Two component adhesive compositions for bonding untreated metal substrates

Abstract

The present disclosure relates to two component adhesive systems (e.g., two component polyurethane and two component epoxy compositions) that may be used to bond untreated metal substrates (such as untreated aluminum), thereby eliminating a metal surface pretreatment step and speeding up production processes. The present disclosure also relates to bonded reinforced composite structures prepared using such two component adhesives, methods of making such bonded reinforced composite structures, and kits for bonding untreated metal substrates onto other substrates that contain the two component adhesive systems.

Description

Attorney Docket No.: 2024P00139WOTWO COMPONENT ADHESIVE COMPOSITIONS FOR BONDING UNTREATED METAL SUBSTRATESFIELD OF THE INVENTION

[0001] The present invention relates to two component adhesive systems (e.g., two component polyurethane and / or two component epoxy adhesives) that may be used to bond untreated metal substrates (such as untreated aluminum), thereby eliminating a metal surface pretreatment step and speeding up production processes. The present invention also relates to bonded reinforced composite structures prepared using such two component adhesives, methods of making such bonded reinforced composite structures, and kits for bonding untreated metal substrates onto other substrates that contain the two component adhesive systems.BACKGROUND OF THE INVENTION

[0002] Composite structures are widely used to make vehicles in the transportation field. Examples of such composite structures include commercial trailers, train cars, aircraft components, recreational vehicles, boats and automobiles. One conventional composite structure comprises a welded aluminum frame having a polymer skin bonded to one surface, a wood skin bonded to the opposing surface and foam between the polymer and wood skins.

[0003] Two component adhesive compositions may be used as composite bonding adhesives. For example, two-component polyurethane adhesives have been widely used in both structural bonding and flexible packaging. Two component epoxy adhesives are known for their structural strength and resistance to a lot of media and are widely used in a variety of end markets, such as general industry, aerospace, and electronics.

[0004] However, in general two-component polyurethane and epoxy adhesives do not bond untreated metals (such as untreated aluminum) well. Accordingly, the aluminum surface must first be pretreated before bonding or laminating application takes place. This extra step slows down production. Good adhesion of the adhesive to each of the composite components is desirable to add strength to the composite structure. Ideally, the adhesive bonding strength will be greater than some, or all, of the materials it is bonded to. Additionally, water can infiltrate intoAttorney Docket No.: 2024P00139WO a bonded composite structure. The adhesive should retain as much of the initial bond strength as possible during and after exposure to water.

[0005] Currently, manufacturers use a multi-step process to form composite structures. In a first step the metallic frame is cleaned to remove oil, grease and dirt. Next the frame is exposed to conversion coating chemicals in a bath or spray application, rinsed with water and dried. The conversion coated frame is now ready for application of adhesive and assembly into a composite structure. This process requires multiple large tanks of chemicals, lifting and drying equipment and substantial space. In a different multi step process, the metallic frame is cleaned to remove oil, grease and dirt. Next the frame is hand wiped by workers using towels saturated with conversion chemicals such as Alodine wipes (Henkel Corp.) and dried. The conversion coated frame is now ready for application of adhesive and assembly into a composite structure. This method does not require the conversion coating tanks and related equipment. However, manually wiping the entire frame requires substantial effort and time and has the risk that workers can miss some areas of the frame.

[0006] International Publication No. WO 2022 / 132486 describes one component, liquid, moisture curable, polyurethane compositions.

[0007] There is still, however, a need for new two component adhesive compositions that exhibit increased adhesion strength to one or more composite components (e.g., deliver a nearly 100% substrate failure bond with untreated metals such as aluminum). It is also desirable to provide two component adhesive compositions that (i) exhibit increased adhesion strength without requiring conversion coatings on the metallic components, and / or (ii) retain the increased strength during and after exposure to water, and / or (iii) are compatible with existing processes and equipment. The present invention addresses these needs.

[0008] The following references may be pertinent to the present disclosure: U.S. Patent Nos. 3,309,427 and 10,155,890; U.S. Publication Nos. 2019 / 0292428, 2020 / 0140729, 2021 / 0284886, 2022 / 0056324, 2022 / 0017677, 2022 / 0106505 and 2022 / 0363965.Attorney Docket No.: 2024P00139WOSUMMARY OF THE INVENTION

[0009] The present inventors have developed two component systems that surprisingly provide increased adhesion strength to composite components, e.g., untreated metals, such as untreated aluminum, thereby eliminating the need for a metal surface pretreatment step and speeding up production processes.

[0010] In one aspect, the present invention relates to a bonded reinforced composite structure comprising:(i) at least one untreated metal frame; and(ii) a room -temperature curable two component adhesive composition comprising:(a) a first component; and(b) a second component; wherein the first component and / or the second component comprises an acid.

[0011] In one embodiment, the first component comprises an acid. In one embodiment, the first component comprises an acid and the second component is free of an acid.

[0012] In one embodiment, the second component comprises an acid. In one embodiment, the second component comprises an acid and the first component is free of an acid.

[0013] In one embodiment, both the first component and the second component comprise an acid.

[0014] In one embodiment, the two component adhesive composition is a two component polyurethane composition.

