JPH1134028A - Method for producing inorganic molded article - Google Patents

Abstract

(57) [Problem] To provide a method for producing an inorganic molded article excellent in releasability, in which a molded article having no foam on the surface and having a mold pattern transferred with good reproducibility can be obtained. It is an object. A SiO ₂ -Al ₂ O ₃ -based powder, alkali metal silicates filled, and an inorganic composition mainly comprising water, to the mold surface in a mold formed of a synthetic resin or rubber composition In the method for producing an inorganic molded article to be molded and formed, an aqueous wax thin film layer having a water content adjusted to 5 to 50% by weight is formed along the mold surface, and then the inorganic composition is filled in a molding die. I did it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an inorganic molded article.

[0002]

_2. Description of the Related Art An inorganic composition mainly composed of SiO ₂ —Al ₂ O ₃ powder, an alkali metal silicate and water is filled in a mold having a mold surface formed of a synthetic resin or rubber composition. Japanese Patent Application Laid-open No.
As disclosed in Japanese Patent No. 10634, a method of applying a silicone emulsion-based surfactant to a mold surface of a molding die before filling the molding with the inorganic molded product is disclosed by the present inventors. Has already been proposed by

That is, according to the method for producing an inorganic molded article, even if the mold surface is formed of a synthetic resin or rubber composition having a high repellency to the inorganic composition, the mold is not filled before the inorganic composition is filled. Since the surface is coated with a silicone emulsion surfactant in advance, the compatibility between the inorganic composition and the mold surface is improved, and there is no foam on the surface, and a molded body with a mold pattern transferred with good reproducibility is obtained. Can be.

[0004] However, in the above-mentioned production method, there is a possibility that the compatibility between the inorganic composition and the mold surface is excessively improved and a problem occurs in the releasability.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can provide a molded article having no foam on its surface and having a mold pattern transferred with good reproducibility, and having a high mold release property. An object of the present invention is to provide a method for producing an excellent inorganic molded article.

[0006]

Means for Solving the Problems The method for producing an inorganic molded article according to the present invention is intended to achieve such an object.
An inorganic material formed by filling an inorganic composition mainly composed of SiO ₂ —Al ₂ O ₃ powder, an alkali metal silicate and water into a mold whose mold surface is formed of a synthetic resin or rubber composition. In the method for producing a molded article, the water content is 5 to 50.
After forming the aqueous wax thin film layer adjusted to the weight% along the mold surface, the mold was filled with the inorganic composition.

The aqueous wax forming the aqueous wax thin film layer is not particularly limited, but includes, for example, animal waxes such as beeswax and wool wax; plant waxes such as carnauba wax and candeli wax;
Mineral waxes such as paraffin and microcrystalline; olefins such as polyethylene; hydrocarbons obtained by Fischer-Tropsch synthesis; chemically modified hydrocarbon waxes such as ethylene polymer and polyol ether-ester; synthesis of substituted amide waxes Examples thereof include those in which wax is dispersed in water using a surfactant, and these are used alone or as a mixture.

The method of forming the aqueous wax thin film layer is not particularly limited, and examples thereof include brush coating, spray coating, roller coating and the like. As the application amount,
It is preferably from 5 to 200 g / m ^{2 in} terms of solid content. That is, if the coating amount is less than 5 g / m ^{2 in} terms of solid content, the releasability is reduced, and if it exceeds 200 g / m ² , the wax may adhere to the surface of the molded product and the hardness may be reduced.

The water content is limited to 5 to 50% by weight,
-40% by weight is more preferred. That is, when the water content is less than 5% by weight, the conformation of the inorganic composition to the mold surface is reduced, and bubbles are easily generated. When the water content exceeds 50% by weight, the inorganic composition is mixed with the aqueous wax. The releasability decreases. The method for adjusting the water content is not particularly limited, and examples thereof include a method of air-drying the aqueous wax and a method of heating.

