Note: Descriptions are shown in the official language in which they were submitted.
1 3 1 9 5 7 ~ PATENT
~ocket M 4659 P + A/NI
TREATMENT METHOD FOR IMPARTING ANTIMICROBIAL AND
HYDROPHILIC PROPERTIES TO ALUMINUM SURFACES
Field of the Invention
This invention relates to a surface treatment method
fox making the surfaces of metals, particularly aluminum
and aluminum alloys (both being briefly denoted herein
merely as "aluminum"), hydrophilic, resistant to growth of
microbes, and corrosion resistant. More particularly, the
present invention relates to a surface treat~ent method for
aluminum materials for use in heat exchangers.
Statement of Related Art
ThPre are many known surface treatments for aluminum
heat exchangers and their components such as fins and the
like with the objective of preventing white rust. Examples
of these surface treatments are anodic oxidation coatings
and resin coating treatments, including those which contain
hexavalent chromium. These coated surfaces are almost
entirely lacking an affinity for water; instead, they are
water repellent. ~hromate conversion coating treatments
are also used, but such coatings have only a modest water
affinity even on freshly formed coatings, and with the
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1319571
passage of time, particularly under hot, dry conditions,
chromate conversion coatings tend to become thoroughly
hydrophobic surfaces.
The fin spacing in many heat exchangers has been made
very small in order to pack as much cooling surface area as
possible into a given volume and thereby improve the
radiation or cooling effectiveness. When the cooling
surfaces or fins are even moderately hydrophobic, having a
water wetting angle substantially greater than zero, water
droplets tend to form on the surfaces by condensation of
water from the atmosphere. When the cooling surfaces are
very closely spaced, such water droplets can easily bridge
the spaces between adjacent surfaces, thereby impeding the
smooth flow of air through the spaces between the cooling
surfaces and reducing the heat exchange efficiency.
Moreover, the water droplets accumulated in the fin
gaps, because they are easily dispersed and scattered about
by the heat exchanger's blower, are not effectively
collected by any conventional droplet collector installed
at the bottom of a heat exchanger, so that the vicinity
around the heat exchanger becomes wet.
Accordingly, in order to avoid the generation of the
mesh-like obstruction by the water droplets remaining in
the fin gaps, treatments have been proposed for the purpose
of imparting hydrophilicity to aluminum surfaces and
improving their wettability by water.
In particular, the treatment of aluminum surfaces by
silicates, for example, waterglass, etc., is widely
employed as a hydrophilicizing treatment because of the
high water affinity and high heat resistance of the
surfaces thus produced, as well as low cost~ Proposed
methods for this type of treatment include, for example,
coating an aqueous silicate solution directly on
conversion-treated aluminum or coating the silicate
solution on the aluminum after the preliminary formation of
an organic polymer film.
For example, Japanese Patent Application Laid Open
131q571
Number 50-38,645 proposes a method for the formation of a
hydrophilic coating in which aluminum is first treated with
a solution containing alkali metal carbonate and alkali
metal chromate or alkali metal dichromate and is then
treated with alkali metal silicate.
United States Patent 3,989,550 teaches a
hydrophilicizing treatment method which consists of a first
treatment with a solution containing fluorine, chromic
acid, and phosphoric acid, in each case as ions. This is
followed by treatment with an alkali metal silicate and
then heating.
Japanese Patent Application Laid Open Number 54-57,264
teaches a heat exchanger that has surfaces with both
corrosion resistance and hydrophilicity, as a result of the
formation of a conversion coating on the aluminum surfaces.
Here, after the surfaces of an aluminum plate-fin-type heat
exchanger have been treated with an aqueous solution of a
silicic acid compound, a treatment is then carried out with
an aqueous alkaline solution which contains an alkaline
earth metal compound.
Japanese Patent Application Laid Open Number 57-82,467
teaches an improvement in physical properties by means of
a post-treatment, and concerns not only the prevention of
the discoloration of aluminum surfaces by hot water, but
also refers to an improvement in corrosion resistance. In
this case, the aluminum surface is coated with an aqueous
solution of an alkaline silicic acid material. After
drying, an anticorrosion coating is then formed by
neutralization with an acid such as nitric acid, etc.
