KR20000037783A - Preparation method of water repellent glass - Google Patents

Abstract

PURPOSE: A method for preparing water repellent glass and the water repellent glass prepared by the method are provided, which water repellent glass is improved in the durability, is free from haze and rainbow phenomena, is uniform and has good light-transparency. CONSTITUTION: A method comprises the steps of preparing the silica solution by hydrolyzing and condensing alkoxide-type silane compound in the presence of a basic catalyst and condensing it in the presence of an acidic catalyst; preparing the silica coating solution by mixing 1-9 wt% of the silica solution with 1-9 wt% of the mixture of 1-9 wt% of acetic acid and 1-9 wt% of alcohol; coating the surface of glass with the silica coating solution; heating the coating at the temperature of 100-300°C to obtain a silica coating; and coating the water repellent layer on the silica coating.

Description

Method for producing water repellent glass and water repellent glass produced thereby

The present invention relates to a method for producing a water-repellent glass having a silica coating film having a sufficient hardness and durability, homogeneous and excellent light transmittance even by low temperature heat treatment, and a water-repellent glass prepared therefrom.

Water repellent glass is a glass manufactured to apply water repellent material on the glass surface to express water repellency. The water-repellent glass is a glass that solves the problem of visual disturbance caused by the spread of water on the glass surface. It can be used for automobile glass, building glass, aircraft, ship, etc., and it can also be used to protect glass appliances from natural corrosion caused by water. Do. If only the water repellent is coated on the surface of the glass as it is, the alkali component in the glass is eluted, and as time passes, the bond between the glass and the water repellent is broken and the water repellent membrane is damaged, the contact angle with water droplets is lowered, and the water repellency is remarkably reduced. Will be lost.

Therefore, it is essential to extend the durability of the water-repellent glass to effectively block the alkali component from the inside of the glass and to prevent moisture from penetrating into the water-repellent portion. To this end, a method of forming a separate silica film using an alkoxysilane compound between the water repellent film and the glass surface and then forming a water repellent film thereon is commonly used.

Recently, in particular, a method of increasing the surface area for forming irregularities on the surface of the silica film and bonding with the water repellent agent has been proposed. For example, Japanese Patent Laid-Open Nos. Hei 5- 213633 and Hei 7-267684 use silica having different molecular weights. A method of forming fine concavities and convexities using a different point of condensation due to a difference in molecular weight during heat treatment by using a mixed solution is proposed. However, this method is difficult to prepare silica solutions of different molecular weights under the same liquidity (acidity), and it is cumbersome to prepare each solution. Particularly, the silica solution obtained by this method is condensed through a heat treatment process after coating. Since the surface irregularities are formed in the degree to which the difference occurs, the heat treatment must be performed at a high temperature of 400 ° C. or higher, and such high heat treatment temperature cannot be applied to laminated glass or tempered glass, which is an automotive glass. In addition, Japanese Patent Application Laid-open No. Hei 9-132433 uses alkoxysilanes having different alkyl groups as starting materials to facilitate the production of silica solutions having different molecular weights, which were problems in Japanese Patent Laid-Open Nos. Hei 5-213633 and Hei 7-267684. Therefore, a method of preparing silica solutions having different molecular weights and then mixing them has been proposed, but this method also has a problem in that irregularities are formed only after high temperature heat treatment.

In order to solve this problem, the present inventors earnestly studied, and the silica solution was obtained by a two-step process prepared by hydrolysis and polycondensation under a basic catalyst and then polycondensation under an acidic catalyst and then mixed with an acetic acid-containing alcohol solution. The present invention has been found to be a homogeneous silica membrane which is not only simple in terms of process but also excellent in durability at low heat treatment temperature and excellent in light transmittance, thereby completing the present invention.

An object of the present invention is to provide a method for producing a water-repellent glass having a homogeneous silica coating film having excellent hardness and durability and excellent light transmittance even by heat treatment at a relatively low temperature.

1 is a view showing the surface irregularities formed when coating the silica solution formed by the two-step process according to the present invention,

Figure 2 is an AFM (Atomic Force Microscopy) photograph of the silica membrane before the heat treatment after coating the silica solution prepared according to the present invention,

3 is an AFM photograph of a silica membrane coated with a silica solution obtained by hydrolyzing and polycondensing a silane compound under basic conditions,

4 is an AFM photograph of a silica membrane coated with a silica solution obtained by hydrolyzing and polycondensing a silane compound under acidic conditions.

