JPH0371472B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a coating composition, and more particularly to a coating composition that can be applied to the surface of iron, stainless steel, aluminum and other metals as well as cement, glass, plastic and other products by short-term low-temperature heating. This creates a pure inorganic film with excellent heat resistance, durability, water resistance, and chemical resistance, and is a coating composition for use in high-temperature oxidation prevention, infrared radiation, heat insulation, electrical resistance, conductivity, corrosion protection, etc. relating to things. [Prior Art] Conventionally, pure inorganic coating compositions include alkali metal salt-based coating agents, acidic metal salt-based coating agents, or Si
Metal alkoxide coating agents such as (OR ¹ ) ₄ (where R ¹ represents a hydrocarbon residue having 1 to 5 carbon atoms) have been proposed. [Problems to be solved by the invention] However, among the coating agents,
Alkali metal salt-based coating agents have limited water resistance and acid resistance because they contain alkali, and cannot be used for electrical resistance purposes. In addition, the acidic metal salt-based coating agent has the disadvantage that it has poor acid resistance because it contains acid, and that both of them are air permeable. Furthermore, metal alkoxide coating agents must contain water necessary for hydrolysis, resulting in a short pot life, which poses a very difficult problem when used as a coating agent. The present invention was made in view of the above-mentioned technical problems, and its first objective is to provide good coating properties to base materials made of metal, plastic, wood, paper, cement, and various other materials. in,
To provide a coating composition that can significantly improve surface properties such as water resistance, weather resistance, corrosion resistance, and heat resistance of a base material, and can be cured in a short time by heating at low temperatures. A second object of the present invention is to create films with high emissivity in the far-infrared region, films with high emissivity in the near-infrared region, conductive films, and electrically resistive films by blending various fillers. Another object of the present invention is to provide a coating composition for producing a functional inorganic paint capable of forming a heat insulating film, a molten metal release film, a transparent cured film, etc. [Means for Solving the Problems] That is, the present invention provides (a) a compound represented by the general formula Si(OR) ₄ (wherein, R represents a hydrocarbon residue having 1 to 5 carbon atoms); At least one silane compound selected from the group of tetraalkoxysilane, a hydrolyzate of the tetraalkoxysilane, and a partial polycondensate of the hydrolyzate (hereinafter sometimes simply referred to as a "silane compound") 5 to 60 Parts by weight, (b) Zirconium tetraalkoxide represented by the general formula Zr(OR') ₄ (in the formula, R' represents a hydrocarbon residue having 1 to 5 carbon atoms), hydrolysis of the zirconium tetraalkoxide At least one selected from the group of polycondensates and partial polycondensates of the hydrolysates.
3 to 30 parts by weight of a seed zirconium compound (hereinafter sometimes simply referred to as "zirconium compound"), (c) 1 to 90 parts by weight of an organic solvent, and (d) 1 to 60 parts by weight of a filler. )+(b)+(c)+(d)=100 parts by weight). The present invention is a tetraalkoxysilane; Si(OR) ₄ that undergoes hydrolysis gradually due to moisture in the atmosphere.
and Zr(OR′) ₄ , a zirconium tetraalkoxide whose hydrolysis proceeds rapidly due to moisture in the atmosphere.
This was based on the knowledge that a functional inorganic coating film can be formed by mixing a mixture of the following, adjusting the amount of an organic solvent for concentration adjustment, and then adding a filler. . Hereinafter, the present invention will be explained in detail for each component. (a) Silane compound Tetraalkoxysilane used in the present invention; Si(OR) ₄ is hydrolyzed in the presence of water to form a hydrolyzate (tetrasilanol), and the hydrolyzate is polycondensed to partially polymerize. producing a condensate;
When the molecular weight is further increased to form a coating film, it is cured by heating, and in the composition of the present invention, it functions as a binder together with (b) the zirconium compound. R in such tetraalkoxysilane is, for example, an alkyl group having 1 to 5 carbon atoms, such as a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group,
