JP2945919B2 - Clay composite porous body and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite porous material containing clay, water glass, and fibers. More specifically, the present invention relates to an environmentally friendly composite porous material that can be used as a heat insulating material, a sound absorbing material, a packaging material, a packaging material, a cushioning material, and does not cause pollution or environmental pollution even during disposal during and after use.

[0002]

2. Description of the Related Art Styrofoam (polystyrene) or styrene paper is widely used because it is lightweight and inexpensive as a heat insulating material and a sound absorbing material. However, its raw material is petroleum, which is a typical material of environmental pollution, such as generating high heat during incineration after use, causing damage to the incinerator and generating a large amount of carbon dioxide gas. In addition, it has long been pointed out as a social problem, such as leaving polystyrene foam and leaving rivers and the sea polluted, and the emergence of materials that are environmentally friendly alternatives to polystyrene insulation and sound-absorbing materials has been anticipated. It is a fact. In order to provide such a material, a porous material using clay has been proposed (Japanese Unexamined Patent Publication No.
No. 230581), however, there is a problem that this porous body is fragile and does not have a strength that can be replaced with styrene foam or the like. Those using gelatin, fibrous bodies, polysaccharides, etc. together with clay have been proposed. These have some improvement in strength but have insufficient heat resistance, and in particular, have a problem that many cracks are generated by drying during manufacturing and the product value is reduced by half.

[0003]

Accordingly, the present invention provides
An object of the present invention is to provide a composite porous material that is compatible with the global environment, has excellent strength and heat resistance, and does not crack during drying during manufacturing.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, a porous material produced by subjecting a mixed sol containing fiber and water glass together with clay to a specific freeze-drying process has been developed. It has been found that both the compressive strength and the heat resistance are high and that no cracking occurs during drying, and the present invention has been accomplished based on this finding. That is, the present invention provides (1) a mixed sol containing clay, water glass, and fibers in an amount of 1 × 10
(2) The clay composite porous material according to (1), wherein the porous material is obtained by freezing at an average freezing rate of not less than ^-2 ml / sec and freeze-drying. (3) The mixed sol according to (1) or (2), wherein the mixed sol is obtained by mixing a clay sol having a solid content of 1 to 40% by weight, an aqueous dispersion of water glass, and an aqueous dispersion of fiber. Clay composite characterized in that a clay composite porous body and (4) a mixed sol containing clay, water glass and fiber are frozen at an average freezing speed of 1 × 10 ⁻² ml / sec or more, and then freeze-dried. It is intended to provide a method for producing a porous body.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The clay used in the present invention may be natural or synthetic, and those having as its main component those belonging to "clay minerals" in mineral classification are used without any particular limitation. Examples of natural products include montmorillonite,
Examples include smectites such as beidellite and saponite, kaolinite and aferon, and bentonite and acid clay containing smectite as a main component, preferably bentonite and acid clay. As the fiber, any fibrous substance can be used without any particular limitation.However, it is preferable to use incombustible fibers in view of the heat resistance of the obtained composite porous body, for example, mineral fibers such as wollastonite and asbestos, and glass. Fiber or the like can be used.

In the present invention, clay is dispersed in water together with fibers and water glass and used as a mixed sol. Specifically, this mixed sol can be prepared, for example, by mixing a clay sol, an aqueous dispersion of water glass and an aqueous dispersion of fibers, and sufficiently stirring the mixture. The ratio of the clay solid content in the clay sol at this time is usually 0.5 to 50% by weight, preferably 1 to 40% by weight.
%, More preferably 5 to 20% by weight. Water glass in the water glass water dispersion is usually 0.5 to 50% by weight,
Preferably 1 to 40% by weight, more preferably 5 to 20%
% By weight. The ratio of the fibers in the aqueous fiber dispersion is also usually 0.5 to 50% by weight, preferably 1 to 40% by weight, and more preferably 5 to 20% by weight. The mixing ratio of clay, water glass, and fiber is the desired strength of the composite porous body,
It is appropriately selected depending on heat resistance, weight, shape and the like, but preferably 5 to 20% by weight of water glass and 1 to 20% by weight of fiber based on clay. More preferably, for clay,
Water glass is 10 to 20% by weight and fiber is 5 to 10% by weight. If the amount of water glass is too large, many cracks may occur during drying, and if the amount is too small, the compressive strength and the like may deteriorate.
Further, if the fiber content is too large, the compressive strength and the like may deteriorate, and if the fiber content is too small, cracks may occur. By adjusting the solid-liquid ratio together with the mixing ratio of the three components, the strength and heat resistance of the obtained composite porous body can be arbitrarily selected.
In addition, components other than clay, water glass, and fiber can be added as needed as long as the weight and the properties of the porosity of the composite porous body are not impaired. For example, coloring and flavoring may be performed by adding a dye or a fragrance, or strength may be increased by adding a polysaccharide or gelatin.