[0015] In one embodiment, the first component comprises a polyol component and the second component comprises a polyisocyanate.Attorney Docket No.: 2024P00139WO

[0016] In one embodiment, the two component adhesive composition is a two component epoxy composition.

[0017] In one embodiment, the first component comprises an epoxy component and the second component comprises curing agent component.

[0018] In one aspect, the present invention relates to a bonded reinforced composite structure comprising:(i) at least one untreated metal frame; and(ii) a room-temperature curable two component adhesive composition comprising:(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or(B)(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; andAttorney Docket No.: 2024P00139WO wherein the room-temperature curable two component adhesive composition is curable at a temperature of less than about 50° C.

[0019] In one embodiment of the bonded reinforced composite structure: in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition.

[0020] In one embodiment of the bonded reinforced composite structure the room-temperature curable two component adhesive composition is curable at a temperature of between about -30° C and less than about 50° C.

[0021] In one embodiment, the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

[0022] In one embodiment, the acid is selected from the group consisting of phosphoric acid, sulfuric acid, nitric acid, and any combination thereof. In one embodiment, the acid is phosphoric acid. In one embodiment, the acid is nitric acid. In one embodiment, the acid is sulfuric acid.

[0023] In one embodiment, the acid is an inorganic acid.

[0024] In one embodiment, the untreated metal is selected from the group consisting of untreated aluminum and untreated steel. In one embodiment, the untreated metal is untreated aluminum (such as, e.g., mill grade aluminum). In one embodiment, the untreated metal is untreated stainless steel (such as, e.g., mill grade stainless steel).

[0025] In one embodiment, the curing agent is an amine, a polymercaptan, or any combination of any of the foregoing.Attorney Docket No.: 2024P00139WO

[0026] In another aspect, the present invention relates to a method of making a bonded reinforced composite structure, the method comprising:(i) providing at least one an untreated metal frame having at least one bonding surface;(ii) providing a room-temperature curable two component adhesive composition comprising:(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises an acid; and(iii) applying the room-temperature curable two component adhesive composition to the at least one bonding surface of the untreated metal frame to form the bonded reinforced composite structure.

[0027] In another aspect, the present invention relates to a method of making a bonded reinforced composite structure, the method comprising:(i) providing an untreated metal frame having at least one bonding surface;(ii) providing a room-temperature curable two component adhesive composition comprising:(a) an epoxy component;(b) a curing component (e.g., an amine or a polymercaptan curing component); wherein the epoxy component and / or the curing component comprises an acid; and(iii) applying the room-temperature curable two component adhesive composition to the at least one bonding surface of the untreated metal frame to form the bonded reinforced composite structure.Attorney Docket No.: 2024P00139WO

[0028] In another aspect, the present invention relates to a method of making a bonded reinforced composite structure, the method comprising:(i) providing at least one an untreated metal frame having at least one bonding surface;(ii) providing a room-temperature curable two component adhesive composition comprising:(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or(B)(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition;(iii) applying the room -temperature curable two component adhesive composition to the at least one bonding surface of the untreated metal frame; and(iv) allowing the room-temperature curable two component adhesive composition to cure at a temperature of less than about 50° C to form the bonded reinforced composite structure.Attorney Docket No.: 2024P00139WO

[0029] In one embodiment of the method: in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid based on 100 wt.% of the combined two component composition.

[0030] In one embodiment, the room-temperature curable two component adhesive composition is allowed to cure at a temperature of between about -30° C and less than about 50° C.

[0031] In one embodiment of any of the methods described herein, the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

[0032] In one embodiment of any of the methods described herein, the acid is selected from the group consisting of phosphoric acid, sulfuric acid, nitric acid, and any combination thereof. In one embodiment, the acid is phosphoric acid. In one embodiment, the acid is nitric acid. In one embodiment, the acid is sulfuric acid.

[0033] In one embodiment of any of the methods described herein, the acid is an inorganic acid.

[0034] In one embodiment of any of the methods described herein, the at least one untreated metal frame comprises an untreated aluminum (such as, e.g., mill grade aluminum) frame. In one embodiment of any of the methods described herein, the at least one untreated metal frame comprises an untreated stainless steel (such as, e.g., mill grade stainless steel) frame.

[0035] In another aspect, the present invention relates to a bonded reinforced composite structure prepared by any of the methods described herein.

[0036] In another aspect, the present invention relates to a kit for bonding an untreated metal substrate onto a second substrate, the kit comprising:Attorney Docket No.: 2024P00139WO(a) a first component; and(b) a second component; wherein the first component and / or the second component comprises an acid; and the kit is a room-temperature curable two component adhesive composition.

[0037] In one embodiment of any of the kits described herein:(a) the first component comprises a polyol component; and(b) the second component comprises a polyisocyanate component.

[0038] In one embodiment of any of the kits described herein:(a) the first component comprises an epoxy component; and(b) the second component comprises a curing agent component.

[0039] In another aspect, the present invention relates to a kit for bonding an untreated metal substrate onto a second substrate, the kit comprising:(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid based on 100 wt.% of the combined two component composition; or(B)Attorney Docket No.: 2024P00139WO(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; and the kit is a room-temperature curable two component adhesive composition that is curable at a temperature of less than about 50° C.

