JPH0410914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film-forming composition, and more particularly to a film-forming composition having excellent heat resistance and containing an alkyl (or allyl) silicate and lead oxide as main components. Generally, the heat resistance of paints that use organic resin as a binder component decreases significantly at temperatures above 400°C, so inorganic paints have traditionally been used for applications that require higher heat resistance. There is. However, since the film formed with conventional inorganic paints is porous, when the material to be coated is a metal surface, for example, an iron base, the base surface is easily oxidized and the film may peel off. It is also believed that this peeling phenomenon is partly due to the fact that the coefficient of thermal expansion of the coating is smaller than that of iron. Therefore, the present inventor previously proposed a heat-resistant coating composition that has excellent adhesion to metal materials and does not peel off even at high temperatures of about 400°C or higher (for example,
JP-A-53-140332, JP-A-53-117027, JP-A-53-121824, etc.). These prior art techniques actively vitrify the formed film at high temperatures to form a film that does not deteriorate and maintains its cosmetic effect even at temperatures of approximately 800° C. or higher. The above-mentioned coating composition exhibits excellent coating film performance when applied to metal materials, especially iron materials, but when the coating material is ceramic or the like, the coefficient of thermal expansion is smaller than that of metal materials. When applied to inorganic materials, since the coating composition uses enamel frit as an essential component, the coefficient of thermal expansion of the coating is close to that of metals, especially iron materials, so the coating may crack or peel. There was a drawback of doing so. In order to avoid this drawback, it is necessary to prepare a coating composition that forms a film with a coefficient of thermal expansion suitable for the object to be coated, which limits the use of enamel frits and requires considerable preliminary consideration in the formulation of the coating material. There was a problem that required . Furthermore, there is a problem in that the use of enamel frit is expensive. Therefore, the present inventors discovered that the film has the ability to form a film at room temperature, can be melted and vitrified at high temperatures of approximately 400°C or higher, and that the coefficient of thermal expansion of the film is similar to that of ceramic materials. As a result of repeated research on the possibility of obtaining a coating composition capable of forming a similar film without the use of enamel frit, it was found that alkyl (or allyl) silicate was used as a binder component, and a specific amount of lead oxide was added to this as a binder component. The present invention was completed by discovering that a composition in addition to the above-mentioned composition satisfies the above-mentioned performance. Thus, according to the invention, (A) alkyl (or allyl) silicate 3-
70% by weight and (B) lead oxide (PbO) and/or red lead (Pb ₃ O ₄ )30
There is provided a film-forming composition characterized in that it contains as an essential component a mixture consisting of ~97% by weight. The film-forming composition of the present invention has excellent thick coating properties and can be easily coated by means such as brush coating, spray coating, and bar coater coating, and the formed film dries at room temperature. The film has excellent adhesion even at room temperature and does not peel off easily. Furthermore, in a temperature range of 600°C or higher, the film changes to a glassy state and forms an insulator. For example, when coated on a ceramic substrate, a glassy insulating film is formed thereon. To explain in more detail the process of vitrifying the film described above, the film-forming composition of the present invention is first heated at 300 to 450°C.
Below, a film consisting of alkyl silicate and lead oxide is formed, and at higher temperatures, for example, at about 600°C or higher, the film in the alkyl silicate compound is formed.
