JPH0637336B2 - Manufacturing method of inorganic foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a foam suitable as a building material. More specifically, the present invention relates to a method for producing an inorganic foam, which contains alkali silicate as an active ingredient and is suitable as a heat insulating material and a heat insulating material having water repellency and waterproofness.

[Conventional technology and problems to be solved]

Conventionally, three types of building materials are known, mainly fiber materials such as rock wool and glass wool, plastic foams such as polyethylene and polyurethane, and inorganic foams such as foam glass.

Among them, plastic foam is excellent in performance such as low cost, low specific gravity, low thermal conductivity and good workability, but it is easily burned in case of fire and generates a lot of harmful gas, smoke and heat. It has a serious defect in fire protection.

Further, although the fiber-based heat insulating material and the inorganic foam are nonflammable, they have the drawback that they have both high water absorption and high thermal conductivity.

In particular, an inorganic foam made from a water-soluble silicate as a raw material can be supplied at a low cost, but it generally has poor water resistance and has a drawback that it is easily deteriorated when it comes into contact with carbon dioxide gas in the air.

As a water-repellent inorganic lightweight foam, there is known a production method in which a liquid modified alkali silicate is reacted with a small amount of a specific alkoxyorganosilane and the foam is heated as it is (JP-A-55-47263). However, it is still insufficient in terms of heat insulation and waterproofness.

The present inventors have previously found an inorganic foam in which the water resistance of a water-soluble silicate is improved (Japanese Patent Laid-Open No. 63-242977). Is still not enough.

[Means for Solving the Problems]

An object of the present invention is to solve the above problems and provide a non-combustible inorganic foam having high waterproofness.

As a result of diligent studies, the inventors of the present invention have found that a mixture of a water-soluble alkali silicate and a curing agent is dried at 150 ° C. or lower, and a foaming hydrated silicate having a water content of 5 to 30% by weight reacts with a reactive organosilicon. The present invention has been completed by finding that an inorganic foam obtained from a mixture containing a polymer has both high heat insulating property, water repellency and waterproof property. That is, the present invention comprises: a) a water-soluble alkali silicate partially substituted with hydrous powdered alkali silicate; b) a polyvalent metal oxide, chloride, sulfate, thiosulfate,
Hardener consisting of one or more selected from sulfite, nitrate, hydroxide, phosphate, condensed phosphate, boric acid, alkali metal borate, Portland cement, alumina cement, and above a) The mixed slurry of b) was dried at 150 ° C or lower, and the expandable hydrous silicate having a water content of 5 to 30% by weight was prefoamed to a maximum foaming ratio of 40 to 95%, and then an organic silicon polymer was blended. It is a process for producing an inorganic foam characterized by heating, reacting, and foaming.

Among alkali silicates, lithium salts have low foaming property, and sodium salts and potassium salts are preferable. Also SiO ₂ / R ₂
The molar ratio of O (R is an alkali metal) is preferably in the range of 1.0 to 5.0.

In the present invention, water-soluble alkali silicate refers to water-containing alkali silicate as well as water-containing powdered alkali silicate,
At least a portion of the aqueous solution is replaced with such powdered alkali silicate. This water-containing powdered alkali silicate is commercially available with a water content of about 20% by weight, which is easily dissolved in water by spray-drying an alkali silicate aqueous solution.
The water content of the slurry of the alcal silicate composition after mixing with the curing agent described below is adjusted, and the aqueous solution and the powder are mixed in order to reduce the evaporation amount of water in the drying step for obtaining the foamable water-containing composition. The ratio can be set appropriately.

The curing agent used in the present invention is a polyvalent metal oxide, chloride,
Sulfate, thiosulfate, sulfite, nitrate, hydroxide, phosphate, condensed phosphate, boric acid, alkali metal borate, Portland cement, alumina cement used alone or in combination of two or more To be done. Examples of polyvalent metals are magnesium, calcium, strontium, and barium.
Examples include divalent metals, trivalent metals such as boron and aluminum, and transition metals such as iron, cobalt, nickel, copper and zinc.
Especially magnesium oxide, boron oxide, calcium oxide,
Boric acid and the like are effective.

The addition amount of the curing agent depends on the curing action force of the curing agent,
2 to 20% by weight, preferably 2 to 15% by weight, based on the solid content of alkali silicate, is suitable. If it exceeds the above range, the foamability is lowered, and conversely, if it is too small, the water resistance is deteriorated.

