U.S. patent application number 10/508583 was filed with the patent office on 2005-07-14 for hydrophilic film, process for producing the same, and paint for formation of hydrophilic film.
This patent application is currently assigned to SUMITOMO OSAKA CEMENT CO.. Invention is credited to Maeda, Daisaku, Shigeru, Keijiro.
Application Number | 20050154112 10/508583 |
Document ID | / |
Family ID | 28456302 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050154112 |
Kind Code |
A1 |
Shigeru, Keijiro ; et
al. |
July 14, 2005 |
Hydrophilic film, process for producing the same, and paint for
formation of hydrophilic film
Abstract
The present invention provides a hydrophilic film, which
displays excellent hydrophilicity, and also displays excellent
durability with respect to acidic, neutral, and alkaline detergents
and chemicals. A hydrophilic film of the present invention
comprises a double oxide of silicon and zirconium, an alkali metal,
and water. Furthermore, the film may also comprise aluminum or a
bivalent metal, and may also contain at least one of a silane
coupling agent and an acrylic resin.
Inventors: |
Shigeru, Keijiro;
(Funaba-shi, JP) ; Maeda, Daisaku; (Shiroi-shi,
JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
SUMITOMO OSAKA CEMENT CO.,
Tokyo
JP
|
Family ID: |
28456302 |
Appl. No.: |
10/508583 |
Filed: |
September 22, 2004 |
PCT Filed: |
March 27, 2003 |
PCT NO: |
PCT/JP03/03855 |
Current U.S.
Class: |
524/430 |
Current CPC
Class: |
C03C 17/008 20130101;
C03C 2218/113 20130101; C09D 1/00 20130101; C03C 2217/23 20130101;
C03C 2217/29 20130101; C03C 17/009 20130101; C23C 30/00 20130101;
C03C 2217/22 20130101; C03C 2217/213 20130101; C03C 17/25 20130101;
C23C 26/00 20130101; C09D 5/38 20130101 |
Class at
Publication: |
524/430 |
International
Class: |
C08K 003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2002 |
JP |
2002-089158 |
Nov 5, 2002 |
JP |
2002-321172 |
Claims
1. A hydrophilic film either comprising a double oxide of silicon
and zirconium, and water, or alternatively, comprising a mixture of
oxides of silicon and zirconium, and water.
2. A hydrophilic film according to claim 1, further comprising an
alkali metal or silver.
3. A hydrophilic film according to claim 1, further comprising
aluminum.
4. A hydrophilic film according to claim 1, comprising a bivalent
metal.
5. A hydrophilic film according to claim 1, comprising at least one
of a silane coupling agent and a resin.
6. A coating material for forming a hydrophilic film, comprising a
silicon component, a zirconium component, and water.
7. A coating material for forming a hydrophilic film according to
claim 6, further comprising an alkali metal or silver
component.
8. A coating material for forming a hydrophilic film according to
claim 7, comprising at least one of an aluminum component, a
bivalent metal component, a silane coupling agent, and a resin.
9. A process for producing a hydrophilic film comprising the steps
of applying a coating material for forming a hydrophilic film
according to claim 6 to a substrate, and conducting a hydration
reaction.
10. A hydrophilic film according to claim 2, further comprising
aluminum.
11. A coating material for forming a hydrophilic film according to
claim 7, comprising at least one of an aluminum component, a
bivalent metal component, a silane coupling agent, and a resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to a hydrophilic film formed
on the surface of a variety of metal, organic or inorganic
materials, for the purposes of protecting the material surface and
suppressing the adhesion of soiling to the material surface, and
relates particularly to a hydrophilic film with superior
characteristics, which does not degrade or separate even when
washed with detergents.
BACKGROUND ART
[0002] Conventional methods for hydrophilizing the surfaces of
materials include (1) applying a surfactant, (2) applying a water
absorbing resin, (3) applying a hydrophilic photocatalyst, (4)
forming either an inorganic coating by enameling or ceramic thermal
spraying, or a silica film, and (5) mixing a hydrophilic component
with a resin coating agent. For example, Japanese Unexamined Patent
Application, First Publication No. 2000-191960 discloses a
hydrophilic coating that uses a photocatalyst.
[0003] However, films formed by these methods suffer from a number
of drawbacks, including poor durability with respect to
detergents.
[0004] In other words, in the method (1), which involves applying a
surfactant, because the surfactant is water soluble, the effect is
lost within a short period of time in the presence of water or
detergents. In the method (2), which involves applying a water
absorbing resin, the resin is acidic, and consequently degrades in
the presence of alkaline detergents. In the method (3), which
involves applying a hydrophilic photocatalyst, satisfactory effects
cannot be achieved in darker locations, and moreover, the silica
binder used to fix the photocatalyst is alkaline, and degrades in
the presence of neutral detergents. In the method (4), which
involves forming an inorganic coating, only heat resistant
materials can be treated by enameling or thermal spraying, and the
resulting coatings also display poor impact resistance.
Furthermore, silica films degrade in the presence of neutral or
alkaline detergents. In the method (5), which uses a resin coating
agent, the resin degrades in the presence of acidic or alkaline
detergents.
