Aqueous sol-gel coating compositions, articles made therefrom, and methods of making such compositions

Abstract

Described herein is an aqueous composition and a method of making a sol-gel coating. The aqueous composition comprises (a) an organometallic salt, wherein the organometallic salt comprises an acid-stable metal alkoxide, a metal carboxylate, or a mixture thereof; and (b) an aminosilane, wherein the aqueous composition has a pH less than or equal to 7. Such sol-gel coating compositions can be used to adhere an organic resin to a metal substrate.

Description

Technical Field

[0001] This paper discloses a method for preparing aqueous sol-gel coatings using aminosilanes by employing acid-stabilized components and / or acidic conditions to generate surface coatings. Such coatings can promote good adhesion between metallic substrates and resin materials, such as organic adhesives. Summary of the Invention

[0002] The aim is to identify aqueous sol-gel compositions derived from aminosilanes that exhibit good adhesive strength.

[0003] In one aspect, an aqueous composition is described, the aqueous composition comprising: (a) Organometal salts, wherein the organometal salts include metal acetates, acid-stable metal alkoxides, or mixtures thereof; and (b) Aminosilanes, The aqueous composition has a pH of less than or equal to 7.

[0004] In another aspect, an article is described that comprises: (i) Metal substrate; (ii) Adhesive resin layer; and (iii) A sol-gel layer located between a metal substrate and an adhesive resin layer, wherein the sol-gel layer is derived from an aqueous composition comprising: (a) an organometallic salt, wherein the organometallic salt includes a metal acetate, an acid-stable metal alkoxide, or a mixture thereof; and (b) an aminosilane, wherein the aqueous composition has a pH of less than or equal to 7.

[0005] In yet another implementation, a kit is described that includes: (a) An aqueous solution comprising an organometallic salt, wherein the organometallic salt comprises a metal acetate, an acid-stable metal alkoxide, or a mixture thereof; and (b) Neutralized aminosilane, wherein the mixture of components (a) and (b) has a pH less than or equal to 7.

[0006] In yet another embodiment, a method for preparing an aqueous sol-gel coating composition is described. The method includes: (a) Providing an organometallic salt, wherein the organometallic salt comprises a metal acetate, an acid-stable metal alkoxide, or a mixture thereof; and (b) Contacting an organometallic salt with an aminosilane, wherein the aqueous sol-gel coating composition has a pH less than or equal to 7.

[0007] The above description is not intended to illustrate every embodiment. Details of one or more embodiments of the invention are also set forth in the following detailed description. Other features, objectives, and advantages will become apparent from this specification and the claims. Detailed Implementation

[0008] As used herein, the terms “an,” “a,” and “the” are used interchangeably and refer to one or more.

[0009] The term “and / or” is used to indicate that one or both of the described situations may occur, such as A and / or B including (A and B) and (A or B).

[0010] Furthermore, in this document, the ranges expressed by the endpoints include all numbers contained within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0011] Furthermore, in this document, the expression "at least one" includes all numbers that are one or greater than one (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0012] As used in this article, "containing at least one of A, B, and C" means containing only element A, containing only element B, containing only element C, containing both A and B, containing both A and C, containing both B and C, and combinations containing all three.

[0013] As used in this article, "sol" may refer to a monomeric unit or cluster of salt, and not necessarily to a colloidal suspension.

[0014] As used in this article, “environmental” conditions refer to general indoor conditions, such as temperatures of 22°C to 25°C and pressures of approximately one atmosphere.

[0015] There are numerous applications where metals are bonded to organic resins. For example, organic-based structural adhesives can be used instead of mechanical fasteners or welding to hold metal layers together. When bonding metals to organic adhesives, the treatment of the metal surfaces prior to bonding is a critical factor for both the initial adhesion of the component and the long-term durability of the bond.

[0016] One such processing method utilizes sol-gel chemistry, in which an organometallic coating is positioned between a metallic substrate and an organic binder. U.S. Patent No. 5,939,197 (Blohowiak et al.) teaches an aqueous sol derived from organometallic salts and reactive silanes. The organometallic salts and reactive silanes form a sol-gel network.

