Curable precursor of adhesive composition

Abstract

The present disclosure relates to a curable precursor of an adhesive composition comprising (a) a radically (co)polymerizable compound, (b) a vanadium compound, (c) a β-dicarbonyl compound, and (d) a quaternary ammonium halide. The present disclosure further relates to a method of curing the curable precursor.

Description

[Technical field]

[0001] The present disclosure relates to a curable precursor of an adhesive composition comprising a radically (co)polymerizable compound, a vanadium compound, a β-dicarbonyl compound, and a quaternary ammonium halide. [Background technology]

[0002] Curable compositions have been known for many years as being suitable for use in a variety of applications, including general-purpose industrial applications such as adhesives and coatings, as well as high-performance applications in the electronics industry, such as, for example, sealing and bonding electronic components. With the widespread use of curable compositions over the years, performance requirements have become increasingly stringent, particularly with regard to cure profile, adhesive performance, storage stability, handling and processability properties, as well as compliance with environmental and health requirements.

[0003] In electric motors, such as electric motors for automobiles, the motor core is made by laminating steel sheets. Usually, the lamination is performed by bundling using dowels. The weakness of this method is that the laminated motor core has iron losses due to electrical short circuits and the laminated core has insufficient strength, especially when the steel sheets are relatively thin.

[0004] To overcome these weaknesses, lamination methods using adhesives have been studied. The requirements for adhesives for this application are high adhesive strength, thin bond line thickness to allow high filling rate of laminated steel sheets in the motor core, rapid curing to mass produce motor cores cost-effectively, and high temperature durability to withstand the heat generated in the motor during use.

[0005] To achieve fast cure rates, anaerobic adhesives containing accelerators have been used. The drawbacks of this type of adhesive are that it has low bond strength at high temperatures and the presence of air tends to cause poor cure, especially at the edges of the adhesive layer.

[0006] To achieve high adhesive strength, one-part heat-curing epoxy adhesives have been used. This type of adhesive requires a heating process, which is undesirable. Also, two-part epoxy or acrylic adhesives have been used. This type of adhesive requires a mixing step and takes a long time to achieve the strength required for further handling.

[0007] WO 2016 / 053877(A1) discloses a method for curing a curable composition, the curable composition comprising a free radically polymerizable compound, a quaternary ammonium halide, and a polyvalent metal compound for free radical curing of the curable composition. The polyvalent metal compound comprises a copper (II) compound, an iron (II or III) compound, a cobalt (II or III) compound, or a manganese (III or III) compound. For curing of the curable composition, a substrate on which a solid primer layer is disposed is contacted with the curable composition, the solid primer layer comprising a binder material and an organic peroxide. The disadvantages of this method are the long processing times due to the need for a primer layer that typically needs to be dried for 30 minutes, and the relatively long curing times of 30 minutes to 24 hours.

[0008] US Patent No. 6,552,140(B1) discloses an air-activatable polymerizable composition comprising a free radically polymerizable monomer, an activator system for the polymerization of the free radically polymerizable monomer, a soluble ionic salt, and a weak acid or a latent weak acid, the activator system comprising an autooxidizing compound that is a β-diketone. The air-activatable composition does not contain peroxides or peroxide precursors that generate peroxides in the absence of air, or any component that is a significant source of radicals in the absence of air.

[0009] There remains a need for curable precursors to adhesive compositions that achieve rapid handling strength without sacrificing the ultimate adhesive strength of the adhesive composition, i.e., that achieve a balance of providing adhesive strength very quickly while still having good ultimate performance.

[0010] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. The term "comprising" is also intended to include the terms "consisting essentially of" and "consisting of." Summary of the Invention

[0011] In a first aspect, the present disclosure provides a curable precursor to an adhesive composition, comprising: (a) a radically (co)polymerizable compound, (b) vanadium compounds, (c) β-dicarbonyl compounds, and (d) Quaternary ammonium halides The present invention relates to a curable precursor comprising:

[0012] The curable precursor disclosed herein may comprise a first portion and a second portion, the first portion comprising a radically (co)polymerizable compound; (i) a first portion comprises a vanadium compound and a quaternary ammonium halide, and a second portion comprises a β-dicarbonyl compound; or (ii) the first portion contains a β-dicarbonyl compound and the second portion contains a vanadium compound and a quaternary ammonium halide; Either:

[0013] In another aspect, the present disclosure also provides a method of curing a curable precursor of the adhesive composition disclosed herein, comprising: providing a curable precursor comprising a first portion and a second portion as disclosed herein; Providing a first substrate having a contact surface and a second substrate having a contact surface; applying a first portion of a curable precursor onto at least a portion of a contact surface of a first substrate; applying a second portion of the curable precursor onto at least a portion of the contact surface of the second substrate; curing the curable precursor of the adhesive composition by contacting a first portion of the curable precursor on the contact surface of the first substrate with a second portion of the curable precursor on the contact surface of the second substrate. The present invention relates to a method comprising the steps of:

[0014] The hardenable precursors disclosed herein allow for rapid curing, which allows them to be used in cost-effective, mass-produced applications, such as laminating steel sheets for motor cores in electric motors for automobiles and the like.

[0015] The curable precursors disclosed herein have good handling strength already after a short curing time. By "good handling strength" it is intended that the bond can be moved without the two substrates moving independently. Handling strength can be tested by hanging a 3 kg weight to create a stress of 0.1 MPa on the bond and checking whether the bond holds for at least 10 seconds. In some embodiments, the curable precursors disclosed herein can withstand a shear stress of 0.1 MPa or more at room temperature (23°C) after only 30 seconds of curing time.

