Aqueous sol-GEL coating compositions, articles therefrom, and method of making such compositions

Abstract

Described herein is an aqueous composition and method of mating a sol-gel coating. The aqueous composition comprising (a) an organo metallic salt, wherein the organo metallic salt comprises an acid-stabilized metal alkoxide, a metal carboxylate, or mixtures thereof; and (b) an amino silane, wherein the aqueous composition has a pH of less than or equal 7. Such sol-gel coating compositions maybe used to adhere organic resins to metal substrates.

Description

AQUEOUS SOL-GEL COATING COMPOSITIONS, ARTICLES THEREFROM, AND METHOD OF MAKING SUCH COMPOSITIONSTECHNICAL FIELD

[0001] Disclosed herein is a method of making an aqueous sol-gel coating with amino silanes using acid- stabilized components and / or acidic conditions to generate surface coatings. Such coatings can promote good bonding between a metal substrate and a resinous material (such as organic adhesives).SUMMARY

[0002] There is a desire to identify aqueous based sol-gel compositions derived from amino silanes, which have good adhesion strength.

[0003] hi one aspect, an aqueous composition is described comprising:(a) an organo metallic salt, wherein the organo metallic salt comprises a metal acetate, an acid- stabilized alkoxy metal, or mixtures thereof; and(b) an amino silane, wherein the aqueous composition has a pH of less than or equal to 7.

[0004] In another aspect, an article is described comprising:(i) a metal substrate;(ii) an adhesive resin layer; and(iii) a sol-gel layer therebetween, wherein the sol-gel layer is derived from an aqueous composition comprising: (a) an organo metallic salt, wherein the organo metallic salt comprises a metal acetate, an acid-stabilized alkoxy metal, or mixturesthereof; and (b) an amino silane, wherein the aqueous composition has a pH of less than or equal to 7.

[0005] In yet another embodiment, a kit is described comprising:(a) an aqueous solution comprising an organo metallic salt, wherein the organo metallic salt comprises a metal acetate, an acid-stabilized alkoxy metal, or mixturesthereof; and(b) a neutralized amino silane, wherein the mixture of components (a) and (b) have a pH of less than or equal to 7.

[0006] hi still yet another embodiment, a method of making an aqueous sol-gel coating composition is described. The method comprising:(a) providing an organo metallic salt, wherein the organo metallic salt comprises a metal acetate, an acid- stabilized alkoxy metal, or mixturesthereof; and(b) contactingthe organo metallic salt with an amino silane, wherein the aqueous sol-gel coating composition has a pH of less han or equal to 7.

[0007] The above summary is not intended to describe each embodiment. The details of one or more embodiments ofthe invention are also set forth in the description below. Other features, objects, and advantages will be apparent fromthe description and from the claims.DETAILED DESCRIPTION

[0008] As used herein, the term “a”, “an”, and “the” are used interchangeably and mean one or more.

[0009] The term “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes, (A and B) and (A or B).

[0010] Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0011] Also herein, recitation of “at least one” includes all numbers of one and greater (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 herein, “comprises at least one of’ A, B, and C refers to element A by itself, element B by itself, element C by itself, A and B, A and C, B and C, and a combination of all three.

[0013] As used herein, “sol” can refer to a monomeric unit, or clusters of the salt, and does not necessarily refer to a colloidal suspension.

[0014] As used herein, “ambient” conditions refer to general room conditions such as a temperature between 22 to 25°C and a pressure such as about 1 atmosphere.

[0015] There are numerous applications where metal is bonded to an organic resin. For example, metal layers may be held together with an organic-based structural adhesive instead of using mechanical fasteners or welding. When bonding metal to an organic adhesive, the treatment of the metal surface prior to bonding is a key factor for both the initial adhesion of the parts and the bond’s long-term durability.

[0016] One such treatment method utilizes sol-gel chemistry, where an organo-metallic based coating is positioned between the metal substrate and the organic adhesive. U.S. Pat. No. 5,939,197 (Blohowiak et al.) teaches a water-based sol derived from an organo metallic salt and a reactive silane. The organo metallic salt and the reactive silane form a sol-gel network.

