JPH05319948A - Granular inorganic foam having good water retaining property, its production and artificial culture soil - Google Patents

Abstract

PURPOSE:To obtain good artificial culture soil having high water absorbency and coarse face by abrading and removing part of a vitreous film on the surface of foam obtained by burning and expanding a formed article of expandable inorganic powder so as to give a prescribed water absorbency. CONSTITUTION:A particle molded article having expandable inorganic powder (e.g. shale, clay or coal ash) is heated and burned to >=1000 deg.C to give a foam having a smooth vitreous film on the surface. The vitreous film is subjected to abrasion treatment to form an inorganic foam having >=10wt.% water absorbency. A granular inorganic foam having a modified cross section and good water retaining properties is obtained therefrom. This granular inorganic foam is used for artificial culture soil for horticulture and hydroponic culture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granular inorganic foamed molded article having good water retention, a method for producing the same, and an artificial soil.

[0002]

2. Description of the Related Art Conventionally, in order to produce a lightweight aggregate having a specific gravity of 1 or less, a foaming inorganic material such as shale, clay, coal ash and slate is used as a raw material, and this is molded into a granular material, It is known to fire and foam (for example, JP-A-3-97643). The inorganic foam obtained in this manner has a low specific gravity, but its surface becomes a smooth vitreous material due to the melting during heating and foaming, and the whole particulate matter has a low water absorption rate. .. Then, such an inorganic foam having a smooth glassy surface has poor water retention when used as an artificial cultivator for gardening,
Moreover, there is a problem that the root survival rate of the plant is low, which is unsatisfactory as an artificial cultivator.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems found in conventional inorganic foams, and provides a granular inorganic foam having a rough surface and a high absorptivity, a method for producing the same and an artificial foam. The challenge is to provide soil.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a part of the vitreous film on the surface is removed by abrasion, the surface is formed to be a rough surface, and good water retention is characterized by having a water absorption rate of 10% by weight or more. An inorganic foam having is provided. Also,
According to the present invention, an artificial soil comprising a granular inorganic foam is provided. Further, according to the present invention, after the granular material of the expandable inorganic powder is fired and foamed to be an inorganic foam, surface abrasion treatment is applied to the inorganic foam having a water absorption rate of 10% by weight or more. A method for producing a granular inorganic foam having good water retention is provided.

The granular inorganic foam of the present invention is an inorganic foam formed on a glassy film having a smooth surface, in which at least a part of the glassy film on the surface is removed by abrasion and the surface is roughened. And the water absorption rate is improved to 10% by weight or more. According to the research conducted by the present inventors, the granular inorganic foam obtained by abrasion-removing a part of such a glassy film on the surface has a high water absorption rate and a rough surface, so that water retention and plant It has excellent root survival rate,
It was found to be of high quality as an artificial soil.
The water absorption referred to in this specification is the ratio (% by weight) of the water absorbed by the foam when the granular inorganic foam is immersed in water for 24 hours.

In order to produce a granular inorganic foam having good water retention according to the present invention, first, an expandable inorganic powder is formed into a granular material having a required particle size, which is fired at a high temperature and foamed to form a glass surface. An inorganic foam made of a quality film is obtained. In this case, as the expandable inorganic powder, any powder can be used as long as it causes foaming by high temperature firing. Generally, shale, clay, coal ash, slate, etc. are used, but gonite is preferably used because of its excellent foamability. In order to mold the expandable inorganic powder, a powdery raw material inorganic material may be added with a molding aid such as water, and then molded into a granular shape using a molding machine such as a pelletizer or an extrusion molding machine. The specific shape of the granular molded body may be a sphere, a pellet, a column, or the like, and the size thereof is usually about 0.5 to 10 mm.
In order to bake and foam the thus obtained granular molded body, the molded body may be baked at a high temperature of 1000 ° C. or higher, usually 1100 to 1200 ° C. in the presence of a fusion inhibitor. By this firing, the raw material molded body is foamed to form an inorganic foamed molded body having a smooth glassy film on the surface. As the anti-fusion agent, do not fuse at the foaming heating temperature,
Inorganic powder with strong fire resistance is used. Examples of such a material include refractory clay powder, clay chamotte powder, silica stone powder, and alumina powder. The addition amount is usually 2 to 10 parts by weight with respect to 100 parts by weight of the raw material compact. The method for producing the above-mentioned inorganic foamed molded article is described in detail, for example, in JP-A-3-97643.

The cross-sectional shape of the inorganic powder granular molding used as the raw material for firing and foaming in the present invention is not particularly limited and may be circular or irregular, but it is preferable to use those having irregular cross-section. .. In the case of a granular molded body having such a modified cross section, the granular inorganic foam having a modified cross section corresponding to the shape of the granular molded product can be obtained by firing and foaming the granular molded product. The granular foam having such an irregular cross section has a strong surface frictional force to support a plant by itself, and has an effect of improving root vigor.