[0005] The present invention takes the above problems into
consideration, with an object of providing a hydrophilic film which
displays excellent hydrophilicity, and also displays excellent
durability with respect to acidic, neutral, and alkaline detergents
and chemicals.
DISCLOSURE OF INVENTION
[0006] A hydrophilic film of the present invention either comprises
a double oxide of silicon and zirconium, and water, or
alternatively, comprises a mixture of oxides of silicon and
zirconium, and water, and preferably also comprises an alkali
metal. Of the possible configurations, a hydrophilic film
comprising a double oxide of silicon and zirconium, water, and an
alkali metal is preferred.
[0007] In addition, the film preferably also comprises aluminum or
a bivalent metal described below. Alternatively, the film may also
comprise at least one of a silane coupling agent and a resin.
[0008] A hydrophilic film of the present invention can be used for
coating all manner of materials, including inorganic materials
(such as glass, pottery, porcelain, concrete or stone), metallic
materials (such as stainless steel, aluminum, gold, silver,
titanium, and any of the various plated metals), and organic
materials (such as plastics and fibrous products).
[0009] A coating material for forming a hydrophilic film of the
present invention comprises a silicon component, a zirconium
component, and water. Furthermore, the coating material preferably
also comprises an alkali metal component, and preferably also
comprises at least one of an aluminum component, a bivalent metal
component, a silane coupling agent, and a resin.
[0010] A process for producing a hydrophilic of the present
invention involves applying an aforementioned coating material for
forming a hydrophilic film of the present invention to a substrate,
and conducting a hydration reaction.
BEST MODE FOR CARRYING OUT THE INVENTION
[0011] A hydrophilic film of the present invention either comprises
a double oxide of silicon and zirconium, and water, or
alternatively, comprises a mixture of oxides of silicon and
zirconium, and water, and preferably also comprises an alkali metal
or silver. The term alkali metal refers to lithium (Li), sodium
(Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr).
Furthermore, in this description, the term water does not refer to
simple liquid water, but describes solidified water generated by a
hydration reaction, such as crystal water.
[0012] A preferred embodiment of a hydrophilic film of the present
invention, comprising a double oxide of silicon and zirconium, an
alkali metal or silver, and water, is expressed by a chemical
formula M(SiO.sub.m).sub.x(ZrO.sub.n).sub.y(H.sub.2O).sub.z. In
this formula, m and n are arbitrary numbers from 1 to 4, x+y=1, and
z is an arbitrary number. Furthermore,
M=Li.sub.aNa.sub.bK.sub.cRb.sub.dCs.sub.eFr.sub.fAg.- sub.g
(wherein, a, b, c, d, e, f and g each represent arbitrary numbers,
and all of a, b, c, d, e, f and g may be 0). A film of this
composition displays excellent durability with respect to various
detergents. Furthermore, because the alkali metal ions or silver
ions attract water molecules, the film also displays excellent
hydration characteristics. This attracted water imparts
hydrophilicity to the film. Furthermore, at least one of lithium
(Li), sodium (Na) and potassium (K) is preferably used as the
alkali metal. By also incorporating silver, antibacterial
properties can also be imparted to the film.
[0013] Another preferred embodiment of a hydrophilic film of the
present invention comprises a mixture of oxides of silicon and
zirconium, and water, and this embodiment is expressed by the
chemical formulas M(SiO.sub.m).sub.x(H.sub.2O).sub.z1 and
M(ZrO.sub.n).sub.y(H.sub.2O).sub.- z2, wherein the hydrophilic film
is formed from a mixture of these two materials. In these formulas,
m and n are arbitrary numbers from 1 to 4, and z1 and z2 are
arbitrary numbers. Furthermore, M=Li.sub.aNa.sub.bK.sub-
.cRb.sub.dCs.sub.eFr.sub.fAg.sub.g (wherein, a, b, c, d, e, f and g
each represent arbitrary numbers, and all of a, b, c, d, e, f and g
may be 0).
[0014] Because a hydrophilic film of the present invention is
either a film of a double oxide of silicon and zirconium, or a film
of a mixture of oxides of silicon and zirconium, the zirconium
strengthens the cross-linking of the silicon, and as a result, the
film displays superior durability with respect to acid and alkali,
when compared with films of silicon oxide or zirconium oxide, or
films formed by simply mixing the two oxides.
[0015] The weight proportion within a hydrophilic film of the
present invention accounted for by silicon oxide is preferably
within a range from 1 to 90%, and even more preferably from 50 to
70%. If the proportion is less than 1%, then adequate
hydrophilicity cannot be obtained, whereas if the proportion
exceeds 90%, then a satisfactory level of alkali resistance cannot
be achieved.
[0016] The weight proportion within a hydrophilic film of the
present invention accounted for by zirconium oxide is preferably
within a range from 1 to 90%, and even more preferably from 20 to
40%. If the proportion is less than 1%, then a satisfactory level
of alkali resistance cannot be achieved, whereas if the proportion
exceeds 90%, then the hydrophilicity deteriorates.
[0017] Furthermore, the weight ratio between the silicon oxide and
the zirconium oxide is preferably within a range from 10:1 to 1:10,
and even more preferably from 7:2 to 5:4.
[0018] The weight proportion within a hydrophilic film of the
present invention accounted for by alkali metals or silver is
preferably within a range from 0.1 to 10%. If the proportion of
alkali metals or silver is less than 0.1%, then the hydrophilicity
deteriorates, whereas if the proportion exceeds 10%, the alkali
resistance deteriorates.
[0019] The weight proportion within a hydrophilic film of the
present invention accounted for by water is preferably within a
range from 1 to 70%, and even more preferably from 5 to 50%. The
water within the film is water that has been bound by a hydration
reaction, such as crystal water, and cannot be easily volatilized
like liquid water. However, the water need not necessarily be
crystallized.
[0020] Furthermore, this type of hydration reaction is extremely
important in manifesting curing and strength within the film, as is
observed in the curing of cement. Furthermore, this water is also
an extremely important component in the manifestation of
hydrophilicity. If the proportion of water is less than 1%, then
the hydrophilicity is unsatisfactory, whereas if the proportion of
water exceeds 70%, then an undesirable decrease in film hardness is
observed.
[0021] Furthermore, a hydrophilic film of the present invention
also displays a soap scum adhesion prevention effect, and in those
cases where this soap scum adhesion prevention effect is a
priority, the weight ratio between the silicon oxide and the
zirconium oxide within the hydrophilic film of the present
invention is preferably within a range from 7:3 to 3:7. The reason
for this requirement is due to the fact that soap molecules
comprise both hydrophilic groups and lipophilic groups within the
same molecule. In other words, it is thought that when soap acts
upon dirt or soiling, organic soiling such as oils adsorb mainly to
the lipophilic groups, whereas inorganic materials within sweat and
the like adsorb to the hydrophilic groups, and subsequent complex
crossing causes insoluble soap scum.
[0022] Hence, soap scum has a complex structure, and as a result,
is quite different from normal soiling. Because silica is strongly
hydrophilic, if the number of hydrophilic groups within the soap
scum is low, then the scum will not adhere to the silica. However,
if the soap scum contains a large quantity of hydrophilic groups,
then the soap scum will bond easily to the surface of the silica.
As a result, simply ensuring a strong level of hydrophilicity is
not sufficient to adequately prevent the adhesion of soap scum.
[0023] On the other hand, although zirconia is an inorganic
material, it is strongly lipophilic, and will not adhere very well
to the hydrophilic groups within soap scum, meaning that even if
the soap scum contains a large quantity of hydrophilic groups, it
will not bond to the surface of the zirconia. However, if the soap
scum contains a large quantity of lipophilic groups, then these
will bond readily, meaning simply ensuring a strong level of
lipophilicity is not sufficient to always prevent the adhesion of
soap scum.
[0024] Accordingly, effective soap scum adhesion prevention can be
achieved by mixing silica and zirconia, which display reciprocal
properties, and preferably by using either a nano level mixture of
alkoxides or a double oxide. A soap scum adhesion prevention effect
is exhibited, to some extent, by a film comprising a mixture of a
silicon oxide and a zirconium oxide, although if a double oxide of
the two elements is formed, or additives such as alkali metals,
alkali earth metals, zinc or copper are added to form a hydrate,
then the soap scum adhesion prevention effect is enhanced, and
provides even better durability.
[0025] In addition to the components described above, a hydrophilic
film of the present invention may also comprise either aluminum or
a bivalent metal. The bivalent metal is preferably selected from
amongst the alkali earth metals, namely, Ca, Sr, Ba, Ra, Be and Mg,
as well as Zn, Cu(II), Fe(II), Ni(II) and Mn(II). Incorporating
this type of metal component improves the strength of the film. It
is thought that the reason for this observation is that network
structures comprising the aforementioned mixed oxide of silicon and
zirconium, alkali metal ions and water can be cross-linked by using
these metal additives. Furthermore, the bivalent metal is
preferably at least one metal selected from a group consisting of
the alkali earth metals, Zn and Cu(II). In the case of Fe, a
similar effect can be achieved even with a metal component that is
not bivalent.
[0026] The weight proportion within a hydrophilic film of the
present invention accounted for by aluminum is preferably within a
range from 0.1 to 10%. If the weight proportion of aluminum is less
than 0.1%, then no differences are discernible from the case in
which no aluminum is added, whereas if the weight proportion of
aluminum exceeds 10%, the hydrophilicity deteriorates
undesirably.
[0027] The weight proportion within a hydrophilic film of the
present invention accounted for by bivalent metals is preferably
within a range from 0.1 to 10%. If the weight proportion of
bivalent metals is less than 0.1%, then no differences are
discernible from the case in which no such metals are added,
whereas if the weight proportion of bivalent metals exceeds 10%,
the hardness deteriorates undesirably.
[0028] Furthermore, if required, silver may also be added to impart
antibacterial properties to the film.
[0029] If, in addition to the components described above, at least
one of a silane coupling agent and a resin is added, then the
adhesion between the film and the coated target surface can be
improved. The resin can be any material typically called a resin,
and there are no particular restrictions, although acrylic resins
are preferred. There are no particular restrictions on the acrylic
resin, and any resin typically called an acrylic resin can be used.
Suitable examples include polyacrylic acid, which is a polymer of
acrylic acid, polymethacrylic acid, which is a polymer of
methacrylic acid, as well as polymers of acrylic acid derivatives,
polymers of methacrylic acid derivatives, and copolymers of such
monomers. It is thought that the reason for the improvement in
adhesion is the fact that a polymer such as polyacrylic acid acts
effectively in improving the bonding between inorganic components
and the coating target surface. In addition to acrylic resins,
other resins such as urethane resins, melamine resins, epoxy
resins, silicone resins, and fluororesins can also be used. Of
these resins, aqueous type resins that are capable of mixing with
water are preferred.
[0030] The weight proportion within a hydrophilic film of the
present invention accounted for by at least one of a silane
coupling agent and a resin is preferably within a range from 1 to
10%.
[0031] A silane coupling agent is an organic silane compound
represented by a general formula R.sup.1Si(OR).sub.3 (wherein
R.sup.1 is an organic substituent), and preferred examples include
trimethoxyphenylsilane, trimethoxymethylsilane,
vinyltriethoxysilane, 3-methacryloxypropyltrimeth- oxysilane,
3-glycidoxypropultrimethoxysilane and 3-aminopropyltriethoxysil-
ane. Because a silane coupling agent has the effect of bonding
organic resins and inorganic materials, it can be favorably
combined with other resin components. The introduction of
polyacrylic acid or a copolymer or derivative thereof, or
alternatively, itaconic acid or methacrylic acid is ideal. Acrylic
acid and methacrylic acid are preferably introduced in the form of
water co-soluble derivatives such as acrylic-melarnine copolymers,
2-hydroxyethyl methacrylate and glycidyl methacrylate.
[0032] The thickness of a hydrophilic film of the present invention
is typically within a range from 0.01 to 5 .mu.m, and preferably
from 0.1 to 1.0 .mu.m. If the film is thinner than 0.01 .mu.m, then
little hydrophilic effect is realized, whereas if the thickness
exceeds 5 .mu.m, the film becomes prone to peeling or
separation.
[0033] Furthermore, in those cases where the soap scum adhesion
prevention effect is a priority, the thickness of the hydrophilic
film of the present invention is typically within a range from 0.05
to 5 .mu.m, and preferably from 0.1 to 1.0 .mu.m. If the film is
thinner than 0.05 .mu.m, then only a minimal soap scum prevention
effect is realized, whereas if the thickness exceeds 5 .mu.m, the
film becomes prone to peeling or separation.
[0034] A hydrophilic film of the present invention helps prevent
the adhesion of the type of soiling formed on all manner of
materials, and can be used in kitchen products such as sinks,
bathroom products, and washing machines and the like. Particularly
when used in washing machines, laundry sinks, wash basins, bath
tubs, around drain holes, and on faucet fitting and pipes, the film
is able to prevent not only oil-based soiling, but also the
adhesion of soap scum.
[0035] Next is a description of a process for forming a hydrophilic
film of the present invention. This process presents a preferred
method of forming a hydrophilic film of the present invention,
although the hydrophilic film of the present invention is not
restricted to films formed using this process.
[0036] A hydrophilic film of the present invention is formed by
applying a liquid coating material comprising the various
components, and then drying and heating the applied coating. The
raw materials for each component are preferably solutions or liquid
dispersions.
[0037] The silicon raw material is preferably a water soluble salt
such as an alkali silicate, a colloidal silica (silica sol), or a
silicon alkoxide such as ethyl silicate. In those cases where an
alkoxide is used, the alkoxide is preferably first hydrolyzed in
the presence of water (acid or alkali) to form a sol, as this
yields a more favorable film.
[0038] The zirconium raw material is preferably a water soluble
salt such as zirconium oxychloride or zirconium oxynitrate, an
alkoxide such as zirconium tetrabutoxide or a hydrolysis product
thereof, or a zirconia sol.
[0039] The alkali metal raw material preferably uses a water
soluble salt such as a nitrate, a chloride, or an organic acid salt
of the alkali metal. Furthermore, salts such as lithium silicate or
lithium zirconate that also contain another component of the
hydrophilic film of the present invention are ideal.
[0040] The silver raw material preferably uses either a water
soluble salt such as silver nitrate or an organic acid salt, or a
silver colloid.
[0041] The aluminum raw material is preferably a water soluble salt
such as aluminum nitrate or chloride, an alkoxide such as aluminum
isopropoxide or a hydrolysis product thereof, or an alumina
sol.
[0042] The bivalent metal raw material is preferably a water
soluble salt such as a nitrate or a chloride of the bivalent
metal.
[0043] The silane coupling agent or resin component is preferably
selected from the materials described above, and of these, acrylic
resins are particularly preferred. Furthermore, the water component
may use the water used in the aqueous solutions of the
aforementioned components, the water used in hydrolyzing an
alkoxide, or water vapor from the air, or alternatively, additional
water may also be added.