[0017] The sol-gel coatings disclosed herein are derived from an aqueous composition comprising an organo metallic salt and an amino silane. The term "sol-gel," a contraction of solution-gelation, refers to a series of reactions where a soluble metal species (typically a metal alkoxide or metal salt) hydrolyzes to form a metal hydroxide. The soluble metal species usually contain organic ligands tailored to correspond with the resin (e.g., organic adhesive) in the bonded structure. The metal hydroxides condense in solution to form a hybrid organic / inorganic polymer.

[0018] The organo metallic salt of the present disclosure comprises both a metal and at least one organic moiety. Exemplary metals of the organo metallic salt include zirconium, cerium, yttrium, lanthanum, or matures thereof. Exemplary organic moieties include aliphatic groups, optionally comprising oxygen atoms, including alkoxy or carboxylic acid terminated alkyl groups having 1 , 2, 3, 4, 5, or even 6 carbon atoms. The aliphatic and alkyl groups may be linear, branched, and / or cyclic. In some embodiments, the organo metallic 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 organo metallic salt includes yttrium 2-ethylhexanoate, cerium acetylacetonate hydrate, cerium 2-ethylhexanolate, cerium stearate, lanthanum acetylacetonate, or mixtures thereof. Insome embodiments, the organo metallic salt is derived from a metal alkoxide compound of the formula Zr-(OR)4, where each R is independently selected from an aliphatic group. R can be linear, branched, and / or cyclic. R can comprise 2, 3, 4, or 5 carbon atoms. Such metal alkoxides include zirconium(iv) propoxide, zirconium(iv) isopropoxide, cerium(iv) propoxide, cerium(iv) isopropoxide, yttrium isopropoxide, yttrium 2-methoxyethoxide, or mixtures thereof.

[0019] The compositions of the present disclosure are aqueous based. In some embodiments, the organo metallic salt is a metal carboxylate, which is stable in water. In other embodiments, organo metallic salts, such as metal alkoxides, are not stable in water. In those instances, the organo metallic salt is treated by the addition of acid to stabilize the organo metallic salt before the addition of the water and / or amino silane to prevent the metal from undergoing rapid hydrolysis. For example, the fast reacting four- coordinate zirconate center zirconium(IV) propoxide is highly susceptible to water. Thus, prior to contacting with water, the zirconium(IV) propoxide is contacted with glacial acetic acid, turning the compound into zirconium(IV) acetate, effectively changed the geometric and electronic nature of the zirconium component, which is now water stable. Preferably, the minimum amount of acid to stabilize the organo metallic salt should be used. For example, the number of protons from the acid should equal the valency of the metal. For instance, zirconium(IV) propoxide should be stabilized with four equivalents of acetic acid. An exemplary acid that may be used for stabilizing the metal is acetic acid, preferably glacial acetic acid. Typically, the acid selected should be one that is anhydrous and has a low boiling point such that it evaporates during drying and condensation of the coating.

[0020] hi 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 aliphatic alcohols. In some embodiments, the amount of solvent present in the aqueous solution is less than 10, 5, 2, 1 , or even 0.5 wt (weight)%.

[0021] The aqueous compositions of the present disclosure comprise a majority of water. Typically, the aqueous solution comprises at least 50, 55, 60, 65, 70, 75, 80, or even 85% to at most 90, 92, 95, 98, 99, 99.5 or even 100% by weight of water.

[0022] The aqueous composition of the present disclosure further comprises an amino silane. The amino silane is a silicon-containing compound comprising at least one amino group and an alkoxy group. In some embodiments, the amino silane is of the formula Si(OR1XOR2)(OR3)(X), wherein R1, R2, and R1are independently selected from a C1-C4 alkyl and X is monovalent C1-C12 group comprising at least 1 amine. In some embodiments, X, comprises at least 1, 2, 3, 4, or even 5 aliphatic carbon atoms, which may be linear, branched, and / or cyclic in configuration. In some embodiments, X comprises at most 4, 5, 6, 7, 8, 9, 10, 11, or even 12 aliphatic carbon atoms. X comprises at least 1 amine group. In some embodiments, X comprises more than 1 amine group. For example, 2, 3, or even 4 amine groups. Exemplary amino silanes include: 3-aminopropyltriethoxysilane, n-(2-aminoethyl)-3- aminopropyltrimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, m- aminophenyltrimethoxysilane, p- aminophenyltrimethoxysilane, 3-aminopropyltrimethoxysilane, n-phenylaminopropylttimethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propylirimeihoxysilane, or mixtures thereof.