In order to achieve the above object, in the present invention, in the method for producing a water-repellent glass by sequentially coating a silica film and a water-repellent film on the glass substrate surface, the alkoxide-based silane compound is hydrolyzed and polycondensed under a basic catalyst and then under an acidic catalyst The polycondensation yields a silica solution, and the solution is mixed with a mixed solution of acetic acid and alcohol to provide a silica coating solution on a glass substrate and then subjected to heat treatment to provide a silica membrane.

Hereinafter, the present invention will be described in more detail.

(A) Silica Solution Preparation

According to the present invention, the coating silica solution for forming the silica film of the water-repellent glass is obtained by the two-step process of the alkoxide-based silane compound. Examples of alkoxide-based silane compounds used as starting materials for preparing a silica solution include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, and the like.

In the two-stage process of the present invention, firstly, the first step is a step of hydrolyzing and polycondensing an alkoxide-based silane compound under a basic catalyst. Specifically, the silane compound is mixed with an alcoholic organic solvent such as ethanol and then stirred at room temperature. The pH of the mixed solution is adjusted to 9 to 13 by adding a basic catalyst and water for hydrolysis thereto, followed by hydrolysis and polycondensation at a temperature in the range of 20 to 80 ° C. for 6 to 48 hours.

Examples of the basic catalyst include sodium hydroxide, potassium hydroxide, ammonia water, and the like, which is preferable because of the advantage that the ammonia water does not remain in the silica film due to volatilization by drying and firing in the silica film forming step.

The silica solution produced in the first step forms the spherical polymer colloidal silica as a result of the hydrolysis and polycondensation of the silane compound.

The second step is then carried out by adding an acidic catalyst to the silica solution prepared by the first step to adjust the pH to 1-4 and then polycondensing at low temperatures in the range of 2-10 ° C. for 1-24 hours.

Examples of the acidic catalyst include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, and the like.

In the second step, incompletely grown silica particles in addition to spherically grown colloidal silica particles are grown to polysiloxane as linear silica by acid.

Therefore, the silica solution prepared in two steps according to the present invention is a form in which spherical silica particles and linear silica coexist together, and the irregularities are formed on the surface of the coating film when the glass substrate is coated due to the characteristics of the solution.

(B) Mixture with acetic acid-alcohol

The silica solution prepared as described above is subjected to a process of mixing with a mixed solution of acetic acid and alcohol in order to use in forming the silica film.

Acetic acid contained in the silica solution enhances the wetting properties of the silica solution and delays the rapid volatilization of the alcohol in the solution, thereby enhancing the leveling effect that allows the silica solution to be coated sufficiently evenly on the glass substrate surface. Therefore, when the silica film is formed on the surface of the glass substrate using the silica solution according to the present invention, the film is uniformly formed even when coated with a thickness of a predetermined value or more, which can exhibit durability as the water-repellent glass, thereby causing problems such as a conventional haze or rainbow phenomenon. It does not occur and a silica coating film excellent in light transmittance can be obtained.

The mixing ratio of the silica solution and the acetic acid-alcohol mixed solution is in the range of 1: 9 to 9: 1 weight ratio, and when the silica solution is used less than the above range, the coating solution is too thin to form an overly thin film, When used a lot, the mixed solution may not be enough to cause coating defects.

In addition, the mixing ratio of acetic acid and alcohol in the acetic acid-alcohol mixed solution is in the range of 1: 9 to 9: 1 weight ratio. If acetic acid is used less than the above ratio, coating defects may occur due to the rapid volatilization rate of alcohol, and if it is used more than the above ratio, the volatilization rate of alcohol is too slow, and foreign substances in the air are mixed or pores are formed in the coating membrane during drying of the membrane. Defects can occur.

Mixing of the acetic acid-alcohol solution and the silica solution should be mixed after the preparation of the silica solution is completed. If the alcohol to be mixed is used early in the preparation of the silica solution, the concentration of the reactants is lowered, thereby lowering the degree of polymerization of the colloidal silica and the formation of irregularities of the silica coating film, thereby lowering the durability of the water repellent film. When used as a catalyst, the reaction of acetic acid is weak, so that the growth of linear polysiloxane does not easily occur, and only spherical colloidal silica particles remain, resulting in a non-uniform and dense silica film.

(C) Formation of Silica Film

The silica coating solution of the present invention prepared as described above can form a silica film by coating on a glass substrate by a conventional method. Examples of the coating method include a deposition method, a spin method, a shedding method, a spray method and the like. In particular, in the case of the spray method, conventional silica coating solution causes various problems such as clogging of the injection nozzle during injection, non-uniformity of the formed silica film, and the like, and the silica film coating solution prepared according to the present invention may be coated by spraying. A homogeneous coating film can be produced without such a problem.

In the silica coating solution of the present invention, spherical silica particles form a large aggregate by the electrostatic force between particles, thereby forming irregularities on the surface of the coating film when coating on the substrate, and linear silica crosslinks between particles or between aggregates of the spherical silica particles. This improves the density of the silica film. Surface irregularities formed when coating the silica solution according to the present invention is shown in Figure 1, Figure 2 is an AFM (Atomic Force Microscopy) of the silica film before the heat treatment after coating the silica solution. As can be seen in Figure 2, the silica film coated with a silica solution aged according to the present invention is already formed on the surface of the coating film before the heat treatment.

On the other hand, unlike in the present invention, the silica solution prepared by hydrolysis and polycondensation under basic conditions only has spherical silica particles, so that the hardness and density of the coating film during coating are easily lowered from the glass substrate (see FIG. 3). In the case of a silica solution prepared by hydrolysis and polycondensation only under an acidic catalyst, surface irregularities are not formed upon coating (see FIG. 4). In contrast, the silica solution of the present invention prepared in two steps under basic conditions and acidic conditions not only forms irregularities well during coating but also improves the film density.

(D) Heat treatment of silica film

As described above, the silica film coated with the silica coating solution of the present invention is formed with irregularities on the surface of the coating film before the heat treatment process, in order to enhance the density and hardness of the silica coating film, such as tempered glass or safety glass The heat treatment of the silica film is carried out within a temperature range in which the glass does not lose its function.

That is, the coated silica film is dried and heat treated by a conventional method. Drying is carried out at room temperature for about 10 minutes, heat treatment is carried out for 10 to 60 minutes at a temperature in the range of 100 to 300 ℃, preferably 100 to 120 ℃. If the heat treatment temperature is 100 ℃ or less, the solvent in the solution is not completely volatilized to produce a film having a low density and hardness, and a high heat treatment temperature of 300 ℃ or more can lose the reinforcing function in the case of tempered glass such as automotive side glass In particular, when manufacturing safety glass such as a windshield of the car, since the bonding film inserted between the glass may be damaged, heat treatment is preferably performed at 120 ° C. or lower. In addition, since the silica film has sufficient hardness even with a heat treatment in the range of 100 to 300 ° C., heat treatment at a temperature higher than that is economically inadequate.

(E) Thickness and Physical Properties of Silica Film

According to the present invention, the film thickness of the silica film formed by the above process is preferably in the range of 400 to 900 kPa. If the thickness is thinner than the above range, it is not preferable because it is difficult to sufficiently improve the durability and if it is too thick, the film may be inhomogeneous and the film forming state may be defective.

The silica film formed according to the present invention, when measured by atomic force microscopy, has a surface roughness in the range of 25 to 100 Hz (center line average roughness, Ra).

Ra is a representative value of surface roughness, but it treats peak and valley of unevenness equally, so it does not give information on the shape of the acid worn by direct contact with the outside (ie It is not enough to explain the structure containing water repellent in between to maintain water repellency for a long time and receive less abrasion). The surface unevenness of the silica film increases the surface area of the silica film to increase the durability of the water-repellent glass.The surface area increases with the Ra value, so the durability should be improved. This falls and you have a sex muscle structure.

On the other hand, in consideration of this point, the present inventors evaluated the surface asperities as Rsk values indicating the peaks and valleys of the asperities, which can explain the shape of the asperities in addition to the surface roughness.

The Rsk value is measured as (+) and (-) values of the up and down bias with respect to the center line of the unevenness, and is expressed as an average of the sum of the cubes of these values, respectively (zero if symmetrical from the center line, or biased to either side). It represents a positive or negative value, and if the mountain protrudes more than the valley around the center line, it will have a positive value and vice versa.

In particular, the surface unevenness of the silica coating film produced according to the present invention has a Rsk value of -1 or more and less than zero (-1? Rsk <0). This is because the depth of the bone is greater than the protruding portion of the mountain, this structure is a structure that can exhibit excellent durability because there is less wear surface protruded to the outside and excess water repellent fluid contained between the bone.

As a result, the surface unevenness of the silica coating film prepared according to the present invention is particularly strong in producing durable water-repellent glass because the depth of the bone is greater than the protruding portion of the acid, which is resistant to abrasion and may contain a water-repellent liquid between the bones. It is a preferred form.

(F) formation of a water repellent film

The water-repellent film is coated on the silica film formed as described above to manufacture a water-repellent glass. A water-repellent film may be used to form a water-repellent film, and specific examples thereof may include those obtained by hydrolyzing a fluorosilane compound represented by the following Chemical Formula 1. have.

CF ₃ (CF ₂ ) _n (CH ₂ ) _m Si (OC _x H _2x ) _4-p (C _y H _2y ) _p

At this time, 0 <n ≤ 13, 0 <m ≤ 4, 0 <x ≤ 4, 0 <p ≤ 4

The compound represented by Chemical Formula 1 may be hydrolyzed and applied onto the silica coating film by a conventional method such as spraying, spinning, dipping, or shedding, and may be water-repelled by drying for about 30 minutes in a range of 100 to 170 ° C. A film can be formed.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited thereto.

Example 1

(1) Preparation of Silica Coating Solution

10 wt% of tetraethoxysilane (TEOS) was added to 90 wt% of ethanol, followed by stirring for 30 minutes. After sufficient mixing, 0.5% by weight of ammonia water was slowly added dropwise to the solution while stirring, followed by stirring at room temperature for 1 hour to sufficiently react. Subsequently, 3.2 wt% of distilled water was added thereto, stirred for 2 hours, completely sealed, placed in a thermostat maintained at 30 ° C., and hydrolyzed and polycondensed for 24 hours to prepare a colloidal silica solution.

After the reaction was completed, the colloidal silica solution was cooled to room temperature in air, and then slowly added dropwise thereto while stirring 1% by weight of hydrochloric acid. At this time, the agitation was performed in an unopened state so that the white smoke of NH ₄ Cl did not remain in the solution. After all the white smoke disappeared, the mixture was stirred for 1 hour and further polycondensed at a refrigeration temperature (5 ° C.).

150 g of the silica solution thus obtained was combined with a mixed solution of 200 g of acetic acid and 650 g of ethanol prepared in advance to obtain a coating solution for forming a silica film.

(2) Formation of Silica Film

A 30 cm x 30 cm sized soda lime glass plate was removed from contaminants on the surface, washed several times with distilled water, and dried at room temperature. Washed with isopropyl alcohol and then the surface of the glass plate is completely dried, and then, above the above-mentioned (1) a silica film coating composition of the ^second pressure, the amount and 700cm / sec of 0.7 kg / cm ^2, a solution of 0.7 kg / cm manufactured by Spray coating at speed. The coated glass plate was heated at a rate of 7 ° C./min and then heat treated at 100 ° C. for 30 minutes to form a silica film on the glass substrate.

Example 2

In the same manner as in Example 1, the silica film was heat-treated at 300 ° C. instead of 100 ° C. to form a silica film.

Example 3

In the same manner as in Example 2, a silica film was formed using a silica coating solution obtained by combining 500 g of a silica solution with a mixture of 100 g of acetic acid and 400 g of ethanol.

Example 4

In the same manner as in Example 2, a silica film was formed using a silica coating solution obtained by combining 400 g of a silica solution with a mixture of 100 g of acetic acid and 500 g of ethanol.

Example 5

In the same manner as in Example 2, a silica film was formed using a silica coating solution obtained by combining 100 g of a silica solution with a mixture of 450 g of acetic acid and 450 g of ethanol.

Comparative Example 1

In the same manner as in Example 2, a silica film was formed using a silica coating solution in which 100 g of the silica solution was combined with 900 g of ethanol without acetic acid.

Comparative Example 2

In the same manner as in Example 2, the silica solution was coated on the glass substrate immediately without mixing with the acetic acid-ethanol solution to form a silica film.

Physical property test of silica film

The physical properties of the silica coating film formed in the Examples and Comparative Examples were measured as follows, and the results are shown in Table 1 below.

-Haze and Rainbow Phenomenon: The haze and rainbow phenomenon were examined by visual observation of the silica film.

-Light transmittance: The light transmittance (%) of the silica film was measured using the UV spectrometer.

Film thickness and refractive index: The thickness and refractive index of the silica film were measured using an ellipsometer (Plasmos, Germany, SD2100).

Ra (center line average roughness) and Rsk (acid and bone asymmetry): Measured using AFM (Atomic Force Microscopy; DI3000 from Digital Instrument).

Haze Rainbow Light transmittance (%) Film thickness Refractive index Ra Rsk Example 1 none none 93 646 1.4403 50 -0.36 Example 2 none none 92 810 1.4307 46 -0.42 Example 3 none none 92 870 1.4288 72 -0.81 Example 4 none none 91 740 1.4379 64 -0.64 Example 5 none none 92 720 1.4302 28 -0.27 Comparative Example 1 none has exist 87 120 1.3824 65 -0.32 Comparative Example 2 has exist has exist 85 1100 1.3520 114 -0.78

As described above, the water-repellent glass manufacturing method according to the present invention, by forming a silica film using a silica solution in which the spherical and linear silica obtained through the two-step process of the silane compound is formed on the surface of the silica coating film without a separate process Unevenness can be formed, resulting in a water-repellent glass with enhanced durability.

In addition, the method of the present invention is not only applicable to functional glass such as safety glass or tempered glass because the silica film has sufficient hardness and durability even after heat treatment at low temperature, and the two-step-treated silica solution is added to the mixed solution of acetic acid and alcohol. By using it, the coating property is improved, there is no haze and rainbow phenomenon, and it is homogeneous and has excellent light transmittance.

Claims (11)

In the method of manufacturing a water-repellent glass by sequentially coating a silica film and a water repellent film on the surface of the glass substrate, the alkoxide silane compound is hydrolyzed and polycondensed under a basic catalyst and then polycondensed under an acidic catalyst to obtain a silica solution, and the solution is acetic acid. A method for producing a water-repellent glass, characterized in that a silica film is obtained by coating a glass substrate with a silica coating solution produced by mixing with a mixed solution of alcohol and alcohol. The method of claim 1, A method in which the mixing ratio of acetic acid and alcohol used in the mixed solution of acetic acid and alcohol is in the range of 1: 9 to 9: 1 weight ratio. The method of claim 1, Mixing ratio of the silica solution and acetic acid-alcohol solution is 1: 9 to 9: 1 weight ratio range. The method of claim 1, Wherein the silica solution is prepared by hydrolyzing and polycondensing the alkoxide silane compound under basic conditions in the range of pH 9 to 13, followed by polycondensation under acidic conditions of pH 1 to 4. The method of claim 1, A method of coating a silica coating solution by spray coating. The method of claim 1, Characterized in that the heat treatment is carried out at a temperature in the range from 100 to 300 ° C. The method of claim 6, The heat treatment is carried out at a temperature of 120 ° C. or lower. The water-repellent glass manufactured by the method of any one of Claims 1-7 by which the silica film and the water-repellent film were sequentially coated on the glass substrate surface. The method of claim 8, A water-repellent glass, characterized in that the silica film has a surface roughness in the range of 25 to 100 GPa as measured as the centerline average roughness Ra. The method of claim 8, A water repellent glass, wherein a silica film has a skew value (Rsk) of an unevenness, which is an average of a value obtained by cubed up and down values based on the centerline of the unevenness, respectively. The method of claim 8, Water repellent glass, characterized in that the silica film has a thickness in the range of 400 to 900 kPa.