Shim treatment adhesive

Abstract

A two-part shim process adhesive that can be cured upon mixing is provided, comprising a base part and a hardener part. The base part comprises a multifunctional epoxy resin having at least three epoxy functional groups, a difunctional epoxy resin miscibly blended with the multifunctional epoxy resin. The hardener part comprises a polyetheramine. Either the base part or the hardener part further comprises an inorganic filler present in an amount of 10 percent to 60 percent, based on the total weight of the two-part curable shim process adhesive, and a phosphate ester. The shim process adhesive allows for joint assembly in one step, providing a significant advantage to users.

Description

[Technical Field]

[0001] Provided herein are curable adhesives for shimming bonded structures, such as primary and secondary structures in industrial applications. [Background technology]

[0002] A shim is a thin piece of material used to fill small gaps or spaces between parts that are to be joined together. Shims take on the shape of the gap and can support compressive loads when fastened together, typically using mechanical fasteners, to prevent excessive strain and damage to structural components. Shims are used in industrial applications such as automotive and aerospace manufacturing. Various forms of shims are also used in residential and commercial construction.

[0003] Various types of shims are available. Solid shims may be made of the same material as the joint. Laminated peelable shims can be made with multiple foil layers that can be removed one by one until the desired fit is achieved. Liquid shim materials work well for filling irregular or tapered joint surfaces and are typically used to fill gaps less than 0.7 millimeters wide.

[0004] Determining the need, size, and shape of a given shim is often an iterative, labor-intensive process. Typically, the part is temporarily assembled and then visually inspected and measured for gaps between the skin and the underlying structure. The part may then be disassembled, and a test shim would be fabricated. The part can then be reassembled with the shim temporarily fixed in place to verify fit. This is a second temporary assembly operation, and such operations may need to be repeated until a proper fit is achieved.

[0005] Liquid shims are not structural adhesives because the bond line is not in the primary load path. In mechanically fastened joints, shear loads are carried by the fasteners, not the shimming material. In these assemblies, the only loads carried by liquid shims are compressive loads. Summary of the Invention

[0006] Provided herein is a liquid shim treatment composition that can also function as an adhesive. Upon curing, the shim treatment composition provides high peel strength with excellent heat / wet bonding performance, allowing for simplified manufacturing processes by eliminating the need to apply a separate adhesive.

[0007] In a first aspect, a two-part curable shim process adhesive is provided, the adhesive comprising: a base part including a multifunctional epoxy resin having at least three epoxy functional groups; and a difunctional epoxy resin miscibly blended with the multifunctional epoxy resin; and a hardener part including a polyetheramine, wherein either the base part or the hardener part further comprises an inorganic filler present in an amount of 10 percent to 60 percent, based on the total weight of the two-part curable shim process adhesive, and a phosphate ester.

[0008] definition As used herein, "Alkyl" refers to straight- and branched-chain alkyl groups, and cycloalkyl groups, having 1 to 40 carbon atoms, 1 to 20 carbon atoms, 1 to 12 carbon atoms, or, in some embodiments, 1 to 8 carbon atoms; "Ambient conditions" means a temperature of 23°C and a pressure of 1 atmosphere (i.e., 101.3 kPa); "Ambient temperature" refers to a temperature of 23°C; "Average" refers to the numerical average unless otherwise indicated; "Cure" refers to chemically crosslinking (e.g., at ambient temperature or under heated conditions), such as by exposure to any form of radiation, heating, or undergoing a chemical reaction that results in hardening or an increase in viscosity; "Cycloalkyl" refers to cyclic alkyl groups such as, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups; "Organic group" refers to any carbon-containing functional group; "Polymer" refers to a molecule having multiple repeating units; "Substantially" means a majority or majority, or 100%, such as at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more; "Substituted," in reference to a molecule or organic group, as defined herein, refers to a state in which one or more hydrogen atoms therein are replaced with one or more non-hydrogen atoms. DETAILED DESCRIPTION OF THE INVENTION

[0009] As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may offer certain advantages, under certain circumstances, although other embodiments may also be preferred, under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are not useful, or is not intended to exclude other embodiments from the scope of the invention.

[0010] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an element preceded by "a" or "the" may include one or more of the element and equivalents thereof known to those skilled in the art. Furthermore, the term "and / or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[0011] In the methods described herein, steps may be performed in any order without departing from the principles of the present disclosure, unless a temporal or operational order is explicitly recited. Moreover, unless a claim explicitly recites certain acts to be performed separately, those acts may be performed simultaneously. For example, a claimed act of doing X and a claimed act of doing Y may be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the claimed process.

