Note: Descriptions are shown in the official language in which they were submitted.
~2~669S
HYDROPHILIC-FILM-FORMING PREPARATIONS
BACKGROUND OF THE INVENTION
Field of the Invention:
This invention relates to hydrophilic-film-forming
preparations which form hydrophilic films on surfaces of
5 materials such as metal, glass, plastics, etc.; to arti-
cles having such hydrophilic films; and to a method of
forming a hydrophilic film especially having corrosion
resistance.
The term "article" as herein used means that made
Of an appropriate industrial material such as metal, glass,
plastics etc. in an appropriate shape, for example, a sec-
tion such as a short-length plate material, a continuous-
length plate material (e.g. a rolled product such as foil,
sheet, plate), a circular material such as rod, bar, tubu-
lS lar product, a press blank material, an extruded sectionetc. or workpieces obtained by processing the above into
desired final shapes, which have been provided with a
film, and in the case of a section, said shape also in-
cludes that adaptable for plastic working processes such
as forging, deep-forming, bending, punching, etc.
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12~61695
Descri tion of the Prior Art-
p
Hydrophilic-film-forming preparations are used for
imparting hydrophilic films on material surfaces so as to
prevent the formation o condensed water droplets on the
material surfaces and also tor antistatic and defogging
purposes.
For example, in heat exchangers equipped with plate
or with corrugated fins, with the progress in the tendency
to higher performance and to compactness, the inter-fin
distance has been made smaller for improving heat transfer
capacity. Heat exchange with the atmosphere is made via
the fin surface and atmospheric moisture condenses on the
fin surface, but if the inter-fin distance has been made
smaller to e.g. 3 - 4 mm or less, the condensed water
forms a bridge between the fins and hence increases the
air-flow resistance, thus resulting in noise generation
and a reduction in energy consumption efficiency, and
therefore, it has been the practice to prevent the bridge
formation by imparting hydrophilic properties to the
fin surface. For imparting such hydrophilic properties,
an appropriate means is employed according to the metal
material used, and, for example, it is known to apply
resin paints containing a silica powder or a surface
active agent as an agent for imparting hydrophilic pro-
perties. However, various problems were encountered;for example, the silica powder came off on press molding
resulting in reduced uniformity of the film, and in order
lZl~i695
to avoid this, if the silica powder was added in a large
amount, it in turn reduced the thickness of the inorganic
film and reduced the corrosion resistance of the film.
Whereas, if the hexavalent chrominum ion concentration
was increased in order to offset this effect of silica,
then the hexavalent ions dissolved out from the formed
film and caused die abrasion when die molding was con-
ducted after film formation, or the surface active agent
gradually dissolved out with time to decrease the hy-
drophilic properties, and in some use environments the
increase in hydrophilic properties caused a decrease
in the corrosion resistance of the metal material.
SUMMARY OF THE INVENTION
The present inventors have discovered that since
ion exchange resins are inherently insoluble in water,
have hydrophilic exchange groups and a strong capacity
to absorb water from the atmosphere, by dispersing an
ion exchange resin powder in a resin paint, an excellent
hydrophilic-film-forming preparation may be obtained.
Furthermore, by providing an appropriate undercoat
treatment, corrosion resistance is also improved.
Accordingly, it is a main object of this invention
to provide film forming preparations having excellent
hydrophilic properties.
Another object of this invention is to provide
articles having a hydrophilic film on at least one sur-
face thereof.
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lZ1669S
It is yet another object of this invention to
provide a method of forming a hydrophilic film on at
least one surface of a material.
According to the invention there is provided a
hydrophilic-film-forming preparation which comprises a
liquid coating vehicle, a film-forming binder component
in said vehicle and adapted to form a continuous film upon
evaporation of said vehicle, and discrete solid particles
of an ion exchange resin dispersed in said vehicle and
insoluble therein.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the material for the article include
metal, glass, plastics and their composites. More spe-
cifically, examples of the metal materials include iron,
steel, aluminum, copper and other generally employed
metals, and alloys thereof. Examples of the plastics
include commercially available general-purpose thermo-
plastic synthetic resins, thermosetting synthetic resins,
reinforced plastics, etc. These materials may be pro-
vided with an undercoat treatment, if desired, as decribedbelow in addition to surface cleaning such as degreasing
etc. before forming a hydrophilic film.