Japanese Patent Application Laid Open Number 61-84,383
teaches a method for treating the surface of aluminum for
heat-exchanger service whose characteristic feature is that
the aluminum surface is first coated with an aqueous
solution of an alkali metal silicate to which a borate has
been added; after drying, an aqueous solution of an
inorganic acid, organic acid, or acidic salt of an
inorganic or organic acid is then applied. KBO2, CaB~O7,
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and Na2B407 are taught as optimal examples of the borate,
while phosphoric acid or dihydrogenph~sphate, tannic acid,
myoinositol hexaphosphate, polyacrylic acid, and their
salts are given as optimal examples of the inorganic or
organic acids and acidic salts thereof. Benefits taught
for this method are an improvement in corrosion resistance
and prevention of saponification of the lubricating oil
applied in post-treatment of the treated aluminum.
Turning now to a consideration of the operation of
automobile air conditioners and heating and/or cooling air
conditioners in household service, one encounters the
problem that an undesirable odor, which accompanies the fan
draft during operation and particularly during start-up,
often fills the interior of the conditioned room or
passenger compartment. This odor tends to be stronger when
more time has elapsed from the installation or last
previous use of the air conditioner. The cause of the
worsening of the odor with increased time is believed to be
proliferation of fungi and/or bacteria in the air
conditioner, particularly on and between the fins of the
heat exchanger. With regard to preventive measures
directed at this, discharging the air to the exterior using
a bypass during the initial stage of operations and
sterilization using a sterilizing lamp have been proposed.
However, the most effective method involves the application
to the heat exchanger itself of a coating which contains an
antimicrobial agent.
The ~ollowing are examples of teachings of how to
impart an affinity for water to the heat exchanger fin
surfaces while at the same time preventing the undesirable
odor, through the application of a coating which contains
an antimicrobial agent to the heat exchanger, filter,
ducts, and the like, in air conditioning service: Japanese
Patent Application Laid Open Numbers 58-10,051, 58-10,052,
58-101,717, 58~102,073, 59-124,428, 59-199,339, 60-50,397,
and 61-168,675. However, in each case the antibacterial
and anti~ungal agents in the preceding are organic
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1 31 q571
compounds or their metal salts.
Boric acids, the oxyacids afforded by the hydration
of B203 and their salts are known for antiEungal and
antibacterial applications.
Busan ll-M1 (sold by Buckman Laboratories, Inc., USA)
is an anti-rust pigment which has barium metaborate as its
principal component. It is marketed for paint and plastic
applications as a pigment which also has antimicrobial
properties, and it is registered with the EPA under No.
1448-17-AA. Its particle size is approximately 65% > 2
micrometers, approximately 15% between 1 to 2 micrometers,
and approximately 10% < 1 micrometer.
Japanese Patent Application Laid Open Number 56-81,373
discloses an antifungal paint which contains zinc borate,
while Japanese Patent Application Laid Open Number
60-146,807 discloses the addition of a thickener, such as
an acrylic acid polymer, etc., to an antifungal agent which
contains hydrogen peroxide and boric acid. The latter
refers to application as a coating on bathroom ceilings,
etc. Japanese Patent Application Laid Open Number
60-90,266 relates to a novel pigment which is obtained by
a reaction in which a silicic acid compound is added to a
phosphoric acid compound plus a boric acid compound plus
Ca, Sn, Ba, Zn, Al, or their equivalents. This is
described as effective both as an antifungal as well as an
anti-rust in paint applications.
As discussed above, a number of methods are known for
the treatment of heat exchangers and aluminum used in their
fins in order to impart hydrophilicity and antifungal
and/or antibacterial properties. Furthermore, treatment
agents simultaneously manifesting both of these effects
have also been proposed.