[0017] The sol-gel coatings disclosed herein are derived from aqueous compositions comprising organometallic salts and aminosilanes. The term "sol-gel" (an abbreviation for solution-gel) refers to a series of reactions in which a soluble metal substance (typically a metal alkoxide or metal salt) hydrolyzes to form a metal hydroxide. The soluble metal substance typically contains organic ligands tailored to correspond to resins (e.g., organic adhesives) in the bonding structure. The metal hydroxide condenses in solution to form a hybrid organic / inorganic polymer.

[0018] The organometallic salts disclosed herein comprise both a metal and at least one organic moiety. Exemplary metals of the organometallic salts include zirconium, cerium, yttrium, lanthanum, or mixtures thereof. Exemplary organic moieties include aliphatic groups (optionally containing oxygen atoms), which include alkyl groups terminated with alkoxy or carboxylic acid having one, two, three, four, five, or even six carbon atoms. The aliphatic and alkyl groups can be straight-chain, branched, and / or cyclic. In some embodiments, the organometallic salt is a metal carboxylate, such as a metal acetate. Exemplary metal acetates include zirconium acetate, cerium acetate, lanthanum acetate hydrate, yttrium acetate trihydrate, or other hydrates. In some embodiments, the organometallic salt includes yttrium 2-ethylhexanoate, cerium acetylacetonate hydrate, cerium 2-ethylhexanoate, cerium stearate, lanthanum acetylacetonate, or mixtures thereof. In some embodiments, the organometallic salt is derived from a metal alkoxide compound of the formula Zr-(OR)4, wherein each R is independently selected from an aliphatic group. R can be straight-chain, branched, and / or cyclic. R may contain 2, 3, 4, or 5 carbon atoms. Such metal alkoxides include zirconium propoxide (iv), zirconium isopropoxide (iv), cerium propoxide (iv), cerium isopropoxide (iv), yttrium isopropoxide, yttrium 2-methoxyethanol, or mixtures thereof.

[0019] The compositions disclosed herein are water-based. In some embodiments, the organometal salt is a metal carboxylate that is stable in water. In other embodiments, the organometal salt (such as a metal alkoxide) is unstable in water. In those cases, the organometal salt is stabilized by adding an acid before adding water and / or an aminosilane to prevent the metal from undergoing rapid hydrolysis. For example, the rapidly reacting tetracoordinate zirconate center zirconium propoxide (IV) is highly sensitive to water. Therefore, zirconium propoxide (IV) is contacted with glacial acetic acid before contact with water, thereby converting the compound to zirconium acetate (IV), effectively altering the geometric and electronic properties of the zirconium component, which is now water-stable. Preferably, a minimal amount of acid should be used to stabilize the organometal salt. For example, the number of protons from the acid should be equal to the valence of the metal. For example, four equivalents of acetic acid should be used to stabilize zirconium propoxide (IV). An exemplary acid that can be used to stabilize the metal is acetic acid, preferably glacial acetic acid. Generally, the acid selected should be anhydrous and have a low boiling point, such that it evaporates during the drying and condensation of the coating.

[0020] In some embodiments, the aqueous composition further comprises a solvent. Exemplary solvents include alcohols, such as methanol, ethanol, 1-propanol, isopropanol, or other C4 to C6 fatty alcohols. In some embodiments, the amount of solvent present in the aqueous solution is less than 10 wt%, 5 wt%, 2 wt%, 1 wt%, or even 0.5 wt%.

[0021] The aqueous compositions disclosed herein contain a large amount of water. Typically, the aqueous solutions contain at least 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, or even 85 wt%, up to at most 90 wt%, 92 wt%, 95 wt%, 98 wt%, 99 wt%, 99.5 wt%, or even 100 wt% water.

[0022] The aqueous compositions disclosed herein also comprise aminosilanes. Aminosilanes are silicon-containing compounds comprising at least one amino group and an alkoxy group. In some embodiments, the aminosilane has the formula Si(OR) 1 (OR) 2 (OR) 3 )(X), where R 1 R 2 and R 3Independently selected from C1-C4 alkyl groups, and X is a monovalent C1-C12 group containing at least one amine. In some embodiments, X contains at least one, two, three, four, or even five aliphatic carbon atoms, which may be linear, branched, and / or cyclic in configuration. In some embodiments, X contains up to four, five, six, seven, eight, nine, ten, eleven, or even twelve aliphatic carbon atoms. X contains at least one amine group. In some embodiments, X contains more than one amine group. For example, two, three, or even four amine groups. Exemplary aminosilanes include: 3-aminopropyltriethoxysilane, n-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, m-aminophenyltrimethoxysilane, p-aminophenyltrimethoxysilane, 3-aminopropyltrimethoxysilane, n-phenylaminopropyltrimethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, or mixtures thereof.

