JP2008111011A - Coating liquid for forming hydrophilic membrane and method for forming hydrophilic membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid for forming a hydrophilic membrane, excellent in corrosion resistance and storing stability, and a method for forming the hydrophilic membrane having high hardness, easy cleaning property, soil-preventing property, hot water resistance, alkali resistance and acid resistance, and also excellent in long term durability. <P>SOLUTION: This coating liquid for forming the hydrophilic membrane contains a chelate compound of a zirconium alkoxide and/or the chelate compound of the partial hydrolyzate of the zirconium alkoxide, a silicon alkoxide and/or the partial hydrolyzate of the silicon alkoxide, and a solvent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coating solution for forming a hydrophilic film and a method for forming a hydrophilic film, and in particular, to form a film that protects the surface of a substrate made of a metal, an inorganic material, an organic material, etc., and makes the surface difficult to get dirty. The present invention relates to a coating solution for forming a hydrophilic film capable of forming a hydrophilic film and a method for forming a hydrophilic film for obtaining this film.

Conventionally, a technique for forming a hydrophilic film on the surface of a base material has been widely used for the purpose of protecting the surface of the base material or making it difficult for dirt or the like to adhere to the surface.
As a method for forming this hydrophilic film, various methods described below have already been proposed.
(1) A method of applying a surfactant.
(2) A method of applying a water absorbent resin.
(3) A method of applying a hydrophilic photocatalyst.
(4) A method of forming a film made of an inorganic compound such as silicon oxide by repelling or ceramic spraying.
(5) A method of applying a resin coating agent containing a hydrophilic component.

However, the hydrophilic films formed by these methods have problems with respect to durability against alkaline solutions, hot water, detergents and the like as described below.
That is, in the above method (1), a hydrophilic film made of a surfactant is formed, but this surfactant is water-soluble. Therefore, the obtained hydrophilic film is easily dissolved in water or detergent, and there is a problem that the hydrophilic effect disappears in a short time.
In the method (2), a hydrophilic film made of a water-absorbing resin is formed. This water-absorbing resin is easily deteriorated by an acidic or alkaline detergent. Therefore, there was a problem that the obtained hydrophilic film was also inferior in durability against detergents.
In the method (3), a hydrophilic film made of a photocatalyst is formed. However, since the photocatalyst exhibits a catalytic action under light energy, the photocatalytic effect cannot be sufficiently obtained in a dark place. was there.
In particular, when using a hydrophilic photocatalyst, it is necessary to use a silica-based binder to fix the hydrophilic photocatalyst, but this silica-based binder is easily deteriorated by an alkaline or neutral detergent. The hydrophilic coating containing a silica-based binder has a problem that it has poor durability against detergents.

Further, the method (4) has a problem that a material applicable to squeezing and ceramic spraying is limited to a heat-resistant material, and a problem that the formed hydrophilic film is vulnerable to impact.
In particular, when the hydrophilic film is a silica film, the silica film is easily deteriorated by hot water or an alkaline detergent, and therefore, the hydrophilic film has a problem that the durability against the detergent is poor.
In the method (5), a hydrophilic film is formed by a resin coating agent containing a hydrophilic component, but this resin coating agent is easily deteriorated by an acidic or alkaline detergent. Therefore, this hydrophilic film has a problem of poor durability against detergents.

Therefore, in order to solve such problems, the present inventors have proposed the following method for forming a hydrophilic film (Patent Document 1).
This hydrophilic film is formed by forming a planar substrate on a double oxide composed of silicon and zirconium and an alkaline earth metal and water, or a mixture of silicon oxide and zirconium oxide, alkaline earth metal and water. , And a second step of bringing a silicate aqueous solution into contact with the coating.
In the first step of this method, a paint containing a silicon compound, a zirconium compound, an alkaline earth metal, and water is used as a paint for forming a film. In this coating material, it is necessary to suppress the reaction of the silicon compound and the zirconium compound in order to ensure storage stability. Therefore, strong acids such as hydrochloric acid and nitric acid are added.
According to this method for forming a hydrophilic film, a hydrophilic film having excellent hydrophilicity, excellent durability against various acidic, neutral and alkaline detergents and chemicals and having high hardness is obtained. Can be formed.
JP 2005-281443 A

However, the following problems still remain in the hydrophilic film forming method proposed by the present inventors.
That is, since the paint used in this method contains a strong acid such as hydrochloric acid or nitric acid, the paint itself is corrosive, so it is used for metal substrates that are easily corroded such as copper and iron. There was a problem that it was not possible.
In addition, in the manufacturing process using this paint, there are problems such that the manufacturing equipment and exhaust equipment related to the coating and drying processes of the paint are corroded by strong acid contained in the paint.

