JPH08188442A - Low temperature curing composition and formation of glassy coating membrane - Google Patents

Abstract

PURPOSE: To obtain a low temperature curing composition and a coating membrane therefrom having excellent water proof properties and excellent in efflorescent properties (hardly developing a white blooming phenomenon by carbon dioxide gas) by using a water soluble alkali metal silicate. CONSTITUTION: This low temperature curing composition is obtained by blending (A) a water glass expressed by M2 O.nSiO2 (n=2.0-4.1, M is an alkali metal such as singly Na or K, or a mixed system with Li) with (B) a sol solution obtained by diluting an alcoholic silica sol solution, obtained by mixing alkoxysilanes with water in the presence of a catalyst consisting of an inorganic strong acid or an organic strong acid, hydrolyzing it and conducting a polycondensation reaction thereto, further diluting the blended mixture with water so as not to cause a precipitation or a gelation upon blending with the above water glass solution.

Description

Detailed Description of the Invention

[0001]

This invention relates to low temperature curable compositions, especially water resistant alkali metal silicates known as water glasses, while having a strong bond to the substrate. And a low-temperature curable composition for forming a glassy coating film having a markedly improved high gloss, colorless transparency, and high hardness.

[0002]

2. Description of the Related Art Conventionally, water-soluble alkali metal silicate, which is known as water glass, forms a highly hard glassy coating film which is excellent in adhesion and film-forming property when dried, so that it is an inexpensive inorganic paint. 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 and the coating film becomes white, so effloresce.
nce white flower phenomenon), which has the drawback of significantly impairing the appearance.

In order to deal with these problems, conventionally, the surface of a dry coating film of water glass is neutralized with acetic acid, phosphoric acid, dilute nitric acid or the like, or an aqueous solution of ammonium salt is brought into contact with the coating surface. There have been various proposals, but the coating film surface is easily damaged due to cracks and peeling, and there is a problem in workability and performance such as requiring 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, which are polysaccharides, have been tried, but when these curing agents are used, rapid gelation occurs. Has a problem in workability, becomes opaque and has poor gloss when mixed with a curing agent, and is not practical for a glassy coating for the purpose of beauty.

Further, it has been attempted to heat-treat water glass. However, the temperature at which water glass becomes insoluble depends on the molar ratio and is widely used from the economical aspect (JIS standard K1408) No. 3 water glass.
It is necessary to heat to 70 ° C or higher (450 ° C or higher for complete insolubilization), but foaming occurs at the stage of heating to 110 ° C, and the coating film produces many pinholes. There is a problem that the coating film is destroyed due to remarkable foaming and loss of transparency.

[0007]

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, it solves the drawbacks of water glass, such as poor water resistance and white flower phenomenon due to carbon dioxide in the air, and has excellent workability, nonflammability, water resistance, and high hardness with good adhesion and good adhesion. Another object of the present invention is to provide a low-temperature curable composition capable of forming the glassy coating film on the surface of various materials at a relatively low temperature.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies on materials capable of solving the drawbacks of water glass and imparting a glassy coating film to various materials at low temperatures. In the presence of a mixture of alkoxysilanes such as tetraethoxysilane and methyl silicate 51 with water, hydrolysis and polycondensation while stirring, a homogeneous transparent sol solution is obtained when this is further diluted with water. Unexpectedly, alkali metal sodium silicate represented by No. 3 water glass defined in JIS K1404 and lithium silicate having a molar ratio of 4.5 (lithium water glass) without causing precipitates unexpectedly. And the composition mixed with water glass is dried and hardened relatively quickly when coated on a glass plate or the like and naturally dried, and the adhesion is impaired. It was discovered that a coating film with high transparency and high hardness could be formed, and surprisingly, the heat resistance at the relatively low temperature up to 200 ° C for a few minutes was the greatest drawback of water glass. They found that the lack of sex and efflorescence were significantly improved, and completed the present invention.