[0016] The curable precursors disclosed herein can be cured at room temperature and do not require additional means such as UV light or heat to cure.

[0017] To cure the curable precursor disclosed herein, a separate step of mixing the first and second parts of the curable precursor is not required. The first part of the curable precursor is applied onto the contact surface of the first substrate to be joined, and the second part of the curable precursor is applied onto the contact surface of the second substrate to be joined, and curing occurs by contacting the first part of the curable precursor on the contact surface of the first substrate with the second part of the curable precursor on the contact surface of the second substrate. Curing does not begin until the first and second substrates are brought together, and upon connection, the two parts spontaneously mix by diffusion and cure to provide bond strength. The curable precursor can be cured substantially uniformly without any physical mixing process.

[0018] The curable precursors disclosed herein allow for thin bond line thickness, which is important for high fill factor steel lamination in motor cores.

[0019] The curable precursors disclosed herein have good high temperature stability and durability required to withstand the heat generated in motors during use.

[0020] The curable precursors disclosed herein have high adhesive strengths. In some embodiments, the curable precursors disclosed herein have high adhesive strengths of 2 MPa or more at 180° C., which can be obtained already after a curing time of 48 hours.

[0021] The curable precursors disclosed herein have air-activated initiators that generate peroxide in situ. Initiators include β-dicarbonyl compounds and vanadium compounds. The air-activated initiators reduce the tendency for cure failure, especially at the edges of the adhesive layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A curable precursor of an adhesive composition, comprising: (a) a radically (co)polymerizable compound, (b) vanadium compounds, (c) β-dicarbonyl compounds, and (d) Quaternary ammonium halides Disclosed herein is a curable precursor comprising:

[0023] "Curable precursor" is intended to denote a composition that can be cured using an initiator.

[0024] "Radically (co)polymerizable compounds" is intended to indicate compounds that can be cured using initiators that contain or can generate free radicals. Radically (co)polymerizable compounds may contain only one, two, or more than two radically polymerizable groups. Typical examples of radically (co)polymerizable groups include unsaturated carbon groups, such as vinyl groups present in (meth)acrylate groups.

[0025] As used herein, "(co)polymeric" is a contraction that refers to "polymeric" and / or "copolymeric."

[0026] The vanadium compound is not particularly limited, as long as it is stable in the curable precursor (as a solution or dispersion), i.e., does not settle to the bottom, and is well mixed throughout to ensure uniform and consistent curing of the adhesive composition. Suitable vanadium compounds for use herein are vanadyl acetylacetonate, vanadium acetylacetonate, vanadium oxide acetylacetonate, vanadyl oxalate, vanadium chloride, vanadium oxide, and vanadium sulfate.

[0027] Preferably, the vanadium compound comprises vanadyl acetylacetonate.

[0028] The quaternary ammonium halide contained in the curable precursor is at least partially soluble in the curable composition.The quaternary ammonium halide should remain well distributed throughout the curable precursor to ensure the even and complete curing of the curable precursor.The quaternary ammonium halide can improve the degree of curing of the adhesive composition.

[0029] Suitable quaternary ammonium halides include those having four hydrocarbyl groups (e.g., alkyl, alkenyl, cycloalkyl, aralkyl, alkaryl, and / or aryl). Preferably, the hydrocarbyl groups are independently selected from hydrocarbyl groups having 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, more preferably 1 to 4 carbon atoms. Examples of suitable hydrocarbyl groups include methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, hexadecyl, and octadecyl, benzyl, phenyl, tolyl, cyclohexyl, and methylcyclohexyl. Exemplary suitable quaternary ammonium compounds include tetramethylammonium halide, tetraethylammonium halide, tetrapropylammonium halide, tetrabutylammonium halide, ethyltrimethylammonium halide, diethyldimethylammonium halide, trimethylbutylammonium halide, trioctylmethylammonium halide, and benzyltributylammonium halide. Any halide (eg, F, Cl, Br, I) ion may be used in the quaternary ammonium halide, but preferably the halide ion is chloride or bromide, more preferably chloride.

[0030] In some embodiments, trioctylmethylammonium chloride is used as the quaternary ammonium halide.

[0031] The curable precursors disclosed herein may comprise from 0.01 weight percent to 5 weight percent, preferably from 0.1 weight percent to 2 weight percent, of a quaternary ammonium halide, based on the total weight of the curable precursor.

[0032] The curable precursors disclosed herein typically comprise a first part and a second part. The first part comprises a radically (co)polymerizable compound. The vanadium compound, the β-dicarbonyl compound, and the quaternary ammonium halide are distributed between the first and second parts of the curable precursor according to one of the following two options: (i) a first portion comprises a vanadium compound and a quaternary ammonium halide, and a second portion comprises a β-dicarbonyl compound; or (ii) the first portion comprises a β-dicarbonyl compound and the second portion comprises a vanadium compound and a quaternary ammonium halide.

[0033] This means that the vanadium compound and the β-dicarbonyl compound are present in different parts of the hardenable precursor, and also the quaternary ammonium chloride and the β-dicarbonyl compound are present in different parts of the hardenable precursor.

[0034] In some preferred embodiments, the vanadium compound, the β-dicarbonyl compound, and the quaternary ammonium halide are distributed between a first and a second part of the hardenable precursor according to option (i), i.e., the first part comprises the vanadium compound and the quaternary ammonium halide, and the second part comprises the β-dicarbonyl compound.