In addition, since this paint suppresses the reaction between the silicon compound and the zirconium compound by adding a strong acid, the effect of suppressing the reaction is not always sufficient although it is stabilized. For example, when this paint is stored (or stored) at room temperature, there is a risk of gelation in the paint, which is insufficient from the viewpoint of stability (storage stability) during storage of this paint. is there.
In order to fully exhibit the reaction-suppressing effect of the paint, it is necessary to store in a refrigerator or a refrigerator. In this case, it is necessary to separately provide a refrigerator or a refrigerator in the storage, which increases the cost of storage. A new problem arises.

  The present invention has been made in order to solve the above-mentioned problems, and it is not necessary to limit the target base material, and can prevent corrosion of the base material and manufacturing equipment, and further storage stability. Excellent coating solution for forming a hydrophilic film, and has high hardness, easy washing and antifouling properties, durability to hot water, durability to alkaline solutions such as alkaline detergents, and acid detergents An object of the present invention is to provide a method for forming a hydrophilic film that has high durability to acidic solutions and excellent long-term durability.

  As a result of intensive studies to solve the above problems, the present inventors have found that the hydrolysis reaction of zirconium alkoxide has a great influence on the storage stability of the coating solution for forming a hydrophilic film. Therefore, a coating solution for forming a hydrophilic film is composed of a chelate compound of zirconium alkoxide and / or a chelate compound of zirconium alkoxide partial hydrolyzate, silicon alkoxide and / or silicon alkoxide partial hydrolyzate, and a solvent. For example, it has been found that it has excellent storage stability and there is no risk of corrosion of the base material and manufacturing equipment, and if this hydrophilic film-forming coating solution is used, it has high hardness, easy washing and antifouling properties. However, it has high durability against hot water, durability against alkaline solutions such as alkaline detergents, and durability against acidic solutions such as acid detergents. It found that it is possible to make excellent hydrophilic membrane durability easily and inexpensively formed, and completed the present invention.

  That is, the hydrophilic film-forming coating solution of the present invention is a coating solution for forming a hydrophilic film, which is a zirconium alkoxide chelate compound and / or a zirconium alkoxide partial hydrolyzate chelate compound, and silicon It contains an alkoxide and / or silicon alkoxide partial hydrolyzate and a solvent.

The zirconium alkoxide chelate compound is a reaction product of zirconium alkoxide and one or more compounds selected from the group consisting of ethanolamine, β-diketone, β-keto acid ester and carboxylic acid. preferable.
The chelate compound of the zirconium alkoxide partial hydrolyzate includes a zirconium alkoxide partial hydrolyzate and one or more compounds selected from the group consisting of ethanolamine, β-diketone, β-keto acid ester, and carboxylic acid. The reaction product is preferably.

  The hydrophilic film forming method of the present invention comprises a first step of forming a film by applying the hydrophilic film-forming coating solution of the present invention to the surface of a substrate and heat-treating it, and a silica film on the film. And a second step of applying and heat-treating an aqueous solution containing an acid salt.

According to the coating solution for forming a hydrophilic film of the present invention, it contains a chelate compound of zirconium alkoxide and / or a chelate compound of zirconium alkoxide partial hydrolyzate, silicon alkoxide and / or silicon alkoxide partial hydrolyzate, and a solvent. Therefore, the hydrolysis reaction of zirconium alkoxide can be suppressed, and the storage stability can be improved. Therefore, room temperature storage becomes possible.
Moreover, since it does not contain an acid, it is not necessary to limit the target base material, and corrosion of the base material and manufacturing equipment can be prevented.

  According to the method for forming a hydrophilic film of the present invention, the hydrophilic film-forming coating solution of the present invention is applied to the surface of a substrate and heat-treated, thereby forming a film on the surface of the substrate. A second step of applying an aqueous solution containing a silicate to the substrate and heat-treating it, so that it has high hardness, easy washing and antifouling properties, durability to hot water, and alkaline solutions such as alkaline detergents It is possible to easily and inexpensively form a hydrophilic film having high durability and durability to acidic solutions such as acid detergents and excellent long-term durability.

The best mode for carrying out the coating solution for forming a hydrophilic film and the method for forming a hydrophilic film of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Coating liquid for hydrophilic film formation"
The coating liquid for forming a hydrophilic film according to the present invention is a coating liquid for forming a hydrophilic film, and is a chelate compound of zirconium alkoxide and / or a zirconium alkoxide partial hydrolyzate that is a zirconium (Zr) component. A coating liquid comprising a compound, a silicon alkoxide that is a silicon (Si) component and / or a silicon alkoxide partial hydrolyzate, and a solvent.
The hydrophilic film includes a single layer hydrophilic film formed on the surface of the base material and a hydrophilic underlayer formed between the surface of the base material and the uppermost film.