[0023] In some embodiments, the resulting aqueous composition has a pH not exceeding 7.5, 7.3, 7.2, 7.0, 6.5, 6.2, 6.0, 5.5, 5.2, 5.0, 4.8, 4.5, 4.2, or even 4.0. Typically, the pH is higher than 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.7, 3.9, or even 4.0. In some embodiments, the resulting aqueous composition has a pH of at least 4.0 and at most 4.5. The pH can be determined using techniques known in the art, including calibrated pH meters or even pH test strips.

[0024] Typically, in aqueous compositions, the molar ratio of the metal of the organometallic salt to the silicon of the aminosilane is at least 0.1:1 or even 0.2:1, and in aqueous compositions, this molar ratio is at most 0.4:1 or even 0.5:1.

[0025] In some embodiments, the aqueous composition has a solids content of at least 1 vol%, 2 vol%, 3 vol%, or even 4 vol%. In some embodiments, the aqueous composition has a solids content of up to 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, or even 10 vol%.

[0026] The aqueous compositions disclosed herein (also referred to herein as sol-gel coating compositions) can be applied to the surface of a metal substrate. The gel coating can be used to improve the adhesion between the metal substrate and the organic resin. In some embodiments, the composite article of this disclosure sequentially comprises a metal substrate, the sol-gel coating disclosed herein, and an organic resin layer. Typically, the sol-gel coating is directly bonded to the metal substrate on one side (via a metal oxide) and directly bonded to the organic resin layer on the other side (via chemical bonds between the organic groups of the sol-gel layer and the organic resin).

[0027] Metal substrates include aluminum, aluminum alloys (e.g., 6061-O, 6061-T4, 6061-T6 and 6005A), titanium, titanium alloys (e.g., Grade 5), iron, steel (e.g. stainless steel), copper and alloys (such as Inconel alloys).

[0028] The organic resin layer is a layer compatible with amines. In some embodiments, the organic resin layer is an adhesive layer, such as a structural adhesive layer or a pressure-sensitive adhesive layer. Pressure-sensitive adhesives typically have initial tack and form a strong bond using only finger pressure. Pressure-sensitive adhesives are characterized by their shear and peel resistance, while structural adhesives are measured for their lap strength and are used for load-bearing joints. In some embodiments, the adhesive layer includes epoxy resins, polyurethanes, phenolic resins, acrylic resins, methacrylic resins, polyamides, bismaleimides, polyimides, or combinations or mixtures thereof. Such adhesives include those known in the art.

[0029] In some embodiments, the epoxy resin is an epoxy phenolic varnish resin, an epoxy cresol phenolic varnish resin, an epoxy phenolic varnish resin, an isocyanate-modified epoxy resin, an aliphatic epoxy resin, a bisphenol epoxy resin, or a mixture thereof.

[0030] In some embodiments, the resin is derived from isocyanate and hydroxyl groups, which react together to form a polyurethane resin. Exemplary compounds include polyols (such as glycols, glycerols, etc.) that react with polyfunctional isocyanates (such as triisocyanates).

[0031] In some embodiments, the adhesive layer comprises a phenolic resin derived from phenols and aldehydes, which provide phenolic varnishes or methyl phenolic resin polymers.

[0032] In some embodiments, the acrylic resin or methacrylic resin is derived from C1 to C2. 12(Meth)acrylate monomers, such as 2-methylbutyl acrylate, 2-ethylhexyl acrylate, butyl acrylate, isooctyl acrylate; optional polar monomers, such as acrylic acid or methacrylic acid; and crosslinking agents, such as polyfunctional (meth)acrylate compounds or triazine compounds.

[0033] In some embodiments, the adhesive layer comprises aliphatic polyamides (such as nylon PA 6 or PA 66) and / or polyphthalamide.