[0035] The second portion of the curable precursor preferably comprises (e) an initiator for radical (co)polymerizing a radical (co)polymerizable compound Further includes:

[0036] The term "initiator" is intended to refer to a substance or group of substances capable of starting or initiating or contributing to the curing process of a curable precursor, i.e. capable of starting or initiating or contributing to the radical (co)polymerization of a radically (co)polymerizable compound.

[0037] The vanadium compound and the β-dicarbonyl compound contained in the curable precursor can be formed in situ, i.e. after contacting the vanadium compound and the β-dicarbonyl compound contained in two different parts of the curable precursor. After contacting the vanadium compound and the β-dicarbonyl compound, the air-activated curing starts by the in situ formation of a peroxide having the function of an initiator for the radical (co)polymerization of the radical (co)polymerizable compound. In some embodiments of the curable precursor, the curable precursor comprises an additional initiator (e) for the radical (co)polymerization of the radical (co)polymerizable compound. The initiator (e) is included in the curable precursor in addition to the initiator formed in situ by the reaction between the vanadium compound and the β-dicarbonyl compound. The additional initiator (e) is included in the second part of the curable precursor. By adding the initiator (e), the curing time can be reduced.

[0038] The additional initiator (e) may be an organic peroxide.

[0039] The organic peroxide may be a monofunctional or polyfunctional carboxylic acid peroxyester. Commercially available organic peroxides include, for example, t-alkyl esters of peroxycarboxylic acids, t-alkyl esters of monoperoxycarboxylic acids, di(t-alkyl) esters of diperoxydicarboxylic acids, alkylene diesters of peroxycarboxylic acids, dialkyl peroxydicarbonates, and O,Ot-alkyl O-alkyl diesters of monoperoxycarbonic acid. Exemplary organic peroxides include diisopropyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-amyl peroxyneodecanoate, maleic acid t-butyl monoperoxyester, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, O-isopropyl O,Ot-butyl monoperoxycarbonate, dicyclohexyl peroxycarbonate, dimyristyl peroxycarbonate, dicetyle ... Examples of suitable organic peroxides include butyl peroxycarbonate, di(2-ethylhexyl)peroxycarbonate, O,Ot-butyl O-2-ethylhexylperoxycarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-amylperoxybenzoate, t-butylperoxyacetate, di(4-t-butylcyclohexyl)peroxycarbonate, cumylperoxyneodecanoate, t-amylperoxypivalate, cumene hydroperoxide, dibenzoylperoxide, and t-butylperoxypivalate. Further suitable organic peroxides are known to those skilled in the art.

[0040] A preferred additional initiator (e) is cumene hydroperoxide.

[0041] Typically, the amount of additional initiator (e) is from 0.1 weight percent to 20 weight percent, preferably from 0.2 weight percent to 10 weight percent, and more preferably from 0.3 weight percent to 5 weight percent, based on the total weight of the curable precursor.

[0042] The curable precursor comprises at least one radically (co)polymerizable compound. Useful radically (co)polymerizable compounds may include ethylenically unsaturated compounds having one or more (e.g., one, two, three, four, or more) radically (co)polymerizable groups.

[0043] The radically (co)polymerizable compounds of the curable precursors disclosed herein may include at least one of (meth)acrylates, (meth)acrylamides, other vinyl compounds, and combinations thereof.

[0044] As used herein, "(meth)acrylate" is a contraction that refers to "acrylate" and / or "methacrylate." For example, "(meth)acrylamide" refers to "acrylamide" and / or "methacrylamide."

[0045] Preferably, the radically (co)polymerizable compound of the curable precursor disclosed herein comprises a (meth)acrylate, which may be a monomer, oligomer, or polymer.

[0046] A "monomer" is any chemical that can be characterized by a chemical formula having a radically polymerizable unsaturated group (including a (meth)acrylate group) that can be polymerized into an oligomer or polymer to increase molecular weight. Usually, the molecular weight of a monomer can be simply calculated based on the given chemical formula.

[0047] "Polymer" or "polymeric material" are used interchangeably to refer to homopolymers, copolymers, terpolymers, and the like.

[0048] In some embodiments, the radically (co)polymerizable compound comprises a (meth)acrylate with a functionality greater than one.

[0049] In some embodiments, the radically (co)polymerizable compound comprises a (meth)acrylate having a functionality of at least two.

[0050] In some embodiments, the radically (co)polymerizable compound comprises a (meth)acrylate having a functionality of at least three.

[0051] By "functionality of 1" it is intended that the (meth)acrylate is a monofunctional (meth)acrylate. By "functionality of 2" it is intended that the (meth)acrylate is a difunctional (meth)acrylate. By "functionality of 3" it is intended that the (meth)acrylate is a trifunctional (meth)acrylate. By "monofunctional (meth)acrylate" it is intended to indicate a (meth)acrylate compound having one (meth)acryloyl functional group (having the structure H2C=CH-C(=O)-, sometimes also referred to as "(meth)acrylyl" or simply "(meth)acrylic" functionality). By "difunctional (meth)acrylate" it is intended to indicate a (meth)acrylate compound having two (meth)acryloyl functional groups. By "trifunctional (meth)acrylate" it is intended to indicate a (meth)acrylate compound having three (meth)acryloyl functional groups.