Such as tert-butyl group. Specific examples of these tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, and tetra-
Examples include n-butoxysilane, tetra-sec-butoxysilane, and tetra-tert-butoxysilane. These tetraalkoxysilanes can be used alone or in combination of two or more. Furthermore, among these tetraalkoxysilanes, tetraethoxysilane is particularly preferred. In addition, such tetraalkoxysilane partially liberates alcohol by hydrolysis,
The polycondensation of the hydroxyl substituent takes place in an aqueous medium with the formation of silanol, giving rise to the corresponding hydrolyzate (tetrasilanol),
A partial polycondensate of silanol is produced, which is further polycondensed to produce a silica component which is a complete polycondensate. Therefore, the silane compound (a) in the present invention includes, in addition to the above-mentioned tetraalkoxysilane, a hydrolyzate thereof and a partial polycondensate of the hydrolyzate. Such hydrolyzate and/or partial polycondensate may be produced from tetraalkoxysilane in the composition, or the hydrolyzate and/or partial polycondensate, for example, ethyl silicate 40 (manufactured by Colcoat Co., Ltd.) may also be blended. The proportion of the silane compound (a) in the composition is 5 to 60 parts by weight, preferably 30 to 40 parts by weight, and at the end of 5 parts by weight, although the storage stability of the composition itself is good, it is not suitable for coating. If the amount exceeds 60 parts by weight, the proportion of the zirconium compound becomes relatively small and hydrolysis does not proceed in a short period of time. Film forming properties will deteriorate. (b) Zirconium compound _The (b) zirconium tetraalkoxide used in the present invention; A substance that is condensed to form a partial polycondensate, which is hardened by heating when the molecular weight is increased to form a coating film, and which acts as a binder together with (a) the silane compound in the composition of the present invention. It is. In such zirconium tetraalkoxide
R' is, for example, an alkyl group having 1 to 5 carbon atoms, such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, tert-butyl group, etc. . Specific examples of these zirconium tetraalkoxides include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetra-i-propoxide, zirconium tetra-n-butoxide, and zirconium tetra-
sec-butoxide, zirconium tetra-
Examples include tert-butoxide. These zirconium tetraalkoxides can be used alone or in combination of two or more. Among these zirconium tetraalkoxides, zirconium tetra-n-butoxide is particularly preferred. In addition, such zirconium tetraalkoxide is rapidly hydrolyzed to liberate the alcohol and produce the corresponding zirconium tetrahydroxide, and the production of the hydroxide causes polycondensation of the hydroxyl substituent, and the hydroxyl A partial polycondensate of polycondensate is produced, which is further polycondensed to produce a zirconia component which is a complete polycondensate. Therefore, the zirconium compound (b) in the present invention includes not only the zirconium tetraalkoxide but also its hydrolyzate and partial polycondensate of the hydrolyzate. Such hydrolysates and/or partial polycondensates are
It may be generated from zirconium tetraalkoxide in the composition, or it may be blended in advance when preparing the composition. The proportion of such zirconium compound (b) in the composition of the present invention is 3 to 30 parts by weight, preferably 8 to 30 parts by weight.
16 parts by weight, and less than 3 parts by weight relatively (b)
Because the proportion of zirconium compounds is small and hydrolysis does not proceed in a short period of time, film forming properties are poor;
If it exceeds 1 part by weight, the proportion of the zirconium compound (b) will be too high, resulting in poor storage stability of the resulting composition, and hydrolysis will be too rapid, resulting in poor film-forming properties, both of which are undesirable. (c) Organic solvent The organic solvent is a dispersion medium for the filler (d), which is a fine particle, as described later, and is also a concentration adjusting agent for the silane compound (a) and the zirconium compound (b), and furthermore, , (b) is for adjusting the hydrolysis of component. Such organic solvents include, for example, alcohols, glycol derivatives, or those having a boiling point of 120°C.
The following low boiling point organic solvents are suitable. Among these, the alcohols or glycol derivatives include monohydric alcohols or dihydric alcohols.
Ethylene glycol or its derivatives, which are alcohols, can be mentioned, and among these, 1
The alcohol is preferably an aliphatic alcohol having 1 to 8 carbon atoms, specifically methanol,
Ethanol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol,
sec-butyl alcohol, tert-butyl alcohol, n-pentyl alcohol, n-hexyl alcohol, 4-methyl-2-pentanol,
Examples include 4-methyl-n-pentanol, and examples of ethylene glycol or its derivatives include ethylene glycol, ethylene glycol monobutyl ether, and acetic acid ethylene glycol monoethyl ether. These alcohols and glycol derivatives are preferably i-propyl alcohol, sec-butyl alcohol, n-propyl alcohol, n-butyl alcohol, acetic acid ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. Examples of low-boiling organic solvents having a boiling point of 120° C. or lower include toluene, benzene, acetone, methyl ethyl ketone, cyclohexane, and tetrahydrofuran. These organic solvents can be used alone or in combination of two or more. In the present invention and composition, the ratio of (c) organic solvent is 10
~90 parts by weight, preferably 15-35 parts by weight,
If it is less than 10 parts by weight, the viscosity of the composition will increase too much and the storage stability will deteriorate, while if it exceeds 90 parts by weight, the storage stability of the composition itself will improve, but the solid content in the composition will decrease. It is not possible to achieve a thick coating film, and the rate of hydrolysis decreases, resulting in insufficient curing in a short period of time. (d) Filler The filler in the present invention is used to exhibit various functions such as heat resistance, infrared radiation, conductivity, electrical resistance, cosmetics, and heat insulation. Such fillers include, for example, general pigments such as inorganic pigments; metals, alloys, and their oxides, carbides, or nitrides in the form of particles or fibers other than pigments; and also M(OR ² ) _o (M is a metal atom other than silicon or zirconium, R ² is an alkyl group, and n is an integer), and specifically includes nickel, copper, stainless steel, and titanium oxide (TiO ₂ ). ,
Aluminum oxide (Al ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), sillimite (Al ₂ O ₃・SiO ₂ ), synthetic mullite (3Al ₂ O ₃・2SiO ₂ ), mica, potassium titanate, iron oxide ( Fe ₂ O ₃ ), manganese oxide (Mn ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), synthetic pigment of cobalt oxide and alumina (CoO.Al ₂ O ₃ ), zirconia silicate (zircon: ZrO ₂ / SiO ₂ ), copper oxide (CuO), tin oxide,
Examples include antimony oxide,
It is not limited to these. The average particle size of these fillers is 0.01~
The thickness is about 100 μm, preferably about 0.02 to 2 μm. Note that some of these fillers become transparent when their average particle size is reduced to 0.02 μm or less. For example, tin oxide, antimony oxide, aluminum oxide, etc. The proportion of such a filler in the composition is 1 to 60 parts by weight, preferably 10 to 50 parts by weight; if it is less than 1 part by weight, the filler is too small and the function of the resulting coating film is reduced; If it exceeds 1 part by weight, the viscosity of the composition increases, and the proportion of the components (a) and (b), which are binders, decreases, resulting in a weakened adhesion of the resulting coating film to the substrate. Hardness is not improved sufficiently and is not preferable. Among these fillers (d), titanium oxide, aluminum oxide, chromium oxide, sillimite, synthetic mullite, zirconia silicate, iron oxide, manganese oxide, copper oxide, silicon carbide, silicon nitride, etc. A coating film with particularly excellent corrosion resistance can be obtained, but a high purity one is desirable depending on the application. Particularly when the resulting coating film is used for electrical resistance, the contamination of alkali metals is undesirable. In other words, if a material contains an alkali metal, it exhibits conductivity because alkali ions move when voltage is applied, and it does not return to its original state even after the voltage is removed, and further application of voltage causes dielectric breakdown. be. In addition, the above-mentioned fillers such as aluminum oxide and chromium oxide have their own characteristics, so they can also be used for purposes other than corrosion prevention and electrical resistance. For example, (d) when two or more powders such as zirconia silicate, aluminum oxide, titanium oxide, and chromium oxide are added as a filler, the result is a coating film with an emissivity of around 0.9 or more in the far infrared region. Furthermore, (d) a coating film with a high thermal emissivity can be obtained by adding two or more kinds of powders such as iron oxide, cobalt oxide, copper oxide, and chromium oxide as a filler. Furthermore, when silicon carbide is used as a filler, a molten metal release film and an electrically resistive film with good thermal conductivity can be obtained. Conversely, if a metal oxide or metal nitride is used as a filler, a film with good heat insulation properties can be obtained. Furthermore, a color film can be obtained by using yellow titanium oxide or edge-colored chromium oxide as a filler. In addition, the composition of the present invention has (a) to
The optimum amount of (c) organic solvent to be added varies depending on the material of the base material of the coating surface, and mainly depends on the surface area of the coating surface, water absorption rate, etc. Determined based on terms and conditions. Therefore, a preferred embodiment of the composition of the present invention includes (a) tetraethoxysilane as the silane compound, (b) zirconium tetra-n-butoxide as the zirconium compound, and (c) i-
When coating the composition of the present invention using propyl alcohol and (d) mica as a filler on a metal or plastic substrate with a smooth coating surface and a small surface area, the following method may be used: Compositions are preferred. (a) Tetraethoxysilane; 18 to 24 parts by weight (b) Zirconium tetra-n-butoxide; 6 to 8 parts by weight (c) i-propyl alcohol; 58 to 66 parts by weight (d) Mica powder (scaly, Average particle size: 1 to 1.5 μm); 10 to 15 parts by weight The composition of the present invention can also be applied to substrates with large surface areas and rough surfaces such as cement, paper, and wood using the same components (a) to (d). The following compositions are suitable for coating objects. (a) Tetraethoxysilane; 32 to 48 parts by weight (b) Zirconium tetra-n-butoxide; 11 to 16 parts by weight (c) i-propyl alcohol; 26 to 47 parts by weight (d) Mica powder (listed above); 10 ~15 parts by weight The composition of the present invention is formed by mixing the above-mentioned components (a) to (d), and these components particularly include (a) which promotes the hydrolysis of the silane compound and improves the resulting coating film. Small amounts of acid can also be added to accelerate curing. Such acids include inorganic acids such as nitric acid and hydrochloric acid;
Acetic acid, formic acid, propionic acid, maleic acid, chloroacetic acid, citric acid, benzoic acid, dimethylmalonic acid,
Examples include organic acids such as glutaric acid, glycolic acid, malonic acid, toluenesulfonic acid, and oxalic acid. These acids can be used alone or in combination of two or more. The proportion of such acids in the composition is 0.01 to 1% by weight, preferably 0.05 to 0.3% by weight, based on the total composition.
That's about it. In addition, in order to cure under mild conditions, the composition of the present invention may contain alkali metal salts of carboxylic acids, quaternary ammonium carboxylates, metal salts of carboxylic acids, amines, alkali metal salts, alkali hydroxides, etc. curing catalysts can be used. When using these acids and curing catalysts together,
For example, for 100 parts by weight of acetic acid, nitrous acid, sulfite,
At least one alkali metal salt such as aluminic acid
By adding about 0.05 to 0.5% by weight of a liquid mixture consisting of 1 to 20 parts by weight of seeds to the composition of the present invention, the composition of the present invention can be heated at 60°C for 3 to 10 days at room temperature. can be cured (finished) in 1 to 3 hours. Furthermore, when producing the composition of the present invention,
Other conventionally known additives such as organic pigments, various surfactants, silane coupling agents, titanium coupling agents, and dyes may also be added. In addition, although the heat resistance of the film decreases, in order to increase the density, the general formula R ³ Si (OR ⁴ ) ₃ (wherein R ³ is a carbon number of 1 to 8
(R ⁴ is the same as R or R' above)
Organoalkoxysilanes represented by can be added. When preparing the composition of the present invention, for example,
Components (a) to (d) may be mixed at once, or (c) to
(a) to (b) may be added to the mixed solution of (d), and usually the solid content [amount of (a) converted as a silica component + amount of (b) converted as a zirconia component + (d ) Total amount of filler] The concentration is adjusted to 10 to 80% by weight, preferably 15 to 50% by weight. As described above, the coating composition obtained according to the present invention can be applied to the surface of the substrate, which is the target object, by applying the coating composition to the surface of the substrate.
By painting methods such as spraying and date ping,
A coating film with a thickness of about 0.5 to 50 μm can be formed with one coat, and a thickness of 1.5 to 150 μm with 2 to 3 coats.
It is possible to achieve a film thickness of about 100%. When the composition of the present invention is coated on a substrate, the composition absorbs moisture adhering to the substrate or moisture in the atmosphere, instantly or in a short period of time even at low temperatures from room temperature to about 80°C. It is hydrolyzed and becomes a sol due to the polycondensation reaction that occurs simultaneously, and as the reaction progresses further, it becomes a gel. Also, for example 100
When heated at ~300℃ for about 10 to 60 minutes, a small amount of
A glassy film of zirconia silicate (SiZrO ₄ ) with OH groups + filler is formed, and this is further heated to 550 to 650
When heated to ℃, the OH groups disappear and a film of SiZrO ₂ + filler is formed. This reaction is expressed, for example, by the following formula. Filler + Si (OR) ₄ + Zr (OR') ₄ +8H ₂ O → Filler + Si
Zr(OH) ₈ +4ROH+4R'OH Filler + SiZr(OH) ₈ →SiZrO ₄ + Filler + 4H ₂ O After coating the coating composition of the present invention on a base material in this way, it is cured for a long time at room temperature. Immediately, for example, at about 100 to 300℃ for 10~
Since a film can be formed by heating for about 60 minutes, workability can be greatly improved. The film obtained from the composition of the present invention has an electrical resistance value of about 10 ¹² to 10 ¹³ Ω·cm when a filler with an average particle size of 1 μm or less is used, and it can be coated in multiple layers. When the film thickness is 100 μm or more, the electrical resistance value can be set to about 10 ¹⁴ Ω·cm. In addition, since it has excellent weather resistance, water resistance, and chemical resistance, it is effective when used in combination with other inorganic anticorrosion paints. When the composition obtained according to the present invention is used in an outdoor structure such as concrete in a place that cannot be heated, it can be used only by drying at room temperature for 3 to 10 days as described above. In this case, after 5 to 10 hours have passed, there is no problem even if the device gets wet with rain. Recently, there has been a demand for high-purity electrical resistance films for electrical and electronic components, and the filler of the composition of the present invention may include a hydrolyzate of the metal alkoxide represented by M(OR ² ) _o . This requirement can be met if a high purity material is used. In addition, (d) zirconia, alumina, as a filler,
If two or more types of powders such as titanium oxide, cobalt oxide, and chromium oxide are used, a highly efficient far-infrared emitting film can be obtained. A film with high thermal emissivity can be obtained by using two or more kinds of powders such as. The composition of the present invention can be applied to a base material in one or more layers to form a coating film.
Furthermore, another coating composition, such as a composition comprising components (a) to (c) defined in the present invention, may be overcoated as a top coat. [Function] The present invention focuses on the difference in the rate of hydrolysis of Si(OR) ₄ and Zr(OR') ₄ , and when coated on a base material without containing the water necessary for hydrolysis, it can be coated in a short time. It is hydrolyzed by moisture in the air or attached to the substrate, and a film is formed by a polycondensation reaction that occurs simultaneously. That is, Si(OR) ₄ has a very slow hydrolysis rate.
It takes up to 7 days, while Zr(OR') ₄ is hydrolyzed in a few minutes. For this reason, the composition of the present invention does not require any particular acid to promote hydrolysis and has extremely high purity, and by using a highly pure and functional filler, A functionalized coating agent is obtained. [Examples] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In the examples, parts and percentages are based on weight unless otherwise specified. Example 1 Compositions A and B shown in Table 1 were prepared to examine properties such as heat resistance, adhesion, spalling resistance, hardness, and electrical resistance.

〔hardness〕

Based on pencil hardness (JIS K5400). [Adhesion ~] Adhesion: Based on cellophane tape peel test. Adhesion: Based on tensile strength (JIS K5400). Adhesion: Based on a grid test. [Heat resistance ~] Heat resistance; held at 1400℃ x 120 hours in an electric furnace,
After cooling naturally, the condition of the coating film was observed. Heat resistance: held at 1200℃ x 240 hours in an electric furnace,
After cooling naturally, the condition of the coating film was observed. [Spalling resistance] Heating at 600°C and cooling with cold water was repeated 20 times, and the state of the coating film was observed. [Water Resistance] After 60 days of immersion in tap water, the condition of the coating film was observed. [Boiling water resistance] The coating was boiled in tap water for 120 hours and the state of the coating film was observed. [Electrical resistance] Measured in accordance with JIS C1302.

【table】

[Table] Example 2 Composition C shown in Table 3 was prepared to examine its performance as a top coat for curing resin coatings.

[Table] Next, 50
Apply composition C to a steel plate (S45C) of ×50 × 2 mm size using an air spray gun, and immediately
When heated at ℃ for 30 minutes, a glossy film with a thickness of 2 mm was formed. The test results for this test piece are shown in Table 4. In addition, in Table 4, salt water spray resistance refers to 4%
Salt solution was sprayed for 480 hours and the state of the coating film was observed.

【table】

[Table] Example 3 To examine the waterproof properties of concrete, 0.03% of sodium nitrite was added to Composition C in Table 3 as a hardening agent.
% to prepare composition D. Next, Composition C was applied to the entire surface of a concrete block with a size of 100 x 100 x 50 mm using an air spray gun, and the block was left outdoors for 24 hours. It was then reapplied in the same manner and left outdoors for 48 hours. The amount of the two coats was 120 g per square meter. The waterproof test results for this concrete block are as follows:
It was as follows. That is, three concrete blocks were immersed in tap water for 30 days, and the weight change was measured. The water absorption rate was 3% or less in all cases. Also, the results were similar for those immersed for 90 days, and the surface water repellency when visually observed was completely unchanged from before the test. Example 4 Composition E and Composition F shown in Table 5 were prepared as compositions for far-infrared emitting films.

[Table] Next, composition E was applied to one side of a 50 x 50 x 2 mm steel plate (S45C) using an air spray gun so that the film thickness after drying would be 30 μm, and heated at 120°C for 20 minutes. Further, Composition F was applied so as to impregnate it, and heated at 120°C for 30 minutes. Membrane pressure is approximately 30μm
It was hot. The test results for this test case are shown in Table 6. In addition, in Table 6, the spectral emissivity is measured using a thermal emissivity measurement device that is an attached device of the IRA-2 type infrared spectrophotometer manufactured by JASCO Corporation, and the temperature setting value is 100℃ ± 1.0.
The emissivity in the far infrared region with a wavelength of 5 to 25 μm at ℃ was determined.

〔Effect of the invention〕

As described above, since the coating composition of the present invention uses a metal alkoxide, it does not contain an alkali metal and can be made even more pure.It has high purity with excellent heat resistance and corrosion resistance. 1000℃ or higher It has heat resistance and forms a dense film, so it can provide an excellent high-temperature oxidation prevention film.It can provide a concrete waterproofing film with excellent weather resistance and corrosion resistance.Organic coating film, inorganic coating film When used as a top coat of a paint film, it can improve hardness, weather resistance, and corrosion resistance. It has excellent heat resistance, weather resistance, water resistance, seawater resistance, organic solvent resistance, and acid resistance, and can form a paint film. It is possible to obtain a corrosion-resistant film with a wide range of applications and uses. It can be applied to most products as a base material, including metals, glass, ceramics, cement, fibers, paper, and plastics. It can be hardened (so-called low-temperature sintering) and can be hardened even at room temperature by using a hardening agent.Since the film itself is activated, it can be sintered at around 1100℃, which is much higher than the normal sintering temperature of the raw material. It has many advantages, such as being non-flammable and producing no gas even when heated, and being stable for more than a year when kept tightly closed as the pot life does not contain water. The significance is extremely great.

Claims (1)

[Claims] 1 (a) General formula Si(OR) ₄ (wherein R has 1 to 1 carbon atoms)
The hydrocarbon residue of No. 5 is shown. ) 5 to 60 parts by weight of at least one silane compound selected from the group of tetraalkoxysilane represented by the following, a hydrolyzate of the tetraalkoxysilane, and a partial polycondensate of the hydrolyzate, (b) General formula Zr(OR') ₄ (in the formula, R' represents a hydrocarbon residue having 1 to 5 carbon atoms), a hydrolyzate of the zirconium tetraalkoxide, and a portion of the hydrolyzate At least one selected from the group of polycondensates
3 to 30 parts by weight of a seed zirconium compound, (c) 10 to 90 parts by weight of an organic solvent, and (d) 1 to 60 parts by weight of a filler (wherein (a) + (b) + (c) + (d) = 100 parts by weight).