The film-forming preparation which forms such a
hydrophilic film is that having the components described
below~
As the coating binder component, those conveniently
FR011 ~ 561 571~ ' ~4 ~ 7 1~1 al
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used in resin paints may suitably be selected from among
thermoplastic synthetic resins and ~hermosettins synthetic
resins, but taking into considerat on the use conditions of
the product to which the hydrophilic film is to be applied,
the stability of the ion exchanse resin, etc., a resin
having a softening temperature of 80~C or higher is preferred
in the case of a thermoplastic resin. In the case of a
thermosettin~ resin, if one ha~ing a setting temperature
of higher than 150~C is used, the stoving time or the film
is preferably 10 minutes or longer, whereas if a resin having
a setting temperature of lower than 15CC. is used, the stoving
heating time is preferably up to 1 minute.
As the resin in the coating binder component satisfying
the above conditions, alkyd resins, acrylic resins, polyvinyl
alcohol resins, vinyl acetate resins, epoxy resins, phenolic
resins, polyester resins, silicone resins, fluorocarbon resins,
urethane resins etc. may be used but these examples are merely
illustrative and not limitative.
Further, the present film-forming preparation may
contain, as a coating auxiliary element in order to obtain
flowability on coating~ either water, in the case of a water-
based paint, or a hydrocarbon, an alcohol, an ester, a ketone,
an ether or ~he like in the case of an or~anic solvent~based
paint depending on the characteristics of the resin used, as
with the case of conventional paints.
~he amo~nt of the solven~ added ~ay be freely selected
:12~66'95
in an appropriate range in order to obtain flowability
according to the coating means as with the case of con-
ventional paints, and also may be selected in an appro-
priate range depending on the desired hydrophilic level.
As the ion exchange resin, in general, those ob-
tained by attaching a hydrophilic atomic group, such as a
sulfonic acid group, a carboxylic acid group, a phosphonic
acid group, a phosphinic acid group, a quaternary ammonium
group or a primary or secondary amine group to a conden-
sation type resin such as a phenolsulfonic acid type, an
ethyleneimine - epichlorohydrin type, an epoxy resin etc.,
or to an addition polymeric resin obtained by copolymer-
izing styrene or methacrylic acid with divinylbenzene as a
crosslinking agent, are frequently used as cation exchange
resins and anion exchange resins. Further, amphoteric ion
exchange resins obtained by polymerizing acrylic acid to
strongly basic anion exchange resins, fluorocarbon resins
into which hydrophilic atomic groups have been introduced,
etc. are commercially available and are also usable. From
a viewpoint of providing hydrophilic properties, ion ex-
change resins having an exchange capacity per gram of the
dry ion exchange resin of 0.5 (meq./g-Dry R) or more, pre-
ferably 1.0 (meq./g-Dry R) or more are employed in this
invention. Those having less than 0.5 cannot provide the
required wettability.
Furthermore, even that based on a phenolic resin may
also be applied as an ion exchange resin if it is insoluble
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i695
and possesses sur~ace active agent-like characteristics.
Of these ion exchange resins, cation exchange resins
(also including alkali metal substituted salt types) are
suitably employed in the respect that they are rich in
hydrophilic properties and inter alia a sulfonic acid type
strongly acidic cation exchange resin is most suitable.
Further, depending on the desired hydrophilic level, it
is also possible to use a mixed system of two or more compo-
nents obtained by mixing a strongly acidic cation exchange
resin and a weakly acidic cation exchange resin, a highly
basic ion exchange resin and a weakly basic ion exchange
resin, or a cation exchange resin, and also possible to use
a scrap ion exchange resin with or without a virgin speck.
Commercially available ion exchange resins are usu-
ally particles of 10 - 50 mesh and therefore used after
grinding according to the desired film thickness. In
general, a film thickness of about 0.5 - 50 ~m is prac-
tical. If it is less than 0.5 ~m, a film having desired
characteristics cannot be stably obtained, whereas if it
exceeds 50 ~m, improvement in the characteristics level
according to the film thickness is not manifested but
merely results in an increase in cost. Therefore, con-
sidering film thickness, uniformity, etcO, it is general
to grind to an average particle diameter of 1 m or less,
for example, to effect grinding treatment by a vibrating
ball mill etc. before use. For example, in the case of
fins for heat exchangers, an average particle diameter
lZ~669~5
of 0.5 - 1 ~m is preferred. Further, if that ground
for an analytical grade for special purposes or for an
ultrapure grade is available, it is needless to say that
it may be used as such. Furthermore, it is also possible
to apply a means for adjusting to a desired final particle
diameter by auxiliarily utilizing a step of kneading with
a resin paint.