[0052] By "functionality greater than 1" it is intended that the functionality of the (meth)acrylate is greater than 1, i.e. the functionality may be 2 or 3, or a non-integer number greater than 1 and less than 2, or a non-integer number greater than 2 and less than 3, or a non-integer number greater than 3. An example of a (meth)acrylate with non-integer functionality is a (meth)acrylate that is an oligomer with (meth)acrylate side chains on average 2.3 side chains per oligomer (i.e. some of the oligomer molecules have 2 side chains and some of the oligomer molecules have 3 side chains, for an average of 2.3 side chains for all oligomer molecules). This oligomer has an average of 2.3 (meth)acryloyl functional groups, and is therefore a (meth)acrylate with a functionality of 2.3.

[0053] By "functionality of at least 2" it is intended that the functionality of the (meth)acrylate is 2 or greater, i.e., the functionality can be 2 or 3, or a non-integer number greater than 2 and less than 3, or a non-integer number greater than 3.

[0054] By "functionality of at least 3" it is intended that the functionality of the (meth)acrylate is 3 or greater, ie, the functionality may be 3 or a non-integer number greater than 3.

[0055] Examples of suitable monofunctional (meth)acrylates include 1,6-hexanediol (meth)acrylate, 2-phenoxyethyl (meth)acrylate, allyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isobornyl (meth)acrylate, isopropyl (meth)acrylate, methyl (meth)acrylate, n-hexyl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and dicyclopentadienyl (meth)acrylate.

[0056] Examples of suitable difunctional (meth)acrylates include 1,3-butylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, bis[1-(2-(meth)acryloxy)]-p-ethoxyphenyl dimethyl methane, bis[1-(3-(meth)acryloxy-2-hydroxy)]-p-propoxyphenyl dimethyl methane, caprolactone-modified neopentyl glycol hydroxypivalate di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol di(meth)acrylate, and dipropylene glycol. di(meth)acrylate, ethoxylated (10) bisphenol A di(meth)acrylate, ethoxylated (3) bisphenol A di(meth)acrylate, ethoxylated (4) bisphenol A di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, ethylene glycol di(meth)acrylate, hydroxypivalaldehyde-modified trimethylolpropane di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate.

[0057] Examples of suitable trifunctional (meth)acrylates include 1,2,4-butanetriol tri(meth)acrylate, ethoxylated (20) trimethylolpropane tri(meth)acrylate, ethoxylated (3) trimethylolpropane tri(meth)acrylate, ethoxylated (30) bisphenol A di(meth)acrylate, ethoxylated (6) trimethylolpropane tri(meth)acrylate, ethoxylated (9) trimethylolpropane tri(meth)acrylate, glycerol ... ) acrylate, pentaerythritol tri(meth)acrylate, propoxylated (3) glyceryl tri(meth)acrylate, propoxylated (3) trimethylolpropane tri(meth)acrylate, propoxylated (5,5) glyceryl tri(meth)acrylate, propoxylated (6) trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate.

[0058] Examples of suitable (meth)acrylates having a functionality greater than 3 include dipentaerythritol penta(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethoxylated (4) pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, sorbitol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0059] Examples of suitable monofunctional (meth)acrylamides include N,N-dimethylacrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, diacetone (meth)acrylamide, and (meth)acryloylmorpholine.

[0060] An example of a suitable difunctional (meth)acrylamide is methylene bis(meth)acrylamide.

[0061] Oligomers of (meth)acrylate and (meth)acrylamide monomers may also be used.

[0062] Further examples of suitable (meth)acrylates include monomers and oligomers of unsaturated carboxylic acids, such as (meth)acrylic acid and aromatic (meth)acrylic acids (e.g., methacrylated trimellitic acid).Acrylic acid and methacrylic acid are examples of monofunctional (meth)acrylates.

[0063] In some embodiments, the curable precursor comprises methacrylic acid. The amount of methacrylic acid may be from 10 weight percent to 50 weight percent based on the total amount of the curable precursor.

[0064] Examples of suitable radically (co)polymerizable vinyl compounds include styrene, dialkyl phthalates, divinyl succinates, divinyl adipates, and divinyl phthalates. Other suitable radically (co)polymerizable compounds include, for example, siloxane-functional (meth)acrylates as disclosed in WO 00 / 38619 (Guggenberger et al.), WO 01 / 92271 (Weinmann et al.), WO 01 / 07444 (Guggenberger et al.), WO 00 / 42092 (Guggenberger et al.), and fluoropolymer-functional (meth)acrylates as disclosed, for example, in U.S. Pat. No. 5,076,844 (Fock et al.), U.S. Pat. No. 4,356,296 (Griffith et al.), EP 0373384 (Wagenknecht et al.), EP 0201031 (Reiners et al.), and EP 0201778 (Reiners et al.).

[0065] Suitable radical (co)polymerizable compounds may contain hydroxyl groups and radically active functional groups in a single molecule. Examples of such materials include hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyrate, poly(propylene glycol) (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol mono- or di-(meth)acrylate, trimethylolpropane mono- or di-(meth)acrylate, pentaerythritol mono-, di-, and tri-(meth)acrylate, sorbitol mono-, di-, tri-, tetra-, or penta-(meth)acrylate, and 2,2-bis[4-(2-hydroxy-3-methyacryloxypropoxy)phenyl]propane (BisGMA).

[0066] Suitable radically (co)polymerizable compounds are available from a wide variety of commercial sources, such as, for example, Sartomer Co. (Exton, Pennsylvania), or can be made by known methods.

