Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2001-05-12
2003-04-29
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S247000, C148S251000, C148S254000, C148S265000, C427S189000, C427S221000, C428S469000, C428S472200
Reexamination Certificate
active
06554916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a treatment for making a heat exchanger, especially, a car evaporator which is used in air conditioners such as those for vehicles, hydrophilic, more specifically, a treatment method for making a heat exchanger with an excellent lasting hydrophilicity, deodorizing capability and corrosion resistance hydrophilic, and a heat exchanger treated to be hydrophilic by said method (hydrophilic heat exchanger).
2. Background Art
In general, heat exchangers are constructed of aluminum, and complex in structure having aluminum fins for the heat exchange held between pipes within narrow spaces. Therefore, it has been devised so as to facilitate the discharge of condensed water during the cooling operation by making the surface of aluminum fins, etc. hydrophilic. However, since the surface of aluminum fins, etc, which has been made hydrophilic as described above, is exposed to severe conditions including the repeated cycle of “heating←→cooling”, and adhesion of condensed water, atmospheric dusts or microorganisms, there have been problems that it is difficult to maintain the hydrophilicity of the surface of heat exchanger for a long period.
A variety of inventions have been made to solve these problems, and, for example, in Japanese Patent Laid-open Publication No. Hei 5-202313, a treatment agent for hydrophilicity comprising a mixture of polyvinyl alcohol and water-dispersible silica or a complex thereof, and lithium metasilicate has been disclosed. Herein, lithium metasilicate is said to be effective in maintaining the lasting hydrophilicity, lowering the freezing temperature and expressing antimicrobial activity.
In addition, in Japanese Patent Laid-open Publication No. Hei 5-214273, a paint composition consisting of a water-soluble or water-dispersible organic resin, nitrogen-containing anticorrosive and silica particulates, and coated aluminum materials with coating film obtained from this paint composition have been disclosed.
Furthermore, in Japanese Patent Publication No. 2649297, a paint composition for fin materials made of aluminum or aluminum alloy containing water-soluble or water-dispersible organic resin (excluding water-soluble amino resins), water-soluble amino resin, water-dispersed agglutinating colloidal silica containing silanol groups of 50 m&mgr;~2 m&mgr; in particle size, or water-dispersible humed silica powder, and a surfactant with HLB value of 8~18, fin materials and a method for manufacturing these fin materials have been disclosed. This invention aims at obtaining a pre-coated type fin material and a hydrophilic coating resistant to drawless processing (ironing) during the manufacturing of heat exchanger.
In addition, in Japanese Patent Laid-open Publication No. Hei 10-30069, an aqueous agent to give hydrophilicity containing colloidal silica of 5~100 nm in dispersed particle size and carboxylic acid polymer at pH 1~5, and a method for manufacturing pre-coated fin materials for the heat exchanger using this agent have been disclosed.
All of these aforementioned prior arts have aimed to enhance the hydrophylicity of paint compositions utilizing irregularities of silica surface by using water-soluble or water-dispersible resin together with colloidal silica or particulate silica. However, hydrophilic coatings formed by the combined use of resin and particulate silica tend to deteriorate due to the long time use of heat exchanger. As a result, particulate silica is exposed, posing problems such as emission of silica specific dust smell or stink from materials adsorbed on silica.
Furthermore, fins, etc. of heat exchanger are often assembled (constructed) by brazing using solders such as aluminum-silicon alloy, aluminum-silicon-magnesium alloy, etc. However, deposits from solders adhering to the surface of fins, etc. during brazing often lead to difficulties in rust preventive treatment such as chemical transformation, posing problems such as the decrease in the corrosion resistance of heat exchanger and formation of white rust. Furthermore, there have been other problems that molds growing in water adsorbed to white rust are strewn inside buildings and automobiles by the ventilator fan, generating stink.
The aforementioned problems maybe solved if deposits from solders can be cleaned off by the pretreatment such as washing, it was difficult however to sufficiently clean away said deposits by the conventional washing with acid, alkali or surfactant. For example, in Japanese Patent Laid-open Publication No. Hei 11-131254, a method for treating the surface of aluminum-containing metal materials has been disclosed, wherein the chemical etching treatment of metal materials is performed, prior to the treatment to make the surface hydrophilic, using an acidic aqueous solution containing at least one acid selected from a group consisting of sulfuric acid, hydrofluoric acid, nitric acid and phosphoric acid, and then the chemical transformation technique was applied to the etched surface with the aqueous solution of ziruconium (Zr) phosphate or titanium (Ti) phosphate. However, the aforementioned prior art was not sufficiently effective in removing said deposits, and aluminum-containing metal materials subjected to the treatment to make them hydrophilic still had a tendency to develop white rust in a prolonged salt water spraying test.
In view of the aforementioned problems, the present invention has been made, aiming to provide a treatment method for making a heat exchanger hydrophilic, which is superb in the lasting hydrophilicity, deodorizing capability and corrosion resistance, and a heat exchanger thus treated for making it hydrophilic (hydrophilic heat exchanger).
SUMMARY OF THE INVENTION
To achieve the aforementioned purposes, a treatment method of this invention for making the metal surface hydrophilic aims to sufficiently clean off deposits of solders by devising a pickling agent for the cleaning process performed prior to the chemical transformation treatment, facilitating the subsequent chemical transformation treatment. With such a treatment method, it has become possible for the first time to improve the corrosion resistance of heat exchanger and at the same time prevent the stink emission caused by white rust.
In addition, a treatment method for hydrophilicity of this invention is to enhance the lasting hydrophilicity and deodorizing capability of the heat exchanger by using a treatment for making the metal surface hydrophilic comprising silica particulates coated with polymer of vinyl alcohol series dispersed in aqueous medium.
Specifically, this invention provides the following cleaners and cleaning methods.
(1) A pickling method for a heat exchanger made of aluminum materials, wherein a cleaning treatment is performed by bringing said heat exchanger into contact with a pickling agent containing at least one acid selected from a group comprising nitric acid, sulfuric acid and hydrofluoric acid prior to the chemical transformation treatment applied to said heat exchanger.
As the example of a pickling agent used in this invention, there are aqueous solutions comprising nitric acid, sulfuric acid or hydrofluoric acid, or combinations thereof, and further supplemented with iron salts. The acid concentration of these cleaners is preferably 1~10 N, more preferably 3~5 N.
(2) The pickling method according to the aforementioned (1), wherein said pickling agent contains an iron salt.
(3) The pickling method according to the aforementioned (2), wherein said iron salt is iron sulfate, iron nitrate, iron acetate or iron chloride.
(4) The pickling method according to the aforementioned (2) or (3), wherein said pickling agent contains an iron salt in the range 0.01~5 weight percent.
Said pickling agents preferably contain iron salts such as iron sulfate, iron nitrate, iron acetate, iron chloride, etc. Said iron salts are contained favorably at 0.01~5 weight percent in an acidic aqueous solution, more preferably made to contain at 0.1~1 weight percent. It is advantageous that
Inbe Toshio
Kojima Masahiro
Matsukawa Masahiko
Nakagawa Shintaro
Sudo Takashi
Nippon Paint Co. Ltd.
Oltman Andrew L.
Sheehan John
LandOfFree
Treatment method for making heat exchanger hydrophilic and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Treatment method for making heat exchanger hydrophilic and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Treatment method for making heat exchanger hydrophilic and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3102202