[0012] It should be noted that the term "comprises" and variations thereof do not have a limiting meaning when these terms appear in the accompanying description. Furthermore, "a," "an," "the," "at least one," and "one or more" are used interchangeably herein. Relative terms such as left, right, front, rear, top, bottom, side, above, below, horizontal, and vertical may be used herein, where such terms are from the perspective seen in a particular view. However, these terms are used merely for ease of description and in no way limit the scope of the present invention.

[0013] Throughout this specification, reference to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" means that the particular feature, structure, material, or characteristic described with respect to that embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one or more embodiments," "in a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the invention.

[0014] Provided herein are curable two-part compositions used to make shims for bonded assemblies, which may be used in some cases in automotive, aerospace, marine, residential, architectural, or other commercial or industrial applications.

[0015] In some embodiments, the shimmed part is an aircraft part, including the skin and substructure of the aircraft, which may include, but is not limited to, springs, spars, ribs, and other structural elements of the aircraft wings and fuselage.

[0016] Structural shims are fly-away components of aircraft and are fabricated from rigid, load-bearing materials. These shims are used to fill gaps between assembled parts that would otherwise result in the parts sinking or buckling and the associated stress concentrations. These stress concentrations, if severe, can cause fasteners to fail and ultimately result in significant damage to the aircraft. Therefore, it is desirable to provide a composition that can easily flow or spread (i.e., a liquid or paste) before hardening, allowing for the formation of a customized shim that fits precisely into the gap where it is installed.

[0017] The provided curable shim treatment adhesive is preferably a two-part composition including a base part and a hardener part. The curable adhesive can be cured by mixing the base part and the hardener part together. For user convenience, curing is generally carried out at ambient temperature.

[0018] Main ingredient The base of the curable two-part shim adhesive is comprised of a blend of epoxy resins, more specifically, a difunctional epoxy resin and a multifunctional epoxy resin having at least two, and preferably three or more, epoxy functional groups.

[0019] Difunctional epoxy resins, which have exactly two epoxy functionalities, can be miscible and blended with multifunctional epoxy resins. Multifunctional epoxy resins can have epoxy functionalities of at least 2.1, at least 2.2, at least 2.3, at least 2.4, at least 2.5, at least 2.6, at least 2.7, at least 2.8, at least 2.9, or at least three. Multifunctional epoxy resins can also be composed of two or more resins, each with more than two epoxy functionalities.

[0020] Epoxy resins include glycidated resins, cycloaliphatic resins, and epoxidized oils. Glycidated resins can be the reaction product of a glycidyl ether, such as epichlorohydrin, with a bisphenol compound, such as bisphenol A. Various examples of epoxy resins include C4-C28 alkyl glycidyl ethers; C2-C28 alkyl- and alkenyl-glycidyl esters; C1-C28 alkyl-, mono-, and polyphenol glycidyl ethers; polyglycidyl ethers of pyrocatechol, resorcinol, hydroquinone, 4,4'-dihydroxydiphenylmethane (or bisphenol F), 4,4'-dihydroxy-3,3'-dimethyldiphenylmethane, 4,4'-dihydroxydiphenyldimethylmethane (or bisphenol A), 4,4'-dihydroxydiphenylmethylethane, 4,4'-dihydroxydiphenylcyclohexane, 4,4'-dihydroxy-3,3'-dimethyldiphenylpropane, 4,4'-dihydroxydiphenylsulfone, and tris(4-hydroxyphynyl)methane; and polyglycidyl ethers of chlorinated and brominated products of the above diphenols. polyglycidyl ethers of diphenols obtained by esterifying ethers of diphenols obtained by esterifying salts of aromatic hydrocarboxylic acids with dihaloalkanes or dihalogen dialkyl ethers; polyglycidyl ethers of polyphenols obtained by condensing phenols and long-chain halogenoparaffins containing at least two halogen atoms; N,N'-diglycidylaniline; N,N'-dimethyl-N,N'-diglycidyl-4,4'-diaminodiphenylmethane; N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane; N,N'-diglycidyl-4-aminophenyl glycidyl ether; N,N,N',N'-tetraglycidyl-1,3-propylenebis-4-aminobenzoate; phenol novolac epoxy resins; cresol novolac epoxy resins; and combinations thereof.

[0021] Representative, non-limiting examples of suitable epoxy resins include bis-4,4'-(1-methylethylidene)phenol diglycidyl ether and (chloromethyl)epoxide bisphenol A diglycidyl ether. Commercially available epoxy resins that can be used in the practice of the present invention include those sold under the trade name ARALDITE by Huntsman Corporation, The Woodlands, TX, and those sold under the trade name EPON by Hexion Inc., Columbus, OH. Suitable epoxy resins also include glycidyl ethers of trihydric phenols, such as tris(hydroxyphenyl)methane. Such resins are sold under the trade name TACTIX by Huntsman Corporation, The Woodlands, TX.

[0022] In some embodiments, epoxy novolac resins may be used. In some embodiments, multifunctional epoxy resins include tetrafunctional epoxy resins based on metaxylenediamine, such as those sold under the trade name ERISYS by Emerald Performance Materials LLC, Vancouver, WA.

[0023] It may be advantageous to use a mixture of epoxy resins, the components of which are selected to provide the desired viscosity characteristics before curing. In some embodiments, the multifunctional epoxy resin includes a trifunctional epoxy resin, such as triphenylmethane triglycidyl ether, or other glycidyl ethers having three or more epoxide groups per molecule. The trifunctional epoxy resin is sometimes a solid epoxy resin at ambient temperature. Optionally, the trifunctional epoxy resin is blended with a tetrafunctional epoxy resin, such as 4,4'-methylenebis(N,N-diglycidylaniline). The difunctional epoxy resin may be a bisphenol A / epichlorohydrin-derived liquid epoxy resin, or other glycidyl ethers having two epoxide groups per molecule.

[0024] The relative amounts of the multifunctional epoxy resin and the difunctional epoxy resin can be adjusted to obtain a suitable crosslink density, which affects important adhesive properties such as glass transition temperature, tensile strength, and shear strength. A suitable amount of low-viscosity difunctional epoxy resin can also aid in the flow of the uncured adhesive and wet the bonding surfaces of the substrates to improve bond strength. In the provided shim treatment adhesives, the multifunctional epoxy resin and the difunctional epoxy resin can be present in a relative weight ratio to each other of 1:1 to 6:1, 1:1 to 4:1, 1:1 to 2:1, or in some embodiments, less than, equal to, or greater than 1:1, 2:1, 3:1, 4:1, 5:1, or 6:1.

[0025] In a preferred embodiment, the multifunctional epoxy resin includes both trifunctional and tetrafunctional epoxy resins in relative amounts that balance the competing properties of stiffness and adhesion of the cured shim adhesive. It has been found that certain epoxy resins, such as solid or semi-solid triphenylmethane triglycidyl ether, have been found to increase adhesive stiffness, while others, such as liquid tetrafunctional 4,4'-methylenebis(N,N-diglycidylaniline), have been found to enhance adhesive strength.

[0026] Consistent with these considerations, the trifunctional epoxy resin and the tetrafunctional epoxy resin may be present in a relative weight ratio to one another of 1:1 to 8:1, 1:1 to 6:1, 1:1 to 4:1, or in some embodiments less than, equal to, or greater than 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, or 8:1.

[0027] The epoxy resin or resins in the base portion can have any suitable molecular weight, including weight average molecular weights of 100 g / mol to 50,000 g / mol, 175 g / mol to 20,000 g / mol, 250 g / mol to 10,000 g / mol, or in some embodiments less than, equal to, or greater than 100 g / mol, 125 g / mol, 150 g / mol, 175 g / mol, 200 g / mol, 250 g / mol, 300 g / mol, 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol, 550 g / mol, 600 g / mol, 650 g / mol, 700 g / mol, 750 g / mol, 800 g / mol, 850 g / mol, 900 g / mol, 950 g / mol, 1000 g / mol, 2000 g / mol, 5000 g / mol, 7000 g / mol, 10,000 g / mol, 20,000 g / mol, 30,000 g / mol, 40,000 g / mol, or 50,000 g / mol.

[0028] The total mixture of the base and hardener parts generally contains at least 20 weight percent epoxy resin, based on the combined weight of the base and hardener parts (i.e., based on the total weight of the shim adhesive composition). For example, the shim adhesive may contain at least 25 weight percent, at least 30 weight percent, at least 40 weight percent, or at least 50 weight percent epoxy resin. The shim adhesive may contain up to 90 weight percent epoxy resin.

[0029] In some embodiments, the base resin further comprises an inorganic filler to increase the compressive strength of the cured shim adhesive. Many useful inorganic fillers are possible. Examples include naturally occurring or synthetic materials such as silicon dioxide; nitrides (e.g., silicon nitride); glasses and fillers derived from, for example, Zr, Sr, Ce, Sb, Sn, Ba, Zn, and Al; feldspar; borosilicate glasses; zirconia; titania; and micron and submicron fumed silica particles (e.g., pyrogenic silicas such as those available under the trade name AEROSIL, including "OX50," "130," "150," and "200" silicas from Degussa Corp., Akron, Ohio, and CAB-O-OSIL M5 silica from Cabot Corp., Tuscola, IL). In a preferred embodiment, the inorganic filler includes fumed silica. The fumed silica optionally has a median particle size in the range of 1 to 10 micrometers.