[0023] In some embodiments, the pH of the resulting aqueous composition is no more than 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 above 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.7, 3.9, or even 4.0. hi some embodiments, the pH of the resulting aqueous composition is at least 4.0 to at most 4.5. The pH can be determined using techniques known in the art, including a calibrated pH meter or even pH test strips.

[0024] Typically, the molar ratio of the metal of the organo metallic salt versus the silicon of the amino silane in the aqueous composition is at a ratio of at least 0.1:1 or even 0.2:1 and at most 0.4:1 or even 0.5: 1 in the aqueous composition.

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

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

[0027] Metal substrates include aluminum, aluminum alloy (e.g., 6061-0, 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 alloy.

[0028] The organic resin layers are layers compatible with amine binding, In some embodiments, the organic resin layer is an adhesive layer such as a structure adhesive layer or a pressure sensitive adhesive layer. Pressure sensitive adhesives typically have initial tack and form a strong bond only with finger pressure. Pressure sensitive adhesives are characterized by their shear and peel resistance, whereas a structural adhesive is measured for its lap strength and is used in load-bearing joints. In some embodiments, the adhesive layer comprises an epoxy, a urethane, a phenolic, an acrylic, a methacrylic, a polyamide, a bismaleimide, a polyimide, or combinations or mixtures thereof. Such adhesives include those known in the art.

[0029] In some embodiments, the epoxy is an epoxy novolac resin, an epoxy cresol novolac resin, an epoxy phenol novolac resin, an isocyanate-modified epoxy resin, an aliphatic epoxy resin, a bisphenol epoxy resin, or mixtures thereof.

[0030] In some embodiments, the resin is derived from isocyanate and hydroxide groups which are reacted together to form a urethane resin. Exemplary compounds include polyols (such as diols, glycerol, etc.) reacted with multifunctional isocyanates (such as a triisocyanate).

[0031] In some embodiments, the adhesive layer comprises a phenolic resin derived from phenols and aldehydes, which provide a novolac or resole polymer.

[0032] In some embodiments, an acrylic or methacrylic resin is derived from a C1to C12(meth)acrylate ester monomer, such as 2-methyl butyl acrylate, 2-ethyl hexyl acrylate, butyl acrylate, iso-octyl acrylate; optional polar monomers, such as acrylic acid or methacrylic acid; and a crosslinking agent, such as a multifunctional (meth)acrylate compound or a triazine compound.

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

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

[0035] In some embodiments, the composite articles of the present disclosure are made by applying the sol-gel coating composition to a metal substrate. The surface of the metal substrate is typically cleaned, for example using detergents, solvents, and / or grit blasting. See, for example, U.S. Pat. No. 5,939,197, herein incorporated by reference. In some embodiments, the cleaned and grit blasted metal surface demonstrates a “water-break-free surface” where the surface maintains a continuous water film for a period of 30 seconds after immersion rinse in clean water. Following cleaning, the sol-gel coating composition of the present disclosure is applied to the metal substrate's surface. The sol-gel coating composition may be applied using techniques known in the art including dip coating, spraying, drenching, wiping, or brushing.

[0036] Following application, the sol-gel coating composition is allowed to dry (or gel) to form the sol- gel coating layer. In some embodiments, drying is performed at ambient conditions for a given amount of time (for example, flash dried or dried from 5 minutes to 2 hours). Alternatively, or additionally, the sample is heated (for example, from 140 to 230 °C) for a given amount of time (for example, 15 minutes to 30 minutes). In some instances, sol-gel coatings processed at elevated temperature give a stronger adhesive bond to the metal substrate than those gelled at ambient temperature.

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

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

[0039] The sol-gel coatings of the present disclosure can produce strong, durable adhesive bonds 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, 18, 20, 22, 25, 28, 30, or even above 32 MPa (mega Pascals).

