JP2000290592A - Production of coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a coating composition that is excellent in long-term storage stability with maintaining a high viscosity suitable for use in a general printing means or a general coating method and is free from any corrosive substance and that gives a coating film having excellent heat resistance and having high electrical insulation properties and high surface hardness. SOLUTION: A process for producing a coating composition comprises the step of carrying out hydrolysis of an metal alkoxide by using a low boiling solvent as a reaction solvent and adding, to the reaction solvent, a volatile catalyst, water and a metal alkoxide, the step of removing the low boiling solvent, the volatile catalyst and surplus water from the reaction system by adding a high boiling solvent to the reaction system and, furthermore, the step of proceeding to condensation polymerization of the reaction system by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal surface coating,
The present invention relates to a method for producing a coating composition used for various electronic devices.

[0002]

2. Description of the Related Art Conventionally, various coating compositions have been used for heat resistance. Among them, inorganic coating solutions produced by hydrolyzing metal alkoxides have been used particularly in fields requiring surface hardness, electrical insulation and heat resistance.

As an example of a conventional method for producing this type of coating liquid, a method described in Japanese Patent Application Laid-Open No. 5-140507 is known. In the conventional method for producing an inorganic coating solution described in this publication, methyl trimethoxysilane, organopolysiloxane, aluminum chelate, isopropyl alcohol and water are added to a reactor equipped with a reflux condenser and a stirrer, By heating to 5 ° C. and reacting for 5 hours, an inorganic coating solution was obtained.

[0004] Further, a method for producing a coating composition described in Japanese Patent Application Laid-Open No. H5-225434, which is disclosed as another conventional example, is a method of mixing an organoalkoxysilane, colloidal alumina, water and an alcohol and hydrolyzing the mixture. The polycondensation is performed, and hydrochloric acid is added to alkoxysilane and water as a catalyst, and the second stage hydrolysis and polycondensation are performed to produce a coating composition.

[0005]

The coating solution and the coating composition obtained by the above-mentioned conventional production methods have the following problems, and a method for solving them has been desired.

The first problem is that the viscosity of the above-mentioned conventional coating solution or coating composition is extremely low, and only spray coating or dip coating can be performed at the time of coating. It is not impossible to increase the apparent viscosity by adding large amounts of inorganic fillers to improve this, but the resulting mixture is either low in viscosity or poorly flowable. However, it was difficult to use as a general paint.

As another method of increasing the viscosity of a conventional inorganic coating composition, there is a method of increasing the viscosity by advancing a condensation polymerization reaction during production, but the coating composition obtained by this method has an extremely long shelf life. It is bad and gels in a short time, and has not been used industrially except for the production of some glass fibers.

A second problem is that the above-mentioned conventional inorganic coating solutions and coating compositions are unstable and have a short shelf life such as precipitation of metal oxide during storage.
The third problem is that the above-mentioned conventional inorganic coating solutions and coating compositions use acidic substances as catalysts and stabilizers at the time of production, so that the compositions themselves often have corrosive properties, such as metal thin films. It could not be applied on top.

The present invention solves the above-mentioned conventional problems and has high viscosity suitable for general printing means and coating methods, excellent long-term storage stability, and contains no corrosive substances. The object of the present invention is to provide a method for producing a coating composition having excellent heat resistance, high electrical insulation and high surface hardness.

[0010]

In order to achieve the above object, a method for producing a coating composition according to the present invention uses a low-boiling solvent as a reaction solvent, and contains an evaporable catalyst, water and a metal alkoxide in the reaction solvent. Adding and hydrolyzing the metal alkoxide, adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, evaporative catalyst and excess water from the reaction system, and further heating the mixture. According to this production method, it has a high viscosity suitable for general printing means and coating methods, has excellent long-term storage stability, and has a high corrosion resistance. The resulting coating film has no heat-resistant substance and has excellent heat resistance, and a coating composition having high electrical insulation and high surface hardness can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a low boiling solvent is used as a reaction solvent, and an evaporable catalyst, water and a metal alkoxide are added to the reaction solvent to hydrolyze the metal alkoxide. And a step of adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, evaporative catalyst and excess water from the reaction system, and further promote the condensation polymerization reaction of the reaction system by heating According to this production method, a low-boiling solvent is used as a reaction solvent, and an evaporable catalyst, water and a metal alkoxide are added to the reaction solvent to hydrolyze the metal alkoxide, and The high boiling point solvent is added to the reaction system to remove the low boiling point solvent, the evaporative catalyst and excess water from the reaction system, and the condensation polymerization reaction of the reaction system is further advanced by heating. By the polycondensation reaction, it is possible to maintain a high viscosity suitable for general printing means and coating methods, and to accelerate the gelation of the coating composition during long-term storage due to insufficient removal of water. As a result, it is possible to obtain a product with excellent long-term storage stability, and because it does not contain corrosive substances, the resulting coating film has excellent heat resistance, high electrical insulation and high surface hardness. It has the effect of obtaining a coating composition.

