JPH07330463A - Production of starting material used for expanded ceramic material - Google Patents

Abstract

PURPOSE:To obtain a starting material for an expanded ceramic meterial capable of uniform expansion even in the case of relatively fine particles having a narrow particle size distribution by granulating a thermally expandable slurried inorg. starting material with a spray drier. CONSTITUTION:A slurried inorg. starting material which is expanded by firing is granulated with a spray drier to obtain the objective starting material used for an expanded ceramic material. By this method, a product free from unevenness in expansion can be produced even when a water-soluble molten starting material is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a raw material used for producing a foamed ceramic material used for the purpose of heat insulation, sound absorption, etc., and particularly to an inorganic material (hereinafter referred to as thermal foaming property) which is foamed by firing. The present invention relates to a method for producing a raw material used for producing a foamed ceramic material obtained by granulating and firing a raw material).

[0002]

2. Description of the Related Art A foamed ceramic material obtained by using a granulated thermally expandable raw material is a molded product in which particles after foaming are fused and integrated with each other, and individual particles without fusion of each particle. There is a shaped lightweight aggregate.

In the case of a molded product, the raw material is granulated and filled in a container, spread on a conveyor or a plate, or after being molded by a press or the like, it is fired to expand each particle at the same time. It is manufactured by fusing and integrating the spaces.

In this case, the significance of granulation is that it can be packed more uniformly than non-granulated powder, that foaming is basically performed in each particle unit, and that there is a space between particles even immediately before melting by foaming. This is because a product having uniform foaming is likely to be obtained because, for example, water of crystallization that adversely affects foaming or gas generated by thermal decomposition of an organic substance is easily released.

In the case of a lightweight aggregate, the granulated heat-foamable raw material is fired while stirring the particles by using a rotary kiln so that the particles are not fused to each other, and foams are formed in individual particle units. Granulation is indispensable since it is manufactured.

In any case, if the particle size distribution is wide, the foaming temperature and the expansion ratio of the fine particles and the coarse particles are different, and it is difficult to obtain a uniformly foamed product. Therefore, a granulating raw material having a narrow particle size distribution is required. Is.

In the conventional granulation method, a dry powder raw material crushed by a ball mill, a vibration mill or the like is granulated with a pan type granulator or the like while adding water or an aqueous binder solution, and sieved. Later, I was getting the desired particle size range.

[0008]

However, especially when a raw material having relatively fine particles and having a uniform particle size in a desired particle size range is required, the above-mentioned granulation method results in a wide particle size distribution. There is a drawback that the yield becomes poor.

Further, in the pulverizing step of the raw material in a ball mill or a vibration mill, the wet raw material must be dried in the case of dry pulverization, and in the case of wet pulverizing, the slurry drying step and the dried product are made into powder. A secondary crushing process is required to do so, which is uneconomical.

Usually, the raw material of the foamed ceramic material is inexpensive, and natural glass or artificial glass that melts at a relatively low temperature is used as a main raw material, and the foamed raw material is added to the raw material.

A method of adding a melting raw material such as sodium carbonate, sodium silicate, borax, etc. to the above-mentioned raw materials to further lower the firing temperature to improve the production efficiency can be adopted. However, the melting raw material is water-soluble. Therefore, there is a problem in drying.

That is, the particles themselves just after granulation have low strength, and even if a binder such as PVA or methylcellulose is added for reinforcement, such binders can exert their effect only after being dried. Since the particles are destroyed when they are dried while moving like a rotary dryer, they cannot be dried unless they are spread on a drying container, a net, or a plate.

However, when dried in such a state, the water-soluble melting raw material moves to the surface of the filling body as water evaporates during the drying, so that the particles at the central portion of the filling body and the particles on the surface become. However, there is a drawback in that the composition varies and the foaming during firing becomes uneven.

Even if the baking is carried out directly without the drying step, the drying is naturally involved in the baking process, and as a result, the same drawbacks occur.

[0015]

As a means for solving the above-mentioned problems, the invention of claim 1 has a constitution in which a slurry-like inorganic raw material foamed by firing is granulated by a spray dryer. According to the invention of claim 1, in the invention of claim 1, the inorganic raw material contains a water-soluble raw material.

[0016]

The present invention has the above-mentioned structure and can be easily produced even with a raw material having relatively fine particles and a narrow particle size distribution. Even if a water-soluble melting raw material is used as the raw material, foaming can be performed. It is possible to manufacture products without variations.

That is, an appropriately prepared inorganic raw material mixture is put into a ball mill together with water and pulverized for a predetermined time, or a slurry is obtained, or if the raw material is a powder and pulverization is unnecessary, a mixer is used. The slurry obtained by mixing the raw material and water, by spraying droplets into the drying chamber of the spray dryer kept at a predetermined temperature with a nozzle, the droplet-shaped slurry touches the high temperature atmosphere in the drying chamber, The granules are instantly dried while maintaining the grain shape, and the obtained granules have narrower particle size distribution and stronger particles than the bread type granulator due to the characteristics of the spray dryer.

