U.S. patent application number 14/116436 was filed with the patent office on 2014-03-13 for heat exchanger obtained from aluminum or aluminum alloy.
This patent application is currently assigned to NIPPON LIGHT METAL COMPANY, LTD.. The applicant listed for this patent is Reiko Takaswa, Kazuhiko Yamazaki. Invention is credited to Reiko Takaswa, Kazuhiko Yamazaki.
Application Number | 20140069620 14/116436 |
Document ID | / |
Family ID | 47139057 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069620 |
Kind Code |
A1 |
Takaswa; Reiko ; et
al. |
March 13, 2014 |
HEAT EXCHANGER OBTAINED FROM ALUMINUM OR ALUMINUM ALLOY
Abstract
Provided is a heat exchanger including a heat exchange fin in
which frost formation at the time of heater operation can be
prevented to the extent possible, and under such a condition that
condensation is liable to occur on a fin surface, a water droplet
of condensed water can be quickly removed by bringing the water
droplet into contact with a hydrophilic film, and as a result, a
favorable heat exchange function can be continuously obtained
without any increase in ventilation resistance. The heat exchanger
includes a heat exchange fin made of an aluminum plate material
that has a crosslinked hydrophobic film having a frost
formation-suppressing effect and a hydrophilic film, in which: an
area occupied by the crosslinked hydrophobic film in a square area
measuring 10 mm by 10 mm at an arbitrary position on a surface of
the heat exchange fin is 20 to 80%; and the crosslinked hydrophobic
film is formed of an aqueous hydrophobic coating composition
containing a resin (A) having a fluorine atom-containing group, a
quaternary ammonium salt group-containing modified epoxy resin (B),
and an amino resin (C) in which the solid content of the resin (A)
is 1 to 30 parts by mass with respect to 100 parts by mass of the
total of the solid contents of the resin (B) and the resin (C).
Inventors: |
Takaswa; Reiko;
(Shizuoka-shi, JP) ; Yamazaki; Kazuhiko;
(Shizuoka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Takaswa; Reiko
Yamazaki; Kazuhiko |
Shizuoka-shi
Shizuoka-shi |
|
JP
JP |
|
|
Assignee: |
NIPPON LIGHT METAL COMPANY,
LTD.
Tokyo
JP
|
Family ID: |
47139057 |
Appl. No.: |
14/116436 |
Filed: |
March 21, 2012 |
PCT Filed: |
March 21, 2012 |
PCT NO: |
PCT/JP2012/057164 |
371 Date: |
November 8, 2013 |
Current U.S.
Class: |
165/133 ;
427/386 |
Current CPC
Class: |
C09D 133/16 20130101;
F28F 19/04 20130101; C09D 133/16 20130101; F28F 13/18 20130101;
F28F 1/126 20130101; F28F 2245/04 20130101; F28D 1/05333 20130101;
C08L 39/02 20130101; C08L 2205/03 20130101; F28F 2245/02 20130101;
C08F 212/08 20130101; C08F 220/06 20130101; C08L 63/00 20130101;
C08F 220/18 20130101 |
Class at
Publication: |
165/133 ;
427/386 |
International
Class: |
F28F 13/18 20060101
F28F013/18 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2011 |
JP |
2011-105501 |
Claims
1. A heat exchanger, comprising a heat exchange fin having a fin
substrate formed of an aluminum plate material formed of aluminum
or an aluminum alloy, and a crosslinked hydrophobic film having a
frost formation-suppressing effect and a hydrophilic film formed on
a surface of the fin substrate, wherein: an area occupied by the
crosslinked hydrophobic film in a square area measuring 10 mm by 10
mm at an arbitrary position on a surface of the heat exchange fin
is 10 to 90%; and the crosslinked hydrophobic film is formed of an
aqueous hydrophobic coating composition containing a resin (A)
having at least one kind of fluorine atom-containing group selected
from the group consisting of a perfluoroalkyl group and a
perfluoroalkenyl group, a quaternary ammonium salt group-containing
modified epoxy resin (B), and an amino resin (C) in which a solid
content of the resin (A) having at least one kind of fluorine
atom-containing group selected from the group consisting of a
perfluoroalkyl group and a perfluoroalkenyl group is 1 to 30 parts
by mass with respect to 100 parts by mass of a total of solid
contents of the quaternary ammonium salt group-containing modified
epoxy resin (B) and the amino resin (C).
2. A heat exchanger according to claim 1, wherein the hydrophilic
film comprises an inorganic film.
3. A heat exchanger according to claim 1 or 2, wherein the
crosslinked hydrophobic film is formed on the hydrophilic film.
4. A heat exchanger according to claim 1 or 2, wherein the heat
exchange fin comprises a corrugated fin.
5. A heat exchanger according to claim 4, wherein the hydrophilic
film comprises a film formed by a brazing step.
6. A heat exchanger according to claim 1 or 2, wherein the
crosslinked hydrophobic film is formed by baking the aqueous
hydrophobic coating composition after application thereof and has a
thickness of 0.02 to 5.0 g/m.sup.2.
7. A heat exchanger according to claim 1 or 2, wherein the
crosslinked hydrophobic film formed in part of the heat exchange
fin is nonuniform and spotted.
8. A heat exchanger according to claim 2, wherein the crosslinked
hydrophobic film formed in part of the heat exchange fin is formed
on the hydrophilic film, and the crosslinked hydrophobic film and
the hydrophilic film form a sea-island structure.
9. A method of producing a heat exchanger including a heat exchange
fin in which a crosslinked hydrophobic film having a frost
formation-suppressing effect is formed on an entirety or part of a
surface of a fin substrate formed of an aluminum plate material
formed of aluminum or an aluminum alloy, the method comprising:
applying, to the entirety or part of the surface of the fin
substrate, an aqueous hydrophobic coating composition containing a
resin (A) having at least one kind of fluorine atom-containing
group selected from the group consisting of a perfluoroalkyl group
and a perfluoroalkenyl group, a quaternary ammonium salt
group-containing modified epoxy resin (B), and an amino resin (C)
in which a solid content of the resin (A) having at least one kind
of fluorine atom-containing group selected from the group
consisting of a perfluoroalkyl group and a perfluoroalkenyl group
is 1 to 30 parts by mass with respect to 100 parts by mass of a
total of solid contents of the quaternary ammonium salt
group-containing modified epoxy resin (B) and the amino resin (C),
followed by baking of the composition to form the crosslinked
hydrophobic film; and subjecting the crosslinked hydrophobic film
to a post-treatment with one or two or more kinds of post-treatment
liquids selected from water, an acid solution, and an alkaline
solution after the formation of the crosslinked hydrophobic film.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger formed by
using a heat exchange fin that is formed of an aluminum plate
material formed of aluminum or an aluminum alloy, and has an
excellent frost formation-suppressing effect and an excellent
condensed water-removing effect imparted to a surface thereof.
BACKGROUND ART
[0002] A heat exchanger using a heat exchange fin formed of an
aluminum plate material has been used in, for example, air
conditioners, refrigerating equipment, and automobile equipment. In
the heat exchanger for air conditioners, when the temperature of
air is low or the evaporating temperature of a refrigerant is low
in an outdoor unit at the time of heater operation, frost adheres
onto the surface of a fin in some cases. In addition, once the
frost forms, a gap between fins is clogged to increase a
ventilation resistance. Eventually, the quantity of air to flow
into the heat exchanger reduces and hence the evaporating ability
of the heat exchanger of the outdoor unit reduces. Accordingly,
when the frost adheres onto the heat exchanger, the following
problem arises. The heater operation needs to be stopped and a
defrosting operation needs to be performed for removing the frost,
and hence comfortability remarkably reduces.
[0003] In addition, a method involving forming a hydrophobic film
on the surface of the fin is available as a technology for the
suppression of such frost formation. The time period during which
the clogging occurs owing to the frost formation can be postponed
by the method. However, after defrosting or under such a condition
that the temperature of the refrigerant is relatively high so that
a water droplet condenses on the surface of the fin, the method
involves the following problem. Condensed water adheres to the gap
between the fins, the adhering condensed water forms a bridge
between the fins to increase the ventilation resistance, and as a
result, heat exchange performance reduces.
[0004] Accordingly, the following has been demanded for improving
the thermal efficiency of the heat exchanger at the time of the
heater operation. The condensed water on the fin surface is removed
before the frost formation and the fin surface is turned into a
surface on which the frost formation hardly occurs. In addition,
the following methods each have been proposed as means for solving
the problem: a hydrophilic treatment method involving forming a
hydrophilic film on the fin surface to cause the condensed water to
flow down as a thin water film (Patent Literatures 1 to 3); a
hydrophobic treatment method involving forming a hydrophobic film
on the fin surface to remove the condensed water at an early stage
(Patent Literatures 4 to 6); a hydrophobic/hydrophilic treatment
method involving forming a hydrophobic film and a hydrophilic film
depending on the placement and site of the fin to compensate for
the disadvantages of the hydrophobic film and hydrophilic film with
their advantages (Patent Literatures 7 to 9); and the like.
CITATION LIST
Patent Literature
[0005] [PTL 1] JP 09-014888 A [0006] [PTL 2] JP 2000-028291 A
[0007] [PTL 3] JP 2010-223520 A [0008] [PTL 4] JP 08-269367 A
[0009] [PTL 5] JP 09-026286 A [0010] [PTL 6] JP 2009-270181 A
[0011] [PTL 7] JP 08-152287 A [0012] [PTL 8] JP 3761262 B2 [0013]
[PTL 9] JP 2006-046695 A
SUMMARY OF INVENTION
Technical Problem
[0014] However, in the hydrophilic treatment method of each of
Patent Literatures 1 to 3, a function of causing the condensed
water to flow down as a thin water film is not sufficient and
defrosting property by which frost formation is suppressed when
performance of heater operation is not sufficient. In addition, in
the hydrophobic treatment method of each of Patent Literatures 4 to
6 as well, water repellency is not sufficient and defrosting
property by which the frost formation is suppressed through secure
removal of a condensed water droplet is not sufficient. Further, in
each of Patent Literatures 7 to 9, water-repelling performance and
hydrophilic performance, in particular, the water-repelling
performance in the hydrophobic film and hydrophilic film to be
formed depending on the placement and site of the fin, in
particular, the hydrophobic film are not necessarily sufficient.
Accordingly, it is still unable to achieve a satisfactory frost
formation-suppressing effect. In addition, it is still unable to
sufficiently solve the problem of the increase of the ventilation
resistance between the fins due to the condensed water.
[0015] Therefore, in view of the problems of the conventional
technologies, the inventors of the present invention have made
extensive studies to develop a heat exchanger constructed of a heat
exchange fin made of an aluminum plate material that achieves
compatibility between an excellent frost formation-suppressing
effect exhibited by a hydrophobic film and an excellent condensed
water-removing effect exhibited by a hydrophilic film to prevent
frost formation, for example, at the time of heater operation, and
does not cause a problem of an increase in ventilation resistance
between fins due to condensed water. As a result, the inventors
have found that the object can be achieved by introducing a
specific crosslinked structure into the hydrophobic film, and
causing the crosslinked hydrophobic film and the hydrophilic film
to coexist in the same surface of the heat exchange fin, and have
completed the present invention.
[0016] Therefore, an object of the present invention is to provide
a heat exchanger including a heat exchange fin made of an aluminum
plate material in which a crosslinked hydrophobic film and a
hydrophilic film are formed on the same surface of the heat
exchange fin, and compatibility between an excellent frost
formation-suppressing effect exhibited by the crosslinked
hydrophobic film and an excellent condensed water-removing effect
exhibited by the hydrophilic film is achieved, and hence frost
formation at the time of heater operation can be prevented to the
extent possible, and under such a condition that condensation is
liable to occur on a fin surface, a water droplet of condensed
water can be quickly removed by bringing the water droplet into
contact with the hydrophilic film, and as a result, a favorable
heat exchange function can be continuously obtained without any
increase in ventilation resistance.