[0040] In one embodiment: in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition.

[0041] In one embodiment, the kit is a room-temperature curable two component adhesive composition that is curable at a temperature of between about -30° C and less than about 50° C.

[0042] In one embodiment of any of the kits described herein, the second substrate comprises wood, plastic, expanded polystyrene foam, high-pressure laminate, fiber glass reinforced plastic, glass, an additional treated or untreated metal substrate, or any combination thereof.

[0043] In one embodiment of any of the kits described herein, the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

[0044] In one embodiment of any of the kits described herein, the acid is selected from the group consisting of phosphoric acid, sulfuric acid, nitric acid, and any combination thereof. In oneAttorney Docket No.: 2024P00139WO embodiment, the acid is phosphoric acid. In one embodiment, the acid is nitric acid. In one embodiment, the acid is sulfuric acid.

[0045] In one embodiment of any of the kits described herein, the acid is an inorganic acid.

[0046] In one embodiment, the curing agent component comprises an amine, a poly mercaptan, or a combination of any of the foregoing.BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 illustrates the adhesion of two component polyurethane adhesive systems in Example 1 (Compositions 1-9) to a sample of mill grade aluminum after the peel test.

[0048] FIG. 2 illustrates the adhesion of two component epoxy adhesive systems in Example 2 (Compositions 1-9) to a sample of mill grade aluminum after the peel test.DETAILED DESCRIPTION OF THE INVENTION

[0049] As used herein, the term “about” when referring to a number or a numerical range means that the number or numerical range referred to is an approximation within experimental variability (or within statistical experimental error), and thus the number or numerical range may vary from, for example, between 1% and 15% of the stated number or numerical range.

[0050] As used herein, the term “comprising” (and related terms such as “comprise” or “comprises” or “having” or “including”) includes, but is not limited to, those embodiments, for example, an embodiment of any composition of matter, composition, method, or process, or the like, that “consist of’ or “consist essentially of’ the described features.

[0051] All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of "from 2 to 10" is inclusive of the endpoints, 2 and 10, and all the intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and / or values. As used herein, approximating language may beAttorney Docket No.: 2024P00139WO applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about," may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "from about 2 to about 4" also discloses the range "from 2 to 4." The term "about" may refer to plus or minus 10% of the indicated number. For example, "about 10%" may indicate a range of 9% to 11 ", and "about 1" may mean from 0.9-1.1. Other meanings of "about" may be apparent from the context, such as rounding off, so, for example "about 1" may also mean from 0.5 to 1.4.

[0052] Unless specifically noted, throughout the present specification and claims the term molecular weight when referring to a polymer refers to the polymer’s number average molecular weight (Mn). The number average molecular weight Mncan be calculated based on end group analysis (OH numbers according to DIN EN ISO 4629, free NCO content according to EN ISO 11909) or can be determined by gel permeation chromatography according to DIN 55672 with THF as the eluent. If not stated otherwise, all given molecular weights are those determined by gel permeation chromatography.

[0053] When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.Acid Component

[0054] The two component adhesive compositions described herein include at least one acid (e.g., at least one acid that is not a carboxylic acid). Suitable acids that may be used in any of the compositions described herein include inorganic acids, organic acids (that are not carboxylic acids), or any combination of the foregoing.Attorney Docket No.: 2024P00139WO

[0055] In one embodiment, any of the two component adhesive compositions described herein include at least one inorganic acid.

[0056] Suitable acids that may be used in any of the two component adhesive compositions described herein include, but are not limited to, sulfuric acid, sulphurous acid, disulfuric acid, peroxydisulfuric acid, thiosulfuric acid, nitric acid, hyponitrous acid, phosphoric acid, hydrochloric acid, chlorous acid, chloric acid, perchloric acid, hydrofluoric acid, phosphinic acid, phosphonic acid, hypodiphosphoric acid, diphosphoric acid, triphosphoric acid, boric acid, hydrogen sulfide, chromous acid, chromic acid, perchromic acid, selenic acid, permanganic acid, silicic acid, antimonic acid, molybdic acid, silicofluoric acid, sulfonic acids (e.g., methanesulfonic acid, ethanesulfonic acid), and any combination of any of the foregoing.

[0057] In one embodiment, the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methane sulfonic acid, ethane sulfonic acid, and any combination of any of the foregoing.

[0058] In one embodiment, the acid is selected from the group consisting of phosphoric acid, sulfuric acid, nitric acid, and any combination thereof. In one embodiment, the acid is phosphoric acid. In one embodiment, the acid is nitric acid. In one embodiment, the acid is sulfuric acid.

[0059] In one embodiment, the acid is an inorganic acid.

[0060] In one embodiment, the acid is methanesulfonic acid. In one embodiment, the acid is ethanesulfonic acid.

[0061] It is also possible for some or all of the acid component to be in a weak salt form such as the reaction product of an acid with a tertiary amine.

