JPH0826774A - Production of water-repellent article - Google Patents

Abstract

PURPOSE:To obtain a water-repellent article with a water-repellent coating film excellent in durability such as weather, moisture and water resistances. CONSTITUTION:A substrate is immersed in an aq. soln. of hydrosilicofluoric acid contg. silicon dioxide and a silicon dioxide film is formed on the surface of the substrate. The surface of the silicon dioxide film is then coated with fluoroalkylsilane to produce a water-repellent article. In this method, the substrate with the formed silicon dioxide film is coated with the fluoroalkylsilane while sticking hyclrosilicofluoric acid or hydrofluoric acid to the surface of the substrate.

Description

Detailed Description of the Invention

[0001]

This invention relates to water repellent articles, especially construction,
Windshields for cars, vehicles, aircraft or ships,
Optical parts such as lenses, glass for electric equipment, glass bottles and other glass products, and transparent or opaque products such as ceramic products are coated with a water-repellent coating with excellent durability such as weather resistance, moisture resistance, water resistance, and abrasion resistance. The present invention relates to a method for producing a water-repellent article.

[0002]

2. Description of the Related Art When the surface of a glass material is made water repellent,
1) Water drops containing contaminants do not remain on the glass surface, so it has the effect of preventing glass contamination and burning. 2) When water-repellent glass is used for automobile windshields, side glasses, etc., even in rainy weather. Various effects can be expected, such as rainwater adhering to the glass surface being blown off by wind pressure, the driver's field of view being secured, and running stability being improved. As a method for producing such water-repellent glass, a water-repellent agent composed of an organic silicone compound mainly containing polymethylsiloxane or a fluorine-containing silicone compound is wet-coated on the glass surface or is dry-coated by plasma or vapor deposition. Are generally used. However, in the method of directly applying the water repellent agent to the glass, it is difficult to maintain the water repellent performance for a long period of time because the water repellent agent and the glass have weak adhesion.

In order to solve such a problem, the water repellency is improved by increasing the bondability with the surface of the base material and preventing the components that deteriorate the water repellent film from being eluted from the base material into the water repellent film. Materials that have good binding properties with agents and materials that have high impurity shielding properties (1)
A method has been devised in which a film is formed on a substrate in advance, or (2) a mixture with a water repellent is applied to the substrate. For example (1)
For example, a silicon oxide film is formed and then a silicone water repellent is applied (JP-A-5-24885), and a substrate is immersed in a silicon dioxide supersaturated aqueous solution of hydrosilicofluoric acid for a predetermined time. To form a dense silicon oxide film on the surface of a base material and then coat it with an alkoxysilane or other organic silicon compound (Japanese Patent Application Laid-Open No. 5-97477), (2)
As a film by a so-called sol-gel method, for example, a mixture of an alkoxysilane compound and a fluoroalkylsilane compound is hydrolyzed (JP-A-4-33813).
7) or a fluoroalkyl group-containing silicon oxide film formed by applying a fluoroalkoxysilane modified silanol oligomer (Japanese Patent Publication No. 63-24554) synthesized by reacting a fluoroalkylsilane with a hydrolyzed alkoxysilane compound Can be mentioned.

[0004]

[Problems to be Solved by the Invention] However, (1)
Although the method of (2) provides a certain degree of durability, it forms a two-layer film, so that the formation of a silicon oxide film and the like and the application of the water repellent agent are performed separately.
It becomes a process. Further, in the method (2), a catalyst is required for producing the coating solution, the film forming step takes time, and baking is required after coating, so that the step is complicated and costly.
Further, as the fluoroalkylsilane and the alkoxysilane are partially hydrolyzed, the fluoroalkylsilane and the alkoxysilane are partially bound to each other, so that the fluoroalkyl group is taken into the formed film, and the firing temperature can be raised only up to about 250 ° C. Since the denseness of the silicon oxide film formed for such reasons is not sufficient, diffusion of impurities such as alkali that deteriorates the water repellent film from the base material into the water repellent film is fast, and the durability of the water repellent film is improved. It will be low.

An object of the present invention is to provide a water-repellent article on which such a defect is eliminated and which is provided with a water-repellent coating having excellent durability such as weather resistance, moisture resistance and water resistance.

[0006]

According to the present invention, a substrate is immersed in an aqueous solution of hydrosilicofluoric acid containing silicon dioxide to form a silicon dioxide film on the surface of the substrate, and then the substrate is washed. It has been found that a water-repellent article having a fluoroalkyl group on the surface of a base material and having excellent durability can be obtained by contacting with a fluoroalkylsilane compound before or during washing.

That is, in the present invention, the substrate is immersed in an aqueous solution of hydrofluoric acid containing silicon dioxide to form a silicon dioxide film on the surface of the substrate, and then a fluoroalkylsilane is formed on the surface of the silicon dioxide film. In the method for producing a water-repellent article for coating, the substrate on which the silicon dioxide film is formed is coated with the fluoroalkylsilane in a state where hydrosilicofluoric acid or hydrofluoric acid is attached to the surface of the substrate. It is a manufacturing method of a water-repellent article.

There are roughly two methods for forming a silicon dioxide film on the surface of a substrate by immersing the substrate in an aqueous solution of hydrofluoric acid containing silicon dioxide. One is a method of immersing a base material in an aqueous solution of hydrofluoric acid containing silicon dioxide in supersaturation to deposit and grow a silicon dioxide film on the surface of the base material (hereinafter referred to as "precipitation method"). , Others, a method of immersing a silicate glass substrate in an aqueous solution of hydrosilicofluoric acid containing silicon dioxide in a saturated state, and modifying the surface layer of the substrate into a porous silicon dioxide layer (hereinafter referred to as "erosion method"). "), And the silicon dioxide film in the present invention may be formed by either the above-mentioned precipitation method or erosion method.

In the present invention, the thickness of the silicon dioxide film may be any number in order to bond silanol groups to the surface of the base material, but in order to prevent the elution of impurities such as alkali from the base material, it should be 30 nm or more. desirable.

The fluoroalkylsilane used in the present invention comprises one fluoroalkyl group (R) represented by the formula (1), 0 to 2 methyl groups, and at least one functional group (X). It is a silane. R-Si (CH3) m (X) 3-m (1) (wherein R: fluoroalkyl group, X: -OCH3,
-OC2H5, -OCOCH3, -OCOC2H5, -C
1 or -OH, m is 0, 1 or 2)

Fluoroalkylsilane methyl group (--C
H3) is inactive and does not significantly affect the effect of the fluoroalkyl group (R), but the larger the number of functional groups (X), the easier it is to immobilize, so the number of methyl groups (m) is small. Reasonably, most preferably m is zero.

The fluoroalkyl group is a group in which some hydrogen atoms of the alkyl group are replaced by fluorine atoms, and is preferably represented by the formula (2). Rf:-(CH2) 2 (CF2) nCF3 (2) (where n is zero or a positive integer)

That is, in the linear alkyl group, a hydrogen atom bonded to a terminal carbon atom excluding two carbon atoms on the silicon atom side is preferably replaced by a fluorine atom. For example,-(CH2) 2CF3,-(CH2) 2 (CF2)
2CF3,-(CH2) 2 (CF2) 5CF3,-(CH2) 2
(CF2) 7CF3 and the like, among which — (CH
2) 2 (CF2) 5CF3 and-(CH2) 2 (CF2) 7CF3 are particularly preferable. The reason is that the compound tends to exist stably due to the presence of-(CH2) 2- on the silicon atom side in the fluoroalkyl group.

In the present invention, innumerable silanol groups are bound to the surface of the silicon dioxide film formed on the surface of the substrate by the precipitation method and the erosion method, and hydrosilicofluoric acid or hydrofluoric acid is present around it. Is attached. When it is brought into contact with fluoroalkylsilane in that state, the functional group (X) of the above formula (1) is
(Excluding -OH group) is hydrolyzed using hydrofluoric acid or hydrofluoric acid as a catalyst, and the hydrolyzed fluoroalkylsilane is combined with a silanol group on the film surface by a dehydration condensation polymerization reaction to form an Si-O-Si bond. And a fluoroalkyl group is immobilized. Immediately after the silicon dioxide film is formed, highly reactive silanol groups are present on the surface of the film, so the silicon dioxide film is bonded by contacting it with a fluoroalkylsilane without cleaning the substrate formed on the surface. Becomes stronger, and water repellency with excellent durability can be obtained.

Hydrofluoric acid and hydrofluoric acid attached to the surface of the silicon dioxide film are effective even in a very small amount, and the film surface is 1 cm 2
Approximately 1 μg per tens of thousands of molecules is sufficient. If the substrate with the silicon dioxide film formed on the surface is washed, hydrosilicofluoric acid and hydrofluoric acid remaining on the surface are completely removed, and the reactivity of silanol groups on the film surface becomes low, Even if a fluoroalkylsilane is brought into contact with the base material, the adhesive force is small and excellent water repellency cannot be obtained.

In the present invention, next, as a method for forming a water repellent layer by coating the surface of a silicon dioxide film with a fluoroalkylsilane, a substrate having a silicon dioxide film formed on the surface is placed in these solutions. A method of dipping, a method of pouring a solution onto the surface of the base material, a method of bringing vaporized vapor into contact with the surface of the base material, and the like can be used. In the case of using the method of dipping in the solution or the method of pouring the solution onto the surface of the base material, the treatment time for forming the water-repellent layer can be adjusted by diluting with a solvent. When no solvent is used or when diluting with a small amount of solvent, the concentration of fluoroalkylsilane increases and the amount of contact with the base material increases, so water repellent performance can be obtained in a short time, but on the other hand However, care must be taken because the fluoroalkylsilane is likely to undergo polycondensation. Further, when the concentration of fluoroalkylsilane becomes low, the occurrence of polycondensation can be suppressed and the water repellent layer can be made uniform, but it is necessary to lengthen the treatment time. When a long processing time is required, the method of dipping in the solution is preferable. The concentration of the fluoroalkylsilane is not particularly limited in order to obtain the water repellent performance, but the concentration is 0.1 to 1.0 volume in consideration of the treatment time, the uniformity of the water repellent layer, the effective use of the water repellent and the like. %, And the treatment time is preferably about 0.5 to 10 minutes. Any solvent may be used as long as it is an organic solvent in which the fluoroalkylsilane is soluble.
For example, ethyl alcohol, isopropyl alcohol, hexane and the like. The coating thickness (or laydown) of fluoroalkylsilane may be a monolayer or tens of angstroms, or even higher.

The above-mentioned treatment for forming the water repellent layer by coating the fluoroalkylsilane uses hydrofluoric acid or hydrosilicofluoric acid adhering to the surface of the silicon dioxide film of the base material as a catalyst.
It is necessary that hydrofluoric acid and hydrosilicofluoric acid remain on the surface of the substrate. Therefore, part of the aqueous solution of hydrosilicofluoric acid containing silicon dioxide used to form the silicon dioxide film is the substrate. Do not clean the substrate adhered to the surface, or do not completely clean it even if it is cleaned. Further, when the dipping method is used for the method of forming the water-repellent layer, a bath of an aqueous solution of hydrosilicofluoric acid containing silicon dioxide, a bath of fluoroalkylsilane,
If the cleaning baths (water tanks) are installed adjacent to each other in that order, the cleaning process after the silicon dioxide film is formed and the water repellent process can be performed in the same process, so the work is not complicated. In addition, since the reaction takes place in the liquid, the deposition method and the erosion method are characterized by large area, large-scale film formation is possible, and even on a substrate with many irregularities, it is possible to form a film evenly over steps. Is also obtained in the water repellent treatment. Furthermore, since the fluoroalkylsilane is already bonded to the silanol groups on the surface when it comes into contact with the surface of the substrate, there is no need to bake it thereafter, so the entire process is a low temperature treatment, so the cost is low.

Further, the silicon dioxide film formed by the precipitation method and the erosion method prevents components that deteriorate the water repellent layer, for example, alkali components in the case of an alkali-containing glass base material, from eluting from the inside of the base material to shield impurities. Because it improves the
The bondability with the water repellent is improved, and the durability of the water repellent layer is improved.

[0019]

According to the present invention, a water-repellent article having a water-repellent layer having excellent durability, in which a water-repellent agent is strongly bonded to a silicon dioxide film, can be obtained by low-temperature treatment.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The contact angle was measured to evaluate the water repellency, and the contact angle was measured after the sample was immersed in boiling water for 4 hours for boiling resistance. The contact angle was measured using a contact angle meter (CA-D manufactured by Kyowa Interface Science Co., Ltd.) and the contact angle of water was measured by the sessile drop method. One sample was measured at 3 to 5 points, and the average value was used as the value of the contact angle.

Example 1 50 ml of a 3.9 mol / l hydrofluoric acid aqueous solution in which silicon dioxide was saturated and dissolved was kept warm at 35 ° C., and water at 35 ° C. was heated to 50 m.
1 was added to prepare an aqueous solution of hydrosilicofluoric acid containing 1.95 mol / l of silicon dioxide in supersaturation. This aqueous solution 3
The glass substrate was immersed in the liquid while maintaining it at 5 ° C., maintained for about 2 hours, and then pulled out of the liquid. About 10 on the substrate surface
The 0 nm thick silicon dioxide film was covered. Without cleaning this substrate, heptadecafluorodecyltrimethoxysilane [CF3 (CF2) 7CH2CH2Si (OCH3) 3]
1 ml of ethyl alcohol [C2H5OH] 100
The substrate was taken out and washed with water after being immersed in a solution diluted and dissolved in ml and held for 1 minute. The results of measuring the contact angle and boiling resistance of this water-repellent glass are shown in Table 1.

Comparative Example 1 As in Example 1, a glass substrate covered with a silicon dioxide film having a thickness of about 100 nm was washed with water, and then 1 ml of heptadecafluorodecyltrimethoxysilane was diluted and dissolved in 100 ml of ethyl alcohol. The substrate was taken out and washed with water after being dipped in and kept for 1 minute. No water repellent layer was formed on the surface of this substrate. The surface of the substrate dried without washing with water was only wiped lightly, and the heptadecafluorodecyltrimethoxysilane on the surface was detached from the substrate.

Example 2 Float plate glass 20 cm × 20 cm and 3 mm thick (soda lime silicate glass, silica content about 72% by weight)
Was immersed in a 1.0% aqueous solution of hydrofluoric acid (HF) for 30 minutes to remove stains on both surfaces and then washed with water. The etching amount of the glass at this time was 6 μm. Then 2.0 at 35 ° C
Sodium silica powder was dissolved in hydrofluoric acid at a concentration of mol / l until it reached saturation, that is, dissolved at 20 g / l, and further immersed in a supersaturated aqueous solution of silica prepared by adding 5 × 10 ⁻³ mol / l of boric acid for 120 minutes. Then, a porous silica layer was provided on the glass surface. The thickness of the porous layer obtained at this time is about 130.
It was 0 angstrom. Also, the pore size is about 50-4
Many of them were 00 angstroms.

Without washing this substrate, 1 ml of heptadecafluorodecyltrimethoxysilane was immersed in a solution of 100 ml of ethyl alcohol diluted and dissolved, and after holding for 1 minute, the substrate was taken out and washed with water. The results of measuring the contact angle and boiling resistance of this water-repellent glass are shown in Table 1.

Comparative Example 2 As in Example 2, a glass substrate covered with a porous silicon dioxide film having a thickness of about 1300 angstrom was once immersed in a water bath for washing, and then 1 ml of heptadecafluorodecyltrimethoxysilane was added to 100 ml of ethyl alcohol. After dipping in a solution that had been diluted and dissolved in and holding for 1 minute, the substrate was taken out and washed with water. No water repellent layer was formed on the surface of this substrate.

[0026]

[Table 1]

Comparative Example 3 Tetraethoxysilane [Si (OC2H5) 4)] 10
0 g, heptadecafluorodecyltrimethoxysilane
[CF3 (CF2) 7CH2CH2Si (OCH3) 3]
2.73 g and 853.2 g of ethyl alcohol were mixed and stirred for 30 minutes. Then, 52.7 g of 0.1 N hydrochloric acid aqueous solution and 42.5 g of water were further added, and the mixture was stirred for 2 hours. This solution was left to seal and stand at 5 ° C. for 5 days and then diluted 5 times with ethyl alcohol to obtain a coating solution. This was applied onto a glass substrate by flow coating (flow coating) and heated at 250 ° C. for 1 hour.

Comparative Example 4 As in Example 1, the surface of the glass substrate which was covered with a silicon dioxide film having a thickness of about 100 nm and then washed was washed with a small amount of a polydimethylsiloxane water repellent, Superrain X (manufactured by unelko). Wipe with a soaked bencot paper and apply. After a few minutes, the water repellent remaining on the surface was wiped off with a clean paper. The water-repellent surface was wiped with paper impregnated with the water repellent, and after 10 minutes, the water repellent remaining on the surface was wiped with clean paper. The results of measuring the contact angle and boiling resistance of this water-repellent glass are shown in Table 1.

Comparative Example 5 50 ml of a 3.9 mol / l hydrofluoric acid aqueous solution in which silicon dioxide was saturated and dissolved was kept warm at 35 ° C., and water at 35 ° C. was added to 50 m.
1 was added to prepare an aqueous solution of hydrosilicofluoric acid containing 1.95 mol / l of silicon dioxide in supersaturation. This aqueous solution 3
Immerse the glass substrate in the liquid while maintaining it at 5 ℃,
After maintaining it for 0 minutes, it was taken out of the solution. About 1 on the substrate surface
The silicon dioxide film with a thickness of 00 nm was covered. Hexyltrimethoxysilane [CH3
0.1 ml of (CH2) 5Si (OCH3) 3] was immersed in a solution prepared by diluting with 100 ml of ethyl alcohol [C2H5OH] and held for 1 minute, and then the substrate was taken out and washed with water. The results of measuring the contact angle and boiling resistance of this water-repellent glass are shown in Table 1.

From the measurement results of the initial contact angle and boiling resistance of the water-repellent glass produced as described above (Table 1), the contact angle after boiling of the example was larger than that of the comparative example. It can be seen that the manufactured water-repellent article has water-repellent performance with excellent durability.

Claims (1)

[Claims] 1. A substrate is immersed in an aqueous solution of hydrosilicofluoric acid containing silicon dioxide to form a silicon dioxide film on the surface of the substrate, and then the surface of the silicon dioxide film is coated with a fluoroalkylsilane. In the method for producing an aqueous article, the substrate having the silicon dioxide film formed thereon is coated with the fluoroalkylsilane with hydrosilicofluoric acid or hydrofluoric acid attached to the surface thereof. Manufacturing method.