Solution to Problem
[0017] That is, the present invention is a heat exchanger,
including a heat exchange fin having a fin substrate formed of an
aluminum plate material formed of aluminum or an aluminum alloy,
and a crosslinked hydrophobic film having a frost
formation-suppressing effect (or an anti-frost effect) and a
hydrophilic film formed on a surface of the fin substrate, in
which: an area occupied by the crosslinked hydrophobic film in a
square area measuring 10 mm by 10 mm at an arbitrary position on a
surface of the heat exchange fin is 10 to 90%; and the crosslinked
hydrophobic film is formed of an aqueous hydrophobic coating
composition containing a resin (A) having at least one kind of
fluorine atom-containing group selected from the group consisting
of a perfluoroalkyl group and a perfluoroalkenyl group, a
quaternary ammonium salt group-containing modified epoxy resin (B),
and an amino resin (C) in which a solid content of the resin (A)
having at least one kind of fluorine atom-containing group selected
from the group consisting of a perfluoroalkyl group and a
perfluoroalkenyl group is 1 to 30 parts by mass with respect to 100
parts by mass of a total of solid contents of the quaternary
ammonium salt group-containing modified epoxy resin (B) and the
amino resin (C).
[0018] The present invention is also a method of producing a heat
exchanger including a heat exchange fin in which a crosslinked
hydrophobic film having a frost formation-suppressing effect (or an
anti-frost effect) is formed on an entirety or part of a surface of
a fin substrate formed of an aluminum plate material formed of
aluminum or an aluminum alloy, the method including: applying, to
the entirety or part of the surface of the fin substrate, an
aqueous hydrophobic coating composition containing a resin (A)
having at least one kind of fluorine atom-containing group selected
from the group consisting of a perfluoroalkyl group and a
perfluoroalkenyl group, a quaternary ammonium salt group-containing
modified epoxy resin (B), and an amino resin (C) in which a solid
content of the resin (A) having at least one kind of fluorine
atom-containing group selected from the group consisting of a
perfluoroalkyl group and a perfluoroalkenyl group is 1 to 30 parts
by mass with respect to 100 parts by mass of a total of solid
contents of the quaternary ammonium salt group-containing modified
epoxy resin (B) and the amino resin (C), followed by baking of the
composition to form the crosslinked hydrophobic film; and
subjecting the crosslinked hydrophobic film to a post-treatment
with one or two or more kinds of post-treatment liquids selected
from water, an acid solution, and an alkaline solution after the
formation of the crosslinked hydrophobic film.
[0019] In the present invention, the aluminum plate material
forming the fin substrate may be formed of pure aluminum or may be
formed of an aluminum alloy, and is not particularly limited. From
the viewpoint of corrosion resistance, an anticorrosive film may be
formed on each of both surfaces of the fin substrate.
[0020] The anticorrosive film to be formed on each of both surfaces
of the fin substrate for the purpose is formed by applying an
anticorrosive treatment agent to each of both surfaces of the fin
substrate, or by performing an emmersion treatment. Examples of the
anticorrosive treatment agent to be used here can include a
chromate, chromate-phosphate, a chromium-free chemical conversion
treatment liquid, and an organic anticorrosive primer. Of those, a
chromium-free chemical conversion treatment liquid, an organic
anticorrosive primer, or the like is preferred from the viewpoint
of an environmentally friendly anticorrosive film.
[0021] In the present invention, the hydrophilic film is preferably
formed on the entirety or part of the surface of the fin substrate,
and the crosslinked hydrophobic film is preferably formed on the
entirety or part of the surface of the hydrophilic film. Thus, in
the heat exchange fin, the crosslinked hydrophobic film is
preferably formed on part of its surface in a nonuniform and
spotted manner, or the crosslinked hydrophobic film and the
hydrophilic film desirably cooperate with each other to form a
sea-island structure in which the cross-linked hydrophobic film
forms a sea portion and the hydrophilic film forms an island
portion. When the crosslinked hydrophobic film having a frost
formation-suppressing effect and the hydrophilic film are formed on
the surface of the fin substrate as described above, frost
formation at the time of heater operation can be prevented to the
extent possible by an excellent frost formation-suppressing effect
and frost formation suppression-maintaining effect exhibited by the
crosslinked hydrophobic film, and under such a condition that
condensation is liable to occur on a fin surface, a water droplet
of produced condensed water can be quickly removed by bringing the
water droplet into contact with the hydrophilic film by virtue of
the condensed water-removing effect of the hydrophilic film.
[0022] Here, a method of forming the crosslinked hydrophobic film
having a frost formation-suppressing effect on the entirety or part
of the surface of the fin substrate, preferably the entirety or
part of the surface of the hydrophilic film formed on the surface
of the fin substrate is not particularly limited. For example, as a
method of forming the crosslinked hydrophobic film on the same
surface as a spot pattern, there are given a method involving
adding a silicone-based hydrophobic agent to a hydrophobic coating
material and splashing part of the mixture at the time of the
formation of the cross-linked hydrophobic film to provide a spot
pattern, a method involving painting the surface with the
hydrophobic coating material in a thin-film manner through the use
of a spray upon its application to form a painted portion and an
unpainted portion, a method involving forming irregular portions on
the surface of the fin substrate (roughened surface) or the surface
of the hydrophilic film (coating film surface) on which the
crosslinked hydrophobic film is to be formed, forming the
crosslinked hydrophobic film in a recessed portion of the irregular
portions, and controlling the thickness of the crosslinked
hydrophobic film to cause the head of a protruded portion of the
irregular portions to appear from the crosslinked hydrophobic film,
and a method involving painting the surface of the fin substrate
(roughened surface) or the surface of the hydrophilic film (coating
film surface) on which the crosslinked hydrophobic film is to be
formed with a water-soluble resin or the like so that a spot
pattern may be obtained, then painting the painted surface with the
hydrophobic coating material, and then performing water washing,
acid washing, or alkali washing to remove the crosslinked
hydrophobic film formed on the water-soluble resin to form the
crosslinked hydrophobic film into a spot pattern.
[0023] In the present invention, after the crosslinked hydrophobic
film having a frost formation-suppressing effect has been formed on
the entirety or part of the surface of the fin substrate, the
crosslinked hydrophobic film is subjected to a post-treatment with
water, an acid solution, or an alkaline solution, and hence
hydrophilicity can be expressed, the frost formation at the time of
the heater operation can be prevented to the extent possible by an
excellent frost formation-suppressing effect and frost formation
suppression-maintaining effect, and under such a condition that
condensation is liable to occur on the fin surface, a water droplet
of condensed water easily flows and the water droplet can be
quickly removed.
[0024] Although the post-treatment with water for the expression of
the hydrophilicity is not particularly limited, the heat exchange
fin after the formation of the crosslinked hydrophobic film is
subjected to water washing with, for example, tap water, industrial
water, or ion-exchanged water through immersion or spraying under
the conditions of preferably normal temperature to 100.degree. C.
and 5 sec to 3 hr, more preferably 40 to 100.degree. C. and 10 sec
to 1 hr. In addition, although the post-treatment with the acid
solution for the expression of the hydrophilicity is not
particularly limited, the heat exchange fin after the formation of
the crosslinked hydrophobic film is subjected to washing through
immersion or spraying under the conditions of preferably normal
temperature to 100.degree. C. and 5 sec to 3 hr, more preferably 40
to 100.degree. C. and 10 sec to 1 hr. Although the acid solution is
not particularly limited, an aqueous solution of an inorganic acid
such as sulfuric acid, nitric acid, phosphoric acid, or boric acid,
or an organic acid such as acetic acid, citric acid, or oxalic acid
is used. In addition, although the post-treatment with the alkaline
solution for the expression of the hydrophilicity is not
particularly limited, the heat exchange fin after the formation of
the crosslinked hydrophobic film is subjected to washing through
immersion or spraying under the conditions of preferably normal
temperature to 100.degree. C. and 5 sec to 3 hr, more preferably
40.degree. C. to 100.degree. C. and 10 sec to 1 hr. Although the
alkaline solution is not particularly limited, an aqueous solution
of, for example, sodium hydroxide, sodium hydrogen carbonate, or
sodium silicate is permitted. It should be noted that after the
washing with the acid solution or the alkaline solution, water
washing may be performed after neutralization with the alkaline
solution or the acid solution.
[0025] Here, the water contact angle of the crosslinked hydrophobic
film having a frost formation-suppressing effect is preferably
100.degree. or more, more preferably 105.degree. or more, and its
thickness is typically 0.05 to 5.0 .mu.m, preferably 0.1 to 4.0
.mu.m, more preferably 0.2 to 2.0 .mu.m. The water contact angle of
the crosslinked hydrophobic film is desirably as large as
possible.
[0026] However, when the water contact angle of the crosslinked
hydrophobic film is less than 100.degree., there arises a problem
in that the frost formation-suppressing effect reduces. In
addition, when the thickness of the crosslinked hydrophobic film is
less than 0.05 .mu.m, for example, the following problem arises.
Variations in frost formation suppression and hydrophilicity
between lots enlarge, and the deterioration of the frost formation
suppression and hydrophilicity-maintaining property over time
enlarges. In contrast, when the thickness exceeds 5.0 .mu.m,
neither additional frost formation suppression nor an additional
improvement in hydrophilicity can be expected. In addition, for
example, the following problem arises. The burn of the film due to
heat upon brazing of a copper tube for a refrigerant to the fin
material becomes rather conspicuous and a cost increases with
increasing thickness.
[0027] In the present invention, the crosslinked hydrophobic film
that exhibits a frost formation-suppressing effect is formed by
applying the aqueous hydrophobic coating composition, and as the
aqueous hydrophobic coating composition to be used for the purpose,
there can be given an aqueous hydrophobic coating composition
containing the resin (A) having at least one kind of fluorine
atom-containing group selected from the group consisting of a
perfluoroalkyl group and a perfluoroalkenyl group, the quaternary
ammonium salt group-containing modified epoxy resin (B), and the
amino resin (C) from the viewpoint of long-term maintenance of
frost formation suppression. It should be noted that in the
following description, the resin (A) having at least one kind of
fluorine atom-containing group selected from the group consisting
of a perfluoroalkyl group and a perfluoroalkenyl group is sometimes
referred to as "resin (A) having a fluorine atom-containing
group."
[0028] <Resin (A) Having Fluorine Atom-Containing Group>
[0029] In the aqueous hydrophobic coating material, a known resin
can be used as the resin (A) having a fluorine atom-containing
group as long as the resin has a perfluoroalkyl group and/or a
perfluoroalkenyl group, and a resin dispersed or dissolved in water
or a medium using water as a main component (hereinafter referred
to as "aqueous medium") can be used. Such resin (A) having a
fluorine atom-containing group is preferably, for example, a resin
obtained by subjecting a polymerizable unsaturated monomer (a-1)
having at least one kind of fluorine atom-containing group selected
from the group consisting of a perfluoroalkyl group and a
perfluoroalkenyl group (hereinafter sometimes described as the
"polymerizable unsaturated monomer (a-1) having a fluorine
atom-containing group") of a structure represented by the following
general formula (I) and any other polymerizable unsaturated monomer
(a-2) to a copolymerization reaction. A method of performing the
polymerization reaction can be selected from known polymerization
methods, and examples thereof can include bulk polymerization,
solution polymerization, emulsion polymerization, suspension
polymerization, and dispersion polymerization. Of those, emulsion
polymerization is preferred from the viewpoint of, for example, the
efficiency with which the resin dispersed or dissolved in the
aqueous medium is produced.
##STR00001##
[0030] (In the formula, Rf represents a linear or branched
perfluoroalkyl group or perfluoroalkenyl group having 1 to 21
carbon atoms. R represents a hydrogen atom, a halogen atom, or a
methyl group. X represents an oxygen atom or an imino group. Y
represents a divalent organic group having 1 to 20 carbon atoms
that may contain an oxygen atom, a sulfur atom, a nitrogen atom, or
a phosphorus atom.)