Here, as the zirconium (Zr) component, a zirconium alkoxide chelate compound and / or a zirconium alkoxide partial hydrolyzate chelate compound is used because the zirconium alkoxide and / or its partial hydrolyzate is very easily hydrolyzed. This is because just by touching moisture in the air, it immediately causes hydrolysis and gels.
Therefore, in the coating solution for forming a hydrophilic film of the present invention, a chelate compound of zirconium alkoxide and / or a chelate compound of partial hydrolyzate of zirconium alkoxide is used. Thereby, the hydrolysis reaction of zirconium alkoxide and / or its partial hydrolyzate is suppressed, and the initial state of the coating liquid is maintained for a long period of time. Therefore, the storage stability of the coating liquid is improved, and room temperature storage (storage) is also possible.

As the above-mentioned chelate compound of zirconium alkoxide, zirconium alkoxide and a hydrolysis inhibitor comprising one or more compounds selected from the group consisting of ethanolamine, β-diketone, β-keto acid ester and carboxylic acid; The reaction product is preferably.
Moreover, as a chelate compound of said zirconium alkoxide partial hydrolyzate, 1 type or 2 types selected from the group of a zirconium alkoxide partial hydrolyzate, ethanolamine, (beta) -diketone, (beta) -keto acid ester, and carboxylic acid It is preferable that it is a reaction product with the hydrolysis inhibitor which consists of the above compound.

Here, examples of the zirconium alkoxide include zirconium tetrapropoxide and zirconium tetrabutoxide.
Moreover, as a zirconium alkoxide partial hydrolyzate, a zirconium tetrapropoxide partial hydrolyzate, a zirconium tetrabutoxide partial hydrolyzate, etc. can be illustrated, for example.

  The hydrolysis inhibitor is a compound that forms a chelate compound with zirconium alkoxide and / or a zirconium alkoxide partial hydrolyzate, and has an action of suppressing hydrolysis of the chelate compound. For example, monoethanol Amine, diethanolamine, ethanolamine such as triethanolamine, β-diketone such as acetylacetone, methyl acetoacetate, ethyl acetoacetate, diethyl malonate, ethyl phenoxyacetate, etc., acetic acid, lactic acid, citric acid, benzoic acid Examples thereof include carboxylic acids such as acid and malic acid.

The addition amount of the hydrolysis inhibitor is preferably 0.5 mol times or more and 4 mol times or less of zirconium (Zr) contained in zirconium alkoxide and / or a partial hydrolyzate thereof.
If the addition amount of the hydrolysis inhibitor is less than 0.5 mol times, the stability of the coating solution for forming a hydrophilic film will be insufficient. On the other hand, if the addition amount exceeds 4 mol times, This is because the hydrolysis inhibitor remains in the film even after the hydrophilic coating obtained by applying the hydrophilic film-forming coating solution is heat-treated, and as a result, the hardness of the film decreases. .

  In addition, as the chelate compound of zirconium alkoxide and / or the zirconium alkoxide partial hydrolyzate, the zirconium alkoxide and / or zirconium alkoxide partial hydrolyzate is dissolved in the above solvent, and the above hydrolysis inhibitor is further added. In addition, chelation may be caused in the obtained solution.

  However, it is necessary that the above solution does not contain silicon alkoxide and / or silicon alkoxide partial hydrolyzate. The reason is that when adding a hydrolysis inhibitor, if a silicon alkoxide and / or a silicon alkoxide partial hydrolyzate is present in the solution, the hydrolysis inhibitor is converted into a zirconium alkoxide and / or a zirconium alkoxide partial hydrolysis. This is because a chelation reaction easily occurs with a silicon alkoxide and / or a silicon alkoxide partial hydrolyzate without causing a chelation reaction with the product, and the target chelate compound cannot be obtained.

  In order for the chelate compound of zirconium alkoxide and / or the chelate compound of the partial hydrolyzate of zirconium alkoxide to coexist with the silicon alkoxide and / or the partial hydrolyzate of silicon alkoxide, the chelate compound of zirconium alkoxide and / or the zirconium alkoxide moiety A hydrolyzate and a hydrolysis inhibitor are reacted to form a chelate compound, and this chelate compound may be added to a solution containing silicon alkoxide and / or a partial hydrolyzate thereof.