That is, the present invention provides (1) the general formula: M ₂
O · nSiO ₂ (n = 2.0 to 4.1, M is an alkali metal, Na or K alone or in a mixed system with Li) is a water glass (A) as a main component, and this is combined with alkoxy. The alcoholic silica sol solution obtained by mixing silanes with water using an inorganic strong acid or an organic strong acid as a catalyst and hydrolyzing and polycondensing the mixture is further added with water to such an extent that precipitation or gelation does not occur when mixed with the water glass. A low temperature curable composition characterized by being mixed with a diluted sol solution (B), and (2) a low temperature curable composition according to item (1) is applied to various substrates, Then, the present invention provides a method for forming a water-resistant glassy coating film, which comprises performing forced drying at 60 to 200 ° C.

In the present invention, the water glass of the component (A) as a main component has a general formula: M ₂ O.nSiO ₂ (n is 2.0).
To 4.1), a commercially available water glass composed of sodium silicate or potassium silicate is used alone, or more preferably, JIS standard No. 3 water glass has a molar ratio of 4.5 to lithium silicate. Aqueous solution (lithium water glass)
Of 10 to 50% by weight, or even JIS
A mixture of JIS No. 4 soda water glass and JIS No. 4 soda water glass in a proportion of 50 to 90% by weight can be used.

The alkoxysilanes used for preparing the sol solution of the component (B) of the present invention include tetrafunctional tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, and trimethoxymethyl. Examples include trifunctional trialkoxyalkylsilanes such as silane and triethoxymethylsilane. Further, partially hydrolyzed oligomeric alkoxysilanes such as ethyl silicate 40 and methyl silicate 51 provided as industrial products are more preferably used.

In preparing the sol solution of the component (B) of the present invention, first, the above alkoxysilanes are mixed with water and hydrolyzed and polycondensed in the presence of an acid catalyst to obtain uniform transparency. An alcoholic silica sol solution is obtained. Here, the amount of water can be appropriately determined, but the weight ratio of the alkoxysilanes and water is usually 8/2 to 4/6. If too much is used, then water is added afterwards. In addition, even if diluted, it is difficult to obtain a stable sol solution. Also,
As the acid catalyst, an inorganic strong acid such as hydrochloric acid or nitric acid, or an organic strong acid such as p-toluenesulfonic acid is used.

Next, the above-mentioned alcoholic silica sol solution is further diluted with water to obtain a stable sol solution. The amount of water added here should be such that precipitation or gelation does not occur during mixing with water glass. This amount depends on the type of alkoxysilanes, the concentration of acid catalyst, and the like. Although it may vary depending on the type and the like and cannot be determined unconditionally, it is generally preferable that the dilution amount is four times or more.

In the present invention, the low temperature curable composition is prepared by uniformly mixing the stable sol solution (B) prepared as described above with the water glass (A).
At that time, the mixing ratio of the water glass and the sol solution is such that the precipitation or gelation does not occur, usually the weight ratio of the water glass and the raw material composed of the alkoxysilanes constituting the sol solution is On the other hand, the latter ratio is preferably set to 1/8 to 1/16. The low temperature curable composition of the present invention thus obtained, if necessary, silica, alumina,
Filler powder such as talc and pigments may be blended.

In the present invention, the above-mentioned low temperature curable composition is applied to a substrate by a usual coating method such as dip coating, spray gun, roller coating, doctor knife, brush coating, and iron coating, and then dried. By doing
A glassy coating film is formed. As the base material,
Materials made of various materials such as wood, various metals, concrete, mortar, asbestos, slate, natural stone, glass and gypsum can be applied. The drying may be natural drying, but is preferably 60 to 200 ° C., particularly 120 to
It is preferable to perform forced drying at 150 ° C., which makes it possible to form a coating film having excellent water resistance and free from the phenomenon of white bloom due to carbon dioxide in the air.

The coating film thus formed is
It is a glass-like coating film that has excellent adhesion to the substrate, weather resistance, flame resistance, high gloss, etc., and has a very high Knoop hardness of 300 to 400 as measured by a micro hardness meter. It has the characteristic that it cures at such a low temperature and becomes excellent in water resistance and efflorescence resistance, which was not possible with conventional water glass paints.

Further, the low-temperature curable composition of the present invention is used for the impregnation of wood, stone, gypsum, cement, asbestos, etc., and various aggregates such as clay, stone powder and glass powder, in addition to the formation of the above-mentioned coating film. It can also be used as a binder for particles. In this case, if it is cured by heating at a temperature of up to about 200 ° C. after dry molding, a water-resistant and strong glass-like cured molded article can be obtained, which can be used for various purposes such as construction and civil engineering.

[0018]

EXAMPLES Next, the present invention will be described more specifically based on production examples, examples and comparative examples, but the present invention is not limited to these examples.

Production Example 1 25 g of methyl silicate 51 (manufactured by Mitsubishi Kasei) and 25 parts of water
g and 0.1 ml of hydrochloric acid of 0.1N are mixed with a magnetic stirrer for about 150 minutes at room temperature. Methyl silicate 51, which was initially dispersed in the form of oil droplets, is hydrolyzed and polycondensed, and is colorless and transparent. A different alcoholic silica sol solution was formed. (Note that this alcoholic silica sol solution was stable at pH 5 for about 1 week, and then solidified into a gel.) Next, this alcoholic silica sol solution was further diluted 4 to 8 times with water and mixed with water glass. The sol solution was used for mixing.

Production Example 2 In Production Example 1, the amount of 0.1N hydrochloric acid used as an acid catalyst was increased by 10 times to 10 ml, and methyl silicate 51 was added.
When 25 g of the above was mixed with 14 g of water and similarly stirred at room temperature with a magnetic stirrer, a colorless and transparent alcoholic silica sol solution was formed in 70 to 80 minutes. Next, this alcoholic silica sol solution was diluted 5 times with water to obtain a sol solution. PH of this 5-fold diluted sol solution
The value was 2.4, which was stable for about 10 days, but then became a gel.

Production Example 3 In Production Example 1, the mixing ratio of methyl silicate 51 and water was changed to 7/3. That is, methyl silicate 51
30 g of water and 1 ml of 0.1N hydrochloric acid were stirred for 120 minutes at room temperature to form a colorless and transparent alcoholic silica sol solution. The alcoholic silica sol solution gelled in about 12 hours. Next, this alcoholic silica sol solution was further diluted with water 4 times and 8 times to obtain a sol solution. The sol solution diluted 4 times became a gel in 24 hours, while the sol solution diluted 8 times was stable for a relatively long period of time.

Production Example 4 To 60 g of triethoxy (methyl) silane, 40 g of water and 0.
When mixed with 1 ml of 1N hydrochloric acid and stirred with a magnetic stirrer, a homogeneous transparent alcoholic silica sol solution was formed in about 30 minutes even at room temperature. The smaller the amount of water with respect to the alkoxysilane, the more stable was the alcoholic silica sol solution, and when the amount of water exceeded the equimolar amount, the phases separated into two phases over time. Next, this alcoholic silica sol solution was diluted 4-fold with water to obtain a stable sol solution.

Production Example 5 When 0.050 g of crystals of p-toluenesulfonic acid monohydrate was used as the acid catalyst in Production Example 1, 120
A colorless, transparent alcoholic silica sol solution was formed by agitating the quantiles. The produced alcoholic silica sol solution was further diluted with water 4 to 8 times to prepare a sol solution used for mixing with water glass.

Production Example 6 In the case of using tetramethoxysilane corresponding to the monomer of this in place of methyl silicate 51 in Production Example 1, uniform transparency was obtained by stirring for 2 to 4 hours without using an acid catalyst. An alcoholic silica sol was formed. When 0.1 N hydrochloric acid was used as a catalyst in the same manner as in Production Example 1, it instantly became transparent and homogenized with some heat generation, and an alcoholic silica sol solution having a pH of 2.6 was obtained. The produced alcoholic silica sol solution was further diluted 8 times with water to obtain a sol solution for mixing with water glass. The diluted sol solution gelled after 10 days.

Production Example 7 In the case of using ethyl silicate 40 (manufactured by Tama Chemical Co., Ltd.) in place of methyl silicate 51 in Production Example 1,
Even if the mixture was stirred for 48 hours or more, it could not be homogenized and it was difficult to form an alcoholic silica sol. However, when the amount of water to be mixed was halved and ethanol was added by that much, a transparent alcoholic silica sol was formed by stirring for 2-3 hours. The resulting sol was relatively stable. This alcoholic silica sol was further diluted 5 times with water and used for mixing with water glass.

Example 1 In a 300 ml Erlenmeyer flask, water glass was prepared by mixing 30 g of JIS standard No. 3 water glass (manufactured by Fuji Chemical Co., Ltd.) with 10 g of an aqueous lithium silicate solution (lithium water glass LSS-45 manufactured by Nissan Chemical Co., Ltd.). When 40 g of the 4-fold diluted sol solution prepared in the above Production Example 1 was mixed, a low-viscosity, transparent, low-temperature curable composition which was stable for a long period of time and which did not precipitate was obtained.

When the above composition is applied to the surface of a flat glass plate and naturally dried and dried by heating on a hot plate at 120 to 150 ° C. for 5 to 10 minutes, a vitreous coating film having high gloss and good adhesion is formed. It was 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, which is 0 (center diameter 25μ
Even if it was rubbed strongly with the commercially available household steel wool of m), it was not scratched at all and was excellent in scratch resistance.

The coating film formed by natural drying was also insoluble in water, but in this case the water resistance was not sufficient and the coating film peeled off when immersed in water. In the case of the coating film dried and cured at 150 ° C., no change in the surface condition was observed even when immersed in water for 1 month or more, and the water resistance, which was a drawback of the water glass coating film, was remarkably improved. In addition, the white flower phenomenon due to the absorption of carbon dioxide gas is
Some hygroscopicity and efflorescence were observed over time. However, 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., efflorescence was hardly seen.

Comparative Example 1 In Example 1, as the sol solution to be mixed with water glass, the alcoholic silica sol solution formed in Production Example 1 was used, which was diluted two times with water. In this case, when mixed with water glass, it gelled and precipitated over time to become a white opaque solid.

Example 2 By the same method as in Example 1, 40 g of water glass consisting only of No. 3 water glass was mixed with 60 g of the 4-fold diluted sol solution prepared in Production Example 1, and phase separation and precipitation were observed. There was no formation and uniform mixing was possible, and a colorless and transparent low-viscosity low-temperature curable composition was obtained. This composition is a glass plate, wood,
It was applied to an aluminum plate, a slate plate, etc., and dried by heating at 120 ° C. and cured. The formed coating film has excellent water resistance,
It had good adhesion, was colorless and transparent, and had high gloss. The hardness of the film was Knoop hardness KH = 296.

Comparative Example 2 In Example 2, as the sol solution to be mixed with water glass, 20 g of the alcoholic silica sol solution formed in Production Example 1 was diluted 3-fold instead of 4-fold. In this case, it became white and opaque, and eventually the whole solidified.

Example 3 In the same manner as in Example 1, in a 50 ml Erlenmeyer flask,
No. 3 sodium silicate 30g, lithium silicate aqueous solution 10g
When 40 g of the 5-fold diluted sol solution prepared in Production Example 2 was mixed with the water glass mixed system prepared by mixing the above, a low temperature curable composition that was homogeneously mixed and was stable for a long period of time was obtained. This product is coated on a glass plate, etc., and dried naturally and at 150 ℃
A colorless, transparent, and high-gloss coating film was obtained by drying at. The coating film obtained by drying and curing at 150 ° C. showed no change in water for a long period of time, and efflorescence hardly occurred. The Knoop hardness of the coating film is Knoop hardness KH = 51 in the case of room temperature dry hardening.
And, the Knoop hardness when dry-curing at 150 ° C is KH = 31.
In No. 6, the adhesion was good and the scratch resistance was good.

Comparative Example 3 In Example 3, the alcoholic silica sol solution formed in Production Example 2 was diluted three times with water as the sol solution to be mixed with water glass. In this case, when mixed with water glass, it gelled and became a white solidified substance over time.

Example 4 In a 300 ml Erlenmeyer flask, 20 g of No. 3 water glass and 20 g of lithium water glass LSS-45 were mixed, and the sol of 4-fold dilution of the alcoholic silica sol solution formed in the above Production Example 3 was prepared. When 10 g of the solution was mixed, a viscous colorless and transparent low-temperature curable composition was obtained.
In addition, when 20 g of a 4-fold diluted sol solution was mixed, a gel was formed. Then, the above composition was applied to a glass plate or the like, dried at room temperature and dried by heating at 120 ° C., whereby a good vitreous coating film was formed. When heat-dried and cured, it showed excellent water resistance and efflorescence resistance.