[0012] The invention according to claim 2 is a method wherein a solvent having a low boiling point is used as a reaction solvent, an evaporable catalyst in the reaction solvent, a metal oxide sol dispersed in water or a metal oxide dispersed in an organic solvent. Adding a sol, water and a metal alkoxide to hydrolyze the metal alkoxide, and adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, evaporative catalyst and excess water from the reaction system And a step of further promoting the condensation polymerization reaction by heating. According to this production method, a low-boiling solvent is used as a reaction solvent, and an evaporable catalyst is dispersed in the reaction solvent in water. A metal oxide sol or a metal oxide sol dispersed in an organic solvent, water and a metal alkoxide are added to hydrolyze the metal alkoxide, and a high boiling solvent is added to the reaction system to form a reaction system. To remove the low boiling point solvent, evaporative catalyst and excess water, and further promote the condensation polymerization reaction of the reaction system by heating, so that the metal oxide sol dispersed in water or dispersed in an organic solvent is used. The addition of the metal oxide sol and the polycondensation reaction of the reaction system can increase the solid concentration in the coating composition and maintain a high viscosity suitable for general printing means and coating methods. In addition, since the gelation of the coating composition during long-term storage due to insufficient water removal is not accelerated, a product having excellent long-term storage stability can be obtained, and corrosive substances can be obtained. , The resulting coating film has excellent heat resistance, and has the effect of obtaining a coating composition having high electrical insulation and high surface hardness.

(Embodiment 1) Hereinafter, a method for producing a coating composition according to Embodiment 1 of the present invention will be described in detail.

The method for producing a coating composition according to the first embodiment of the present invention basically uses a low-boiling solvent as a reaction solvent, and adds an evaporable catalyst, water and a metal alkoxide to the reaction solvent to form a metal. A step of hydrolyzing the alkoxide, a step of adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, the evaporative catalyst and excess water from the reaction system, and further reducing the reaction system by heating. And a step of promoting a polymerization reaction.

The low-boiling solvent as the reaction solvent used in the first embodiment of the present invention preferably dissolves both water for hydrolysis and metal alkoxide as a raw material of the coating composition, and If possible, an azeotropic composition with water is preferably used in order to efficiently remove water from the reaction system in the subsequent steps of removing the low-boiling solvent, the evaporable catalyst and the water. Examples thereof include lower alcohols such as methanol, ethanol, n- or iso-propanol and butanol, and water-soluble ketones such as acetone and methyl ethyl ketone. These low-boiling solvents can be arbitrarily selected depending on the type of metal alkoxide.

For example, alkoxides such as indium and zirconium do not dissolve in methanol and ethanol, so that propanol, butanol and the like must be used. In short, it is preferable to use a reaction solvent that dissolves both the metal alkoxide used and water. That is, if the reaction system is not uniform in the hydrolysis step, the hydrolysis reaction does not easily proceed smoothly. However, as described in Example 5 below, if the metal alkoxide is a liquid, it may be heterogeneous initially, but may be homogenized with the hydrolysis reaction.

As the evaporative catalyst, a lower carboxylic acid such as formic acid, acetic acid or propionic acid or an inorganic acid such as hydrochloric acid or nitric acid can be used. It is most convenient to use hydrochloric acid or acetic acid in consideration of cost, post-treatment and the like.

Examples of the metal alkoxide include methoxides of metals such as silicon, titanium, aluminum, calcium, barium, zirconium, cobalt, strontium, manganese, iron, tantalum, indium, tin, copper, zinc, yttrium, niobium, lanthanum, and tungsten. , Ethoxide, n- or iso-propoxide, butoxide and the like can be obtained as commercial products. Among the above metal alkoxides, metal alkoxides of silicon, titanium, aluminum, calcium, barium, and zirconium are particularly suitable for coating applications, and alkoxides of silicon, titanium, and aluminum are low in cost and convenient.

Metal alkoxides in which a part of the alkoxy group is substituted by an alkyl group or the like can also be used for improving the coating film properties. For example, methyl trialkoxy silane gives the coating flexibility and adhesion to the underlying material, and fluoroalkyl trialkoxy silane gives the coating water repellency, resulting It is possible to prevent insulation deterioration.

As the high boiling point solvent to be added to the reaction system using the above low boiling point solvent, it is preferable to use one having a boiling point at atmospheric pressure of 150 ° C. or higher. When the boiling point is low and at the same level as that of water, loss of the solvent is large when excess water is removed from the reaction system, and extra cost is required for recovery and disposal of the effluent solvent, which is economically disadvantageous. In addition, if the solvent flows out of the reaction system more than necessary, there is a problem that the reaction system is gelled, so that it is necessary to add an excess solvent from the beginning, which is further economically disadvantageous.

When the coating composition obtained in the first embodiment of the present invention is used as a paste or ink vehicle for screen printing, the high boiling solvent to be added to the reaction system may be a long-time continuous printing. It is preferable to use a solvent having a boiling point of 180 ° C. or higher in order to enable the above.

Specific solvents include high-boiling alcohols such as cyclohexanol, benzyl alcohol and terpineol, cyclic ketones such as cyclohexanone and isophorone, ethyl cellosolve, butyl cellosolve, butyl carbitol and acetates thereof. Examples include ethers and esters of ethylene glycol and diethylene glycol.

These high-boiling solvents need not necessarily be water-soluble, unlike the low-boiling solvents described above. That is, even if the reaction system becomes temporarily non-uniform due to the addition of the high boiling point solvent, the reaction system becomes uniform and transparent by removing excess water. Rather, water-insoluble ones are more convenient for the separation of the condensed water.

Next, the process conditions of the method for producing a coating composition according to the first embodiment of the present invention will be described.

First, a low boiling point solvent is measured and injected into a reaction vessel. Subsequently, the metal alkoxide is added to the low boiling point solvent while stirring. Depending on the reactivity of the metal alkoxide, an operation such as atmosphere replacement using dry air or nitrogen may be required at the time of addition. In general, in the case of silicon alkoxide, no particular care is required,
Since the alkoxide of titanium is sensitive to the humidity in the atmosphere, it is better to perform replacement with dry air or nitrogen.

Following the addition, water with the catalyst dissolved therein is added dropwise with stirring. Since heat is generated when the water is dropped, it is preferable to drop the water while keeping the reaction temperature at 40 ° C. or lower for the purpose of preventing runaway. Cooling may be required depending on the amount of the reaction system. After the required amount of water has been dropped, the reaction vessel is then stirred at 50 ° C to 60 ° C.
And the hydrolysis reaction proceeds. However, since the above hydrolysis reaction is almost completed at the time of dropping water,
No prolonged hydrolysis is required.

Following the addition of the water, a high boiling solvent is added to the vessel and the mixture is stirred at 60 ° C to 80 ° C.
To remove the low-boiling solvent, evaporative catalyst and excess water under reduced pressure. The completion of the removal of the excess water can be known from the rise in the degree of vacuum and the rise in the temperature of the reaction system. The step of removing the evaporable catalyst and excess water is one of the important processes in the first embodiment of the present invention, and if the water is not sufficiently removed, the coating composition may not be used during subsequent storage. The gelation of the material is accelerated, and the storage life is shortened.

After the step of removing the evaporable catalyst and excess water is completed, the temperature of the reaction system is further increased by heating.
The condensation polymerization reaction of the reaction system is advanced. The reaction temperature of the polycondensation reaction is preferably from 110 ° C to 150 ° C. In this case, when the reaction temperature is 110 ° C. or lower, the reaction is slow. On the other hand, when the reaction temperature is 150 ° C. or higher, the reaction may be so rapid that it may gel before cooling in the final stage. When the condensation polymerization reaction is also performed under reduced pressure under the reflux condition of the high boiling point solvent, separation of the condensed water is easily performed.