As the zirconium (Zr) component, a zirconium compound other than the above-mentioned chelate compound is used as a whole zirconium (Zr) component, that is, a chelate compound of zirconium alkoxide and / or a chelate compound of a partial hydrolyzate of zirconium alkoxide and the above chelate compound. Zirconium (Zr) in the total amount with other zirconium compounds may be 80 mol% or less, preferably 50 mol% or less in terms of the content when converted to zirconium oxide (ZrO ₂ ).
When the content of the zirconium compound exceeds 80 mol%, it is not preferable because the film cannot be imparted with properties such as hydrophilicity, durability, and adhesion prevention such as dirt.
Examples of such zirconium compounds include zirconia sol, zirconium oxychloride, zirconyl nitrate, and zirconyl acetate.

The total zirconium (Zr) component content in the hydrophilic film-forming coating solution is preferably 0.1% by mass or more and 9% by mass or less in terms of zirconium oxide (ZrO ₂ ). The reason is that when the content of all zirconium (Zr) components is out of the range of 0.1% by mass or more and 9% by mass or less, it becomes difficult to impart sufficient water resistance to the film.

Examples of the silicon alkoxide include tetraethoxysilane and tetramethoxysilane.
Moreover, as a silicon alkoxide partial hydrolyzate, a tetraethoxysilane partial hydrolyzate, a tetramethoxysilane partial hydrolyzate, etc. can be illustrated, for example.

In addition, as a silicon (Si) component, a silicon compound other than the above silicon alkoxide and / or silicon alkoxide partial hydrolyzate is converted into an all silicon (Si) component, that is, silicon alkoxide and / or silicon alkoxide partial hydrolyzate, 80 mol% of silicon (Si) at a content when converted to silicon oxide (SiO ₂₎ in the total amount of the other silicon compounds, preferably may contain less than 50 mole%.
If the content of the silicon compound exceeds 50 mol%, it is not preferable because the film cannot be imparted with properties such as hydrophilicity, durability, and adhesion prevention such as dirt.
Examples of such a silicon compound include alkali silicate and colloidal silica (silica sol).

The content of the total silicon (Si) component in the hydrophilic film forming coating solution is preferably 0.1% by mass or more and 9% by mass or less in terms of silicon oxide (SiO ₂ ). The reason is that when the content of the total silicon (Si) component is out of the range of 0.1% by mass or more and 9% by mass or less, it becomes difficult to impart sufficient water resistance to the film.

The mass ratio of the total zirconium (Zr) component and the total silicon (Si) component in the hydrophilic film forming coating solution is expressed as a mass ratio (ZrO ₂ : SiO ₂ ) when all of these are converted into oxides. In this case, it is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 2: 8 to 5: 5.
This is because, when the mass ratio (ZrO ₂ : SiO ₂ ) is out of the above range, it becomes impossible to impart properties such as hydrophilicity, durability, and adhesion prevention such as dirt to the film.

  The solvent is not particularly limited as long as it is a solvent capable of dissolving the chelate compound of zirconium alkoxide and / or the chelate compound of zirconium alkoxide partial hydrolyzate, and the silicon alkoxide and / or silicon alkoxide partial hydrolyzate. , Methanol (boiling point: 65 ° C.), ethanol (boiling point: 78 ° C.), alcohols such as 1-propanol (boiling point: 97 ° C.), 2-propanol (boiling point: 82 ° C.), acetone (boiling point: 56 ° C.), methyl ethyl ketone Examples include solvents (low boiling point solvents) having a boiling point of about 100 ° C. or lower, such as ketones such as (boiling point: 80 ° C.) and diethyl ketone (boiling point: 102 ° C.).

  In order to improve the coating property of the coating solution for forming a hydrophilic film, 1-ethoxy-2-propanol (boiling point: 132 ° C.), 1-methoxy-2-propanol (boiling point: 120 ° C.), 2-methoxyethyl Acetate (boiling point: 145 ° C), 2-ethoxyethyl acetate (boiling point: 156 ° C), N, N-dimethylformamide (boiling point: 153 ° C), N-methylformamide (boiling point: 180 ° C), 2-ethoxyethanol A high boiling point solvent such as (boiling point: 136 ° C.) can be used together with the above low boiling point solvent.

  In addition, when water is contained in said solvent, it is preferable to restrain water content in the coating liquid for hydrophilic film formation to 5 mass% or less. This is because if the content of water in the coating solution exceeds 5% by mass, the stability of the coating solution is lowered, and long-term storage at room temperature exceeding 1 month becomes difficult.

In addition to the zirconium (Zr) component and the silicon (Si) component, this hydrophilic film forming coating solution may contain other metal ions.
By adding other metal ions, the long-term durability of the hydrophilic film can be improved. Examples of such metal ions include divalent metal ions such as alkaline earth metals, trivalent metal ions such as aluminum and boron, and tetravalent metal ions such as titanium.
Such metal ions are preferably added to the hydrophilic film-forming coating solution in the form of a solution of nitrate, chloride, organic acid salt or the like. However, if too much is added in the form of nitrates, chlorides, etc., it may cause corrosion of the base material and the production equipment, so care must be taken in the amount added.

  The content of the metal ions in the hydrophilic film-forming coating solution is preferably 10 ppm or more and 2% by mass or less. If the content of the metal ions is less than 10 ppm, it is difficult to improve the long-term durability of the film. On the other hand, if the content of the metal ions exceeds 2% by mass, it is sufficient for the substrate. This is because a film having adhesion cannot be formed.

Further, the hydrophilic film-forming coating liquid, an acrylic resin, urethane resin, melamine resin, epoxy resin, silicone resin, and fluorine resin resin or _{R x Si (OR) 4-} x (x is 1 to 3, An appropriate amount of an organosilane compound represented by (integer), that is, a coupling agent may be added.
Thus, when resin and a silane coupling agent are added to the coating liquid for hydrophilic film formation, the adhesiveness of the film | membrane formed and a base material, especially a plastics base material will improve.

  Moreover, it is preferable to add an appropriate amount of various surfactants such as an anionic surfactant, a nonionic surfactant, and a cationic surfactant to the coating solution for forming a hydrophilic film. Thus, when a surfactant is added to the coating solution for forming a hydrophilic film, the coating property of the coating solution for forming a hydrophilic film on a substrate can be improved.

  The solid content in the hydrophilic film-forming coating solution, that is, the content of the hydrophilic film-forming component not containing an organic component such as a resin or a silane coupling agent is not particularly limited, but is 0.1 in terms of oxide. The content is preferably not less than 10% by mass and not more than 10% by mass. When the solid content is less than 0.1% by mass, it becomes difficult to form a hydrophilic film. On the other hand, when the solid content exceeds 10% by mass, the hydrophilic film forming coating solution is stored. This is because the stability is lowered.

"Method of forming hydrophilic film"
The hydrophilic film forming method of the present invention comprises a first step of forming a film by applying the hydrophilic film-forming coating solution of the present invention to the surface of a substrate and heat-treating it, and a silica film on the film. And a second step of applying and heat-treating an aqueous solution containing an acid salt.

The base material is not particularly limited, and is made of a ceramic material such as glass or translucent alumina, a base material made of an inorganic material such as straw, concrete or stone, iron, stainless steel, aluminum, gold, silver, titanium, metal. Examples thereof include a base material made of a metal material such as a plated product, and a base material made of an organic material such as plastic and fiber.
Since the coating liquid for forming a hydrophilic film of the present invention does not contain an acid as a hydrolysis inhibitor, there is no possibility of corroding the base material, and therefore it can be applied to a metal base material.

As a coating method of the hydrophilic film forming coating solution, for example, a spin coating method, a dip coating method, a roll coating method, a bar coating method, a spray coating method, an ink jet method, a screen printing method, a brush coating method, or the like is used. Can do.
The coating film thus formed is heat-treated to form a film.

The temperature and time in this heat treatment should be as high as possible and long as long as they do not adversely affect the substrate, which increases the strength and water resistance of the film and prevents the hydrolysis inhibitor from remaining. In some cases, a short heat treatment at a temperature of the degree of drying may be sufficient.
Specifically, when the base material is an inorganic material such as a glass substrate, the specific heat treatment temperature is preferably room temperature (25 ° C.) to 500 ° C., more preferably 80 ° C. to 500 ° C. Moreover, when a base material is a plastic substrate or a plastic film, room temperature (25 degreeC)-150 degreeC is preferable, More preferably, it is 80 degreeC-130 degreeC. Moreover, when a base material is metal materials, such as a metal substrate, room temperature (25 degreeC) -300 degreeC are preferable, More preferably, they are 80 degreeC-300 degreeC.
In addition, the atmosphere at the time of heat processing is not specifically limited, Usually, it carries out in air | atmosphere.

  The thickness of the film thus obtained is preferably 0.01 μm or more and 5 μm or less. When the thickness of the film is less than 0.01 μm, a sufficient hydrophilic effect cannot be obtained, and the hardness and wear resistance are inferior. On the other hand, when the thickness of the film is thicker than 5 μm, the adhesion with the substrate is lowered and cracks are easily generated, which is not preferable.