The adjustment of the particle size distribution is mainly determined by the concentration of the slurry and the nozzle diameter, and by appropriately selecting one of them, the granulation raw material having the desired particle size distribution can be easily obtained. Furthermore, since it is wet crushing,
There is no need for a step of drying the wet material, a step of drying the slurry, and a secondary crushing step for powdering the dried material.

When the raw material contains a water-soluble melting raw material, since the particles dried and granulated by a spray dryer are dried in a hollow shape (a state in which fine bubbles are gathered inside), the water-soluble melting raw material is melted. Since the raw material moves only in the slight thickness direction of the thin shell forming fine bubbles, the difference between the inside and the surface of one particle can be ignored.

As described above, the present invention is a very useful means as a method for producing a raw material of a foaming ceramic material to be used after granulation, and can effectively solve the drawbacks that have occurred conventionally.

[0021]

EXAMPLES Examples of the method of the present invention will be described below.

Example 1: 12% of Nagano clay which is the main raw material
And a synthetic glass powder (85%) and dolomite (3%) as a raw material for foaming and melting, 1200 kg, 655 liters of water.
It was put into a 2-ton ball mill together and wet-milled for 15 hours.

The resulting slurry had a water content of 36% and a pulverized particle size of 300% sieve residue was 4%. The slurry was pressure fed to a spray dryer with a pump pressure of 15 kg / cm ² , and sprayed into a drying chamber kept at 430 ° C. from a nozzle having a diameter of 2.4 mm to granulate.

The particles thus obtained had a water content of 2.5% and a particle size distribution of 0.1-0.3 mm was 14.4% and 0.3-0.8 mm was 8%.
It was 4.3%, 0.7% for 0.8 to 1.8 mm, and 0.6% for unused particle sizes of 0.1 mm or less and 1.8 mm or more.

This granulated raw material was spread on a mesh belt of a mesh belt kiln with a width of 1000 mm to a thickness of 10 mm, and fired at 1020 ° C. to produce a foam plate. The obtained product had a bulk specific gravity of 0.8 g / cc and was uniformly foamed.

Comparative Example 1: As a comparative example to Example 1, the same formulation as in Example 1 was dry-pulverized for 18 hours in a 2 ton ball mill so that the pulverized particle size was the same as in Example 1, and further, This raw material was granulated while spraying water using a pan granulator.

The granulation raw material thus obtained had a water content of 12%, and the particle size distribution was 4.1% for 0.1 to 0.3 mm and 1 for 0.3 to 0.8 mm.
6.5%, 52.3% was 0.8 to 1.8 mm, and 27.1% was 0.1 mm or less and 1.8 mm or more, which are unused particle sizes.

Thereafter, firing was performed under the same conditions as in Example 1 to produce a foam plate. The obtained product had a bulk specific gravity of 0.8 g / cc and was uniformly foamed.

Example 2: Artificial glass powder 5 as the main raw material
A mixture consisting of 6% and 30% of roe stones, which are all water-soluble melting raw materials of 5% sodium carbonate, 2% sodium nitrate, and 7% borax, was put into a 2 ton ball mill with 1200 kg of water and 675 l of water for 15 hours. Wet milled. In the case of this formulation, sodium nitrate mainly acts as a foaming raw material.

The resulting slurry had a water content of 36% and a pulverized particle size of 300% sieve residue of 2%. The slurry was pressure fed to a spray dryer with a pump pressure of 15 kg / cm ² , and sprayed into a drying chamber kept at 430 ° C. from a nozzle having a diameter of 2.4 mm to granulate.

The water content of the obtained granulation raw material is 1.8% or less, and the particle size distribution is 0.1% to 0.3 mm, 11.5%, 0.3 to.
0.8 mm is 77.6%, 0.8-1.8 mm is 9.3%, and the unused particle size of 0.1 mm or less and 1.8 mm or more is 1.6.
%Met.

This granulation raw material was spread on a mesh belt of a mesh belt kiln with a width of 1000 mm to a thickness of 10 mm and fired at 800 ° C., and the obtained product had a bulk specific gravity of 0.26 g / cc and was uniform. It was foaming.

Comparative Example 2: As a comparative example to Example 2, the same formulation as in Example 2 was pulverized with a 2 ton ball mill for 18 hours so that the pulverized particle size would be the same as in Example 1. This raw material was granulated while spraying water using a pan granulator.

The water content of the obtained granulation raw material was 11.8%,
The particle size distribution is 0.1% to 0.3 mm, 5.2%, 0.3 to 0.8 mm
Was 21.3%, 0.8-1.8 mm was 48.7%, and particle sizes not used 0.1 mm or less and 1.8 mm or more were 24.8%.

The granulated raw material was not dried, but was fired under the same conditions as in Example 2 to produce a foamed plate. The obtained product was vigorously foamed in the surface layer portion and the net portion, and the central portion was not foamed. The condition was apparent and was not worth the product.

The reason for this is that the melting raw material is naturally water-soluble during the firing process, and therefore the water-soluble melting raw material is present in the surface layer portion and the net portion of the packing due to the evaporation of water during drying. This is because the melting temperature of the surface layer portion and the net portion is lowered and the melting temperature of the central portion is increased on the contrary.

Example 3: 150 l of water was further added to the slurry obtained in the same manner as in Example 2 to make the water content of the slurry 41%, and this slurry was pumped to a spray dryer with a pump pressure of 15 kg / cm ^2. , And was granulated by spraying from a nozzle having a diameter of 2.4 mm into a drying chamber kept at 430 ° C.

The granulation raw material thus obtained had a water content of 2.4% or less and a particle size distribution of 0.1-0.5 mm was 92.3% and 0.1 m.
7.7% was below m and above 1.8 mm.

This granulation raw material was spread on a mesh belt of a mesh belt kiln with a width of 1000 mm to a thickness of 10 mm and baked at 800 ° C. The obtained product had a bulk specific gravity of 0.25 g / cc. As compared with Example 2, the foaming was more uniform, and the surface was smooth with few irregularities.

Example 4: The unsintered granulation raw materials obtained in Examples 2 and 3 were each calcined at 800 ° C. in an externally heated rotary kiln. A product without welding was obtained.

Comparative Example 3: When the granulation raw material obtained in Comparative Example 2 was fired at 800 ° C. in a rotary kiln of the same external heating type, there was much welding on the retort and between particles.

This is because a part of the particles are broken into powder by the impact at the time of charging into the rotary kiln or the impact caused by the rotation of the retort before the drying in the initial stage of firing, and the particles are retained in the retort. This is because the temperature has risen above the predetermined temperature.

As described above, in Example 1, as compared with Comparative Example 1 which is a conventional method, the loss (particle size not used) in the granulation step was small, that is, the granulation yield was high.

In Example 2, as compared with Comparative Example 2 which is a conventional method, a product having no foaming variation was obtained even if a water-soluble raw material was used.

In the third embodiment, a granulated product in the fine particle region is used as compared with the first embodiment, and the extreme poor granulation yield in the fine particle region of the conventional granulation method is efficiently adjusted by adjusting the water content. Goods have been obtained with the manufactured products.

Example 4 demonstrates that the strength of the granulated particles is higher than that of Comparative Example 3 which is a conventional method, and a product having a desired particle size and specific gravity could be obtained.
The same result was obtained not only by the rotary kiln but also by the fluidized bed heating method.

When the raw materials granulated under the same conditions as in Examples 2 and 4 were tested by changing only the firing temperature, the bulk specific gravity was 1.55 g / cc and 1.51 g / cc at 720 ° C., respectively.
Bulk specific gravity is 0.63 g / cc, 0.6 g /
Bulk specific gravity is 0.21g / cc, 0.19g at cc and 820 ℃
/ Cc, and a desired expansion ratio (bulk specific gravity) can be obtained by selecting the firing temperature.

In the case of Comparative Example 2, the difference in foaming between the net portion, the surface layer portion and the central portion was extremely large in any temperature range, and it was not suitable as a product.

The main raw material may be glassy or vitrified by firing. Natural glass materials such as Nagano clay, shirasu, obsidian, pearlite, anti-firestone, etc.
Glass powder, frit, etc., which are artificial glass raw materials, are suitable, and any one of them may be used alone, or a plurality of them may be used.

The reason why the water-soluble raw material is used as the foaming and melting raw material is that it is inexpensive and has a large melting effect, and the amount used may be arbitrarily adjusted depending on the foaming ratio and the firing temperature.

In the production of the slurry, it is not necessary to add all the raw materials and water to the ball mill, and when using raw materials pulverized to a desired particle size in advance, pulverization with a ball mill or the like is not necessary. Simply add water and raw materials to the mixture and stir and mix.If the grain size of some raw materials is coarser than the desired grain size, grind the raw materials wet or dry with a ball mill etc. May be mixed with stirring.

With respect to the strength of the granulating raw material, the strength of the granulating raw materials of all the examples and the comparative examples to which 0.3% of organic methyl cellulose was added as a binder is markedly improved, while the strength of the granulating raw materials is remarkably improved. Is only slightly improved.

In addition, as the binder, celluloses, PVA, molasses, etc. are effective in the organic system, and water glass, etc. are effective in the inorganic system, and the addition amount is appropriately 1% or less in terms of solid matter.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuo Imahashi 4-23 Tsutsujigaoka, Chofu-shi, Tokyo Kamidai housing complex 27-402

Claims (2)

[Claims] 1. A method for producing a raw material used for a foamed ceramic material, which comprises granulating a slurry-like inorganic raw material that is foamed by firing with a spray dryer. 2. The method for producing a raw material used for a foam ceramic material according to claim 1, wherein the inorganic raw material contains a water-soluble raw material.