[0044] Each of these raw materials is weighed in advance to ensure
a composition with predetermined proportions of each component. In
order to make the coating process easier, the composition is
preferably prepared as a coating material using any of a variety of
organic solvents. Other than water, suitable organic solvents
include those solvents that are miscible with water such as
alcohols and ketones. During preparation, in order to prevent
precipitation or condensation, either an acid is added to adjust
the pH to an appropriate level, or the quantity of water used is
adjusted as appropriate. A volatile acid is preferred as the acid.
Nitric acid, hydrochloric acid and acetic acid are ideal. If acid
is not added, then a hydration reaction can proceed within the
coating material, causing the coating material to harden prior to
application. At lower pH values, the hydration reaction is
extremely slow, meaning this type of hardening prior to application
does not occur.
[0045] There are no particular restrictions on the solid fraction
concentration within the coating material, although values from 0.1
to 10% are preferred.
[0046] The respective weight proportions for the silicon component
and the zirconium component within the coating material, calculated
as oxides, are preferably within a range from 0.1 to 9% for silicon
oxide, and from 0.1 to 9% for zirconium oxide. Furthermore, the
weight proportion of the alkali metal or silver component is
preferably within a range from 0.01 to 1%.
[0047] In addition, in those cases where at least one of aluminum,
a bivalent metal, a silane coupling agent and a resin is added, the
respective weight proportions within the coating material are
preferably from 0.01 to 1% for aluminum, from 0.01 to 1% for the
bivalent metal, from 0.1 to 1% for the silane coupling agent, and
from 0.1 to 1% for the resin. Furthermore, the coating material
should contain a sufficient quantity of water for the hydration
reaction.
[0048] The weight ratio between the silicon component and the
zirconium component within the coating material, calculated as
oxides, is preferably within a range from 10:1 to 1:10.
Furthermore, in order to achieve an even better hydrophilic effect,
weight rations from 7:2 to 5:4 are even more desirable.
Furthermore, in those cases where the soap scum adhesion prevention
effect is a priority, weight ratios from 7:3 to 3:7 are the most
desirable.
[0049] Furthermore, the weight proportion of the alkali metal or
silver component within the coating material, calculated as an
oxide and calculated relative to the combined weight of the silicon
component and the zirconium component when calculated as oxides, is
preferably within a range from 0.1 to 5% by weight.
[0050] Furthermore, the weight proportion of the aluminum component
within the coating material, calculated as an oxide and calculated
relative to the combined weight of the silicon component and the
zirconium component when calculated as oxides, is from 0.1 to 5% by
weight.
[0051] Furthermore, the weight proportion of the bivalent metal
within the coating material, calculated as an oxide and calculated
relative to the combined weight of the silicon component and the
zirconium component when calculated as oxides, is also preferably
from 0.1 to 5% by weight.
[0052] A coating material prepared in this manner can be applied
and heated to form a film. Suitable application methods include
dipping, spraying and brush coating methods, although there are no
particular restrictions on the method used. Similarly, there are no
particular restrictions on the heating method employed, although
heating to a temperature of 100 to 300.degree. C. is preferred as
it promotes the volatilization of the acid. As the acid
volatilizes, the pH rises, thus accelerating the hydration reaction
and promoting curing. Furthermore, the organic solvent also has the
effect of terminating the hydration reaction, and because the
organic solvent also evaporates during the heating stage, this also
accelerates the hydration reaction. Furthermore, in those cases
where, for some reason, heating is not possible, leaving the film
to stand for an extended period at room temperature will also
result in evaporation of the acid and the organic solvent, causing
the hydration reaction to proceed, and the curing process to also
proceed gradually. In those cases where curing is unsatisfactory,
water is preferably applied to the film to supplement the water
component. When supplying water in this manner, supplying an
aqueous solution containing bivalent or higher inorganic anions is
particularly preferred. Specifically, if the coating material is
applied, and following drying, an aqueous solution comprising
bivalent or higher anions, including sulfur-containing ions such as
sulfate ions, silicon-containing ions such as silicate ions,
phosphorus-containing ions such as phosphate ions,
aluminum-containing ions such as aluminate ions, carbonate ions,
zirconium-containing ions such as zirconate ions, or
boron-containing ions such as borate ions, is then applied to the
film by spraying or the like, the curing of the film can be
accelerated. It is thought that this phenomenon occurs because the
above types of ions accelerate the hydration reaction, thereby
enabling curing to proceed at normal temperatures. When a coating
material of the present invention is used on a washing machine or a
laundry sink or the like, because the above types of components are
incorporated within soaps and detergents, using the device actually
causes the curing of the film to be accelerated.
[0053] The curing mechanism relies on the hydration reaction, which
accelerates with the pH rise that accompanies the evaporation of
the volatile acid added to the coating liquid used for forming the
film. The progression of this hydration reaction is the principle
used in the curing of cement. This reaction causes water to become
incorporated within the cured film, thus providing excellent
hydrophilicity, and as this reaction proceeds, the mixed oxide is
gradually produced. In a normal sol gel reaction, hydrolysis occurs
with an acid catalyst, and curing proceeds via a subsequent
dehydration condensation reaction, which is very different from the
curing reaction of the present invention in terms of the movement
of water.
[0054] Furthermore, it is thought that the reason that a
hydrophilic film of the present invention displays excellent
durability with respect to a variety of detergents is the inclusion
of zirconium. However, the zirconium component displays poor
hydrophilicity, meaning the zirconium component alone is unable to
produce a hydrophilic coating. Only by adding a silica component
and an alkali metal to the zirconium component, and then promoting
hydration and curing by volatilizing the acid, can a highly durable
film with excellent hydrophilicity be obtained.
[0055] Applying a coating material for forming a hydrophilic film
of the present invention to the surface of any of a variety of
materials to form a film helps prevent the adhesion of soiling to
all manner of materials, and as such, the coating material can be
used in kitchen products, bathroom products, and washing machines
and the like. Particularly when used in washing machines, laundry
sinks, wash basins, bath tubs, around drain holes, and on faucet
fitting and pipes, the coating material is able to prevent not only
oil-based soiling, but also the adhesion of soap scum. Furthermore,
because application of the coating material enables the formation
of a hydrophilic film, a film that helps prevent the adhesion of
soiling can be formed on the surface of all manner of molded
materials.
EXAMPLES
[0056] As follows is a more detailed description based on a series
of examples, although the present invention is in no way restricted
to the examples presented below.
Example 1
Preparation of a Film on a Glass Plate
[0057] To 10 g of tetraethoxysilane were added 80 g of ethanol, 9 g
of butoxyethanol, and 1 g of a 1% aqueous solution of nitric acid,
and the mixture was then heated at 60.degree. C. with stirring for
24 hours to allow the hydrolysis reaction to proceed, yielding a
silica sol solution. Next, 1 g of zirconium oxynitrate, 0.1 g of
aluminum nitrate, 0.1 g of zinc nitrate, 1 g of lithium nitrate,
and 1 g of polyacrylic acid were dissolved in water and the
solution was made up to 100 g. 50 g of each of the two solutions
were then mixed together, and the pH was adjusted to pH1 using
nitric acid, thus yielding a coating material. The solid fraction
concentration of this coating material was approximately 5%, and
the chemical composition (weight ratios) of this solid fraction on
heating to 300.degree. C., determined using wet chemical analytical
methods, was SiO.sub.2: 58%, ZrO.sub.2: 11%, Al.sub.2O.sub.3: 0.4%,
ZnO.sub.2: 0.8%, Li.sub.2O: 4%, H.sub.2O: 7%, and polyacrylic acid:
19%. The heated product contained 7% water, and because this water
had not evaporated even at 300.degree. C., it is thought to
represent solidified water of hydration. Furthermore, the results
of X-ray diffraction showed no particular crystalline materials,
indicating an amorphous mixed oxide. Using a spray gun, the coating
material liquid was sprayed onto a glass plate that had been heated
to 300.degree. C., and water was then sprayed onto the plate, thus
forming a film of a detergent resistant hydrophilic coating with a
film thickness of 0.1 .mu.m on the surface of the glass plate.
Example 2
Preparation of a Film on a Stainless Steel Plate
[0058] To 10 g of zirconium tetrabutoxide were added 80 g of
isopropyl alcohol, 9 g of colloidal silica (a 30% aqueous
dispersion), and 1 g of lithium nitrate, and the pH was then
adjusted to pH1 using nitric acid, thus yielding a coating
material. The solid fraction concentration of this coating material
was approximately 6%, and the chemical composition (weight ratios)
of this solid fraction on heating to 200.degree. C., determined
using wet chemical analytical methods, was SiO.sub.2: 40%,
ZrO.sub.2: 40%, Li.sub.2O: 3%, and H.sub.2O: 7%. The heated product
contained approximately 7% water, and because this water had not
evaporated even at 200.degree. C., it is thought to represent
solidified water of hydration. Furthermore, the results of X-ray
diffraction showed no particular crystalline materials, indicating
an amorphous mixed oxide. This coating material liquid was applied
to a stainless steel plate using spraying, and was then heated at
200.degree. C. for 10 minutes, thus forming a film of a detergent
resistant hydrophilic coating with a film thickness of 0.2
.mu.m.
Example 3
Preparation of a Film on an Acrylic Sheet
[0059] 8 g of tetraethoxysilane, 1 g of trimethoxyphenylsilane, and
1 g of zirconium tetrabutoxide were dissolved in 45 g of isopropyl
alcohol, and 40 g of a 1% aqueous solution of sodium nitrate was
then added. An additional 5 g of 2-hydroxyethyl methacrylate was
then added, and the pH was adjusted to pH1 using hydrochloric acid,
thus yielding a coating material. The solid fraction concentration
of this coating material was approximately 8%, and the chemical
composition (weight ratios) of this solid fraction on heating to
100.degree. C., determined using wet chemical analytical methods,
was SiO.sub.2: 23%, ZrO.sub.2: 3%, Na.sub.2O: 2%, resin components:
50%, and H.sub.2O: 22%. The heated product contained 22% water, and
because this water had not evaporated even at 100.degree. C., it is
thought to represent solidified water of hydration. Furthermore,
the results of X-ray diffraction showed no particular crystalline
materials, indicating an amorphous mixed oxide. This coating
material liquid was applied to an acrylic sheet using a dipping
method, and was then heated at 100.degree. C. for 20 minutes, thus
forming a film of a detergent resistant coating with a film
thickness of 1.0 .mu.m.
Example 4
Hydrophilicity and Detergent Resistance
[0060] The contact angles for each of the films prepared in the
examples 1 to 3 are shown in Table 1. For reference purposes, the
contact angle of the substrate prior to coating is also shown. From
these results it is evident that the coating treatment of the
present invention is able to markedly increase the
hydrophilicity.
1 TABLE 1 Example 1 Example 2 Example 3 Contact angle following
coating 10.degree. 20.degree. 5.degree. Contact angle prior to
coating 50.degree. 70.degree. 80.degree.
[0061] Next, films prepared in the examples 1 to 3 were immersed in
an acidic detergent (brand name: Sanpol, manufactured by Dainihon
Jochugiku Corporation), a neutral detergent (brand name: Mama
Lemon, manufactured by Lion Corporation), and an alkaline detergent
(brand name: Kitchen Haiter, manufactured by Kao Corporation) for
one week, and the variation in contact angle was measured in each
case. Prior to measuring the contact angle, the films were washed
well with water to remove any residual detergent. From the results
in Table 2 it is very clear that each of the films displays
excellent detergent resistance.
2 TABLE 2 Example 1 Example 2 Example 3 Acidic detergent 10.degree.
20.degree. 5.degree. Neutral detergent 10.degree. 20.degree.
5.degree. Alkaline detergent 10.degree. 20.degree. 5.degree.
Example 5
Application of a Film to a Stainless Steel Washing Machine
[0062] The outside of the stainless steel tank of a washing machine
was treated with a film of the present invention. In order to
prepare the coating material for forming the film, first, 3 g of
zirconium butoxide and 3 g of tetraethoxysilane were dissolved in
44 g of isopropyl alcohol. Meanwhile, 0.2 g of lithium silicate and
1 g of silver nitrate were dissolved in 40 g of a 10% aqueous
solution of nitric acid, and 8.8 g of butyl cellosolve was then
added. The resulting solution was added gradually, with stirring,
to the previously prepared isopropyl alcohol solution, thus
yielding a coating material.
[0063] The weight ratio between silicon and zirconium within the
coating material, calculated as oxides, was 1:1. Furthermore, the
ratio between the lithium content of the coating material and the
combined weight of silicon and zirconium, calculated as the weight
of the respective oxides, was 1:20.
[0064] This coating material was sprayed onto the outside of the
stainless steel tank of the washing machine, was subsequently dried
at 200.degree. C. for 20 minutes, and was then cooled with water to
complete formation of the film. The thickness of the thus obtained
film was 0.2 .mu.m.
[0065] The weight ratio between silicon oxide and zirconium oxide
within the produced film was 1:1. Furthermore, the ratio between
lithium oxide and the combined weight of silicon oxide and
zirconium oxide, expressed as a weight ratio, was 1:20.
[0066] The washing machine containing this stainless steel tank,
and an untreated washing machine were used for a period of 1 year,
and the state of soap scum adhesion was then compared by visual
inspection. The untreated product displayed marked levels of soap
scum adhesion, and black mold was noticeable on one portion of the
tank. In contrast, the coated product showed no soap scum adhesion,
and no mold was visible.
Example 6
Formation of a Film on a Plated Faucet Fitting
[0067] A bathroom chrome-plated faucet fitting was treated with a
film of the present invention. In order to prepare the coating
material for forming the film, first, 0.5 g of zirconium butoxide
was dissolved in 49.5 g of ethanol. Meanwhile, 0.8 g of zirconium
oxynitrate and 0.2 g of calcium nitrate were dissolved in 40 g of a
1% aqueous solution of nitric acid, and 9 g of a 10% aqueous
dispersion of colloidal silica was then added. The resulting liquid
was added gradually, with stirring, to the previously prepared
ethanol solution, thus yielding a coating material.
[0068] The weight ratio between silicon and zirconium within the
coating material, calculated as oxides, was 2:1. Furthermore, the
ratio between the calcium content of the coating material and the
combined weight of silicon and zirconium, calculated as the weight
of the respective oxides, was 1:20.
[0069] The polished chrome-plated faucet fitting was immersed in
this coating material, and was then lifted out of the coating
material at a rate of 1 mm/second to complete the treatment. The
faucet fitting was then dried for 1 day at 20.degree. C. and then
sprayed with water. This operations was repeated 5 times, thus
forming a coating with a thickness of 3 microns.
[0070] The weight ratio between silicon oxide and zirconium oxide
within the produced film was 2:1. Furthermore, the ratio between
calcium oxide and the combined weight of silicon oxide and
zirconium oxide, expressed as a weight ratio, was 1:20.
[0071] The faucet fitting produced in this manner and an untreated
faucet fitting were used in a bathroom, and the state of soap scum
adhesion was then compared by visual inspection. After use for 1
month, the untreated product had a noticeable white film of adhered
soap scum, whereas on the treated product, almost no such adhesion
was visible. After 3 months, the untreated product displayed marked
adhesion of soap scum. In contrast, although the treated product
also showed some adhesion of soap scum, the level of adhesion was
less than that observed for the untreated product. When the two
faucet fittings were then wiped with a sponge, almost no soap scum
could be removed from the untreated faucet fitting, whereas in the
case of the treated faucet fitting, the soap scum was able to be
removed with ease. This observation was continued for a further 1
year, and similar results were observed.
[0072] This coating was cured at room temperature (25.degree. C.)
because the faucet fitting could not be heated. As described above,
this film displayed a favorable soap scum adhesion prevention
effect. If this film was rubbed strongly with a sponge then some
wearing of the film was noticeable, although there were no
particular abrasion problems associated with normal everyday use.
In these types of situations, where heating is not possible, even
curing of the coating at room temperature is able to produce a film
which, for normal use, provides a good soap scum adhesion
prevention effect.
Example 7
Paint Top Coat
[0073] The coating material prepared in the example 3 was applied,
by spray coating, to the surface of an aluminum plate that had
undergone acrylic melamine coating, and the coating material was
then heated at 150.degree. C. for 30 minutes, thus forming a film.
The thickness of the thus obtained film was 0.5 .mu.m. When this
aluminum plate was then exposed outdoors, a reduction in the types
of stains and streaks caused by rain was confirmed. It is thought
that this reduction is due to the fact that because the film is
hydrophilic, water droplets and streams tend to diffuse, making any
soiling less noticeable.
Example 8
Paint Undercoat
[0074] The coating material prepared in the example 1 was applied
to the surface of a zinc-plated pipe using dip coating, and was
then allowed to dry naturally, thus forming a film. When water was
then sprayed onto the film and subsequently dried, the adhesiveness
of the film increased. When a urethane based paint was applied over
the film and baked, a reduction in the number of typical defects
such as peeling was confirmed.
Example 9
Defogging Coating
[0075] The material prepared in the example 1 was applied to the
surface of a mirror using dip coating, and then dried using a
dryer, and when water was then sprayed onto the mirror and wiped
off with a towel, the film had cured to the extent that it was not
removed by the towel. The thickness of the film was 0.5 .mu.m. When
this mirror was used in a bathroom, no fogging of the mirror
occurred.
Example 10
Antistatic Coating
[0076] The coating material prepared in the example 3 was applied
to the surface of a polycarbonate sheet using spray coating, and
was allowed to dry naturally, and when water was then sprayed onto
the sheet and also allowed to dry naturally, the film had cured to
the extent that it was not removed by wiping with a towel. The
surface resistivity of polycarbonate is at least 10.sup.14 .OMEGA.,
but this value decreased to 10.sup.11 .OMEGA. with the coating
treatment of the present invention. Accordingly, this treatment
enabled a reduction in the electrostatic chargeability of the
polycarbonate surface, and dust was less likely to adhere to the
treated surface.
Example 11
Scorch Resistant Coating
[0077] When a lighted cigarette was pressed against the treated
polycarbonate sheet prepared in the example 10, it was confirmed
that the surface was more resistant to scorching. It is thought
that this finding is because the water of hydration within the
coating prevents large increases in the temperature. With a normal
untreated polycarbonate, scorching occurs readily with a lighted
cigarette.
Example 12
Drying Promoting Coating
[0078] The coating material prepared in the example 2 was applied,
by spray coating, to the surface of the stainless steel drum of a
clothes dryer, and was then heated at 200.degree. C., thus forming
a film of thickness 0.4 .mu.m. When the dryer was put to actual
use, the drying time for the surface of the stainless steel drum
fell to approximately half that of an untreated drum.
Example 13
Scratch Prevention Coating
[0079] When the surface of the stainless steel tank from the
example 12 was inspected for scratches, it was clear that the
quantity of scratches within the coated portion of the drum had
been markedly reduced.
Example 14
[0080] The coating material prepared in the example 2 was applied
to a stainless steel plate using spray coating, and was then dried
at room temperature for 24 hours without any heating. An aqueous
solution of sodium silicate was then sprayed onto the film surface,
and subsequently dried at room temperature for 24 hours, thus
forming a hydrophilic film. Furthermore, the coating material
prepared in the example 2 was also applied to another stainless
steel plate using spray coating, was then dried at room temperature
for 24 hours without any heating, and water was then sprayed onto
the film surface, and subsequently dried at room temperature for 24
hours, thus forming another hydrophilic film. Even when both films
were rubbed lightly with a sponge, no film separation was observed,
and particularly in the case of the film that was produced using
the aqueous solution of sodium silicate, no separation was observed
even when the film was rubbed strongly with the sponge.
Industrial Applicability
[0081] The present invention enables the production of a
hydrophilic coating film with excellent detergent resistance. This
film can be used for treating metallic materials, inorganic
materials and organic materials, and not only does the film improve
the ease with which soiling can be removed, but it also dries
quickly. This enables both water and energy to be conserved, making
it an ideal environmentally friendly product. In addition, this
coating also displays excellent durability with respect to acidic,
neutral, and alkaline detergents, which can be used in the case of
excessive soiling. Accordingly, films of the present invention can
be potentially applied to a wide range of different applications.
Films of the present invention can also be cleaned effectively even
with reduced quantities of these detergents, meaning the invention
is also environmentally friendly in terms of reduced detergent
use.
* * * * *