[0007] The mixed sol obtained in this manner is 1 × 10 ^-2.
The desired composite porous body is obtained by rapidly freezing at a freezing rate of at least ml / sec and drying the frozen body without dissolving it. The freezing rate in the present invention is the volume of a sol that freezes for one second. When frozen at a speed of less than 1 × 10 ⁻² ml / sec, the size and shape of the pores become irregular, and the compressive strength and the like deteriorate. For freezing, liquid nitrogen, refrigerators, etc.
This can be done by ordinary means. Drying can also be carried out by ordinary means, and is usually freeze-dried under reduced pressure, but may be dried under reduced pressure without blowing.

In the present invention, a composite porous body having high compressive strength and heat resistance can be obtained by using water glass and fibers used together with clay. In addition, the composite porous body of the present invention hardly generates cracks due to drying during production. Although the reasons for these are not clear, since the fibers are uniformly dispersed in the clay reinforced by water glass, the fibers connect the water glass and the clay that shrink during drying to prevent the occurrence of cracks. Presumed.

[0009]

Next, the present invention will be described in more detail with reference to examples. Example 1 A clay sol having a weight-to-liquid ratio of 1: 9 was prepared from natural bentonite produced in Sazawa, Yamagata Prefecture and water, and left to stand for 24 hours to mature.
Commercially available water glass and noncombustible fiber (glass wool) were also dispersed in water so that the weight-solid ratio was 1: 9. These aqueous dispersions were treated with a clay: water glass: combustible fiber weight ratio of 7
The mixture was mixed at a ratio of 2: 24: 4 to prepare a mixed sol. This was put in a stainless steel container, immersed in liquid nitrogen, rapidly frozen at an average freezing speed of 3.0 × 10 ⁻² ml / sec, and the frozen body was dried under vacuum to obtain a composite porous body. The obtained composite porous body (average pore diameter: about 0.8 μm, porosity: about 90
%) Had no cracks due to drying, had a smooth surface, had higher compressive strength than expanded polystyrene, and exhibited high heat resistance (compressive strength: 5 kgf / cm ² , heat resistance: 1000 ° C.). Further, it was also possible to control the shape, such as a plate or a bar, depending on the container at the time of manufacture.

Example 2 A mixed sol having a weight ratio of clay: water glass: non-combustible fiber of 72: 24: 4 was prepared in exactly the same manner as in Example 1 and colored with red paint. It was frozen and dried in the same manner as in Example 1 to obtain a composite porous body. The obtained composite porous body (average pore diameter: about 0.8 μm, porosity: about 90%)
As in Example 1, it exhibited high compressive strength and heat resistance (compressive strength: 5 kgf / cm ² , heat resistance: 1000 ° C.), and no cracks were observed during drying.

Comparative Example 1 The same clay sol and water glass aqueous dispersion as in Example 1
A mixed sol was prepared by mixing water glass at a weight ratio of 75:25, and the mixture was frozen and dried in the same manner as in Example 1 to obtain a porous body. The obtained porous body had a lower compressive strength (3 kgf / cm ² ) than those of Examples 1 and 2, and a large number of cracks having a length of about 50 mm and a depth of about 5 mm were generated by drying at the time of production.

[0012]

As described above, the composite porous body of the present invention uses only materials that are compatible with the environment, and can be easily recovered and reused.
Even when discarded, it is returned to the soil and does not pollute the environment. Moreover, since it has higher compressive strength and heat resistance than styrene foam or the like, it can be used in place of styrene foam or the like, and can be used for a wider range of applications. further,
Cracks do not occur during drying like ordinary clay products,
An excellent effect is obtained in that a lightweight, porous and smooth surface can be obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C04B 38/00

Claims (4)

(57) [Claims] 1. A clay composite porous material obtained by freezing a mixed sol containing clay, water glass and fiber at an average freezing speed of 1 × 10 ⁻² ml / sec or more and freeze-drying the mixed sol. body. 2. The clay composite porous body according to claim 1, wherein the fibers are non-combustible fibers. 3. The mixed sol has a solid content of 1 to 40% by weight.
The clay composite porous body according to claim 1 or 2, which is obtained by mixing the clay sol, the aqueous dispersion of water glass, and the aqueous dispersion of fiber. 4. A method for producing a clay composite porous body, comprising: freezing a mixed sol containing clay, water glass and fiber at an average freezing speed of 1 × 10 ⁻² ml / sec or more, followed by freeze-drying. Method.