Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
1999-05-11
2001-04-17
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S251000, C427S410000, C427S419500, C405S014000, C405S014000
Reexamination Certificate
active
06217674
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to passivating compositions and a process for treating metal substrates prior to the application of a decorative or protective coating.
Passivating metal substrates with a phosphate conversion coating and chrome-containing rinse, prior to the application of a protective or decorative coating, is well known for promoting corrosion resistance. Phosphate conversion coating compositions typically contain heavy metals such as nickel and post-rinses contain chrome, producing waste streams that pose environmental concerns and which are expensive to dispose.
Rinsing compositions utilizing metal ions other than chromium are also known in the art and are disclosed, for example, in U.S. Pat. Nos. 3,966,502 and 4,132,572. U.S. Pat. No. 3,966,502 discloses treatment of phosphated metals with zirconium-containing rinse solutions. Other rinse compositions containing combinations of Group IVB metal ions with polymeric materials have also been used over phosphated substrates. See, for example, U.S. Pat. Nos. 3,912,548, 5,209,788, and 5,653,823. However, many post-rinse compositions are suitable for use over a limited number of substrates or over substrates that must be phosphated first.
It would be desirable to provide a composition for passivating metal substrates prior to the application of a protective or decorative coating which is substantially free of chrome. Preferably the composition would be effective in passivating a number of metal substrates, particularly metallic objects fashioned with more than one substrate type, such as are commonly found on automobile bodies, so that the need to perform separate passivating treatments would be eliminated. More preferably, the compositions would additionally be effective in passivating untreated (i.e. non-phosphated) metal substrates.
SUMMARY OF THE INVENTION
In accordance with the present invention, a composition for passivating a metal substrate is provided. The composition is prepared by mixing together, usually in a carrier medium:
a) a Group IIIB or IVB metal compound; and
b) a reaction product of an epoxy group-containing polymer or oligomer such as a polyglycidyl ether of a polyphenol, a hydroxy acid such as dimethylolpropionic acid and a dialkanolamine such as diethanolamine.
Also provided is a process for treating a metal substrate by contacting the substrate with the composition. The process may further include subsequent steps of coating the substrate with any of a number of protective or decorative film-forming compositions, including coatings applied by electrodeposition, primers applied by non-electrophoretic means, and powder coating compositions.
DETAILED DESCRIPTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used in the specification and claims are to be understood as modified in all instances by the term “about”. The composition and process of the present invention are typically used to passivate metal substrates such as cold rolled steel, steel coated with zinc metal, zinc compounds or zinc alloys such as electrogalvanized steel, hot-dipped galvanized steel, galvanealed steel, and steel plated with zinc alloy. Also, aluminum alloys, aluminum plated steel and aluminum alloy plated steel substrates may be used. Preferably, the substrate is a multimetal substrate containing two or more metals such as cold rolled steel; steel coated or plated with zinc metal, zinc compounds or zinc alloys and aluminum. By passivation is meant the process of applying a treatment to a metal substrate which improves its corrosion resistance compared to its resistance without such a treatment.
The substrate is usually first cleaned to remove grease, dirt, or other extraneous matter. This is done by employing conventional cleaning procedures and materials. These would include mild or strong alkaline cleaners such as are commercially available and conventionally used in metal pretreatment processes. Examples of alkaline cleaners include Chemkleen 163 and Chemkleen 177, both of which are available from PPG Industries, Pretreatment and Specialty Products. Such cleaners are generally followed and/or preceded by a water rinse(s).
Optionally, the metal surface may be rinsed with an aqueous acidic solution after cleaning with the alkaline cleaner and before contact with the composition. Examples of rinse solutions include mild or strong acidic cleaners such as the dilute nitric acid solutions commercially available and conventionally used in metal pretreatment processes.
The metal substrate may also optionally be phosphated. Suitable phosphate conversion coating compositions may be any of those known in the art. Examples include zinc phosphate, iron phosphate, manganese phosphate, calcium phosphate, magnesium phosphate, cobalt phosphate, zinc-iron phosphate, zinc-manganese phosphate, zinc-calcium phosphate, and layers of other types, which may contain one or more multi-valent cations. Phosphating compositions are known to those skilled in the art and are described in U.S. Pat. Nos. 4,941,930, 5,238,506, and 5,653,790.
Following the optional cleaning and phosphating steps, the metal surface is contacted with the composition of the present invention.
The composition of the present invention is typically dispersed or dissolved in a carrier medium, usually an aqueous medium. The solution or dispersion may be applied to the metal substrate by known application techniques, such as dipping or immersion, which is preferred, spraying, intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing, or by roll-coating. Typically, the solution or dispersion when applied to the metal substrate is at a temperature ranging from 60 to 150° F. (15 to 65° C.). The contact time is generally between 10 seconds and five minutes, preferably 30 seconds to 2 minutes.
The Group IIIB or IVB metals referred to herein are those elements included in such groups in the CAS Periodic Table of the Elements as is shown, for example, in the
Handbook of Chemistry and Physics,
63rd Edition (1983). Where applicable, the metals themselves, but more usually metal compounds are used.
Preferred Group IIIB and IVB metal compounds are compounds of zirconium, titanium, hafnium, yttrium and cerium and mixtures thereof. Typical zirconium compounds may be selected from hexafluorozirconic acid, alkali metal and ammonium salts thereof, ammonium zirconium carbonate, zirconyl nitrate, zirconium carboxylates and zirconium hydroxy carboxylates such as hydrofluorozirconic acid, zirconium acetate, zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium lactate, ammonium zirconium citrate, and mixtures thereof. Hexafluorozirconic acid is preferred. An example of the yttrium compound is yttrium nitrate. An example of the titanium compound is fluorotitanic acid and its salts. An example of the hafnium compound is hafnium nitrate. An example of the cerium compound is cerous nitrate. The Group IIIB or IVB metal compound is typically present in the carrier medium in an amount of 10 to 5000 ppm metal, preferably 100 to 1000 ppm metal based on total weight of the composition. The pH of the medium is usually from 2.0 to 7.0, preferably 2.7 to 6.5. The pH of the medium may be adjusted using mineral acids such as hydrofluoric acid, fluoroboric acid, phosphoric acid, and the like, including mixtures thereof; organic acids such as lactic acid, acetic acid, citric acid, sulfamic acid, or mixtures thereof; and water soluble or water dispersible bases such as sodium hydroxide, ammonium hydroxide, ammonia, or amines such as triethylamine, methylethyl amine, or mixtures thereof.
The composition also contains the reaction product of an epoxy-containing polymer or oligomer (polyepoxide) with a dialkanolamine and a hydroxy acid. Examples of suitable epoxy-containing polymers or oligomers include polyglycidyl ethers of polyhydric phenols such as the polyglycidyl ether of Bisphenol A. The preferred polyglycidyl ether is the diglycidyl ether
Gray Ralph C.
Hauser Brian T.
Valko Joseph T.
Oltmans Andrew L.
PPG Industries Ohio Inc.
Sheehan John
Uhl William J.
LandOfFree
Compositions and process for treating metal substrates does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compositions and process for treating metal substrates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compositions and process for treating metal substrates will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2553034