JP2615407B2 - Coating composition and method of forming vitreous coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention while the component useful alkali metal silicates (waterglass) as a non-machine quality coating various materials, the water resistance with a bond strength of moderately water-insoluble markedly improved those related to the coating materials to form a coating film of glassy.

[0002] The coating material of the present invention can easily form a non-combustible, water-resistant, high-hardness vitreous cured product having excellent water resistance. is suitable use <br/> have Runoni the surface coating of the like.

[0003]

2. Description of the Related Art An aqueous solution of a water-soluble alkali metal silicate, which is conventionally known as water glass, forms a high-hardness vitreous coating film having excellent adhesion and film-forming properties when dried. Used as an adhesive for inorganic paints, cardboard, paper tubes, etc.
Old Kukara have been used Te. However, a vitreous coating formed from water glass originally had a problem in water resistance such as being water-soluble and not resistant to moisture. Also, since ordinary water glass, which has been used in large quantities since ancient times, is strongly alkaline, so-called efflorescence, in which even a sufficiently dried coating film absorbs moisture and carbon dioxide in the air and whitens the coating film.
It has the disadvantage of causing effloresnce (white flower phenomenon) and significantly impairing the appearance.

As a method for addressing these problems, the surface of the dried film of water glass is neutralized with acetic acid, phosphoric acid, dilute nitric acid, or the like, or an aqueous solution of a water-soluble ammonium salt is brought into contact with the surface of the film. Methods have been known, but all of these methods have problems in performance and workability, such as long processing time, blistering, peeling, and washing with water.

As a curing agent, a metal oxide such as zinc powder or a metal oxide of a polyvalent metal such as calcium, magnesium, or aluminum, or a metal hydroxide, a divalent metal such as aluminum phosphate or zinc phosphate is used. It is also known to use phosphates, borates, sodium silicofluoride, ferrosilicon, ethylene carbonate, glyoxal, polysaccharide pullulan, and the like. There is a problem with the properties and the pot life is so short that mixing adjustment on site is necessary. In general, the coating film becomes opaque or has poor gloss due to the mixing of the curing agent, and is not practical for a vitreous coating for cosmetic purposes.

In the prior art, heat treatment of water glass has also been attempted, but the temperature at which the water glass is insolubilized depends on the molar ratio, but in the case of the commonly used No. 3 water glass, the temperature exceeds 170 ° C. It needs to be heated. However, when heated to 110 ° C, the coating film foams, causing many bubbles and pinholes in the coating film. When heated to 130 ° C or more, the coating film foams significantly, loses transparency, and breaks down. There was a point. As a method of improving water resistance, SiO ₂ / M
_It is considered effective to use sodium silicate (water glass No. 4), lithium silicate, or quaternary ammonium salt of silicic acid having a high 2O ratio. And peeling and cracking are remarkable and have almost no film-forming property. For this reason, in the prior art, a method of blending an emulsion of ethylene-vinyl acetate copolymer and zinc white to improve the adhesion has been known, but the coating method which is a feature of water glass forming a vitreous coating film is known. In addition to impairing the transparency, hardness and glossiness of the film, the organic emulsion of the binder is liable to agglomerate and has problems in workability and stability of the mixed system.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide the conventional water-soluble alkali metal silicate (water glass) with excellent properties such as nonflammability, adhesion, high hardness, high gloss and economy. Utilizing water, it solves the drawbacks such as poor water resistance of water glass and the phenomenon of whitening caused by carbon dioxide gas in the air. It is to form a coating film on the surface of various materials .

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, completed the present invention. That is, according to the present invention, the general formula M ₂ O · nSi
O ₂ (where M represents sodium or potassium, n
JP resole resin is an initial condensate of phenolic resins synthesized from bisphenol A and formalin in an aqueous solution of alkali metal silicate represented by the number of 2 to 4) is
Dissolved uniformly without phase separation at a constant composition ratio, compositions based on water glass according resole resin is uniformly dissolved, crack or peel when naturally dried coating to a substrate such as a glass plate He knew that a high-hardness coating film with good adhesiveness could be formed without forming, and surprisingly, only a few minutes of heat treatment at a relatively low temperature of 120 to 200 ° C. was the biggest drawback of water glass. The present inventors have found that the lack of water resistance has been significantly improved, and have completed the present invention.

That is, the present invention relates to a 100 wt.% Aqueous solution of silicic acid of No. 2 to No. 4 which is known as a commercially available soda water glass.
In part, 0.5-10 parts by weight of obtained resole resin (N.V. 61 to 63%) was synthesized from bisphenol A,
More preferably, it is composed of a composition obtained by mixing and dissolving at a ratio of 3 to 6 parts by weight, and the composition is mixed with a glass plate, a metal plate, wood,
After coating or impregnating on various substrates such as cement and gypsum, after natural drying or heat drying, 110-150 ° C
Heat treatment for about 5 to 30 minutes to form a vitreous surface coating with very high hardness and excellent water resistance
it can.

The water glass used in the present invention has the general formula M
Sodium silicate or potassium silicate represented by ₂ O · nSiO ₂ (n is 2.0 to 4.1) can be used, and more preferably, a lithium silicate aqueous solution (lithium water solution) having a molar ratio of 4.5 is used. Glass) is used in a mixture of 10 to 50% by weight, or a No. 4 soda water glass having a molar ratio of 3.1 is mixed with a No. 4 soda water glass having a molar ratio of 3.9 from 50:50 to 1
Mixing at a ratio of 0:90 also gives good results.

As the resol resin used by mixing with water glass, an oligomeric resol resin synthesized from bisphenol A and formalin, which is an initial condensate of a phenol resin, is more effectively used. The resole resin synthesized from phenol (phenol) and formalin is discolored to red by triphenylmethane-type coloring, which is considered to be formed by the oxidative condensation of the methylene bond at the para-position of the phenolic hydroxyl group with another phenol or polynuclear. It is not desirable.

The method of the present invention is characterized in that the oligomeric resole resin is uniformly dissolved in water glass of which concentration has been adjusted and the solution composition can be stored stably for a long period of time. The production of formula processing is easy and the workability is good. In particular, when the composition is naturally dried after coating or forcibly dried at about 60 to 100 ° C., and then further subjected to a heat treatment at 120 to 200 ° C., curing is further advanced in a short time, resulting in extremely high hardness and excellent water resistance. That is, a high-gloss glassy film is formed.

Conventionally, the insolubilization of a coating film using water glass is performed by adding a hardening agent such as zinc oxide, zinc dust, calcium carbonate and ethylene carbonate, heat-treating the coating film at a high temperature after forming the coating film, and neutralizing the alkali on the surface with a dilute acid. For example, a method of immersion in an aqueous solution of ammonium salt for a long time has been proposed, but there have been serious problems in workability such as rapid thickening, gelation and pot life, foaming and generation of pinholes. In addition, it is generally difficult to form a glossy film by these methods.

On the other hand, according to the method of the present invention, after air drying or forced drying at 60-100 ° C., 120-200.
0 ° C desirably only heat treatment from 120 ° C to 180 ° C for about 5 to 10 minutes, so there is no problem of pot life, and since heat treatment is performed at a relatively low temperature, there is little generation of pinholes and foaming and high gloss. A vitreous, water-resistant coating film can be formed. Of course, it is also possible to rapidly cure using a known curing agent in combination.

In order to form a coating film on the substrate surface using the coating material of the present invention, the coating material of the present invention is applied to the substrate surface and dried, and then the dried coating film formed on the substrate surface is heat-treated. Just do it. As a coating method, various methods such as spraying, roller coating, brush coating, and iron coating are employed. Coating materials include
If necessary, an appropriate amount of filler such as powdered silica, alumina, talc and the like can be added.

The coating film obtained by coating the composition according to the present invention is a vitreous coating film having a Knoop hardness of 200 to 300, which can be cured at a low temperature of 120 to 130 ° C. It is a great feature that it has water resistance and efflorescence resistance that were not considered in such cases. In addition, since the raw materials such as water glass are very inexpensive, the composition of the present invention is a breakthrough as an industrial material that can be used up to civil engineering and construction.

[0017]

EXAMPLES Next, the production example of the resole resin used in the present invention and the formation of a coating film using a mixed composition of water glass and the resole resin will be described more specifically based on examples. It is not limited to only examples.

Production Example 1 150 g of bisphenol A, 30 g of 48% caustic soda, 208 g of 37% formalin, and 4 g of a 1-liter glass corvette equipped with a mantle heater, thermometer, stirrer, reflux condenser and dropping funnel Water 10
0 g was charged. Gradually heat up with mantle hitter 6
It was kept at 0 ° C. for 2 hours. After the reaction, add 50 g of water and
While maintaining 0 ° C., 23 g of 78% sulfuric acid was dropped and neutralized,
After sufficient stirring, the mixture was allowed to stand, and the upper layer was separated and removed to obtain a brown transparent resole resin.

Example 1 In a 50 ml Erlenmeyer flask, JIS standard No. 3 water glass made by Fuji Chemical (SiO ₂ 28-30%, Na ₂ O 9-10)
%, A molar ratio of 3.1 to 3.3, and the remaining moisture) to 10 g of a lithium silicate solution LSS-45 (Si
A mixture of 5 g of O ₂ 22.0% and Li ₂ O 2.2%) was mixed with 6 g of water and 1 g of the resole resin shown in Production Example 1 using a magnet stirrer to dissolve the mixture. Solution was obtained. The above composition was applied to the surface of a transparent sheet glass, and after natural drying, a heat treatment was performed on a hot plate at 120 to 140 ° C. for 5 to 10 minutes. A vitreous coating film having good adhesion was formed. The hardness of the coating film is very high, and the Knoop hardness by the Terada micro hardness tester (SM-2 type) is KH = 2.
96, which is excellent in scratch resistance. Further, even when the coating film was immersed in water for one month or more, no change was observed in the surface state, and the water resistance, which was a disadvantage of the water glass coating film, was significantly improved. Further, the coating film was left for 6 months or more, but no efflorescence phenomenon due to carbon dioxide gas absorption was observed.

Comparative Example 1 In Example 1, the coating film which was air-dried or merely dried at 100 ° C. or lower had a considerably high surface hardness, a Knoop hardness KH = 215, and a vitreous high-gloss coating film having good adhesion. Met. However, as soon as the coating was immersed in water, the surface peeled off and the coating completely dissolved.

Comparative Example 2 In Example 1, when only a mixed water glass of sodium silicate and lithium silicate was applied on a glass plate without adding a resole resin and air-dried, a colorless and transparent adhesive having good adhesion was obtained. A vitreous coating having a hard surface was obtained. However, when the coating film was left for about one month, the coating film gradually became white from the peripheral portion, and finally became white and opaque. Further, when the coating film was heated to 120 to 130 ° C., bubbles were generated on the coating film surface, and pinholes were generated.

Example 2 In the same manner as in Example 1, 10 g of No. 3 water glass and 5 g of lithium water glass (LSS-45) were mixed to form a water glass system.
1 g of the resole resin shown in Production Example 1 was added to 4 g of water, mixed and dissolved.
g of glycerin was added to prepare a homogeneous solution. The composition is applied to a stainless plate, an aluminum plate, a chrome-plated plate, a glass plate, and the like, and is naturally dried.
When heat-treated for 10 minutes to 10 minutes, a water-resistant yellow-white translucent coating film was formed. The hardness of the coating heated to 120 ° C. was Knoop hardness KH = 136.

Example 3 In Example 1, when the amount of the resole resin was reduced to 1/5 by 0.5 g, a uniform solution was easily prepared only by adding 2 g of water. As a result, a transparent film having good water resistance and very high hardness (Knoop hardness KH = 306) was obtained. However, in this case, heating to 130 ° C. produces pinholes,
At 0 ° C., foaming was significant. When no resole resin is used, foaming occurs at 120 ° C. When 1 g of resole resin is used, no foaming occurs at 150 ° C., and foaming is observed when heated to 170 ° C. or higher. Has the effect of doing

Example 4 In Example 1, when only 0.5 g of resol resin was mixed with 15 g of No. 3 soda water glass as water glass, 2 to 6 g of water was different from Examples 1 to 3. When added, the composition cannot be uniformly dissolved, and the liquid composition separates into two phases.
In order to make the system uniform, it was necessary to add 9 to 12 g or more of water. Although the coating film had good adhesion and formed a hard film, it had poor water resistance when heated at 120 ° C.
Water resistance was achieved by heating to 0 ° C. or higher.

[0025]

As described above, a water glass system having a mixing ratio in a limited range and a heat treatment at a limited temperature of 120 to 180 ° C., preferably 120 to 180 ° C. are widely used. The lack of water resistance and the whitening phenomenon (eflorescence) due to absorption of carbon dioxide, which are the biggest drawbacks of the No. 3 soda water glass, have been improved. A vitreous or enamel-like coating film having excellent weather resistance, flame resistance, and high hardness, which cannot be obtained with a system paint, can be formed. In addition, since water is used as a medium, it is excellent in pollution-free properties and workability. From this, the surface of wood, various metals, concrete, mortar, asbestos slate, natural stone, glass, plastic, gypsum and the like can be coated with a vitreous or enamel-like hard coating .

Claims (2)

(57) [Claims] During 1. A general formula M ₂ O · nSiO ₂ (wherein, M is alone or the Na or K in an alkali metal, show the two mixed system of which, n represents 2.0 to 4.
Bisphenol A to 100 parts by weight of an aqueous solution (water glass) of an alkali metal silicate represented by
A resol resin, which is an initial condensate of a phenolic resin obtained by synthesizing as a raw material, is dissolved in 0.5 to 10 parts by weight.
A coating composition comprising: 2. The composition according to claim 1, which is applied to a substrate,
After natural drying or forced drying at 100 ° C or less,
A method for forming a water-resistant glassy coating film, characterized by heating at 200 ° C.