[0067] Typically, the hardenable precursor comprises a sufficient amount of a radically (co)polymerizable compound to provide the desired hardening or curing rate and the desired overall properties after curing / hardening. Mixtures of radically (co)polymerizable compounds may be used if desired.

[0068] The curable precursors disclosed herein may comprise at least 20 weight percent of the radically (co)polymerizable compound, based on the total weight of the curable precursor.

[0069] Typically, the amount of the radically (co)polymerizable compound is from 20 weight percent to 99.9 weight percent of the curable precursor, or from 25 weight percent to 98 weight percent, or from 25 weight percent to 95 weight percent, based on the total weight of the curable precursor.

[0070] In some embodiments, the amount of the radically (co)polymerizable compound is from 75 weight percent to 99.9 weight percent of the curable precursor, preferably from 80 weight percent to 98 weight percent, and more preferably from 85 weight percent to 95 weight percent, based on the total weight of the curable precursor.

[0071] The curable precursors disclosed herein may comprise at least 20 weight percent (meth)acrylate, based on the total weight of the curable precursor.

[0072] The amount of (meth)acrylate may be from 20 weight percent to 99.9 weight percent, or from 25 weight percent to 98 weight percent, or from 25 weight percent to 95 weight percent of the curable precursor, based on the total weight of the curable precursor.

[0073] In some embodiments, the amount of (meth)acrylate is from 75 weight percent to 99.9 weight percent of the curable precursor, preferably from 80 weight percent to 98 weight percent, and more preferably from 85 weight percent to 95 weight percent, based on the total weight of the curable precursor.

[0074] The curable precursor may comprise at least 30 weight percent, preferably at least 35 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality greater than 1. In some embodiments, the curable precursor comprises at least 40 weight percent, or at least 45 weight percent, or at least 50 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality greater than 1.

[0075] The curable precursor may comprise at least 30 weight percent, preferably at least 35 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality of at least 2. In some embodiments, the curable precursor comprises at least 40 weight percent, or at least 45 weight percent, or at least 50 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality of at least 2.

[0076] The curable precursor may comprise at least 30 weight percent, preferably at least 35 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality of at least 3. In some embodiments, the curable precursor comprises at least 40 weight percent, or at least 45 weight percent, or at least 50 weight percent, based on the total weight of the radically (co)polymerizable compounds, of (meth)acrylates having a functionality of at least 3.

[0077] In some embodiments, the curable precursor comprises from 30 weight percent to 100 weight percent of (meth)acrylates having a functionality of at least 3, based on the total weight of the radically (co)polymerizable compounds. Preferably, the curable precursor comprises from 30 weight percent to 80 weight percent of (meth)acrylates having a functionality of at least 3, based on the total weight of the radically (co)polymerizable compounds. More preferably, the curable precursor comprises from 30 weight percent to 60 weight percent of (meth)acrylates having a functionality of at least 3, based on the total weight of the radically (co)polymerizable compounds.

[0078] The vanadium compound may be added to the curable precursor in any effective amount. Typically, the curable precursor disclosed herein comprises 0.0005 weight percent to 1.0 weight percent of the vanadium compound based on the total weight of the curable precursor. In some embodiments, the curable precursor disclosed herein comprises at least 0.01 weight percent, or at least 0.02 weight percent, or at least 0.05 weight percent, or at least 0.1 weight percent of the vanadium compound based on the total weight of the curable precursor. Preferably, the curable precursor disclosed herein comprises at least 0.01 weight percent and up to 0.5 weight percent, more preferably at least 0.02 weight percent and up to 0.5 weight percent of the vanadium compound based on the total weight of the curable precursor.

[0079] The β-dicarbonyl compounds used in the curable precursors disclosed herein have the formula [ka] [In the formula, X 1 and X 2 are independently a covalent bond, O, S, [ka] (In the formula, each R 4 each independently represents hydrogen or alkyl having 1 to 18 carbon atoms; R 1 and R 2 independently represents a hydrocarbyl group or a substituted hydrocarbyl group having 1 to 18 carbon atoms; R 3 represents hydrogen, or a hydrocarbyl or substituted hydrocarbyl group having 1 to 18 carbon atoms; Or, R 1 , R 2 , or R 3 any two of these may be combined to form a 5- or 6-membered ring. or a salt thereof.

[0080] Preferably, R 1 and R 2 Each of R has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 4 carbon atoms. 1 and R 2 The groups include methyl, ethyl, isopropyl, n-propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, hexadecyl, and octadecyl. In general, the nature of the substituents in the substituted hydrocarbyl group (which may be mono- or polysubstituted) is not particularly important, except that those that interfere with radical polymerization should be used sparingly or completely excluded. Exemplary substituted hydrocarbyl groups include hydroxyhydrocarbyl groups (e.g., hydroxyethyl and hydroxypropyl), alkoxyhydrocarbyl groups (e.g., methoxyethyl and methoxyethoxy), alkanoylhydrocarbyl groups (e.g., acetylethyl and benzoylethyl), haloalkyl groups (e.g., chloroethyl and dichloropropyl), and dialkylaminohydrocarbyl groups (e.g., dimethylaminopropyl and diethylaminoethyl).

