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
2000-01-11
2002-04-09
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...
C427S354000, C427S388400, C427S421100, C427S435000, C148S251000, C148S253000
Reexamination Certificate
active
06369149
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel surface treatment liquid composition, usually for brevity called hereinafter a “bathe”, even though it may be applied to surfaces by other methods than immersion, that imparts an excellent corrosion resistance and paint adherence to aluminiferous surfaces (i.e., a surface of pure aluminum or of any aluminum alloy that contains at least 50 atomic percent of aluminum) after the aluminiferous surface is contacted with the bath according to the invention, prior to the painting of the aluminiferous surface. The invention also relates to a process for treating the surface of aluminiferous materials using this novel surface treatment bath. The present invention can be applied with particularly good results to the surface treatment of drawn-and-ironed, alternatively called “draw-ironed” and hereinafter usually abbreviated as “D”, aluminum cans. That is, the present invention relates most specifically and most preferably to a novel aqueous surface treatment bath (1) that imparts an excellent corrosion resistance and paint adherence to the surfaces of aluminum DI cans prior to the painting or printing of the can surfaces and (2) that also supplies the excellent slidability required for the smooth conveyor transport of the cans (hereinafter abbreviated simply as slidability). The invention additionally relates to a process for treating the surface of aluminiferous materials using the described surface treatment bath.
BACKGROUND OF THE INVENTION
DI cans are already known as a type of two piece can. A DI can is fabricated by a drawing process and an ensuing ironing process. Tin-plated steel and aluminum alloy are used as the metal stock for DI cans based on their excellent workabilities. Draw-ironed aluminum alloy cans are in wide use at the present time for beer and carbonated beverages.
In the case of a draw-ironed can, painting is generally carried out on the already fabricated can body, and a variety of surface treatments have been carried out on the can body prior to its painting in order to improve the corrosion resistance of the can body and its adherence to paint films. Phosphate-chromate conversion treatments (chromium systems, see U.S. Pat. No. 2,438,877) and zirconium system conversion treatments (nonchromium systems, see Japanese Patent Application Laid Open (Kokai or Unexamined) Number Sho 52-131937 (131,937/1977)) are widely used commercially as surface treatments for DI aluminum alloy cans. Conversion treatment is a process in which a coating is formed on a surface by chemical reactions that occur, without any need for imposition of electric current from an outside source, when the workpiece and a treatment bath are brought into contact. This process is also known as “chemical conversion coating” and “conversion coating”. Phosphate-chromate conversion treatments employ conversion treatment baths that contain hexavalent chromium and are thus a burden on wastewater treatment and are undesirable from an environmental standpoint. The surface treatment coatings produced by zirconium system conversion treatments suffer from problems, vide infra, with regard to corrosion resistance (particularly resistance to retort whitening), adherence (particularly in the case of a neck-in with its high degree of working), and slidability.
Once a DI aluminum alloy can has been subjected to surface treatment, the outer wall is typically printed with any of various designs adapted to the fill that will be introduced later and the inner wall is painted with a paint that will improve the corrosion resistance. Thus, both the inner and outer walls are overcoated with paint or ink and only the outer surface of the bottom of the can is typically left unpainted. After these processes have been completed, the can body is filled with any of various contents, such as beer or juice, provided with a lid, and sealed. The filled can is then submitted to a sterilizing treatment.
The sterilization conditions vary as a function of the particular fill. The sterilization methodologies include sterilization by immersing the can in hot water at 65 to 90° C. and more severe, higher temperature sterilization methods in which the can is exposed to an atmosphere at 115 to 130° C. (generally a retort treatment). For example, retort treatment is carried out when the fill is caféau lait or tea. As stated above, the bottom of a DI aluminum alloy can is basically left unpainted. As a result, when the coating produced by the surface treatment exhibits a poor corrosion resistance, the aluminum will become oxidized (corroded) in this region during the sterilization processes under discussion and a discolored appearance will be produced. More specifically, a black discoloration is typically produced by immersion in hot water, while a white discoloration is typically produced by retort treatment. Aluminum oxide is white in its native form, but in the case of immersion in hot water the growing oxide takes up, for example, the hardness components in the water and takes on a black color. These phenomena are generally known as “whitening” and “blackening”. At the level of practical applications, the surface treatment coatings produced by the heretofore known phosphate-chromate conversion treatments and zirconium system conversion treatments are prone to undergo whitening during retort treatment, and the bottom is often painted in commercial applications to counter this problem. Moreover, since retort treatments in some cases cause a loss of adherence by ink on the outer surface, a type of primer known as a size coat or sizing may be applied prior to printing when a retort treatment will be carried out. No surface treatment coating is known at the present time that exhibits a high corrosion resistance and that, in the absence of a size coat, can prevent a loss of ink adherence during retort treatment.
Another problem area in the can fabrication process is the frequent transport upsets that can occur during the conveyor transport of cans. These upsets occur when a can tips over sideways and are due to the poor slidability of the can surface caused by a high friction coefficient of the outer can surface. Can conveyability is a particularly critical issue for transport to the printer. This creates a requirement in the can fabrication process for a reduction in the coefficient of static friction of the cans without any associated impairment in the adherence of the paint or ink that will be applied to the cans. An example of methods for improving the slidability is the invention disclosed in Japanese Patent Application Laid Open (Kokai or Unexamined) Number Sho 64-85292 (85,292/1989). This invention relates to a surface treatment agent for metal cans that contains water-soluble organic substance selected from phosphate esters, alcohols, monovalent and polyvalent fatty acids, fatty acid derivatives, and mixtures of the preceding. However, while the disclosed method does produce an increase in the slidability, it does not produce improvements in the corrosion resistance or paint adherence. Another method directed to improving the slidability is the invention disclosed in Japanese Patent Application Laid Open (Kokai or Unexamined) Number Hei 5-239434 (239,434/1993). This method, which uses phosphate ester, again produces an increase in the slidability, but again also does not produce improvements in the corrosion resistance or paint adherence.
As indicated above, once a can has been filled with its contents, for example, juice, the lid is rolled on and the can is sealed. The desire to economize on lid stock has resulted in the use of lid diameters that are smaller than the diameter of the can body. The constriction or reduction in the diameter of the can body is known as the “neck-in”. At present, the diameter of the 350 milliliter (hereinafter usually abbreviated as “mL”) can body primarily used for beer, etc., is denoted as “211” for (2+{fraction (11/16)}) inches, while the lid diameter is (2+{fraction (6/16)}) inches or “206”. Thus, the lid end of the can body is necked in f
Oshita Ken-ichiro
Shimizu Akio
Yoshida Masayuki
Harper Stephen D.
Henkel Corporation
Jaeschke Wayne C.
Mulcahy Peter D.
LandOfFree
Aqueous treatment process and bath for aluminiferous surfaces 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 treatment process and bath for aluminiferous surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous treatment process and bath for aluminiferous surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2847814