[0040] It is known that the sol-gel coating layer deposited on a metal substrate is not homogeneous. It is believed that reaction of the organometallic salt with the reactive silane in the aqueous composition formsa gradient from the metal substrate through a hybrid inorganic / organic layer to the organic resin. For example, the organic type moieties of the sol-gel are located primarily on the surface of the sol-gel coating available for interacting and / or bonding to the organic resin layer while the metal atoms (e.g., zirconia) and silicon are located more toward the metal substrate side of the sol-gel coating layer where they can interact and complex with the metal substrate.

[0041] The present application is directed toward using amino-based silanes in the sol-gel coatings. U.S. Pat. No. 5,939,197 teaches that when using amino silanes, the sols operate best at a pH of 8-9 and thus, it is taught to add small amounts of ammonium hydroxide. In the present disclosure, it has been discovered that when using amino silanes in making these sol-gel coatings, operating in neutral or, more preferably, acidic conditions results in improved bonding.

[0042] Although not wanting to be limited by theory, it is believed that to get a good integrated layer in the sol-gel coating, the zirconium (i.e., metal from the organo metallic salt) and the silicon components should hydrolyze on a similar time scale. To achieve this, the organo metallic salt must be stabilized, as described above. Further, when the amino silane is added to the organo metallic salt, which is water stable, either the amino silane is pre-neutralized with an organic acid (such as acetic acid) prior to the addition or the resulting mixture is made acidic, such that the stabilization of the organo metallic salt is not undone. Preferably, the amino silane is pre-neutralized. The neutralization / acidification step is critical as it prevents the base catalyzed condensation of the basic amino silane with the organometallic salt precursor when coming in contact with organo metallic aqueous solution. The neutralization step of the basic amino silane shifts the reaction mechanism of the amino silane to a hydrolysis reaction mechanism with a reaction time scale that is more compatible with hydrolysis of the organometallic salt. This is believed to offer better reactive integration between the basic amino silane and organo metallic salt, yielding better structured, higher performing surface coatings.EXAMPLES

[0043] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0044] The following abbreviations are used: cm = centimeter, g = gram, L = liter, mL = millileters, min = minute, MPa = mega Pascals, and wt = weight.Table 1. Materials List

[0045] Preparatory Sample 1: Acid stabilized aqueous zirconium sol

[0046] To a 50 mL flask (Flask 1), 5.3 grams of glacial acetic acid was added. To the flask, 11.7 grams of zirconium tetrapropoxide as a 70% mixture in 1 -propanol was added with stirring. Then, the contents of Flask 1 were diluted with an equivalent volume of deionized water with stirring. To a 2 L flask (Flask 2), 1135 mL of deionized water was added. The entire content of Flask 1 was added to Flask 2. Flask 1 was rinsed with 40 mL of deionized water and added to Flask 2.

[0047] Preparatory Sample 2. Epoxy adhesive

[0048] The epoxy adhesive system was an anhydride cured epoxy. The epoxy component was composed of YX8000D and EPON58005 mixed in a 1 to 1 wt ratio. The anhydride curative component was composed of Lindride 52D and DDSA mixed in a 1 to 1 wt ratio with 10 wt% FXR1081. The epoxy and anhydride components were mixed in a 1 to 1 wt blend ratio.

[0049] Preparatory Sample 3. Al adherend substrate cleaning method 1

[0050] Two 4 inch x 7 inch (10 cm x 18 cm) Al substrates were cleaned by immersion in a detergent water solution and scrubbed with a cleaning pad (available under the trade designation “3M SCOTCH- BRITE LIGHT CLEANSING PAD 7445” from 3M Co., St. Paul, MN) and rinsed with deionized water. Following detergent cleaning, the Al substrates were then cleaned with the following solvents in order,acetone, ethanol, and isopropanol by rinsing the surface with the solvent and drying between each solvent rinse with a clean paper towel. The cleaned surfaces demonstrated a “water-break-free surface” where the surface maintained a continuous water film for a period of 30 seconds after having been immersion rinsed in clean water. Then, along the bottom of the 7 inch side, the cleaned surface of the Al substrate was blasted with grit (aluminum oxide #180) forming at least a 1 inch (2.5 cm)-wide blasted strip. The grit blasted surface was rinsed and wiped with isopropanol and allowed to dry.