[0062] In one embodiment, when the two component system is a two component polyurethane system, the one or more acids is present in the polyol component. In one embodiment, when the two component system is a two component polyurethane system, the one or more acids is present in the polyisocyanate component. In one embodiment, when the two component system is a two component polyurethane system, the one or more acids is present in the polyol component andAttorney Docket No.: 2024P00139WO the polyisocyanate component. Different acids, or combinations of acids, may be used in each component.

[0063] In one embodiment, when the two component system is a two component epoxy system, the one or more acids is present in the epoxy component. In one embodiment, when the two component system is a two component epoxy system, the one or more acids is present in the curing agent component. In one embodiment, when the two component system is a two component polyurethane system, the one or more acids is present in the epoxy component and the curing agent component. Different acids, or combinations of acids, may be used in each component.

[0064] In certain embodiments of any of the two component adhesive compositions described herein, the acid (or combination of acids) is present in an amount from about 0.01 wt. % to about 5 wt. %, such as from about 0.035 wt.% to about 3 wt.%, from about 0.035 wt.% to about 2 wt. %, from about 0.05 wt.% to about 1.5 wt.%, from about 0.05 wt.% to about 1 wt.%, from about 0.05 wt.% to about 0.5 wt.%, from about 0.08 wt. % to about 0.5 wt.%, or from about 0.1 wt. % to about 0.5 wt.% (based on 100 wt.% of the combined two component composition).

[0065] Exemplary, non-limiting, wt. % ranges for the acid (based on 100 wt.% of the combined two component composition) are shown in Table 1.Table 1Two Component Polyurethane Systems

[0066] Suitable two component polyurethane systems that may be used in the present invention are readily known to one of ordinary skill in the art. Exemplary, but non limiting, examples of polyol and polyisocyanate components that may be used are provided below. See also, e.g., U.S. Patent Nos. 3,309,427 and 10,155,890, U.S. Publication Nos. 2019 / 0292428, 2020 / 0140729, 2021 / 0284886, 2022 / 0056324, 2022 / 0017677, 2022 / 0106505, and 2022 / 0363965, andAttorney Docket No.: 2024P00139WOInternational Publication No. WO 2023 / 284974, each of which is hereby incorporated by reference in its entirety.Polyol Component

[0067] Suitable polyols that can be used in the two component polyurethane compositions described herein include, but are not limited to, polyols used for the production of polyurethanes, including, without limitation, polyether polyols, polyester polyols, polycarbonate polyols, polybutadiene polyols, polyacetal polyols, polyamide polyols, polyesteramide polyols, polyalkylene polyether polyols, polythioether polyols, and any mixture of any of the foregoing.

[0068] In one embodiment, the polyol component comprises a polyether polyol, a polyester polyol, a polycarbonate polyol, or any mixtures of any of the foregoing. In one embodiment, the polyol component comprises a polyether polyol.

[0069] Suitable polyester polyols that can be used in the two component polyurethane compositions described herein include, but are not limited to, those that are obtainable by reacting, in a polycondensation reaction, dicarboxylic acids with polyols. The dicarboxylic acid may be aliphatic, cycloaliphatic or aromatic, and / or a derivative thereof, such as, for example, an anhydride, an ester or an acid chloride. Non-limiting examples include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecandioic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric fatty acid, dodecane dioic acid and dimethyl terephthalate. Non-limiting examples of suitable polyols include monoethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 3-methylpentane- 1,5-diol, neopentyl glycol (2, 2-dimethyl- 1,3-propanediol), 1,6-hexanediol, 1,8-otaneglycol cyclohexanedimethanol, 2-methylpropane-l,3-diol, diethyleneglycol, triethyleneglycol, tetraethyleneglycol, polyethyleneglycol, dipropyleneglycol, tripropyleneglycol, tetrapropyleneglycol, polypropyleneglycol, dibutyleneglycol, tributyleneglycol, tetrabutyleneglycol and polybutyleneglycol. Alternatively, they may be obtained by ring-opening polymerization of cyclic esters, such as, for example, caprolactone. Polyester polyols are commercially available, for example, Piothane polyols available from Panolam IndustriesAttorney Docket No.: 2024P00139WOInternational and Dynacoll polyols available from Evonik. Other suppliers include Stepan, COIM and Lanxess. In one embodiment, the polyester polyol is polyhexanediol adipate.

[0070] Suitable polyether polyols that can be used in the two component polyurethane compositions described herein include, but are not limited to, linear and branched polyethers having hydroxyl groups. Non-limiting examples of the polyether polyol may include a polyoxyalkylene polyol, such as, for example, polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like. Additionally, a homopolymer and a copolymer of the polyoxyalkylene polyols may also be used. Suitable copolymers of the polyoxyalkylene polyols may include an adduct of at least one compound selected from, for example, ethylene glycol, propylene glycol, di ethylene glycol, dipropylene glycol, tri ethylene glycol, 2-ethylhexanediol-l,3, glycerin, 1,2,6-hexane triol, trimethylol propane, trimethylol ethane, tris(hydroxyphenyl)propane, triethanolamine, triisopropanolamine, ethylenediamine and ethanolamine. In one embodiment, the polyether polyol comprises polypropylene glycol. In one embodiment, the polyether polyol has a number average molecular weight of from about 500 to about 6,000 Daltons, such as from about 1,000 to about 3,000 Daltons. In one embodiment, the polyether polyol may comprise a mixture of poly ether polyols.