It is thought that the SiO ₂ component and lead oxide melt and change into silicate-lead glass. The alkyl (or allyl) silicate A used in the present invention has the following general formula: (R represents an alkyl group or an allyl group having 1 to 8 carbon atoms, and n represents an integer of 0 or 11 or less) or a lower condensate thereof. . Specifically, for example, methyl orthosilicate, ethyl orthosilicate, n-propylorthosilicate, n-butyl orthosilicate, n-octylorthosilicate, phenyl orthosilicate, benzyl orthosilicate, phenethyl orthosilicate, allyl ( Examples include allyl) orthosilicate, methacryl orthosilicate, and low condensates produced by dehydration condensation of these orthosilicates. Furthermore, as the alkyl (or allyl) silicate A that can be suitably used in the present invention, the above-mentioned tetraalkyl (or tetraallyl) orthosilicate and the following general formula (R and n represent the above-mentioned meanings, R' represents an alkyl group having 1 to 12 carbon atoms or allyl) (for example, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane silane, phenyltriethoxysilane, their low condensates, etc.) in the presence of an acid catalyst, and then condensed using an alkaline substance to raise the pH to 7 or more. Examples include organosilicon high condensates having a degree of condensation of 20 or more and a molecular weight of about 3000 or more. This high condensate may be used alone or in combination with the alkyl silicate of the general formula []. In this high condensate, it is appropriate that the components of the general formula [] and [] be blended in the following proportions based on weight. Compound of general formula []: 5 to 95% by weight, preferably 20 to 80% by weight Compound of general formula []: 5 to 95% by weight, preferably 20 to 80% by weight In the above formulation, the amount of compound [] is less than 5% by weight i.e. 95% by weight of [] compound
If it exceeds , the curability of the inorganic coating formed using this condensate at room temperature will be poor. In addition, if the amount of the [] compound is less than 5% by weight,
That is, when the amount of the [] compound exceeds 95% by weight, the film tends to peel off when thick coating is applied using this condensate. In the present invention, when the organosilicon high condensate is used as component A, the resulting film-forming composition can be applied thickly (up to a dry film thickness of about 100μ) and is easily cured by components in the air. However, the film formed has excellent heat resistance. In the present invention, lead oxide (PbO) is used as the B component.
and red lead (Pb ₃ O ₄ ) are used, among which red lead is preferred because it has excellent storage stability when used as a paint composition and has excellent appearance when a film is formed. The blending ratio of alkyl (or allyl) silicate A and lead oxide and/or red lead B, which are essential components in the film-forming composition of the present invention, is (A): 3 to 70% by weight, preferably 5 to 50% by weight (B): Suitably blended in a range of 30 to 97% by weight, preferably 50 to 95% by weight. In the above formulation, if component (A) exceeds 70% by weight, that is, component (B) is less than 30% by weight, cracks may occur in the film or the vitrification temperature will become high, resulting in the formation of a continuous glassy film. It's difficult. On the other hand, 3%
If the amount of component (B) exceeds 97% by weight, the coating will peel off easily when dried at room temperature.
It is difficult to form a film. In the present invention, in addition to the above-described components (A) and (B), inorganic pigments, raw materials for glass, inorganic additives, etc. may be blended as necessary. Examples of inorganic pigments include titanium white, red iron, alumina, carbon black, and coloring agents.
Cyanine blue, zinc white, etc. can be used, and as extender pigments, talc, tankal, clay, mica, baryta, feldspar, etc. can be used. In addition, raw materials for glass include refractory raw materials (silica stone, silica sand, feldspar, etc.), meltable raw materials (soda ash, chile saltpetre, potassium saltpeter, lithium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, water calcium oxide, zinc oxide, etc.),
Weak milk white raw materials (fluorite, cryolite, sodium fluoride, aluminum fluoride, sodium silicate, etc.), strong milk white raw materials (tin oxide, antimony oxide,
antimony metal, sodium antimonate, titanium oxide, zirconium oxide, zirconium silicate, arsenite, cerium oxide, etc.), coloring materials (sulfur flower, cobalt oxide, chromium oxide, nickel oxide, manganese dioxide, copper oxide, iron oxide, Potassium dichromate, cadmium sulfate, metallic selenium, lead chromate, etc.) and adhesives (cobalt oxide, nickel oxide, manganese dioxide, etc.) can be used. Further, as the inorganic additive, mica, clay, bentonite, Erosil, etc. may be used in order to suppress sedimentation of the pigment. Furthermore, asbestos, glass fiber, glass powder, and glass flakes can also be used in combination to prevent cracking of the paint film. The total amount of the above-mentioned inorganic pigments, raw materials for glass, inorganic additives, etc. can be contained up to 50% by weight as a solid content in the film-forming composition, but preferably 20% by weight or less. It is. The film-forming composition of the present invention is applied to materials such as glass plates, ceramics, and metals by means such as brush coating and spray coating. These include oxide ceramic materials such as alumina, magnesia, zirconia, titania, and barium titanate, and non-oxide ceramic materials such as nitrides, carbides, and borides. The film formed by the film-forming composition of the present invention dries at room temperature, has excellent adhesion, is hard,
Can withstand high temperatures of over 800℃. Such characteristics are not found in ordinary inorganic paints. The reason why such an excellent film can be obtained is that the components in the composition form a glassy film at high temperatures, and the coefficient of thermal expansion of the film is close to that of the material to be coated. Because there is. The present invention will be explained in more detail below using Examples and Comparative Examples. Note that parts and % indicate parts by weight and % by weight unless otherwise specified. Example 1 Paint compositions were prepared by dispersing various inorganic paint compositions having the following compositions using a paint conditioner for about 2 hours. Ethyl silicate 66% hydrolyzed solution *1 50 parts Red lead 70 parts *1 Ethyl silicate (manufactured by Nippon Colcoat Chemical Co., Ltd.,
A mixture consisting of 100 parts of SiO ₂ min (40%), 90 parts of isopropyl alcohol and 10 parts of IN-hydrochloric acid with a degree of polymerization of 4 to 6 was maintained at room temperature for 24 hours for hydrolysis. The hydrolysis rate of the obtained ethyl silicate was 66%, and the nonvolatile content was 20%. Example 2 A coating composition was prepared in the same manner as in Example 1 with the following formulation. 50% hydrolyzed solution of ethyl silicate *225 parts Fluorite 2 parts Silica powder 10 parts Red lead 70 parts *2 Ethyl orthosilicate (manufactured by Nippon Colcoat Chemical Co., Ltd., SiO ₂ min 28%) 248 parts, isopropyl alcohol 250 parts and IN - A mixture consisting of 18 parts of hydrochloric acid was maintained at room temperature for 24 hours for hydrolysis. The hydrolysis rate of the obtained ethyl orthosilicate was 50%, and the nonvolatile content was 16%. Example 3 A coating composition was prepared in the same manner as in Example 1 with the following formulation. Organosilicon high condensate solution *3 40 parts Potassium nitrate 2 parts Red lead 100 parts Long stone 10 parts *3 Add 62 g of tetraethoxysilane, 125 g of methyltriethoxysilane, and 187 g of ethyl alcohol to a reaction vessel, and stir the contents. heat it up
After the temperature reached 80℃, add 30g of 0.2N hydrochloric acid and heat to 80℃.
The mixture was allowed to react for 10 hours. Next, 30 g of triethylamine was added to this reaction product to raise the pH to 7 or above, and a condensation reaction was carried out at 80° C. for 2 hours. After that, benzene was added and the solvent was removed until the nonvolatile content became 36%. Example 4 A coating composition was prepared in the same manner as in Example 1 with the following formulation. Organosilicon high condensate solution *4 40 parts Nagarite 10 parts Red lead 70 parts *4 Add 132 g of tetrabutoxysilane, 138 g of phenyltributoxysilane, and 270 g of butyl alcohol to a reaction vessel, and heat the contents while stirring. After the temperature reached 100°C, 66 g of 5% formic acid aqueous solution was added and the mixture was reacted at 100°C for 1 hour. Then, 30 g of N-methylmorpholine was added to this reaction product.
Raise the pH to 7 or higher and conduct the condensation reaction at 90℃ for 2 hours, then add 100g of toluene to reduce the nonvolatile content to 40%.
%. Comparative Example 1 A coating composition was prepared in the same manner as in Example 1 using the following formulation. Ethyl silicate used in Example 1 10 parts Titanium white 20 parts Alumina 10 parts Comparative example 2 Heat-resistant paint "Terumo 300" (manufactured by Kansai Paint Co., Ltd.)
was subjected to the test. The paints obtained in the above Examples and Comparative Examples were applied with a brush onto an oxide-based ceramic plate, dried at room temperature, and then used for testing. The test results are shown in Table 1 below. [Test Items] Hardness: After drying the coating film at room temperature for one week, pencil hardness was measured. Adhesion: After the coating was allowed to dry at room temperature for 5 days, a cross cut was made with a knife and then peeled off with cellophane tape to see if it would adhere to it. Heat resistance: After being placed in an electric furnace at 400°C and 800°C for 1 hour, it was left at room temperature and the coating film was observed for cracking or peeling. ◎: Indicates that there is no cracking or peeling 〇: Indicates that there is very little cracking, but there is no problem in practical use [Table]

Claims (1)

[Scope of Claims] 1 (A) 3 to 70% by weight of alkyl (or allyl) silicate and (B) lead oxide (PbO) and/or red lead (Pb ₃ O ₄ ) 30
A film-forming composition comprising as an essential component a mixture consisting of ~97% by weight.