The mixture of the alkali silicate and the curing agent is mixed into a slurry by adjusting the water content so that the solid content is 30 to 75% by weight and forming a slurry. Solid content of 30% by weight
If the amount is less than 50%, the amount of water vaporized in the next drying step is large and the energy consumption becomes large. A mixer such as a high speed disperser, a sand mill or a kneader is suitable for mixing such a slurry. The uniform slurry is stretched to a thickness of 0.5 to 5 mm and dried by heating to 150 ℃ or less, specifically 60 to 150 ℃ until the water content becomes 5 to 30% by weight, preferably 10 to 20% by weight. Thus, a foamable hydrous silicate composition can be obtained.

If the drying temperature exceeds 150 ° C, the silicate composition will foam during drying, and the desired composition will not be obtained. If the drying temperature is less than 60 ° C, the drying will be slow and it will be difficult to keep the water content below 30% by weight. Is.

When the water content is less than 5% by weight, the expansion ratio is small, and 30% by weight
If it exceeds, adhesiveness is strong and blocking occurs during storage, which is not preferable.

The effervescent hydrous silicate obtained in this manner is used after being classified into fine particles having a particle size according to the purpose of use.

A uniform foam is obtained by previously foaming such a foamable hydrous silicate to 95% or less of the maximum foaming rate. This pre-expansion is performed within the range of 40 to 95% of the maximum expansion rate. If it exceeds 95%, the fusion between silicates is weak during foam molding, and the mechanical strength of the final foam obtained is low. Also
If it is less than 40%, a uniform foam cannot be obtained.

Suitable organic silicon polymers to be added to the foamable hydrous silicate after pre-foaming are, for example, methylhydrogen polysiloxane, polyether silicone, methylphenyl silicone and the like.

The content of the organic silicon polymer is preferably 1 to 20% by weight, more preferably 5 to 10% by weight, based on the foamable hydrous silicate. If it is less than the above range, the water repellency and waterproofness are deteriorated, and if it exceeds this range, unbonded organosilicon polymer remains on the surface and cross section of the foam after heat foaming, and the heat insulating effect is reduced.

Further, inorganic hollow bodies such as ceramic balloons, glass balloons and carbon balloons may be mixed as an aggregate with the foamable hydrous silicate. Examples of ceramic balloons include alumina balloons, alumina-silica composite balloons, and glass balloons include glass balloons, shirasu balloons, cenospheres, perlite, vermiculite, and the like.

In order to make the mixing of the hydrous silicate and the inorganic hollow body uniform, a very small amount of water is added, and if necessary, an aqueous binder is added and mixed, and the foamable hydrous silicate is added to the surface of the inorganic hollow body. It is essential that the particles are evenly attached. Therefore, the particle size of the foamable hydrous silicate is preferably smaller than the particle size of the inorganic hollow body, and specifically, it is preferably 1/2 or less.

Examples of the water-based binder include sodium metasilicate, colloidal silica, sodium metaphosphate, lithium metaphosphate, glycerin, polyvinyl alcohol, polyethylene glycol, etc.
% By weight, preferably about 3 to 5% by weight.

In addition, alkali resistant glass fiber as a reinforcing material,
Fibrous substances such as potassium whisker titanate, asbestos, and aramid can be contained. The compounding amount is 1 to 30% by volume, preferably 3 to 10% by volume, based on the foamable hydrous silicate.

In this way, the organic silicon polymer is blended, and if necessary, the foamable hydrous silicate composition containing the above-mentioned aggregates, reinforcing materials, etc. is heated, and in order to carry out reactive foaming, it is filled in a molding frame and externally heated. Therefore, heating at 400 to 600 ° C. may be used, but high frequency heating is preferable.

That is, in the case of an external heating method such as an infrared heater, a burner, an electric heater, foaming starts from the outside, and the heat insulation of the foam layer hinders the internal heating, so that a long heating time is required and a uniform foam Is hard to get. On the other hand, in the high frequency heating method, uniform foaming can be obtained in a short time by internal heating. If used in combination with an external heating method, the processing time can be further shortened. The high frequency wavelength used is preferably 10 to 100 MHz. If it is less than the above range, the heating effect is small and the treatment time becomes long. If it exceeds the above range, foaming tends to be non-uniform, and partial overheating tends to cause melting of the foamable hydrosilicate. If a high frequency in this range is used, a foam can be obtained in a treatment time of 1/10 or less of the 400 ° C. external heating method.

The present invention will be described below with reference to examples and comparative examples. All compositions are by weight unless otherwise specified.

Example 1 100 parts of potassium silicate aqueous solution (SiO ₂ 20%, K ₂ O 10%, water 70%) Powder sodium silicate 100 parts (SiO ₂ 55%, Na ₂ O 25%, water 20%) Boron oxide 5 parts Above The three were stirred and mixed with a high speed disperser to form a uniform slurry, which was stretched to a thickness of 4 mm and dried at 95 ° C for 96 hours. This is ground to obtain a foamable hydrous silicate (water content 20%) classified to 10-60 mesh. Further 150-170
Heat at ℃ for 30 minutes to pre-foam about 10 to 20 times. Next, the above foamed hydrous silicate 300 parts 5% aqueous solution of sodium metasilicate 210 parts Methylhydrogen polysiloxane 20 parts The above three parts are mixed and stirred to make a uniform depth 25 mm, 300 × 300
It was put in a mm heat-resistant resin mold and foam-molded using a high-frequency heating device of 40 MHz (3 kw). The results are shown in Table 2.