Example 5 In a 300 ml Erlenmeyer flask, 30 g of the 4-fold diluted sol solution prepared in Production Example 4 was mixed with water glass obtained by mixing 20 g of No. 3 water glass with 20 g of lithium water glass. A transparent low temperature curable composition with low viscosity was obtained without any formation. After coating on a glass plate or the like, it was naturally dried and dried by heating on a hot plate at 120 ° C. for 10 minutes, whereby a vitreous coating film having high gloss and good adhesion was formed. The water resistance was improved even when naturally dried, but the water resistance was remarkably improved by heating at 120 ° C.

Example 6 20 g of No. 3 water glass was mixed with lithium water glass (LSS-4).
4 prepared in Production Example 5 in water glass in which 20 g of 5) was mixed.
When 20 g of the double-diluted sol solution was mixed, a low-viscosity transparent low-temperature curable composition was obtained without causing precipitation. In the case of natural drying after coating on a glass plate etc., the film-forming property such as cracks and peeling was poor, but forced drying at 120 ° C gives good film-forming property, excellent water resistance, and high gloss without efflorescence. Thus, a hard (Knoop hardness KH = 316) vitreous coating film having good adhesion was formed.

Example 7 When 40 g of No. 3 water glass was mixed with 30 g of the 4-fold diluted sol solution prepared in Production Example 6, a transparent low temperature curable composition was obtained without causing precipitation. When the above composition was coated on a glass plate and naturally dried, a colorless and transparent, highly glossy coating film of good glass quality without efflorescence was formed. Knoop hardness is KH
= 58, the adhesion was also good. Knoop hardness is KH = 2 when dried and cured on a 120 ° C hot plate.
In No. 61, a highly glossy glassy coating film having good adhesion and excellent water resistance was formed, and no efflorescence was observed.

Example 8 20 g of No. 3 water glass was charged with lithium water glass (LSS-4).
5) 1 prepared in Production Example 7 in water glass mixed with 20 g
When 20 g of 0-fold diluted sol solution was mixed, a low-viscosity colorless transparent composition was obtained without causing precipitation. When coated on a glass plate and dried at room temperature, the film-forming property was rather poor and cracks and peeling were observed. However, the coating film obtained by drying and curing at 120 ° C. is a colorless, transparent and highly glossy glass material with high hardness (Knoop hardness KH = 296) without efflorescence, which is water resistant. It was excellent.

[0039]

EFFECTS OF THE INVENTION The low temperature curable composition of the present invention can improve the lack of water resistance and the white bloom phenomenon due to absorption of carbon dioxide, which are the main drawbacks of water glass. It is possible to form a glassy or enamel-like coating film with excellent weather resistance, flame resistance, and high hardness that cannot be obtained with organic paints, and because it uses water as a medium, it is excellent in pollution-free and workability. There is. 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. It can also be used as a binder for various fillers such as clay, cement, asbestos, sand, etc., and because the raw material is very inexpensive, molded products such as unfired bricks and tiles can be easily obtained, and construction, civil engineering, etc. There is a wide range of applications in the field of.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area C09D 183/06 PMU

Claims (2)

[Claims] 1. A general formula: M ₂ O.nSiO ₂ (n = 2.
0 to 4.1, M is an alkali metal, which is composed mainly of water glass (A) represented by Na, K alone or in a mixed system with Li, and alkoxysilanes with inorganic strong acid or organic strong acid. The alcoholic silica sol solution obtained by mixing with water as a catalyst and hydrolyzing / polycondensing is further diluted with water to such an extent that precipitation or gelation does not occur when mixed with the above water glass, and a sol solution (B). A low temperature curable composition characterized by being mixed. 2. A method for forming a water-resistant glassy coating film, which comprises applying the low-temperature curable composition according to claim 1 to various substrates and then forcibly drying at 60 to 200 ° C.