[0051] Preparatory Sample 4. Al adherend substrate cleaning method 2

[0052] Two 4 inch x 7 inch (10 cm x 18 cm) Al substrates were cleaned with the following solvents in order, acetone, ethanol, and isopropanol by rinsing the surface with the solvent and drying between each solvent rinse with a clean paper towel. The cleaned surfaces demonstrated a “water-break-free surface". Then, along the bottom of the 7 inch side, the cleaned surface of the Al substrate was blasted with grit (aluminum oxide #180) forming at least a 1 inch (2.5 cm)-wide blasted strip. The grit blasted surface was rinsed and wiped with isopropanol and allowed to dry.

[0053] Preparatory Sample 5. Ti adherend substrate cleaning method

[0054] Ten 1 inch x 4 inch (2.5 cm x 10.2 cm) Ti substrates were cleaned with the following solvents in order, acetone, ethanol, and isopropanol by rinsing the surface with the solvent and drying between each solvent rinse with a clean paper towel. The cleaned surfaces demonstrated a “water-break-free surface”. Then, along the bottom of the 1 inch side, the cleaned surface of the Ti substrate was blasted with grit (aluminum oxide #180) forming at least a 1 inch (2.5 cm)-wide blasted strip. The grit blasted surface was rinsed and wiped with isopropanol and allowed to dry.

[0055] Preparatory Sample 6 OLS sample preparation

[0056] The designated sol-gel solution was brushed to the grit blasted area of the metal adherend substrates prepared as in Preparatory Samples 3, 4, or 5. The coated surface was kept wet for 1 min The excess solution was removed by allowing the excess to drain from the surface. The wet surface was dried at ambient temperature for 30 min and then thermally treated at 130°C for 30 min.

[0057] Two of the same sol-gel treated metal adherend substrates were bonded in an overlap configuration with the sol-gel treated sides facing each other with a 0.5 inch (1.3 cm) overlap. The epoxy adhesive from Preparatory Sample 2 was placed between the overlap of the two sol-gel treated metal substrates, having a 7 + / - 1 mil (178 pm + / - 25 pm) bond line thickness maintained with a minimal amount of 7 mil (178 pm) glass spacer beads. The epoxy adhesive was cured by heating the assembly for 1 hour at 130°C. In the case of the Al substrate, after curing of the epoxy adhesive between the two Al substrates, the composite was cut perpendicular to the overlap into five 1 inch (2.6 cm)-wide overlap shear (OLS) specimens for apparent shear strength testing.

[0058] Test method for overlap shear (OLS) apparent shear strength

[0059] 1 inch (2.6 cm)-wide OLS specimens were tested by loading on a load cell frame (available from MTS Systems Corp., Eden Prairie, MN) with self-tightening tensile grips. The specimen was place in the tensile grips so that the long direction of the test specimen coincided with the load direction and 1 inch of the specimen ends were held within the grips. The specimen was continuously loaded to failuremaintaining a crosshead speed of 1.3 mm / min. The shear stress was calculated as the failure load per unit of bond area calculated from the measured width and length of the adhesive bond to the nearest 0.01 inches (0.25 mm) and reported in MPa units.

[0060] Method of measuring pH

[0061] The pH values reported below for the various solutions were determined using standard pH test strips. The test strips measured pH in 0.5 intervals based on color relative to a color chart on test strip package. The pH values reported were based on matching the color of the test strip to the padrage. If a color fell between two colors, the range was reported.

[0062] Comparative Example 1:

[0063] A sol was prepared similar to the disclosure of Table 5 in U.S. Pat. No. 5,939,197 using 3- aminopropyl)trimethoxysilane. To a 1000 ml flask (Flask 1), 500 mL of deionized water was added. 4 drops of ammonium hydroxide was added to Flask 1. The pH of the mixture in Flask 1 was between 7 to 8. To a 50 ml flask (Flask 2), 7.3 mL of glacial acetic add was added. 14.3 mL of zirconium tetrapropoxide as a 70% wt mixture in 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 covered and allowed to dwell for 30 min. To another 500 mL flask (Flask 3), 300 mL of deionized water was added and 200 mL of deionized water was added to a 200 mL flask (Flask 4). The contents of Flask 2 were diluted with an equivalent volume of deionized water with stirring. The entire contents of Flask 2 was added to Flask 3. Then, 3 mL of ammonium hydroxide was added to Flask 3. The solution in Flask 3 was milky white and had a pH of approximately 5. Then, the contents of Flask 3 were added to the contents of Flask 1 with stirring. Flask 2 and Flask 3 were rinsed with deionized water from Flask 4 and added to Flask 1. The solution in Flask 1 was aged at ambient conditions for 4 hours with stirring.

[0064] The resulting sol-gel solution was hazy and heterogenous due to the nucleation of colloidal heteroparticles from the sol precursors. The size of colloidal heteroparticles was measured by dynamic light scattering to be an average of about 1 pm. The pH of the solution was measured to be approximately 9.

[0065] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0066] Comparative Example 2:

[0067] The same preparation as in Comparative Example 1 was used, except that 32 mL of N-(2- Aminoethyl)-3-aminopropyltrimethoxysilane was used in place 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 it was added to Flask 1.

[0068] The resulting sol-gel solution was hazy and heterogenous due to the nucleation of colloidal heteroparticles from the sol precursors. The size of colloidal heteroparticles was measured by dynamic light scattering to be an average of about 1 pm. The pH of the solution was measured as approximately 9.

[0069] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0070] Comparative Example 3.

[0071] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial. 0.213 grams of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was added to the glass vial. The contents of the glass vial were vortex mixed to yield a hazy heterogeneous solution. The solution was aged at ambient conditions for 4 hours.

[0072] The resulting sol-gel solution was hazy and heterogenous due to the nucleation of colloidal heteroparticles from the sol precursors. The size of colloidal heteroparticles was measured by dynamic light scattering to be an average of about 1 pm. The pH of the solution was measured as approximately 9.

[0073] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0074] Comparative Example 4.

[0075] A solution comprising about 1 wt% N-(2-antinoethyl)-3-aminopropyltrimethoxysilane in methanol was used in place of the sol-gel solution and was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0076] Example 1

[0077] Solution 1 : 0.860 grams of (3-aminopropyl)trimethoxysilane was neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0078] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial. 0.230 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 4 hours.

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

[0080] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0081] Example 2

[0082] Solution 1: 1.067 grams ofN-(2-Aminoethyl)-3-aminopropyltrimeflioxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0083] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 4 hours.

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

[0085] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0086] Example 3

[0087] Solution 1: 1.067 grams of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mature was vortex mixed to yield a viscous homogeneous liquid.

[0088] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.057 grams of glacial acetic acid, and mixed. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 4 hours.

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

[0090] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0091] Example 4

[0092] Solution 1: 1.274 grams of 3-[2-(2-aminoethylamino)ethylamino] propyhrimethoxysilane was at least partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0093] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.057 grams of glacial acetic acid, and mixed. 0.312 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 4 hours.

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

[0095] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0096] Example 5

[0097] Solution 1: 1.274 grams of 3-[2-(2-Aminoethylamino)ethylamino] propyltrimethoxysilane was at least partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0098] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.115 grams of glacial acetic acid, and mixed. 0.312 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 4 hours.

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

[0100] The sol-gel solution was tested following the Preparatory Samples 3 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0101] Example 6

[0102] Solution 1: 1.067 grams of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0103] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.057 grams of glacial acetic acid, and mixed. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 30-60 minutes.

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

[0105] The sol-gel solution was tested following the Preparatory Samples 4 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0106] Example 7

[0107] Solution 1: 1.067 grams ofN-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0108] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.057 grams of glacial acetic acid, and mixed. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 30-60 minutes.

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

[0110] The sol-gel solution was tested following the Preparatory Samples 4 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0111] Example 8

[0112] Solution 1: 1.067 grams of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.

[0113] A sol-gel coating solution was prepared by adding 9.820 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.057 grams of glacial acetic acid, and mixed. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 30-60 minutes.

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

[0115] The sol-gel solution was tested following the Preparatory Samples 5 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0116] Example 9

[0117] A sol-gel coating solution was prepared by adding 9.82 grams of Preparatory Sample 1 to a 25 mL glass vial, followed by an additional 0.115 grams of glacial acetic acid, and mixed. 0.213 grams of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 30-60 minutes.