[0031] The fluorine atom-containing group is preferably a
perfluoroalkyl group, and examples of the perfluoroalkyl group
include --CF.sub.3, --CF.sub.2CF.sub.3, --CF.sub.2CF.sub.2CF.sub.3,
--CF(CF.sub.3).sub.2, --CF.sub.2CF.sub.2CF.sub.2CF.sub.3,
--CF.sub.2CF(CF.sub.3).sub.2, --C(CF.sub.3).sub.3,
--(CF.sub.2).sub.4CF.sub.3, --(CF.sub.2).sub.2CF (CF.sub.3).sub.2,
--CF.sub.2C(CF.sub.3).sub.3,
--CF(CF.sub.3)CF.sub.2CF.sub.2CF.sub.3, --(CF.sub.2).sub.5CF.sub.3,
--(CF.sub.2).sub.3CF (CF.sub.3).sub.2, --(CF.sub.2).sub.4CF
(CF.sub.3).sub.2, --(CF.sub.2).sub.7CF.sub.3,
--(CF.sub.2).sub.5CF(CF.sub.3).sub.2,
--(CF.sub.2).sub.6CF(CF.sub.3).sub.2, and
--(CF.sub.2).sub.9CF.sub.3. The perfluoroalkyl group has 1 to 21
carbon atoms, preferably 2 to 20 carbon atoms, more preferably 4 to
16 carbon atoms.
[0032] The emulsion polymerization of the polymerizable unsaturated
monomer (a-1) having a fluorine atom-containing group can be
performed by a known method involving subjecting a mixture of the
monomer (a-1) and the other polymerizable unsaturated monomer (a-2)
to emulsion polymerization with an emulsifier and a polymerization
initiator in the aqueous medium. It should be noted that in the
emulsion polymerization, a hydrophilic or hydrophobic organic
solvent may be used as required.
[0033] A conventionally known emulsifier can be used as the
emulsifier, and examples thereof include an anionic surfactant, a
nonionic surfactant, an amphoteric surfactant, and a combination
thereof. A compound having a fluorine atom of, for example, a
fluorinated alkyl group bonded thereto may be used as the
surfactant as required.
[0034] A conventionally known polymerization initiator can be used
as the polymerization initiator, and examples thereof include:
persulfates such as ammoniumpersulfate (APS), potassiumpersulfate,
and sodium persulfate; and oil-soluble polymerization initiators
such as diisopropyl peroxydicarbonate (IPP), benzoyl peroxide,
dibutyl peroxide, and azobisisobutyronitrile (AIBN).
[0035] In addition, a chain transfer agent may be used in the
emulsion polymerization reaction, and examples of the chain
transfer agent include: malonic acid diesters such as diethyl
malonate (MDE) and dimethyl malonate; acetic acid esters such as
ethyl acetate and butyl acetate; alcohols such as methanol and
ethanol; mercaptans such as n-lauryl mercaptan and n-octyl
mercaptan; and an .alpha.-methylstyrene dimer.
[0036] An aqueous dispersion of the resin (A) having a fluorine
atom-containing group can be produced by performing the
polymerization reaction at a polymerization temperature of 20 to
150.degree. C. for a polymerization time of 0.1 to 100 hr. In the
aqueous dispersion, the resin (A) having a fluorine atom-containing
group is obtained as particles having an average particle diameter
of 10 to 500 nm, preferably 30 to 200 nm. Its solid content
concentration is desirably about 5 to 50 mass %.
[0037] Each of the particles of the resin (A) having a fluorine
atom-containing group may be of a monolayer structure or may be of
a multilayer structure including a core-shell structure. In
addition, the inside of each of the particles may be crosslinked
and those particles can be obtained by a known method in emulsion
polymerization.
[0038] A monomer having copolymerization reactivity to the
polymerizable unsaturated monomer (a-1) having a fluorine
atom-containing group can be used as the other polymerizable
unsaturated monomer (a-2) without any particular limitation.
Examples thereof can include: acrylic acid; methacrylic acid;
itaconic acid; itaconic anhydride; maleic anhydride; butadiene;
isoprene; chloroprene; a (meth)acrylic acid alkyl ester in which
the alkyl group has 1 to 20 carbon atoms; a (meth)acrylic acid
cyclohexyl ester; isobornyl (meth)acrylate; a (meth)acrylic acid
benzyl ester; polyethylene glycol di(meth)acrylate; aromatic
vinyl-based monomers such as styrene, .alpha.-methylstyrene, and
p-methylstyrene; hydroxyalkyl (meth)acrylates such as
2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate,
hydroxybutyl (meth)acrylate, hydroxyamyl (meth)acrylate, and
hydroxyhexyl (meth)acrylate; a vinyl alkyl ether in which the alkyl
group has 1 to 20 carbon atoms; a halogenated alkyl vinyl ether in
which the alkyl group has 1 to 20 carbon atoms; a vinyl alkyl
ketone in which the alkyl group has 1 to 20 carbon atoms; silyl
group-containing unsaturated monomers such as vinyltriethoxysilane
and .gamma.-(methacryloxypropyl)trimethoxysilane;
(meth)acrylamide-based monomers such as (meth)acrylamide,
N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide,
N-ethoxymethyl (meth)acrylamide, N-n-propoxymethyl
(meth)acrylamide, N-isopropoxymethyl (meth)acrylamide,
N-n-butoxymethyl (meth)acrylamide, N-sec-butoxymethyl
(meth)acrylamide, and N-tert-butoxymethyl (meth)acrylamide; vinyl
esters such as vinyl acetate and "VeoVa" (vinyl ester manufactured
by Shell); acrylonitrile; methacrylonitrile ethylene; and
butadiene. It should be noted that herein, the term "(meth)acrylic
acid" is a collective term for acrylic acid and methacrylic acid,
the term "(meth)acrylate" is a collective term for acrylate and
methacrylate, and the term "(meth)acrylamide" is a collective term
for acrylamide and methacrylamide.
[0039] A commercial product of the resin (A) having a fluorine
atom-containing group dissolved or dispersed in an aqueous medium
is, for example, UNIDYNE TG-652, UNIDYNE TG-664, UNIDYNE TG-410,
UNIDYNE TG-5521 UNIDYNE TG-5601, UNIDYNE TG-8711, UNIDYNE TG-470B,
UNIDYNE TG-500S, UNIDYNE TG-580, UNIDYNE TG-581, or UNIDYNE TG-658
(all of which are manufactured by DAIKIN, trade name), SWK-601
(manufactured by SEIMI CHEMICAL), FS6810 (manufactured by Fluoro
Technology), or NK GUARD SR-108 (manufactured by NICCA CHEMICAL
CO., LTD).
[0040] Instead of the method based on the copolymerization reaction
between the polymerizable unsaturated monomer (a-1) having a
fluorine atom-containing group and the other polymerizable
unsaturated monomer (a-2), the production of the resin (A) having a
fluorine atom-containing group can be similarly performed by a
polymerization reaction between the polymerizable unsaturated
monomers involving using a perfluoroalkyl group-containing radical
generator as a polymerization initiator, and examples of the
polymerization initiator can include fluorine-containing organic
peroxides described in JP 2010-195937 A.
[0041] <Quaternary Ammonium Salt Group-Containing Modified Epoxy
Resin (B)>
[0042] The aqueous hydrophobic coating material contains the
quaternary ammonium salt group-containing modified epoxy resin (B)
to be described below from the viewpoints of the processability,
adhesiveness, moisture resistance, and corrosion resistance of a
coating film to be obtained.
[0043] The modified epoxy resin (B) can be produced by subjecting a
mixture containing an epoxy resin (b-1), a carboxyl
group-containing acrylic resin (b-2), and an amine compound (b-3)
to a reaction. In the reaction, a reaction for producing a
quaternary ammonium salt group, and an esterification reaction
between an epoxy group in the epoxy resin and a carboxyl group in
the carboxyl group-containing acrylic resin progress to produce the
quaternary ammonium salt group-containing modified epoxy resin (B).
In addition, in the reaction, the epoxy group of the epoxy resin
(b-1) opens to produce a hydroxyl group. Thus, the quaternary
ammonium salt group-containing modified epoxy resin (B) has a
hydroxyl group, which is reactive with the amino resin (C) to be
described later.
[0044] A bisphenol-type epoxy resin is preferred as the epoxy resin
(b-1) from the viewpoints of adhesiveness and corrosion resistance.
The bisphenol-type epoxy resin is a resin obtained by a reaction
between a bisphenol compound and an epihalohydrin such as
epichlorhydrin.
[0045] Examples of the bisphenol compound can include
bis(4-hydroxyphenyl)-2,2-propane (bisphenol A),
4,4-dihydroxybenzophenone, bis(4-hydroxyphenyl)methane (bisphenol
F), and 4,4-dihydroxydiphenyl sulfone (bisphenol S). Of those
bisphenol-type epoxy resins (b-1), a bisphenol A-type epoxy resin
is preferably used from the viewpoint of corrosion resistance.
[0046] From the viewpoints of, for example, the dispersion
stability in an aqueous medium and the processability and hygiene
of the coating film to be obtained, it is suitable to use the
bisphenol-type epoxy resin (b-1) having a number-average molecular
weight in the range of 4,000 to 30,000, preferably 5,000 to 30,000,
and having an epoxy equivalent of 2,000 to 10,000, preferably 2,500
to 10,000.
[0047] As a commercial product of a bisphenol A-type epoxy resin
that can be used as the bisphenol-type epoxy resin (b-1), there can
be given, for example, jER1010, jER1256B40, and jER1256
manufactured by Japan Epoxy Resins Co. Ltd.
[0048] In addition, the bisphenol A-type epoxy resin may be a
bisphenol A-type modified epoxy resin obtained by modifying a
bisphenol A-type epoxy resin with a dibasic acid. In this case, a
resin having a number-average molecular weight in the range of
2,000 to 8,000 and an epoxy equivalent in the range of 1,000 to
4,000 can be suitably used as the bisphenol A-type epoxy resin to
be caused to react with the dibasic acid. In addition, a compound
represented by a general formula "HOOC--(CH.sub.2).sub.n--COOH
(where n represents an integer of 1 to 12)," specifically, for
example, succinic acid, adipic acid, pimelic acid, azelaic acid,
sebacic acid, dodecanedioic acid, or hexahydrophthalic acid can be
used as the dibasic acid, and adipic acid can be particularly
suitably used.
[0049] The bisphenolA-type modified epoxy resin can be obtained by
subjecting a mixture of the bisphenol A-type epoxy resin and the
dibasic acid to a reaction in the presence of an esterification
catalyst such as tri-n-butylamine and an organic solvent at a
reaction temperature of 120 to 180.degree. C. for a reaction time
of about 1 to 4 hr.
[0050] The carboxyl group-containing acrylic resin (b-2) to be used
in the production of the quaternary ammonium salt group-containing
modified epoxy resin (B) can be produced by subjecting a mixture
containing a carboxyl group-containing polymerizable unsaturated
monomer and any other polymerizable unsaturated monomer to a
copolymerization reaction with, for example, a radical
polymerization initiator through heating in an organic solvent at
80 to 150.degree. C. for 1 to 10 hr.
[0051] As the other polymerizable unsaturated monomer that can be
used in the production of the carboxyl group-containing acrylic
resin (b-2), there can be given the other polymerizable unsaturated
monomer (a-2) described for the resin (A) having a fluorine
atom-containing group.
[0052] As the polymerization initiator, for example, an organic
peroxide-based or azo-based polymerization initiator is used.
Examples of the organic peroxide-based polymerization initiator
include benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate,
di-t-butyl peroxide, t-butyl peroxybenzoate, and t-amyl
peroxy-2-ethylhexanoate, and examples of the azo-based
polymerization initiator include azobisisobutyronitrile and
azobisdimethylvaleronitrile.