The synthetic resin forming the mold surface is not particularly limited. For example, olefin resins such as polyethylene and polypropylene, ABS resins, vinyl chloride resins, acrylic resins, epoxy resins, and fiber-reinforced products of polyester and epoxy resins (FRP) and the like. The rubber composition forming the mold surface is not particularly limited,
For example, urethane rubber, silicone rubber, nitrile rubber (NBR), butyl rubber, ethylene-propylene rubber (EPDM), fluorine rubber and the like can be mentioned.

The mold may be formed not only by the mold surface but also by the entire mold made of the above synthetic resin or rubber composition.

As the SiO ₂ —Al ₂ O ₃ powder, SiO ₂ : Al ₂ O ₃ = 1: 9 to 9: 1 (weight ratio)
And the powder as a whole is SiO
It is desirable that the total content of ₂ and Al ₂ O ₃ be 50% by weight or more. That is, if the content is less than 50% by weight, the reactivity with the aqueous alkali metal silicate solution is reduced, and the strength of the obtained moisture absorbing / releasing layer may be reduced.

Examples of such SiO ₂ —Al ₂ O ₃ based powders include the following, which can be used alone or in combination. Fly ash containing 80% by weight or more of particles having a particle size of 10 μm or less. Decolorized fly ash containing 80% by weight or more of particles having a particle size of 10 μm or less. An inorganic powder obtained by melting fly ash or clay and spraying it into a gas. An inorganic powder obtained by applying mechanical energy of 0.1 to 30 kwh / kg to clay. Inorganic powder obtained by further heating the powder at 100 to 750 ° C. An inorganic powder obtained by applying a mechanical energy of 0.1 to 30 kwh / kg to metakaolin. Ash from electric precipitators when producing corundum or mullite. Crushed calcined bauxite. Metakaolin.

Incidentally, ordinary fly ash is defined in JIS.
A The fine ash particles collected by a dust collector from a pulverized coal combustion boiler specified in A6201 have a SiO ₂ content of 40% or more, a moisture content of 1% or less, a specific gravity of 1.95 or more, and a specific surface area of 270.
It passes through a standard sieve of 0 cm ² / g or more and 44 μm or more by 75% or more. Then, fly ash is a method of classifying this normal fly ash using a commonly used classifier such as wet sedimentation classification, air classification, specific gravity separation, and fine milling such as a jet mill, a roll mill, and a ball mill. It can be obtained by processing by a conventionally known method such as a method of pulverizing also using a mill, a method of using a continuous system of a classifier and a pulverizer, and the like.

The reason why the particles having a particle size of 10 μm or less must be contained in an amount of 80% by weight or more, such as fly ash, is that if the amount of the fly ash having a particle size of 10 μm or less is less than 80% by weight, alkali metal silicate This is because the reactivity with the salt aqueous solution is reduced, and there is a possibility that the strength is reduced or curing failure is caused.

The decolorized fly ash is obtained by baking fly ash at 400 to 1000 ° C. or baking ordinary fly ash at 400 to 1000 ° C.
Can be obtained in the same manner as fly ash.
That is, fly ash is generally black, and if this black fly ash is fired at a temperature of 400 ° C. or higher as described above, it can be decolorized. However, when firing at a temperature exceeding 1000 ° C., the reactivity with the aqueous solution of the alkali metal silicate decreases, so firing at the above temperature range is desirable.

The inorganic powder is obtained by melting fly ash or clay and spraying it in a gas.
As a method of melting and spraying in a gas, a spraying technique applied to a ceramic coating, preferably a spraying technique in which the fly ash and clay are melted at a temperature of 2000 to 16000 ° C and sprayed at a speed of 30 to 80 m / s. ,
Specifically, a plasma spraying method, a high energy gas spraying method, an arc spraying method, and the like can be given.

The specific surface area of the inorganic powder obtained by the above-mentioned thermal spraying technique is generally controlled to 0.1 to 60 m ² / g.

