Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-01-22
2002-11-05
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S591000, C524S594000, C524S595000, C524S596000, C524S841000, C427S372200, C427S385500, C427S388100, C427S388200, C427S388300, C427S388400, C428S460000
Reexamination Certificate
active
06476119
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous primer or coating, particularly a primer for use in polymeric material-to-metal adhesive bonding and a coating for protecting metallic surfaces.
Primers are often used as an undercoat in combination with a covercoat adhesive in order to achieve superior bonding between two substrates made from different materials. One particular application for such primers is in bonding metal surfaces to elastomeric surfaces. Elastomer-to-metal bonding is subjected to severe environmental conditions in many industrial and automotive assemblies. For example, many engine mounting assemblies that employ elastomer-to-metal bonding contain fluids in order to assist in damping of vibration of the engine. These fluid-filled engine mounting devices are being exposed to increasingly high temperatures such that the elastomer-to-metal adhesive bonds within the mounts are being exposed to very high temperature fluid environments. Many elastomer-to-metal assemblies, particularly those utilized in automobile applications, are routinely exposed to materials that contain corrosive salts or other corrosive materials that may act to degrade the elastomer-to-metal adhesive bond.
In light of the increasing regulations regarding volatile organic compounds (VOC), the use of traditional solvent-borne adhesives is becoming more problematic. Consequently, there is significant ongoing work to develop water-borne replacements. For example, U.S. Pat. No. 4,167,500 describes an aqueous adhesive composition that includes a water-dispersible novolak resin, a methylene donor and water. Aqueous or water-borne primers are known and described in U.S. Pat. Nos. 5,200,455 and 5,162,156, but they have various shortcomings compared to solvent-borne primers. For example, it is desirable to improve the environmental resistance performance of aqueous elastomer-to-metal adhesion primers that include polyvinyl alcohol-stabilized phenolic resin dispersions (see U.S. Pat. No. 5,200,455) when used with certain important adhesive covercoats. Elastomer-to-metal primers that include phenolic resins derived from water soluble phenolic precursors are also known (see U.S. Pat. No. 5,162,156) but these suffer from drawbacks that prevent their use to form robust, environmentally resistant films. Before being thermoset, films formed from water soluble phenolic resins tend to re-solvate when exposed to water. The source of the water can be an aqueous covercoat applied to the film. Application of the aqueous covercoat essentially washes away the film formed from the water soluble phenolic resin. In addition, such films exhibit very limited resistance to corrosive fluids.
Another problem associated with the bonding of elastomer to metal relates to pre-heating or pre-baking of the dried adhesive prior to bonding. The metal substrate typically is coated with the adhesive, the adhesive is dried and then the adhesive-coated metal substrate is placed in a mold. Elastomer then is introduced into the mold and bonded to the metal substrate during vulcanization of the elastomer. The bonded part is removed from the mold and the next metal substrate is placed in the mold. When this subsequent metal substrate is placed in the mold it is subjected to the heat retained in the mold from the previous molding operation. The dried adhesive must be able to withstand this retained heat (referred to herein as “pre-heating”) prior to bonding.
Consequently, there exists a continuing need for an aqueous primer that provides robust adhesive bonding in hot, corrosive environments, has an affinity for a broad range of covercoats, and forms a flexible film that is resistant to pre-heating conditions and exhibits superior shelf-life stability and resistance to resolvation. It would be especially advantageous if such a primer could also be used as a coating for protecting a metallic surface.
At present, there are two commonly-used metal coating methods electrodeposition and autodeposition—that are typically used subsequent to, or as a substitute for, phosphatizing of the metallic surface. Electrodeposition (frequently referred to as “E-coat”) involves immersing a metal surface in a composition then applying a voltage through the composition so that a coating will deposit on the metal surface. An autodeposition coating is commercially available from Henkel and its subsidiary Parker Amchem under the trademark AUTOPHORETIC®.
According to the patents and commercial literature, immersion of a metallic surface in an autodeposition composition produces what is said to be a self-limiting protective coating on a metal substrate. Autodeposition compositions are known to generally include water, resin solids dispersed in the aqueous medium, and an activator. For example, the aqueous autodeposition solution in one commercial embodiment contains 3-5 percent solids of a latex (polyvinylidene chloride or acrylic) and carbon black, ferric fluoride and a low concentration of hydrofluoric acid to provide a solution pH of 2.5-3.0. According to the commercialized multi-stage process, a clean degreased steel panel is immersed in an autodeposition solution for one to two minutes, the resulting “green” film is rinsed in a reaction rinse solution and then dried at 100° C. The reactive rinse solution can include a diphosphonic acid.
The dispersed resin solid typically is derived from ethylenically unsaturated monomers. Polyvinylidene chloride is the preferred resin. Polyethylene, polyacrylic, styrene-butadiene and epoxy resins are mentioned as possible resin particles that are dispersed or emulsified in water (see U.S. Pat. Nos. 4,414,350; 4,994,521; 5,427,863; 5,061,523; and 5,500,460). According to U.S. Pat. No. 5,486,414, AUTOPHORETIC® 800 Series compositions are based on polyvinylidene chloride and AUTOPHORETIC® 700 Series compositions are based on acrylic resins.
The activator is an ingredient or ingredients that convert the composition into one which will form a self-limiting resinous coating on a metallic surface. The activating system generally comprises an acidic oxidizing system, for example: hydrogen peroxide and HF; HNO
3
; a ferric-containing compound and HF; and other soluble metal-containing compounds, for example, silver fluoride, ferrous oxide, cupric sulfate, cobaltous nitrate, silver acetate, ferrous phosphate, chromium fluoride, cadmium flouride, stannous flouride, lead dioxide, and silver nitrate in an amount of 0.025 to 50 g/l and an acid, which can be used alone or in combination with hydrofluoric acid, and including, for example, sulfuric, hydrochloric, nitric and phosphoric acid, and organic acids, including, for example, acetic, chloroacetic and trichloroacetic acids.
In the case of treating zinciferous surfaces (e.g., galvanized steel), PCT International Patent Application Publication No. WO 97/09127 discloses treating the surface prior to autodeposition with a composition consisting of water, dissolved phosphonate (for example, diethylene triaminepenta(methylene phosphonic acid) or aminotri(methylene phosphonic acid)), aromatic sulfonate surfactant (for example, disulfonated derivative of dodecyl ether (DOWFAX 2A1 or 2A0)), and dissolved non-oxidizing acid (for example, hydrochloric acid).
Autodeposition coatings are recognized as being very distinct from coatings formed by immersing metallic surfaces in compositions simply comprising solid resin particles dispersed in water (in other words, conventional latices) and coatings formed from acidic aqueous coating compositions that contain dispersed solid resin particles and relatively high amounts of water soluble corrosion inhibitors such as hexavalent chromium compounds (see U.S. Pat. No. 4,242,379). In both instances, the thickness of the resulting coating is not determined by the amount of time in which the metallic surface is immersed in the composition.
SUMMARY OF THE INVENTION
According to the present invention there is provided a composition useful as a primer or a coating that includes (A) an aqueous dispersion of a phenolic resin that includes wate
Cowles Rebecca S.
Kucera Helmut W.
Dearth Miles B.
Lord Corporation
Mulcahy Peter D.
LandOfFree
Aqueous primer or coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous primer or coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous primer or coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2994618