Next, an aqueous solution containing silicate is applied onto the film.
Although it does not restrict | limit especially as aqueous solution containing this silicate, For example, aqueous solutions, such as lithium silicate, sodium silicate, potassium silicate, or a mixture of these aqueous solutions can be illustrated.
The concentration of silicate in this aqueous solution is preferably 0.01% by mass or more and 50% by mass or less. If the silicate concentration is less than 0.01% by mass, the hydrophilicity and hardness of the film cannot be improved. On the other hand, if the silicate concentration exceeds 50% by mass, the film thickness becomes too thick. This is because cracks and peeling easily occur.

It is preferable that colloidal silica is added to the aqueous solution containing the silicate. The reason is that, by adding colloidal silica, the smoothness of the hydrophilic film is improved and the antifouling effect is enhanced. The amount of colloidal silica added is preferably 0.25 mol times or more and 4 mol times or less of the silicate.
This is because when the amount of colloidal silica added is less than 0.25 mol times, no improvement in smoothness is observed, whereas when the amount added exceeds 4 mol times, the hardness of the hydrophilic film is lowered.

  The aqueous solution containing the silicate preferably contains an appropriate amount of various surfactants such as an anionic surfactant, a nonionic surfactant, and a cationic surfactant. When these surfactants are added to an aqueous solution containing a silicate, the coating properties of this aqueous solution can be improved.

As a method of applying the aqueous solution containing the silicate, for example, a spin coating method, a dip coating method, a roll coating method, a bar coating method, a spray coating method, an ink jet method, a screen printing method, a brush coating method, or the like is used. Can do.
An aqueous solution containing this silicate easily penetrates into the above-mentioned film, and a sufficient effect can be obtained with the silicate that has penetrated into the film. It may be washed away.
The film thus obtained is heat-treated to form a hydrophilic film.

The temperature and time in this heat treatment should be as high as possible and long as long as they do not adversely affect the substrate, which increases the strength and water resistance of the film and prevents the hydrolysis inhibitor from remaining. In some cases, a short heat treatment at a temperature of the degree of drying may be sufficient.
Specifically, when the base material is an inorganic material such as a glass substrate, the specific heat treatment temperature is preferably room temperature (25 ° C.) to 500 ° C., more preferably 80 ° C. to 500 ° C. Moreover, when a base material is a plastic substrate or a plastic film, room temperature (25 degreeC)-150 degreeC is preferable, More preferably, it is 80 degreeC-130 degreeC. Moreover, when a base material is metal materials, such as a metal substrate, room temperature (25 degreeC) -300 degreeC are preferable, More preferably, they are 80 degreeC-300 degreeC.
In addition, the atmosphere at the time of heat processing is not specifically limited, Usually, it carries out in air | atmosphere.

The hydrophilic film thus obtained is considered to have the following film structure.
(1) When the amount of the aqueous solution containing the silicate is small or the concentration is low, the aqueous solution penetrates into the film, and at least the surface layer portion of the film is modified to a hydrophilic layer. .
When an aqueous solution containing silicate is applied to the membrane, the aqueous solution penetrates into the membrane, and the alkoxy groups remaining in the membrane are further hydrolyzed by alkali components such as Na, K, Li, etc. and water in the aqueous solution. Dehydration and dealcoholization reactions occur between the decomposed metal alkoxides, and a composite oxide composed of silica and zirconia is generated. Therefore, at least the surface layer portion of the film is modified to a hydrophilic layer.

  Furthermore, the silica component in the film and the silicate ions supplied from the aqueous solution react with zirconium ions in the film, other metals, water and alkali supplied from the aqueous solution, etc. to form a hydrate, Block the holes on the surface. As a result, the obtained hydrophilic film has higher hardness and improves durability against hot water and alkaline solution.

(2) When the application amount of the aqueous solution containing silicate is large or the concentration is high, the outermost layer rich in hydrophilicity mainly composed of silicate is formed on the film as the underlayer. Thus, the film has a two-layer structure.
The film serving as the underlayer has a high hardness and has improved durability against hot water and an alkaline solution. Furthermore, when a hydrophilic outermost layer mainly composed of silicate is formed on a film having such characteristics, the hydrophilicity of the entire film, that is, the hydrophilic film is improved, and the film thickness is also increased. Thicker, higher hardness is obtained, and durability against wear is also improved.

As described above, according to the coating liquid for forming a hydrophilic film of the present embodiment, the hydrolysis reaction of zirconium alkoxide can be suppressed, and the storage stability can be improved. Therefore, room temperature storage (storage) can be performed for a long time.
Moreover, since it does not contain an acid, it is not necessary to exclude a metal base material, and corrosion of the base material and manufacturing equipment can be prevented.