The above-mentioned inorganic powder and the clay used as a raw material of the inorganic powder include SiO ₂ as a chemical composition;
Clay containing 5 to 85% by weight, Al ₂ O ₃ ; 90 to 10% by weight, for example, kaolinite, dickite, nacrite, kaolin minerals such as halloysite, muscovite, illite, fengite, sea chlorite, celadonite, Mica clay minerals such as paragonite and branmarite, montmorillonite, beidellite, nontronite, sabonite,
Examples include smectites such as sauconite, chlorite, pyrophyllite, talc, and sand shale.

The mechanical energy used in the production of the inorganic powder (1) means a compressive force, a shearing force, and an impact force, which may be used alone or in combination of two or more. . Examples of the equipment for making these act specifically include a ball mill, a vibration mill, a planetary mill, a medium stirring type mill, a roller mill, a mortar, and a jet powder crusher.

The particle diameters of the clay and metakaolin used in the production of the above inorganic powders are not particularly limited.
The average particle diameter is preferably from 0.01 to 500 μm, more preferably from 0.1 to 500 μm, in order to effectively exert mechanical energy.
It is preferably from 1 to 500 μm, particularly preferably from 0.1 to 1 μm.
00 μm.

If the mechanical energy applied during the production of the inorganic powder is less than 0.1 kwh / kg, the reactivity of the obtained inorganic powder with the aqueous alkali metal silicate solution is reduced, and If it exceeds, the load on the above-mentioned crushing device increases, and the wear and damage of the device increase,
Since problems such as impurities to the above-mentioned clay occur, 0.1 to
Limited to 30 kwh / kg, preferably 1.0 to 26
Act at kwh / kg.

The reason why the mechanical energy applied to metakaolin is limited to 0.1 to 30 kWh / kg is the same as in the above cases. When applying mechanical energy, a grinding aid may be added as necessary.

The pulverizing auxiliary agent prevents the powder of clay or metakaolin from adhering to the inside of the device or remarkably agglomerating when mechanical energy is applied. For example, alcohols such as methyl alcohol and ethyl alcohol; Alcohol amines such as triethanolamine; metal soaps such as sodium stearate and calcium stearate; and acetone vapor. These can be used alone or 2
More than one species may be used in combination.

The inorganic powder is obtained by applying steam mechanical energy to the clay and then heating the clay to 100 to 750 ° C., because the mechanical strength is improved by heating. When the heating temperature is less than 100 ° C,
No improvement in strength is observed. When the temperature exceeds 750 ° C, crystallization of the inorganic powder occurs, and the reactivity with the aqueous alkali metal silicate solution is reduced. Therefore, the temperature is limited to 100 to 750 ° C, and preferably limited to 200 to 600 ° C. Is done. Also,
When the heating time is short, the improvement of the mechanical strength of the obtained molded body is small, and when the heating time is long, the energy cost increases, so 1 minute to 5 hours is preferable.

And the inorganic powders described in JP-B-3-9
060 and Japanese Patent Publication No. 4-45471. The commercially available metakaolin can be used.

The alkali metal silicate used in the present invention is a silicate represented by M ₂ O.nSiO ₂ (at least one metal selected from M = K, Na and Li). When the value is small, a molded article having a good appearance cannot be obtained, and when the value is large, gelation is likely to occur.
~ 8, more preferably 0.5 ~ 2.5.

The alkali metal silicate is preferably added in the form of an aqueous solution. Further, when the aqueous solution is used, when the concentration is low, the reactivity with the SiO ₂ —Al ₂ O ₃ powder is reduced, and when the concentration is high, the alkali metal salt is easily formed. %, More preferably 10 to 60% by weight. That is,
When the concentration is lower than 10% by weight, the strength of the obtained molded body is reduced. When the concentration is higher than 70% by weight, the viscosity of the alkali metal silicate aqueous solution is increased, and the workability during mixing and molding is reduced. There is fear.

The aqueous alkali metal silicate solution may be prepared by dissolving the alkali metal silicate in water as it is under pressure and heating.
The iO ₂ component may be dissolved under pressure and heat so that n becomes a predetermined amount, or a commercially available aqueous solution of an alkali metal silicate is used after being adjusted to a predetermined composition with a metal hydroxide and water. You may.

The addition amount of the alkali metal silicate is SiO ₂ −
The amount is preferably 1 to 300 parts by weight (10 to 1300 parts by weight as an aqueous solution) based on 100 parts by weight of the Al ₂ O ₃ powder.
0 to 250 parts by weight (10 to 1000 parts by weight as an aqueous solution) is more preferable. That is, if the addition amount is too large, cracks and the like may be generated in the obtained molded body.

The water used in the present invention may be added in a total amount as an aqueous solution of an alkali metal silicate, or may be added in the form of both an aqueous solution of an alkali metal silicate and independent water. . If the amount of water is too small, it will not cure sufficiently, and if it is too large, the strength of the moisture absorbing / releasing layer will decrease.
10 to 10 parts by weight of SiO ₂ —Al ₂ O ₃ powder
1000 parts by weight, preferably 10 to 750 parts by weight, more preferably 50 to 500 parts by weight.

In the inorganic composition of the present invention, if necessary, an inorganic filler, a reinforcing fiber, a lightweight aggregate, a pigment,
A foaming agent, a foaming aid, a foaming agent and the like can be added.

As the inorganic filler, rock powder, volcanic ash (silas, anti-firestone, etc.), wollastonite, calcium carbonate, silica stone powder, mica, mica, silica fume and the like can be used. The amount _is preferably 900 parts by weight or less with respect to SiO 2 -Al ₂ O ₃ -based powder 100 parts by weight. If the amount exceeds 900 parts by weight, the mechanical strength may be reduced.

As the reinforcing fibers, those used in ordinary cement products can be used, and polypropylene, vinylon, rayon, alkali-resistant glass, carbon, acrylic,
Fibers such as aramid and acrylonitrile can be used alone or in combination. Fiber diameter is 1 ~ 500μ
m and a fiber length of 1 to 15 mm are desirable. That is, if the fiber diameter is less than 1 μm, a fiber ball is formed during mixing,
When the strength exceeds 500 μm or the fiber length is less than 1 mm, a reinforcing effect such as improvement in tensile strength cannot be expected. On the other hand, if the fiber length exceeds 15 mm, the dispersibility decreases, and a molded article having uniform strength cannot be obtained.

As the amount of the reinforcing fiber, SiO ₂ -A
It is desirable that the content be 10 parts by weight or less based on 100 parts by weight of the l ₂ O ₃ -based powder. If it exceeds 10 parts by weight, the dispersibility of the fiber may be reduced.

As the lightweight aggregate, inorganic foams such as pearlite, glass balloon, silica balloon, fly ash balloon and shirasu foam, and organic foams such as phenol resin, urethane resin, polyethylene and polystyrene can be used. The amount of the lightweight aggregate added is SiO ₂ −
It is desirable that the amount be 150 parts by weight or less based on 100 parts by weight of the Al ₂ O ₃ -based powder. If the amount exceeds 150 parts by weight, there is a possibility that the strength, surface smoothness or molding workability may be reduced.

As the pigment, metal oxide pigments such as iron oxide, titanium oxide and cobalt oxide and carbon black are desirable. The addition amount of the pigment with _respect to SiO 2 -Al ₂ O ₃ -based powder 100 parts by weight or less is preferable 50 parts by weight.
Even if it exceeds 50 parts by weight, the hiding power is not improved and it is uneconomical.

As the foaming agent, Mg, Ca, Cr, M
n, Fe, Co, Ni, Cu, Zn, Al, Ga, S
n, Si, metal powders such as ferrosilicon, hydrogen peroxide water or sodium peroxide, potassium peroxide, peroxide powders such as sodium perborate, and the like, cost, safety,
Considering availability and ease of mixing, Al and hydrogen peroxide are preferred.

The foaming agent powder preferably has a particle diameter of 1 to 200 μm. That is, if the particle diameter is smaller than 1 μm, the dispersibility is reduced, and rapid foaming is caused. If the particle diameter is larger than 200 μm, the reactivity may be reduced. The addition amount of the foaming agent (solution 100% basis), compared SiO ₂ -Al ₂ O ₃ -based powder 100 parts by weight or less is preferable 5 parts by weight. That is, if the amount exceeds 5 parts by weight, the strength is remarkably reduced, and it becomes impossible to handle the molded body.

As foaming agents, higher alcohol sulfates, alkyl ether sulfates, aromatic derivative sulfonates, imidazoline derivatives, fatty acid amides,
Animal protein systems can be used. The addition amount of the foaming _agent, to SiO 2 -Al ₂ O ₃ -based powder 100 parts by weight of 1
0 parts by weight or less is desirable. If the amount is more than 10 parts by weight, poor curing tends to occur.

Examples of the foaming aid include porous powders such as silica gel, zeolite, activated carbon, and alumina gel, and metal soaps such as metal stearate and metal palmitate. As the amount of the foaming aid, SiO ₂ —Al
_It is desirable that the amount be 10 parts by weight or less based on 100 parts by weight of the ₂ O ₃ powder. If the amount is more than 10 parts by weight, there is a possibility that bubbles may be broken.

In order to obtain the above-mentioned inorganic composition by mixing, an ordinary mixer such as a paddle rotary mixer, an oscillating mixer or a screw mixer can be used. As a mixing method, a powder raw material is dry-mixed, and an alkali metal silicate aqueous solution is further added to the obtained mixture and mixed, a method of simultaneously supplying and mixing all the raw materials, an alkali metal silicate aqueous solution And a method in which a part of the raw material is mixed, and the remaining raw materials are sequentially added and mixed.

When a foaming agent is used, it is advantageous to mix the foaming agent at the end of the mixing step in terms of workability and stability of bubbles. If a foaming agent is used, add the foaming agent last or make a slurry with raw materials other than the foaming agent,
A method of mixing with an aqueous solution in which bubbles are generated by a foaming agent and water is preferable. Foaming agent concentration when used as an aqueous solution
1-5% is desirable. If it is less than 0.1%, the stability of the foam is inferior and the foam breaks, and if it is more than 5%, poor curing occurs.

The filling of the slurry of the inorganic composition into the mold may be carried out by a free-fall method or may be carried out forcibly by a pump or the like. Vibration may be applied during or after filling the slurry for leveling or defoaming the slurry. When the viscosity of the slurry is high, press molding may be performed.

As for the conditions for curing the inorganic composition, it is preferable to carry out the treatment while maintaining the ambient temperature between room temperature and 100 ° C. for 5 minutes to 12 hours. The heating method is not particularly limited,
For example, an oven is mentioned. It goes without saying that the higher the heating temperature, the shorter the curing time. When the heat curing is completed, the mold is released.

[0046]

Embodiments of the present invention will be described below in detail. In the method for producing an inorganic molded article of the present invention, a mold having a mold surface formed of a synthetic resin or a rubber composition is prepared, an aqueous wax is applied to the mold surface of the mold, and then air-dried to reduce the water content. The aqueous wax thin film layer is formed by adjusting the amount to 5 to 50% by weight.

Next, SiO ₂ —Al ₂ O ₃
The inorganic powder is filled with an inorganic composition mainly composed of a base powder, an alkali metal silicate and water, and the inorganic composition is molded so as to conform to the shape of the molding die. A molded article is obtained.

That is, according to this manufacturing method, when the inorganic composition is filled in a mold and molded, the aqueous wax thin film layer whose water content has been previously adjusted to 5 to 50% by weight is formed along the mold surface. Since it is provided, repulsion of the inorganic composition on the mold surface is reduced, and no air bubbles are generated between the inorganic composition and the mold surface. Also, it has excellent releasability. Therefore, it is possible to stably obtain a molded body having no bubbles on the surface and having a pattern pattern transferred with good reproducibility.

[0049]

Embodiments of the present invention will be described below in more detail. First, following SiO ₂ -Al ₂ O ₃ -based powder A, B,
Alkali metal silicate aqueous solutions I and II, aqueous wax 1
4. Molds 1 to 4 were prepared.

[SiO ₂ -Al ₂ O ₃ -based powder A] Metakaolin (manufactured by Engelhart, trade name: SATENTO)
NE SP33, average particle size 3.3 μm, BET specific surface area: 5.8 cm ² / g)

[SiO ₂ -Al ₂ O ₃ -based powder B] Metakaolin (manufactured by Engelhardt, trade name: SATENTO)
NE SP33, average particle size 3.3 μm, BET specific surface area: 5.8 cm ² / g) 100 parts by weight and 0.5 part by weight of a mixed solution of 25% by weight of triethanolamine and 75% by weight of ethanol were added to an Ultra Fine Mill ( (Zirconia balls 10 mm, manufactured by Mitsubishi Heavy Industries, Ltd., ball filling rate: 85% by volume), and obtained by applying a mechanical energy of 10 kwh / kg. The applied mechanical energy was expressed by dividing the electric power supplied to the ultrafine mill by the unit weight of the treated powder.

[Alkali metal silicate aqueous solution I] JIS
No. 1 aqueous solution of sodium silicate (manufactured by Nippon Chemical Industry Co., Ltd.) and sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed with SiO ₂ / Na ₂
(Molar ratio) = 0.8 and the concentration was adjusted to 38%.

[Alkali Metal Silicate Aqueous Solution II] A 1K aqueous solution of potassium silicate (manufactured by Nippon Chemical Industry Co., Ltd.) and potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed with SiO ₂ / K ₂ (molar ratio) =
1.4 and a concentration of 42%.

[Water-based wax 1] PD-
191N (wax component: polyethylene, concentration 35% by weight) [Water-based wax 2] EM-01 (wax component: microcrostalin, concentration 29% by weight) manufactured by Oil & Fat Products Co., Ltd.

[Water-based wax 3] PSK, manufactured by Fat & Oil Products Co., Ltd.
-80 (wax component: polyolefin + microcrostalin, concentration 25% by weight) [Water-based wax 4] E-43N (oil component: polypropylene, concentration 30% by weight) manufactured by Yushi Products Co., Ltd.

[Mold 1] As shown in FIGS. 1 and 2, the mold 2 is formed of silicone rubber, and a reinforcing iron plate 3 having a thickness of 3 mm is integrally provided along the bottom of the mold 1. A mold having the following dimensions. _{L 1, L 2, L 5} , L 6, L 8, L 9, L 13, L 14, L
₁₇ , L ₁₈ , L ₂₀ = 5 mm L ₃ , L ₇ , L ₁₀ , L ₁₂ = 150 mm L ₄ , L ₁₁ , L ₁₆ = 10 mm L ₁₅ , L ₂₁ = 330 mm L ₁₉ = 20 mm

[Mold 2] A mold similar to mold 1 except that mold body 2 is formed of butyl rubber. [Mold 3] A mold similar to mold 1 except that mold body 2 was formed of ethylene-propylene rubber.

[Mold 4] A mold similar to mold 1 except that mold body 2 is formed of polypropylene.

(Example 1) 20% by weight of the mold 1
Aqueous wax 1 adjusted to a concentration of 20 g / m ² , spray-dried, and then air-dried to a water content of 8% by weight.
To form a water-based wax layer. This mold 1
Then, 100 parts by weight of the SiO ₂ —Al ₂ O ₃ -based powder A and 35 parts by weight of an aqueous solution of an alkali metal silicate I were charged into an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) and mixed for 2 minutes to obtain a slurry. The inorganic composition was introduced by gravity and cured at 85 ° C. for 4 hours to obtain a molded product.

(Example 2) 20% by weight of the mold 2
Was applied at a coating amount of 60 g / m ² and then air-dried to form an aqueous wax layer having a water content adjusted to 21% by weight.

The above-mentioned SiO ₂ —Al ₂ O
100 parts by weight of ₃ series powder A and aqueous solution of alkali metal silicate I
70 parts by weight and silica sand (Haya Kasei Co., Ltd., Flatary Sand 4
8M) 150 parts by weight into an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.), and the slurry-like inorganic composition obtained by mixing for 2 minutes is dropped by gravity and cured at 85 ° C. for 4 hours to cure and form. I got a body.

(Example 3) 20% by weight of the mold surface of the mold 3
Was spray-coated at a coating amount of 170 g / m ² and air-dried to form an aqueous wax layer having a water content adjusted to 32% by weight.

The above-described SiO ₂ —Al ₂ O
100 parts by weight of powder ₃ system B and aqueous solution of alkali metal silicate I
100 parts by weight of I45 and 100 parts by weight of silica sand (manufactured by Hayashi Kasei Co., Ltd., Flatary Sand 48M) were charged into an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) and mixed for 2 minutes to obtain a slurry-like inorganic composition. It was thrown in and dropped and cured at 85 ° C. for 4 hours to obtain a molded article.

(Example 4) 20% by weight of the mold 4
Aqueous wax 4 adjusted to a concentration of 50 g / m ² was spray-coated and then air-dried to a water content of 15% by weight.
To form a water-based wax layer. This mold 4
Then, 100 parts by weight of the SiO ₂ —Al ₂ O ₃ -based powder B and 25 parts by weight of an aqueous solution of an alkali metal silicate II were charged into an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) and mixed for 2 minutes to obtain a slurry. The inorganic composition was introduced by gravity and cured at 85 ° C. for 4 hours to obtain a molded product.

(Example 5) 20% by weight of the mold 2
Was applied at a coating amount of 80 g / m ² and then air-dried to form an aqueous wax layer having a water content adjusted to 21% by weight. This mold 2
Then, 100 parts by weight of the SiO ₂ —Al ₂ O ₃ -based powder A and 35 parts by weight of an aqueous solution of an alkali metal silicate I were charged into an omni mixer (manufactured by Chiyoda Giken Kogyo Co., Ltd.) and mixed for 2 minutes to obtain a slurry. The inorganic composition was introduced by gravity and cured at 85 ° C. for 4 hours to obtain a molded product.

Comparative Example 1 A molded product was obtained in the same manner as in Example 1 except that the water content was changed to 2% by weight. (Comparative Example 2) A molded article was obtained in the same manner as in Example 3 except that the water content was changed to 65% by weight.

Comparative Example 3 A molded product was obtained in the same manner as in Example 2 except that the aqueous wax layer was not formed. The molded products obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were checked for mold releasability and presence or absence of air bubbles on the surface of the molded product. The results are shown in Table 1.

The above Examples 1 to 5 and Comparative Examples 1 to 5
In 3, the solid content application amount and the water content were prepared by preparing two same molds, applying the aqueous wax in parallel, adjusting the water content, using one mold for molding, and using the other mold for molding. It was measured by drying at 105 ° C.

[0069]

[Table 1]

Table 1 clearly shows that the production method of the present invention has good mold release properties and excellent moldability.

[0071]

As described above, the method for producing an inorganic molded article according to the present invention has no bubbles on the surface, and a molded article on which a mold pattern is transferred with good reproducibility can be obtained. In addition, it has excellent release properties.

[Brief description of the drawings]

FIG. 1 is a plan view of a molding die used in an example.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mold 20 Mold main body 30 Reinforced iron plate

Claims (1)

[Claims] 1. An inorganic composition mainly composed of SiO ₂ —Al ₂ O ₃ powder, an alkali metal silicate and water is filled in a mold whose mold surface is formed of a synthetic resin or rubber composition. Forming a water-based wax thin film layer having a water content adjusted to 5 to 50% by weight along the mold surface, and then filling the molding composition with the inorganic composition. A method for producing an inorganic molded article, characterized in that: