its derivatives, iodonium and sulfonium salts, titanium complexes such as bis(n5-2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrolo-1-yl)phenyl]titanium (e.g., available under the trade name CGI 784DC from BASF, Florham Park, NJ); halomethyl-nitrobenzene (e.g., 4-bromomethylnitrobenzene), and combinations of photoinitiators in which one component is monoacylphosphine oxide or diacylphosphine oxide (e.g., under the trade names IRGACURE 1700, IRGACURE 1800, and IRGACURE). Purchased in 1850 from BASF, Florem Park, New Jersey, and in OMNIRAD 4265 from IGM Resins USA.

[0100] Free radical initiators can also be thermally activated free radical initiators, such as azo initiators (e.g., azobisisobutyronitrile) or peroxides (e.g., benzoyl peroxide).

[0101] The free radical initiator is present in the curable composition in an amount sufficient to allow the curable composition to have a adequate rate of curing free radical reaction when polymerization is initiated; these amounts can be readily determined by those skilled in the art. In embodiments of this disclosure, the free radical initiator is typically present in the curable composition at a level of 0.1 to 10% by weight, more typically 0.5 to 5% by weight, of the curable free radical polymerization component; however, this is not required.

[0102] In some embodiments, the curable composition comprises, based on the total weight of the curable composition, 49% to 97% by weight of at least one monofunctional free radical polymerizable monomer, 0.1% to 10% by weight of at least one free radical initiator, and 2.9% to 50.9% by weight of at least one free radical polymerizable crosslinking agent.

[0103] The curable composition may also contain other compounds having two or more free radical polymerizable groups (e.g., hexanediol diacrylate or trimethylolpropane triacrylate); however, this is generally not preferred.

[0104] The curable composition may optionally contain one or more conventional additives. Additives may include, for example, tackifiers, plasticizers, dyes, pigments, antioxidants, UV stabilizers, corrosion inhibitors, dispersants, wetting agents, adhesion promoters, and fillers.

[0105] The fillers that can be used in the embodiments of this disclosure include, for example, fillers selected from: microfibrillated polyethylene, pyrolytic silica, talc, wollastonite, aluminosilicate clay (e.g., hydrous kaolin), phlogopite, calcium carbonate, kaolin, metal oxides (e.g., barium oxide, calcium oxide, magnesium oxide, zirconium oxide, titanium oxide, zinc oxide), nanoparticle fillers (e.g., nano silica, nano zirconium oxide), and combinations thereof.

[0106] Curable compositions may be provided as single- or two-part compositions, depending, for example, on the free radical initiator selected.

[0107] The curable compositions according to this disclosure can be at least partially cured by exposure to photochemical electromagnetic radiation (e.g., ultraviolet and / or visible light), thermal energy (e.g., in an oven, infrared radiation, or thermal conduction), by exposure to oxygen, by combining two portions of a two-part composition, or any combination thereof.

[0108] After at least partial curing, a crosslinked composition is typically obtained, and if fully cured, it can be suitable as a structural adhesive for bonding two adherends. In this application, the curable composition is typically sandwiched between the adherends and at least partially cured, for example, to the point where at least the desired level of bond strength is achieved.

[0109] The purposes and advantages of this disclosure are further illustrated by the following non-limiting embodiments, but the specific materials and quantities referenced in these embodiments, as well as other conditions and details, should not be construed as undue limitation of this disclosure.

[0110] Example

[0111] Unless otherwise stated, all parts, percentages, ratios, etc., in the examples and the remainder of this specification are by weight. Unless otherwise specified, all other reagents were obtained or purchased from fine chemical suppliers such as Sigma-Aldrich Company, St. Louis, Missouri, USA, or can be synthesized by known methods. Table 1 (below) lists the materials used in the examples and their sources.

[0112] Table 1

[0113]

[0114]

[0115] Test methods

[0116] Transmission-FTIR spectroscopy measurement

[0117] Transmission-FTIR measurements were recorded using a Thermo Nicolet iS50 system FTIR spectrometer (Thermo Fisher Scientific Co., Waltham, Massachusetts). Samples were prepared by diluting aliquots of the reaction sample in toluene to provide a solution, spreading the solution onto a salt plate, and drying it under a nitrogen stream.

[0118] Overlap shear test

[0119] Each sample formulation was individually loaded onto 10 portions of a 10:1 dual-syringe dispenser, with an accelerator from 3M SCOTCH-WELD DP8410NS acrylic adhesive (3M Company) used on 1 portion of the dispenser in each case. All adhesives were prepared by dispensing the sample formulation and accelerator via a static mixing head. Overlap shear test specimens were prepared on sandblasted aluminum substrates using the resulting adhesives. The overlap shear specimens were 2.54 cm × 10.16 cm × 16 cm aluminum specimens, using spaced beads of 0.076–0.0127 mm, with a 1.27 cm overlap. The adhesive layer was clamped with a long-tail clip during curing and the clamps were removed after 24 hours at 25°C. The overlap shear test was run on a 5000 lb (22 kN) force sensor. The value is the average of three samples.

[0120] Impact test

[0121] Each sample formulation was individually loaded onto 10 portions of a 10:1 dual-syringe dispenser, with an accelerator from SCOTCH-WELD DP8410NS acrylic adhesive (3M Company) used on 1 portion of the dispenser in each case. All adhesives were prepared by dispensing the sample formulation and accelerator into the adhesive composition used to prepare impact test specimens on sandblasted aluminum substrates via a static mixing head. The impact specimens were 2.54 cm × 10.16 cm × 16 cm aluminum specimens using beads spaced 0.076 mm–0.0127 mm with a 1.27 cm overlap. The adhesive layer was clamped with a long-tail clamp during curing and removed after 24 hours at 25°C. The specimens were tested on an Instron CP9050 impact pendulum (Norwood, Massachusetts), where the specimens were held in the clamps and impacted against the edges of the adhesive area. The test parameters conform to ISO 179-1, using a 21.6J hammer dropped at a 150.0° angle.

[0122] Tensile test of cured film

[0123] A film of the cured composition was prepared by mixing 40 g of sample formulation and 4 g of accelerator (SCOTCH-WELD DP8410NS acrylic adhesive, 3M) in a polypropylene Max100 DAC cup (part number 501 221, from FlackTek, Inc., Landrum, SC, South Carolina). The cup was closed with a polypropylene cap, and the mixture was mixed at 1500 rpm for 25 seconds under high shear at ambient temperature and pressure using a FlackTek high-speed mixer (DAC 400.2VAC). The resulting mixture was coated between silicone-treated polyester release liner at a thickness of approximately 1 mm. The coated film was allowed to stand at room temperature for at least 24 hours prior to testing. The test was performed according to ASTM Standard D638–14, 2015, "Standard Test Method for Tensile Properties of Plastics". The tensile elongation was measured using a TYPE-V die for sample cutting and a chuck test speed of 100 mm / min.

[0124] Dynamic Mechanical Analysis (DMA) Test

[0125] Membrane samples were prepared using the membrane prepared for tensile testing as described above. The membrane samples were cut into pieces approximately 6-7 mm wide × 1 mm thick × 50 mm long and tested on a DMAQ 800 (TA Instruments Inc., New Castle, Delaware) using a double cantilever clamp with the following settings: frequency = 1 Hz, oscillation amplitude = 15 micrometers (μm), and minimum oscillation force = 0.02 Newtons (N). The membrane samples were equilibrated to -75°C and held at this temperature for five minutes, then heated to 150°C at a rate of 3.0°C / min.

[0126] Methacryloxy-terminated HC1101 (HC1101-GMA) ) Synthesis

[0127] Add 200 g of HC1101 polymer (branched poly(tetrahydrofuran)diamine, with a primary (1°) amine content of 7143 g / equivalent and a total amine content of 5243 g / equivalent) to a Max 200 DAC cup (Flaketech). Heat the cup at 70°C for 3 hours to melt the material, then add glycidyl methacrylate (5.69 g, AlfaAesar). Stir the mixture manually using a wooden tongue depressor and mix at 2000 rpm for 1 minute using a DAC 400 high-shear mixer. Monitor the mixture using transmission FTIR with 15 mil silicone rubber spacers. Due to the presence of epoxy groups, at 4535 cm⁻¹... -1 A small peak was observed, so the sample was placed back in a 70°C oven for four hours. At this time, transmission FTIR showed that there were basically no remaining epoxy group peaks.

[0128] Example 1 (EX-1)

[0129] The curable adhesive was prepared by mixing the components of Table 2 in a polypropylene MAX 200DAC cup (part number 501 220, FlackTek, Inc.). After capping with a polypropylene lid, the mixture was mixed three times at 1500 rpm for one minute in a high-speed mixer (DAC400.2VAC, FlackTek, Inc.), with manual stirring using a wooden tongue depressor between mixes. The sample was degassed by capping with a polypropylene lid containing vent holes and mixed at high shear at 2000 rpm under reduced pressure (35 Torr). The curable adhesive was stored refrigerated (approximately 6°C) until use.

