How to glue the board

Abstract

A method of bonding first and second substrates, each having a respective bonding surface to be bonded to one another, comprising the steps of: (a) applying a redox-active metal catalyst primer to at least the bonding surface of the first substrate to form a primed surface, (b) activating the primed bonding surface of the first substrate by exposing the primed bonding surface to actinic radiation, (c) applying a UV-curable anaerobic adhesive to the activated bonding surface of the first substrate and / or the bonding surface of the second substrate, (d) bonding the bonding surfaces with the UV-curable anaerobic adhesive between them, and (e) exposing the UV-curable anaerobic adhesive between the bonding surfaces to actinic ultraviolet radiation. The method is particularly suited to obtaining good tensile shear strength adhesion to electrical substrates coated with insulating varnish.

Description

[Technical field]

[0001] The present invention relates to a method for bonding substrates. [Background technology]

[0002] (Brief Description of Related Art) It is known in the adhesives industry that certain substrates are difficult to bond to. This can be due to a variety of factors, including the low surface energy / low surface tension properties of the materials of the substrates being bonded.

[0003] To bond such difficult to bond materials, various approaches are commonly used. For example, adhesive compositions are specially formulated to bond such substrates. Additionally or alternatively, primers are used. A primer is applied to the substrate before the adhesive is applied. Additionally or alternatively, surface treatments of the substrate are used to enhance adhesion, often through physical effects such as roughening the substrate surface to facilitate adhesion, or through chemical treatments such as acids.

[0004] One type of substrate that can be difficult to bond to is a substrate that has a coating on it, this means that the material that forms the substrate can be bonded easily, but the coated material can be more difficult to bond due to the different properties of the coating.

[0005] Of particular interest in the context of the present invention is the case when the coating is applied as an electrically insulating coating. In the context of the present invention, the term "insulating" refers to electrical insulation.

[0006] For example, the substrate may be formed of a metal such as steel, which is relatively easy to bond to. However, the coating makes bonding of the substrate very difficult. Moreover, removing at least a portion of the coating (e.g., using the techniques described above) would allow bonding, but would result in the loss of the desirable properties imparted by the coating, which is undesirable. In particular, it is undesirable to remove a coating applied for electrical insulation purposes, as loss of such insulation can lead to electrical shorts and shock hazards, and related hazards such as fire, reduced performance, and injury.

[0007] Despite the state-of-the-art solutions to these problems proposed, it is desirable to provide alternative solutions so that more choices are available to the end user. Summary of the Invention [Means for solving the problem]

[0008] In one aspect, the present invention provides a method as claimed.

[0009] It will be appreciated that only one of the substrates to be bonded may be a substrate that is difficult to bond to, such as a coated substrate, such as a substrate coated for electrical insulation purposes, etc. In the present invention, such substrates / coatings may be referred to as e-coats, e-coated, e-coatings, etc.

[0010] In the electrical industry, such coatings are often used on parts of electrical / electronic components. The composition applied to form the coating is often referred to as a varnish. In this regard, the present invention relates to the adhesion of substrates, particularly electrical substrates, coated with such varnishes. In many cases, the varnish confers electrical insulating properties to the substrate. Typically, electrical substrates are made of metal, such as steel, and are insulated using such coatings.

[0011] Of particular interest to the present invention are coated substrates that function using electromagnetic induction.

[0012] Such coated substrates often form part of electrical devices, including motors, generators, transformers, sensors, and other devices that function by electromagnetic induction. The coating provides suitable electrical insulation and has sufficient structural integrity to permit operation of the electrical equipment.

[0013] Such insulating coatings may be applied by encapsulation, casting, or potting onto a suitable substrate.

[0014] The coatings are typically epoxy resins, phenolic resins (including phenol / formaldehyde resins), and polyurethane resins.

[0015] Silicon steel, also known as electrical steel, is steel with the addition of silicon. The addition of silicon to steel increases the electrical resistance, improves the ability of magnetic fields to penetrate the steel, and reduces the hysteresis losses in the steel. Silicon steel is used in many electrical applications where electromagnetic fields are important, such as electric stators / rotors, motors, coils, magnetic coils, and transformers.

[0016] Steel used for electrical applications is also called laminated steel, silicon electrical steel, silicon steel, core plate steel, C5 core plate, or transformer steel.

[0017] Steel types include GO grain oriented steel, NGO non-oriented steel, CRML cold rolled motor laminated steel etc.

[0018] Electrically insulating coatings are coatings that insulate steel, such as silicon steel, and are often pigmented.

[0019] Some of the insulation classes for electrical steel insulating coatings are listed below:

[0020] C3 / EC-3: Unfilled, organic-based varnishes with enhanced punching power and excellent thermal insulation. Typical applications for these coatings are small motors, transformers and transmitters. The special C3 coating is a self-adhesive varnish that adheres to the entire cross section, even in complex geometries, and therefore offers the highest level of adhesion properties. This allows electrical equipment manufacturers to insulate and bond steel stacks in one step, while preserving the magnetic properties and excellent mechanical strength of the electrical steel sheets.

[0021] C5 / EC-5: These are filled organic and inorganic based varnishes, ideal for improving insulating properties, annealing resistance and weldability. Typical applications for these coatings are machines that undergo processes such as welding, aluminum-die casting or annealing.

[0022] C6 / EC-6: These are organic and inorganic based varnishes with high loadings that improve the insulating properties and also provide the required resistance to pressure. Typical applications for these coatings are medium and large machinery with high resistance to pressure and temperature.

[0023] [Table 1]

[0024] The method of the present invention is suitable for use with all classes of insulating coatings listed above. The method of the present invention utilizes a primer, an anaerobic / UV anaerobic adhesive, and a UV light source. In this method, the primer is applied to the areas to be bonded and then activated with UV light. The UV anaerobic adhesive is applied and the joint is assembled and secured with clamps as needed. The ends of the (clamped) joint are exposed to UV light. This method can be used to bond e-coated substrates, such as e-coated C5 substrates.

[0025] The use of a UV-activated primer in conjunction with an anaerobic / UV anaerobic adhesive significantly improves the bond strength in certain applications, such as bonding e-coat steel to another e-coat steel substrate. For example, the method of the present invention can be used to achieve stronger adhesion when at least one of the substrates being bonded is a coated metal, such as coated steel, e.g. e-coat C5 steel. Performance is improved when compared to the use of a UV anaerobic / UV anaerobic plus primer system.

[0026] Substrates that can be bonded by the method of the present invention include e-coated steel. Examples of commercially available e-coated steel include Waelzholz M310-65A according to EN10106 - supplied with mill certificate to EN10204-3.1 - Waelzholz 2xAN8-C5 classification - thickness 2.0-6.0 μm per side (100 mm x 25 mm x 0.5 mm).

[0027] Coatings are filled organic and inorganic based varnishes that are typically applied to steel to improve insulating properties, resistance to annealing, and / or improve weldability. Typical applications for these coatings are on machines that undergo processes such as welding, aluminum-die casting, or annealing. Coatings may be epoxy based.

[0028] The method of the present invention is suitable for bonding substrates where the coated substrates need to be bonded together, for example in the form of a stack or array, for example in the assembly of electric motor components such as laminate stacks. Such coated substrates may be C5e-coated substrates.

[0029] Using a UV-activated primer in conjunction with an anaerobic / UV anaerobic adhesive significantly improves the bond strength between the e-coat and substrates such as e-coat C5 steel compared to using a UV anaerobic / UV anaerobic plus primer system.