As a preferred method for producing a granular molded product having a modified cross section, a wet pressurized molded product having surface-attached water or a dehydrated wet cake-like product having surface-attached water is prepared by rotating a crushing blade and a stirring blade. It is preferable to employ a granulation method in which crushing and agitation are performed to granulate and dry powder is gradually added during granulation.

In order to preferably carry out such a granulation method, first, as a raw material for crushing and stirring, a press-molded product or a dehydrated cake-like product containing a slight excess of water as compared with the saturated water absorption of the inorganic powder. make. The pressure-molded product is obtained by adding a slight excess of water to the inorganic powder than the saturated water absorption amount, kneading, and molding the kneaded product using a pressure-molding machine such as an extrusion molding machine or a press. You can The shape of the molded product may be a block shape, a rod shape, a plate shape, a column shape, or the like. On the other hand, the dehydrated cake-like material can be obtained by dehydrating a slurry containing inorganic powder with a pressure dehydrator. In this case, the inorganic powder pressure-molded product and dehydrated cake-like product contain a little excess of water than the saturated water absorption of the powder,
Water is attached to the surface to be in a wet state (wet state). The water content of the pressure-formed product and the dehydrated cake is
Generally, it is 120 to 130% by weight, preferably 123 to 127% by weight, of the saturated water absorption of the inorganic powder.

Next, the pressure-molded product or dehydrated cake-like material of the inorganic powder is put into a stirrer to granulate, and at the time of granulating, dry powder is gradually added to form a granular product without adhering water. Produce things. The stirrer used in this case is
It has a crushing blade and a stirring blade. The crushing blade has a length of 70 to 70 in which one end face extending in the longitudinal direction is formed into a blade shape.
150 mm, width 20-40 mm, thickness 10-20 mm,
It is preferably composed of a plate-shaped body of 12 to 18 mm. The thickness of the tip of this crushing blade is 3 to 8 mm, preferably 4 to 6 mm. The crushing blade has a function of crushing the pressure-formed product of the inorganic powder, which is the raw material, or the dehydrated cake-like product into small pieces. The stirring blade has a length of 80 to 160 mm,
It is made of a plate-shaped body having a width of 50 to 100 mm, and the thickness thereof is 10 to 20 mm. The stirring blade has a function of stirring the small divided body made of the inorganic powder formed by the crushing blade to granulate the granular material. The number of stirring blades is
5 to 20, preferably 10 to 1 for 10 crushing blades
It is a ratio of 5.

As the stirrer, it is preferable to use a stirrer having a structure provided with a plurality of rotating shafts having a plurality of the above-mentioned crushing blades and stirring roots. Further, the rotary shaft in this case may be arranged vertically or horizontally, but if it is arranged horizontally, the structure of the stirrer becomes simpler and the dry powder is dried. It is preferable because the body can be easily added.

In the above-mentioned granulation method, the pressure-molded product or dehydrated cake of inorganic powder is stirred at the same time as crushing by the rotation of the crushing blade and the stirring blade as described above, and then dried during that time. The operation includes a step of gradually adding the powder, and by this operation, the pressure-molded product of the inorganic powder or the dehydrated cake-like product is granulated into a highly fluid granular product having no surface-adhered water. Since the granular material thus obtained is formed by being divided by the crushing blade, its cross-sectional shape is
It does not show a circular shape, but an irregular shape. In addition, this granular material,
The particle size becomes smaller as the stirring time elapses. This stirring is sufficient for about 2 to 10 minutes, preferably about 5 to 8 minutes. The dry powder may be added little by little while stirring, preferably by spraying.
The addition time is 1 to 5 minutes, preferably 2 to 4 minutes. Further, the addition of the dry powder may be added at the same time as the crushing and stirring of the pressure-molded product or the dehydrated cake-like product,
It is also possible to add it after performing crushing and stirring to some extent.