[0034] In some embodiments, the adhesive layer comprises polyimide or bismaleimide resin.

[0035] In some embodiments, the composite article of this disclosure is prepared by applying a sol-gel coating composition to a metal substrate. The surface of the metal substrate is typically cleaned, for example, using detergents, solvents, and / or sandblasting. See, for example, U.S. Patent No. 5,939,197, which is incorporated herein by reference. In some embodiments, the cleaned and sandblasted metal surface exhibits a “crack-free surface,” wherein a continuous water film is maintained on the surface for a period of 30 seconds after immersion rinsing in cleaning water. After cleaning, the sol-gel coating composition of this disclosure is applied to the surface of the metal substrate. The sol-gel coating composition can be applied using techniques known in the art, including dip coating, spraying, wetting, wiping, or brushing.

[0036] After application, the sol-gel coating composition is dried (or gelled) to form a sol-gel coating. In some embodiments, drying is performed under ambient conditions for a given amount of time (e.g., rapid drying or drying for 5 minutes to 2 hours). Alternatively or additionally, the sample is heated (e.g., from 140°C to 230°C) for a given amount of time (e.g., 15 minutes to 30 minutes). In some cases, sol-gel coatings processed at elevated temperatures exhibit stronger adhesive bonding to the metal substrate than those gelled at ambient temperatures.

[0037] In some embodiments, the thickness of the sol-gel layer is less than 10 micrometers, 8 micrometers, or even 5 micrometers. Typically, at least one molecular layer of the sol-gel coating should be present to ensure adequate coverage of the metal substrate and adhesion to the organic resin layer. The thickness of the resulting sol-gel coating can be controlled by the formulation and the duration of surface wetting.

[0038] After the surface gelation of the sol-gel coating on the metal substrate, an organic resin is applied to the exposed sol-gel coating using techniques known in the art. In some embodiments, the article is then further processed (e.g., using heat) to cure the organic resin layer, thereby forming a composite article.

[0039] The sol-gel coating disclosed herein can create a strong, durable adhesive bond between a metal substrate and an organic resin layer. In one embodiment, the sol-gel coating has an average overlap shear strength of at least 15 MPa, 18 MPa, 20 MPa, 22 MPa, 25 MPa, 28 MPa, 30 MPa, or even higher than 32 MPa.

[0040] Sol-gel coatings deposited on metal substrates are known to be non-uniform. It is believed that the reaction of organometallic salts with reactive silanes in aqueous compositions forms a gradient from the metal substrate through a hybrid inorganic / organic layer to the organic resin. For example, the organic portion of the sol-gel is predominantly located on the surface of the sol-gel coating, which can interact with and / or bond to the organic resin layer, while the metal atoms (e.g., zirconium oxide) and silicon are more oriented towards the metal substrate side of the sol-gel coating, where these metal atoms and silicon can interact with and complex with the metal substrate.

[0041] This application relates to the use of amino-based silanes in sol-gel coatings. U.S. Patent No. 5,939,197 teaches that when using aminosilanes, the sol operates optimally at a pH of 8 to 9, and therefore teaches the addition of a small amount of ammonium hydroxide. In this disclosure, it has been found that when aminosilanes are used in the preparation of these sol-gel coatings, operation under neutral or more preferably acidic conditions results in improved adhesion.

[0042] While not wishing to be theoretically limited, it is believed that for a well-integrated layer in sol-gel coatings, the zirconium (i.e., the metal from the organometallic salt) and silicon components should hydrolyze on similar timescales. To achieve this, the organometallic salt must be stabilized, as described above. Furthermore, when aminosilanes are added to water-stabilized organometallic salts, the aminosilanes are either pre-neutralized with an organic acid (such as acetic acid) before addition, or the resulting mixture is made acidic so as not to compromise the stability of the organometallic salt. Preferably, the aminosilane is pre-neutralized. The neutralization / acidification step is critical because it prevents the basic aminosilane from undergoing base-catalyzed condensation with the organometallic salt precursor upon contact with an aqueous organometallic solution. The neutralization step of the basic aminosilane transforms the reaction mechanism of the aminosilane into a hydrolysis mechanism, whose reaction timescale is more compatible with the hydrolysis of the organometallic salt. This is believed to provide better reactive integration between the basic aminosilane and the organometallic salt, resulting in a better-structured, higher-performance surface coating.

[0043] Example

[0044] Unless otherwise specified, all parts, percentages, ratios, etc., in the examples and the remainder of the description are by weight, and all reagents used in the examples are derived from or purchased from common chemical suppliers, such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or can be synthesized by conventional methods.

[0045] Use the following abbreviations: cm = centimeter, g = gram, L = liter, mL = milliliter, min = minute, MPa = megapascal, and wt = weight.

[0046]

[0047] Sample 1: Acid-stable aqueous zirconium sol

[0048] Add 5.3 g of glacial acetic acid to a 50 mL flask (flask 1). Add 11.7 g of tetrazirconium tetrapropoxide (as a mixture in 70% 1-propanol) to the flask while stirring. Then, dilute the contents of flask 1 with an equal volume of deionized water while stirring. Add 1135 mL of deionized water to a 2 L flask (flask 2). Add the entire contents of flask 1 to flask 2. Rinse flask 1 with 40 mL of deionized water and add the solution to flask 2.

[0049] Sample 2. Epoxy Resin Adhesive

[0050] The epoxy resin adhesive system is an anhydride-cured epoxy resin. The epoxy resin component consists of YX8000D and EPON58005 mixed in a 1:1 weight ratio. The anhydride curing agent component consists of Lindride 52D and DDSA mixed in a 1:1 weight ratio with 10wt% FXR1081. The epoxy resin component and the anhydride component are blended in a 1:1 weight ratio.

[0051] Sample preparation 3. Cleaning method for Al adhesive substrate 1

[0052] Two 4-inch × 7-inch (10cm × 18cm) Al substrates were cleaned by immersion in a detergent solution and scrubbing them with a cleaning pad (available under the trade name "3M SCOTCH-BRITE LIGHT CLEANSING PAD 7445" from 3M Co., St. Paul, MN), followed by rinsing with deionized water. After detergent cleaning, the Al substrates were then cleaned sequentially with the following solvents (acetone, ethanol, and isopropanol) by rinsing the surface with solvent and drying it with clean paper towels between each solvent rinse. The cleaned surface exhibited a "crack-free surface," meaning that a continuous water film remained on the surface for 30 seconds after immersion in the cleaning water. The cleaned surface of the Al substrates was then sandblasted along the bottom of the 7-inch side using abrasive (alumina #180) to create a sandblasting strip at least 1 inch (2.5cm) wide. The sandblasted surface was rinsed with isopropanol and wiped dry.

[0053] Sample preparation 4. Al adhesive substrate cleaning method 2

[0054] Two 4-inch × 7-inch (10cm × 18cm) substrates were cleaned sequentially using the following solvents (acetone, ethanol, and isopropanol) by rinsing the surface with solvent and drying it with clean paper towels between each solvent rinse. The cleaned surfaces exhibited a "crack-free surface." Then, along the bottom of the 7-inch side, the cleaned surface of the Al substrates was sandblasted with abrasive (alumina #180) to create a sandblasting strip at least 1 inch (2.5cm) wide. The sandblasted surfaces were rinsed with isopropanol and wiped, then allowed to dry.

[0055] Sample preparation 5. Cleaning method for Ti adhesive substrate

[0056] Ten 1-inch × 4-inch (2.5 cm × 10.2 cm) Ti substrates were cleaned sequentially using the following solvents (acetone, ethanol, and isopropanol) by rinsing the surface with solvent and drying it with clean paper towels between each solvent rinse. The cleaned surfaces exhibited a "crack-free surface." The cleaned surfaces of the Ti substrates were then sandblasted along the bottom of the 1-inch side using abrasive (alumina #180) to create sandblasting strips at least 1 inch (2.5 cm) wide. The sandblasted surfaces were rinsed with isopropanol and wiped, then allowed to dry.

[0057] Sample Preparation 6 OLS Sample Preparation

[0058] Apply the specified sol-gel solution to the sandblasted area of ​​the metal adhesive substrate prepared as in samples 3, 4, or 5. Keep the coated surface wet for 1 minute. Remove excess solution by draining it from the surface. Dry the wet surface at ambient temperature for 30 minutes, followed by heat treatment at 130°C for 30 minutes.