[0071] Suitable polycarbonate polyols that can be used in the two component polyurethane compositions described herein include, but are not limited to, those obtained by reaction of a carbon acid derivative, e g., diphenyl carbonate, dimethyl carbonate or phosgene, with a diol. Suitable examples of such diols include, for example, ethylene glycol, 1,2- and 1,3 -propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8 -octanediol, neopentyl glycol, 1,4-bishydroxymethyl cyclohexane, 2-methyl-l,3-pro-panediol, 2,2,4-trimethyl pentanediol -1,3, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, bisphenol F, tetrabromobisphenol A, and lactone-modified diols. In some embodiments, the diol component contains about 40 wt. % to about 100 wt. % hexanediol, such as, e.g., 1,6-hexanediol, and / or a hexanediol derivative. In one embodiment, the diol component includes, in addition to terminal OH groups, one or more ether or ester groups. In one embodiment, the polycarbonate polyol is substantially linear or is linear. In other embodiments, the polycarbonate polyol is branched by the incorporation of polyfunctional components, such as low-molecular weight polyols. Suitable examples include, for example, glycerol, trimethylol propane, hexanetriol-1,2,6, butanetriol-1,2,4,Attorney Docket No.: 2024P00139WO trimethylol propane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, 1, 3,4,6- dianhydrohexites, and any combination thereof.

[0072] Suitable polyols can also be hydroxyl-terminated prepolymers (prepolymer polyols) which may, for example, be prepared by reacting a polyisocyanate with a stoichiometric excess of a polyol.

[0073] In one embodiment, the polyol content in the polyol component is from about 20 wt.% to 100 wt.% (based on the weight of polyol component alone). In one embodiment, the polyol content is from about 90 wt.% to about 100 wt.% (based on the weight of polyol component alone). In another embodiment, the polyol content is from about 20 wt.% to about 60 wt.% (based on the weight of polyol component alone).

[0074] Exemplary, non-limiting, wt.% ranges for polyol content in the polyol component (based on the weight of polyol component alone) by are shown in Table 2.Table 2Polyisocyanate Component

[0075] Polyisocyanates that can be used in the two component polyurethane compositions described herein include single polyisocyanates and mixtures of polyisocyanates. In one embodiment, the weight average functionality of the polyisocyanate or polyisocyanate mixture is from 2.0 to about 2.7, such as from 2.0 to about 2.6 or from 2.0 to about 2.5, e.g., to enhance bond strength of the adhesive composition. The weight average functionality of a mixture of polyisocyanates (f NCO) is calculated as follows: f NCO = (wt. % NCO1 * fNCOl) + (wt. % NCOi * fNCOi) + . .. In other words, the weight average functionality is the sum of each weight % of a given polyisocyanate based on the total polyisocyanate weight percentage multiplied by its functionality. For example, an adhesive composition containing 30 wt. %, based on the total composition weight, of a polyisocyanate having functionality of 2.7 and 15 wt.%, based on theAttorney Docket No.: 2024P00139WO total composition weight, of a poly isocyanate having a functionality of 2.0 yields a weight average functionality of (30 / (30+15)) * 2.7 + (15 / (30+15)) * 2 = 2.47.

[0076] Suitable poly isocyanates that can be used in the two component polyurethane compositions described herein include, but are not limited to, diisocyanates, such as 4,4'-diphenylmethane diisocyanate (4,4’ MDI), toluene diisocyanate, 1,4-diisocyanatobenzene (PPDI), 2, d'diphenylmethane diisocyanate, 1,5 -naphthalene diisocyanate, bitolylene diisocyanate, 1,3-xylene diisocyanate, TMXDI (tetramethylxylyl ene diisocyanate), l,6-diisocyanato-2,4,4- trimethylhexane, CHDI (cyclohexene diisocyanate); BDI (butylene diisocyanate); He.XDI (bis(isocyanatomethyl)cyclohexane); IPDI (isophorone diisocyanate); H12MDI (methylenebis(cyclohexyl isocyanate), polymeric versions of any of the above (such as, e.g., polymeric MDI), modified versions of the any of the foregoing (such as allophanates, carbodiimides and biurets), and any mixture of any of the foregoing.

[0077] Suitable polyisocyanates can also be isocyanate terminated prepolymers which can, for example, be prepared by reacting a polyol with a stoichiometric excess of a polyisocyanate.

[0078] In one embodiment, the polyisocyanate content in the polyisocyanate component is from about 20 wt.% to 100 wt.% (based on the weight of the poly isocyanate component alone). In one embodiment, the polyisocyanate content is from about 90 wt.% to about 100 wt.% (based on the weight of the polyisocyanate component alone). In another embodiment, the polyisocyanate content is from about 20 wt.% to about 60 wt.% (based on the weight of the polyisocyanate component alone).