The particle size of the dry powder is 3 to 20 μm, preferably 5 to 10 μm. Generally, it is preferable to use a powder having a particle size that is the same as or smaller than that of the inorganic powder that is the granulation raw material. The amount of this dry powder added varies depending on the type of the dry powder, but it does not absorb water adhering to the surface of the granules formed from the press-molded product or dehydrated cake-like product and gives the surface-dried granules. A sufficient amount will do. As the dry powder, any water-absorbing powder may be used, and either inorganic powder or organic powder can be used. As the inorganic powder, other than the various materials shown above as the raw material inorganic powder, refractory clay, clay chamotte powder, silica stone powder,
Alumina powder and the like are exemplified, and as the organic powder,
A hydrophilic polymer is preferably used. As such hydrophilic polymer, conventionally known ones, for example, carboxymethyl cellulose, hydroxyethyl cellulose, other cellulose derivatives such as cellulose sulfate, polyvinyl alcohol, polyvinyl pyrrolidone, sodium polyacrylate,
Examples thereof include sodium polymethacrylate, polyethylene oxide, sodium alginate, starch, and the like, but it is particularly preferable to use a super absorbent polymer. For such super absorbent polymer, for example, Kyoritsu Shuppan Co., Ltd.
Published by Fusayoshi Masuide, “OnePoint New Polymer Material”
Superabsorbent polymer ".

According to the above granulation method, the particle size is 0.6 to 3
Granules distributed in the range of 0 mm can be obtained at one time, but this particle size distribution depends on the particle size of the raw material inorganic powder, the water content of the pressure-molded product of the inorganic powder or the dehydrated cake, and the stirring. It can be controlled by the conditions. Generally, as the water content increases, the content of the granules having a large particle size in the obtained granulated product increases. In addition, as the water content decreases, the content of the particles having a small particle size in the obtained granular material tends to increase. The granular material obtained by this granulation method has an irregular cross section. Typical cross-sectional shapes are shown in FIGS. 1 (a), 1 (b) and 1 (c).

Next, the inorganic foam obtained as described above is subjected to abrasion treatment to scrape off a part of the vitreous film on the surface thereof. This abrasion treatment can be easily performed by stirring the inorganic foamed molded article under wet or dry conditions and rubbing the particles of the inorganic foamed molded article against each other. In this case, a wear aid such as silica sand may be added to promote surface wear of the inorganic foamed molded product. Further, this abrasion treatment can be carried out in the firing and foaming step while cooling the inorganic foamed molded body.
That is, the firing and foaming of the raw material molded body is carried out by using a heating furnace such as a rotary kiln. In this case, the foamed molded body is a cooling device attached to the heating furnace, generally agitating the baked product. It is cooled by a rotary cooler and then taken out. In the present invention, a member that promotes wear inside the rotary cooler (for example, fins)
It is advisable to attach the above-mentioned and to wear the surface of the inorganic foam in this rotary cooler. As a result, the product of the present invention can be obtained directly from the cooling device attached to the heating furnace without using a special wear device.

When the surface abrasion treatment of the inorganic foam is carried out in the present invention, the abrasion rate is 0.5 to 4% by weight, preferably 1 to 2.5% by weight. This wear rate is 0.5% by weight
If the amount is too small, the effect of improving water retention and plant root survival rate is not yet sufficient, while if it is more than 4% by weight, the mechanical strength of the inorganic foam molded article is reduced and the yield of the product is reduced. It is not preferable because it worsens. The surface wear rate R is expressed by the following equation. R = (A−B) / A × 100 (%) R: Surface abrasion rate (% by weight) A: Weight of inorganic foamed molded product before surface abrasion treatment B: Weight of inorganic foamed molded product after surface abrasion treatment

In the granular inorganic foam which has been subjected to the surface abrasion treatment of the present invention, its apparent specific gravity is 1 or less, usually 0.6 to
0.8, the water absorption rate is 10% by weight or more, usually 1
It is 5 to 20% by weight. The specific shape thereof may be spherical, columnar, granular, etc., and the particle size thereof is
It is about 1 to 25 mm, preferably about 2 to 20 mm. The granular inorganic foam of the present invention has good mechanical strength while having a light specific gravity, and the compression strength when one particle is subjected to compressive failure by applying a load from above is usually 40 kg.
That is all.

[0018]

INDUSTRIAL APPLICABILITY The surface-abrasive-treated granular inorganic foam according to the present invention has a high water absorption rate and its surface is roughened due to abrasion, and is therefore suitable as an artificial soil for horticulture. It is a thing. That is, the surface-abrasive-treated granular inorganic foam of the present invention has good water retention, and also has an excellent rooting rate of plant roots, which enables stable growth of roots. It is advantageously applied as an artificial soil for cultivation.

[0019]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Reference Example 1 As the raw material inorganic powder, an expandable shale powder having an average particle diameter of about 5 μm (saturated water absorption is about 18% by weight) was used. Further, as a granulating device, in a commercially available test biaxial forced kneading mixer (SF60, manufactured by Nikko Co., Ltd.), the total number of blades attached to two rotary shafts disposed inside was 16
8 of the stirring blades (length: 120 mm, width: 80 mm, thickness: 15 mm) were removed, and instead, a crushing blade consisting of a plate-shaped body having a length of 10 mm, a width of 40 mm, and a thickness of 10 mm. (Blade edge thickness: 4 mm) 6 pieces were used. After adding 20 kg of water to 100 kg of the raw material powder and mixing them well, an extruding machine was used to obtain a wet plate-like body having surface-adhered water having a thickness of 40 mm. Next, 50 kg of this plate-like body was put into the above-mentioned granulating apparatus, stirring was started, and at the same time, the above-mentioned raw material powder was added as a dry powder under stirring for 3 minutes of addition time, and further stirring was continued for 2 minutes. The granulation operation was completed. The granular material thus obtained had good fluidity without water adhering to the surface.

Reference Example 2 In Reference Example 1, a wet dehydrated cake (water content: 22% by weight) having surface-adhered water formed by dehydrating a slurry of a raw material inorganic powder is used as a raw material for granulation. At the same time, the same experiment was conducted except that the amount of the dry powder added was 12% by weight of the dehydrated cake. The granular material thus obtained has a good fluidity without water adhering to the surface.

Next, the results of examining the particle size distribution of the granules obtained in Reference Examples 1 and 2 using a sieve are shown in the following table.

[0022]

[Table 1]

Example 1 The granules having a particle size of about 10 mm or less obtained in Reference Example 1 were heated in the presence of clay chamotte as a fusion inhibitor in a firing furnace (rotary kiln) at a temperature of 1170 to 1190 ° C.
Baking for 30 minutes under the condition of oxygen concentration of 2 to 5 vol%,
An inorganic foam was obtained. This inorganic foam has a specific gravity of about 0.6.
~ 0.8, the dimensions were 2-20 mm. This granular inorganic foam had a modified cross section. A glassy film was formed on the surface of this inorganic foam.
The water absorption of this inorganic foam was as low as 8.7% by weight. Next, this inorganic foam was put into a stirrer having a stirring blade on its central axis and stirred at a rotation speed of 20 rpm until the surface wear rate became about 1% by weight.

The surface-abrasion-treated granular inorganic foam thus obtained had a glassy surface roughened, and its water absorption was 16.0% by weight. Also,
This one has sufficient mechanical strength as artificial soil,
The load for compressing and destroying one of the particles from above was 40 kg or more, and it did not cause any particular trouble in handling such as transportation and bagging.

Next, using the above-mentioned surface-abrasive-treated inorganic foam as artificial soil, hydroponics of plants was carried out as follows. As the test plants, Dracaena and Dorcaena fragrans
cv. Massangiana), Paraki (Pachi)
ra aquatica), Akebono Croton (Co
diaeum variegatum cv. Akeb
ono), Ficus Benjamina (Ficus ben)
jamina) and canary palm (Phoenix c)
anariensis Hort. ) Plants were used.
These plants were planted in an artificial soil consisting of the surface abrasion-treated inorganic foam and cultivated in a 50% light-shielding hard film house, and the growth of these plants was observed for about 2 months. In this case, irrigation was performed appropriately and fertilization was not performed.
As a result, it was confirmed that all plants grow well.

[Brief description of drawings]

FIG. 1 (a), (b), (c) shows a cross-sectional view of a representative inorganic powder granule having a modified cross section obtained by the granulation method of the present invention.

[Explanation of symbols]

 1,2,3 Inorganic powder granules

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[Procedure amendment]

[Submission date] July 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, in order to produce a lightweight aggregate having a specific gravity of 1 or less, a foaming inorganic material such as shale, clay, coal ash and slate is used as a raw material, and this is molded into a granular material, It is known to fire and foam (for example, JP-A-3-97643). The inorganic foam obtained in this manner has a low specific gravity, but its surface becomes a smooth vitreous material due to the melting during heating and foaming, and the whole particulate matter has a low water absorption rate. .. Then, the inorganic foam is such a surface was a smooth glassy, when used as artificial culture soil horticultural, poor water retention,
Moreover there is a problem of low survival rate of the roots of the plants were of unsatisfactory as artificial <br/> culture soil.

Claims (5)

[Claims] 1. A granular inorganic material having good water retention, characterized in that part of a glassy film on the surface is removed by abrasion to form a rough surface and has a water absorption rate of 10% by weight or more. Foam. 2. The granular inorganic foam of claim 1 having a modified cross section. 3. An artificial cultivation soil comprising the granular inorganic foam according to claim 1. 4. An inorganic foamed molded body having a water absorption rate of 10% by weight or more is obtained by subjecting a granular molded body of expandable inorganic powder to firing and foaming to form an inorganic foamed body, and then subjecting it to surface abrasion treatment. A method for producing a granular inorganic foamed molded article having good water retention. 5. The method according to claim 4, wherein the granular molding has a modified cross section.