[0059] Two identical sol-gel treated metal-adhesive substrates were bonded in an overlapping configuration, with the sol-gel treated sides overlapping each other by 0.5 inches (1.3 cm). An epoxy resin adhesive from Preparation Sample 2 was placed between the overlapping portions of the two sol-gel treated metal substrates, having a 7 ± 1 mil (178 μm ± 25 μm) bond line thickness maintained using a minimum amount of 7 mil (178 μm) glass spacers. The epoxy resin adhesive was cured by heating the assembly at 130 °C for 1 hour. In the case of Al substrates, after the epoxy resin adhesive between the two Al substrates had cured, the composite was cut perpendicularly to the overlap into five 1-inch (2.6 cm) wide overlap shear (OLS) specimens for apparent shear strength testing.

[0060] Test method for apparent shear strength by overlap shear (OLS)

[0061] A 1-inch (2.6 cm) wide OLS specimen was tested by loading it onto a force sensor frame with a self-tightening tension clamp (available from MTS Systems Corp., Eden Prairie, MN). The specimen was placed in the tension clamp with its length aligned with the loading direction, and the 1-inch end of the specimen held within the clamp. The specimen was continuously loaded to failure at a crosshead speed of 1.3 mm / min. The shear stress was calculated as the failure load per unit bonded area, accurate to 0.01 inches (0.25 mm), from the measured width and length of the adhesive bond, and reported in MPa.

[0062] Methods for measuring pH

[0063] The pH values ​​of the various solutions reported below were determined using standard pH test strips. The pH was measured in 0.5 increments based on the color of the test strip relative to the colorimetric chart on the test strip packaging. The reported pH values ​​are based on matching the test strip color to the packaging. If the color falls between two colors, the range is reported.

[0064] Comparative Example 1 : The sol was prepared using (3-aminopropyl)trimethoxysilane, similar to the disclosure in Table 5 of U.S. Patent No. 5,939,197. 500 mL of deionized water was added to a 1000 mL flask (flask 1). Four drops of ammonium hydroxide were added to flask 1. The pH of the mixture in flask 1 was 7 to 8. 7.3 mL of glacial acetic acid was added to a 50 mL flask (flask 2). 14.3 mL of zirconium tetrapropoxide (as a mixture in 70 wt% 1-propanol) was added to flask 2 with stirring. 25 mL of (3-aminopropyl)trimethoxysilane was added to flask 1 with stirring. Flask 1 was capped and allowed to stand for 30 min. 300 mL of deionized water was added to another 500 mL flask (flask 3), and 200 mL of deionized water was added to a 200 mL flask (flask 4). The contents of flask 2 were diluted with an equal volume of deionized water with stirring. Add the entire contents of flask 2 to flask 3. Then, add 3 mL of ammonium hydroxide to flask 3. The solution in flask 3 is milky white and has a pH of approximately 5. Then, add the contents of flask 3 to the contents of flask 1 while stirring. Rinse flasks 2 and 3 with deionized water from flask 4, and add the solution to flask 1. Age the solution in flask 1 under ambient conditions for 4 hours while stirring.

[0065] The resulting sol-gel solution is hazy and heterogeneous due to the nucleation of colloidal heteroparticles from the sol precursor. The size of the colloidal heteroparticles was measured by dynamic light scattering, with an average value of approximately 1 μm. The pH of the solution was measured to be approximately 9.

[0066] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0067] Comparative Example 2 : The same preparation method as Comparative Example 1 was used, except that 32 mL of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was used instead of 3-aminopropyl)trimethoxysilane. Similar to Comparative Example 1, the solution in flask 3 was milky white and had a pH of approximately 5 before being added to flask 1.

[0068] The resulting sol-gel solution is hazy and heterogeneous due to the nucleation of colloidal heteroparticles from the sol precursor. The size of the colloidal heteroparticles was measured by dynamic light scattering, with an average value of approximately 1 μm. The pH of the solution was measured to be approximately 9.

[0069] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0070] Comparative Example 3.

[0071] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial. 0.213 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was added to the vial. The contents of the vial were vortexed to produce a hazy, heterogeneous solution. The solution was aged under ambient conditions for 4 hours.

[0072] The resulting sol-gel solution is hazy and heterogeneous due to the nucleation of colloidal heteroparticles from the sol precursor. The size of the colloidal heteroparticles was measured by dynamic light scattering, with an average value of approximately 1 μm. The pH of the solution was measured to be approximately 9.

[0073] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0074] Comparative Example 4.

[0075] A methanol solution containing approximately 1 wt% N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was used instead of the sol-gel solution, and tests were performed according to the methods used for preparing samples 3 and 6 and for testing the apparent shear strength using OLS. The average results are reported in Table 2.

[0076] Example 1

[0077] Solution 1: Neutralize 0.860 g of (3-aminopropyl)trimethoxysilane with 0.288 g of glacial acetic acid. Vortex the mixture to obtain a viscous, homogeneous liquid.

[0078] The sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial. 0.230 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 4 hours.

[0079] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0080] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0081] Example 2

[0082] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0083] The sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 4 hours.

[0084] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be approximately 7.

[0085] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0086] Example 3

[0087] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0088] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.057 g of glacial acetic acid and mixing. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 4 hours.

[0089] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0090] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0091] Example 4

[0092] Solution 1: 1.274 g of 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane was at least partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0093] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.057 g of glacial acetic acid and mixing. 0.312 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 4 hours.

[0094] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be approximately 7.

[0095] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0096] Example 5

[0097] Solution 1: 1.274 g of 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane was at least partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0098] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.115 g of glacial acetic acid and mixing. 0.312 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 4 hours.

[0099] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0100] The sol-gel solutions were tested according to the methods used for preparing samples 3 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0101] Example 6

[0102] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0103] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.057 g of glacial acetic acid and mixing. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0104] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0105] The sol-gel solutions were tested according to the methods used for preparing samples 4 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0106] Example 7

[0107] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0108] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.057 g of glacial acetic acid and mixing. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0109] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0110] The sol-gel solutions were tested according to the methods used for preparing samples 4 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0111] Example 8

[0112] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0113] A sol-gel coating solution was prepared by adding 9.820 g of preparation sample 1 to a 25 mL glass vial, followed by the addition of 0.057 g of glacial acetic acid and mixing. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0114] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0115] The sol-gel solutions were tested according to the methods used for preparing samples 5 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0116] Example 9

[0117] A sol-gel coating solution was prepared by adding 9.82 g of Preparation Sample 1 to a 25 mL glass vial, followed by the addition of 0.115 g of glacial acetic acid and mixing. 0.213 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was added to the glass vial. The contents of the vial were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0118] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0119] The sol-gel solutions were tested according to the methods used for preparing samples 4 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0120] Example 10

[0121] An aqueous zirconium acetate sol was prepared by adding 0.486 g of zirconium acetate to a 60 mL vial, followed by the addition of 48.6 g of water. An additional 0.576 g of glacial acetic acid was added to the vial. The mixture was vortexed. A sol-gel coating solution was prepared by adding 9.82 g of the prepared aqueous zirconium acetate solution to a 25 mL glass vial, followed by the addition of 0.213 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. The contents of the glass vials were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0122] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0123] The sol-gel solutions were tested according to the methods used for preparing samples 4 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0124] Example 11

[0125] Solution 1: 1.067 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 g of glacial acetic acid. The mixture was vortexed to obtain a viscous, homogeneous liquid.

[0126] An aqueous cerium acetate sol was prepared by adding 0.296 g of cerium acetate to a 60 mL vial, followed by 48.7 g of water. An additional 0.404 g of glacial acetic acid was added to the vial. The mixture was vortexed to dissolve the cerium acetate in the solution. A sol-gel coating solution was prepared by adding 9.88 g of the prepared aqueous cerium acetate solution to a 25 mL glass vial. 0.271 g of solution 1 was added to the glass vial. The contents of the glass vial were vortexed. The solution was aged under ambient conditions for 30 to 60 minutes.

[0127] The resulting sol-gel was clear and colorless. The pH of the solution was measured to be between 4 and 4.5.

[0128] The sol-gel solutions were tested according to the methods used for preparing samples 4 and 6 and for testing apparent shear strength using OLS. The average results are reported in Table 2.