[0030] The inorganic filler or fillers can be present in any suitable amount, such as 10 to 60 percent, 12 to 45 percent, 15 to 30 percent, or in some embodiments, less than, equal to, or greater than 10, 12, 15, 17, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent by weight of the two-part curable shim process adhesive.

[0031] To facilitate dispersion of the inorganic filler in the matrix resin, the base resin portion may further comprise a phosphate ester. The phosphate ester may optionally be a phosphate polyester copolymer containing acid groups. A useful phosphate ester is available under the trade name BYKW9010 from Altana AG, Wesel, Germany.

[0032] The inorganic filler and phosphate ester may be present in a relative weight ratio of from 100:3 to 1000:3, from 100:3 to 500:3, from 100:3 to 300:3, or in some embodiments less than, equal to, or greater than 100:3, 150:3, 200:3, 250:3, 300:3, 350:3, 400:3, 450:3, 500:3, 600:3, 700:3, 800:3, 900:3, or 1000:3.

[0033] The base portion may, in some embodiments, include other toughening components. Exemplary toughening components may include, for example, core-shell rubber particles.

[0034] Core-shell particles are filler particles having two or more distinct concentric portions: a core and one or more shell layers surrounding the core. In some embodiments, the core-shell particles are core-shell rubber (CSR) particles having an elastomeric core, made from either a physically crosslinked or microphase-separated polymer, and the shell layer is made from a non-elastomeric glassy polymer. Advantageously, the rubbery elastomeric core can increase the toughness of the cured shim adhesive, and the glassy polymer shell can provide compatibility between the filler particle and the matrix.

[0035] In exemplary composite applications, the core-shell particles may have a range of 10 nm to 800 nm, 50 nm to 500 nm, or 80 nm to 300 nm, or in some embodiments may be less than, equal to, or greater than 5 nm, 10, 20, 30, 40, 50, 70, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 nm.

[0036] The core-shell particles may be uniformly dispersed in the composition or may be at least partially aggregated. The aggregated core-shell particles may be in physical contact with one or more other core-shell particles. In some embodiments, the core-shell particles form long chains of aggregated particles that extend throughout the bulk of the curable resin. Such aggregated core-shell particle chains may be linear or branched. The core-shell particle chains may themselves be uniformly distributed throughout the bulk of the curable resin. The structure of such aggregates may be substantially retained when the shim adhesive is cured.

[0037] The core-shell rubber toughener may be present in an amount of from 1 percent to 20 percent, from 1 percent to 15 percent, from 1 percent to 10 percent, or in some embodiments, less than, equal to, or greater than 1 percent, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 percent of the total weight of the base portion of the two-part curable shim process adhesive.

[0038] Further technical aspects of core-shell particles are described elsewhere, such as in co-pending WO 2019 / 005800 (Chen et al.).

[0039] The base resin optionally contains one or more reactive diluents. Reactive diluents that reduce the viscosity of the epoxy resin component are generally epoxy resins having either a saturated or cyclic branched aliphatic backbone. Examples of reactive diluents include, but are not limited to, diglycidyl ether of resorcinol, diglycidyl ether of cyclohexanedimethanol, diglycidyl ether of neopentyl glycol, and triglycidyl ether of trimethylolpropane. Diglycidyl ether of cyclohexanedimethanol is commercially available from Hexion Specialty Chemicals in Columbus, Ohio, under the trade name HELOXY MODIFIER 107, and from Evonik Industries AG, Essen, Germany, under the trade name EPODIL 757.

[0040] The reactive diluent can be added in a suitable amount to obtain the desired viscosity profile of the uncured shim adhesive. Typical amounts can be 1 to 12 weight percent, based on the total weight of the epoxy component. Further details of reactive diluents can be found, for example, in International Publication No. WO 2014 / 210298 (Elgimiabi et al.).

[0041] Hardener part The hardener portion includes at least one hardener that, when mixed with the epoxy resin of the base portion, initiates a chemical reaction that hardens the two-part shim adhesive.

[0042] Useful curing agents include cyclic compounds containing at least one cyclic moiety, which may be either aliphatic or aromatic. The cyclic moiety may be substituted with a primary amino group, i.e., the primary amino group may be directly attached to the ring. Preferably, the cyclic moiety is substituted with one or more residues bearing a primary amino group, optionally at a terminal position. The residue may be, for example, a linear or branched aminoalkyl group, preferably with a primary amino group at a terminal position.

