Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1997-01-27
1999-04-20
Simmons, David A.
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
148251, 148273, 148275, C23C 2248
Patent
active
058955321
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for treating the surface of aluminum and aluminum alloy sheet, particularly sheet intended for the manufacture of caps (hereinafter referred to in some cases as aluminum cap stock sheet). More particularly, this invention relates to a process for treating the surface of aluminum cap stock sheet that forms thereon a polymer coating that is highly paint adherent even after the forming operation.
DESCRIPTION OF THE RELATED ART
In addition to having sufficient strength, aluminum cap stock sheet must generally have an excellent proccessability and workability, because of the deep-drawing operation used to form caps. Phosphate-chromate treatments have been executed on aluminum cap stock sheet with the objective of imparting thereto corrosion resistance and paint adherence. However, paint film adherence during the forming operation is inadequate when phosphate-chromate treatments are used by themselves, with the result that paint exfoliation can still occur.
As one example of art directed to solving this problem, Japanese Patent composition for the treatment of metal surfaces". This invention is characterized by the use of a waterborne composition containing a water-soluble zirconium compound plus a water-soluble or water-dispersible resin (e.g., polyacrylic acid, etc.) as a paint undercoating treatment. Unfortunately, in the case of cap stock, which is subjected to a severe forming operation, the undercoating film provided by the described composition is unable to follow deformation of the material during the forming operation, with the result that the art in this invention again does not always prevent such phenomena as paint exfoliation. application as a paint undercoating treatment for aluminum and its alloys". This invention seeks to improve paint adherence through the addition of another essential component to the known composition of water-soluble zirconium compound+polyacrylic acid. This additional component consists of a water-soluble substance that contains the amino, amide, or imino group. However, the presence of said water-soluble substance containing the amino, amide, or imino group as an essential component of the undercoating treatment bath causes the treatment bath to have a short pot life and therefore greatly complicates the maintenance of stable film characteristics.
PROBLEMS TO BE SOLVED BY THE INVENTION
Thus, there has yet to appear a surface treatment process that provides the surface of aluminum cap stock with a treatment film that, after the forming operation, is strongly adherent to paint films applied on the aluminum or aluminum alloy stock and is also highly corrosion resistant. Moreover, such a process in which the treatment bath has a long pot life is also unknown.
Therefore, the present invention takes as its object the introduction of a process, for treating the surface of aluminum and aluminum alloys, which uses a waterbome composition in which the undercoating treatment bath is relatively stable during prolonged use and which provides corrosion resistance and paint adherence even after a forming operation such as is used for cap manufacturing.
SUMMARY OF THE INVENTION
The present inventors discovered that the aforementioned object could be accomplished by the formation of a polymer coating on the surface of aluminum sheet or aluminum alloy sheet by coating thereof with a liquid waterborne composition in which a water-soluble zirconium compound is combined with at least one selection from acrylic polymers and copolymers that have a glass-transition temperature no greater than 0.degree. C., and by thereafter drying, preferably without any intermediate rinsing.
DETAILED DESCRIPTION OF THE INVENTION, INCLUDING PREFERRED EMBODIMENTS
Aluminum sheet, aluminum alloy sheet, and the like comprise the aluminum and aluminum alloy cap stock to which the present invention is directed. The aluminum alloy is specifically exemplified by aluminum-manganese-iron alloys, aluminum-iron-silicon alloys, aluminum-iron-magnesium allo
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the Conversion Treatment of Aluminum! in Nihon Paakaraijiaya Gihou (Nihon Parkerizing Technical Reports) 1988, No. 1, pub. Jul. 3, 1988 (unavailable).
Nakada Kazuya
Nakamura Mitsuru
Wada Hiroyuki
Henkel Corporation
Jaeschke Wayne C.
Johnson Lance G.
Koehler Robert R.
Simmons David A.
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