While the amount of the ion exchange resin added
relative to the coating binder component in the present
film-forming preparation can be appropriately selected
depending on the exchange capacity of the particular ion
exchange resin used and the hydrophilic level desired for
the formed film, it is necessary that the proportion of
the ion exchange resin to the total weight of the coating
binder and ion exchange resin powder be 0.1 or more on the
dry weight basis (hereinafter, the aforesaid proportion
is referred to as the "exchange resin ratio"). If the
exchange resin ratio is less than 0.1, it is difficult to
stably obtain the desired hydrophilic level. The exchange
resin ratio is suitably in the range of 0.3 - 0.7. If
it exceeds 0.7, the adhesion to the substrate is poor.
~ or example, where the present fil~-forming
preparation is especially used for antistatic purposes
requiring only hydrophilic properties, the exchange
resin ratio is preferably 0.5 or more, but where both
hydrophilic properties and die moldability are parti
cularly required, it is preferred that the exchange
resin ratio be 0.3 or more. Further, where
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applied to defogging of plastic materials, the exchange
resin ratio can be as low as about 0.2
The solvent or vehicle for the coating auxiliary
element may be added to the present film-forming pre-
paration in a mode where it is added to a mixed stock
solution of the coating binder component and the ion
exchange resin in use, in a mode where these three mem
bers are integrally added and mixed at the start, etc.
Further~ it is also possible to add to the present
film-forming preparation various additives which impart
various properties to the paint. More specifically,
a dispersant, a mildewproofing agent, an anti-skinning
agent, a slip agent, an antifoaming agent etc. may be
added in amounts of about 1 - 2% by weight respectively
if desired. Furthermore, as an agent for improving the
initial hydrophilic properties, a surface active agent
such as ~-olefinsulfonates etc. may be added in an amount
of 0.5 - 10% by weight.
The use embodiments of the present film-forming
preparation are now described. Any conventional coat-
ing means in the paint art may be used, for example,
roll coating, spraying, dipping, brushing, spin coating
etc., and the coating weight in this case is suitably
1 - 3 g/m2 (dry basis). If the paint is an air dry-
ing type, then it is coated and thereafter air dried as
such to fix the film, or if the paint is a thermosetting
type, stoving is conducted under proper heating condi-
tions which do not adversely affect the characteristics
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FRO11 8~ 561 5718 ~216695 '84. 11.117 1~i08
29-12
o~ the ion exchange resin. In the next place, as pre-
treatment for the film-forming treatment, it is also an
effective mea~s to apply undercoat treatment described
hereinbelow for the p~rpose of improving the corrosion
resistance of the material surface and the ~ixing of the
film.
As the undercoat treatment, a method of forming an
oxidized film or a method of forming an anti-corrosive metal
film using aluminum, zinc, copper, chrominum etc., and the
~ike, may be used or these two methods may be used in com-
bination.
As the method of forming an oxidized film, any of
conventional methods, e.g. a chemically oxidized film method,
an anodized film method etc. can be used, but the chemically
oxidized film method is pre~erred because a film of a relati-
vely thin thickness having excellent corrosion reistance can
be continuously and inexpensively obtained.
Examples of the chemically oxidized ~ilm method
include, according to the bath component, the so-called
alkali chromate methods such as M3V method, ~W method,
Pylumin method and Alrock method and the so-called acidic
chromate methods such as Bonderite method, and Alodine method,
as well as Boehmite treating method, a phosphate salt method
etc. In ~eneral, there is employed a chromate ~ilm treatin~
method which comprises using chromic acid luoride as a main
bath component and treat~ing at a bath tempe~ature of 20 - 40C
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FROrl ~ 561 5718 12~L6695 a4 ll e7 131 1~
29-13
for 5 seconds to 5 minutes, a chromium phosphate film treatirg
method which comprises usin3 ch~omic acid, hydrofluoric acid
and phosphoric acid as main bath components and treat in~ at
26 - 60C for 30 seconds to 7 minutes, a phosphate salt film
method which comprises using a phosphate salt such as zinc
phospate, mAnganese phospate etc. as a main bath component
and treating at a bath temperature of 60 - 100qC for about 5
minutes, or a 30ehmite film method which comprises treating
with hot water-saturated steam, triethanolamine etc., and
the like.
These methods may be effected by dipping, spraying,
roll coatin~, steam gun method etc. By these methods, a
chemically oxldized film of O.OQ5 Ym or more in thickness
is formed, and with less than 0.005~m, the characteristics
as the anti-corrosive underocat are insufficient. ~or
example, in the case of fins for heat exchangers, about 0.01
- 0.5 ~m is preferred, and where there is no need for molding
after the film ~ormation, or where the heat conductivity of
the film is not important, a film thickness of 5 ~m or more
can also be used.
Examples of the method of forming ~n anti-corrosive
metal film include electroplating, deposition, flame spraying,
cladding etc. using a metal such as aluminum, zinc, copper,
chromium etc. and an appropriate method is selected therefrom
according to the nature of the metal material and the use.
In other words, for example, in the case of zinc
FR~M a3 561 5718 12~669S ~a4. 11.07 1~1 12
coating, a zinc film may be formed by a method which comprises
electroplating in a bath con~aini~g ~SO - 240 g/l of zinc
oxide, 500 - 550 g/l of sodium hydroxide and 5 - 10 ~/l o~
sodium cyanide as main components, an acidic zinc electro-
platin~ bath method using 3inc sulfate, æinc chloride andzinc borofluoride, a zincate electroplating bath method
usin~ zin^ oxide and sodium hydroxide as main components,
a neutral zinc electroplating bath method in which the bath
contains a chelating agent such as an oxy acid in addition
to zinc chloride, a pyrophosphoric acid bath method etc., or
a molten zinc plating method which comprises flux pre-
treating with ammonium chloride and ammonium 2inc chloride
and subsequently dippin3 in a molten metallic zinc bath,
zinc flame spra~ing, cladding, or the like. As the method
of coating alu~inum, there may be used molten aluminum
plating which comprises dipping in a flux bath comprising
a chloride system o~ potassium chloride and sodium chloride
or a fluoride system of cryolite and aluminum fluoride and
subsequently dipping in a molten aluminum bath, plasma flame
spraying, vacuum deposition, cladding etc.
By these methods, an anti-corrosive metal film of
3 ~m or more in ~ilm thickness is formed, and if the
thickness is less than 3~-~, the characteristics as the
anti-corrosive undercoat are insuf icient. ~he film
thickness varies depending on the use purpose, and, for
example, in the case of fins for heat exchangers, about
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FRO~ 13~ ~61 5718 ' 84. 1 1 . a7 1~
~: 1216695 29-15
5 _ 10 ~m is preferred, but where there is no need for molding
after the film formation or where the heat conduct1vity of
the film is not importar.t, an appropriate thickness of ~ore
than 10 ~m may be used.
Of the~e methods, as the undercoat treatlng method
of improving the corrosion resistance, the chromate treatin~
method is most pre~erred in practice and this can exert the
best effects including economy.
The hydrophilic ilm according to this invention has
been described above, ahd the film formed with the present
preparation has such features as extremely low deterioration
with time in use and very small die abrasion when a material
to be treated is die molded after vhe film formation. There-
~ore, it is not only suitable as a hydrophilic-film-forming
preparation for fin members ~or heat exchangers equipped
with high density fiGs but it also can form a film rich in
the power to retain hydrophilic properties which is not
achievable with the conventional preparations and thus may
be used for e.g. antistatic defogging purposes etc., and,
in addition, by providing desired undercoat treatment,
excellent corrosion resistance is manifested.
This invention is more particularly described by
the followin~ examples.
EXAMPLE 1
..
A co~merically available sulfonic acid type poly-
styrene-ba6ed cation exchange resln: 4.5 (meg/g-DRY R)
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:lZ~669S
(Amberlite* IR-120 produced by Rohm & Haas Co.) was ground
in a vibrating ball mill for about 30 minutes and dried
by an infrared lamp to obtain a fine powder of an average
particle diameter of 15 ~m and a water content of 12%.
Thereafter, 200 g of this fine powder, 650 g of an epoxy
ester-based water soluble paint (Watersol* S-352 produced
by Dainippon Ink and Chemical, Inc., solids content 46%),
100 g of butyl Cellosolve* and 400 g of water were added
to a pot mill and kneaded for about 6 hours to achieve
uniform dispersion. As a result, the secondary particle
diameter of the ion exchange resin became 0.5 - 1 ~m.
The resultant film-forming preparation was coated using
a bar coater (#12) on a previously cleaned aluminum panel
as a material and dried at 230C for 30 seconds to fix.
COMPARATIVE EXAMPLES
In a case where the epoxy ester-based paint used in
Example 1 was directed coated tComparative Example 1)
and a case where a commercially available thermosetting
acrylic resin paint containing a wet type surface active
agent (solids content 18%) was coated (Comparative Exam-
ple 2), treatment was conducted using coating and drying
conditions similar to those in Example 1. The products
of these examples and comparative examples were sub~ected
to various tests. The results are shown in the following
Table 1.
In the table, the initial wettability shows the wetted
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FRO~1 a3 561 5718 ' 34 . I I . ~7 13 1 ~ 7
` 1;~1669S
conditions of a 6ample 30 seeonds after picking up said sample
dipped in deioni.zed water, and is expressed relative to the
case where the entire surface has been wetted taken as 100~.
Table 1
_ _. . _...... _ .. ~
Water Wettabili~y Die Brine
. _ Molda- Spraying
Initial Wetting bility Test
Wettabi- Test (a~ter lOOhrs)
. . . . _ _ _ _ _
100~ even ! Corrosion
Example 1 100~ after 1000 Good within 5%
_
Comparatlve 0 0 Good 1, -do-
_ . t --~- --------- ... .
Example 2 100% 30%hraf5ter Good -do-
. . ._. ~,,,~ . __. . . _.. _ _ ._ _ . _ .. _ . _. _ .. . . . . . .emarks Wetting Test: The sample was left in an atmosphere
of a temperature of 50C and a
humidity of 100~.
Die Moldability: Evaluated by the die abraded
condltions.
From these results, it can be seen that where the resin
paint of Comparative Example 2 is used, although the die mold-
ability after the film formation is good, the deterioration of the
hydrophilic properties (in this case, expressed by the water
wettabillty) is less with the case of this lnvention and better
results are obtained by this invention.
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~2~6695
EXAMPI,E 2
8 g of a 5~ solution of cobalt naphthenate was added
as a drier to the composition of ~xample 1, and a similar
kneading operation was conducted. The resultant paint
was coated on a previously degreased aluminum fin plate
material for heat exchangers, forcedly dried and left at
room temperature for 3 days to fix the film.
Thereafter, a test similar to that in Example 1 was
conducted to obtain almost similar results, and, in parti-
cular, it was found that there was remarkable enhancement
in durability against xylene, thus indicating improved
corrosion resistance. This is believed due to the action
of cobalt naphthenate as a catalyst.
EXAMP~E 3
A fine powdered sulfonic acid type polystyrene-based
cation exchange resin obtained by the process described
in Example 1: 4.5 (meq./g-DRY R) (Amberlite* IR-120) was
mixed with an air drying acrylic resin paint ~Acrydic*
A-165 produced by Dainippon Ink and Chemical, Inc.; sol-
ids content 45%) at an exchange resin ratio of 0.70 also
together with 0.5% based on the resin paint total weight
of a wetting dispersant (BM 1000* produced by Bayerische
Motoren Werke AG, West Germany) for improving the dispers-
ibility of the ion exchange resin, and thereafter kneading
was similarly conducted in a pot mill for 5 hours.
The resultant film-forming composition was coated on a
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~2~6695
transparent plastic plate of l.Omm in thickness to a dry
film thickness of 0.5 ~m and left at room temperature to
dry and fix.
The coated surface o~tained was subjected to an
exposure test under conditions of an atmosphere of a
temperature of 40C and a relative humidity of 90 + 5
percent and an outer temperature of 27C. As a result,
the plate having a film formed according to this in-
vention kept transparent and did not show cloudiness,
whereas a naked plastic plate without coating showed
cloudiness on the entire surface.
EXAMPLE 4
250 g of a dried fine powder (average particle
diameter 1.0~ m, water content 5~) of a weakly acidic
cation exchange resin; 10 (meq./g-DRY R) (Amberlite*
I~C-50 produced by Rohm & Haas Co.)., 700 g of a modified
alkyd resin paint (P- 86-50* produced by Dainippon Ink
and Chemical, Inc.), 300 cc of xylene, 30 g of a dispers-
ant (BM1000* produced by Bayerische Motoren Werke AG, West
Germany) and 7 g of a leveling agent (BM1800A* produced
by Bayersiche Motoren Werke AG, West Germany) were added
to and mixed in a high speed mixer for 30 minutes. The
solids content of the alkyd resin paint was 50~, and the
exchange resin ratio of the resultant film-forming pre-
paration was 0.38.
* Trade Mark
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~2~1695
This film-forming preparation was coated by brushing
on a zinc plated steel plate, and heated at 200C to form
a film.
The wettability of the film was measured under con-
ditions similar to those in Example l to obtain a wettingtest result of 97% after 48 hours, which indicated that
the deterioration of the hydrophilic properties was ex-
tremely low.
EXAMPL~ 5
A hydrophilic-film-forming preparation produced simi-
larly as in Example l (except that ~he average particle
diameter of the ion exchange resin ground in the vibrating
ball mill was 1.0 ~m and the water content after drying by
an infrared lamp was 5%) was continuously coated by a roll
coater on a previously degreased rolled fin material for
aluminum heat exchangers as a material, and dried in a hot
air drylng oven at 230C for 30 seconds to fix.
A test sample was prepared from the resultant fin
material, this sample was dipped in deionized water,
picked up and the water wettability 30 seconds later was
measured to give 100%, and when a wetting test (conducted
in an atmosphere of a temperature of 50C and a humidity
of 100%) was carried out, the water wettability was found
100% even after lO00 hours. Further, the brine spraying
test result showed a corrosion rate after lO0 hours of
within 5%.
Thereafter, the film-formed fin material as an article
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~16695
was punched into fin members of a desired shape by press
molding and the fin member surfaces were provided with
louver processing.
In the press molding, neither abrasion of the molding
die nor damage to the film was observed as was observed
with silica-containing hydrophilic films, and thus good
working had been effected. Further, when the resultant
fin members were used by assembling into an automobile
condenser, the intended continuous operation was possible
even when there was a change in humidity in the atmosphere.
EXAMPLE 6
A coiled aluminum fin material (made of AA 310-5
alloy, plate thickness 0.12 mm) degreased with a weakly
alkaline cleaner (trade name~ FC 315 produced by Nihon
Parkerizing Co., Ltd.) was coated with a phosphoric acid -
chromate type treating agent having a concentration of
1.3~ by weight (trade name: Alodine 401-45 produced by
Nippon Paint Co., Ltd.) by spraying by heating at 35C
to form an undercoat of about 70 A on the surface.
Thereafter, a sulfonic acid type ion exchange resin
(trade name: R-120B produced by Japan Organo Co., Ltd.)
of an average particle diameter of 0.5 ~ 1~ m was added
to a catalytically curing epoxy ester-based water paint
(trade name: Watersol S346 produced by ~ainippon Ink and
Chemical Co.) so as to give a dry solids content of 40% by
weight, and thoroughly mixed to prepare a hydrophilic film-
forming composition, which was then coated on the above
-- 19 --
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12~l.6695
undercoat to give a coating weight of 1.5 9/m2 ~dry
basis) and heated at 230C in a hot air drying oven
for 30 seconds to effect stoving heating treatment.
The coiled material obtained by the above film-
forming treatment was subjectec3 to punching and wiping
to prepare cross members, which were evaluated by tests
for hydrophilic properties and corrosion resistance.
More specifically, the long term stability of the
hydrophilic properties was evaluated by the percentage
area wetted when left in an atmosphere of a relative
humidity of 95% and a temperature of ~0c for soo
hours, and this was 100%, thus confirming good hydro-
philic properties.
On the other hand, the corrosion resistance was eval-
uated by a 500 hour brine spraying test according to
JIS Z 2371 (1955), and it was found that corrosion had
been generated neither in the unprocessed part nor in
the wiped part, thus confirming also excellent corrosion
resistance, and therefore, it was confirmed that by this
invention, a film excellent in both hydrophilic proper-
ties and corrosion resistance may be obtained and that
machinability after the film formation i5 also excellent.
While the invention has been described in detail and
with reference to specific embodiments thereof, it will
be apparent to one skilled in the art that variations and
modifications can be made therein without departing from
the spirit or scope of the invention thereof.
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~2~6695
For example, it is possible that a hydrophilic
film-forming composition is formed immediately on an
article surface by means of mixing components which
comprises a step of forming an resin paint film on the
article surface and a step of spraying an ion exchange
resin powder on said resin paint film.
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b,