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

[0119] The sol-gel solution was tested following the Preparatory Samples 4 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0120] Example 10

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

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

[0123] The sol-gel solution was tested following the Preparatory Samples 4 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.

[0124] Example 11Solution 1: 1.067 grams of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was partially neutralized with 0.288 grams of glacial acetic acid. This mixture was vortex mixed to yield a viscous homogeneous liquid.An aqueous cerium acetate sol is prepared by adding 0.296 grams of cerium acetate to a 60 mL vial followed by 48.7 grams of water. 0.404 grams of additional glacial acetic acid is added to the vial. This mixture is vortex mixed to dissolve the cerium acetate into solution. A sol-gel coating solution is prepared by adding 9.88 grams of the prepared cerium acetate aqueous solution to a 25 mL glass vial. 0.271 grams of Solution 1 was added to the glass vial. The contents of the glass vial were vortex mixed. The solution was aged at ambient conditions for 30-60 minutes.

[0125] The resulting sol-gel solution was clear and colorless. The pH of the solution was measured to be between 4-4.5.

[0126] The sol-gel solution was tested following the Preparatory Samples 4 and 6 and Test method for OLS apparent shear strength. The average result is reported in Table 2.*Ml

[0127] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned or incorporated by reference herein, this specification as written will prevail.

Claims

What is claimed is:

1. An aqueous composition comprising: a)an organo metallic salt wherein the organo metallic salt comprises a metal carboxylate, an acid-stabilized metal alkoxide, or mixtures thereof; and b) an amino silane, wherein the aqueous composition has a pH of less than or equal to 7.2.The aqueous composition of claim 1, wherein the organo metallic salt comprises zirconium, cerium, or mixtures thereof.

3. The aqueous composition of any one of the previous claims, wherein the metal carboxylate comprises an acetate.

4. The aqueous composition of claim 3, wherein the organo metallic salt comprises zirconium acetate, cerium acetate, or mixtures thereof.

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

6. The aqueous composition of any one of the previous claims, wherein the amino silane is of the formula Si(OR1)(OR2XOR3)(X), wherein R1, R2, and R3are independently selected from a C1-C4 alkyl and X is C1-C12 alkyl group comprising at least 1 amine.

7. The aqueous composition of any one of the previous claims, wherein the amino silane is selected from 3-aminopropyltriethoxysilane, n-(2-ammoethyl)-3-aminopropyltrimethoxysilane, 3- (m-aminophenoxy)propyltrimethoxysilane,m-aminophenyltrimethoxysilane, p- aminophenyhrimethoxysilane, 3-aminopropyltrimethoxysilane, n- phenylaminopropyltrimethoxysilane, 3-[2-(2- aminoethylamino)ethylamino]propyltrimethoxysilane, or mixtures thereof.

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

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

10. The aqueous composition of any one of the previous claims, wherein the aqueous composition has a solids volume of at least 1% and at most 10%.

11. The aqueous composition of any one of the previous claims, wherein the molar ratio of the metal in the organo metallic salt versus the silicon in the amino silane is at least 0.1:1 to at most 0.5:1.

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

13. The article according to claim 12, wherein the metal substrate comprises aluminum, titanium, titanium alloy, aluminum alloy, steel, or mixtures thereof.

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

15. The article according to claim 14, wherein the epoxy comprises an epoxy novolac resin, an epoxy cresol novolac resin, an epoxy phenol novolac resin, an aliphatic epoxy resin, a bisphenol epoxy resin, or mixtures thereof.

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

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

18. A kit comprising:(a) an aqueous solution comprising an organo metallic sol, wherein the organo metallic sol comprises an acid-stabilized alkoxy metal, a metal acetate, or mixtures thereof and having a pH of less than or equal to 7; and(b) a neutralized amino silane.

19. A method of making an aqueous sol-gel coaling composition, the method comprising:(a) providing an organo metallic aqueous sol, wherein the organo metallic sol comprises an acid-stabilized alkoxy metal, a metal acetate, or mixtures thereof;(b) contacting in an aqueous solution, the organo metallic sol with an amino silane, wherein the aqueous sol-gel coating composition has a pH of less than or equal to 7.

20. The method of claim 19, wherein the acid-stabilized alkoxyl metal is stabilized with glacial acetic acid.

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

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