JPS6114185B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to film-forming compositions. More specifically, the present invention relates to a film-forming composition containing an aqueous alkali metal silicate solution or an aqueous colloidal silica dispersion, enamel frit, and zinc dust as essential components. Generally, paints that can withstand high temperatures of 400℃ or higher are considered inorganic paints, but even this inorganic paint
At around 800℃, the difference in thermal expansion from the iron base becomes large, causing peeling when moving from a high temperature range to room temperature. In this way, there is no paint that excels in the high temperature range of 800℃ or higher. In order to develop a paint that can withstand high temperatures of 800°C or higher, the inventor focused on enamel, which has excellent adhesion to iron, and silicates and colloidal silica, which are used as inorganic binders for inorganic paints, and conducted extensive research. As a result, we were able to obtain this film-forming composition that can withstand temperatures of 800°C or higher. Traditionally, enamel finishing is achieved by adding clay, potassium chloride, sodium nitrite, water, etc. as mill additives to the enamel frit and dispersing it, then painting it on the object to be coated and baking it at around 800℃. An enamel film is obtained. However, although it forms a film at temperatures below 800°C before baking, the hardness of the film is extremely low, it has no adhesion to the substrate, no water resistance, and has no function as a paint film. Therefore, it cannot be used unless it is processed at around 800°C. Enamel has the above-mentioned drawbacks in the temperature range below 800℃, but by using it together with an inorganic binder for inorganic paints, enamel can be heated to temperatures below 800℃.
The present inventors have discovered that not only can an inorganic paint that withstands the above-mentioned high temperatures be obtained, but also that a paint that forms a hard coating film with excellent adhesion even at room temperature and has a cosmetic effect can be obtained. That is, the present invention provides (A) general formula M ₂ O・XSiO ₂
(In the formula, M is an alkali metal, N(CH ₂ OH) ₄ , N
(C ₂ H ₄ OH) ₄ , N(C ₂ H ₄ OH) ₃ , C(NH ₂ ) ₂ NH, N
(CH ₃ ) ₃ C ₆ H ₅ or NH ₄ , X is a positive number from 2.0 to 9.0) and/or colloidal silica aqueous dispersion, (B) enamel frit and (C) The present invention relates to a film-forming composition containing zinc powder as an essential component and, if necessary, adding one or more selected from inorganic pigments, enamel frit raw materials, and inorganic additives. In the present invention, the silicate M _{2 O.} Examples include guanidine silicate, which is made of grade ammonium and silicic acid. Alkali metal silicates include sodium silicate, potassium silicate, lithium silicate, cesium silicate, etc. Tertiary amine silicates include triethanolamine silicate, and quaternary ammonium silicates include tetraethanolammonium silicate. can give. As a colloidal silica aqueous dispersion, acidic side,
It can be used even if it is on the basic side. That is, as the colloidal silica on the acidic side, non-stabilized silica (PH 2 to 4) commercially available under the trade name Snowtex-O or Snowtex OL (manufactured by Nissan Chemical Industries, Ltd.) can be used. On the other hand, colloidal silica on the basic side includes silica (PH8.4-10) stabilized by the addition of trace amounts of alkali metal ions, ammonium ions, or amines;
Snowtex 30, Snowtex C, Snowtex N (all manufactured by Nissan Chemical Industries, Ltd.) Ludox HS
-40 (manufactured by DuPont, USA), etc. The enamel frit (B) used in combination with the above inorganic binder (A) is used for ordinary enamel finishing, and contains refractory raw materials (silica stone, silica sand, feldspar, etc.), meltable raw materials (borospar, etc.). sand, boric acid,
Boron oxide, soda ash, chile saltpeter, potash saltpetre, lithium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, calcium hydroxide, lead tan, lead monoxide, zinc white, etc.), weakly opalescent raw materials (fluorspar, ice) crystal, sodium fluoride, aluminum fluoride, sodium silicate, etc.),
Highly opalescent raw materials (tin oxide, antimony oxide, antimony metal, sodium antimonate, titanium oxide, zirconium oxide, zirconium silicate, arsenite, cerium oxide, etc.), coloring raw materials (sulfur flower, chromium oxide, cobalt oxide, nickel oxide) ,
This frit is made from a material selected from manganese dioxide, copper oxide, iron oxide, potassium dichromate, cadmium sulfate, metallic selenium, lead chromate, etc.) and adhesives (cobalt oxide, nickel oxide, manganese oxide, etc.). For example, as a commercially available product, frit number F-
327, F-501, F-540, F-718, (manufactured by Kanto Enamel Glaze Co., Ltd.), etc. Zinc dust improves the water resistance of the coating,
The effect is particularly remarkable when an alkali silicate is used as a binder. In addition to the above-mentioned components, the film-forming composition of the present invention may include inorganic pigments, raw materials for enamel fritting, and