[0081] In some embodiments, R 1 , R 2 , and R 3 Any two of R taken together form a 5- or 6-membered ring. In these embodiments, the combined R 1 , R 2 , and R 3 Two of them, for example, [ka] and combinations thereof [wherein each R 4may independently represent H or an alkyl group having 1 to 18 carbon atoms (preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms), and y is 1, 2, or 3. For example, the β-dicarbonyl compound may be 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid). Exemplary R 4 Groups include hydrogen, methyl, ethyl, isopropyl, n-propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, hexadecyl, and octydecyl. R 1 , R 2 , and R 3 Examples of divalent groups formed by two of them taken together include alkylene, alkyleneoxy, oxycarbonyloxy, carbonylalkylene, alkylenecarbonyloxy, alkyleneoxycarbonyl, alkylene(alkyl)amino, and dialkylene(alkyl)amino. 1 and R 2 When they are joined together to form a five-membered ring, X 1 Or X 2 At least one of the bonds is a covalent bond.

[0082] R 3 may represent hydrogen or a hydrocarbyl group having 1 to 18 carbon atoms. 3 Groups include methyl, ethyl, isopropyl, n-propy, butyl, pentyl, hexyl, octyl, decyl, dodecyl, hexydecyl, phenyl, cyclohexyl, methylcyclohexyl, and octadecyl. Exemplary substituted hydrocarbyl groups R 3 As an example, -CH2C(=O)OR 4 In the formula, R 4 is as defined above (e.g., R 4 can be H, methyl, ethyl, dodecyl, or octadecyl).

[0083] X 1 and X 2 each independently represents a covalent bond, O, S, [ka] [In the formula, R 4 is as above].

[0084] In some embodiments, the β-dicarbonyl compound is a barbituric acid (i.e., R 3 =H, and X 1 and X 2 Both and = [ka] (In the formula, R 4 =H), and the combined R 1 and R 2 = carbonyl), or a derivative thereof (e.g., 1,3-dialkylbarbituric acid). Examples of suitable barbituric acid derivatives include 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, and 1-cyclohexyl-5-ethylbarbituric acid.

[0085] In some embodiments, the β-dicarbonyl compound comprises a dialkyl 2-acetylsuccinate diester having 8 to 14 carbon atoms, preferably 8 to 12 carbon atoms, more preferably 8 to 10 carbon atoms. The dialykl 2-acetylsuccinate diester may be substituted or unsubstituted. Examples include dimethyl 2-acetylsuccinate, diethyl 2-acetylsuccinate, and methyl ethyl 2-acetylsuccinate.

[0086] Useful salts of β-dicarbonyl compounds include alkali metal (e.g., lithium, sodium, potassium, or cesium) salts, NH4 + Salts and organic ammonium salts, preferably 1°, 2°, 3°, and 4° (i.e., primary, secondary, tertiary, and quaternary), having 1 to 24 carbon atoms, include tetrabutylammonium, dibenzyldimethylammonium, benzyltributylammonium, and tetraethylammonium salts.

[0087] The curable precursors disclosed herein can include from 0.05 weight percent to 20 weight percent, preferably from 0.1 weight percent to 10 weight percent, of a β-dicarbonyl compound based on the total weight of the curable precursor.

[0088] In some embodiments of the curable precursors disclosed herein, the first portion of the curable precursor further comprises a monofunctional (meth)acrylate, ie, a (meth)acrylate having a functionality of one.

[0089] The amount of the monofunctional (meth)acrylate may be 20% by weight to 80% by weight, preferably 30% by weight to 70% by weight, and more preferably 40% by weight to 60% by weight, based on the total weight of the radically (co)polymerizable compounds.

[0090] The curable precursors disclosed herein may further comprise a hydrophobic solvent.

[0091] As for the hydrophobic solvent, any hydrophobic solvent that does not react with the β-dicarbonyl compound and does not react with the additional initiator (e) may be used. Suitable hydrophobic solvents are paraffins such as liquid paraffin, and ether acetates such as diethylene glycol monobutyl ether acetate (CAS No. 124-17-4). Plasticizers, such as those based on dipropylene glycol dibenzoate (e.g., Benzoflex 9-88, available from Eastman Chemical Company (Kingsport, TN, USA)), may also be used as hydrophobic solvents.

[0092] The hydrophobic solvent can be used as a non-reactive diluent for the components of the curable precursor, such as the β-dicarbonyl compound and, if present, the initiator. The hydrophobic solvent can migrate to the surface of the curable precursor to prevent oxygen inhibition of the polymerization of the radically (co)polymerizable compounds of the curable precursor.

[0093] The hydrophobic solvent may be present in the first part or the second part of the curable precursor. The hydrophobic solvent may also be present in both the first part and the second part of the curable precursor.

[0094] The amount of hydrophobic solvent present in the curable precursor may be up to 70 weight percent, based on the total weight of the curable precursor. Typically, the amount of hydrophobic solvent is up to 20 weight percent, or up to 10 weight percent, based on the total weight of the curable precursor.

[0095] The curable precursor disclosed herein may further comprise a thixotropic agent. The thixotropic agent may be included in the first part or the second part of the curable precursor. The thixotropic agent may also be included in the first part and the second part of the curable precursor. The thixotropic agent may help to control the rheological properties of the precursor, for example, how thickly it coats a substrate. An example of a useful thixotropic agent is hydrophilic fumed silica.

[0096] The curable compositions disclosed herein may optionally include additives such as, for example, one or more fillers, antioxidants, plasticizers, tackifiers, thickeners, fragrances, hindered amine light stabilizers (HALS), UV stabilizers, inhibitors (which may, for example, be associated with a radically polymerizable compound), coating aids, coupling agents, toughening agents, or combinations thereof. Examples of fillers include silica, clay, and surface-modified clay. Exemplary toughening agents include elastomeric materials such as various synthetic rubbers (e.g., methyl methacrylate-butadiene-styrene (MBS) copolymers, acrylonitrile-butadiene-styrene (ABS) copolymers, linear polyurethanes, acrylonitrile-butadiene rubbers, styrene-butadiene rubbers, chloroprene rubbers, butadiene rubbers, and natural rubbers. Of these, acrylonitrile-butadiene rubbers are particularly useful because they typically have good solubility in the curable precursors. The toughening agents may be used alone or in combination.

[0097] 1. A method for curing a curable precursor of an adhesive composition according to the present disclosure, comprising: providing a curable precursor according to the present disclosure comprising a first portion and a second portion; Providing a first substrate having a contact surface and a second substrate having a contact surface; applying a first portion of a curable precursor onto at least a portion of a contact surface of a first substrate; applying a second portion of the curable precursor onto at least a portion of the contact surface of the second substrate; and curing the curable precursor of the adhesive composition by contacting a first portion of the curable precursor on the contact surface of the first substrate with a second portion of the curable precursor on the contact surface of the second substrate. Further disclosed herein is a method comprising:

[0098] The first and second portions of the curable precursor may be applied onto the contacting surfaces of the first or second substrates, respectively, by using any suitable conventional coating process technique.

[0099] The weight ratio of the amount of the first portion to the amount of the second portion applied onto the contact surfaces of the first and second substrates may be from 20:1 to 1:1. Preferably, the weight ratio of the amount of the first portion to the amount of the second portion is from 15:1 to 5:1, more preferably from 12:1 to 8:1, and most preferably 10:1.

[0100] After applying the first and second portions of the curable precursor onto at least a portion of the contact surface of the first and second substrates, respectively, the first portion of the curable precursor on the contact surface of the first substrate is contacted with the second portion of the curable precursor on the contact surface of the second substrate. This contact causes the curable precursor to harden. Typically, it is not necessary to heat the first and second portions of the curable precursor while they are in contact with each other.

[0101] After contacting the vanadium compound and the β-dicarbonyl compound contained in the two different portions of the curable precursor, in the presence of air, the vanadium compound and the β-dicarbonyl compound contained in the curable precursor form in situ a peroxide initiator, which initiates the radical (co)polymerization of the radical (co)polymerizable compound of the curable precursor.

[0102] Curing does not begin until the first and second parts of the curable precursor are brought together, and upon joining, the two parts of the curable precursor spontaneously mix and cure by diffusion. The curable precursor can be cured substantially uniformly without any physical mixing process.

[0103] Curing may be carried out at a temperature below 50° C., or at a temperature up to 40° C. or up to 30° C., or at room temperature (23° C.). Preferably, curing is carried out at room temperature (23° C.).

[0104] Typically, after a curing time of 5 minutes at room temperature (23° C.), an adhesive composition having an adhesive strength of at least 0.1 MPa is obtained. Preferably, an adhesive strength of at least 0.1 MPa is obtained after a curing time of 3 minutes, 1 minute, or 0.5 minutes. The adhesive strength (overlap shear strength, OLS) of the cured composition after a curing time of at least 48 hours at room temperature (23° C.) can be at least 2 MPa, or at least 3 MPa, or at least 4 MPa, or at least 5 MPa, measured according to the test method described in the experimental section. The curing time can be adjusted as desired depending on the target application and manufacturing requirements.

[0105] The cured compositions made by the processes disclosed herein may have an overlap shear strength (OLS) at room temperature (23° C.) in the range of 2.0 MPa to 10.0 MPa, or 2.0 MPa to 8.0 MPa, when measured according to the test methods described in the Experimental Section.

[0106] The cured compositions made by the processes disclosed herein may have an overlap shear strength (OLS) at 180°C of at least 1.0 MPa, at least 1.5 MPa, at least 2.0 MPa, or at least 3.0 MPa, when measured according to the test methods described in the Experimental Section.

[0107] The cured compositions made by the processes disclosed herein may have an overlap shear strength (OLS) at 180° C. in the range of 1.0 MPa to 5.0 MPa, or 2.0 MPa to 5.0 MPa, as measured according to the test methods described in the Experimental Section.

[0108] The curable precursor may contain an additional initiator (e) for radical (co)polymerization of the radical (co)polymerizable compound in addition to the initiator formed in situ by the reaction between the vanadium compound and the β-dicarbonyl compound. The additional initiator is included in the second part of the curable precursor. By adding an initiator, the curing time can be reduced.

[0109] The curable precursors disclosed herein can be used to laminate steel sheets for motor cores in electric motors for vehicles such as automobiles. The curable precursors disclosed herein can also be used in electronic device and display assemblies. EXAMPLES

[0110] Unless otherwise stated or readily apparent from the context, all parts, percentages, ratios, etc. in the examples are by weight.