[0129]

[0130] Foreseeable modifications and alterations to the invention will be apparent to those skilled in the art without departing from its scope and spirit. The invention should not be limited to the embodiments shown in this application for illustrative purposes. In the event of any conflict or contradiction between the disclosure in this written specification and any document incorporated herein by reference, the written specification shall prevail.

Claims

1. An aqueous composition comprising: a) Organometal salts, wherein the organometal salts include metal carboxylates, acid-stable metal alkoxides, or mixtures thereof; and b) Aminosilane, The aqueous composition has a pH of less than or equal to 7.

2. The aqueous composition according to claim 1, wherein the organometallic salt comprises zirconium, cerium, or mixtures thereof.

3. The aqueous composition according to any one of the preceding claims, wherein the metal carboxylate includes an acetate.

4. The aqueous composition according to claim 3, wherein the organometallic salt comprises zirconium acetate, cerium acetate, or a mixture thereof.

5. The aqueous composition according to any one of claims 1 to 2, wherein the acid-stabilized metal alkoxide is derived from zirconium propoxide (IV), zirconium isopropoxide (IV), cerium propoxide (IV), cerium isopropoxide (IV), or mixtures thereof.

6. The aqueous composition according to any one of the preceding claims, wherein the aminosilane has the formula Si(OR) 1 (OR) 2 (OR) 3 )(X), where R 1 R 2 and R 3 X is independently selected from C1-C4 alkyl groups, and X is a C1-C12 alkyl group containing at least one amine.

7. The aqueous composition according to any one of the preceding claims, wherein the aminosilane is selected from 3-aminopropyltriethoxysilane, n-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, m-aminophenyltrimethoxysilane, p-aminophenyltrimethoxysilane, 3-aminopropyltrimethoxysilane, n-phenylaminopropyltrimethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, or mixtures thereof.

8. The aqueous composition according to any one of the preceding claims, wherein the aqueous composition has a pH of less than or equal to 5.

9. The aqueous composition according to any one of the preceding claims, wherein the aqueous composition has a pH greater than or equal to 3.

10. The aqueous composition according to any one of the preceding claims, wherein the aqueous composition has a solid volume of at least 1% and at most 10%.

11. The aqueous composition according to any one of the preceding claims, wherein the molar ratio of the metal in the organometallic salt to the silicon in the aminosilane is at least 0.1:1 to at most 0.5:

1.

12. An article comprising: (a) Metal substrate; (b) Adhesive resin layer; and (c) A sol-gel layer located between the metal substrate and the adhesive resin layer, wherein the sol-gel layer is derived from an aqueous composition according to any one of the preceding claims.

13. The article of claim 12, wherein the metal substrate comprises aluminum, titanium, titanium alloy, aluminum alloy, steel, or a mixture thereof.

14. The article of any one of claims 12 to 13, wherein the adhesive resin layer comprises epoxy resin, polyurethane, phenolic resin, acrylic resin, polyamide, bismaleimide, polyimide, or combinations or mixtures thereof.

15. The article of claim 14, wherein the epoxy resin comprises epoxy phenolic varnish resin, epoxy cresol phenolic varnish resin, epoxy phenolic varnish resin, aliphatic epoxy resin, bisphenol epoxy resin, or mixtures thereof.

16. The article of any one of claims 12 to 15, wherein the thickness of the sol-gel layer is less than 10 micrometers.

17. The article according to any one of claims 12 to 16, wherein the article has an average shear strength of at least 15 MPa.

18. A kit comprising: (a) An aqueous solution comprising an organometallic sol, wherein the organometallic sol comprises an acid-stable metal alkoxide, a metal acetate, or a mixture thereof, and has a pH less than or equal to 7; as well as (b) Neutralized aminosilanes.

19. A method for preparing an aqueous sol-gel coating composition, the method comprising: (a) Providing an aqueous organometallic sol, wherein the organometallic sol comprises an acid-stabilized metal alkoxide, a metal acetate, or a mixture thereof; (b) Contacting the organometallic sol with an aminosilane in an aqueous solution, wherein the aqueous sol-gel coating composition has a pH of less than or equal to 7.

20. The method of claim 19, wherein glacial acetic acid is used to stabilize the acid-stabilized metal alkoxide.

21. The method according to any one of claims 19 to 20, wherein the pH of the aqueous sol-gel coating composition is adjusted using acetic acid.

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