JPH0350585B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a coated plate by applying a cold-curable inorganic paint using a roll coater method. (Prior Art) A large number of compositions have been disclosed for inorganic paints containing an aqueous alkali metal silicate solution as a binder. However, these compositions rarely have a sufficient pot life, satisfactory water resistance, and efflorescence resistance when cured at room temperature, and most require heat curing at 150 to 350°C. The present inventors previously proposed a room-temperature curable inorganic coating composition that has a suitable pot life, high water resistance, efflorescence resistance, surface hardness, and adhesion strength (Japanese Patent Application Laid-Open No. 1983-1972-1).
56364 etc.). However, these compositions had poor tackiness and a high thixotropic index, making them unsuitable for roll coater application. For this reason, spray methods and flow coater methods are generally used to apply inorganic paints; However, the disadvantage was that pinholes were easily formed in the coating film. (Object of the invention) In order to improve the above-mentioned drawbacks, the present invention
An object of the present invention is to provide a method for producing a coated board in which an inorganic paint having sufficient water resistance and efflorescence resistance when cured at room temperature is modified and coated on a substrate using a roll coater method. (Structure of the Invention) The present invention is characterized in that a specific viscosity agent is added to an alkali silicate-based cold-curing inorganic paint, the thixotropic index is adjusted to 4.0 to 8.5, and the paint is applied to various boards using a roll coater method. This relates to a method for manufacturing coated boards. General formula for room temperature curing inorganic paint
An alkali metal silicate aqueous solution represented by M ₂ O・nSiO ₂・mH ₂ O (M is lithium, sodium, potassium; n=2.0 to 4.5) is used as a binder, and the adsorption amount of calcium sulfite and/or iodine is 50 to 250.
A composition containing active magnesium oxide of mg·I/g·MgO as a hardening agent is used. In order to impart roll coatability, it is desirable that the solid content of the sodium salt and/or potassium salt is 50% by weight or more based on the total solid content of the alkali metal silicate. Further, if particularly necessary, other inorganic binders such as silica sol and alumina sol, and organic binders such as synthetic resin emulsions and silicone compounds may be added. In this case, it is preferable that the solid content of these other binders is 40% by weight or less based on the solid content of the alkali metal silicate. Other heat-curing curing agents, such as sodium silicate and condensed aluminum phosphate, do not only fail to provide sufficient water resistance and efflorescence resistance when cured at room temperature, but also do not provide a viscosity suitable for roll coaters. I can't do it. The content of gypsum as an impurity in the hardening agent calcium sulfite is preferably 3.5% by weight or less, and more preferably 2.5% by weight or less. If the gypsum content exceeds 3.5% by weight, the curing reaction will be too rapid and a suitable pot life will not be obtained. Activated magnesium oxide has iodine adsorption amount
50 to 250 mg・I/g・MgO, and 90 to 220 mg・
I/g·MgO is preferable. If the iodine adsorption amount is less than 50mg・I/g・MgO, a water-resistant cured composition cannot be obtained;
If it exceeds , the pot life will be extremely short and workability will be affected. When activated magnesium oxide is used as a curing agent, a high degree of water resistance and efflorescence resistance can be obtained, but because curing shrinkage is relatively large and mechanical strength is low, it is difficult to form a thick film with a thickness of 500 μm or more. It is desirable to use calcium sulfite in combination and increase the amount. The amount of hardening agent used is 15-250% relative to the _SiO2 content in the alkali metal silicate
% by weight is suitable, and 25 to 200% by weight is even more suitable. Coating compositions in which various pigments are blended with the above-mentioned alkali metal silicate and curing agent exhibit excellent physical properties such as water resistance when cured at room temperature, but are still insufficient to be suitable for roll coating. As a result of various experiments, the present inventors found that the thixotropic index of the above coating composition was approximately in the range of 9.5 to 12.0, and by adding a viscosity agent to this, the thixotropic index was increased to 4.0 to 8.5.
It has been found that the most appropriate roll coater suitability can be obtained by adjusting. (The thixotropic index is expressed as η ₆ /η _60, and the viscosity at 6 RPM with a BM type rotational viscometer is η ₆ and the viscosity at 60 RPM is η ₆₀ ). If the thixotropic index exceeds 8.5, the binder component and pigment component will be significantly separated on the roll coater, and the coating composition will not be uniformly distributed on the coating roll, making it impossible to achieve uniform coating. In order to improve the thixotropic properties in this manner, acrylic metal salts such as sodium polyacrylate and/or ammonium polyacrylate are used as the viscosity agent. That is, by adding 0.2 to 0.8% by weight of an aqueous solution of sodium polyacrylate and/or ammonium polyacrylate to the aqueous alkali metal silicate solution as a solid content, the thixotropic index of the present inorganic paint can be increased from 4.0 to 4.0.
8.5, and roll coater suitability improves dramatically. When celluloses such as carboxymethyl cellulose and hydroxyethyl cellulose, bentonite, white carbon, etc. are added, the above-mentioned remarkable thixotropic improvement effect cannot be obtained. The coating composition with improved thixotropic properties is applied to various substrates by natural roll coating or reverse roll coating. As a base material, calcium silicate board,
Noncombustible boards such as asbestos slate boards, rock wool boards, gypsum boards, and magnesium carbonate boards, and metal boards such as aluminum and stainless steel boards can be used. Next, examples and comparative examples will be described. Example 1 A cold-curing inorganic paint was prepared by blending each raw material as shown below (thixotropic index:
5.5). JIS No. 3 Sodium Silicate (SiO ₂ 30%, Na ₂ O 10%)
100 parts Calcium sulfite 30 Titanium oxide 100 Calcium carbonate 150 parts 3% Sodium polyacrylate 15 Water 15 Next, apply this inorganic paint to a 5 mm thick calcium silicate plate using the natural roll coating method (application amount : about 150 g/m ² ) and dried and cured for 24 hours to obtain an inorganic paint coated board. Example 2 A cold-curing inorganic paint was prepared by blending each raw material as shown below (thixotropic index:
7.0). JIS No. 3 Sodium silicate 100 parts Activated magnesium oxide (Iodine adsorption capacity 130 mg
I/g・MgO) 15〃 Titanium oxide 80〃 Calcium carbonate 120〃 3% ammonium polyacrylate 15〃 Water 15〃 Next, this inorganic paint was applied to a 4 mm thick asbestos slate board using the reverse roll coating method. Amount: 250 g/m ² ) was dried and cured for 24 hours to obtain an inorganic paint coated board. Example 3 An inorganic paint that cures at room temperature was prepared by blending each raw material as shown below (thixotropic index 5.0) Potassium silicate (SiO ₂ 20%, K ₂ O 11%) 150 parts Potassium sulfite 30 Magnesium oxide ( Iodine adsorption amount 130mg・I/
g・MgO) 10〃 Titanium oxide 100〃 Calcium carbonate 300〃 3% Sodium polyacrylate 25〃 Next, apply this inorganic paint to a 4 mm thick asbestos slate board using the reverse roll coating method (coating amount: approx. 400 g/ m ² ) and dried and cured for 24 hours to obtain an inorganic paint coated board. Comparative Example 1 Same formulation thixotropic index as Example 2 except that ammonium polyacrylate was not added.
11.0) and obtained asbestos slate board coated with inorganic paint. Comparative Example 2 An asbestos slate plate coated with an inorganic paint was obtained in exactly the same manner as in Example 2, except that the flow coater method was used. The performance of the coating films of the inorganic paint-coated plates obtained in the above Examples and Comparative Examples is shown in the following table.

[Table] In Comparative Example 1, the number of coatings required to obtain the same coating thickness as in Example 2 using the roll coater method was three times. (Effects of the Invention) As described above, according to the present invention, a viscous inorganic paint composition suitable for a roll coater method can be obtained by blending a viscosity agent into a room temperature curable inorganic paint to improve thixotropic properties. By applying roll coater coating to various boards, it is possible to produce coated boards that are uniform, have no pinholes, etc., and have excellent adhesion to the base material.

Claims (1)

[Claims] 1 Using an alkali metal silicate aqueous solution as a binder, the adsorption amount of calcium sulfite and/or iodine is
Add an alkali metal salt of polyacrylic acid and/or ammonium polyacrylate to a cold-curable inorganic paint using activated magnesium oxide of 50 to 250 mg I/g MgO as a hardening agent, and adjust the thixotropic index to 4.0 to 8.5. A method for manufacturing coated boards, characterized in that various boards are coated using a roll coater method.