[0053] In the copolymerization reaction, a chain transfer agent may
be used, and examples thereof include known agents such as an
.alpha.-methylstyrene dimer and a mercaptan compound.
[0054] The carboxyl group-containing acrylic resin (b-2) has a
weight-average molecular weight in the range of preferably 5,000 to
100,000, more preferably 10,000 to 100,000 and a resin acid value
in the range of preferably 150 to 700 mgKOH/g, more preferably 200
to 500 mgKOH/g from the viewpoints of its stability in an aqueous
medium, and the processability and adhesiveness of the coating film
to be obtained.
[0055] The amine compound (b-3) is preferably a tertiary amine
compound such as triethylamine, dimethylethanolamine,
triethanolamine, monomethyldiethanolamine, or
N-methylmorpholine.
[0056] The quaternary ammonium salt group-containing modified epoxy
resin (B) can be produced by subjecting the mixture containing the
epoxy resin (b-1), the carboxyl group-containing acrylic resin
(b-2), and the amine compound (b-3) to a reaction through heating
in an organic solvent at 80 to 120.degree. C. for 0.5 to 8 hr.
[0057] A blending ratio between the epoxy resin (b-1) and the
carboxyl group-containing acrylic resin (b-2) in the reaction,
which has only to be appropriately selected depending on painting
workability and coating film performance, falls within the range of
preferably 10/90 to 95/5, more preferably 60/40 to 90/10 in terms
of a solid content mass ratio "resin (b-1)/resin (b-2)."
[0058] The usage of the amine compound (b-3) suitably falls within
the range of 1 to 10 mass % with reference to the total solid
content of the epoxy resin (b-1) and the carboxyl group-containing
acrylic resin (b-2) from the viewpoints of the moisture resistance
and corrosion resistance of the resultant film.
[0059] The quaternary ammonium salt group-containing modified epoxy
resin (B) obtained by the reaction has an acid value in the range
of preferably 20 to 120 mgKOH/g, more preferably 30 to 100 mgKOH/g
and a weight-average molecular weight in the range of preferably
1,000 to 40,000, more preferably 2,000 to 15,000 from the
viewpoints of its stability in an aqueous medium, and the
processability, adhesiveness, moisture resistance, and corrosion
resistance of the coating film to be obtained.
[0060] It should be noted that the weight-average molecular weight
in the description is a value obtained by converting a retention
time (retention volume) measured with tetrahydrofuran as a solvent
by gel permeation chromatography with reference to the
weight-average molecular weight of a polystyrene. In addition, the
number-average molecular weight is a value determined from the
weight-average molecular weight by calculation.
[0061] "HLC8120GPC" (manufactured by Tosoh Corporation) was used as
a gel permeation chromatograph. Four columns, i.e., "TSKgel
G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel
G-2000HXL" (all of which were manufactured by Tosoh Corporation,
trade name) were used, and the measurement was performed under the
following conditions: mobile phase; tetrahydrofuran, measurement
temperature; 40.degree. C., flow rate; 1 ml/min, and detector;
RI.
[0062] The quanternary ammonium salt group-containing modified
epoxy resin (B) is neutralized and dispersed in an aqueous medium,
and a basic compound such as an amine or ammonia is suitably used
as a neutralizer to be used in the neutralization.
[0063] Typical examples of the amine include triethylamine,
triethanolamine, dimethylethanolamine, diethylethanolamine, and
morpholine. Of those, triethylamine and dimethylethanolamine are
particularly suitable. For the neutralization of the quanternary
ammonium salt group-containing modified epoxy resin (B), it is
generally preferred that the neutralization be performed in the
range of 0.2 to 2.0 equivalents with respect to carboxyl groups in
the resin.
[0064] In the present invention, the amount of a quaternary
ammonium salt group formed at the time of the esterification
reaction and by the neutralization (the number of moles of the
quaternary ammonium salt group contained per 1 g of the resin)
preferably falls within the range of 3.0.times.10.sup.-4 mol/g or
less, preferably within the range of 0.6.times.10.sup.-4 to
3.0.times.10.sup.-4 mol/g, more preferably within the range of
0.8.times.10.sup.-4 to 2.5.times.10.sup.-4 mol/g from the
viewpoints of the adhesiveness, the moisture resistance, and the
corrosion resistance.
[0065] Here, the measurement of the quaternary ammonium salt group
amount is performed as described below. A titration reaction is
performed by dropping, to a sample solution obtained by dissolving
a sample after the initiation of the reaction in a solvent, an
indicator solution obtained by dissolving an indicator having a
sulfonic group and a hydroxyl group as functional groups in a
solvent. For each of the first stage of the titration reaction
where the indicator and a quaternary ammonium salt of an epoxy
compound react with each other to form an indicator in which both a
sulfonic group and a hydroxyl group have been simultaneously
ionized, and a carboxylic acid, and the second stage of the
titration reaction where the indicator and the ionized indicator
react with each other to form an indicator in which only a sulfonic
group has been ionized, a relationship between a titer and an
electric conductivity is plotted. A titer t.sub.1 in the first
stage is determined from a titer at the point of intersection
between a straight line connecting the plots in the first stage and
a straight line connecting the plots in the second stage, and then
the amount (mol/g) of the quaternary ammonium salt in 1 g of the
sample in terms of a solid content is determined from the following
equation (1).
Quaternary ammonium salt amount (mol/g)=t.sub.1
(ml).times.2.times.indicator concentration
(mol/l).times.(1/1,000).times.{100/(sample (g).times.solid content
(%))} Equation (1)
[0066] It should be noted that an aqueous medium in which the
quaternary ammonium salt group-containing modified epoxy resin (B)
is dispersed may be water alone or may be a mixture of water and an
organic solvent. Any one of the conventionally known solvents can
be used as the organic solvent as long as the stability of the
quaternary ammonium salt group-containing modified epoxy resin (B)
in the aqueous medium is not impaired.
[0067] <Amino Resin (C)>
[0068] Examples of the amino resin (C) in the aqueous hydrophobic
coating material include a melamine resin, a urea resin, and a
benzoguanamine resin. Of those, a melamine resin is preferred from
the viewpoints of the processability and the adhesiveness.
[0069] Examples of the melamine resin include a partially
etherified or fully etherified melamine resin obtained by
etherifying part or all of the methylol groups of methylolated
melamine with a monohydric alcohol having 1 to 8 carbon atoms such
as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl
alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, or
2-ethylhexanol.
[0070] As such resin, there can be used one in which the methylol
groups are fully etherified or one in which the methylol groups are
partially etherified and methylol groups and imino groups remain.
Examples thereof can include alkyl-etherified melamines such as
methyl-etherified melamine, ethyl-etherified melamine, and
butyl-etherified melamine. One kind of these malamines may be used
alone, or two or more kinds thereof may be used in combination as
required. Of those, a methyl-etherified melamine resin in which at
least part of the methylol groups are methyl-etherified is
suitable.
[0071] Commercial products of the melamine resin satisfying such
conditions are commercially available under, for example, the
following trade names: "CYMEL 202," "CYMEL 232," "CYMEL 235,"
"CYMEL 238," "CYMEL 254," "CYMEL 266," "CYMEL 267," "CYMEL 272,"
"CYMEL 285," "CYMEL 301," "CYMEL 303," "CYMEL 325," "CYMEL 327,"
"CYMEL 350," "CYMEL 370," "CYMEL 701," "CYMEL 703," "CYMEL 736,"
"CYMEL 738," "CYMEL 771," "CYMEL 1141," "CYMEL 1156," "CYMEL 1158,"
"MYCOAT 212," "MYCOAT 715," and "MYCOAT 776" (all of which are
manufactured by Nihon Cytec Industries Inc.); "U-VAN 120," "U-VAN
20HS," "U-VAN 2021," "U-VAN 2028," and "U-VAN 2061" (all of which
are manufactured by Mitsui Chemicals, Inc.); and "Melan 522"
(manufactured by Hitachi Chemical Co., Ltd.).
[0072] It should be noted that a blending ratio between the
quaternary ammonium salt group-containing modified epoxy resin (B)
and the amino resin (C) falls within the range of preferably 95/5
to 50/50, particularly preferably 93/7 to 60/40 in terms of a solid
content mass ratio "quaternary ammonium salt group-containing
modified epoxy resin (B)/amino resin (C)." When the amount of the
amino resin (C) is excessively small, sufficient curability is not
obtained. When the amount is excessively large, the processability
of an aluminum fin material may reduce.
[0073] The content of the resin (A) having a fluorine
atom-containing group in the aqueous hydrophobic coating
composition is 1 to 30 parts by mass, preferably 3 to 25 parts by
mass, more preferably 10 to 22 parts by mass in terms of a solid
content with respect to 100 parts by mass of the total of the solid
contents of the quaternary ammonium salt group-containing modified
epoxy resin (B) and the amino resin (C) from the viewpoints of
frost formation suppression, the corrosion resistance, and coating
stability.
[0074] It should be noted that additives such as a basic compound,
a crosslinking agent other than the amino resin (C) (such as a
blocked polyisocyanate), colloidal silica, an antibacterial agent,
a coloring pigment, a rust preventive pigment known per se (such as
a chromate-based, lead-based, or molybdic acid-based pigment), and
a rust preventive agent (such as: a phenolic carboxylic acid, e.g.,
tannic acid or gallic acid and a salt thereof; an organic
phosphoric acid, e.g., phytic acid or phosphinic acid; a metal
biphosphate; or a nitrite), and an aqueous medium can be added to
the aqueous hydrophobic coating composition in the present
invention in addition to the resin (A) having a fluorine
atom-containing group, the quanternary ammonium salt
group-containing modified epoxy resin (B), and the amino resin (C)
as required.
[0075] The aqueous medium may be water or may be a mixed solvent of
water and a small amount of an organic solvent or any one of the
basic compounds such as amines and ammonia. The content of water in
the mixed solvent is typically 80 mass % or more.
[0076] In addition, in the present invention, the hydrophilic film
exhibiting a condensed water-removing effect may be formed by
applying a hydrophilic coating material. Examples of the
hydrophilic coating material to be used for the purpose can
include: inorganic coating materials such as water glass-based,
silica-based, and boehmite-based coating materials; an organic
hydrophilic coating material containing a water-soluble acrylic
resin, a water-soluble cellulose resin, a water-soluble amino
resin, a polyvinyl alcohol, or the like; and an organic-inorganic
composite hydrophilic coating material containing an inorganic
material and an organic resin.
[0077] A known coating material can be used as the organic
hydrophilic coating material and examples thereof can include the
following organic hydrophilic coating compositions (E):
[0078] (1) an organic hydrophilic coating material containing a
polyvinyl alcohol having a saponification degree of 87% or more and
a neutralized resin obtained by the formation of a salt of at least
part of the carboxyl groups of a high-acid value acrylic resin
having a resin acid value of 300 mgKOH/g or more with a basic
compound that does not have a boiling point of less than
180.degree. C. and does not decompose at less than 180.degree. C.;
and
[0079] (2) an organic hydrophilic coating material containing a
polyvinyl alcohol-based resin and a polyethylene glycol-based resin
as main components, and containing a nitric acid compound having a
monovalent or divalent element (see JP 2002-275407 A).
[0080] In addition, in the present invention, the hydrophilic film
exhibiting a condensed water-removing effect may be formed by
applying a flux to be used in the step of brazing the fin. Examples
of the flux can include fluoride-based fluxes such as KAlF.sub.4,
K.sub.2AlF.sub.5.H.sub.2O, a complex compound of KAlF.sub.4 and
K.sub.3AlF.sub.6, KZnF.sub.3, K.sub.2SiF.sub.6, Li.sub.3AlF.sub.6,
and CsAlF.sub.4. One kind or more of those fluxes are used as a
mixture.
[0081] The application of the hydrophobic coating material, the
hydrophilic coating material, or the flux is performed by applying
means such as a roll coating method, a bar coating method, a
spraying method, an immersion method, or a spin coating method, and
is performed by a method involving using a precoated fin material
obtained by painting an aluminum material through the use of a roll
coater or the like, or a post-coating method involving applying
such coating material or flux to a heat exchanger constructed of an
aluminum fin material through spraying or immersion. At this time,
the hydrophobic coating material or the hydrophilic coating
material is appropriately diluted so as to have a predetermined
concentration before use.
[0082] In addition, the water contact angle of the hydrophilic film
is preferably 40.degree. or less, more preferably 30.degree. or
less, and its thickness is typically 0.1 to 200 .mu.m, preferably
0.2 to 100 .mu.m, more preferably 0.5 to 100 .mu.m. In addition,
when the hydrophilic film is a film formed in the brazing step, its
water contact angle is preferably 40.degree. or less, more
preferably 30.degree. or less, and its thickness is typically 0.1
to 200 .mu.m or less, preferably 1 to 100 .mu.m, more preferably 5
to 100 .mu.m.
[0083] The water contact angle of the hydrophilic film is desirably
as small as possible. However, when the water contact angle of the
hydrophilic film is more than 40.degree., a problem in that
condensed water hardly flows arises. In addition, when the
thickness of the hydrophilic film is less than 0.1 .mu.m, as in the
case of the crosslinked hydrophobic film, for example, the
following problem arises. Variations in frost formation suppression
and hydrophilicity between lots enlarge, and the deterioration of
the frost formation suppression and hydrophilicity-maintaining
property over time enlarges. In contrast, when the thickness
exceeds 200 .mu.m, neither additional frost formation suppression
nor an additional improvement in hydrophilicity can be expected. In
addition, for example, the following problem arises. A cost
increases with increasing thickness.
[0084] <Method of Forming Films for Heat Exchanger Fin>
[0085] (1) Case of Precoated Fin
[0086] A method of applying the anticorrosive film, the crosslinked
hydrophobic film, and the hydrophilic film on the surfaces of
various hard materials is not particularly limited. For example, in
the case of a precoated fin, a method involving using a generally
used roll coater, a bar coating method, or a spray method can be
adopted.
[0087] For example, when the crosslinked hydrophobic film is formed
on the surface of the fin substrate made of an aluminum plate
material for heat exchangers with the aqueous hydrophobic coating
composition, first, the aqueous hydrophobic coating composition is
applied to the aluminum material with a roller coater or the like,
and then the resultant is subjected to heating with, for example, a
floater oven under high-temperature ventilation, preferably heating
under a high-temperature ventilation of 10 to 30 m/min at a high
temperature of 60 to 300.degree. C. for 2 sec to 30 min.
[0088] In addition, when the crosslinked hydrophobic film is formed
after the formation of the hydrophilic film, the hydrophilic
treatment agent is applied to the surface of the fin substrate made
of an aluminum plate material for heat exchangers, then the
resultant is subjected to heating with, for example, a floater oven
under high-temperature ventilation, preferably heating under a
high-temperature ventilation of 10 to 30 m/min at a high
temperature of 60 to 300.degree. C. for 2 sec to 30 min, then the
aqueous hydrophobic coating composition is applied to the heated
product, and then the resultant is subjected to heating with, for
example, a floater oven under high-temperature ventilation,
preferably heating under a high-temperature ventilation of 10 to 30
m/min at a high temperature of 60 to 300.degree. C. for 2 sec to 30
min.
[0089] (2) Case of Post-Coating Painting
[0090] With regard to a method of applying the anticorrosive film,
the crosslinked hydrophobic film, and the hydrophilic film to
various surfaces, in the heat exchanger using an aluminum fin
material, the hydrophilic film, the anticorrosive film, and the
crosslinked hydrophobic film are formed by post-coating.
[0091] When the heat exchanger using the heat exchange fin made of
an aluminum plate material is formed of, for example, a heat
exchanger obtained by brazing a flat flow channel tube and a
corrugated fin, the hydrophilic film and the crosslinked
hydrophobic film, or the hydrophilic film, the anticorrosive film,
and the crosslinked hydrophobic film are formed in the heat
exchanger obtained by brazing the flat flow channel tube and the
corrugated fin by post-coating. In this case, the hydrophilic film
is formed by applying a flux to be used at the time of the brazing
by a spraying method, an immersion method, or the like, and the
anticorrosive film and the crosslinked hydrophobic film are each
formed by treating and applying the anticorrosive treatment liquid
or the aqueous hydrophobic coating material by the immersion
method, the spraying method, or the like, and then heating the
liquid or coating material at 60 to 300.degree. C. for 2 sec to 30
min.
[0092] For example, when the flat flow channel tube and the
corrugated fin are brazed with a fluoride-based flux, the following
may be adopted. A flux slurry is applied with a shower, a spray, a
brush, or the like and dried, and is then heated at 590 to
610.degree. C. for 3 to 10 min to form an inorganic hydrophilic
film on the flat flow channel tube and/or the corrugated fin. After
the film has been cooled, post-coating with the aqueous hydrophobic
coating material is performed by the method.
[0093] Alternatively, the following may be adopted. The flux is
applied to perform brazing so that an inorganic hydrophilic film
may be formed on the flat flow channel tube and/or the corrugated
fin. After the film has been cooled, post-coating with the
anticorrosive coating material is performed by the method and then
post-coating with the aqueous hydrophobic coating material is
performed by the method.
[0094] In the heat exchange fin of the present invention, a ratio
between the crosslinked hydrophobic film and hydrophilic film
formed on its surface needs to be as described below. An area
occupied by the crosslinked hydrophobic film in a square area
measuring 10 mm by 10 mm at an arbitrary position on the surface of
the heat exchange fin is 10 to 90%, preferably 20 to 80%. When the
area occupied by the crosslinked hydrophobic film is less than 10%,
a problem in that the frost formation-suppressing effect becomes
insufficient arises. In contrast, when the area is more than 90%, a
problem in that the condensed water-removing effect becomes
insufficient arises.
Advantageous Effects of Invention
[0095] According to the heat exchanger of the present invention,
the crosslinked hydrophobic film and the hydrophilic film are
formed on the same surface of the heat exchange fin made of an
aluminum plate material, and an excellent frost
formation-suppressing effect exhibited by the crosslinked
hydrophobic film and an excellent condensed water-removing effect
exhibited by the hydrophilic film cooperate with each other, and
hence frost formation at the time of heater operation can be
prevented to the extent possible, and under such a condition that
condensation is liable to occur on a fin surface, a water droplet
of condensed water can be quickly removed by bringing the water
droplet into contact with the hydrophilic film, and as a result, a
favorable heat exchange function can be maintained without any
increase in ventilation resistance.
BRIEF DESCRIPTION OF DRAWINGS
[0096] FIG. 1 is a perspective explanatory diagram illustrating a
heat exchanger made of an aluminum alloy obtained in each of
Examples 5 to 12 and Comparative Examples 1 to 8.
DESCRIPTION OF EMBODIMENTS
[0097] Hereinafter, a preferred embodiment of the present invention
is specifically described on the basis of examples and comparative
examples.
Production Example of Aqueous Hydrophobic Coating Composition
[0098] In the following production examples, the term "part (s)"
refers to "part (s) by mass" and the term "%" refers to "mass
%."
(1) Production of Carboxyl Group-Containing Acrylic Resin (Ca) to
be Used in Production of Ammonium Salt Group-Containing Modified
Epoxy Resin (B)
Production Example 1
Solution of Carboxyl Group-Containing Acrylic Resin (ca-1)
[0099] 850 parts of n-butanol were heated to 100.degree. C. in a
stream of nitrogen, and then a monomer mixture and a polymerization
initiator "450 parts of methacrylic acid, 450 parts of styrene, 100
parts of ethyl acrylate, and 40 parts of t-butyl
peroxy-2-ethylhexanoate" were dropped therein over 3 hr. After the
dropping, the resultant mixture was aged for 1 hr. Next, a mixed
solution of 10 parts of t-butyl peroxy-2-ethylhexanoate and 100
parts of n-butanol was dropped to the aged product over 30 min, and
after the dropping, the resultant mixture was aged for 2 hr. Next,
933 parts of n-butanol and 400 parts of ethylene glycol monobutyl
ether were added to the aged product to provide a solution of a
carboxyl group-containing acrylic resin (ca-1) having a solid
content of about 30%. The resultant resin had a resin acid value of
300 mgKOH/g and a weight-average molecular weight of about
17,000.
Production Example 2
Solution of Carboxyl Group-Containing Acrylic Resin (Ca-2)
[0100] 1,400 parts of n-butanol were heated to 100.degree. C. in a
stream of nitrogen, and then a monomer mixture and a polymerization
initiator "670 parts of methacrylic acid, 250 parts of styrene, 80
parts of ethyl acrylate, and 50 parts of t-butyl
peroxy-2-ethylhexanoate" were dropped therein over 3 hr. After the
dropping, the resultant mixture was aged for 1 hr. Next, a mixed
solution of 10 parts of t-butyl peroxy-2-ethylhexanoate and 100
parts of n-butanol was dropped to the aged product over 30 min, and
after the dropping, the resultant mixture was aged for 2 hr. Next,
373 parts of n-butanol and 400 parts of ethylene glycol monobutyl
ether were added to the aged product to provide a solution of a
carboxyl group-containing acrylic resin (ca-2) having a solid
content of about 30%. The resultant resin had a resin acid value of
450 mgKOH/g and a weight-average molecular weight of about
14,000.
(2) Production of Ammonium Salt Group-Containing Modified Epoxy
Resin (ae)
Production Example 3
Aqueous Dispersion of Ammonium Salt Group-Containing Modified Epoxy
Resin (ae-1)
[0101] 513 parts of a jER828EL (manufactured by Japan Epoxy Resins
Co., Ltd., epoxy resin, epoxy equivalent: about 190, number-average
molecular weight: about 380), 287 parts of bisphenol A, 0.3 part of
tetramethylammonium chloride, and 89 parts of methyl isobutyl
ketone were loaded, and were then subjected to a reaction for about
4 hr while being heated to 140.degree. C. in a stream of nitrogen.
Thus, an epoxy resin solution was obtained. The resultant epoxy
resin had an epoxy equivalent of 3,700 and a number-average
molecular weight of about 17,000.
[0102] Next, 667 parts of the solution of the carboxyl
group-containing acrylic resin (ca-1) having a solid content of
about 30% obtained in Production Example 1 were charged into the
resultant epoxy resin solution, and were then uniformly dissolved
by heating to 90.degree. C. After that, 40 parts of deionized water
were dropped to the solution at the temperature over 30 min. Next,
30 parts of dimethylethanolamine were added to the mixture and then
the whole was subjected to a reaction by being stirred for 1 hr.
Further, 2,380 parts of deionized water were added to the resultant
over 1 hr to provide an aqueous dispersion of an ammonium salt
group-containing modified epoxy resin (ae-1) having a solid content
of about 25%. The resultant resin had a resin acid value of 48
mgKOH/g, a quaternary ammonium salt amount (based on the electric
conductivity titration method in the description) of
1.2.times.10.sup.-4 mol/g, and a weight-average molecular weight of
26,000.
Production Example 4
Aqueous Dispersion of Ammonium Salt Group-Containing Modified Epoxy
Resin (ae-2)
[0103] 519 parts of a jER828EL (manufactured by Japan Epoxy Resins
Co., Ltd., epoxy resin, epoxy equivalent: about 190, number-average
molecular weight: about 380), 281 parts of bisphenol A, 0.3 part of
tetramethylammonium chloride, and 89 parts of methyl isobutyl
ketone were loaded, and were then subjected to a reaction for about
4 hr while being heated to 140.degree. C. in a stream of nitrogen.
Thus, an epoxy resin solution was obtained. The resultant epoxy
resin had an epoxy equivalent of 2,800 and a number-average
molecular weight of about 12,000.
[0104] Next, 667 parts of the solution of the carboxyl
group-containing acrylic resin (ca-2) having a solid content of
about 30% obtained in Production Example 2 were charged into the
resultant epoxy resin solution, and were then uniformly dissolved
by heating to 90.degree. C. After that, 40 parts of deionized water
were dropped to the solution at the temperature over 30 min. Next,
53 parts of dimethylethanolamine were added to the mixture and then
the whole was subjected to a reaction by being stirred for 1 hr.
Further, 2,350 parts of deionized water were added to the resultant
over 1 hr to provide an aqueous dispersion of an ammonium salt
group-containing modified epoxy resin (ae-2) having a solid content
of about 25%. The resultant resin had a resin acid value of 75
mgKOH/g, a quaternary ammonium salt amount (result based on the
electric conductivity titration) of 1.8.times.10.sup.-4 mol/g, and
a weight-average molecular weight of 18,000.
(3) Production of Aqueous Hydrophobic Coating Composition (D)
Production Example 5
Aqueous Hydrophobic Coating Composition (D-1)
[0105] 10 parts (solid content) of a UNIDYNE TG-500S (*1 of Note
2), parts (solid content) of the quaternary ammonium salt
group-containing modified epoxy resin (ae-1) obtained in Production
Example 3, and 10 parts (solid content) of a MYCOAT 715 (*4 of Note
2) were added, and then deionized water was further added to the
mixture to adjust its solid content. Thus, an aqueous hydrophobic
coating composition (D-1) having a solid content of 10% was
obtained.
Production Examples 6 to 12
Aqueous Hydrophobic Coating Compositions (D-2) to (D-8)
[0106] Respective components were sufficiently stirred with a
stirring machine in accordance with formulation shown in each of
Table 1 and Table 2 below, and then deionized water was added to
the mixture to adjust its solid content. Thus, aqueous hydrophobic
coating compositions (D-2) to (D-8) each having a solid content of
10% were produced.
TABLE-US-00001 TABLE 1 Aqueous hydrophobic coating composition D-1
D-2 D-3 D-4 D-5 D-6 D-7 D-8 Resin (A) having fluorine UNIDYNE 10 --
-- -- -- 1 3 20 atom-containing group TG-500S(*1) UNIDYNE -- 10 --
10 -- -- -- -- TG-580(*2) UNIDYNE -- -- 10 -- 10 -- -- --
TG-581(*3) Quaternary ammonium salt ae-1 90 90 90 -- -- 90 90 90
group-containing modified ae-2 -- -- -- 90 90 -- -- -- epoxy resin
(B) Amino resin (C) MYCOAT 715(*4) 10 10 10 10 10 10 10 10 (Note 1)
The ratio of a blended content is represented in a "part(s) by
mass" unit in terms of a solid content. (Note 2) (*1)UNIDYNE
TG-500S: manufactured by DAIKIN INDUSTRIES, LTD, trade name, water
dispersion of fluorine-based resin, solid content: 30 mass %
(*2)UNIDYNE TG-580: manufactured by DAIKIN INDUSTRIES, LTD, trade
name, water dispersion of fluorine-based resin, solid content: 30
mass % (*3)UNIDYNE TG-581: manufactured by DAIKIN INDUSTRIES, LTD,
trade name, water dispersion of fluorine-based resin, solid
content: 30 mass % (*4)MYCOAT 715: Nihon Cytec Industries Inc.,
trade name, methyl-etherified melamine resin, solid content:
80%
Production Examples of Hydrophilic Coating Compositions (E)
Production Example 13
Polyvinyl Alcohol Aqueous Solution (e-1)
[0107] A DENKA POVAL K-05 (manufactured by DENKI KAGAKU KOGYO
KABUSHIKI KAISHA, saponification degree: 99%, polymerization
degree: 550) was dissolved in water to provide a polyvinyl alcohol
aqueous solution (e-1) having a solid content of 14%.
Production Example 14
Acrylic Resin Aqueous Solution
[0108] 80 parts of a "JULIMER AC10LP" (polyacrylic acid
manufactured by Nihon Junyaku Co., Ltd., weight-average molecular
weight: 25,000, acid value: 779 mgKOH/g) were dissolved in 535
parts of a 3% aqueous solution of n-butanol to provide an acrylic
resin aqueous solution (e-2) having a solid content of 13%.
Production Example 15
Acrylic Resin Aqueous Solution)
[0109] 80 parts of a "JULIMER AC10LHP" (polyacrylic acid
manufactured by Nihon Junyaku Co., Ltd., weight-average molecular
weight: 250,000, acid value: 779 mgKOH/g) were dissolved in 920
parts of a 3% aqueous solution of n-butanol to provide an acrylic
resin aqueous solution (e-3) having a solid content of 8%.
Production Example 16
Hydrophilic Coating Composition (E-2)
[0110] 385 parts of the acrylic resin aqueous solution (e-2) having
a solid content of 13% obtained in Production Example 14 were added
to 357 parts of the polyvinyl alcohol aqueous solution (e-1) having
a solid content of 14% obtained in Production Example 13. Further,
146 parts of a mixed solution (solution containing lithium
hydroxide monohydrate at a concentration of 10%) of 14.6 parts of
lithium hydroxide monohydrate (LiOH.H.sub.2O) and 131.4 parts of a
3% aqueous solution of n-butanol were added to the mixture so that
the neutralization degree of the carboxyl groups of the acrylic
resin became 0.6 equivalent, followed by mixing and stirring.
Further, 112 parts of a 3% aqueous solution of n-butanol were added
to the resultant, and then the contents were mixed and stirred so
as to be uniform. Thus, a hydrophilic coating composition (E-2)
having a solid content of 10% was obtained. Table 2 shows coating
formulation.
Production Example 17
Hydrophilic Coating Composition (E-3)
[0111] 385 parts of the acrylic resin aqueous solution (e-3) having
a solid content of 13% obtained in Production Example 15 were added
to 357 parts of the polyvinyl alcohol aqueous solution (e-1) having
a solid content of 14% obtained in Production Example 13. Further,
146 parts of a mixed solution (solution containing lithium
hydroxide monohydrate at a concentration of 10%) of 14.6 parts of
lithium hydroxide monohydrate (LiOH.H.sub.2O) and 131.4 parts of a
3% aqueous solution of n-butanol were added to the mixture so that
the neutralization degree of the carboxyl groups of the acrylic
resin became 0.6 equivalent, followed by mixing and stirring.
Further, 112 parts of a 3% aqueous solution of n-butanol were added
to the resultant, and then the contents were mixed and stirred so
as to be uniform. Thus, a hydrophilic coating composition (E-3)
having a solid content of 10% was obtained. Table 2 shows coating
formulation.
TABLE-US-00002 TABLE 2 Hydrophilic coating composition E-2 E-3
Polyvinyl alcohol aqueous solution (e-1) 50 50 Acrylic resin
aqueous solution (e-2) 50 -- Acrylic resin aqueous solution (e-3)
-- 50 Lithium hydroxide monohydrate (neutralization 0.6 0.6
equivalent) (Note) Contents blended in the components e-1 to e-3
are each represented in a "part (s) by mass" unit in terms of a
solid content.
Preparation of Comparative Hydrophobic Coating Composition
Comparative Production Example 1
Modified Epoxy Resin Free of Quaternary Ammonium Salt Group
[0112] 513 parts of a jER828EL (manufactured by Japan Epoxy Resins,
Co., Ltd., epoxy resin, epoxy equivalent: about 190, number-average
molecular weight: about 380), 287 parts of bisphenol A, 0.3 part of
tetramethylammonium chloride, and 89 parts of methyl isobutyl
ketone were loaded, and were then subjected to a reaction for about
4 hr while being heated to 140.degree. C. in a stream of nitrogen.
Thus, an epoxy resin solution was obtained. The resultant epoxy
resin had an epoxy equivalent of 3,700 and a number-average
molecular weight of about 17,000.
[0113] Next, 667 parts of the solution of the carboxyl
group-containing acrylic resin (ca-1) having a solid content of
about 30% obtained in Production Example 1 were charged into the
resultant epoxy resin solution, and were then uniformly dissolved
by heating to 90.degree. C. After that, 40 parts of deionized water
were dropped to the solution at the temperature over 30 min. Next,
0.2 part of tetramethylammonium chloride was added to the mixture
and then the whole was subjected to a reaction under stirring for 3
hr. Further, a mixture of 2,380 parts of deionized water and 23
parts of 25% ammonia water was added to the resultant over 1 hr to
provide an aqueous dispersion of a modified epoxy resin free of any
quaternary ammonium salt group having a solid content of about 25%.
The resultant resin had a resin acid value of 48 mgKOH/g and a
weight-average molecular weight of 24,000.
TABLE-US-00003 TABLE 3 Comparative hydrophobic coating composition
F-1 F-2 F-3 F-4 F-5 Resin (A) having fluorine UNIDYNE 10 -- -- --
10 atom-containing group TG-500S(*1) UNIDYNE -- 10 -- -- --
TG-580(*2) UNIDYNE -- -- 10 -- -- TG-581(*3) LUMIFLON -- -- -- 10
-- FE-2320(*5) Quaternary ammonium salt (ae-1) 90 90 90 90 --
group-containing modified epoxy resin (B) Modified epoxy resin free
of quaternary 90 ammonium salt group (*6) Amino resin (C) MYCOAT
715(*4) 0 0 0 10 10 (Remark 1) The ratio of a blended content is
represented in a "part(s) by mass" unit in terms of a solid
content. (Remark 2) (*1) to (*4)The resins are identical to those
of Table 1. (*5)LUMIFLON FE-2320: manufactured by ASAHI GLASS CO.,
LTD., trade name, an alternating copolymer of fluoroethylene and
vinyl ether (that does not have any perfluoroalkyl group) (*6): The
modified epoxy resin of Comparative Production Example 1 (free of
any quaternary ammonium salt group)
[0114] <Production of Heat Exchanger Using Precoated Fin
Material>
(Production of Anticorrosive Fin Substrates a and b for Precoated
Fin Materials)
[0115] In each of Examples 1 to 4, an aluminum plate material (JIS
A 1050) having a plate thickness of 100 .mu.m was used as an
aluminum fin material and then the aluminum plate material was
subjected to a degreasing treatment. After that, an anticorrosive
film was formed by painting each of both surfaces of the aluminum
plate material with a chromate-based treatment agent (treatment
agent a: manufactured by Nihon Parkerizing Co., Ltd., trade name
"ALCHROM 712") or an organic treatment agent (treatment agent b:
manufactured by KANSAI PAINT CO., LTD., trade name "Cosmer 9105")
as an anticorrosive treatment agent through the use of a roll
coater. Here, upon preparation of an anticorrosive fin substrate a
with the treatment agent a, the substrate was formed by: painting
each of both surfaces of the aluminum plate material with the
treatment agent a through the use of the roll coater so that the
amount of the agent became 20 mg/m.sup.2 in terms of a Cr amount;
and then drying the agent at a peak metal temperature (PMT) of
230.degree. C. for 15 sec. In addition, when the treatment agent b
was used, an anticorrosive fin substrate b was formed by: painting
each of both surfaces of the aluminum plate material with the
treatment agent b through the use of the roll coater so that the
thickness of the agent became 1.0 g/m.sup.2; and then drying the
agent at a PMT of 250.degree. C. for 10 sec.
