JPH11172148A - Hydrophilic coating material and production of hydrophilic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject coating material capable of keeping transparency and hydrophilicity, and facilitating the removal of attached soil when the coating material is coated on the surface of a substrate such as a glass by using an aqueous solution obtained by dissolving a silicic acid salt, phosphoric acid or the like. SOLUTION: This hydrophilic coating material comprises an aqueous solution of (A) a silicic acid salt, preferably a salt comprising silicon dioxide and a metal oxide represented by the formula (M is Al, Fe, Ca, Mg, Na, K, Li or ammonium), (B) phosphoric acid or a derivative thereof, preferably the phosphoric acid such as phosphoric anhydride, orthophosphoric acid, pyrophosphoric acid and tripolyphosphoric acid anhydride, phosphoric acid salt or phosphoric acid ester. The (weight) ratio of the components A to B compounded therewith is preferably (99/1)-(1/99).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrophilic coating material and a hydrophilic substrate, and more particularly, to the surface of a substrate such as glass, resin (plastic, fiber-reinforced resin), metal, or a composite thereof. TECHNICAL FIELD The present invention relates to a hydrophilic paint which is transparent and can maintain hydrophilicity when coated, and a method for producing a hydrophilic base material coated with the hydrophilic paint.

[0002]

2. Description of the Related Art As a method for imparting hydrophilicity to the surface of a substrate such as glass, resin, metal or a composite material thereof for the purpose of preventing dew condensation and fogging, it is known to form a coating with a water-soluble polymer or the like. ing. Specific examples of the formation of this coating include polyvinyl alcohol as a water-soluble polymer,
Carboxymethylcellulose and ionic polymers are used. Also, for example, in Japanese Patent Application Laid-Open No. 7-102189,
An aqueous polymer compound having a polyoxyalkylene chain represented by polyethylene oxide (PEO) and an aqueous resin such as an aqueous alkyd resin and an aqueous polyester resin have been proposed.

In addition, other than the above-mentioned water-soluble polymer,
Hydrophilization with water glass such as sodium silicate and potassium silicate is also commonly performed. JP-A-8-283042 proposes a surface treating agent comprising phosphoric acid or a derivative thereof, boric acid or a derivative thereof, and a solvent.

[0004] On the other hand, as a method for imparting antifouling properties,
Contrary to hydrophilicity, a method of making the surface hydrophobic / water-repellent is also performed. This means that the surface is coated with a water-repellent fluorine component, and the contact angle with water is set to 100 ° or more, thereby making it difficult for contaminants to adhere.

[0005]

However, the film made of the above water-soluble polymer does not have sufficient weather resistance, water resistance, heat resistance, and long-lasting hydrophilicity, and does not have sufficient film hardness. In addition, since the mixture is a mixture of various components, the mixture generally becomes cloudy or opaque, and its use is limited.

In the case of inorganic water glass, the initial hydrophilicity is good, but white water and devitrification occur after repeated water treatment, and micro cracks occur on the surface during repeated drying. There's the problem I said.

The surface treating agent comprising phosphoric acid or a derivative thereof, boric acid or a derivative thereof, and a solvent disclosed in Japanese Patent Application Laid-Open No. 8-283042 has good initial hydrophilicity, but is repeatedly heated and immersed in running water. And the hydrophilicity decreased, and the durability was not always sufficient.

On the other hand, in the method based on the water repellent treatment of the surface,
Generally, fluorine components are expensive, have low adhesiveness and adhesion to other materials, and have problems such as requiring special treatment to make them adhere.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a transparent and hydrophilic material when coated on the surface of a substrate such as glass, resin, metal or a composite material thereof. And a method for producing a hydrophilic base material on which a coating with the hydrophilic paint can be easily removed by, for example, washing with water.

[0010]

Means for Solving the Problems The present inventors have made intensive studies in order to achieve the above-mentioned object, and applied an aqueous solution of a paint composed of a specific component to the surface of a base material, and baked. It has been found that a heat treatment such as this forms a hydrophilic film which is transparent, has high hydrophilicity persistence, and can wash off dirt attached by washing with water or the like.

That is, one aspect of the present invention is a hydrophilic paint comprising an aqueous solution in which a silicate and phosphoric acid or a derivative thereof are dissolved. After applying a hydrophilic paint made of the aqueous solution to the substrate surface, the substrate itself or the substrate surface is heated to 50 ° C to 600 ° C.
Is a method for producing a hydrophilic substrate that is subjected to a heat treatment within the range described above.
And, with the hydrophilic paint and the production method of the present invention, it is possible to form the above-mentioned transparent hydrophilic film having high hydrophilicity persistence and capable of washing off dirt attached by washing with water or the like.

Although the mechanism of the above-mentioned effects is not yet clear, it is known that silicate is water-soluble, but it is cross-linked by heating to become insoluble in water. This is considered to be due to the fact that the hydrophilic and hydrophilic phosphoric acid or its derivative was physically fixed in the network of silicic acid crosslinked by heating and could not be eluted.

Hereinafter, the present invention will be described in more detail together with the reasons for limiting the numerical values. In the present invention, the silicate is a salt composed of silicon dioxide and a metal oxide represented by the general formula xM ^I ₂ O · y SiO ₂ , wherein M is Al, Fe, C
It is a substance selected from a, Mg, Na, K, Li, and ammonium. These may be used alone or as a mixture of two or more types without any problem.

Phosphoric acid or a derivative thereof includes phosphoric anhydride,
Orthophosphoric acid, pyrophosphoric acid, phosphoric acid such as tripolyphosphoric anhydride, a phosphate, or a phosphoric acid ester, and as the phosphate, the phosphoric acid (phosphoric anhydride, metaphosphoric acid,
Pyrophosphate, orthophosphate, triphosphate, tetraphosphate) and Na
⁺ , K ⁺ , Li ⁺ , and a compound with one or more cations selected from NH ₄ ⁺ . Examples of the phosphoric ester include compounds with alkyl esters such as methyl, ethyl, propyl, and butyl groups. Among them, preferred compounds include sodium tripolyphosphate and sodium pyrophosphate. In addition, these compounds described above may be used alone or as a mixture of two or more, without any problem.

The mixing ratio (mass ratio) of the silicate and phosphoric acid or a derivative thereof is not particularly limited, but is preferably 99/1 to 1/99, more preferably 95/5.
If the content of the silicate exceeds the above value (95/5), whitening and devitrification occur during repeated water treatment such as washing, which is not preferable. Further, depending on the baking conditions, fine cracks may occur on the surface after cooling, which is not preferable. Conversely, the content of phosphoric acid or a derivative thereof is the above value (5
/ 95) is not preferable because it is not sufficiently fixed in the network of the silicic acid crosslinked by baking and flows out by washing with water or the like, and sufficient hydrophilicity cannot be exhibited. Furthermore, the concentration of silicate and phosphoric acid or a derivative thereof in the form of an aqueous solution is not particularly limited. However, in consideration of applicability to a substrate, hydrophilicity persistence after baking, and durability. % By mass or more is preferred.

In addition to the silicate and phosphoric acid or a derivative thereof, a dispersant, a thickener, and the like may be added as an additive within a range that does not impair the performance of the hydrophilic paint of the present invention. it can.

Further, since the above-mentioned components such as silicate, phosphoric acid or its derivative, and additives are water-soluble, water is most suitable as a coating solvent, but water-miscible solvents such as alcohol and butyl cellosolve are used. Solvents can be used as long as the performance of the hydrophilic paint of the present invention is not impaired.

On the other hand, the method for producing a hydrophilic substrate of the present invention comprises:
After the above-mentioned hydrophilic paint is applied to the surface of the base material, the base material itself or the base material surface is subjected to a heat treatment within a range of 50 ° C to 600 ° C, and the coating method at that time is particularly limited. Instead, the coating is performed using a conventionally used coating method such as a dipping method, a roll coater method, a spin coating method, and a spray method.

Regarding the heat treatment, the baking conditions are as follows:
There are factors such as temperature and time and the material of the base material, so it cannot be specified unambiguously.
The temperature is preferably in the range of 00 ° C. When the temperature is lower than 50 ° C., baking is insufficient, and the paint components flow out due to washing with water, so that sufficient hydrophilicity cannot be expected. On the other hand, when the temperature is higher than 600 ° C., decomposition and fluidization of the base material, particularly some metals such as resin or aluminum, occur, and an undesirable phenomenon occurs. A more preferred heat treatment is to remove water at 50 to 100 ° C. and then bake at a high temperature of 100 to 600 ° C. to quickly complete the silicate crosslinking reaction. Painting and baking can be repeated a plurality of times. It is also desirable to perform annealing after baking to remove distortion of the surface coating. Further, as a heating device used for the heat treatment, a commonly used dryer, an electric furnace, and other heating devices can be used.

The thickness of the film formed on the surface of the substrate is not particularly limited. However, from the viewpoint of the transparency of the film and the sustainability of the hydrophilicity, the thickness of the film is from submicron to tens of microns. Is preferred.

The substrate is not particularly limited, but may be glass such as quartz or silicate glass, thermoplastic resin such as polyester, polyamide, polyether or polyolefin, epoxy or unsaturated polyester. Thermosetting resins and their fiber-reinforced composite materials, metals such as aluminum, iron (stainless steel), titanium, and copper can be targeted. In particular, decorative patterns are applied to the surface, and it is necessary to prevent the surface from being stained. Glass, resin, metal, or transparent glass or resin that needs to prevent fogging or condensation, such as advertising boards, glass for greenhouses, glass for vehicles such as automobiles, lenses such as glasses, mirrors, etc. Can be mentioned.

[0022]

Embodiments of the present invention will be described below. A predetermined amount of a silicate and phosphoric acid derivative was dissolved in water to obtain a hydrophilic paint. This paint is applied to a transparent glass plate as a base material using a coating means such as a bar coater, and then,
Bake at a desired temperature (50 ° C to 600 ° C) in a heating device,
A glass plate (substrate) having a hydrophilic coating on the surface was produced. The glass plate manufactured in this manner was free from fogging and dew condensation for a long time even when it was put into and taken out of a humid place, transparency and hydrophilicity were maintained, and dirt substances could be easily washed.

[0023]

[Example] Sodium silicate (silicate N
a) was prepared by using sodium tripolyphosphate (Na tripolyphosphate) as a derivative of phosphoric acid and dissolving them in water to obtain an aqueous solution (hydrophilic paint) having a concentration shown in Table 1;
And Comparative Examples 1 to 4 were prepared. Then, these paints were applied to a transparent glass plate using a bar coater, and the glass plate was placed in a dryer and treated at a baking temperature shown in Table 1.

Examples 1 to 5 obtained by processing as described above
4 and the glass plates of Comparative Examples 1 to 4 were allowed to cool, washed with water, and left outdoors for one month. Thereafter, the surface transparency and water wettability were evaluated. The transparency was evaluated by visual inspection of the appearance, and the water wettability was evaluated by spraying water in the form of a mist and visually observing the state of water repellency (repelling). If there was, it was evaluated as △, and if there was overall repelling, it was evaluated as ×.
These evaluation results are also shown in Table 1.

[0025]

[Table 1]

As is clear from Table 1 above, Examples 1 to
About 4, transparency and water wettability (hydrophilicity) are good,
It can be seen that these characteristics are maintained for one month or more.
On the other hand, in Comparative Example 1 in which a paint consisting of an aqueous solution of only sodium silicate was applied, transparency was partially devitrified, and hydrophilicity was partially repelled. In Comparative Example 2 in which a coating consisting of an aqueous solution of only sodium tripolyphosphate was applied, the transparency was maintained, but the hydrophilicity was completely absent. For comparison, in Comparative Example 3 in which only water used in this test was applied, as in Comparative Example 2, the transparency was maintained, but the hydrophilicity was completely absent. Also, set the baking temperature to 25
Comparative Example 4 baked at a temperature as low as
Similarly, transparency was maintained, but hydrophilicity was completely absent.

[0027]

As described above, according to the hydrophilic paint of the present invention, when applied to the surface of a base material such as glass, resin, metal or a composite material thereof, it is transparent and maintains hydrophilicity for a long time. In addition, it is possible to form a film capable of easily removing adhered dirt by washing with water or the like.

According to the method for producing a hydrophilic substrate using the above-mentioned hydrophilic paint, the transparency of the substrate or the see-through of the decorative pattern can be maintained for a long time, and the dirt attached to the surface can be washed with water. Can be easily removed.

Claims (5)

[Claims] 1. A hydrophilic coating material comprising an aqueous solution in which silicate and phosphoric acid or a derivative thereof are dissolved. 2. The hydrophilic paint according to claim 1, wherein the silicate is a salt comprising silicon dioxide represented by the general formula xM ^I ₂ O.ySiO ₂ and a metal oxide. Where M is Al, Fe, Ca,
It is a substance selected from Mg, Na, K, Li, and ammonium. 3. The method according to claim 1, wherein the phosphoric acid or a derivative thereof is phosphoric anhydride,
2. A phosphoric acid such as orthophosphoric acid, pyrophosphoric acid and tripolyphosphoric anhydride, a phosphate, or a phosphoric acid ester.
The hydrophilic paint according to the above. 4. After coating a hydrophilic paint composed of an aqueous solution in which silicate and phosphoric acid or a derivative thereof are dissolved on the surface of the substrate, the substrate itself or the surface of the substrate is heated at a temperature within the range of 50 ° C. to 600 ° C. A method for producing a hydrophilic substrate, which comprises performing a heat treatment. 5. The method for producing a hydrophilic substrate according to claim 4, wherein the substrate is any one of glass, resin, metal, or a composite thereof.