[0079] Exemplary wt.% ranges of polyisocyanate content in the polyisocyanate component (based on the weight of polyisocyanate component alone) are shown in Table 3.Table 3Attorney Docket No.: 2024P00139WOTwo Component Epoxy Systems

[0080] Suitable epoxy components that may be used in the two component epoxy systems useful in the present invention are readily known to one of ordinary skill in the art. Exemplary, but non limiting, examples of epoxy components that may be used are described in, e.g., U.S. Patent No. 5,258,427, and International Publication Nos. WO 2021 / 127128, WO 2022 / 046836, WO 2022 / 250884, WO 2023 / 043757, WO 2023 / 091806, and WO 2023 / 288149. See also, e.g., Chemistry and Technology of Epoxy Resins by B Ellis, Springer 1993, Chapters 1 and 2, and Epoxy Resins by M Dombusch, Vincentz, 2016, Chapter 2, each of which is hereby incorporated by reference in its entirety.

[0081] Exemplary wt.% ranges of epoxy content in the epoxy component (based on the weight of the epoxy component alone) are shown in Table 4.Table 4Curing Agent Component

[0082] Suitable curing agents that may be used in the two component epoxy systems useful in the present invention are readily known to one of ordinary skill in the art. Exemplary, but non limiting, examples of curing agent components that may be used include, but are not limited, to amines (such as primary amines, secondary amines, tertiary amines, and any combination thereof, including, but not limited to, aromatic amines, aliphatic amines, cycloaliphatic amines, and any combination thereof), mercaptans, and any combination of any of the foregoing.

[0083] Primary amines undergo an addition reaction with the epoxide group to form a hydroxyl group and a secondary amine. The secondary amine can further react with an epoxide to form a tertiary amine and an additional hydroxyl group. Kinetic studies have shown the reactivity of theAttorney Docket No.: 2024P00139WG primary amine to be approximately double that of the secondary amine. Use of a difunctional or polyfunctional amine forms a three-dimensional cross-linked network. Tertiary amines can be used alone as the curing agent component, or as an accelerator in combination with polyamines, polyamides and / or amidoamines; or as a catalyst with thiols. Aliphatic, cycloaliphatic and aromatic amines may also be employed as epoxy curatives. The overall reactivity potential for different amine curatives can roughly be ordered: aliphatic amines > cycloaliphatic amines > aromatic amines, although aliphatic amines with steric hindrance near the amino groups may react as slowly as some of the aromatic amines.

[0084] Thiols, also known as mercaptans, can also be used as the curing agent component. These materials contain a sulfur which reacts very readily with the epoxide group, even at ambient or sub-ambient temperatures.

[0085] Suitable examples of curing agent components include, but are not limited to, Capcure products such as Capcure 3-800 and Capcure 40 secHV (available from Gabriel US), Ancamine products (available from Evonik Industries AG, Germany) and Jeffamine products (available from Huntsman US).

[0086] Exemplary wt.% ranges of epoxy-reactive curing agent content in the curing agent component (based on the weight of the curing agent component alone) are shown in Table 5.Table 5Additional Additives

[0087] The two component adhesive compositions described herein may optionally include additional additives. The optional additional additives may be present in the composition at a weight percent from greater than zero, about 0.1 percent, about 0.5 percent, or about one percent, to about five percent, about 30, about 50 percent, or about 80 percent, based on the total weightAttorney Docket No.: 2024P00139WO of the composition, or a weight percentage between any pair of the foregoing values. The weight percentage of the optional additional additives may be applied to the combined total of all additional additives present or to each additional additive separately.

[0088] Some examples of additional additives include, but are not limited to, crosslinkers, chain extenders, humectants, thixotropy, nucleating agents, surfactants, adhesion promoter, molecular sieves, diluents, anti-settling agents, flame-retardant enhancers, and any combination thereof. In some embodiments, the optional additional additives include catalysts, waxes, release agents, reinforcing fillers, tougheners, non-reactive polymers, pigments, heat stabilizers, UV stabilizers, plasticizers, rheology modifiers, processing aids, lubricants, mold release agents, biocides, or component or combinations thereof. Suitable reinforcing fillers include, but are not limited to, mica, calcium carbonate, Kaolin, quartz, mineral fillers and glass fibers.

[0089] Exemplary, but non limiting, wt.% ranges of additive content in any of the polyol component, polyisocyanate component, epoxy component, or epoxy-reactive curing agent components described herein (based on the weight of any individual component alone) are shown in Table 6.Table 6

[0090] The two component adhesive compositions described herein may be prepared by methods known to one of ordinary skill in the art.

[0091] Typically, the two components of the acid-containing systems described herein are packaged separately. The two components of such systems are mixed together during application of the systems. However, the two components of some two component systems can also be physically mixed together along with an acid to form a pseudo two component system. Without a form of energy initiation, such as light (see, e.g., chapter 14, Epoxy Adhesive Formulations by Edward M. Petrie, McGraw Hill, 2005), the systems remain stable. Upon emission of a form ofAttorney Docket No.: 2024P00139WO energy onto the systems, the curing ingredients get activated which initiate the curing reaction. For example, U.S. Patent No. 4,256,828 describes a pseudo two component system containing epoxide functional photopolymers / monomers and cationic photoinitiators. When light is emitted to the system, it activates cationic photoinitiators and starts the curing reaction. Such a pseudo two component system when containing acid as described above can also be used to bond untreated metals for improved adhesion.

[0092] Percentage substrate failure is usually used to judge the bonding strength of the adhesive, or in another term, the adhesion. 100% substrate failure means that the bonding strength of the adhesive is higher than the strength of at least one of the substrates, which is the most desirable.0% substrate failure is the least desirable. As described herein, the percentage adhesion is recorded as the percentage of substrate failure. For composite panels used in a variety of industries, it is desired to have a % adhesion of at least about 30%, preferably at least about 50%, more preferably at least about 70% or at least about 80%, and most preferably about 90% or about 95%. An adhesion % of 100% would be ideal as it denotes the substrate fails before the adhesive bond. While some of these adhesion strengths can be achieved with conventional adhesives in combination with anodized or conversion coated aluminum frame members, it has not been possible to consistently achieve even the 30% adhesion strength using conventional adhesives with mill grade aluminum frame members, e.g. aluminum frame members as received from a mill with no cleaning and no conversion coating or anodizing.

[0093] As used herein, in one embodiment, the term “room temperature” when referring to curing or a curable product, means that a curing process occurs at temperatures ranging from about -30° C to about 50° C. In another embodiment, the term “room temperature” when referring to curing or a curable product, means that a curing process occurs at a temperature of less than about 50° C.ExamplesSystem Components

[0094] LOCTITE® UK M-06FL is a two component polyurethane adhesive available from Henkel Corp. (Bridgewater, NJ). The poly isocyanate component is based on a commercially available modified aromatic polyisocyanate and the polyol component is based on a mixture ofAttorney Docket No.: 2024P00139WO commercially available polyols and contains inorganic additives. LOCTITE® EA E-60HP is a two component epoxy adhesive available from Henkel Corp. (Bridgewater, NJ). The epoxy component is based on aromatic epoxy resin and the curing agent component is based on a mixture of polyamines. Phosphoric acid (85%) was obtained from Univar. Methanesulfonic acid was obtained from Sigma-Aldrich. Sulfuric acid (80%) was obtained from PVS Chemical Solutions (93%, diluted to 80%). Propionic acid was obtained from Sigma-Aldrich.Peel Testing

[0095] The percent adhesion was tested by applying the test composition, after mixing, to an aluminum frame at about 10 gram per square foot, and placing a second_substrate, Lauan plywood, on the test composition disposed on the frame forming an assembly for bonding. The assembly was clamped until the adhesive was fully cured. Afterwards, the assembly was peeled manually with a spatula. The_percentage of Lauan plywood failure was visually assessed based on the amount of wood which remained bonded to aluminum. If there is no adhesive failure and 100% of the failure is from plywood, the result was recorded as 100% (of substrate failure) which is the most desirable case. If plywood separated completely from the aluminum surface without any plywood left on the surface of aluminum, the result was recorded as 0% (of substrate failure) the most undesirable case.Example 1; Two Component Polyurethane System Testing

[0096] The commercially available two component polyurethane product LOCTITE® UK M06FL (Henkel Corp.) was used as a benchmark in this example. The application of this product requires mixing of the resin part (the polyisocyanate component) and the hardener part (the isocyanate-reactive polyol component) before application to the substrate. The resin: hardener mixing ratio by weight was 50 : 100 at room temperature. In the examples shown in Table 7, the acid was added to the polyol component. The percentage of the acid in the examples is based on total weight of the two component mixture, not the percentage of the polyol component. In Composition 3, the aluminum frame was pretreated using Henkel's commercially available Alodine 5700 surface pretreatment chemical, followed by application of the polyurethane adhesive system. The percent wood substrate failure results are shown in Table 7.Attorney Docket No.: 2024P00139WOTable 7

[0097] FIG. 1 illustrates the adhesion of a two component polyurethane adhesive systems of Example 1 (See Table 7 for Compositions 1-9) to a sample of mill grade aluminum after the peel test. The numbering of samples in FIG. 1 corresponds to the Compositions shown in Table 7.Attorney Docket No.: 2024P00139WO

[0098] As can be seen from Table 7, LOCTITE® UK M-06FL alone (Composition 1) does not bond an untreated aluminum frame well, with an undesirable 15% wood substrate failure. With surface pretreatment (Composition 3), LOCTITE® UK M-06FL provided good bonding, with 95% wood substrate failure. When a non-carboxylic acid is added to the LOCTITE® UK M- 06FL system, even with untreated aluminum, the results showed significant improvement compared to Composition I, with e.g., 80%, 90% or greater wood substrate failure (Compositions 2 and 4-8). Addition of propionic acid resulted in a wood substrate failure of 55% (Composition 9).Example 2: Two Component Epoxy System Testing

[0099] The commercially available two component epoxy product LOCTITE® EA E-60HP (Henkel Corp.) was used as a benchmark in this example. The application of this product requires mixing of the epoxy component and the curing agent component before application to the substrate. The epoxy: curing agent mixing ratio by weight was 100:50 at room temperature. In the examples shown in Table 4, the acid was added to the curing agent component. The percentage of the acid in the examples is based on total weight of the two component mixture, not the percentage of the individual curing agent component. In Composition 2, the aluminum frame was pretreated using Henkel's commercially available Alodine 5700 surface pretreatment chemical, in comparison Compositions 1 and 3-9 were applied to the aluminum frames without pretreatment. Then followed by application of the epoxy adhesive system, assembly and cure in the manner described in Example 1.Attorney Docket No.: 2024P00139WO

[0100] The percent wood substrate failure results are shown in Table 8.Table 8

[0101] FIG. 2 illustrates the adhesion of two component epoxy adhesive systems in Example 2 (Compositions 1-9) to a sample of mill grade aluminum after the peel test.