[0130] Table 2

[0131] Components Number of portions (g) XT100 9.4 MMA 10.9 HEMA 5.2 SR340 17.8 HC1101-GMA crosslinking agent 37.7 MA 13.4 NK Ester SA 3.4 <![CDATA[BzBu3N + Cl - ]]> 2.1 CuNap 0.1

[0132] The above procedure was used to prepare bonds between sandblasted aluminum samples incorporating the curable adhesive listed in Table 2. The lap shear test and impact test procedures were described above, and the test results are reported in Tables 3 and 4 below.

[0133] Table 3

[0134]

[0135] Table 4

[0136]

[0137] Sample film and adhesion test

[0138] The above procedure was used to prepare a film coating incorporating a curable adhesive. The test procedure for measuring tensile elongation and performing dynamic mechanical analysis (“DMA”) using the prepared film coating was described above. The test results for the sample films are reported in Tables 5 and 6 below.

[0139] Table 5

[0140]

[0141]

[0142] Table 6

[0143]

[0144] References, patents, and patent applications cited in this application are incorporated in a consistent manner. In the event of any inconsistency or contradiction between the incorporated references and this application, the information in this application shall prevail. The foregoing description, given to enable those skilled in the art to practice this disclosure protected by the claims, should not be construed as limiting the scope of this disclosure, which is defined by the claims and all their equivalents.

Claims

1. A crosslinking agent capable of free radical polymerization, comprising a divalent segment Z represented by the following formula: Each of the two-valent segments Z is directly bonded to: i) Two secondary N atoms, each of which is further directly bonded to a divalent segment Z or X group. ii) Two tertiary N atoms, each of which is further directly bonded to p additional divalent Z segments and (2-p) X groups, wherein p is 0, 1, or 2; or iii) A secondary N atom, which is further directly bonded to: an additional divalent segment Z or X group; and a tertiary N atom, which is further directly bonded to p additional divalent segments Z and (2-p) X groups. Each R 1 Independently representing alkyl subgroups having 1 to 4 carbon atoms, Each n independently represents a positive integer, and Each X group is independently represented by the following formula: Each L independently represents a covalent bond, O, S, NR. 1 Or having a divalent linker group with 2 to 8 carbon atoms and at most 3 oxygen atoms, and Each R 2 Independently, it is a free radical polymerizable group selected from ethoxy, methacryloxy, allyloxy, vinylaryl having 8 to 12 carbon atoms, and 2-propenylaryl having 9 to 13 carbon atoms. The prerequisite is that no two O, S, or N atoms in the X group are adjacent. The free radical polymerizable crosslinking agent has a number average molecular weight of 4,000 g / mol to 54,000 g / mol relative to a polystyrene standard, as measured by gel permeation chromatography at 40°C.

2. The free radical polymerizable crosslinking agent according to claim 1, wherein R 2 It is ethyleneoxy, methacryloyloxy, or allyloxy.

3. The crosslinking agent that can be polymerized by free radicals according to claim 1 or 2, wherein L is a covalent bond.

4. The free radical polymerizable crosslinking agent according to claim 1 or 2, wherein the free radical polymerizable crosslinking agent has two X groups.

5. The free radical polymerizable crosslinking agent according to claim 1 or 2, wherein the free radical polymerizable crosslinking agent has at least two X groups.

6. The free radical polymerizable crosslinking agent according to claim 1 or 2, wherein the free radical polymerizable crosslinking agent has at least three X groups.

7. The free radical polymerizable crosslinking agent according to claim 1 or 2, wherein R 1 It is -CH2CH2CH2CH2-.

8. A curable composition, said curable composition comprising: At least one monofunctional monomer that can be polymerized by free radicals; Free radical initiators; and At least one crosslinking agent that can be polymerized by free radicals according to any one of claims 1 or 2.

9. The curable composition according to claim 8, wherein the at least one monofunctional free radical polymerizable monomer is selected from methyl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, methacrylic acid, 2-(2-butoxyethoxy)ethyl methacrylate, glycerol formaldehyde methacrylate, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and combinations thereof.

10. The curable composition of claim 8, wherein the curable composition comprises 49% to 97% by weight of the at least one monofunctional free radical polymerizable monomer, 0.1% to 10% by weight of the free radical initiator, and 2% to 60% by weight of the at least one free radical polymerizable crosslinking agent.

11. The curable composition of claim 8, wherein the curable composition further comprises a filler.

12. The curable composition according to claim 11, wherein the filler is selected from microfibrillated polyethylene, pyrolytic silica, talc, wollastonite, aluminosilicate clay, phlogopite, calcium carbonate, kaolin, and combinations thereof.

13. An adhesive comprising a partially cured reaction product of the curable composition according to claim 8.

14. An adhesive comprising a cured reaction product of the curable composition according to claim 8.

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