[0043] The curing agent may contain at least one, preferably at least two, primary amino groups (-NH groups) at terminal positions. The most preferred embodiment contains two primary amino groups, both of which are at terminal positions of the molecule. At least one cyclic moiety is typically a five- or six-membered ring, which may be a hydrocarbon ring or a heterohydrocarbon ring. The heterohydrocarbon ring typically contains one or more heteroatoms selected from nitrogen and oxygen atoms.

[0044] Examples of suitable curing agents include, but are not limited to, cyclohexane containing one or more terminal primary amino groups and / or aminoalkyl residues with one or more terminal primary amino groups, piperazine containing one or more terminal primary amino groups and / or aminoalkyl residues with one or more terminal primary amino groups, and morpholine containing one or more terminal primary amino groups and / or aminoalkyl residues with one or more terminal primary amino groups. Specific examples include, but are not limited to, bis- or tris-aminoalkyl piperazines or morpholines. Specific examples include, but are not limited to, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (also known as isophoronediamine) and N,N-bis(3-aminopropyl)piperazine.

[0045] The curing agent may be an aliphatic cyclic (poly)amine, as described above, or an adduct of such an aliphatic cyclic polyamine with one or more epoxy resins, provided that the aliphatic cyclic polyamine is used in molar excess to ensure that the adduct contains at least two primary amine groups, preferably at the terminal positions of the adduct. Preferably, the epoxy resin used to form the adduct is the same as or similar to one of the epoxy resins used in the epoxy component. For example, the first curing agent may be a diamine that reacts with an epoxy resin having two glycidyl groups to form an adduct, and the first primary curing agent may be used in a molar ratio of diamine to epoxy resin of 2:1 or greater to form an amine-containing adduct having two amino groups. Often, a molar excess of amine is used, so that the curing agent contains both the amine-containing adduct and free (unreacted) amine curing agent. For example, the molar ratio of amine curing agent to epoxy resin having two glycidyl groups may be greater than 2.5:1, greater than 3:1, greater than 3.5:1, or greater than 4:1.

[0046] Useful aliphatic amines need not be cyclic and can include linear and / or branched polyetheramines. In some embodiments, the curing agent composition comprises an excess, typically less than, equal to, or greater than 200% to 800%, 300% to 600%, 400% to 500%, or in some embodiments, 200%, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800%, molar excess of at least one adduct of a difunctional unbranched polyetheramine along with an epoxy resin.

[0047] The unbranched polyetheramine may have a molecular weight of from 130 g / mol to 500 g / mol, from 180 g / mol to 400 g / mol, from 200 g / mol to 300 g / mol, or in some embodiments less than, equal to, or greater than 130 g / mol, 140, 150, 160, 170, 180, 190, 200, 220, 250, 270, 300, 320, 350, 370, 400, 420, 450, 470, or 500 g / mol.

[0048] The unbranched polyetheramines can have 1 to 4 ether oxygens, more typically 2 or 3 ether oxygens. In some embodiments, the unbranched polyetheramines have a structure represented by Formula I: [ka] wherein y is selected from 1, 2, 3, or 4; and each x is independently selected from 2, 3, or 4.

[0049] In some embodiments, the unbranched polyetheramine can be 4,7,10-trioxatridecanediamine (TTD). In some embodiments, the unbranched polyetheramine can be 4,7-dioxadecanediamine, commercially available as JEFFAMINE EDR176.

[0050] Suitable amounts of polyetheramine may be between 5 percent and 30 percent, between 5 percent and 20 percent, between 5 percent and 15 percent, or in some embodiments, less than, equal to, or greater than 5 percent, 10, 15, 20, 25, or 30 percent, based on the total weight of the shim adhesive before curing.

[0051] In some cases, the hardener portion further comprises a secondary hardener. The secondary hardener may be an imidazole or a salt thereof, an imidazoline or a salt thereof, or a phenol substituted with a tertiary amino group. An exemplary secondary hardener is tris-2,4,6-(dimethylaminomethyl)phenol, commercially available under the trade name ANCAMINE K54 from Evonik Industries AG, Essen, Germany.

[0052] Any component that may be present in the base part of a two-part curable shim treatment adhesive may also be present in the curing agent part. For example, the curing agent part may contain any of the inorganic fillers, such as fumed silica, described above with reference to the base part in the amounts provided. The curing agent part may also contain any of the phosphate esters used in combination with the inorganic fillers, as described above with reference to the base part in the amounts provided. The curing agent part may also contain any of the core-shell rubber toughening agents described above with reference to the base part in the amounts provided.

[0053] In any of the above cases, both the base part and the hardener part may contain the above-mentioned ingredients in similar or different proportions.

[0054] Either or both of the base and curative parts may further include additives known to those skilled in the art, including impact modifiers, other functional fillers, rheology modifiers, and / or pigments.

[0055] Shim processing method Prior to use, the base and hardener portions are kept separate to avoid premature curing. At the time of use, these portions are mixed to provide a homogeneous reactive mixture. The amount of each portion included in the mixture can be selected to provide the desired molar ratio of epoxide groups from the base portion to amine hydrogen atoms from the hardener portion. The ratio of amine hydrogen equivalents to epoxy equivalents in the hardener can be selected so that sufficient amine groups are present to fully react with the epoxide groups in the epoxy resin and any other reactive diluents or additives, if present.

[0056] The then-mixed shim adhesive can then be placed between the bonding surfaces of two or more respective substrates and then cured, thereby providing a bonded assembly. In a preferred method of bonding, two substrates are mated together with the reactive mixture disposed therebetween, and the two substrates are further secured together during curing using mechanical fasteners that extend through the substrates and the reactive mixture. The provided compositions may be particularly suitable as shim materials to act as adhesives capable of supporting tensile, shear, and peel loads while filling any remaining gaps between components of the assembly.

[0057] In many embodiments, the shim adhesive composition has a low viscosity at ambient temperatures, allowing it to be syringed or otherwise applied. Typically, the composition exhibits a low degree of sag or creep upon application.

[0058] In many embodiments, the shim adhesive compositions provided herein fully cure in 24-48 hours at ambient temperature and can be sanded or drilled 4 hours after application. In many embodiments, the shim adhesive compositions have a pot life (time for positioning and adjustment) of about 3 hours and can be cured at an accelerated rate with the application of mild heat, typically in less than 30 minutes at 70°C.

[0059] The cured compositions exhibit good mechanical properties, which are desirable for shimming applications, particularly in the automotive and aircraft industries. For example, the cured shimming compositions may have a cohesive strength, as measured by overlap shear strength, of at least 2500 psi (17.2 MPa). For example, the overlap shear strength may be at least 3000 psi (20.7 MPa) or at least 3200 psi (22.1 MPa).

[0060] Substrate materials can include metals (e.g., steel, iron, copper, aluminum, or alloys thereof) and composites. Composites typically contain one or more types of fibers embedded in a resin. Typical fibers include carbon fiber, glass fiber, and combinations thereof. The resin can be an epoxy resin, a phenolic resin, a polyamide resin, or a combination thereof, or other resin. Preferably, the composition is applied to fill any remaining voids between composites, most preferably fiber-reinforced resins, including carbon fiber and glass fiber-reinforced epoxy composites.

[0061] In many embodiments, the shim-treated adhesive composition exhibits high compressive strength properties at ambient and elevated temperatures, as well as high peel resistance at non-high temperatures, such as ambient temperatures. For example, the shim-treated adhesive when cured may have a compressive modulus of 500 MPa to 2500 MPa, 700 MPa to 2000 MPa, or 700 MPa to 1500 MPa at 90° C. The same shim-treated adhesive when cured may have an average floating roller peel strength of 50 N / 25 mm to 250 N / 25 mm, 100 N / 25 mm to 250 N / 25 mm, or 120 N / 25 mm to 250 N / 25 mm at ambient temperatures.

[0062] The provided shimming adhesives are not limited to applications in aircraft and automotive assemblies. Gaps to be shimmed may also exist between assembled portions of residential or commercial buildings or components thereof. For example, the provided shimming adhesives can be used to shim gaps in components of wind energy plants or stations, such as rotor blades or towers of wind turbines.

[0063] Further exemplary embodiments are provided below, which are not intended to be exhaustive.

[0064] 1. A two-part curable shim process adhesive comprising a base part comprising a multifunctional epoxy resin having at least three epoxy functional groups; and a difunctional epoxy resin miscibly blended with the multifunctional epoxy resin; and a hardener part comprising a polyetheramine, wherein either the base part or the hardener part further comprises an inorganic filler present in an amount of 10 percent to 60 percent, based on the total weight of the two-part curable shim process adhesive, and a phosphate ester.

[0065] 2. The two-part curable shim treatment adhesive of embodiment 1, wherein the multifunctional epoxy resin and said difunctional epoxy resin are present in a weight ratio of 1:1 to 6:1.

[0066] 3. The two-part curable shim process adhesive of embodiment 1 or 2, wherein the base part and / or the curing agent part further comprise core-shell rubber particles present in an amount of 1 percent to 20 percent, based on the total weight of the two-part curable shim process adhesive.

[0067] 4. The two-part curable shim treatment adhesive of any one of embodiments 1-3, wherein the multifunctional epoxy resin comprises a trifunctional epoxy resin.

[0068] 5. The two-part curable shim treatment adhesive of embodiment 4, wherein the trifunctional epoxy resin comprises triphenylmethane triglycidyl ether.

[0069] 6. The two-part curable shim treatment adhesive of any one of embodiments 1-5, wherein the multifunctional epoxy resin comprises a tetrafunctional epoxy resin.

[0070] 7. The two-part curable shim adhesive of embodiment 6, wherein the tetrafunctional epoxy resin comprises 4,4'-methylenebis(N,N-diglycidylaniline).

[0071] 8. The two-part curable shim treatment adhesive of any one of embodiments 1-7, wherein the trifunctional epoxy resin and said tetrafunctional epoxy resin are present in a relative weight ratio of 1:1 to 8:1.

[0072] 9. The two-part curable shim treatment adhesive of any one of embodiments 1-8, wherein the polyetheramine comprises trioxadecanediamine.

[0073] 10. The two-part curing shim process adhesive of any one of embodiments 1-9, wherein the polyetheramine is present in an amount of 5 percent to 30 percent, based on the total weight of the two-part curing shim process adhesive.

[0074] 11. The two-part curable shim treatment adhesive of any one of embodiments 1-10, wherein the inorganic filler comprises fumed silica.

[0075] 12. A bonded assembly comprising the reaction product of the two-part curable shim treatment adhesive of any one of embodiments 1-11, wherein the reaction product is disposed between bonding surfaces of two or more respective substrates. [Example]

[0076] Objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, although the specific materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit the present disclosure. Unless otherwise stated, all parts, percentages, and ratios in the examples and elsewhere in the specification are by weight. [Table 1]

[0077] Test Method: Grade 2024-T3 bare aluminum panels were obtained from Erickson Metals of Minnesota, Inc., Coon Rapids, Minnesota, and were subjected to the following panel preparation process prior to bonding with a structural adhesive.

[0078] Panel preparation Bare aluminum panels were immersed in OAKITE 165 (BASF Corporation) caustic cleaning solution at 85°C (185°F) for 10 minutes. The panels were then immersed in tap water at 21°C (69.8°F) for 10 minutes, followed by a continuous tap water spray rinse for approximately 3 minutes. The panels were then immersed in Forest Products Laboratory (FPL) etching solution at 66°C (151°F) for 10 minutes. Afterwards, the panels were spray rinsed with water at 21°C (69.8°F) for approximately 3 minutes, allowed to drip dry for an additional 10 minutes, and then dried in an oven at 54°C for 30 minutes. The etched panels were ready for adhesive bonding and could be used within 8 to 12 hours.

[0079] Floating Roller Peel (FRP) Strength Test The EN2243-2:2006 method was followed. 20.3 cm x 7.6 cm x 0.16 cm (8.0 in x 3.0 in x 0.063 in) and 25.4 cm x 7.6 cm x 0.064 cm (10 in x 3 in x 0.025 in) etched panels of 2024-T3 bare aluminum were prepared for testing as described above under "Panel Preparation." Adhesives corresponding to the Examples or Comparative Examples were applied onto the 20.3 cm x 7.6 cm x 0.16 cm etched panels of 2024-T3 bare aluminum. Primed 25.4 cm x 7.6 cm x 0.064 cm aluminum panels were then applied onto the 20.3 cm x 7.6 cm x 0.16 cm panels to which adhesive had already been applied. The assembly was then pressed between metal blocks at a pressure of approximately 2 to 5 psi (13.8 to 34.5 kPa). The panel assemblies were allowed to cure for 72 hours at ambient temperature and then evaluated for floating roller peel strength according to ASTM D-3167-76 with the following modifications: Three specimens were tested for each example or comparative example, and the average value (N / 25 mm) was reported. 1.27 cm (0.5 in) wide specimens were cut along the length of the bonded aluminum panels. Tests were conducted at ambient temperature at a speed of 30.5 cm / min (6 in / min). For each test, a thinner substrate was peeled from a thicker substrate, and results were normalized to a width of 25 mm (approximately 1 inch).

[0080] Compression Modulus Test Cylindrical samples 2.54 cm (1 inch) long and 1.27 cm (0.5 inch) in diameter were prepared by pouring the mixed product into a silicone mold. The samples were left to cure at room temperature for one week. Compressive modulus testing was performed for each composition according to the ISO 604:2002 method at a test speed of 0.127 cm / min (0.05 in / min). Five specimens were tested for each composition and the average value was recorded. For testing at elevated temperatures (i.e., 90°C), the specimens were preconditioned at that temperature for at least 15 minutes before testing.

[0081] Examples 1 to 4 (EX1 to EX4) and Comparative Examples 1 to 2 (CE1 to CE2): Preparation of Agent A In each case, Part A of the epoxy-based curable composition was prepared by combining the primary amine component (EC130, 2422, or BAPP) with epoxy resin E828 in a glass vessel equipped with a laboratory stirrer. The mixture was mixed at ambient temperature for approximately 15 minutes and then heated to 80°C (176°F) using an oil bath. The mixture was continued to stir at 80°C (176°F) for 60 minutes. The mixture was then cooled to ambient temperature and transferred to a DAC 150 Speedmixer (obtained from Hauschild & Co. KG of Hamm, Westphalia, Germany). ATBN and K54 were added to the mixture and mixed at 2000 rpm for 1 minute. SF20, A140, R202, and Blue were then added and mixed at 3500 rpm for 2 minutes. The composition was then degassed under vacuum for 2 minutes while mixing. In Table 2, all concentrations are listed in weight percent. [Table 2]

[0082] Preparation of agent B The B part of the epoxy-based curable composition was prepared in each case by combining the compounds listed in Table 3 in a DAC150 Speedmixer at ambient temperature. In the first step, the epoxy resin component and wetting agent were mixed at 3000 rpm for 2 minutes. The solid components were then added and mixed at 3500 rpm for 2 minutes. The mixture was then degassed for 2 minutes by mixing at 2000 rpm under vacuum. In Table 3, all concentrations are given in weight percent. [Table 3]

[0083] Mixing Agent A and Agent B The Part A and Part B compositions were mixed together at ambient temperature in a static Quadro MFQ 10-24T Mixer obtained from Sulzer Mixpac of Winterthur, Switzerland, using a 200 mL cartridge in a volume ratio of 2:1 (Part B:Part A).

[0084] test Compression modulus and FRP tests were conducted, and the test conditions and results are shown in Table 4.

[0085] Comparative Example 3 (CE3) Samples of LOCTITE EA 9394 AERO adhesive obtained from Henkel Corporation of Dusseldorf, Germany were subjected to compressive modulus and FRP testing, and the results are presented in Table 4. [Table 4]

[0086] All references, patent documents, and patent applications cited in the above patent application are incorporated herein by reference in their entirety for consistency. In the event of any inconsistency or contradiction between the incorporated reference portions and this application, the information in the foregoing description shall prevail. The foregoing description is intended to enable one skilled in the art to practice the disclosure as set forth in the claims, and should not be construed as limiting the scope of the present disclosure, which is defined by the claims and all equivalents thereof.

Claims

1. a multifunctional epoxy resin having at least three epoxy functional groups, the multifunctional epoxy resin comprising a trifunctional epoxy resin and a tetrafunctional epoxy resin in a relative weight ratio of 1:1 to 8:1; and a base portion comprising a difunctional epoxy resin miscibly blended with the multifunctional epoxy resin; a curing agent portion comprising a polyetheramine; 1. A two-part curable shim treatment adhesive comprising: wherein either the base part or the hardener part further comprises an inorganic filler present in an amount of 10 percent to 60 percent, based on the total weight of the two-part curable shim treatment adhesive, and a phosphate ester; the multifunctional epoxy resin and the difunctional epoxy resin are present in a weight ratio of 1:1 to 6:1; the polyetheramine is present in an amount of 10 percent to 30 percent, based on the total weight of the two-part curable shim treatment adhesive; the base resin portion and / or the curing agent portion contain core-shell rubber particles, The inorganic filler comprises fumed silica. Two-component curing shim treatment adhesive.

2. 10. The two-part curable shim process adhesive of claim 1, wherein the core-shell rubber particles are present in an amount of 1 percent to 20 percent, based on the total weight of the two-part curable shim process adhesive.

3. 3. The two-part curable shim treatment adhesive of claim 1 or 2, wherein the trifunctional epoxy resin comprises triphenylmethane triglycidyl ether.

4. The two-part curable shim treatment adhesive of any one of claims 1 to 3, wherein the tetrafunctional epoxy resin comprises 4,4'-methylenebis(N,N-diglycidylaniline).

5. The two-part curable shim treatment adhesive of any one of claims 1 to 4, wherein the polyetheramine comprises trioxadecanediamine.

6. 6. A bonded assembly comprising the reaction product of the two-part curable shim treatment adhesive of any one of claims 1 to 5, said reaction product disposed between bonding surfaces of two or more respective substrates.

Images