However, these known antifungal~antibacterial
hydrophilicizing methods suffer from various disadvantages
that are particularly notable in heat exchangers used for
air conditioning. Surface-treatment agents with a high
hydrophilicizing capacity are usually used to ameliorate
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the problem of mesh-like obstruction by condensed water
droplets. These agents are generally highly hydrophilic
organic polymers or waterglass. These materials are water
soluble, and water is generally used as the solvent in
these hydrophilicizing treatment solutions, thus avoiding
environmental problems and ignition hazards. When an
antifun~al is added to such an agent, a homogeneous mixed
solution can be easily prepared if a water-soluble
antifungal, for example, p-hydroxybenzoic acid, salicylic
acid, sorbic acid, salts of the foregoing, borax, and the
like, is used.
A problem with these water-soluble substances is their
short term of effectiveness due to elution by condensed
water during operation of the air conditioner. In a
specific response to this retention problem, a poorly
water-soluble or water-insoluble organic antifungal can be
used ky emulsifying and dispersing it in water after
dissolution in a suitable solvent, or an inorganic or
organic antifungal can be suspended in water after
comminution, followed in either case by addition to the
hydrophilicizing treatment solution. However, the
hydrophilicizing treatment solutions afforded by these
methods again suffer from several problems: in addition
to stability problems with the solution itself due to
sedimentation and separation of the emulsified antifungal,
it is difficult to obtain a uniform coating due to phase
separation from the waterglass or hydrophilic polymer when
the coating is dried.
Furthermore, due to the narrow fin spacing in heat
exchangers~ as well as considerations of the heat
conductivity and cost, it is advantageous for the coated
hydrophilicizing film to form as thin a film as possiblP,
less than 1 micrometer after drying. This places stringent
requirements on comminution of particles to be suspended
after grinding. Also, due to limitations in this regard,
complete coverage cannot usually be obtained by a film
produced using a hydrophilicizing treatment agent in which
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antlfungal particles are suspendecl; pinholes occur frequentl~ and
when they occur subs~antially recluce anticorrosion performance.
The presen-t applicants have previously discovered tha-t a
hydrophilic film, which manifests an excellent ~orrosion resist-
ance, excellent hyd~ophilicity, good initial odor characteristics,
good film bonding, and good p.rocessing properties, can be obtained
by coating and drying a waterglass hydrophilicizin~ treatment
agent on aluminum surfaces followed by treatment with a solution
containing a multivalent metal salt. This has been the suhject of
Japanese Patent Applications 62-179028 and 6~ 17gO29~ No borate
or other antimicrobial agent is used in the hydrophilicizing
treatment according to these earlier inventions.
According to the present invention there is provided a
process for generating an antimicrobial or hydrophilic surface on
an aluminum substrate, comprising:
(a~ coating the surface of said substrate with a
first liquid film of an aqueous solution comprising (i)
an alkali metal salt or a quaternary ammonium salt of
silicic acid, said salt having a molar ratio of silica
to monovalent cation between about 0.5 and about 8.5,
and (ii) a boric acid or a salt thereof;
(b) drying by heating the liquid film produced in
step (a) to obtain a first solld film on said surface;
(c) coating the solid film formed in s-tep (b) with
a second liquid film of a solution comprising water and
at least 0.01 mole per liter of a soluble salt or
hydroxide of a cation with a charge of at least two
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131957 1 ~7587 ~
units; and
(d) drying by heating the liquid film formed in
step (e~.
In a preferred embodiment the aluminum substrate is
prepared by the following additional treatments before the above
step (a):
(a') treatment with a chronie acid and ~hromate
ion containing treatment solution; and
(a'') coating the surfaee procluced by the treatment
of part (a') with a film about 0.3 microns thick of a
polyurethane elastomer.
Descriptlon of the Invention
Except in the operatiny examples or where othe~wise
expressly stated, all numbers in this description expressing
quantities of materials or reaction cond:ltions are to be
understood as modified by ~he word "about".
It has been diseovered that an antimierobial hydro-
philicizing surface treatment, which will provide a high
hydrophilicity, high corrosion resistance, and high antifungal
performance, and which avoids diffieulties with lubrieating oil
eoatability in post-treatment, ancl which results in ].ow odor, both
initial and lony-term, can be obtained by first eoating aluminum
with a hydrophilieizing aqueous treatment solution containing an
alkali metal and~or a quaternary a~monium silieate acid, along
with borie acid and/or its water-soluble salts, followed by
heating and drying to form a homogeneous film, and by then
carrying out treatment with a solution containing at least one
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1 31 9571
275~7-~3
species of multi~alent metals salt or hydroxide.