Inorganic additives and the like are added. As inorganic pigments, for example, titanium white, red iron, alumina, red lead, yellow lead, carbon black, cyanine blue, zinc white, etc. can be used as coloring agents, and as extender pigments, talc, tancal, clay, mica, baryta, feldspar can be used. etc. can be used. Further, red lead, basic zinc chromate, cyanamide, etc. can also be used for the purpose of rust prevention. In the present invention, it is possible to enamel the entire coating film in a temperature range of 800°C or higher even with a coating composition consisting only of an inorganic binder and enamel frit; If it is, it is difficult to form an enamel film over the entire surface. Therefore, if it is necessary to enamelize the entire surface of the coating, the above-mentioned raw materials for enamel frit may be used in combination. In addition, common oxide glass raw materials such as thallium, thallium oxide, bismuth oxide, cadmium oxide, indium oxide, phosphorus pentoxide, vanadium pentoxide, germanium oxide, gallium oxide, thorium oxide, and yttrium oxide are used as raw materials for enamel frits. May be added to. In addition, as inorganic additives, clay, bentonite, Erosyl,
It is recommended to use . Additionally, asbestos, glass fiber, glass powder, and glass flakes can be used in combination to prevent cracking of the paint film. The blending ratio of the colloidal silica aqueous dispersion or alkali silicate aqueous solution (A) to the enamel frit (B) and zinc dust (C) is based on the total dry coating weight as 100. The solid content should preferably be 5 to 50% by weight.
Preferably it is 15 to 35% by weight. If it is less than 5% by weight, film formation is poor and hardness is low. Moreover, if it exceeds 50%, cracking tends to occur and water resistance is poor. The proportion of enamel frit can range from 20 to 90% by weight, but preferably from 0 to 85% by weight. If it is less than 20% by weight, it will be difficult to form an enamel film at high temperatures, and if it is more than 90% by weight, it will not have hardness. In addition, the proportion of zinc powder can be included from 0.1 to 40% by weight,
When using a colloidal silica aqueous dispersion, 1 to
It is preferably 10% by weight, and in the case of an aqueous alkali silicate solution, 10 to 40% by weight. When alkali silicate is used in the present invention, it has a glass component that itself becomes Na ₂ O and K ₂ O, so it can be vitrified more easily than colloidal silica. Even if it is contained in a somewhat large amount, it tends to change into an enamel film. The film-forming composition of the present invention is applied to an iron substrate or the like by brushing, spraying, or the like, and forms a film by drying at room temperature. The coating film has excellent adhesion, is hard, and can withstand not only room temperature but also high temperatures of over 800℃. Such characteristics are not found in ordinary inorganic paints such as zinc-rich paints based on alkyl silicate. The reason why such an excellent coating film can be obtained is that not only the enamel frit but also the raw materials used for the enamel frit form an enamel film at high temperatures, and at the same time, the coefficient of thermal expansion of the coating film is close to that of the base material. This is because. In addition, when this inorganic paint composition is used after being dried at room temperature, the paint film does not become glossy.
Epoxy resin paint, polyurethane paint, etc. may be applied as a top coat. 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. Examples 1 to 6 and Comparative Examples 1 to 4 Paints were prepared using the formulations shown in Table 1. The zinc powder was removed, and after being dispersed in a ball mill for 24 hours, the zinc powder was added to create a paint. The resulting paint was applied to a sandblasted steel plate using a brush. The test results are shown in Table-2. *1 LuDox: Manufactured by DuPont, 40% non-volatile content colloidal silica aqueous dispersion *2 Sodium silicate: 40% aqueous solution of Na ₂ O, 3SiO ₂ *3 Enamel frit, F-540, F-327: Manufactured by Kanto Enamel Glaze Co., Ltd.

【table】

【table】

[Table] Test items Hardness: Measure the pencil hardness after drying at room temperature for one week. Paint film condition: There are cracks etc. in the above paint film. Adhesiveness: Peeling was determined by cross-cutting a sample under similar conditions with a knife and performing a tape test. Water resistance: Dry at room temperature for 5 days, immerse in 20℃ water for 5 days, then remove and return to room temperature.
I left it for 30 minutes and observed the softening of the paint film. Heat resistance: After placing the sample in an electric furnace at 400°C and 850°C for 5 hours, it was taken out to room temperature and peeling of the coating was observed 30 minutes later.

Claims (1)

[Claims] 1 (A) General formula M ₂ O.xSiO ₂ (where M is an alkali metal, N(CH ₂ OH) ₄ , N(C ₂ H ₄ OH) ₄ , N
( _C2H4OH ) ₃ ,C( _NH2 ) _2NH ,N( _CH3 ) _3C6H6 or _NH4 , x is _a positive number from 2.0 _{to 9.0} )
A silicate aqueous solution or colloidal silica aqueous dispersion represented by (B) enamel frit and (C) zinc powder are essential ingredients, and if necessary, one or more selected from inorganic pigments, raw materials for enamel frit, and inorganic additives. A film-forming composition comprising: