JPS5853589B2 - How to apply inorganic paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for applying an inorganic paint, and particularly to a method for forming a uniform paint film and preventing pinholes from forming on the surface of the paint film.

In the past, organic paints were generally widely used, but flame retardant, smokeless, non-combustible properties, etc. have become highly desirable, and the paints in practical use have changed from organic solvent-based organic paints to water-based synthetic resins. There has been a transition to emulsion paints and then to water-based inorganic paints.

Conventionally used coating methods include the spray method, brush coating method, roll coater method, curtain flow coater method, etc., but newly proposed coating methods require new coating methods that are compatible with these methods. It has been proposed.

The coating method using a curtain flow coater is promising because there is almost no loss of paint during coating and the amount of coated paint can be adjusted over a wide range. When this method is applied, pinholes, bubbles, etc. occur in the coating film, making it difficult to apply it practically to inorganic coatings.

Inorganic paints generally consist of binders, fillers, pigments, dispersants, dispersion aids, etc. However, as mentioned above, it is difficult to apply the coating method using a curtain flow coater, so spray coating methods are generally widely used. ing.

However, spray coating causes a lot of paint loss and has poor coating efficiency, so a coating method suitable for inorganic paints has been strongly desired.

The inventors of the present invention have previously conducted various studies on inorganic paints containing lithium silicate, silica sol, alumina sol, etc. as binders, and as a result of intensive experimental research on coating methods, they have found that Roll coater in advance
discovered that if an inorganic paint or an aqueous solution of the binder contained therein is applied, a uniform and pinhole-free paint film can be obtained by applying a curtain flow coater over the inorganic paint, and the present invention was completed. reached.

The present invention provides an inorganic paint containing silica sol, alkali silicate, or a mixture thereof, alumina sol, or aluminum phosphate as a binder, or a resin in an amount of 200 weight tons of solids in the binder. After applying the composite inorganic paint on the surface of the object to be coated using a roll coater,
The inorganic paint coating method further comprises applying the inorganic paint or composite inorganic paint thereon using a curtain flow coater.

An object of the present invention is to provide an efficient coating method for obtaining a uniform and thick coating without producing bubbles or pinholes on the coating surface.

The coating film obtained by the method of the present invention not only has uniform hardness and smoothness, but also has uniform gloss.

The inorganic paint used in the present invention contains silica sol, alkali silicate or a mixture thereof, alumina sol or aluminum phosphate as a binder, and as necessary, a dispersant, dispersion aid, filler, pigment, curing agent, etc. is blended.

The composite inorganic paint used in the present invention is one in which the inorganic paint further contains a resin component in an amount of 200 weight molecules of the solid content in the binder.

The silica sol used as a binder in the present invention is dispersed in water or a water-soluble organic solvent such as methanol, ethanol, inpropatol, glycerin, ethylene glycol, acetone, dimethylamine, etc., or a mixed solvent of these and water. medium, and the particle size is about 3 to 150 μm
It is a product in which colloidal silica is dispersed, and is usually acidic or alkaline, and contains a 5i02 concentration of 3 to 60% by weight.

In particular, it is stabilized with a caustic alkali or a nitrogen-containing organic base, such as various ammoniums, quaternary ammonium hydroxide, etc.
A high molar ratio of silica to the above-mentioned caustic alkali or organic base is preferable because it improves the water resistance and weather resistance of the inorganic paint.

The alkali silicates used as binders in the present invention include amine silicate, guanidine silicate, sodium silicate,
Potassium silicate, lithium silicate, etc., and usually have a pH of 6 to 6.
The inorganic paint is preferably used as an aqueous solution containing water-soluble reduced size or colloid particles with a 5i02 concentration of 12 to 40, and the higher the molar ratio of silica to alkali, the better the water resistance of the inorganic paint.

A mixture of the alkaline silica sol and the alkali silicate may also be used as a binder in the present invention.

Regarding this mixture, as above, the higher the molar ratio, the more preferable it is.

The alumina sol used as a binder in the present invention uses water or a water-soluble organic solvent as a dispersion medium, and the same water-soluble organic solvent as used for the above-mentioned silica sol can be used.

It is usually stabilized with an organic or inorganic acid, has an Al2O3 concentration of about 2 to 25, and has a pH of 1 to 8.

The aluminum phosphate used as a binder in the present invention includes monoaluminum phosphate, dibasic aluminum phosphate, and the like.

In the present invention, an aqueous solution containing about 5 to 60% solids is usually used.

Examples of resins included in the composite inorganic paint used in the present invention include polymethyl acrylate, polyethyl acrylate, methyl acrylate-butyl acrylate-styrene copolymer, polyvinyl acetate, and ethylene-vinyl acetate copolymer. , vinyl ester of versatic acid-vinyl acetate copolymer, styrene-butadiene copolymer, polyurethane resin, synthetic resin or synthetic rubber such as epoxy resin, sodium polyacrylate, polyvinyl alcohol, carboxymethylcellulose, methylcellulose, urea resin, melamine Examples include water-soluble resins such as resins and phenol resins.

In the present invention, the synthetic resin or synthetic rubber is usually used as an emulsion, particularly preferably an aqueous emulsion, and the water-soluble resin is used in the form of a fine powder or an aqueous solution.

These resins are included in the inorganic paint in a proportion of 200 gw based on the solid content in the binder.

If it is included in a proportion of more than 200% by weight, the desirable properties of the inorganic paint will be impaired, such as weather resistance, nonflammability, smokelessness, etc., will be significantly reduced, and it will be difficult to obtain a hard inorganic paint film.

The inorganic paint or composite inorganic paint used in the present invention can be obtained by uniformly mixing the binder, filler, pigment, dispersant, dispersion aid, curing agent, resin, etc. using a mixer, forced stirrer, etc. It is cured by drying at room temperature or under heat.

In the present invention, the objects to be coated with the above-mentioned inorganic paint or composite inorganic paint include a wide range of objects such as hardened cement, gypsum boards, asbestos slate boards, calcium silicate boards, wood, wood plywood, cloth, and metal surfaces. It is.

The inorganic paint or composite inorganic paint used in the present invention has excellent performance, but when it is applied directly to the surface of the object to be coated using a curtain flow coater, air bubbles may form in the resulting coating film. Alternatively, pinholes may occur or there may be many uneven coatings, making it impossible to obtain a desirable coating film.

It is thought that pinholes are caused by air bubbles retained in the paint film that click and collapse in the latter stages of the drying process.

The inventors of the present invention have made strenuous efforts to investigate the cause of air bubbles occurring when painting with a curtain flow coater, and have found that there are no air bubbles in the fluid film hanging down from the curtain flow coater. , as well as the fact that there are few air bubbles in the coated film that exhibits surface properties that are easily wetted by the above-mentioned inorganic paints, and when the fluid film hanging down from the curtain flow coater is coated on the surface of the coated object, it is in a fluid state. It was found that air interposed between the coating and the surface of the object to be coated appears as bubbles in the fluid film or on the surface, and furthermore, when applying the above-mentioned inorganic paint or composite inorganic paint with a roll coater, It was also found that no air was present between the film and the surface of the object to be coated, and that no air bubbles or pinholes were generated in the coating film.

The present inventors further investigated the reason why bubbles or pinholes do not occur in the paint film when applying the above-mentioned inorganic paint or composite inorganic paint with a roll coater, and found that the paint on the roll coater When transferred to the surface, the air on the surface of the object to be coated is quickly replaced by the fluid coating film, and the air on the surface is expelled from the coating film, resulting in a close bond between the surface of the object and the coating film. It was found that no air bubbles were generated in the coating film.

When pre-coating with a roll coater, not only the above-mentioned inorganic paint or composite inorganic paint is applied, but also its binder or its aqueous solution, such as silica sol, alkali silicate aqueous solution or a mixture thereof, alumina sol, aluminum phosphate. It has also been found that aqueous solutions and even water alone can be applied.

Further, in the method of the present invention, the above-mentioned inorganic paints, composite inorganic paints, silica sol, aqueous alkali silicate solutions or mixtures thereof, alumina sol, aqueous aluminum phosphate solutions are coated in advance on the surface of the object to be coated with a roll coater. ,
Surprisingly, it has been found that when the inorganic paint or composite inorganic paint is further applied to the applied surface using a curtain flow coater, no bubbles or pinholes occur in the paint film. It was done.

This effect is obtained by applying the above-mentioned inorganic paint, composite inorganic paint, silica sol, alkali silicate aqueous solution or a mixture thereof, alumina sol, aluminum phosphate aqueous solution, water, etc. with a roll coater to the coating surface and hanging from the curtain flow coater. The fluid coating film is thought to be due to the fact that the adhesion effect due to wetting is sufficient and no air is trapped at all.

Before applying the inorganic paint or composite inorganic paint using a curtain flow coater, it is preferable to apply the coating using a roll coater while the coating surface obtained is sufficiently wet.

Even if the inorganic paint or composite inorganic paint is applied to the surface of the object to be coated using only a roll coater, a thick coating cannot be achieved, the surface of the object to be coated cannot be sufficiently hidden, and a more uniform coating film cannot be achieved. Hard to get.

The method of the present invention essentially consists of a coating process using a roll coater and a coating process using a curtain flow coater. It may be allowed to stand, or it may be dried without being allowed to stand, or after being allowed to stand naturally, at a preferred temperature for a convenient period of time.

Even after the coating process using the curtain flow coater, a preferable coating can be achieved by allowing the coating to stand naturally and drying as described above.

The coating film obtained by the method of the present invention exhibits uniform gloss and excellent performance as an inorganic paint, and the method of the present invention is simple and efficient, making it extremely useful.

The properties of the binders used are shown in Table 1 below, which will be explained in more detail with reference to Examples.

Example 1 (a) Preparation of paint In a 10-liter enamel vat equipped with a high-speed stirrer, 5 liters of water was added.
0 kg of silica sol A shown in Table 1 was added under stirring. 4.5 kg of aqueous emulsion of ethyl acrylate containing 50% solids by weight, 0.2 kg of methyl sefflerose, bentonite)11. Calcium carbonate passed through 29,200 meshes of sodium polyacrylate 400kp
, 50 ky of silica powder that had passed through 300 meshes and 50 kg of methane oxide were sequentially added thereto, followed by forced stirring for 1 hour to prepare paint (I).

(B) Coating test Prepare an asbestos slate board P1 with length and width of 300n+n+ and 600mm, thickness of 6mm, and specific gravity of 1.6, and separately put it on a roll coater with a width of 600mm. ) The asbestos slate plate was fed at a feed rate of 20 while keeping the paint CI) prepared at 21 uniformity at all times.
6 m/min onto the asbestos slate board.
The coating amount was 0!9/rrt.

Immediately thereafter, using a curtain flow coater with a width of 600 mm, the coating material α) was applied at a rate of 50 m/min to the coated asbestos slate board at a rate of 250.9 m/m, and after being left at room temperature for 3 minutes, it was heated to 90'C. Leave it in the dryer for 1
Dry for 0 minutes.

Then, it was taken out of the dryer to obtain a painted asbestos slate board.

When the coating surface of the obtained coated plate was closely observed with the naked eye, there were no bubbles or pinholes, and the gloss was uniform.

*2: Based on paint boiling in Table 2.

Beau 3: Use a spray instead of a roll coater.

Examples 2 and 3 0) Preparation of paint A paint (
I), (II) and (IV) were prepared.

(b) Painting test Prepare a pulp cement board P2 with a specific gravity of 1.2 and a thickness of 4 mm and a special asbestos slate board P3 with a specific gravity of 1.6 and a thickness of 3 mm, cut into the same dimensions as in Example 1. , 3rd. Roll coater coating and curtain flow coater coating were performed in the same manner as in Example 1 under the conditions shown in the table.

The coating films of the obtained coated plates were all good as shown in Table 3.

Comparative Example 1 The same asbestos slate board P1 used in Example 1 was prepared, and the paint (I) was applied to it under the conditions shown in Table 3 in the same manner as in Example 1, without applying it with a roll coater. I painted the curtains with a flow coater.

There were many bubbles and pinholes in the paint film of the painted board, and the paint film was not uniform.

Comparative Example 2 The same pulp cement board P2 as used in Example 2 was prepared, and only the binder used in the preparation of paint (I) was added to it.
It was applied with a 0g/m spray, and after being left for 5 minutes, the paint ω was immediately applied using a curtain flow coater under the conditions shown in Table 3 in the same manner as in Example 1.

The paint film on the painted board had many bubbles and pinholes, and was non-uniform.

Example 4 A coated board was obtained in the same manner as in Example 1 except that ([11)] was used as the paint.

Example 5 A coated board was obtained in the same manner as in Example 1, except that paint (I) was used for coating with an 0-lu coater, and paint ([) was used for coating with an old curtain flow coater.

Example 6 Painting by Curtain Flow Coater A coated board was obtained in the same manner as in Example 3, except that Km material (V) was used.

The coating films of the coated plates obtained in Examples 4, 5, and 6 above were all uniform, and no bubbles or pinholes were observed.

Claims (1)

[Claims] 1. An inorganic paint containing silica sol, alkali silicate, or a mixture thereof, alumina sol, or aluminum phosphate as a binder, or the inorganic paint is impregnated with a resin in an amount of 200 weight tons of the solid content in the binder. 1. A method for applying an inorganic paint, which comprises applying a coated composite inorganic paint onto the surface of a workpiece using a roll coater, and then applying the inorganic paint or composite inorganic paint thereon using a curtain flow coater.