While not ~ishi~ to be ho~lnd by theory, the applicants
believe that the boric acid and/or ~ater-soluble borate added to
the ~7aterglass hydrophilicizing treatment solution may be
converted to a poorly ion-exchangeable
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multivalent metal salt by the subsequent aqueous
multivalent metal salt solution. Elution by condensation
water generated by operation of the heat exchanger is thus
made more difficult. Furthermore, the multivalent metal
ion may form a cross link between borate anions and the
anionic silicate network characteristic of waterglasses by
bonding to each kind of negatively charged entity. This
would serve to strengthen the hydrophilic film.
The film formed in the present invention, besides
preventing initial odor from heat exchangers that utilize
it, also prevents the longer-term development of odor
originating in the growth of bacteria and fungi.
The first treating solution used in this invention is
an aqueous solution containing quaternary amine
silicate(s), for example, QAS - 40 or QAS 25 from Nissan
Chemical Industries, Limited, or alkali silicat(es), either
of these types of silicates being alternatively referred to
below as waterglass(es). Waterglasses do not have a fixed
composition as do most salts, but can have greater or
lesser amounts of silicon oxide for a given amount of
cations. The solution for this invention preferably has a
value of 0.5 to 8.5 for the (SiO2)/(monovalent cation)
molar ratio, with Li, Na, and K preferred as monovalent
cations. More preferably, the cations are Na or K and the
molar ratio is 1 to 2.
The preferred types of boric acids for the present
invention are those with molecular formulas that can be
matched by mixing B2O3 with varying numbers of water
molecules, for example, orthoboric acid ~H3B03), metaboric
acid (HB02), and tetraboric acid (H2B4O7).
Waterglass, and particularly high SiO2 waterglass, is
prone to coagulation upon the addition of acidic
substances. Thus instead of the free boric acids noted
above, it is generally preferred to use neutral
water~soluble salts, ~or example, sodium, potassium, or
lithium borate. Furthermore, ammonium borate can also be
admixed in part.
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It is often useful to add water soluble organic
polymers to the solutions of silicates and borates
described above. suitable polymers include polyvinyl
pyrrolidone, the water-soluble salts of polyacrylic acid
or polymethacrylic acid, the polymers and copolymers of
unsaturated acids such as maleic acid, or itaconic acid,
the polymers and copolymers of acrylamide, methacrylamide,
and their derivatives, the partial hydrolyzates of
polyacrylamide and polymethacrylamide, polyvinyl alcohol,
poly(2-hydroxyethyl acrylate), the alkali metal salts of
polystyrenesulfonic acid, and pullulan.
The weight ratios in the aqueous solution preferably
is 5 to 100 parts, more preferably 20 to 60 parts, of
borate for each 100 parts of waterglass, and 0 to 100
parts, more preferably 0 to 60 parts organic polymer for
each lO0 parts of the sum of the waterglass and borate.
Of course, in addition to the preceding, surfactants,
leveling agents, non-boric acid antimicrobials, fragrances,
colorants, defoamers, rust inhibitors, and the like can be
present. Also, in order to increase the hydrophilicity,
hydrophilic metal oxide sols, for example, silica sols or
alumina sols can also be added.
The hydrophilicizing treatment solution obtained as
described above can be coated and then dried on a bare
aluminum surface, or it can be coated and dried after a
conversion treatment or priming with an organic polymer has
been used on the aluminum.
In the present context, aluminum also comprises
aluminum alloys, and no specific restriction is placed on
the application methodology: coating can be carried out
either on the sheet-form fin material or after installation
in a heat exchanger. In other words, one may freely
select ~rom among brush application, immersion, spraying,
roll coating, or flow coating, among others, according to
the form of the substrate to be coated, quantity of
application, and similar factors. Sheet-form fin material
is typically roll coated, while the installed product is
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typically imm~rsion coated.