In the first embodiment of the present invention, the step of removing the evaporable catalyst and excess water was performed after the addition of the high boiling point solvent. After the removal step, a high-boiling solvent may be added.

The reaction solution which has reached the desired viscosity by the progress of the polycondensation reaction is cooled and taken out in a storage container to complete a coating composition.

In the above description of the process of the method for producing a coating composition according to the first embodiment of the present invention, a system in which water is added in the hydrolysis reaction stage has been described. However, the solid content concentration in the coating composition is described. When it is desired to increase the water, the aqueous sol such as silica sol, alumina sol, and zirconia sol in which the colloidal metal oxide is dispersed in water instead of the above water, or the colloidal metal oxide is dispersed in the organic solvent. An organosol may be used.
In the case of using the former aqueous sol, a catalyst such as hydrochloric acid is usually added for stabilizing the aqueous sol, so that it is not necessary to add an evaporable catalyst in the hydrolysis.
However, a stabilizer to which a non-volatile catalyst such as oxalic acid other than hydrochloric acid is added cannot be used in the present invention. On the other hand, when the latter organosol is used, it is necessary to separately add water and an evaporable catalyst.

Next, a specific embodiment of the present invention will be described.

Example 1 200.0 g of ethanol and 20 parts of tetraethoxysilane were placed in a 1-liter four-necked flask equipped with a stirrer, a reflux condenser, an exhaust port for reducing pressure, and a thermometer.
8.0 g, and the mixture was stirred while cooling the flask with a water bath, and 36.0 g of 1N hydrochloric acid was added to 30 g of the flask.
Dropped over minutes. During this time, the temperature inside the flask was raised from 20 ° C to 40 ° C. Subsequently, the internal temperature was raised to 70 ° C. by a water bath, and after stirring for 30 minutes, 60.0 g of diethylene glycol n-butyl ether was added, and ethanol and water were added at an internal temperature of 60 ° C. under a reduced pressure of 300 torr. Removed. At the final stage of this removal, the vacuum was reduced to 55 torr.

Thereafter, the heating source was changed to an oil bath, and heating was performed at 150 ° C. under atmospheric pressure, and the inside of the flask was refluxed at an internal temperature of 128 ° C. The reaction was carried out for 60 minutes while separating water from the reflux liquid, and then the flask was cooled to produce a coating composition.

The obtained coating composition (hereinafter referred to as composition 1) is a colorless and transparent high-viscosity liquid, and has a viscosity of 460 centipoise (0.46 Pa · s) as measured with an E-type viscometer manufactured by Tokyo Keiki. s). Thermogravimetric analysis showed that weight loss occurred at 230-260 ° C, and finally 43.2% solids remained. The viscosity of the composition 1 was stable without a rise in viscosity even after storage for 1 month in a room (25 to 30 ° C.).

To 50 g of Composition 1, 50 g of alumina fine powder (particle size: 0.5 μm) was added and kneaded by a three-roll mill to produce a printing paste. The paste obtained here had a viscosity of 120 Pa · s at a shear rate of 10 s ⁻¹ and had good leveling properties. This paste was printed on an aluminum plate by screen printing, dried at 150 ° C, and then cured at 300 ° C.
A smooth coating film was obtained.

(Example 2) 200.0 g of methyltrimethoxysilane and 60.0 g of ethanol were put into a 1-liter four-necked flask equipped with a stirrer, a reflux condenser, an evacuation port for reducing pressure, and a thermometer. 20% solids while stirring
60.0 g of silica sol was dropped over 30 minutes. During this time, the temperature inside the flask was raised from 20 ° C to 40 ° C. Subsequently, the internal temperature was raised to 60 ° C. in a water bath, and the mixture was stirred for 30 minutes. Then, 90.0 g of diethylene glycol n-butyl ether was added, and the degree of vacuum was set to 300 torr.
Under reduced pressure, ethanol and water were removed at an internal temperature of 60 ° C. At the final stage of this removal, the vacuum was reduced to 45 torr and the internal temperature was increased to 68 ° C.

Thereafter, the heating source was changed to an oil bath, and heating was performed at 150 ° C. under atmospheric pressure, and the inside of the flask was refluxed at an internal temperature of 128 ° C. The reaction was carried out for 120 minutes while separating water from the reflux liquid, and then the flask was cooled to produce 207 g of a coating composition.

The obtained coating composition (hereinafter referred to as composition 2) is a colorless and transparent high-viscosity liquid, and the viscosity was 900 centipoise (0.9 Pa. s). Thermogravimetric analysis showed that weight loss occurred at 250-300 ° C., and finally 48.1% solids remained. Composition 2 has a viscosity of 1
There was no increase in viscosity even when stored indoors (25-30 ° C.) for months, and the product was stable.

Example 3 A coating composition (hereinafter referred to as composition 3) manufactured in the same manner as in Example 2 except that the oil bath heating time in Example 2 was changed to 150 minutes, had a viscosity of 3200 centipoise (3). .2 Pa · s). Thermogravimetric analysis showed that weight loss occurred at 280-300 ° C., and finally 49.1% solids remained. The viscosity of Composition 3 increased three-fold after one month of room (25-30 ° C.) storage.

Example 4 200.0 g of methyltrimethoxysilane and 100.0 g of ethanol were put into a 1-liter four-necked flask equipped with a stirrer, a reflux condenser, an exhaust port for reducing pressure, and a thermometer. Solid content 20 with stirring
% Silica sol was dropped over 30 minutes.
During this time, the temperature inside the flask was raised from 20 ° C to 40 ° C. Following this, the internal temperature was raised to 60 ° C with a water bath.
After stirring for 30 minutes, diethylene glycol n
-Butyl ether (100.0 g) was added, and the degree of vacuum was 300
Ethanol and water were removed at an internal temperature of 60 ° C. under a reduced pressure of torr. In the final stage of this removal, the degree of vacuum is 45 torr
And the internal temperature rose to 65 ° C.

Thereafter, the heating source was changed to an oil bath, and heating was performed at 150 ° C. under atmospheric pressure, and the inside of the flask was refluxed at an internal temperature of 128 ° C. The reaction was performed for 120 minutes while separating water from the reflux liquid, and then the flask was cooled to prepare 234 g of a coating composition.

The obtained coating composition (hereinafter referred to as composition 4) is a colorless and transparent high-viscosity liquid, and its viscosity was measured at 1,200 centipoise (1.2 Pa. s). As a result of thermogravimetric analysis, weight loss occurred at 300 to 350 ° C., and finally 53.6% of solid content remained. The viscosity of Composition 4 did not increase even after storage for one month in a room (25 to 30 ° C.), and was stable.

(Example 5) Stirrer, reflux condenser, for reducing pressure
1-liter decompressible 4-neck flask equipped with exhaust port and thermometer
122.4 g of methyltrimethoxysilane (0.9 mol
Le), C₈F₁₇C_TwoH _Four(OC_TwoH_Five)_ThreeFloor indicated by
66.7 g (0.1 mol) of alkylsilane and ethanol 1
00.0 g and 20% solids with stirring
Of silica sol was dropped over 30 minutes. this
Meanwhile, the inside of the flask was heated from 20 ° C. to 40 ° C. drop
The system was opaque at the time of completion, but water continued
The internal temperature was raised to 60 ° C in a bath and stirred for 60 minutes.
A translucent solution was obtained. Then, diethylene glycol
9-g of n-butyl ether was added, and the
Ethanol and water at an internal temperature of 60 ° C under a reduced pressure of 0 torr
Was removed. At the final stage of this removal, the degree of vacuum is 55 torr.
r and the internal temperature rose to 67 ° C.

Thereafter, the heating source was changed to an oil bath, and heating was performed at 150 ° C. under atmospheric pressure, and the inside of the flask was refluxed at an internal temperature of 128 ° C. The reaction was performed for 210 minutes while separating water from the reflux liquid, and then the flask was cooled to prepare 226 g of a coating composition.

The obtained coating composition (hereinafter referred to as composition 5) is a colorless and transparent high-viscosity liquid, and the viscosity was 1000 centipoise (1.0 Pa. s). As a result of thermogravimetric analysis, weight loss occurred at 300 to 350 ° C., and finally 53.6% of solid content remained. The viscosity of Composition 5 did not increase even after storage for one month in a room (25 to 30 ° C.), and was stable.

To 50 g of Composition 5, 30 g of alumina fine powder (particle size: 0.5 μm) and 4.0 g of aluminum borate whiskers were added and kneaded with a three-roll mill to produce a printing paste. The paste obtained here is 10 s ^-1
It showed a viscosity of 120 Pa · s at a shear rate and had good leveling properties. Then, this paste was printed on an aluminum plate by screen printing, dried at 150 ° C., screen printed again, and cured at 300 ° C. to obtain a smooth coating film having a thickness of 30 μm.

An epoxy-based silver paste was printed on the coating film obtained here, cured at 150 ° C., and tested for insulation and moisture resistance of the coating film. This test result was initially 3.
A volume resistivity value of 3 × 10 ¹² Ω · cm and a withstand voltage of 910 V were obtained. After this coating film was stored in an environment of 60 ° C. and 95% RH for 500 hours, the same measurement was immediately carried out. As a result, the volume resistivity increased to 1.19 × 10 ¹⁴ Ω · cm, and the dielectric strength was 460 V Has dropped. The withstand voltage returned to the initial value by the subsequent drying.

(Comparative Example 1) For comparison, in Example 1, the conventional composition taken out at the stage when the hydrolysis reaction was completed had a viscosity of only several centipoise and could not be used as a coating material. . What proceeded the reaction under reflux of ethanol in order to increase the viscosity of this solution was gelled by standing overnight.

Comparative Example 2 For comparison, in Example 2, diethylene glycol n-butyl ether 90.
0 g was added and ethanol and water were simply removed at an internal temperature of 60 ° C. under a reduced pressure of 300 torr, showing extremely good storage stability. It was at the same level as the coating composition, and was insufficient as a coating material.

From the above Examples 1 to 5 and Comparative Examples 1 and 2, the method for producing a coating composition shown in each Example of the present invention was the first to have high viscosity and excellent long-term storage stability. The result is a coating composition.

In each of the examples of the present invention, a silica-based coating composition was described. However, as described in the first embodiment of the present invention, the method for producing the coating composition of the present invention is, for example, zirconia. By using the alkoxide of (1), the water repellency can be increased, and it can be applied to the production of an inorganic coating composition using various metal alkoxides and metal oxide sols.

In the first embodiment of the present invention, a high-boiling solvent is added after the hydrolysis step. However, the high-boiling solvent is used together with the low-boiling solvent from the first stage. It is a good thing. However, in this case, it is necessary to consider the composition and the like so as not to make the reaction system non-uniform.

[0054]

As described above, the method for producing the coating composition of the present invention is characterized in that a solvent having a low boiling point is used as a reaction solvent, and an evaporable catalyst, water and a metal alkoxide are added to the reaction solvent to hydrolyze the metal alkoxide. A step of performing decomposition, a step of adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, an evaporable catalyst and excess water from the reaction system, and further performing a condensation polymerization reaction of the reaction system by heating. According to this production method, a low-boiling solvent is used as a reaction solvent, and an evaporable catalyst, water and a metal alkoxide are added to the reaction solvent to hydrolyze the metal alkoxide, Then, a high-boiling solvent is added to the reaction system to remove the low-boiling solvent, the evaporable catalyst and excess water from the reaction system, and the polycondensation reaction of the reaction system is further advanced by heating. Therefore, the polycondensation reaction of the reaction system,
Since high viscosity suitable for general printing means and coating methods can be maintained, and gelation of the coating composition during long-term storage due to insufficient removal of water does not occur, Since the product has excellent long-term storage stability and does not contain corrosive substances, the resulting coating film has excellent heat resistance and provides a coating composition with high electrical insulation and high surface hardness. It has the effect that it can be done.

Claims (2)

[Claims] 1. A step of using a low-boiling solvent as a reaction solvent, adding an evaporable catalyst, water and a metal alkoxide to the reaction solvent to hydrolyze the metal alkoxide, and adding a high-boiling solvent to the reaction system. Removing the low-boiling solvent, evaporative catalyst and excess water from the reaction system, and further comprising heating to promote the condensation polymerization of the reaction system, producing a coating composition. Method. 2. A low boiling solvent is used as a reaction solvent. An evaporable catalyst, a metal oxide sol dispersed in water or a metal oxide sol dispersed in an organic solvent, water and a metal alkoxide are used as a reaction solvent in the reaction solvent. Adding and hydrolyzing the metal alkoxide; adding a high-boiling solvent to the reaction system to remove the low-boiling solvent, evaporative catalyst and excess water from the reaction system; A method of producing a coating composition, comprising a step of promoting polymerization.