[0030] For example, the method of the present invention can be used to bond the individual components that form the laminate stack of an electric motor, for example, the stack in an electric motor may consist of individual stators or rotors bonded together.

[0031] Generally, the same radiation parameters can be used for both activating the primer and UV curing the anaerobic adhesive.

[0032] The present invention relates to a method for bonding together a first substrate and a second substrate having respective bonding surfaces to be bonded together, (a) applying a redox-active metal catalyst primer to an adhesion surface of at least a first substrate to form a primed surface; (b) activating the prime adhesive surface of the first substrate by exposing the prime adhesive surface to actinic radiation; (c) applying a UV-curable anaerobic adhesive to the activated adhesive surface of the first substrate and / or the adhesive surface of the second substrate; (d) bonding the adhesive surfaces together with a UV-curable anaerobic adhesive therebetween; and (e) exposing the UV-curable anaerobic adhesive between the mating surfaces to actinic UV radiation.

[0033] In the method of the present invention, optionally, step (a) comprises applying a redox-active metal catalyst primer to the bonding surfaces of each of the first substrate and the second substrate to form respective primed surfaces; Step (b) involves activating the prime adhesive surfaces of each of the first and second substrates by exposing the respective adhesive surfaces to actinic radiation.

[0034] Preferably, step (c) comprises applying a UV curable anaerobic adhesive to the activated adhesive surface of the first substrate and to the activated adhesive surface of the second substrate.

[0035] The actinic radiation in step (b) may have a wavelength of from about 10 nm to about 10,000 nm, such as from 100 to 700 nm, optionally from 300 to 400 nm, such as from 360 to 380 nm. One useful range is from 100 to 400 nm.

[0036] The exposure time to actinic radiation in step (b) may be from 1 to 300 seconds, such as from 1.5 to 200 seconds, optionally from 2 to 100 seconds, such as from 5 to 60 seconds.

[0037] The intensity of the actinic radiation in step (b) is 1 to 5000 mW / cm 2 , e.g. 50-900mW / cm 2 , preferably 100 to 800 mW / cm 2 , e.g. 120-700mW / cm 2 may be also possible.

[0038] The total energy to which the prime adhesive surface of the first substrate and / or the prime adhesive surface of the second substrate are exposed during step (b) is preferably 1 to 300,000 mJ / cm 2 , for example 100 to 200,000 mJ / cm 2 , appropriately 250~100000mJ / cm 2 , e.g. 0.5 J / cm 2 ~40J / cm 2 It is.

[0039] The actinic radiation in step (e) may have a wavelength of from about 10 nm to about 10,000 nm, such as from 100 to 700 nm, optionally from 300 to 400 nm, such as from 360 to 380 nm. One useful range is from 100 to 400 nm.

[0040] The exposure time to actinic radiation in step (e) may be from 1 to 300 seconds, such as from 1.5 to 200 seconds, optionally from 2 to 100 seconds, such as from 5 to 60 seconds.

[0041] Optionally, the intensity of the actinic radiation in step (e) is between 1 and 5000 mW / cm 2 , e.g. 50-900mW / cm 2 , appropriately 100~800mW / cm2 , e.g. 120-700mW / cm 2 It is.

[0042] The total energy to which the UV-curable anaerobic adhesive is exposed during step (e) is 1 to 300,000 mJ / cm 2 , for example 100 to 200,000 mJ / cm 2 , appropriately 250~100000mJ / cm 2 , e.g. 0.5 J / cm 2 ~40J / cm 2 It could be.

[0043] The redox-active metal catalyst primer can include a redox-active metal catalyst selected from cobalt (II) naphthenate, copper carbonate, copper (II) acetylacetonate, silver nitrate, vanadium (III) acetylacetonate, iron (II) naphthenate, copper disodium ethylenediaminetetraacetate (EDTA·2Na·Cu(II)), vanadyl acetylacetonate, iron (II) acetate, or combinations thereof.

[0044] Suitably, the redox-active metal catalyzed primer comprises a copper-based primer, for example, the redox-active metal catalyzed primer comprises at least one CuII salt, which may be selected from Cuacac (copper(II) acetylacetonate) and copper(II) ethylhexanoate, such as copper(II) 2-ethylhexanoate, and combinations thereof.

[0045] The redox-active metal catalyst primer may include a redox-active metal catalyst dissolved in a reactive solvent, such as a (meth)acrylate monomer, such as hydroxypropyl methacrylate ("HPMA"), methacrylic acid, or propylene glycol dimethacrylate, and combinations thereof.

[0046] Optionally, the redox-active metal catalyst primer includes an organic solvent, such as acetone or dichloromethane.

[0047] Desirably, the redox active metal catalyst primer comprises 0.01 to 0.4%, such as 0.05 to 0.4%, such as 0.1% to 0.3% of an active redox active metal catalyst, such as a copper salt, based on the total weight of the solution.

[0048] The substrate may be a substrate having a coating thereon, and further, the coating may be a coating applied by curing a curable coating composition on the substrate.

[0049] The substrate is optionally steel, the substrate forming part of an electric motor.

[0050] The coating may be formed from epoxy resins, phenolic resins (including phenol / formaldehyde resins), polyurethane resins, and combinations thereof.

[0051] <Polymerizable (meth)acrylate ester monomer> Suitable (meth)acrylate monomers for use in the anaerobic curable compositions described herein include H2C=CGCO2R 4 (wherein G is hydrogen, halogen, or an alkyl group having 1 to about 4 carbon atoms; R 4 is selected from an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl, or aryl group having 1 to about 16 carbon atoms, any of which may optionally be substituted or interrupted with silane, silicon, oxygen, halogen, carbonyl, hydroxyl, ester, carboxylic acid, urea, urethane, carbonate, amine, amide, sulfur, sulfonate, sulfone, etc., and may be selected from a wide variety of materials such as those represented by the formula:

[0052] One class of monomers suitable for use in the present invention includes acrylate esters having the general formula: [ka] In the formula, R is hydrogen, lower alkyl containing 1 to 4 carbon atoms, hydroxyalkyl containing 1 to 4 carbon atoms, and [ka] represents a radical selected from the group consisting of R' is a radical selected from the group consisting of hydrogen, halogen, and lower alkyl having 1 to 4 carbon atoms; R″ is hydrogen, -OH, and [ka] is a radical selected from the group consisting of m is an integer at least equal to 1, e.g., 1 to 8 or more, e.g., 1 to 4; n is an integer equal to at least 1, for example, 1 to 20 or more; p is either 0 or 1.

[0053] Examples of polymerizable (meth)acrylate ester monomers that can be used according to the present invention and correspond to the above general formula include, but are not limited to, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, di(pentamethylene glycol) dimethacrylate, tetraethylene diglycerol diacrylate, diglycerol tetramethacrylate, tetramethylene dimethacrylate, ethylene dimethacrylate, neopentyl glycol diacrylate, and trimethylolpropane triacrylate.Of these, preferred monomers are triethylene glycol dimethacrylate and polyethylene glycol dimethacrylate.

[0054] [ka]

[0055] Representative examples of polyacrylate esters corresponding to the above general formula include di-, tri-, and tetraethylene glycol dimethacrylate, di(pentamethylene glycol) dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol di(chloroacrylate), diglycerol diacrylate, diglycerol tetramethacrylate, butylene glycol dimethacrylate, neopentyl glycol diacrylate, and trimethylolpropane triacrylate.

[0056] While di- and other polyacrylate esters have been found to be particularly desirable, particularly the polyacrylate esters described in the previous paragraph, monofunctional acrylate esters (esters containing one acrylate group) can also be used. When working with monofunctional acrylate esters, it is highly preferred to use esters that have relatively polar alcohol moieties. Such materials are less volatile than low molecular weight alkyl esters, and more importantly, the polar groups provide intermolecular attractions during and after cure, producing more desirable cure properties and a more durable sealant or adhesive.

[0057] Preferably, the polar group is selected from the group consisting of labile hydrogen, heterocyclic, hydroxy, amino, cyano, and halo polar groups. Representative examples of compounds within this category include cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, t-butylaminoethyl methacrylate, cyanoethyl acrylate, chloroethyl methacrylate, and the like.

[0058] Another preferred class of monomers is prepared by the reaction of monofunctional substituted alkyl or aryl acrylate esters containing an active hydrogen atom on the functional group substituent. This monofunctional acrylate terminated material is reacted with an organic polyisocyanate in the appropriate proportions to convert all of the isocyanate groups to urethane or ureido groups.

[0059] Additional (meth)acrylate monomers suitable for use in the present invention include di- or trifunctional (meth)acrylates such as polyethylene glycol di(meth)acrylate, tetrahydrofuran (meth)acrylate and di(meth)acrylate, hydroxypropyl (meth)acrylate ("HPMA"), hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), tetraethylene glycol dimethacrylate, dipropylene glycol dimethacrylate ("PEN"), tetramethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), tetramethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), tetramethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), tetramethylolpropane tri(meth)acrylate ("TMPTMA"), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate ("TRIEGMA"), diethylene glycol dimethacrylate, dipropylene ...DIEGMA"). Examples of suitable methacrylates include ethylene glycol dimethacrylate, di(pentamethylene glycol) dimethacrylate, tetraethylene diglycol diacrylate, diglycerol tetramethacrylate, tetramethylene dimethacrylate, ethylene dimethacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, and bisphenol A mono- and di(meth)acrylates such as ethoxylated bisphenol A (meth)acrylate ("EBIPMA"), and bisphenol F mono- and di(meth)acrylates such as ethoxylated bisphenol F (meth)acrylate.

[0060] Still other (meth)acrylate monomers that can be used in the present invention include the silicone (meth)acrylate moieties ("SiMA") as taught and claimed in U.S. Pat. No. 5,605,999 (Chu), the disclosure of which is expressly incorporated herein by reference.

[0061] The polymerizable (meth)acrylate ester monomer may be present in the composition in an amount of from about 10 to about 90 weight percent, suitably from about 30 to about 70 weight percent, based on the total weight of the composition.

[0062] <Redox active metal catalyst> Curing of the anaerobically curable composition can be initiated by a redox-active metal catalyst comprising a transition metal when the anaerobically curable composition is contacted with a plastic substrate under anaerobic conditions The redox-active metal catalyst enhances the cure strength, cure speed, and combinations thereof of the compositions described herein.

[0063] The transition metal included in the redox-active metal catalyst can be titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, silver, vanadium, molybdenum, ruthenium, and combinations thereof. Furthermore, the transition metal can be provided in the form of a salt. For example, the transition metal salt can be selected from cobalt (II) naphthenate, copper carbonate, copper (II) acetylacetonate, silver nitrate, vanadium (III) acetylacetonate, and combinations thereof. Preferably, the redox-active metal catalyst is iron (II) naphthenate, copper disodium ethylenediaminetetraacetate (EDTA·2Na·Cu(II)), or copper naphthenate, vanadium acetylacetonate, vanadyl acetylacetonate, iron (II) acetate, or combinations thereof.

[0064] The redox-active metal catalyst may be included in the composition in an amount of from about 0.0001 to about 2, preferably from about 0.0002 to about 0.5, weight percent based on the total weight of the composition.

[0065] <Peroxide> Peroxides may function as a free radical source to initiate free radical cure of the anaerobic curable compositions described herein. The anaerobic curable compositions described herein include, but are not limited to, peroxides having a half-life of 10 hours at temperatures between about 80° C. and 140° C., such as cumene hydroperoxide ("CHP"), paramenthane hydroperoxide, t-butyl hydroperoxide ("TBH"), and t-butyl perbenzoate. Several well-known free radical polymerization initiators may be incorporated. Other suitable peroxides include benzoyl peroxide, dibenzoyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, diacetyl peroxide, butyl 4,4-bis(t-butylperoxy)valerate, p-chlorobenzoyl peroxide, t-butylcumyl peroxide, t-butyl perbenzoic acid, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxyhex-3-yne, 4-methyl-2,2-di-t-butylperoxypentane, and combinations thereof.

[0066] Additionally, hydroperoxides derived from hydrocarbons having a chain length of 3 to 18 carbon atoms, such as cumene hydroperoxide, tert-butyl hydroperoxide, methyl ethyl ketone hydroperoxide, diisopropylbenzene hydroperoxide, can be included in the compositions described herein.

[0067] The peroxide may be present in the composition in an amount of about 0.5 to about 10 weight percent, suitably about 1 to about 5 weight percent, based on the total weight of the composition.

[0068] Suitable compositions that can be used in the present invention include anaerobic curable compositions that include (i) one or more polymerizable (meth)acrylate ester monomers, (ii) a redox-active metal catalyst, (iii) saccharin or a saccharin derivative, (iv) a peroxide, and (v) a benzoyl-functionalized compound, and preferably the composition does not gel after about 24 hours of storage at room temperature. Each of components (i) to (v) of the present invention is a different component. For example, the redox-active metal catalyst is not a benzoyl-functionalized compound. For example, the benzoyl-functionalized compound is not a peroxide.

[0069] <Benzoyl-functionalized compounds> The inclusion of benzoyl-functionalized compounds in the compositions of the present invention is desirable to stabilize the compositions, for example, to stabilize redox-active metal catalysts.

[0070] Benzoyl-functionalized compounds can be photoinitiators. For example, photoinitiators available from BASF Chemical in Germany under the trade names "IRGACURE" and "DAROCUR" are preferred, specifically "IRGACURE" 184 (1-hydroxycyclohexyl phenyl ketone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one), 369 (2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone), 500 (combination of 1-hydroxycyclohexyl phenyl ketone and benzophenone), 651 (2,2-dimethoxy-2-phenylacetophenone), and 707 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one). DAROCUR 1173 (2-hydroxy-2-methyl-1-phenyl-1-propane) and 4265 (2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one). Of course, combinations of these materials may also be used in the present invention. The structures of the preferred photoinitiators are shown below.

[0071] [ka]

[0072] The benzoyl-functionalized compound can be included in the composition in an amount of about 0.1 to about 5 weight percent, suitably about 0.5 to about 2 weight percent, based on the total weight of the composition. Desirably, the benzoyl-functionalized compound is present in an excess amount relative to the redox-active metal catalyst. On a weight basis, based on the total weight of the composition, the benzoyl-functionalized compound is desirably present in an excess amount relative to the redox-active metal catalyst. For example, the benzoyl-functionalized compound is desirably present in an excess amount relative to the redox-active metal catalyst in a ratio of at least about 3:1, such as at least about 4:1, or even at least about 5:1.

[0073] <Optional ingredients> The anaerobic curable compositions disclosed herein may include additional components, provided that the additional components do not interfere with the functionality of the components described above.

[0074] For example, acrylic acid may be included in the composition in an amount of from about 0 to about 20 weight percent, suitably from about 1 to about 10 weight percent, based on the total weight of the composition, to enhance cure and adhesion.

[0075] A (meth)acrylate oligomer can be optionally further included in the composition. The (meth)acrylate oligomer can be included to improve the fully cured peel strength of the compositions described herein. For example, a polyurethane oligomer capped with a (meth)acrylate can be included. A variety of commercially available urethane (meth)acrylate oligomer resins are known. Suitably, this component is or includes a block resin as described in U.S. Pat. No. 4,309,526, which includes at least one polyether block derived from a polyether polyol and at least one hard block derived from an aromatic or alicyclic diisocyanate and an aromatic or alicyclic polyol. Particularly preferred are resins in which the polyether polyol is an aliphatic polyether having a number average molecular weight of about 400 to about 10,000, more suitably about 700 to about 3,500.

[0076] When included, the (meth)acrylate oligomer may be present in the anaerobically curable composition in an amount of from about 5 to about 90 weight percent, suitably from about 10 to about 50 weight percent, based on the total weight of the composition.

[0077] Optionally, an amine can be included in the composition to polymerize the monomers in the absence of oxygen and to prevent polymerization of the monomers in the presence of oxygen.

[0078] The nature of the amine is not critical for the purposes of the anaerobic curable compositions disclosed herein, i.e. primary, secondary, tertiary, aliphatic or aromatic amines can be used. For example, primary aliphatic amines such as ethyl, n-butyl, n-propyl, isopropyl, n-hexyl, t-butylamine, etc. can be suitably used. Also, primary aromatic amines such as aniline, p-toluidine, p-naphthylamine, xylidine, benzylamine, p-benzylaniline, etc. can be used. Aliphatic or aromatic secondary amines can also be used. Typical examples of acceptable secondary amines include diethylamine, dipropylamine, diisopropylamine, diphenylamine, N-phenylbenzylamine and N-allylaniline.

[0079] Tertiary amines are organic amines in which all three valencies of the nitrogen atom are satisfied by carbon atoms. Tertiary amines are also suitable for use in the compositions described herein. The carbon atoms of tertiary amines may be part of unsubstituted or hydroxyl-substituted alkyl, carbocyclic or heterocyclic groups. In general, trialkylamines and dialkylanilines are most suitably used. However, alkaloids and other compounds within the above definition are also suitable for the present invention. Examples of various tertiary amines used are triethylamine, tripropylamine, tributylamine, triamylamine, triphenylamine, dimethylaniline, ethyldiethanolamine, triethanolamine and piperidine.

[0080] In general, amines suitable for use in the compositions described herein can be represented by the formula R″-R-NH, where R″ is an aliphatic or aromatic hydrocarbon group containing up to about 14 carbon atoms, preferably up to about 8 carbon atoms, and R is either hydrogen or R. Of course, either R″ or R can include any substituent or bond, hydrocarbon or otherwise, which does not adversely affect the condensation product for the purposes disclosed herein.

[0081] The amines used in the compositions described herein are suitably liquid at room temperature for ease of handling and mixing, although gaseous and solid compounds can also be used dispersed in the monomer.

[0082] The anaerobic curable compositions disclosed herein can include a variety of secondary and tertiary organic amines, preferably secondary aromatic amines.

[0083] The amine, preferably a secondary aromatic amine, may be included in the composition in an amount up to about 5 weight percent, preferably from about 0.001 to about 2 weight percent, based on the total weight of the composition.

[0084] A chelating agent can be optionally further included in the composition. A chelating agent, such as ethylenediaminetetraacetic acid (EDTA), can be used in the anaerobic curable compositions described herein to sequester metal ions. For example, the chelating agent can be included in the composition in an amount of about 0.0001 to about 1 weight percent, suitably about 0.0002 to about 0.5 weight percent, based on the total weight of the composition.

[0085] Optionally, a free radical stabilizer can be included in the composition. Phenols such as hydroquinone, benzoquinone, naphthoquinone, anthraquinone, butylated hydroxytoluene, and p-methoxyphenol can be used to prevent premature polymerization due to decomposition of peroxides and formation of free radicals. For example, the free radical stabilizer can be included in the composition in an amount of about 0.0001 to about 2 weight percent, suitably about 0.0002 to about 0.5 weight percent, based on the total weight of the composition.

[0086] Silica and inorganic fillers can also be included in the composition if necessary. Silica can be added to increase the viscosity, i.e., thixotropy, of the composition. This helps with non-flowing and non-sagging properties, such as when used in gasket seals. Preferably, when silica and / or inorganic fillers are included in the composition, they are included in an amount of up to about 10 weight percent, preferably up to about 5 weight percent, based on the total weight of the composition.

[0087] Additional resins may also be included in the composition as needed, including, but not limited to, polyesters, polyurethanes, etc. These resins may be included in the composition in an amount up to about 50 weight percent, suitably up to about 20 weight percent, based on the total weight of the composition. [Brief description of the drawings]

[0088] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] Figure 1 is a graph of tensile shear strength (N / mm2) for epoxy coated C5E steel lap shear. Cure time was 24 hours. The tensile shear strength was tested using various adhesive / lap shear treatment / activator / UV combinations, as shown on the x-axis, where "AA" = anaerobic adhesive, "Act" = activator, "UV" = UV exposure, "laps" = lap shear, and "Hy" = hybrid. All numbers on the x-axis are product codes for commercially available Loctite® products. These Loctite® products are available from Henkel Ireland and other Henkel sites.

[0089] [Diagram 2] FIG. 2 is a plot of the tensile shear strength (N / mm2) for the indicated substrates, showing both comparative results (without the method of the invention, labeled "Loctite AA3510 + UV only") and results using the method of the invention (labeled "4-step primer / UV process"). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0090] <Detailed Description> Below is described a series of experiments highlighting methods for improving the adhesion of electrically insulating coated substrates, such as the adhesion of an e-coated steel substrate to another e-coated steel substrate.

[0091] The bonding method according to the invention was carried out. Comparative tests / methods were also carried out.

[0092] The method of the present invention includes bonding together a first substrate and a second substrate having respective bonding surfaces that are bonded to each other; (a) applying a redox-active metal catalyst primer to an adhesion surface of at least a first substrate to form a primed surface; (b) activating the prime adhesive surface of the first substrate by exposing the prime adhesive surface to actinic radiation; (c) applying a UV-curable anaerobic adhesive to the activated adhesive surface of the first substrate and / or the adhesive surface of the second substrate; (d) bonding the adhesive surfaces together with a UV-curable anaerobic adhesive therebetween; and (e) exposing the UV-curable anaerobic adhesive between the mating surfaces to actinic ultraviolet light.

[0093] One of the irradiation sources used was a Light Hammer® 6UV system, which is a device that emits ultraviolet light.

[0094] In all embodiments of the present invention, when actinic radiation is referred to, it is from a light source specifically positioned to irradiate the substrate to be bonded, for example, the light source is within 1 meter, for example within 30 cm, of the substrate. Thus, exposure refers to exposure to actinic radiation from such a source, and does not include ambient light, such as natural light, light from overhead lighting, etc.

[0095] The substrate bonded was e-coated steel. In particular, substrates of the above materials were used: Waelzholz M310-65A according to EN10106 - supplied with mill certificate according to EN10204-3.1 - Waelzholz 2xAN8-C5 classification. Electrical steel grades according to EN 10106 are standard grades in many conventional applications. These grades are defined as non-oriented, finally annealed electrical steel sheets. The dimensional tolerances are according to EN10106. The lap shears used in the experiments were made of C-5 material, with thicknesses of 2.0-6.0 μm per side and dimensions of 100 mm x 25 mm x 0.5 mm. Mill Test Certificates (MTC) or Mill Test Reports (MTR) are issued by manufacturers to certify the chemical and mechanical properties of a product and its compliance with applicable standards and technical specifications. Usually, mill test certificates comply with the EN10204 standard and relate to steel products. Certification for steel plate rolled in Europe will generally be to EN10204. The actual certificate will vary depending on the plate offered but will be either 3.1 or 3.2. 3.1 or 3.2 MTC means that the test has been carried out on the actual plate or heat sold and a Mill Test Certificate (MTC) will be affixed to the plate. AN8 is the coating applied by Waelzholz.

[0096] As mentioned above, coatings are filled with organic and inorganic based varnishes and are usually applied to steel to improve its insulating properties, resistance to annealing, and / or improve weldability. Typical applications for these coatings are on machines that undergo processes such as welding, aluminium-die casting or annealing.

[0097] The UV-curable anaerobic adhesive used in the tests was Loctite® AA3510. ("AA" = anaerobic adhesive)

[0098] The redox active metal catalyzed primer used was Loctite® 7091. It contains an organocopper compound and a reactive methacrylate monomer in a solvent.

[0099] The tests were conducted according to the following criteria: (i) ASTM D1002-05 (October 1, 2005) Strength properties of adhesives under shear with tensile load (metal to metal (ii) ASTM D3163 Strength properties of rigid plastic lap shear joints subjected to tensile loading (iii) ISO 4587 Adhesives - Determination of tensile lap shear strength of high strength adhesive bonds 5.1.4 DIN EN 1465 Adhesives - Determination of tensile lap shear strength of rigid-to-rigid adhesive assemblies

[0100] In the above tests, M310-65A C5 lap shear was used.

[0101] Light Hammer® 6 was used as the actinic UV radiation source. Where indicated, Light Hammer® 6 was used in steps (b) and (e) (Tables 1-3).

[0102] Both lap shears were coated with Loctite® 7091 to prime each surface.

[0103] The primed surfaces were irradiated and activated using a Light Hammer® 6. Each primed surface was irradiated with approximately 5 W / cm 2 The light was irradiated for 60 seconds at an intensity of 10 ... 2 (UVV 2.6 W / cm 2 , UVA1.8W / cm 2 , UVB0.7W / cm 2 , UVC 0.1W / cm 2 ).

[0104] Loctite® 3510 was applied to one of the activated surfaces and the lap shears were bonded together to form a bonded lap shear assembly.

[0105] Where indicated in steps (b) and (e) (Table 4), the UV light source was a Loctite® UVALOC 1000 UV curing chamber. The bonded lap shear assembly was placed in a Loctite® UVALOC 1000 UV curing chamber ("UVALOC 1000"). The bonded assembly was cured at 200 mW / cm at the bond line on both sides of the lap shear. 2 The device was positioned to receive light at an intensity of 100 .mu.m for 60 seconds.

[0106] A series of tests were performed as follows: [Table 2]

[0107] In Table 1 above, the "ACM..." code is the identifying reference / code for each test. "3510" and "7091" are abbreviations for Loctite® products 3510 and 7091, respectively, as discussed above. Each test was performed using three samples, labeled "Samples" 1-3 above. The tensile shear strength results for the three tests were averaged as indicated by "Average." 24 Hours Room Temperature N / mm 2 is the tensile shear strength (N / mm 2 ) is shown.

[0108] ACM-DUB-0031-52-01 is a comparative test in which Loctite® 3510 is applied to the lap shears and the lap shears are clamped together and allowed to sit for 24 hours before testing. In this test, the priming and all UV exposure steps are omitted.

[0109] ACM-DUB-0031-52-02 was prepared by applying Loctite® 3510 to the lap shears, clamping the lap shears together and applying approximately 5 W / cm2 using a Light Hammer® 6. 2This is a comparative test in which the surface is exposed to light at an intensity of 1000 x 1000 for 60 seconds and left for 24 hours before testing. In this test, the priming and UV activation steps of the primed surface are omitted.

[0110] ACM-DUB-0031-52-03 is a comparison test where Loctite® 7091 primer was applied at lap shear. The prime lap shear was approximately 5 W / cm using a Light Hammer® 6. 2 The lap shears are then exposed to an intensity of 10 ...

[0111] ACM-DUB-0031-52-04 applies a Loctite® 7091 primer to the lap shears, primes the lap shears with Loctite® 3510, and the lap shears are clamped together and allowed to sit for 24 hours before testing. All UV exposure steps are omitted for this test.

[0112] Although some results are better than others, the conclusion from Table 1 is that the tensile shear strength is relatively low and it is desirable to achieve a better tensile shear strength. For example, 10 N / mm 2 It is desirable to achieve a tensile shear strength of greater than

[0113] Several further tests were performed, as shown in Table 2, which lists comparative examples and examples of the present invention. [Table 3]

[0114] In Table 2 above, the "ACM..." code is the identifying reference / code for each test. "3510" and "7091" are abbreviations for Loctite® products 3510 and 7091, respectively, as discussed above. Each test was performed using four or five samples, labeled "Samples" 1-5 above. The average of the tensile shear strength results from the four or five tests is given under "Average." 24hr Room Temperature N / mm 2 is the tensile shear strength (N / mm 2 ) is shown.

[0115] ACM-DUB-0031-53-01 is applied with a lap shear of approximately 5W / cm using a Light Hammer® 6. 2 This is a comparative test in which the lap shear is exposed to an intensity of 1000 ppm for 60 seconds. Loctite® 3510 is applied to the lap shear, the lap shear is clamped together and allowed to sit for 24 hours before testing. This test omits priming and omits exposing the lap shear after it is assembled.

[0116] ACM-DUB-0031-53-02 is tested using a Light Hammer® 6 with a lap shear of approximately 5 W / cm 2 This is a comparative test in which the lap shears are irradiated for 60 seconds at an intensity of approximately 5 W / cm2. Loctite® 3510 is applied to the lap shears, the lap shears are clamped together, and the shears are irradiated for 60 seconds at an intensity of approximately 5 W / cm2 using a Light Hammer® 6. 2 The light is exposed to light at an intensity of 1000 for 60 seconds and left to stand for 24 hours before testing. Priming is omitted for this test.

[0117] ACM-DUB-0031-53-03 was prepared by applying Loctite® 7091 primer to the overlap shear section and applying approximately 5 W / cm2 using a Light Hammer® 6. 2 This is a comparative test in which the lap shears are exposed to a 500 psi intensity for 60 seconds. Loctite® 3510 is applied to the lap shears and the lap shears are clamped together and allowed to sit for 24 hours before testing. In this test, exposure of the lap shears after clamping them together is omitted.

[0118] ACM-DUB-0031-53-04 is a test within the scope of this invention, which involves applying Loctite® 7091 primer at lap shear and using a Light Hammer® 6 at a lap shear of approximately 5 W / cm 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate for 60 seconds at an intensity of approximately 5 W / cm using a Light Hammer® 6. 2 The specimen is exposed to light at an intensity of 100 nm for 60 seconds and left for 24 hours before testing, which includes all steps of the method of the present invention.

[0119] Several additional tests were performed, including comparative examples and examples of the invention, as shown in Table 3. [Table 4]

[0120] In Table 3 above, The "ACM..." code is the identifying reference / code for each test. "3510" and "7091" are abbreviations for Loctite® products 3510 and 7091, respectively, listed above. Each test was performed using five samples, labeled "Samples" 1-5 above. The tensile shear strength results for the five tests were averaged as indicated by "Average." 24hr Room Temperature N / mm 2 is the tensile shear strength (N / mm 2 ) is shown.

[0121] ACM-DUB-0031-54-01 is a lap shear test using Light Hammer® 6 at approximately 5 W / cm 2 This is a comparative test in which the lap shears are irradiated for 60 seconds at an intensity of approximately 5 W / cm2. Loctite® 3510 is applied to the lap shears, the lap shears are clamped together, and the shears are irradiated for 60 seconds at an intensity of approximately 5 W / cm2 using a Light Hammer® 6. 2The test is then performed with an intensity of 10000 for 60 seconds and left for 24 hours before testing. Priming is omitted for this test. This test is essentially a repeat of Example ACM-DUB-0031-53-02.

[0122] ACM-DUB-0031-54-02 is a test within the scope of this invention, which involves applying Loctite® 7091 primer at lap shear and using a Light Hammer® 6 at a lap shear of approximately 5 W / cm 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate for 60 seconds at an intensity of approximately 5 W / cm using a Light Hammer® 6. 2 The sample is then exposed to an intensity of 10000 for 60 seconds and left for 24 hours before testing. This test involves all steps of the method of the present invention. This is essentially a repeat of Example ACM-DUB-0031-53-04.

[0123] <Comments / Conclusions> By utilizing the method of the present invention, the skilled artisan can achieve a force of at least 10 N / mm 2 It can be seen that the above-mentioned goal can be achieved. In the tests carried out in accordance with the present invention, the substrates were immediately fixed to each other.

[0124] <Further testing> To demonstrate that a range of intensities can be used, the inventors investigated using different UV light sources. The Light Hammer® 6 is a high intensity UV system. The UVALOC system is lower intensity. The aim was to demonstrate a wide range of intensities (W / cm 2 ) and total exposure energy (J / cm 2 ) with high adhesive strength (>10N / mm 2 The objective of the study was to demonstrate that it was possible to achieve this.

[0125] To do so, they used the Loctite® UVALOC 1000 UV Cure Chamber, a high-performance modular curing system consisting of a cure chamber, lamp housing, and controller. The chamber has four rack levels and can accommodate slide-in trays, making it easy to position parts of various heights at their optimal exposure level. A perforated aluminum plate allows for the placement of customized part holders. The lamps are shielded by a time-controlled shutter, which prevents workers from exposing them to UV light while loading or unloading parts. A door safety switch prevents the door from being opened during exposure. Cure time is controlled by a built-in timer and can be operated in continuous or timed mode. Exposure cycles are triggered by a foot switch, a panel-mounted start button, or via a PLC interface.

[0126] The tests according to the method of the invention and the comparative tests were repeated using the UVALOC1000, with the assembly placed in the UVALOC1000 for both irradiation steps and 200 mW / cm2 for both steps. 2 This resulted in a desirable average tensile shear strength of 14.74 N / mm 2 was achieved.

[0127] [Table 5]

[0128] In Table 4 above, the "ACM..." code is the identifier reference / code for each test. "Loctite 3510" and "Loctite AA3510" are the same product. (AA=Anaerobic Adhesive). Loctite® Products 3510 and 7091 are described above. Each test was performed using three or five samples, labeled "Samples" 1-5 above. The tensile shear strength results for the three / five tests were averaged as indicated by "Average". 24hr Room Temperature N / mm 2 is the tensile shear strength (N / mm2 ) is shown.

[0129] ACM-DUB-0031-57-01 was applied with Loctite® 3510 to the lap shear, the lap shear was clamped together and the assembly was placed in a UVALOC 1000 with an intensity of 200mW / cm 2 This is a comparative test in which the surface is exposed to UV light for 60 seconds and then left for 24 hours before testing. In this test, the steps of priming and UV activation of the primed surface are omitted. This corresponds to test ACM-DUB-0031-52-02.

[0130] ACM-DUB-0031-57-02 is a comparative test in which a Loctite® 7091 primer is applied to the lap shears, Loctite® 3510 is applied to the primed lap shears, and the lap shears are clamped together and allowed to sit for 24 hours before testing. In this test, all UV exposure steps are omitted. This corresponds to test ACM-DUB-0031-52-04.

[0131] ACM-DUB-0031-57-03 was applied with Loctite® 7091 primer to the lap shear and placed on a UVALOC 1000 for 200mW / cm 2 This is a comparative test in which the lap shear is exposed to an intensity of 10 ...

[0132] ACM-DUB-0031-57-04 is placed in lap shear on a UVALOC 1000 and 200mW / cm 2 In a comparative test, Loctite® 3510 was applied to the lap shear, the lap shear was clamped and irradiated using a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2After 60 seconds of exposure to light with an intensity of 10 ...

[0133] ACM-DUB-0031-57-05 is a test within the scope of the present invention, in which Loctite® 7091 primer was applied to lap shear and placed on a UVALOC 1000 at 200 mW / cm 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The test is performed after 60 seconds at an intensity of 100 nm and then after 24 hours of standing. This test includes all steps of the method of the present invention. It corresponds to the test ACM-DUB-0031-53-04.

[0134] ACM-DUB-0031-57-06 was prepared by applying Loctite® 7091 primer to the lap shear and placing the lap shear on a UVALOC 1000 at 200mW / cm 2 This is a comparative test in which the lap shear is exposed to a 60 second exposure at an intensity of 10 ...

[0135] In particular, it has been found that the tensile shear strength can be further improved by using a more directed UV irradiation process on the bonded assembly.

[0136] Further tests were performed (results are shown in Figure 1). Each test was performed on triplicate samples. All samples were cured at room temperature for 24 hours before testing. The average tensile shear strength results for the three tests were calculated and are shown in Figure 1. The appropriate unit for tensile shear testing is N / mm 2Each lap shear was performed with a Waelzholz M310-65A and the overlap (glue area) was 322 mm unless otherwise stated. 2 All lap shears are clamped together unless otherwise stated. The results shown in Figure 1 are the result of the following tests performed in the same order:

[0137] Loctite® AA3510 is used as a control (no UV exposure or priming). Waelzholz M310-65A was received with Loctite® AA3510 applied and cured. As can be seen in Figure 1, the tensile shear strength is 2N / mm 2 Less than and low.

[0138] Loctite® AA3510 and Loctite® 3038-Part B Loctite® 3038 is a two-component acrylic adhesive designed to cure on low activity plastics such as polyethylene. Part B was investigated in combination with Loctite® AA3510 to see if there was an improvement in performance. Loctite® AA3510 and Loctite 3038-Part B were applied to different lap shears in a pair of Waelzholz M310-65A lap shears as received. The lap shears were clamped together and allowed to cure, holding the composition together. As can be seen in Figure 1, the tensile shear strength was 2N / mm 2 It remains low at less than 10%.

[0139] Loctite® AA3510 with UV Prime Lap Shear with Loctite® 3038-Part B Loctite® 3038 is a two-component acrylic designed to cure low activity plastics such as polyethylene. The Part B component was combined with Loctite AA3510 to investigate whether there was an increase in performance. This was done by combining both Waelzholz M310-65A lap shears primed with Loctite® 3038 Part B and curing them at approximately 5 W / cm using a Light Hammer® 6. 2 This test differs from the previous one in that it was exposed to UV light for 60 seconds at a strength of 1.5 N / mm. Loctite® AA3510 was then applied and clamped and allowed to cure for 24 hours. As can be seen in Figure 1, the tensile shear strength was still around 7 N / mm. 2 is low.

[0140] Loctite® AA3510 with Loctite® 7091 UV Prime Lap Shear on both sides Loctite® 7091 primer was applied to the lap shear and the lap shear was placed on a UVALOC 1000 and subjected to 200 mW / cm 2 Loctite® 3510 was applied to the lap shear, the lap shears were clamped together and irradiated from the side with UV light from a UVALOC 1000 at 200 mW / cm for 60 seconds. 2 After irradiating the specimen for 60 seconds at an intensity of 1000 N / mm2, the specimen was clamped and left for 24 hours before testing. This test was performed according to the method of the present invention, and as can be seen from FIG. 1, the tensile shear strength was about 15 N / mm2. 2 and significantly improved.

[0141] Loctite® AA3510 with Plasma Treated Lap Shear Both lap shears were plasma treated prior to bonding using a Tantec™ Plasma Treatment System. The lap shears were exposed to plasma for 0.5 seconds at a distance of 1 cm from the tip. Loctite® AA3510 was applied to one of the pre-treated lap shears and the lap shears were clamped and allowed to cure for 24 hours. As can be seen in Figure 1, the tensile shear strength was 8 N / mm 2Moreover, such treatments tend to remove the insulating coating, which is undesirable.

[0142] Loctite® AA3510 with grit blasted lap shear specimens Both lap shear specimens were grit blasted prior to bonding. Loctite® AA3510 was applied to one of the pretreated lap shears and the lap shear was clamped and allowed to cure for 24 hours. As can be seen in Figure 1, the tensile shear strength was within the target value of 10 N / mm 2 However, such treatment is undesirable since it tends to remove the insulating coating.

[0143] Loctite® HY4070 is a two-component cyanoacrylate / acrylic hybrid that provides excellent adhesion to a variety of plastics and metals. This was used as a control (no UV exposure or priming).

[0144] It has been shown that the use of UV anaerobic primers Loctite® AA7091 and Loctite® 3510 UV treated according to the method of the invention can improve the bond strength on substrates such as e-coated C5 steel, e.g. e-coated steel - Waelzholz M310-65A according to EN10106 - supplied with mill certificate EN10204-3.1 - Waelzholz 2xAN8-C5 classification - 2.0-6.0 μm thick per side (100 mm x 25 mm) substrates.

[0145] E-coated steel bonded to steel using standard adhesive products will have lower strength than bonded using the method of the present invention.

[0146] The tests according to the method of the invention and the comparative tests were repeated using the UVALOC 1000, with the assembly placed in the UVALOC 1000 for both irradiation steps and 200 mW / cm2 for both steps. 2Irradiate for 60 seconds at an intensity of 100 nm.

[0147] Various e-coated boards were tested and compared with the original e-coated Waelzholz M310-65A board.

[0148] The following C5e-coated steel substrate was comparatively tested using methods outside the present invention and the methods of the present invention. NO30-1500A Suralac 7000 M270-50AA Backlack Suralack 9000 (EB549) M270-35AA Backlack Suralack 9000 (EB549) M330-50 Backlack 2xPE75W Waelzholz M310-65A-blue / grey board Waelzholz M310-65A - Original

[0149] [Table 6]

[0150] The "ACM..." codes in Table 5 above are the identifying references / codes for each test. "Loctite3510" and "LoctiteAA3510" are the same product. (AA=Anaerobic Adhesive). Each test was done on three samples, labeled "Sample" 1-3 above. The tensile shear strength results from the three tests were averaged as indicated by "Average". 24hr Room Temperature N / mm 2 is the tensile shear strength (N / mm 2 ) is shown.

[0151] ACM-DUB-0031-81-02 is a comparison test in which Loctite® 3510 is applied to the lap shears and the lap shears are clamped together.

[0152] The substrate is a comparative C5e-coated lap shear, NO30-1500ASuralac 7000. The clamped joint is rated at 200mW / cm 2 The specimen is exposed to a 60 second exposure at an intensity of 10 ...

[0153] ACM-DUB-0031-82-02 is a comparative test where Loctite® 3510 is applied to the lap shear and the lap shear is clamped together. The substrate is a comparative C5e-coated substrate, M270-50AA Backlack Suralack 9000 (EB549). The clamped joint is subjected to 200mW / cm 2 The specimen is exposed to a 60 second exposure at an intensity of 10 ...

[0154] ACM-DUB-0031-83-02 is a comparative test where Loctite® 3510 is applied to the lap shear and the lap shear is clamped together. The substrate is a comparative C5-e-coated substrate, M270-35AA Backlack Suralack9000 (EB549). The clamped joint is heated to 200mW / cm 2 The specimen is exposed to a 60 second exposure at an intensity of 10 ...

[0155] ACM-DUB-0031-84-02 is a comparison test where Loctite® 3510 is applied to the lap shear and the lap shear is clamped together. The substrate is a comparative C5e-coated substrate, M330-50 Backlack 2xPE75W. The clamped joint is heated to 200mW / cm 2The sample is exposed to an intensity of 10000 for 60 seconds and left to stand for 24 hours before testing. In this test, the exposure of the primer and the primed substrate is omitted. This corresponds to test ACM-DUB-0031-81-02.

[0156] ACM-DUB-0031-85-02 is a comparative test where Loctite® 3510 is applied to the lap shear and the lap shear is clamped together. The substrates are a comparative C5e-coated substrate, a Waelzholz M310-65A-blue / grey substrate. The clamped joint is subjected to a 200mW / cm 2 The specimen is exposed to a 60 second exposure at an intensity of 10 ...

[0157] ACM-DUB-0031-86-02 is a comparison test where Loctite® 3510 is applied to the lap shears and the lap shears are clamped together. The substrate is the original C5e-coated substrate, Waelzholz M310-65A, used in the previous experiment above. The clamped joints are heated to 200 mW / cm 2 The specimen is exposed to a 60 second exposure at an intensity of 10 ...

[0158] The tests in the method of the present invention (which can be compared to those in Table 5) were repeated using the UVALOC 1000, with the assembly placed in the UVALOC 1000 and exposed to 200 mW / cm for both irradiation steps. 2 The light was irradiated for 60 seconds at an intensity of 100 nm.

[0159] Various e-coated boards were tested and compared with the original e-coated Waelzholz M310-65A board.

[0160] The following C5e-coated steel substrates were tested: NO30-1500A Suralac 7000 M270-50AA Backlack Suralack 9000 (EB549) M270-35AA Backlack Suralack 9000 (EB549) M330-50 Backlack 2xPE75W Waelzholz M310-65A-blue / grey board Waelzholz M310-65A - Original

[0161] [Table 7]

[0162] The "ACM..." codes in Table 6 above are the identifier references / codes for the respective tests. "Loctite 3510" and "Loctite AA3510" are the same product. (AA = Anaerobic Adhesive). Loctite® Products 3510 and 7091 are as described above. Each test was performed using three or five samples, labeled "Samples" 1-5 above. The tensile shear strength results of the three / five tests were averaged as indicated by "Average". 24 hr Room Temperature N / mm 2 is the tensile shear strength (N / mm 2 ) is shown.

[0163] ACM-DUB-0031-81-06 is a test within the scope of this invention in which Loctite® 7091 primer was applied at lap shear and then heated at 200 mW / cm in a UVALOC 1000. 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The test is carried out after 60 seconds at an intensity of 100 nm and then after 24 hours of standing. This test includes all steps of the method of the present invention.

[0164] N030-1500A Suralac7000 is the comparison C5e-coated board tested in this experiment. It corresponds to test ACM-DUB-0031-57-05.

[0165] ACM-DUB-0031-82-06 is a test within the scope of this invention, which involves applying Loctite® 7091 primer to lap shear and placing it on a UVALOC 1000 at 200 mW / cm 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The test is carried out after 60 seconds at an intensity of 100 nm and then after 24 hours of standing. This test includes all steps of the method of the present invention.

[0166] The M270-50AA Backlack Suralack 9000 (EB549) is the comparison C5e-coated board tested in this experiment. It corresponds to test ACM-DUB-0031-57-05.

[0167] ACM-DUB-0031-83-06 is a test within the scope of this invention, in which Loctite® 7091 primer was applied to lap shear and placed on a UVALOC 1000 at 200 mW / cm 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The substrate is exposed to an intensity of 100000 for 60 seconds and then left for 24 hours before testing. This test includes all steps of the method of the present invention. M270-35AA Backlack Suralack 9000 (EB549) is the comparative C5e-coated substrate tested in this experiment. It corresponds to test ACM-DUB-0031-57-05.

[0168] ACM-DUB-0031-84-06 is a test within the scope of this invention, which uses Loctite® 7091 primer applied at lap shear and 200 mW / cm in a UVALOC 1000. 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The substrate is exposed to a 60 second exposure at an intensity of 10 ...

[0169] ACM-DUB-0031-85-06 is a test within the scope of this invention, which uses Loctite® 7091 primer applied at lap shear and 200 mW / cm in a UVALOC 1000. 2 Apply Loctite® 3510 to the lap shear, clamp the lap shear together and irradiate in a UVALOC 1000 at an intensity of 200 mW / cm for 60 seconds. 2 The substrate is exposed to an intensity of 10 ...

[0170] ACM-DUB-0031-85-06 is a test within the scope of this invention in which Loctite® 7091 primer was applied to lap shear and placed in a UVALOC 1000 and tested at 200 mW / cm 2The substrate is exposed to an intensity of 10 ...

[0171] The results of the above tests are shown in Figure 2, where the comparative results (from Table 5) are displayed on the left side of each pair of columns, and the results using the method of the present invention (from Table 6) are displayed on the right side of each pair of columns. As can be seen, the results using the method of the present invention are clearly superior in achieving better tensile strength in all cases.

[0172] The above tests demonstrate that the process of the present invention significantly improves the tensile strength performance of a variety of C5e-coated steel substrates.

[0173] As used herein in connection with the present invention, the terms "comprises / comprising" and "having / including" are used to specify the presence of stated features, integers, steps, or ingredients, but do not exclude the presence or addition of one or more other features, integers, steps, ingredients, or groups thereof.

[0174] It is appreciated that certain features of the invention that are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Claims

1. 1. A method for bonding together a first substrate and a second substrate, each having a respective bonding surface to be bonded together, comprising: (a) applying a redox-active metal catalyst primer to the bonding surface of at least a first substrate to form a primed surface; (b) activating the prime adhesive surface of the first substrate by exposing the prime adhesive surface to actinic radiation; (c) applying a UV-curable anaerobic adhesive to the activated adhesive surface of the first substrate and / or the adhesive surface of the second substrate; (d) bonding the adhesive surfaces together with a UV-curable anaerobic adhesive therebetween; and (e) exposing the UV-curable anaerobic adhesive between the mating surfaces to actinic ultraviolet light.

2. Step (a) comprises applying a redox-active metal catalyst primer to a bonding surface of each of a first substrate and a second substrate to form a respective primed surface; 10. The method of claim 1, wherein step (b) comprises activating the respective prime adhesive surfaces of the first and second substrates by exposing the respective prime adhesive surfaces to actinic radiation.

3. 3. The method of claim 2, wherein step (c) comprises applying a UV-curable anaerobic adhesive to the activated adhesive surface of the first substrate and to the activated adhesive surface of the second substrate.

4. The method of claim 1 or 2, wherein the actinic radiation in step (b) has a wavelength of from 10 nm to 10,000 nm.

5. 3. The method of claim 1, wherein the duration of exposure to actinic radiation in step (b) is from 1 to 300 seconds.

6. 3. The method according to claim 1, wherein the intensity of the actinic radiation in step (b) is 1 to 5000 mW / cm 2 .

7. 3. The method of claim 1, wherein the total energy to which the prime bonding surface of the first substrate and / or the prime bonding surface of the second substrate are exposed during step (b) is from 1 to 300,000 mJ / cm 2 .

8. The method of claim 1 or 2, wherein the actinic radiation in step (e) has a wavelength of from 10 nm to 10,000 nm.

9. 3. The method of claim 1, wherein the duration of exposure to actinic radiation in step (e) is from 1 to 300 seconds.

10. 3. The method according to claim 1, wherein the intensity of the actinic radiation in step (e) is 1 to 5000 mW / cm 2 .

11. 3. The method of claim 1, wherein the total energy to which the UV-curable anaerobic adhesive is exposed during step (e) is 1 to 300,000 mJ / cm 2 .

12. 3. The method of claim 1 or 2, wherein the redox-active metal catalyst primer comprises a redox-active metal catalyst selected from cobalt naphthenate, copper carbonate, copper(II) acetylacetonate, silver nitrate, vanadium(III) acetylacetonate, iron(II) naphthenate, copper disodium ethylenediaminetetraacetic acid (EDTA.2Na.Cu(II)), vanadyl acetylacetonate, iron(II) acetate, or a combination thereof.

13. The method of claim 1 or 2, wherein the redox-active metal catalyst primer comprises a copper-based primer.

14. The method of claim 13 , wherein the redox-active metal catalyst primer comprises at least one CuII salt.

15. 15. The method of claim 14, wherein the CuII salt is selected from Cuacac (copper(II) acetylacetonate) and copper(II) ethylhexanoate, and combinations thereof.

16. 3. The method of claim 1 or 2, wherein the redox-active metal catalyst primer comprises a redox-active metal catalyst dissolved in a solvating agent.

17. The method of claim 1 or 2, wherein the redox-active metal catalyst primer comprises an organic solvent.

18. The method of claim 1 or 2, wherein the redox-active metal catalyst primer comprises 0.01 to 0.4% active redox-active metal catalyst, based on the total weight of the solution.

19. 3. The method of claim 1 or 2, wherein at least one substrate has a coating thereon, and further wherein the coating is applied by curing a curable coating composition on the substrate.

20. 20. The method of claim 19, wherein the substrate is steel, and optionally the substrate forms part of an electric motor.

21. 20. The method of claim 19, wherein the coating is formed from an epoxy resin, a phenolic resin (including a phenol / formaldehyde resin), or a polyurethane resin, or a combination thereof.

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