[0102] As can be seen from Table 8, LOCTITE® EA E-60HP alone (Composition 1) does not bond an untreated aluminum frame well, with an undesirable 10% wood substrate failure. WithAttorney Docket No.: 2024P00139WO metal surface pretreatment (Composition 2), LOCTITE® EA E-60HP provided good bonding, with 95% wood substrate failure. When a non-carboxylic acid is added to the LOCTITE® EA E- 60HP system, even with untreated aluminum, the results showed significant improvement compared to Composition 1, with 95% wood substrate failure (Compositions 3-8). Addition of propionic acid resulted in a wood substrate failure of 70% (Composition 9).

[0103] All patents and publications cited herein are incorporated by reference in their entirety.

Claims

Attorney Docket No.: 2024P00139WOWHAT IS CLAIMED IS;1. A bonded reinforced composite structure comprising:(i) at least one untreated metal frame; and(ii) a room-temperature curable two component adhesive composition comprising:(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or(B)(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; and wherein the room-temperature curable two component adhesive composition is curable at a temperature of less than about 50° C.

2. The bonded reinforced composite structure of claim 1, wherein:Attorney Docket No.: 2024P00139WO in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition.

3. The bonded reinforced composite structure of claim 1, wherein the roomtemperature curable two component adhesive composition is curable at a temperature of between about -30° C and less than about 50° C.

4. The bonded reinforced composite structure of claim 1, wherein the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

5. The bonded reinforced composite structure of claim 1, wherein the acid is an inorganic acid.

6. The bonded reinforced composite structure of claim 1 , wherein the at least one untreated metal frame comprises an untreated aluminum frame.

7. The bonded reinforced composite structure of claim 1, wherein the curing agent component comprises an amine, a polymercaptan, or a combination of any of the foregoing.

8. A method of making a bonded reinforced composite structure, the method comprising:(i) providing at least one an untreated metal frame having at least one bonding surface;(ii) providing a room-temperature curable two component adhesive composition comprising:Attorney Docket No.: 2024P00139WO(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or(B)(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition;(iii) applying the room-temperature curable two component adhesive composition to the at least one bonding surface of the untreated metal frame; and(iv) allowing the room-temperature curable two component adhesive composition to cure at a temperature of less than about 50° C to form the bonded reinforced composite structure.

9. The method of claim 8, wherein: in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; orAttorney Docket No.: 2024P00139WO in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition.

10. The method of claim 8, wherein the room -temperature curable two component adhesive composition is allowed to cure at a temperature of between about -30° C and less than about 50° C.

11. The method of claim 8, wherein the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

12. The method of claim 8, wherein the acid is an inorganic acid.

13. The method of claim 8, wherein the at least one untreated metal frame comprises an untreated aluminum frame.

14. The method of claim 8, wherein the curing agent component comprises an amine, a polymercaptan, or a combination of any of the foregoing.1 . A bonded reinforced composite structure prepared by the method of claim 8.

16. A kit for bonding an untreated metal substrate onto a second substrate, the kit comprising:(A)(a) a polyol component; and(b) a polyisocyanate component; wherein the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; orAttorney Docket No.: 2024P00139WO(B)(a) an epoxy component;(b) a curing component; and wherein the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1.5 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; and the kit is a room-temperature curable two component adhesive composition that is curable at a temperature of less than about 50° C.

17. The kit of claim 17, wherein: in (A), the polyol component and / or the polyisocyanate component comprises from about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition; or in (B), the epoxy component and / or the curing component comprises about 0.05 wt.% to about 1 wt.% of at least one acid that is not a carboxylic acid, based on 100 wt.% of the combined two component composition.

18. The kit of claim 17, wherein the kit is a room -temperature curable two component adhesive composition that is curable at a temperature of between about -30° C and less than about 50° C.

19. The kit of claim 17, wherein the acid is selected from the group consisting of nitric acid, sulfuric acid, phosphonic acid, phosphoric acid, disphosphoric acid, methanesulfonic acid, ethanesulfonic acid, and any combination of any of the foregoing.

20. The kit of claim 17, wherein the acid is an inorganic acid.

21. The kit of claim 17, wherein the at least one untreated metal frame comprises an untreated aluminum frame.Attorney Docket No.: 2024P00139WO22. The kit of claim 17, wherein the curing agent component comprises an amine, a polymercaptan, or a combination of any of the foregoing.

23. The kit of claim 17, wherein the second substrate comprises wood, plastic, expanded polystyrene foam, high-pressure laminate, fiber glass reinforced plastic, glass, an additional treated or untreated metal substrate, or any combination thereof.

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