[0111] [Table 1]

[0112] Test Method Overlap shear strength The overlap shear strength test of the examples and comparative examples was carried out using SPCC-SB steel plates (cold rolled steel) available from Test Piece Co., Ltd. (Kanagawa, Japan) with dimensions of 1.6 mm x 25 mm x 100 mm. The plates were wiped with isopropyl alcohol to remove grease and / or particle contamination from the surface. The overlap area between the two plates was 25 mm x 12.5 mm. Approximately 30 mg of adhesive precursor composition-Part A (i.e., the first part of the curable precursor of the adhesive composition) was dispersed within the overlap area of ​​the surface of the first plate according to the combination shown in Table 3, and a thin layer of approximately 3 mg of adhesive precursor composition-Part B (i.e., the second part of the curable precursor of the adhesive composition) was coated within the overlap area of ​​the surface of the second plate using a cotton swab. The two areas of the plates with adhesive precursor were then brought into contact with each other such that the Part A composition was in contact with the Part B composition. Two binder clips were used to hold the two plates together. The adhesive precursor composition between the plates was cured at room temperature for 2 days to form overlap shear specimens. The overlap shear strength test was performed using a conventional tensile tester (Tensilon Universal Tester RTC1325A, A&D Co., Ltd., Tokyo, Japan) by attaching both ends of the plates of the overlap shear specimen to the clamps of the tensile tester, and then applying a shear force to the specimen with a clamp extension speed of 5 mm / min. The results are shown in Table 3.

[0113] Adhesive Precursor Composition-Part A (PC-A1) Adhesive precursor compositions were prepared according to the formulations shown in Table 1. Each composition was mixed thoroughly to obtain a homogenous solution.

[0114] [Table 2]

[0115] Adhesive precursor composition - Part B (PC-B1) Adhesive precursor compositions were prepared according to the formulations shown in Table 2. Each composition was mixed thoroughly to obtain a homogenous solution.

[0116] [Table 3]

[0117] Examples 1 to 5 (Ex.1 to Ex.5) and Comparative Examples 6 to 9 (CE-6 to CE-9) Examples and Comparative Examples were prepared for use in the overlap shear strength tests described above. Table 3 shows the compositions of PC-A and PC-B used to prepare each Example and Comparative Example. The overlap shear strength results at both room temperature (RT) and elevated temperature (180°C) are also shown in Table 3.

[0118] [Table 4]

Claims

1. A curable precursor of an adhesive composition, comprising: (a) a radical (co)polymerizable compound, (b) a vanadium compound; (c) a β-dicarbonyl compound, and (d) Quaternary ammonium halides A curable precursor comprising:

2. a first portion and a second portion, the first portion comprising the radical (co)polymerizable compound; (i) the first portion comprises the vanadium compound and the quaternary ammonium halide, and the second portion comprises the β-dicarbonyl compound; or (ii) the first portion comprises the β-dicarbonyl compound, and the second portion comprises the vanadium compound and the quaternary ammonium halide; The curable precursor according to claim 1, wherein

3. The second portion is (e) an initiator for radically (co)polymerizing the radically (co)polymerizable compound; The curable precursor of claim 2 further comprising:

4. The curable precursor of claim 3 wherein the initiator is an organic peroxide.

5. The curable precursor of claim 1 , wherein the radically (co)polymerizable compound comprises a (meth)acrylate.

6. 2. The curable precursor of claim 1, wherein the radically (co)polymerizable compound comprises a (meth)acrylate with a functionality greater than one.

7. 2. The curable precursor of claim 1, wherein the radically (co)polymerizable compound comprises a (meth)acrylate having a functionality of at least 2.

8. 2. The curable precursor of claim 1, wherein the radically (co)polymerizable compound comprises a (meth)acrylate having a functionality of at least three.

9. 9. The curable precursor of claim 8, comprising at least 30 percent by weight of said (meth)acrylate having a functionality of at least 3, based on the total weight of said radically (co)polymerizable compounds of said curable precursor.

10. 10. The curable precursor of claim 1 comprising at least 0.01 weight percent of said vanadium compound, based on the total weight of said curable precursor.

11. The β-dicarbonyl compound is represented by the formula 【Chemistry 1】 [In the formula, X １ and X ２ are independently a covalent bond, O, S, 【Chemistry 2】 (In the formula, each R ４ independently represent hydrogen or alkyl having 1 to 18 carbon atoms; R １ and R ２ independently represent a hydrocarbyl or substituted hydrocarbyl group having 1 to 18 carbon atoms; R ３ represents hydrogen, or a hydrocarbyl or substituted hydrocarbyl group having 1 to 18 carbon atoms; Or, R １ , R ２ , or R ３ any two of these may be taken together to form a five- or six-membered ring.

2. The curable precursor of claim 1, wherein the curable precursor is represented by:

12. The curable precursor of claim 11, wherein the β-dicarbonyl compound comprises a dialkyl 2-acetylsuccinate diester having from 8 to 14 carbon atoms.

13. The curable precursor of claim 1 , wherein the vanadium compound comprises vanadyl acetylacetonate.

14. The curable precursor of claim 2 , wherein the first portion of the curable precursor further comprises a monofunctional (meth)acrylate.

15. The curable precursor of claim 1 further comprising a hydrophobic solvent.

16. The curable precursor of claim 1 further comprising a thixotropic agent.

17. A method for curing a curable precursor of the adhesive composition according to any one of claims 2 to 16, comprising the steps of: Providing a curable precursor comprising a first part and a second part according to any one of claims 2 to 16; Providing a first substrate having a contact surface and a second substrate having a contact surface; applying the first portion of the curable precursor onto at least a portion of the contact surface of the first substrate; applying the second portion of the curable precursor onto at least a portion of the contact surface of the second substrate; and curing the curable precursor of the adhesive composition by contacting the first portion of the curable precursor on the contact surface of the first substrate with the second portion of the curable precursor on the contact surface of the second substrate. A method comprising:

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