[0116] (Formation of Hydrophilic Films E-1 to E-3 Each Using
Hydrophilic Coating Composition)
[0117] In each of Example 1 and Comparative Example 9, the top of
the anticorrosive film on the anticorrosive fin substrate a was
painted with a carboxymethylcellulose-based coating material E-1
(manufactured by Nippon Paint Co., Ltd., trade name "SURFALCOAT
160") by using a roll coater so that the coating material had a
thickness shown in Table 4. Next, the coating material was dried at
a PMT of 200.degree. C. for 10 sec to form a hydrophilic film. In
addition, in each of Examples 2 and 4, the top of the anticorrosive
film on the anticorrosive fin substrate a or b was painted with the
coating material E-1 or coating material E-2 shown in Table 2 in
the same manner as in the case of Example 1, and then the coating
material was dried at a PMT of 230.degree. C. for 10 sec.
[0118] (Formation of Crosslinked Hydrophobic Film Using Aqueous
Hydrophobic Coating Composition)
[0119] After the hydrophilic film E-1 had been formed on the
anticorrosive film a, in Example 1, the resultant was painted with
the coating material D-1 of the aqueous hydrophobic coating
composition shown in Table 1 by using a spray so that the coating
material had a thickness shown in Table 4, and in Comparative
Example 9, the resultant was painted with the comparative
hydrophobic coating composition F-1 shown in Table 3 by using a
spray so that the coating material had a thickness shown in Table
4. Next, the coating material was dried at a PMT of 220.degree. C.
for 10 sec to produce a precoated fin having a crosslinked
hydrophobic film on part of a fin substrate.
[0120] In Example 2, after the anticorrosive film a and the
hydrophilic film E-2 had been formed, the resultant was painted
with the coating material D-1 of the aqueous hydrophobic coating
composition shown in Table 1 by using a spray so that the coating
material had a thickness shown in Table 4, followed by drying under
the conditions of Example 1 to produce a precoated fin having a
crosslinked hydrophobic film on part of its surface as a heat
exchange fin of Example 2.
[0121] In each of Example 3 and Comparative Example 10, after the
anticorrosive film a had been formed, the resultant was painted
with the coating material D-2 of the aqueous hydrophobic coating
composition shown in Table 1 in Example 3, or the comparative
hydrophobic coating composition F-2 shown in Table 3 in Comparative
Example 10, by using a roll coater so that the coating material had
a thickness shown in Table 4, followed by drying under the
conditions of Example 1.
[0122] In Example 4, after the anticorrosive film b and the
hydrophilic film E-3 had been formed, the resultant was painted
with the coating material D-2 of the aqueous hydrophobic coating
composition shown in Table 1 by using a roll coater so that the
coating material had a thickness shown in Table 4, followed by
drying under the conditions of Example 1.
[0123] (Production of Heat Exchanger Using Precoated Fin)
[0124] The precoated fin of each of Examples 1 and 2 in which the
crosslinked hydrophobic film having a frost formation-suppressing
effect had been formed on part of the fin substrate was cut into a
piece measuring 500 by 25 by 0.1 mm and then subjected to press
working with 2 rows.times.12 rows of collar portions to provide a
heat exchange fin. The heat exchange fins were laminated so as to
coincide with the collar portions, and then a copper tube
(JIS-C1220, outer diameter: 7 mm, wall thickness: 0.3 mm) was
inserted into the collar portions of the formed laminate. Next, the
copper tube was expanded with a mandrel to join the collar portions
mechanically. Thus, a cross fin tube-type heat exchanger (having
external dimensions measuring 500 mm by 25 mm by 250 mm) of each of
Examples 1 and 2 including the heat exchange fin having the
crosslinked hydrophobic film on part of its surface was
produced.
[0125] In Example 3, a heat exchanger was produced in the same
manner as in Example 1 by using a precoated fin in which a
crosslinked hydrophobic film having a frost formation-suppressing
effect had been formed on a fin substrate. Next, a cross fin
tube-type heat exchanger of Example 3 including a heat exchange fin
having the crosslinked hydrophobic film on part of its surface was
produced in the same manner as in Example 1 by immersing the heat
exchanger in tap water at 40.degree. C. for 30 min and drying the
heat exchanger as a post-treatment.
[0126] In Example 4, a heat exchanger was produced in the same
manner as in Example 1 by using a precoated fin in which a
crosslinked hydrophobic film having a frost formation-suppressing
effect had been formed on a fin substrate. Next, a cross fin
tube-type heat exchanger of Example 4 including a heat exchange fin
having the crosslinked hydrophobic film on part of its surface was
produced in the same manner as in Example 1 by subjecting the heat
exchanger to spray washing with industrial water at 80.degree. C.
for 1 min and drying the heat exchanger as a post-treatment.
[0127] In Comparative Example 9, a heat exchanger was produced in
the same manner as in Example 1 by using a precoated fin in which a
hydrophobic film had been formed on part of a fin substrate.
[0128] In Comparative Example 10, a cross fin tube-type heat
exchanger was produced in the same manner as in Example 1 by using
a precoated fin in which a hydrophobic film had been formed on a
fin substrate. Next, a cross fin tube-type heat exchanger was
produced in the same manner as in Example 1 by subjecting the heat
exchanger to spray washing with tap water at 80.degree. C. for 1
min and drying the heat exchanger as a post-treatment.
Production of Heat Exchanger Using Corrugated Fin
Examples 5 to 12 and Comparative Examples 1 to 8
Heat Exchanger Using Corrugated Fin and Formation of Hydrophilic
Film with Flux
[0129] A heat exchanger using a corrugated fin is of a
parallel-flow heat exchange type constructed of a porous extruded
flat tube as a flat flow channel tube, the corrugated fin, and a
header pipe made of aluminum.
[0130] In each of Examples 5 to 8 and Comparative Examples 1 to 8,
the porous extruded flat tube (JIS A1050 alloy, width: 16 mm,
thickness: 0.93 mm, wall thickness: 0.35 mm) and the corrugated fin
formed of a clad brazing sheet (JIS A4343 alloy/JIS A3003 alloy/JIS
A4343 alloy, thickness: 0.9 mm, fin height: 7.9 mm, fin width: 16
mm) were laminated, and then the header pipe made of aluminum was
set at each of both ends of the laminate, followed by restriction
with a jig made of SUS. After that, a flux made of a complex
compound of KAlF.sub.4 and K.sub.3AlF.sub.6 was applied to the
laminate with a spray, and was then dried at 150.degree. C. for 5
min. The average application amount of the flux after the drying
was 5 g/m.sup.2 in the case of each of Examples 5 and 6, 15
g/m.sup.2 in the case of each of Examples 7 and 8, 3 g/m.sup.2 in
the case of each of Comparative Examples 1 and 2, and 9 g/m.sup.2
in the case of each of Comparative Examples 3 to 8.
[0131] Next, the resultant was subjected to a temperature increase
and heating in a mesh belt-type continuous furnace having an inert
atmosphere muffle replaced with an N.sub.2 gas, followed by brazing
at 600.degree. C. After the flat tube and the fin, and the flat
tube and the header pipe had been joined to each other by the
brazing, the resultant was cooled to normal temperature in a
continuous brazing furnace. After the brazing, a section of the fin
material was observed. As a result, it was found that a film formed
of the flux had irregularities, in each of Examples 5 and 6, a
thick portion had a thickness of 10 .mu.m and a thin portion had a
thickness of 0.5 .mu.m, in each of Examples 7 and 8, a thick
portion had a thickness of 35 .mu.m and a thin portion had a
thickness of 2 .mu.m, in each of Comparative Examples 1 and 2, a
thick portion had a thickness of 4 .mu.m and a thin portion had a
thickness of 0.4 .mu.m, and in each of Comparative Examples 3 to 8,
a thick portion had a thickness of 15 .mu.m and a thin portion had
a thickness of 1.2 .mu.m. The heat exchanger made of an aluminum
alloy after the brazing was washed with tap water and dried as a
pretreatment for the painting.
[0132] (Anticorrosive Treatment and Production of Heat Exchanger
Including Anticorrosive Fin Substrate c)
[0133] In each of Examples 5 and 6, and Comparative Examples 6 and
7, after the painting pretreatment, the heat exchanger to which the
corrugated fin (heat exchange fin) had been brazed was immersed in
a bath, which contained a 2% solution of an ALSURF 375 manufactured
by Nippon Paint Co., Ltd. warmed to 40.degree. C., for 1 min and
lifted. After that, the heat exchanger was sufficiently washed with
water and dried at 50.degree. C. for 1 min to produce a heat
exchanger including an anticorrosive fin substrate c.
[0134] In each of Examples 7 and 8, and Comparative Examples 1 to 5
and 8, no anticorrosive film was formed.
[0135] (Formation of Crosslinked Hydrophobic Film)
[0136] Next, in each of Examples 5 to 8, each of the coatings D-3
to D-6 of the aqueous hydrophobic coating compositions shown in
Table 1 was applied through immersion so as to have a thickness
shown in Table 4, and was then drained off, followed by drying in a
continuous drying furnace at 160.degree. C. for 30 min.
[0137] In addition, in each of Comparative Examples 1 to 7, each of
the coating material D-1 of the aqueous hydrophobic coating
composition shown in Table 1, and the aqueous hydrophobic coating
compositions F-1 to F-5 of Comparative Examples shown in Table 3
was applied through immersion so as to have a thickness shown in
Table 4, and was then drained off, followed by drying in a
continuous drying furnace at 160.degree. C. for 30 min.
[0138] In Comparative Example 8, the coating material of the
aqueous hydrophobic coating composition was not applied and a state
after the brazing was maintained.
[0139] (Post-Treatment)
[0140] Next, in Example 5, no post-treatment was performed, and in
Example 6, after having been immersed in a 1% solution of caustic
soda at 50.degree. C. for 30 sec and lifted, the heat exchanger was
sufficiently washed with tap water and dried as a post-treatment.
Further, in Example 7, the heat exchanger was washed with tap water
at 60.degree. C. for 30 min as a post-treatment. Further, in
Example 8, after having been immersed in a 1% solution of sulfuric
acid at 40.degree. C. for 30 sec and lifted, the heat exchanger was
sufficiently washed with tap water and dried as a post-treatment.
Thus, a parallel flow-type heat exchanger of each of Examples 5 to
8 including a heat exchange fin having a crosslinked hydrophobic
film on part of its surface was produced.
[0141] In each of Comparative Examples 3 and 7, after having been
immersed in tap water at 80.degree. C. for 1 min and lifted, the
heat exchanger was sufficiently washed with water and dried as a
post-treatment. In any other comparative example, no post-treatment
was performed. Thus, a parallel flow-type heat exchanger of each of
Comparative Examples 1 to 8 was produced.
Examples 9 and 10
Heat Exchanger Using Corrugated Fin and Formation of Hydrophilic
Film with Flux
[0142] In each of Examples 9 and 10, a porous extruded flat tube
(width: 16 mm, thickness: 1.93 mm, wall thickness: 0.35 mm)
obtained by adding 0.4% of Cu, 0.03% of Zr, and 0.1% of Ti to a JIS
A1050 alloy was used as a flat flow channel tube. The surface of
the flat flow channel tube was immersed in a solution obtained by
turning Si metal powder having an average particle diameter of 10
.mu.m or less, a mixed flux of K.sub.2AlF.sub.5.H.sub.2O and
KZnF.sub.3, and an acrylic resin as a binder into a slurry in an
industrial alcohol, and was then dried at 250.degree. C. for 3 min.
Formed on the surface after the drying was an Si/flux mixed film
containing the Si metal powder having an average application amount
of 4 g/m.sup.2, the flux having an average application amount of 10
g/m.sup.2, and the binder having an average application amount of 3
g/m.sup.2.
[0143] The porous extruded flat tube having the Si/flux mixed film
formed on its surface and a natural corrugated fin (thickness: 0.9
mm, fin height: 7.9 mm, fin width: 16 mm) obtained by adding 1.5%
of Zn to a JIS A3003 alloy were laminated, and then a header pipe
made of aluminum was set at each of both ends of the laminate,
followed by restriction with a jig made of SUS. After that, the
resultant was subjected to a temperature increase and heating in a
mesh belt-type continuous furnace having an inert atmosphere muffle
replaced with an N.sub.2 gas, followed by brazing at 595.degree. C.
After the flat tube and the fin, and the flat tube and the header
pipe had been joined to each other by the brazing, the resultant
was cooled to normal temperature in a continuous brazing furnace.
After the brazing, a section of the fin material was observed. As a
result, it was found that the Si/flux film of the flat flow channel
tube spread over the corrugated fin material, the fin material had
irregularities, and a thick portion had a thickness of 5 .mu.m and
a thin portion had a thickness of 0.5 .mu.m. The heat exchanger
made of an aluminum alloy after the brazing was washed with tap
water and dried as a pretreatment for the painting.
[0144] (Anticorrosive Treatment and Production of Heat Exchanger
Including Anticorrosive Fin Substrate c)
[0145] In each of Examples 9 and 10, after the painting
pretreatment, a heat exchanger including the anticorrosive fin
substrate c was produced in the same manner as in each of Examples
5 and 6 for forming an anticorrosive film.
[0146] (Formation of Crosslinked Hydrophobic Film)
[0147] Next, the heat exchanger of each of Examples 9 and 10 was
painted with the coating material D-7 of the aqueous hydrophobic
coating composition shown in Table 1 through immersion so that the
coating material had a thickness shown in Table 4, and then the
coating material was dried in a continuous drying furnace at
160.degree. C. for 30 min.
[0148] (Post-Treatment)
[0149] Next, in Example 9, no post-treatment was performed, and in
Example 10, after having been immersed in tap water at 80.degree.
C. for 30 sec and lifted, the heat exchanger was sufficiently
washed with tap water and dried as a post-treatment. Thus, a
parallel flow-type heat exchanger of each of Examples 9 and 10
including a heat exchange fin having a crosslinked hydrophobic film
on part of its surface was produced.
Examples 11 and 12
Heat Exchanger Using Corrugated Fin and Formation of Hydrophilic
Film with Flux
[0150] In each of Examples 11 and 12, a porous extruded flat tube
(width: 16 mm, thickness: 1.93 mm, wall thickness: 0.35 mm)
obtained by adding 0.40 of Cu, 0.03% of Zr, and 0.1% of Ti to a JIS
A1050 alloy was used as a flat flow channel tube. The surface of
the flat flow channel tube was immersed in a solution obtained by
turning Si metal powder having an average particle diameter of 10
.mu.m or less, a mixed flux of K.sub.2AlF.sub.6 and KZnF.sub.3, and
an acrylic resin as a binder into a slurry in an industrial
alcohol, and was then dried at 250.degree. C. for 3 min. Formed on
the surface after the drying was an Si/flux mixed film containing
the Si metal powder having an average application amount of 4
g/m.sup.2, the flux having an average application amount of 10
g/m.sup.2, and the binder having an average application amount of 3
g/m.sup.2.
[0151] The porous extruded flat tube having the Si/flux mixed film
formed on its surface and a natural corrugated fin (thickness: 0.9
mm, fin height: 7.9 mm, fin width: 16 mm) obtained by adding 1.5%
of Zn to a JIS A3003 alloy were laminated, and then a header pipe
made of aluminum was set at each of both ends of the laminate,
followed by restriction with a jig made of SUS. After that, a flux
made of a complex compound of KAlF.sub.4 and K.sub.3AlF.sub.6 was
applied to the laminate with a spray, and was then dried at
150.degree. C. for 5 min. The average application amount of the
flux after the drying was 7 g/m.sup.2.
[0152] Next, the resultant was subjected to a temperature increase
and heating in a mesh belt-type continuous furnace having an inert
atmosphere muffle replaced with an N.sub.2 gas, followed by brazing
at 595.degree. C. After the flat tube and the corrugated fin, and
the flat tube and the header pipe had been joined to each other by
the brazing, the resultant was cooled to normal temperature in a
continuous brazing furnace.
[0153] After the brazing, a section of the corrugated fin was
observed. As a result, it was found that the corrugated fin had
irregularities derived from the flux film, and a thick portion had
a thickness of 15 .mu.m and a thin portion had a thickness of 2
.mu.m. The heat exchanger made of an aluminum alloy after the
brazing was washed with tap water and dried as a pretreatment for
the painting.
[0154] (Anticorrosive Treatment)
[0155] In each of Examples 11 and 12, no anticorrosive film was
formed.
[0156] (Formation of Crosslinked Hydrophobic Film)
[0157] Next, the heat exchanger of each of Examples 11 and 12 was
painted with the coating material D-8 of the aqueous hydrophobic
coating composition shown in Table 1 through immersion so that the
coating material had a thickness shown in Table 4, and then the
coating material was dried in a continuous drying furnace at
160.degree. C. for 30 min.
[0158] (Post-Treatment)
[0159] Next, in Example 12, after having been immersed in
industrial water at normal temperature for 30 min and lifted, the
heat exchanger was sufficiently washed with tap water and dried as
a post-treatment. Thus, a parallel flow-type heat exchanger of each
of Examples 11 and 12 including a heat exchange fin having a
crosslinked hydrophobic film on part of its surface was
produced.
[0160] FIG. 1 illustrates the heat exchanger made of an aluminum
alloy obtained in each of Examples 5 to 12 and Comparative Examples
1 to 8 by joining a corrugated fin 5 and an extruded flat tube 4,
and the extruded flat tube 4 and a header pipe 3, to each other
through brazing, and then cooling the resultant to normal
temperature in a continuous brazing furnace. In FIG. 1, one of the
pair of header pipes 3 is provided with a heating
medium-introducing port 1 and the other is provided with a
discharge port 2.
[0161] It should be noted that in the following examples and
comparative examples, the measurement of the water contact angles
of a crosslinked hydrophobic film and a hydrophilic film, the
measurement of the area ratio of the crosslinked hydrophobic film,
and the confirmation of a frost formation-suppressing effect were
performed by the following methods.
[0162] (Measurement of Water Contact Angle)
[0163] In each of Examples and Comparative Examples, an aluminum
fin material measuring 7 cm by 15 cm was prepared for contact angle
measurement, and then the formation of an anticorrosive film, a
hydrophilic film, and a crosslinked hydrophobic film, and a
post-treatment were performed in the same manner as in Examples
except that the portion painted by using a roll coater was painted
by using a bar coater. Thus, a test piece of the hydrophilic film,
a test piece having the crosslinked hydrophobic film on the
hydrophilic film, a test piece having the hydrophilic film on the
anticorrosive film, or a test piece having the hydrophilic film
formed on the anticorrosive film and having the crosslinked
hydrophobic film thereon was produced. 2 .mu.L of pure water were
dropped on the hydrophobic or hydrophilic film to be subjected to
the measurement of the test piece placed horizontally and then the
contact angle of a water droplet formed on the film of the test
piece was measured with a contact angle meter (manufactured by
Kyowa Interface Science Co., Ltd.: CA-A).
[0164] (Measurement of Area Ratio of Crosslinked Hydrophobic
Film)
[0165] The fin material having a size measuring about 10 by 10 mm
was cut out of the heat exchanger produced in each of Examples 1 to
12 and Comparative Examples 1 to 7, the carbon (C) mapping of the
surface of the film was performed with an X-ray microanalyzer
(EPMA), and the area ratio of carbon (C) in an area measuring 5 by
5 mm2 was calculated by image analysis.
[0166] (Evaluation of Heat Exchanger)
[0167] Next, a 50-wt % aqueous solution of propylene glycol was
introduced as a refrigerant into the test heat exchanger of each of
Examples 1 to 12 and Comparative Examples 1 to 8 thus produced. The
refrigerant was circulated in a thermostatic chamber having a
chamber temperature of 2.degree. C. and a humidity RH of 90% or
more under the conditions of a refrigerant temperature of
-6.degree. C. and a refrigerant flow rate of 1 L/min, and then the
heat exchanger was operated for 45 min, followed by the observation
of a frost formation state in the heat exchange fin of each test
heat exchanger. In addition, after the frost formation, a
defrosting operation was performed with the refrigerant at
30.degree. C. for 3 min, followed by the observation of the
presence or absence of the formation of a bridge by melt water (or
condensed water) produced between heat exchange fins.
[0168] The frost formation-suppressing effect was evaluated as
described below. A time period required for the formation of frost
on the entire surface was measured and the evaluation was performed
by the following criteria: x: the case where the time period was
less than 15 min, .DELTA.: the case where the time period was 15
min or more and less than 30 min, 0: the case where the time period
was 30 min or more and less than 45 min, and .circleincircle.: the
case where no frost formation occurred even after a lapse of 45
min. In addition, a condensed water-removing effect was evaluated
as described below. The state of adhesion of the melt water (or
condensed water) between the fins after the defrosting operation
was observed and the evaluation was performed by the following
criteria: x: the case where the bridge occurred on substantially
the entire surface, .DELTA.: the case where the bridge occurred on
part of the surface, and .smallcircle.: the case where the
occurrence of the bridge was not observed.
TABLE-US-00004 TABLE 4 Example 1 2 3 4 5 6 7 8 9 10 11 Kind of fin
substrate a a a b c c -- -- c c -- Hydrophilic Kind of coating E-1
E-2 -- E-3 -- -- -- -- -- -- -- surface material Thickness min. 1.1
0.7 -- 0.5 0.5 0.5 2.0 2.0 0.5 0.5 2.0 (.mu.m) max. 1.5 1.0 -- 0.8
10 10 35 35 5 5 15 Water contact 5 15 35 10 27 15 10 7 32 21 8
angle (.degree.) Hydrophobic Kind of coating D-1 D-1 D-2 D-2 D-3
D-4 D-5 D-6 D-7 D-7 D-8 surface material Thickness (.mu.m) 0.7 0.4
0.4 1.0 0.7 1.0 0.2 5.0 0.2 1.0 2.5 Water contact 101 100 100 105
105 103 100 108 100 105 108 angle (.degree.) Post-treatment Absent
Absent Water Water Absent Alkali Water Acid Absent Water Absent
washing washing washing washing washing washing Area of crosslinked
hydrophobic 42 75 60 52 43 25 54 38 21 39 45 film (%) Frost
formation-suppressing .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .largecircle.
.circleincircle. .circleincircle. .largecircle. .circleincircle.
.circleincircle. effect Condensesd water-removing effect
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. Example Comparative
Example 12 1 2 3 4 5 6 7 8 9 10 Kind of fin substrate -- -- -- --
-- -- c c -- a a Hydrophilic Kind of coating -- -- -- -- -- -- --
-- -- E-1 -- surface material Thickness min. 2.0 0.5 0.5 1.2 1.2
1.2 1.2 1.2 1.2 1.5 -- (.mu.m) max. 15 4 4 15 15 15 15 15 15 1.8 --
Water contact 5 5 5 7 7 7 7 7 7 5 35 angle (.degree.) Hydrophobic
Kind of coating D-8 D-1 D-1 F-1 F-2 F-3 F-4 F-5 -- F-1 F-2 surface
material Thickness (.mu.m) 0.8 6 0.01 0.2 2.0 5.0 2.0 1.0 -- 0.2
2.0 Water contact 100 100 70 95 80 100 105 100 -- 95 80 angle
(.degree.) Post-treatment Water Absent Absent Water Absent Absent
Absent Water Absent Absent Water washing washing washing washing
Area of crosslinked hydrophobic 70 95 5 2 25 70 65 5 -- 51 70 film
(%) Frost formation-suppressing .circleincircle. .circleincircle. X
X X .DELTA. X X X X X effect Condensed water-removing effect
.largecircle. X .largecircle. .DELTA. X X X X .largecircle.
.largecircle. X
REFERENCE SIGNS LIST
[0169] 1 . . . heating medium-introducing port, 2 . . . heating
medium-discharging port, 3 . . . header pipe, 4 . . . extruded flat
tube, 5 . . . corrugated fin.
* * * * *