Coating processes – With pretreatment of the base – Metal base
Reexamination Certificate
2000-01-03
2001-06-19
Beck, Shrive (Department: 1762)
Coating processes
With pretreatment of the base
Metal base
C427S397700, C427S409000, C427S410000, C427S419700, C156S329000
Reexamination Certificate
active
06248403
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wipe solvent compositions for application to various substrates, including metal finishes/coatings such as anodized, Alodined, deoxidized, abraded, bare metals, fiberglass, plastic films, organic coatings, composites, glass and other substrates, for purposes of cleaning the substrate surface to improve the receptivity and bonding properties of the substrate relative to organic coatings, adhesives, adhesive coatings, primers, adhesive primers, sealants, paints, honeycomb structures and similar materials conventionally bonded to such substrates.
2. State of the Art
It is known to improve the receptivity of substrates for paints, primers and adhesive layers by treating the substrate surface with mechanical abrasive operations such as blasting followed by cleaning with an organic solvent such as methyl ethyl ketone following by brush-coating with a dilute aqueous silane solution and drying. Reference is made to U.S. Pat. No. 5,312,520. The process according to the patent is objectionable because methyl ethyl ketone is a hazardous air pollutant, dangerous to worker safety, and the process requires three separate steps, with the silane brushing step being repeated three times using alternating brush strokes
Reference is also made to U.S. Pat. No. 5,424,133 for its disclosure of a process for preparing a plastic film or composite substrate surface for adhesive bonding coating operations by applying to the surface an abrasive composition containing abrasive particles such as silicon-containing particles and rubbing the coating into the surface to fix the abrasive particles thereto. The surface is first degreased by wiping with a solvent such as isopropanol.
It is known to treat or coat aluminum and other substrates to improve their bonding properties relative to primers , paints, adhesive coatings and other substrates such as composites, metals, glass, etc. Such process typically requires the use of a chemical conversion coating (CCC), such as Alodine, over the aluminum surface to improve the bonding properties of the substrate for paints, adhesives, etc., while enhancing the corrosion resistance of the coating system. The chemical conversion coating composition typically contains chromic acid, a fluoride acid salt and accelerators.
Chromium is an environmentally-objectionable chemical targeted by the EPA for reduction or elimination, and the replacement of chromium-containing plating and treatment baths with non-chromated baths has been the subject of extensive academic and industrial research.
Alternative chromium-free coating compositions have been developed but the process of applying such compositions requires multiple steps, each of which usually requires a different heated process tank as opposed to the single heated process tank required for the conventional chromated chemical conversion coating (CCC) process. The energy and facility requirements of this alternative process create substantial difficulty and expense from the standpoint of implementation into a production facility.
Another alternate chemical conversion process involves the use of a cobalt-amine oxidizing composition such as Alodine 2000 to form a chemical oxide film on aluminum substrates. Such process requires the use of two separate heated process tanks. In the first step a chemical oxide layer is formed on the surface of the aluminum using a cobalt-amine oxidizing bath to form an oxide layer about 1000 angstrom units in thickness. In the second step the oxidized aluminum substrate is immersed in a second tank containing a composition which seals the oxide layer to impart corrosion resistance to the substrate. The first step increases the bonding properties of the aluminum substrate while the second step is required to impart corrosion resistance.
Clearly, it is highly desirable to provide a process which eliminates the need for chemical conversion steps which require the use of chromium or require the use of several heated baths and several steps to enhance adhesion properties to the substrate.
Such processes are tedious, time-consuming and/or dangerous, and are unsatisfactory for use on certain substrates, where abrasion or blasting cannot be used, and are ineffective for certain coatings and bonding operations.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery that environmentally-safe non-chrome surface treating wipe solvent compositions can be produced by incorporating conventional silane or coupling agents in effective, environmentally-safe organic solvents such as naphtha, methyl propyl ketone, isopropyl alcohol, acetone and similar safe, non-carcinogenic volatile organic solvents, or blends of such solvents, having a composite vapor pressure below about 45mmHg, or a volatile organic compound considered exempt by federal, state or local regulations, and that such compositions can be wiped onto various substrate surfaces to simultaneously clean the surfaces and deposit the coupling agent thereon for subsequent bonding to an applied primer, paint, adhesive layer and/or to another substrate such as of composite, metal, glass, plastic or honeycomb composite.
An advantage of the present process resides in the elimination of the conventional chemical conversion coatings that are applied to substrates, such as aluminum, to improve the bonding properties and corrosion-resistance of such substrates. The present process enables the direct application of novel surface treating wipe solvent(s) coatings to the surface of the substrate to simultaneously clean the substrate surface with environmentally-friendly organic solvents and to deposit thereon and bond thereto a coupling agent which functions as a bonding link between the substrate surface and the reactive organic groups contained in the corrosion-resistive primer composition to provide excellent bonding properties therebetween.
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McLaughlin Joanne Swiderski
Weir John Douglas
Anderson Terry J.
Beck Shrive
Crockford Kirsten A.
Hoch, Jr. Karl J.
Northrop Grumman Corporation
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