Example 2 Boron oxide of Example 1 was added with an iodine adsorption amount of 150 mg · I / g ·
A foam was obtained in the same manner as in Example 1 except that 10 parts of MgO was replaced with magnesium oxide. The results are shown in Table 2.

Example 3 Example 1 except that the methylhydrogenpolysiloxane of Example 1 was replaced with 20 parts of methylphenyl silicone.
A foam was obtained in the same manner as. The results are shown in Table 2.

Example 4 The foamable hydrous silicate obtained in Example 1 was used in an amount of 150-170.
Preheated by heating at ℃ for 30 minutes, then foamed hydrosilicate 150 parts Perlite (bulk specific gravity 0.1, particle size 1.5 mm) 150 parts 5% sodium metasilicate aqueous solution 200 parts methylhydrogenpolysiloxane 20 parts above After mixing the four, they were put in the same mold and subjected to high-frequency heating at 40 MHz (3 kw) to obtain a foam. The results are shown in Table 2.

Comparative Example 1 A foamable hydrous silicate obtained with the same composition as in Example 1 was used.
Pre-foam by heating at 50-170 ° C for 30 minutes, then mix 300 parts of this foamed hydrous silicate and 200 parts of water into the same mold, and obtain a foam by high frequency heating at 40MHz (3kw). . The results are shown in Table 2.

Comparative Example 2 The foamable hydrous silicate obtained in the same composition as in Example 2 was
After pre-foaming by heating at 50-170 ° C for 30 minutes, 300 parts of this hydrous silicate and 200 parts of water are mixed and put in the same mold, and a foam is obtained by high-frequency heating at 40 MHz (3 kw). It was The results are shown in Table 2.

As shown in Table 2 above, the inorganic foam prepared by the method of the present invention is remarkably improved in water absorption and flexural strength as compared with the comparative foam which does not react with the organic silicon polymer.

[Operation of the invention]

1. In the present invention, the foamable hydrous silicate obtained from an alkali silicate and a curing agent is used in the form of granules or powder, not in liquid or slurry form. It is blended with an organic silicon polymer in liquid form or slurry form. This is because the foaming rate is very low and the heat insulating property is small when heating and foaming.

2. The organic silicon polymer used in the present invention forms a strong chemical bond with the silicate by the water, alkali content and heat contained in the effervescent hydrous silicate, so that it has long-term water repellency and waterproofness. Maintained and demonstrated. The outline of the reaction is as follows.

(I) Methylhydrogen polysiloxane Effervescent silicate end (Ii) Methylphenyl silicone When a polymer is used as the organosilicon compound, the water repellency and waterproofness of the foam are improved as compared with the case where a monomer is used.

〔The invention's effect〕

According to the present invention, a solid foamable hydrated silicate is heated and reacted with an organic silicon polymer to obtain an inorganic foam having improved heat insulation and waterproofness. This foamed molded product has a wide range of uses as a heat insulating material, and is useful as a non-combustible building material, various heat insulating and cold insulating materials.

Claims (6)

[Claims] 1. A) Water-soluble alkali silicate partially substituted with hydrous powdered alkali silicate, b) Polyvalent metal oxide, chloride, sulfate, thiosulfate,
One or more curing agents selected from sulfite, nitrate, hydroxide, phosphate, condensed phosphate, boric acid, alkali metal borate, Portland cement, and alumina cement, or more a) b ) Was mixed with the water content of 5 to 30% by weight to obtain a foamable hydrated silicate, which was obtained by drying the mixed slurry in step 1) below 150 ° C. A method for producing an inorganic foam, which comprises blending a mixture, heating, reacting, and foaming. 2. The method according to claim 1, wherein the organosilicon polymer is one kind or two or more kinds selected from methylhydrogen polysiloxane, polyether silicone and methylphenyl silicone. 3. The method according to claim 1, wherein the foamable hydrous silicate is blended with an inorganic hollow body. 4. The method according to claim 1, wherein the heating method is high frequency heating with a wavelength of 10 to 100 MHz. 5. The method according to claim 1, wherein the curing agent is one or more selected from calcium oxide, magnesium oxide, boron oxide and boric acid. 6. The method according to claim 1, wherein an aqueous solution or dispersion of an inorganic binder is added as a binder.