Heat exchange – With coated – roughened or polished surface
Reexamination Certificate
2002-03-26
2003-12-09
Bennett, Henry (Department: 3743)
Heat exchange
With coated, roughened or polished surface
C165S134100, C427S409000, C427S388200, C525S056000
Reexamination Certificate
active
06659171
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a modifier for hydrophilicity and a hydrophilic modification method to be used for providing evaporators and heat exchangers with good and hydrophilicity and odor preventing ability even during a long period of use.
PRIOR ART
Evaporators and heat exchangers generally have a complicated structure, namely they have aluminum fins arranged therein at short intervals for heat exchange and further have aluminum tubes intricately arranged for feeding a cooling medium to these fins. Therefore, the discharge of water condensed upon cooling operation is facilitated by modifying the surface of aluminum fins hydrophilic. However, the above surface of aluminum fins which are modified hydrophilic or the like is exposed to severe conditions, namely to repeated heating and cooling and mixed adhesion of condensed water and dust and microorganisms in the atmosphere. Therefore, it is difficult for that surface to retain hydrophilicity over a long period of time.
Japanese Kokai Publication Hei-05-302042 discloses modifiers for hydrophilicity comprising polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), nylon, phenolic resin, etc. Japanese Kokai Publication Hei-05-202313, Japanese Kokai Publication Hei-05-214273, JP 2649297 and Japanese Kokai Publication Hei-10-30069 disclose modifiers for hydrophilicity comprising water-dispersible organic resins and silica or alumina. Furthermore, Japanese Kokai Publication Hei-09-087576 discloses compositions for hydrophilic modification comprising minute hydrophilic cross-linked acrylic polymer particles.
Japanese Kokai Publication Hei-07-323500, Japanese Kokai Publication Hei-09-14889 and Japanese Kokai Publication Hei-11-131254 disclose modifiers for hydrophilicity intended for retaining hydrophilicity by crosslinking such polar functional groups as sulfonic acid groups and acrylamide for insolubilization.
Japanese Kokai Publication 2000-262968 discloses a coat for aluminum fins which comprises PVA having a degree of saponification of not less than 90% and a metal salt and are intended for suppressing odor emanation and deterioration in hydrophilicity.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a hydrophilic modification method of heat exchangers, which method is capable of suppressing not only the odor of the resulting hydrophilic coat itself but also the unpleasant odor emanation after exposure to odorants and retaining the hydrophilicity even during a long period of use. A further object is to provide a heat exchanger treated by said hydrophilic modification method.
The present inventors found that when heat exchangers, after treatment for rust prevention, are treated with a modifier for hydrophilicity comprising a modified polyvinyl alcohol having a specific amount, in side chains, of groups resulting from addition of 1 of 500 moles of ethylene oxide, the heat exchangers thus coated with a hydrophilic coat can suppress possible odor emanation from the aluminum or like material of the above heat exchangers and from the above hydrophilic coat itself even during a long period of use and, even after exposure to an odorant, such as tobacco, sweat or perfume, can suppress emanation of the unpleasant odor of such odorant and, furthermore, can retain a sufficient hydrophilicity. The present invention has been completed on the basis of such findings.
The present invention thus provides a hydrophilic modification method comprising
a step of forming a coat having a solid coat amount of 0.02 to 3 g/m
2
on a heat exchanger with a modifier for hydrophilicity after treatment for rust prevention thereof
wherein said modifier for hydrophilicity comprises a modified polyvinyl alcohol (A) having, on a side chain thereof, a group represented by the formula (I):
in the formula, n represents an integer of 1 to 500, R
1
represents a hydrogen atom or an alkyl group containing 1 to 4 carbon atoms, and R
2
represents a hydrogen atom or a methyl group,
and at least one member (B) selected from the group consisting of phosphorus compound salts and boron compound salts of Ca, Al, Mg, Fe and Zn,
said group represented by the formula (I) accounting for 0.01 to 20 mole percent relative to hydroxyl and acetoxy groups contained in the above modified polyvinyl alcohol.
The above modifier for hydrophilicity may further contain 0.1 to 30% by mass, relative to the above modifier for hydrophilicity, of a polyvinyl alcohol having a degree of saponification of not less than 90%.
The above-mentioned modified polyvinyl alcohol (A) preferably accounts for 0.1 to 30% by mass relative to the above modifier for hydrophilicity.
The above-mentioned at least one member (B) selected from the group consisting of phosphorus compound salts and boron compound salts of Ca, Al, Mg, Fe and Zn preferably accounts for 0.1 to 200% by mass relative to a resin solid matter.
The above heat exchanger is preferably made of an aluminum or aluminum alloy material.
The present invention is also directed to a heat exchanger treated by the above hydrophilic modification method.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention is described in detail.
The hydrophilic modification method of the invention comprises a step of forming a coat having a solid coat amount of 0.02 to 3 g/m
2
on a heat exchanger with a modifier for hydrophilicity after treatment for rust prevention thereof.
The above heat exchanger is not particularly restricted but is preferably made of an aluminum or aluminum alloy material.
Generally, the above heat exchanger is subjected in advance to degreasing treatment by cleaning with an acidic or alkaline cleaning agent.
The above acidic cleaning agent is not particularly restricted but includes, for example, acidic aqueous solutions such as those of nitric acid, sulfuric acid and hydrofluoric acid or a combination of these. The acid concentration of the above acidic cleaning agent is preferably 1 to 10 N, more preferably 3 to 6 N. It is also preferable to supplement the above acidic cleaning agent with a salt or acid salt of a metal selected from among iron, nickel, cobalt, molybdenum and cerium.
The above alkaline cleaning agent is not particularly restricted but includes, for example, alkaline aqueous solutions containing at least one of sodium hydroxide, sodium silicate and sodium phosphate. A surfactant may be added to the above alkaline aqueous solutions to thereby increase the detergency thereof.
The method of cleaning the above heat exchanger is not particularly restricted but may comprise, for example, spraying the heat exchanger with the above cleaning agent or immersing the heat exchanger in a bath containing the above cleaning agent. The liquid temperature of the above cleaning agent is preferably 10 to 70° C., and the time of contact with the above cleaning agent is preferably 1 second to 5 minutes. When the liquid temperature is below 10° C. or the above time of contact is shorter than 1 second, the etching may be insufficient and, a temperature exceeding 70° C. or a time exceeding 5 minutes may be unfavorable from the economical viewpoint. The heat exchanger cleaned in the above manner is washed with water and then subjected to treatment for rust prevention.
The above treatment for rust prevention is carried out in the manner of chemical conversion treatment using a chemical conversion agent. Usable as the above chemical conversion agent are the conventional chromatic chromating agent, phosphoric chromating agent and nonchromic treatment agent.
The above chromic chromating agent is an aqueous solution containing chromic acid, a fluoride and a strong acid, and includes a reactive chromate and electrolytic chromate whose main component is trivalent chromium, and a coating type chromate in which hexavalent and trivalent chromium are admixed. The above phosphoric chromating agent is a mixed aqueous solution containing chromic acid, orthophosphoric acid and a fluoride. In carrying out chemical conversion treatment with the above chromating agent, it is necessary to control the amoun
Inbe Toshio
Kasebe Osamu
Kobayashi Kengo
Maekawa Susumu
Matsui Norizumi
Bennett Henry
Duong Tho V
Nippon Paint Co. Ltd.
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