After application of the hydrophilicizing treatment
agent, the aluminum heat exchanger is dried by heating,
without a water rinse, to form a hydrophilic coating film.
While the thickness of this film is not specifically
restricted in the practice of this invention, thicknesses
of approximately 0.02 to 2 microns are normally preferred
and 0.05 to 1 micron will usually be most preferable.
Drying is typically conducted in a hot-air drying
oven, but infrared heating or any other appropriate means
can also be used. The usual hot-air drying oven has
orifices through which hot air is ejected, and the aluminum
heat exchanger or other object is dried by passage through
the chamber while hot air is ejected from these holes.
While the drying conditions will vary substantially
according to the part to be dried, 80 to 300 degrees
Centigrade for 5 seconds to 30 minutes will usually be
suitable, with the longer times at the lower temperatures,
and the shorter times at the higher temperatures.
The dried hydrophilic film is then treated with an
aqueous solution of the salt of a multivalent metal. Both
flat fin sheet and assembled heat exchangers can be
suitably treated by immersion, and flat fin sheet can also
be treated by various other methods such as spraying, roll
coating, and curtain coating, among others.
Useable as the multivalent metal are magnesium,
calcium, strontium, barium, aluminum, titanium, zirconium,
chromium, molybdenum, manganese, iron, cobalt, ~opper,
zinc, tin, and any other cation with at least two charges
that forms a water soluble salt. Magnesium, calcium,
barium, and zinc are preferred. Water soluble solvents
such as alcohol can also bs present in the treatment
solutions. There is no limitation on the anion(s~ present,
so long as water solubility is obtained, the nitrates,
nitrites, fluorides, carbonates, bicarbonates, and
hydroxides are advantageous from the standpoint of
corrosion resistance.
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On the subject of the solution concentration, while
practice of the invention will be possible as long as the
cation's solubility is at least 0.01 mol/L-H2O, treatment
is more effective at concentrations of at least 0.1
mol/L-H2O. With regard to the upper limit on ~he
concentration, preferably no more than 3 moles of cations
/L-H2O and particularly preferably no more than 2 mol metal
ion/L-H2O is used from the standpoint of economics and
because an excessive add-on in the absence of a water rinse
can cause a deterioration in the heat-exchange
performance. It is possible to use a slurry, for example,
milk of lime, as long as some degree of solubility exists.
While no rigorous restriction applies to pH of the
solution, one should avoid strongly acidic solutions
capable of decomposing the silicic acid salts of
multivalent metals, and the use of aqueous solutions with
a pH of 3 to 13 is preferred, while a pH of 4 to 12 is even
more preferable.
As long as the effect of treatment according to the
application under consideration is not hindered, the
aqueous multivalent metal salt solution may contain various
additives. For example, in addition to surfactants,
defoamers, antimicrobials, fragrances, colorants, and the
like, when treating a surface bearing a chromic
acid/chromate conversion treatment, one may find it
effective to add a Cr6 reductant, for example, hydrazine
salts, to reduce chromium elution. Furthermore, when the
aqueous multivalsnt metal salt solution is to be roll
coated on flat aluminum sheet, the addition of a thickener,
leveling agent, surfactant, or the like may be useful.
When a slurry or aqueous solution of calcium hydroxide is
used, a hydroxyl group-containing organic compound can also
usefully be added in order to increase the solubility.
The time and temperature of treatment may be varied
within wide limits. Short times at high temperatures may
be used, but generally treatment at ambient temperature is
preferred because of its lower costO
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The present invention is explained further in the
following illustrative but not limiting examples, in which
the ~ollowing measurement methods were used:
Contact anqle (hydrophilicityl. The contact
angle for small (l to 2 mm diameter) water droplets
placed on the solid surface was measured using a FACE
contact angle instrument (model CA-P from Kyowa Kaimen
Kagaku). The contact angle was measured shortly after
treatment of the samples according to this invention
(designated in the Table below as llinitial") and after
five cycles of immersion for eight hours in running
water at room temperature followed by drying for 16
hours at 80 C (designated in the following Table as
"after water wash").
Corrosion resistance. This was based on the
salt-spray test method of JIS Z-2371. The reported
value is the spray test period until the white rust
sur~ace area reached 5%.
Antimicrobial ac.tivitv. The treated aluminum to
be tested was cut into a 30 mm x 30 mm square and
after immersion in running water for 1 week, was heat
sterilized. This was fixed in the center of agar
culture medium in a 90 mm petri dish. One mL of a
microbial suspension, previously obtained by culturing
the isolate from the adhered material on the surface
of a heat exchan~er, was uniformly spread on the test
specimen and the culture medium surface. Scoring was
performed, aft~r incubation for 3 weeks at 28 C,
according to the following table:
score rowth
0 no growth
l very little growth
2 small amount of growth
3 moderate growth
4 heavy growth
Initial Odor. This odor, which is believed due
to volatilization of chemicals used in treatment, was
1 3 1 957 1
evaluated on a 5 point-scale by ten individuals who
smelled humid air directed onto the treated sheet. A
maximum score of 5 was allowed for the minimal amount
of odor produced by a completely untreated aluminum
sheet, while a minimum score of 1 was assigned to the
unpleasant odor produced with a sheet subject~d to a
chromate treatment, then waterglass treatment (without
any boron containing chemical mixed with the
waterglass), then nitric acid treatment.
Bondinq. Cellophane adhesive tape was adhered on
the hydrophilic film and then quickly stripped off,
and the ~xternal appearance was then ~valuated.
Lubricating oil_ coatability (processability).
The status of the oil coating was visually evaluated
after immersion in Panting Oil AF-8F (from Idemitsu
Sekiyu Kabushiki Kaisha) and stan~ing for 1 minute.
ExamPle 1
An aqueous mixed solution (7% nonvolatiles) of 100
parts (based on solids) potassium waterglass tsio2/x2o
molar ratio = 3~ and 35 parts potassium borate was coated,
in a quantity affording a dry film thickness of O.4
micrometers, on the surface of A-1100 aluminum sheet (0.1
mm thick). This was dried Eor 3 minutes in a 200 degrees
Centigrade oven.
- 25 This sheet was then dipped for 30 seconds in a 3 %
aqueous solukion of calcium nitrate, rinsed, and finally
dried for 2 minutes in a 200 degrees Centiyrade oven.
Example 2
This was the same as Example 1, except that before
beginning the treatments described in ~xample 1, the
aluminum surface was treated with chromic acid/chromate and
then coated with a water-soluble polyurethane ~Elastron~
A-42 from Daiichi Kogyo Seiyaku Company, Limited). Drying
for 3 minutes at 200 degrees Centigrade gave a film
thickness of approximately 0.3 microns. This then received
the same hydrophilicizing treatment solution as in Example
1, followed again by the same calcium nitrate solution dip
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as above.
Examples 3 throuqh 6
These were treated in the same general way as Examples
1 and 2, but with the variations in materials used as shown
in Tabla 1.
Example 7
A chromic acid/chromate-treated aluminum heat
exchan~er was dipped into an aqueous mixed solution having
5 % total non volatiles, the non volatiles consisting of
100 parts waterglass no. 3, 40 parts sodium metaborate, and
60 parts sodium polyacrylate. A good solution uptake was
found upon withdrawal. The treated heat exchanger was then
dried for 5 minutes at 200 degrees Centigrade, immersed for
1 minute in a 3% solution of calcium nitrate, withdrawn,
and finally dried for 2 minutes in a 200 degrees Centigrade
oven.
Comparison Examples 1 and 2
Treatment followed the procedure of Example 1 or 2,
respectively, but with the omission of the potassium
borate.
Comparison Example 3
Treatment followed the procedure of Example 1, but
with the omission of treatment with the aqueous calcium
nitrate solution.
Comparison Example 4
Treatment followed the procedure of Example 3, but
using phosphoric acid in place of the magnesium nitrate.
Comparison Example 5
Treatment followed the procedure of Example 4, with
the exceptions that the addition of potassium borate was
omitted and a nitric acid rinse was executed in place of
- the aqueous barium nitrate rinse.
Comparison Example 6
Treatment followed the procedure of Example 4, with
the exceptions that the aqueous barium nitrate rinse was
omitted and an aqueous slurry of barium metahorate was used
in place of the potassium borate of Example 1.
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27587-4
Comparison Example 7
Treatment followed the procedure of Example 7 with the
exceptions that the addition of sodium metaborate was
- omitted and a phosphoric acid rinse was executed in place
of the aqueous calcium nitrate rinse.
The heat exchangers used in Example 7 and the present
comparison example were respectively installed in air
conditioners, each then received 2 mL of the microbial
- suspension described above for the antimicrobial test, and
each was then sprayed with approximately 10 mL of warm
culture solution (100 mL water, 4 g glucose, 1 g peptone,
and 0.5 g agar). After standing for 24 hours, each was
then run through 10 cycles where 1 cycle comprised 1 hour
of air cooling, 6 hours standing at room temperature, 1
hour of air cooling, and 16 hours standing at room
temperature. The odor at the start of air-conditioner
~ operation was then evaluated by 10 people, on a scale
running from 1 point for a highly objectionable odor to a
maximum of 5 points for minimal odor, similar to that used
for scoring initial odor as described above. The average
odor score for Comparison Example 7 was 2.3 points, against
an average of 3.8 for Example 7 according to the inventlon.
Some results for Examples 1 through 7 and Comparison
Examples 1 through 7 are collectively reported in the
second part of Table 1. As a comparison of Examples 1
through 7 with Comparison Examples 1 through 7 makes cl~ar,
the invention of the pr~sent application not only affords
an excellent hydrophilicity, corrosion resista~ce, initial
odor resistance, bonding, and lubricating oil coatability,
but also has longer lasting hydrophilicity and an excsllent
antimicrobial performance.
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1 3 1 957 1
Table 1.
, ..
No. alurNnum substrate for borate post-treatment
hydrophilicizing aclditive rinse
trea tment
Example ~ no pretreatment sheet potassium borate calcium nitrate
xample 2 chromic acid/chromate sheet potassium borate calcium nitrate
+ primer
Example 3 phosphoric acid/chromate sheet potassium borate magnesium nitrate
Example 4 chrornic acid/chrornate shees potassium borate barium nitrate
Example 5 chromic acid/chromate sheet potassium borate calcium hydroxide
Example 6 chromic acid/chromate sheet potassium borate zinc - acetate
xample 7 chrornic acid/chromate heat sodium metaborate calcium nitrate
exchang~
Comparison
Examples
no pretreatment sheet _ calcium nitrate
2 chromic acid/chromate sheet _ calcium nitrate
+ primer
3 no pretreatment sheet potassium borate
4 phosphoric acid/chromate sheet potassium borate phosphoric acid
chrornicacid/chrornatesheet _ nitric acid
6 chromic acid/chromate sheet barium metaborate
7 chromic acid/chromate heat _ phosphoric acid
. _ _ exchanger
(continued on the next page)
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Tablel. (continued from rcvious a
No. hydrophilicity conoslonini tial antimicrobial bond- lubricating
(contact angle) resistance c,dor performance ability oil
coatability
ini tial wash (hours)
Example I < 5o< 10 -15 192 4 ~ 5 I ~ +
Example 2 < 5o< 5O -10 > 480 5 I +
Example 3 < 5o< 5O ~ IOO 384 3 ~ 4 I ~ +
Example 4 < 510 ~ 15 > 4804 ~ 5 I + +
Example 5 ~ 5o< 5 ~ 10 > 480 5 I + +
Example 6 < 5o10 ~ 15 > 480 4 0~1 + +
Example 7 < 5~~ 5 ~ 10 > 480 4 (3.8j~
Comparison
Examples
<5<10~15 t68 3~4 3~~ +
2 <5< 5~15 >480 4 3-4 .~ +
3 < 515 ~20 120 3 2~3 x x
4 <5 10~15 360 2 4 ~
< 515 ~ 20> 480 I 3~4 x +
6 < 515 ~ 20> 480 3 2 x x
~ 510 ~ 15> 480 :2 -3(2.3)" _
(note) ~The evaluation method consisted of evaluation by odor and thus differed ~rom the other
examples and comparison examples.
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