Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2002-04-25
2003-04-01
Green, Anthony J. (Department: 1755)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C106S014120, C106S014440, C148S259000
Reexamination Certificate
active
06540845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aqueous agent for treating metal surfaces, more particularly to an aqueous agent for treating metal surfaces that is capable of removing oils adhering to metal surfaces and of forming a water-insoluble zinc phosphate coat on the surfaces.
2. Description of Related art
The invention disclosed in examined Japanese patent application publication No. 57-49111(1982) relates to a conventional technology of forming an iron phosphate coat on a metal surface to provide the surface with rust resisting properties. The publication teaches a composition for producing a phosphate on a metal surface to form an essentially water-insoluble iron phosphate coat that has an improved surface-adhesion and enhanced humidity resistance. Although the iron phosphate coat made by this composition worked sufficiently as a primer coat that was used in some fields, the coat was inferior in rust prevention compared with a zinc phosphate coat formed by an aqueous composition that was used in the automobile industry and home electric appliances industry.
Unexamined Japanese patent application publication No. 52-107244(1977) discloses another composition. This composition is a zinc phosphate coat-forming agent prepared by mixing an acidic zinc phosphate aqueous solution that includes zinc ions and phosphate ions with nitrate ions and chlorate ions so that the ratio of nitrate ions to chlorate ions and that of phosphate ions to chlorate ions to nitrate ions are respectively within specified ranges. However, forming a zinc phosphate coat on a metal surface using the aqueous agent required complicated multiple steps; degreasing step, water washing step, pure water washing step, surface-conditioning step, coat-forming step, water washing step, pure water washing step and drying step in this order. Another defect was that, because a great amount of water was necessary for this process, the dehydration required special equipment and was costly. Besides, because the nitrate ions serve as a catalyst in this composition, as the concentration of nitrate ions was increased, the value of pH was decreased, which led to a failure in forming the coat.
In order to remove the defects of this zinc phosphate coat-forming agent, a phosphoric acid-treating agent was proposed in unexamined Japanese patent application publication No. 4-128383(1992). This phosphoric acid-treating agent is substantially a non-aqueous composition for forming a phosphoric acid coat on a metal surface, comprising a first solvent mixture of 100 parts by weight of a polar organic solvent with not more than 100 parts by weight of water, phosphoric acid, zinc ions and a solubilizer, wherein the phosphoric acid, the zinc ions and the solubilizer are present in specific amounts respectively based on 100 parts by weight of the first solvent mixture.
The phosphoric acid agent of unexamined Japanese patent application publication No. 4-128383(1992), however, contains a large amount of polar organic solvent and therefore is inflammable. The user has to handle it with a great care. In the examples of this publication are used for the polar solvent methanol, ethanol, isopropanol, t-butanol, ethylene chloride and acetonitrile. When the amount of water exceeds 100 parts by weight based on 100 parts by weight of these polar solvents, the solubility of the formed coat increases, which hinders the formation of a substantially uniform coat. The phosphoric acid agent described in this publication includes not less than 50% of the polar solvent and therefore oil adhering to the metal surface being treated dissolves in the polar solvent very well. In other words, this phosphoric acid agent removes oil that is present on the metal surface being treated by dissolving the oil in the polar solvent the agent includes in an amount larger than the amount of water. As the agent is used repeatedly, the polar solvent becomes saturated with oil. Then the phosphoric acid agent separates into a solvent layer that includes oil with a small amount of water, phosphate ions, zinc ions and the solubilizer and a water layer that includes water, phosphate ions, zinc ions and the solubilizer with a small amount of the polar solvent. This separation hinders a normal formation of the zinc phosphate coat. Consequently, it is absolutely necessary to regularly control the amount of oil that dissolves in the phosphoric acid agent. In other words, as the amount of oil dissolved in the phosphoric acid agent increases, the agent requires such a complicated maintenance as a replacement of the solution or regeneration thereof by distillation. In view of these problems, treating agents that require an easier maintenance have been desired.
The object of the invention is to solve the aforementioned problems. Specifically, an objective of the invention is to provide an aqueous agent for treating metal surfaces, in which agent a metal article is immersed to remove from the surface of the metal article such oils as lubricating oil, examples of which are cutting oil and hydraulic actuation oil, and preservative oil, and to form a zinc phosphate coat on it. Another objective of the invention is to provide an aqueous agent for treating metal surfaces which makes the removed oil float to the surface of the agent when the amount of the dissolved oil reaches to the saturation, whereby the excessive oil can easily be removed and the agent does not separate into layers. A still further objective of the invention is to provide an aqueous agent for treating metal surfaces, with which can desirably be formed a zinc phosphate coat excellent in adhesion and preservative properties.
SUMMARY OF THE INVENTION
In the present invention, the aforementioned problems are solved by an aqueous agent for treating metal surfaces including 100 parts by weight of an aqueous solution that comprises from more than 12 weight % to less than 50 weight % of a water-soluble organic solvent and from more than 50 weight % to less than 88 weight % of water, 0.01-4.25 parts by weight of phosphate ions, 0.02-45 parts by weight of nitrate ions, and 0.01-6.5 parts by weight of zinc ions.
In a preferred embodiment of the invention, the aqueous solution comprises from more than 12 weight % to 45 weight % of the water-soluble organic solvent and from 55 weight % to less than 88 weight % of the water.
In another preferred embodiment of the invention, the water-soluble organic solvent is at least one glycol compound selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether and propylene glycol monoalkyl ether, or a mixture of the glycol compound with a lower alcohol.
In a further preferred embodiment, the respective aqueous agents of the aforementioned embodiments additionally include up to 6 parts by weight of monovalent ions of an alkaline metal.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Generally, when a treating agent for forming a zinc phosphate coat on a metal surface is aqueous, the process of the formation requires complicated multiple steps; degreasing step, water washing step, pure water washing step, surface-conditioning step, coat-forming step, etc. The aqueous agent for treating metal surfaces in accordance with the invention, however, does not require such multiple steps but needs only one step in one tank for degreasing and forming a zinc phosphate coat. Another advantage is that the aqueous agent of the invention can remove oils from the metal surface although the agent is aqueous, and form a uniform zinc phosphate coat on the surface. In a case where is employed a conventional non-aqueous phosphoric acid agent including a water-containing solvent that comprises 50% or more of alcohol and a water-containing organic solvent that comprises 50% or more of chlorinated hydrocarbons, the formed coat is more dissolved in the agent and a substantially uniform coat can hardly be obtained when the amount of the water exceeds 100 parts by w
Okada Hirokuni
Oyama Masaki
Green Anthony J.
Nippon Dacro Shamrock Co., Ltd.
Webb Ziesenhiem Logsdon Orkin & Hanson. P.C.
LandOfFree
Aqueous metal surface treating agent 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 metal surface treating agent, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous metal surface treating agent will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3041467