  Further, according to the method for forming a hydrophilic film of the present embodiment, it has high hardness, easy washing and antifouling properties, durability to hot water, durability to an alkaline solution such as an alkaline detergent, and acid It is possible to easily and inexpensively form a hydrophilic film composed of a single layer or multiple layers having high durability against acidic solutions such as detergents and excellent long-term durability.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
Chelating zirconium butoxide and methyl acetoacetate by dissolving 4 parts by weight of zirconium butoxide in 86 parts by weight of 2-propanol, adding 3 parts by weight of methyl acetoacetate and stirring at room temperature for 30 minutes. Went.
Next, 6 parts by mass of tetraethoxysilane and 1 part by mass of calcium nitrate ethanol solution (concentration: 1% by mass) were mixed with the chelated solution to obtain a coating solution for forming a hydrophilic film.

Next, this hydrophilic film-forming coating solution was applied onto a stainless steel substrate by a spray coating method, and heat-treated at 200 ° C. for 20 minutes in the air to form a base layer. At this time, the coating amount was adjusted so that the film thickness of the underlayer was 0.2 μm.
Next, a 20 mass% sodium silicate aqueous solution was applied onto the underlayer by a bar coating method, and heat-treated at 200 ° C. for 20 minutes in the air to form the hydrophilic film of Example 1.

"Example 2"
Chelating zirconium butoxide and triethanolamine by dissolving 3 parts by weight of zirconium butoxide in 86 parts by weight of 2-propanol, adding 2 parts by weight of triethanolamine, and stirring at room temperature for 30 minutes. Went.
Next, 6 parts by mass of tetraethoxysilane, 1 part by mass of a silane coupling agent (3-glycidoxypropyltrimethoxysilane), and 2 parts by weight of a calcium nitrate ethanol solution (calcium nitrate) were added to the chelated solution. A tetrahydrate 10 mass% ethanol solution) was mixed to obtain a coating solution for forming a hydrophilic film.

Next, this hydrophilic film-forming coating solution was applied onto an acrylic substrate by a spray coating method and heat-treated at 80 ° C. for 60 minutes in the air to form an underlayer. At this time, the coating amount was adjusted so that the film thickness of the underlayer was 0.5 μm.
Next, the acrylic substrate on which the underlayer was formed was immersed in an aqueous silicate solution obtained by mixing 95 parts by mass of a 20% by mass sodium silicate aqueous solution and 5 parts by weight of colloidal silica, and then the acrylic substrate. Was washed with water to remove excess sodium silicate, and then heat-treated in the atmosphere at 80 ° C. for 60 minutes to form the hydrophilic film of Example 2.

"Example 3"
In 82 parts by mass of 2-propanol, 6 parts by mass of a chelate compound of zirconium alkoxide and acetylacetone (molar ratio of zirconium alkoxide to acetylacetone is 1: 1) was dissolved, and a chelate compound of zirconium alkoxide and acetylacetone was dissolved 2 A propanol solution was obtained.
Next, 10 parts by mass of tetraethoxysilane and 2 parts by weight of calcium acetate aqueous solution (10% by mass aqueous solution of calcium acetate tetrahydrate) are mixed with this 2-propanol solution, and a hydrophilic film forming coating solution is prepared. Obtained.

Next, this hydrophilic film-forming coating solution was applied onto a copper plate by a spray coating method, and heat-treated at 120 ° C. for 40 minutes in the air to form an underlayer. At this time, the coating amount was adjusted so that the film thickness of the underlayer was 1 μm.
Next, a 20% by mass sodium silicate aqueous solution containing sodium alkylbenzenesulfonate was applied on the underlayer by a spray coating method and heat-treated at 120 ° C. for 40 minutes in the atmosphere. The hydrophilic film of Example 3 Formed.

"Comparative Example 1"
6 parts by mass of tetraethoxysilane, 4 parts by mass of zirconium butoxide, 69 parts by mass of 2-propanol, 20 parts by mass of pure water, and 1 part by mass of nitric acid were mixed to obtain a coating solution for forming a hydrophilic film.
Next, this hydrophilic film-forming coating solution was applied onto a stainless steel substrate by a spray coating method, and heat-treated at 200 ° C. for 30 minutes in the atmosphere to form a base layer. At this time, the coating amount was adjusted so that the film thickness of the underlayer was 0.2 μm.
Next, a 20% by mass aqueous sodium silicate solution was applied onto the underlayer by a bar coating method, followed by heat treatment at 200 ° C. for 30 minutes in the air to form the hydrophilic film of Comparative Example 1.

"Comparative Example 2"
6 parts by weight of tetraethoxysilane, 4 parts by weight of zirconium butoxide, 2 parts by weight of calcium nitrate ethanol solution (10% by weight ethanol solution of calcium nitrate tetrahydrate) and 88 parts by weight of 2-propanol were mixed to make hydrophilic. A coating solution for forming a conductive film was obtained.
Next, this hydrophilic film-forming coating solution was applied onto a stainless steel substrate by a spray coating method, and heat-treated at 200 ° C. for 30 minutes in the atmosphere to form a base layer. At this time, the coating amount was adjusted so that the film thickness of the underlayer was 0.2 μm.
Next, a 20% by mass aqueous sodium silicate solution was applied onto the underlayer by a bar coating method, followed by heat treatment at 200 ° C. for 30 minutes in the air to form a hydrophilic film of Comparative Example 2.

“Comparative Example 3”
A coating solution for forming a hydrophilic film was obtained according to Example 1.
Next, this hydrophilic film-forming coating solution was applied onto a stainless steel substrate by a spray coating method, and heat-treated at 200 ° C. for 20 minutes in the air to form a coating film of Comparative Example 3. At this time, the coating amount was adjusted so that the film thickness was 0.2 μm.

"Evaluation of coating solution for hydrophilic film formation"
The coating liquids for forming a hydrophilic film in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated.
The evaluation items were 50 ° C. storage and corrosive two items. The evaluation methods for these evaluation items are as follows.
(1) Storage at 50 ° C. Using a thermostatic bath, the coating solution for forming a hydrophilic film was stored at 50 ° C. for 1 month while observing the progress.
(2) Corrosivity After immersing the copper plate in the coating solution for forming a hydrophilic film, the copper plate was dried at 100 ° C., and the presence or absence of discoloration of the copper plate was visually evaluated.

"Evaluation of membrane"
The hydrophilic films of Examples 1 to 3 and Comparative Examples 1 and 2 and the coating film of Comparative Example 3 were evaluated.
The evaluation items were five items: film appearance, pencil hardness, easy cleaning, alkali resistance, and hot water resistance. The evaluation methods for these evaluation items are as follows.
(1) Film appearance The surface state of the film was visually observed.
(2) Pencil hardness It evaluated based on Japanese Industrial Standard JISK5600 "paint general test method".

(3) Easily washed The film was written on the film with an oil pen to make it dirty, and the dirt was rubbed with a sponge soaked in water, and it was observed whether or not the dirt was removed.
(4) Alkali resistance The membrane was immersed in a 5% by weight aqueous sodium hydroxide solution at room temperature (25 ° C.) for 30 days while observing the course, then washed with water, and the state of the membrane was observed visually. did.
(5) Hot water resistance The membrane was immersed in hot water at 98 ° C. for 30 days while observing the progress, and then the state of the membrane was visually observed.
These evaluation results are shown in Table 1.

  The coating solution for forming a hydrophilic film of the present invention contains a chelate compound of zirconium alkoxide and / or a chelate compound of zirconium alkoxide partial hydrolyzate, silicon alkoxide and / or silicon alkoxide partial hydrolyzate, and a solvent. Can form a film with high hardness, easy cleaning, antifouling properties, hot water resistance, alkali resistance, acid resistance, and excellent long-term durability. It can be used in all technical fields that require both of its properties, and its industrial significance is extremely great.

Claims (4)

A coating solution for forming a hydrophilic film,
Zirconium alkoxide chelate compound and / or zirconium alkoxide partial hydrolyzate chelate compound, silicon alkoxide and / or silicon alkoxide partial hydrolyzate, and solvent-containing coating, liquid.   The zirconium alkoxide chelate compound is a reaction product of zirconium alkoxide and one or more compounds selected from the group consisting of ethanolamine, β-diketone, β-keto acid ester and carboxylic acid. The coating solution for forming a hydrophilic film according to claim 1.   The chelate compound of the zirconium alkoxide partial hydrolyzate includes a zirconium alkoxide partial hydrolyzate and one or more compounds selected from the group consisting of ethanolamine, β-diketone, β-keto acid ester, and carboxylic acid. The coating solution for forming a hydrophilic property according to claim 1 or 2, wherein A first step of forming a film by applying the hydrophilic film-forming coating solution according to any one of claims 1 to 3 to a surface of a substrate and performing a heat treatment;
A second step in which an aqueous solution containing a silicate is applied on the film and heat-treated;
A method for forming a hydrophilic film, comprising: