JPH09328351A - Transparent glassy material forming composition and formation of coated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-temperature hardenable composition as a hardenable composition using a water-soluble alkali metal silicate, providing a coated film excellent in water resistance and efflorescence resistance. SOLUTION: This low-temperature hardenable composition obtained by blending a water glass shown by the formula M2 O.nSiO2 (n=2.0 to 3.3; M is an alkali metal and is Na or K alone or a mixed system) with 5-10wt.% of sodium dihydrogenphosphate or in a limit amount not to precipitate at a normal temperature is forcibly dried and hardened at a low temperature of 80-150 deg.C to give a glassy solid material and a coated film having water resistance and excellent adhesiveness free from efflorescence.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transparent vitreous forming composition containing a water-soluble alkali metal silicate known as water glass as a main component and useful as an inorganic coating material, an adhesive and the like and its use. In particular, it can form a strong bond as a binder, adhesive, etc. for various base materials, and it can be used on metal products, wood, cement products, gypsum, plastic, etc. The present invention relates to a low-temperature curable transparent vitreous forming composition which can be cured at a low temperature, forms a vitreous coating film having high gloss, colorless and transparent, and having extremely improved water resistance and efflorescence resistance.

[0002]

2. Description of the Related Art Conventionally known as water glass, a water-soluble alkali metal silicate is an inexpensive inorganic paint because it forms a glassy coating film of high hardness having excellent adhesion and film-forming property when dried. It has been used for a long time as an adhesive for corrugated board, paper tubes, etc., as a soil hardening agent, a binder for foundry sand, and a binder for refractory mortar. However, the vitreous coating film formed from water glass originally has a problem in water resistance such as being water-soluble and not resistant to moisture.

Further, since water glass is strongly alkaline, even a sufficiently dried coating film absorbs moisture and carbon dioxide in the air to cause effloresnce (white flower phenomenon) in which the coating film is whitened, and the appearance is significantly impaired. It has drawbacks.

In order to solve these problems, a method of neutralizing the surface of a conventional dry glass coating film of water glass with acetic acid, phosphoric acid, dilute nitric acid or the like, or bringing the coating solution surface into contact with an aqueous solution of ammonium chloride salt. However, there are problems in workability and performance such as swelling with water, damage to the coating surface such as cracks and peeling, and the need for washing with water.

Further, as a curing agent, a metal such as zinc dust or a metal oxide of a polyvalent metal such as calcium, magnesium or aluminum, or a metal hydroxide, or a divalent or trivalent metal such as aluminum phosphate or zinc phosphate. Metal phosphates,
Methods using borate, sodium fluorosilicate, ferrosilicone, ethylene carbonate, glyoxal, and pullulan of polysaccharides are also known, but when these curing agents are used, rapid gelation occurs. There is a problem in workability, and when it is mixed with a curing agent, it becomes opaque and has poor gloss, which is not practical for a glassy coating for the purpose of beauty.

Further, in order to improve water resistance, it has been attempted to heat-treat water glass in the prior art. Film-forming property,
In the case of No. 3 water glass, which is widely used in terms of adhesion and economy (JIS standard K 1408), it needs to be heated to 170 ° C or higher (450 ° C or higher for complete insolubilization), but to 110 ° C. There is a problem in that the coating film foams at the stage of heating and a large number of pinholes are formed in the coating film, and when heated to 130 ° C. or more, the coating film foams remarkably and loses transparency and the coating film is broken. Further, the heat resistance alone does not sufficiently improve the water resistance and the efflorescence.

Further, as a method for improving water resistance, SiO ₂ /
It is also effective to use No. 4 water glass having a high Na ₂ O ratio, lithium silicate, or a quaternary ammonium salt of silicic acid, but the substance has poor adhesion as a coating film, and peeling and cracking are remarkable. Can not stand. From this, methods such as using lithium water glass or No. 4 water glass mixed with No. 1 to No. 3 water glass, or mixing with an emulsion of ethylene-vinyl acetate copolymer have been known. Inferior in sensitivity.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide excellent properties such as nonflammability, adhesion, high hardness, high gloss, and economical efficiency of conventional water-soluble alkali metal silicates (water glass). While taking advantage of the water resistance of water glass and the drawbacks such as whitening phenomenon due to carbon dioxide in the air, it has excellent workability, non-combustibility, water resistance and high hardness with high adhesion and good adhesion. Glass coating film at 80-150 ℃
A curable composition that becomes a paint that can be formed on the surface of various materials at a relatively low temperature, and a solidified product that is inexpensive and has excellent water resistance and efflorescence resistance when mixed with various fillers as a binder It is to provide a low-temperature curable composition which is applied or used as an adhesive.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies, the present inventors have solved the drawbacks of water glass and provided a method of applying a glassy coating film to various materials at a relatively low temperature. , An aqueous solution of potassium dihydrogen phosphate or sodium dihydrogen phosphate, which is a specific inorganic compound, and alkali metal sodium silicate represented by No. 3 water glass defined in JIS K 1404 in a limited amount. It was found that a highly transparent coating film of high hardness can be formed without impairing the adhesiveness by simply mixing the coating film evenly with 80% to 80% of this coating film.
The present invention has been completed by discovering that the lack of water resistance and the efflorescence, which are the greatest drawbacks of water glass, are remarkably improved only by heat treatment at a temperature of 50 ° C. for several minutes to 30 minutes. In the present invention, the coating film means not only a coating film used as a paint but also a coating film used as an adhesive.

That is, the present invention provides (1) the general formula: M ₂ O · n
Water glass component (A) represented by SiO ₂ (wherein n is 2.0 to 3.3, M represents an alkali metal, and two Ms may be the same or different from each other). As the main component, and as the component (B), potassium dihydrogen phosphate KH ₂ PO ₄ or sodium dihydrogen phosphate N dissolved in water.
aH ₂ PO ₄ is added to and mixed with the water glass component (A) up to a limit amount at which precipitation does not occur at room temperature, and a transparent vitreous forming composition according to item (2) and (1). The glass-forming composition described is applied to a substrate and then 80-1
A method of forming a glassy coating film, which comprises forcibly drying at 50 ° C., and (3) bonding with the glassy composition described in item (1), followed by forced drying at 80 to 150 ° C. A bonding method is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the water glass component (A) is preferably a commercially available product of JIS standard Nos. 1 to 3 represented by M ₂ O.nSiO ₂ (n is 2.0 to 3.3). Sodium silicate is used alone, but an equivalent mixture of potassium silicate water glass, lithium water glass with a molar ratio of 4.5, and No. 4 sodium silicate with a molar ratio of 3.9 to 4.1 is also used. be able to.

The component (B) used in the present invention is
An aqueous solution is prepared in order to suppress the formation of a gelled mamoko that partially occurs when mixed with water glass and to facilitate dissolution and mixing, but potassium dihydrogen phosphate salt or phosphorus dissolved in water to a concentration of 5 to 10% by weight. Sodium dihydrogen acid salt is mixed with No. 3 sodium water glass, etc., and the limit amount immediately before gelation or precipitation occurs at room temperature (the amount that causes precipitation is the amount of time even if precipitation occurs during mixing, Often dissolves 4
It means the amount that does not dissolve evenly when left for 8 hours or more. ) Is desirable. In the present invention, the addition and mixing of the component (B) to the component (A) up to the limit amount at which precipitation does not occur at room temperature includes from the limit amount itself to the case where the concentration is 10% lower than the limit amount. Is.
The addition amount of the component (B) is preferably 1: 1 in the aqueous solution having a concentration of 5% by weight and 1/2 times that in the aqueous solution having a concentration of 10% by weight with respect to the water glass component (A). In the present invention, it is essential to use a dihydrogen salt as a phosphate, in order to improve efflorescence resistance, potassium monohydrogen phosphate monohydrogen salt, sodium monohydrogen phosphate phosphate, potassium phosphate, Sodium phosphate has little effect. Further, even when these dihydrogen phosphate salts were used, if the mixing amount was too small, it was insufficient to improve the efflorescence resistance. Also, the use of ammonium dihydrogen phosphate salt in place of potassium dihydrogen phosphate salt is liable to generate toxic and corrosive vapors, and should be avoided. Further, the calcium dihydrogen phosphate salt was unsuitable because it immediately precipitated calcium silicate. Phosphoric acid is a toxic substance and not only is troublesome to handle, but also markedly promotes gelation, and it is difficult to specify the amount to be added, the concentration, and the like. The thickness of the coating film formed in the transparent vitreous forming composition of the present invention,
Water can be added arbitrarily in consideration of workability, and the water content is not particularly limited.

The composition prepared with the dihydrogen phosphate salt as described above is a homogeneous, colorless, transparent and slightly viscous liquid. The transparent vitreous forming composition of the present invention can be used by coating it on a substrate or solidifying various substances by this composition. To describe this application method,
By coating the composition of the present invention on an iron plate, a glass plate and the like and then naturally drying it, a colorless and transparent and highly glossy vitreous film is formed, but the water resistance and efflorescence resistance are not sufficient. However, when forced drying at 80 to 150 ° C. is performed after coating, a colorless and water-resistant vitreous hard coating film that is colorless and transparent is rapidly formed. Surprisingly, the coating film shows no efflorescence even if left for more than one month.

Although the detailed reason for suppressing efflorescence by adding and mixing potassium dihydrogen phosphate is not clear yet, it is considered as follows. Condensation of water glass is further promoted by heat treatment to form a cage having a three-dimensional structure of polysiloxane. In this case, most of the Na ⁺ ions are directly linked to the siloxane bond through non-crosslinked oxygen, not through the surrounding water molecules. Via a chain or a polysiloxane-bonded network cage. However, since some Na ⁺ ions remain surrounded by water molecules in a highly mobile state, they absorb moisture and carbon dioxide in the air to form white sodium carbonate, which shows the white flower phenomenon. On the other hand, in the present invention, the dihydrogen phosphate ion is dissociated as in the following formula. _{^{H 2 PO 4 - → HPO 4}} 2- + H + HPO 4 2- → PO 4 3- + H + where dihydrogen phosphate ions hydrogen phosphate ions, while being neutralized like phosphate ions, water molecules All of the Na ⁺ ions that remain partially in the state surrounded by are formed into a water-insoluble salt by the reaction represented by the following formula, and the Na ⁺ ions are fixed. _{Na 2 O · xSiO 2 + H} 2 O → xSi (OH) 4 + Na + + OH - Na + + H 2 PO 4 - + nSi (OH) 4 → NaH 2 PO 4 · nH 4 SiO 4 ↓ 2Na + HPO 4 2- + nSi (OH) ₄ → Na ₂ HPO ₄ · nH ₄ SiO ₄ ↓ It is considered that the generated insoluble salt is glassy and is embedded in the polysiloxane formed by the water glass to form a denser insoluble protective film.

The method of applying the composition of the present invention to a substrate is not particularly limited, and ordinary coating methods such as spray gun, roller coating, doctor knife, brush coating, and iron coating can be employed in addition to dip coating. In this case, a filler such as powdered silica, alumina or talc, a pigment or the like may be added to the composition.

As the base material, wood, various metal panels, metal parts, corrugated board, roof tile, concrete products, asbestos,
It can also be used for hard coating of transparent plastics by using slate, natural stone, gypsum, and a suitable primer.

The coating film obtained by coating the composition according to the present invention is preferably dried by force at 80 to 150 ° C., so that it has excellent water resistance and does not show efflorescence due to carbon dioxide gas in the air. A colorless and highly glossy vitreous coating film can be formed.

The coating film thus formed has a very high Knoop hardness of 300 to 400 as measured by a microhardness meter, but has excellent adhesion to various base materials such as iron plates, wood and paper products. Excellent weather resistance, flame retardancy, and scratch resistance. In the present invention, especially 80
It is a major feature that it can be cured at a low temperature of ℃ to 150 ℃, and has excellent water resistance and efflorescence resistance that could not be considered by conventional water glass paints.

Further, the low-temperature curable composition of the present invention is a water-resistant and alkali-stain-resistant (no migration of strong alkaline substance) hard and strong adhesive for corrugated paper and paper tubes, in addition to the formation of the above-mentioned coating film. It is also useful as a binder for various aggregate particles such as clay, stone powder, glass powder and incinerated ash. In this case, if it is cured by heating at 120 to 200 ° C. after molding, a strong glass-like cured body having water resistance can be obtained. Moreover, since the raw materials such as water glass are very low in price, the composition of the present invention
It is an epoch-making material as an industrial material that can be used for various purposes including civil engineering.

[0020]

EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to such examples. In the examples,% indicating the composition indicates% by weight.

Example 1 When 100 g of JIS No. 3 water glass (manufactured by Fuji Chemical Co., Ltd.) was mixed with 50 g of a 10% aqueous solution of potassium dihydrogen phosphate, a precipitate was first formed and solidified into a gel, but after 24 hours. As a result, a transparent sol solution composition which was dissolved in a uniform transparent state and had a slightly long-term stable viscosity was formed.

A glass plate having high gloss and good adhesion is obtained by polishing the above composition with an iron plate for can-making using sandpaper, coating the composition with an applicator, and immediately heating and drying it on a hot plate at 120 to 150 ° C. for 5 to 10 minutes. A good quality coating 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 = 316.
It has excellent scratch resistance with no scratches even when strongly rubbed with No. 0 steel wool (central type 25 μm). The coating film formed by natural drying had poor water resistance, and when immersed in water, the coating film peeled and dissolved. However, in the case of the coating film which was forcibly dried and cured at 150 ° C., no change in the surface condition was observed even when immersed in water, and the water resistance, which was a drawback of the water glass coating film, was remarkably improved. Further, the whitening (efflorescence) phenomenon due to absorption of carbon dioxide gas was found to be efflorescence with time in the case of natural dry curing, but it is considerably reduced by the method of the present invention as compared with the case of water glass alone. Further, when heat-dried and cured at 150 ° C., no efflorescence was observed even after being left for a long time.

Comparative Example 1 A transparent sol solution was prepared in the same manner as in Example 1 except that the amount of the aqueous potassium dihydrogen phosphate solution mixed with water glass was 25 g, which is half of that in Example 1. A composition was prepared. In this case, a uniform colorless and transparent composition liquid is obtained without gelation when mixed with water glass, but the coating film obtained by forced drying and curing on an iron plate at 150 ° C. in the same manner as in Example 1 is water resistant. It has excellent properties and is greatly improved compared to the case of using water glass alone. But,
Efflorescence was observed over time, and the coating film surface was whitened.
However, this whitening could be easily removed by washing with water and restored.

Example 2 In the same manner as in Example 1, 100 g of JIS standard No. 3 water glass was added with 100 g of a 5% potassium dihydrogen phosphate aqueous solution.
When mixed, there is little formation of precipitates and can be mixed uniformly,
Over time, a colorless and transparent low-viscosity sol solution was obtained. Apply this composition liquid to glass plate, wood, iron plate, slate plate, etc. 1
It was heat-dried and cured at 20 ° C. The formed coating film was excellent in water resistance and efflorescence resistance, had good adhesiveness, was colorless and transparent, and had high gloss. The hardness of the film was Knoop hardness KH = 350.

Comparative Example 2 In Comparative Example 1, 5 g per 100 g of JIS standard No. 3 water glass was used.
When 350 g of an aqueous dipotassium hydrogen phosphate solution was mixed, an unexpectedly transparent composition liquid was initially obtained, but it became white and opaque over time, and eventually the whole solidified.

Comparative Example 3 When 100 g of JIS standard No. 3 water glass was mixed with 5% disodium hydrogen phosphate, even if 200 to 400 g of them were mixed and allowed to stand, no precipitation occurred, and colorless, transparent and uniform. A solution was obtained. However, the coating film obtained by forced drying and curing at 150 ° C. showed efflorescence over time and no effect was seen.

Example 4 As in Example 1, when 100 g of No. 3 water glass was mixed with 50 g of a 10% solution of sodium dihydrogen phosphate, a partially transparent gel-like mamako was produced. A slightly viscous and highly transparent solution was formed, and Example 1
It showed the same physical properties as. When 100 g of No. 3 water glass was mixed with 150 g of a 5% aqueous solution of sodium dihydrogen phosphate, the entire system solidified into a translucent gel, but when 100 g of a 5% aqueous solution was mixed, the colorless transparency was low. A viscous solution was formed, and a glassy coating film excellent in efflorescence resistance and water resistance, which was exactly the same as in Example 1, was obtained.

[0028]

INDUSTRIAL APPLICABILITY The low temperature curable composition of the present invention can improve the lack of water resistance and the efflorescence phenomenon due to carbon dioxide absorption, which are the greatest drawbacks of water glass. As a characteristic of paints, it is possible to form a glassy or enamel-like coating film having excellent weather resistance, antistatic properties, flame resistance, antifog properties, and scratch resistance that cannot be obtained with organic paints. Since water is used as the medium, it has excellent pollution-free and workability. Therefore, the surface of wood, various metals, concrete, mortar, asbestos, slate, natural stone, glass, gypsum, etc. can be coated with a vitreous or enamel-like hard coating film. In particular, it can be used as an anticorrosion method for steel plates, steel frames, iron parts, etc., improvement of scratch resistance, acid rain resistance measures for stone materials, roof tiles, concrete products, nonflammability treatment for wood and plastic corrugated paper, and abrasion resistance treatment method. It can also be used as an alkali-stain-free adhesive for paper tubes and corrugated board, and as a binder for clay, cement, asbestos, sand, incineration ash, etc. Molded products can be easily obtained and have a wide range of applications in fields such as construction and civil engineering.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C23D 5/00 C23D 5/00 K

Claims (3)

[Claims] 1. A general formula: M ₂ O.nSiO ₂ (wherein n
Is 2.0 to 3.3, M is an alkali metal, 2
The M's may be the same or different from each other. ) Is a water glass component (A) as a main component, and as a component (B) therein, potassium dihydrogen phosphate KH ₂ P dissolved in water
A transparent vitreous composition comprising O ₄ or sodium dihydrogen phosphate NaH ₂ PO ₄ which is added to and mixed with the water glass component (A) to a limit amount at which precipitation does not occur at room temperature. 2. A method for forming a glassy coating film, which comprises applying the glassy forming composition according to claim 1 to a substrate and then forcibly drying at 80 to 150 ° C. 3. A bonding method, which comprises bonding with the glass forming composition according to claim 1 and forcibly drying at 80 to 150 ° C.