JPS61251530A - Production of glass coated shell granule - Google Patents

Abstract

PURPOSE:To obtain lightweight granules having low water absorption and improved strength, by coating the surface of core material of granule of perlite raw ore with glass powder through a binder and heating the coated material so that the core material is expanded and sintered to the glass powder layer. CONSTITUTION:Perlite raw ore is ground to form granules, the granules are used as a core material, a binder is stuck to the surface of the core material and the surface is coated with glass powder which contains optionally a blowing agent. Then, the granulated material is dried, heat-treated, the granule of perlite raw ore which becomes the core material is expanded in the final process, so that the glass powder layer is sintered to the core material. Consequently glass coated shell granule which makes the most of characteristics of non-combustible particle of perlite which becomes the core material, having suppressed water absorption and bulk density and extremely improved crushing strength is easily obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a lightweight material useful as a material for heat insulating materials, heat retaining materials, various wall materials, aggregates, etc. used in civil engineering, construction materials, and other uses. The present invention relates to a method for producing glass-shelled granules.

[Prior art]

Conventionally, the method for obtaining relatively lightweight granular molded bodies made of glass is to mix glass powder and decomposable blowing agent powder, add a binder to the mixture, granulate it, and then process the granulated product. A method is known in which glass powder is foamed while being heated to melt and sinter it to obtain spherical foamed glass particles.

However, since the glass foam particles produced by the above method have a single structure, they have low strength and high bulk density. Furthermore, since the glass foam particles themselves have a single structure, not only does it take a long time to grow and granulate them from the powder particles, but it is extremely difficult to obtain granules of uniform size. The particle size distribution becomes wide and the yield decreases when trying to obtain the desired particle size. On top of that,
If glass foam particles with uniform particle size are intended, sintering and
It was necessary to sieve the granules before the foaming process.

On the other hand, pearlite (including expanded pearlite), which has been commercially available as a material for construction materials, is an inorganic "granular material" made by crushing pearlite etc. and firing it, but it has a high open porosity and water absorption. It is extremely large (more than 70% volume ratio) and has weak strength, so it has the disadvantage of severely limiting its uses, such as being unsuitable for building wall materials and insulation materials that require low water absorption. It had a point.

Therefore, the applicant first decided to use the above pearlite (foamed)
We have proposed glass-shell-coated granules that compensate for the above-mentioned drawbacks of pearlite itself, and a method for producing the glass-shell-coated granules. However, in the above manufacturing method, glass shell-covered granules are produced using pearlite (non-combustible particles having communicating holes) which has been foamed by heating and firing pearlite raw stone in advance. Therefore, not only are two heating and firing processes required: firing the pearlite raw stone and firing the entire glass shell-coated granules made by covering the fired and foamed pearlite with a glass shell, but also the second heating and firing process. There is a disadvantage that the pearlite that forms the core material that is sintered by heating and firing is not tightly sintered with the glass shell on the outside.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned problems, and makes use of the characteristics of pearlite raw stone that has foamability to suppress water absorption to a low level and significantly improve strength, as well as reduce weight and The purpose of the present invention is to provide a method for producing glass shell-coated granules that shortens the granulation process, ensures uniformity of particle size, and further reduces the heating and sintering steps and provides a good sintered state. It is.

[Structure of the invention]

The method for producing glass shell-coated granules according to the present invention involves pulverizing raw pearlite to produce granules, using the granules as a core material, and adhering a binder to the surface of the granules, and then adding a blowing agent as needed. coated with glass powder,
Next, the granules are dried and heat-treated, and in the final step, the raw pearlite granules that will become the core material are foamed and the glass powder layer is sintered to the core material, thereby forming non-combustible pearlite particles that will become the core material. It is easy to obtain glass shell-coated granules that have low water absorption and bulk density, and significantly improved single-particle crushing strength, while taking advantage of the characteristics of The present invention is characterized in that it is configured to reduce the amount of sintering and to obtain a good sintered state.

〔Example〕

An embodiment of the present invention will be described as follows.

Granules are produced by crushing raw pearlite.

This pearlite raw stone is originally foamable and has the property of foaming when heated and fired, and is made of obsidian-based natural stone, pearlite-based natural stone, or pinestone-based natural stone. . The above-mentioned granules serve as the core material of the glass-shelled granules, and are used after being crushed and sieved to a desired particle size (for example, 10 to 12 mesh).

Next, the sieved raw pearlite granules are fed to a pan-type granulator, and an aqueous polyvinyl alcohol solution is added thereto as a binder to wet the surface of the granules with the binder. As the above-mentioned binder, it is appropriate to use a solution of a substance having a so-called thickening effect, such as polyvinyl alcohol, as well as an aqueous solution of water-soluble polymers such as carboxymethyl cellulose and starch.

On the other hand, a foaming agent is mixed with glass powder to obtain a mixture. Mixing of glass powder and blowing agent is usually done using a super mixer (
(Made by Yoda Seisakusho ■) and mix. The above-mentioned super mixer is a batch type, and is equipped with a special blade-shaped mixing arm in the upper center, and a high-speed chopper for fine granulation, for example. This is used to mix and granulate powder.

The above-mentioned glass powder, for example, together with the glass component, is S 1
0 z (70wt%), Adz ○3 (5
wt%), Bz Oz (14wt%)
, Fez 03 (0,5-t %) , Ca
O (1wt%) Kz O (2wt%), Na
20 (6.5wt%), BaO (1wt%)
A glass powder of 200 mesh or less with the composition of Further, as the above-mentioned foaming agent, for example, about 300 to 400
1IIesh calcium carbonate (Ca CO3) powder is used, and 3 parts by weight is blended with the glass powder. Examples of the blowing agent include various powdered compositions that can be thermally decomposed to generate gas during the heat treatment described below, including decomposable blowing agents known in the field of foaming of synthetic resins. Among these, as mentioned above, it is preferable to use a carbonate such as calcium carbonate or a carbon dioxide gas generating agent such as carbon powder. Further, the mixing ratio of the glass powder and the decomposable blowing agent is preferably adjusted so that the amount of the blowing agent is 0.5 to 10 parts by weight per 100 parts by weight of the glass powder.

If it is less than 0.5 parts by weight, there is too little blowing agent and the absolute amount of decomposed gas is insufficient, and if it exceeds 10 parts by weight, some of the decomposition products of the blowing agent will crystallize, resulting in high density. This is because it is not preferable in terms of weight reduction.

The mixture of the glass powder and the blowing agent is supplied to the pan-type granulator mentioned above, and the pan-type granulator is started. Due to the transfer of the pan-type granulator, the core material made of the raw pearlite granules becomes a nucleus and grows while adhering the glass powder mixture with a binder. After a predetermined period of time has elapsed in this state, granules are produced in which the raw pearlite is coated with a glass shell made of a glass powder material.

To explain the formation process of the above-mentioned coating layer in more detail, the above-mentioned binder is sprayed onto the surface of the raw pearlite granules that will become the core material using a sprayer or other means to moisten it, and the core material is mixed with glass powder and decomposed foaming. A coating layer is formed by transferring the mixture onto the mixture of agents to adhere the mixture to the outer periphery thereof, and continuing to transfer while appropriately spraying a binder to grow an adhesion layer. Note that it is also possible to coat the core material by bringing it into contact with a mixture consisting of glass powder, a decomposable foaming agent, and a binder. That is, the granulation method can be a conventional method or any method similar thereto (for example, a sugar coating machine). In the case of the above-mentioned transfer method, for example, the core material moistened with a binder is placed on top of the glass powder, rolled there to adhere the glass powder, and then moved onto the decomposable blowing agent powder and rolled there. By depositing the foaming agent and repeating this operation alternately, a mixed layer is formed without mixing the glass powder and the foaming agent in advance.

The granules thus produced are first dried at a predetermined temperature for a predetermined time. This drying process is carried out to eliminate moisture contained in the binder used before sintering, and is intended to shorten the sintering time and prevent explosions during sintering due to the moisture content. It is effective in preventing

Finally, the dried granules are heat-treated in an electric furnace,
The glass shell and raw pearlite granules are sintered at the same time. As a result, the pearlite raw stone forming the core material of the glass shell-coated granules is foamed and sintered, and on the other hand, if the glass shell made of the glass powder layer also contains a foaming agent, it is simultaneously foamed and sintered. As a result, glass-shell-coated granules are obtained, which consist of granules having a structure in which the core is foamed pearlite raw stone, that is, pearlite, and the outer surface is coated with a sintered glass shell made of a glass powder material. In addition, when the glass powder has foaming properties including a foaming agent,
In the heating step of the final treatment, the glass shell is linearly heated to the foaming temperature of the foaming agent, and after the glass shell is sintered and foamed, it is allowed to cool at room temperature. However, if the glass powder does not contain a blowing agent and has non-foaming properties, it is sufficient to heat the glass powder layer to a temperature at which it sinteres into a hard glass shell.

The above heat treatment is usually carried out by holding the glass particles in a high-temperature heating furnace for a predetermined period of time at a temperature that allows at least the glass particles to fuse together. The temperature at this time depends on the melting point of the glass powder, but usually 700 to 900°C is suitable.

Further, a heating time of 1 to 15 minutes is sufficient. This heat treatment causes the foaming agent in the coating layer to separate and form bubbles in the fused glass powder layer, resulting in the outer layer becoming porous, as is clear from the micrograph in Figure 1. A glass shell-coated granule is obtained, which is made of a glass foam layer, the core material of which is made of a pearlite layer with a high foaming rate, and the inner and outer layers are integrally sintered.

The core material of the glass shell-coated granules produced by the above method is an inorganic granule that has been calcined into raw pearlite granules, and has numerous communicating pores, including some that coexist with closed cells. The foamed pearlite itself has a very high open porosity and a water absorption rate of 70% or more by volume. This pearlite is usually single grain (particle size 5 to 7n+
Although it has a relatively low crushing strength of 0.373 kg, the foamable glass shell-coated granules obtained as described above have a low bulk density and are lightweight. At the same time, the water absorption rate is kept low, and the single grain crushing strength is also significantly the same as above.

In addition, as shown in Figure 2, glass shell-coated granules using raw pearlite as the core material have a certain relationship between the thickness of the glass acid coating layer and the bulk density. found. As shown by the graph in the same figure, when the thickness of the coating layer made of glass acid is less than 0.5fl,
It's just that it's coated,
This coaching does not only contribute to foamability, but also, if the coating layer becomes too thick, the proportion of the glass foam layer to the core material increases, increasing the bulk density of the glass shell-coated granules. In other words, the optimum thickness of the glass acid coating layer, which forms the outer shell of pearlite raw stone, is approximately 0.7 to 0.9 m, thereby minimizing the bulk density of the particles (0.17 g). /cc). At least the thickness of the coating layer is desirably set within the range of 0.5 m to 1.3 m in consideration of the relationship with bulk density.

The foamability (bulk density) with respect to the thickness of the coating layer is as shown in Table 1. (However, the pearlite raw stone that is the core material has a mesh size of 10~l'l and its average diameter is 1.5
4n. ) Table 1 In addition, glass shell-coated granules (in an unfoamed state before heating and firing) made by using obsidian as the raw pearlite and coating the granules with a layer of glass powder were heated for various times. The experimental data showing the physical properties when foamed by heating and firing were as shown in Tables 2 to 5.

Table 2 [Glass shell-coated granules 4 to 5 n+esh, foamable glass layer thickness average 1.42 m, core material formed of obsidian granules. Table 3 [Glass shell-coated granules 5 to 6 mesh, foamable glass layer thickness average 1.06 mm, core material made of obsidian granules. Table 4 [Glass shell-coated granules 6 to 7 mesh, foamable glass layer thickness average 0077 mm, core material made of obsidian granules. Table 5 [Glass shell-coated granules 7 to 8 mesh, foamable glass layer thickness average 0.53 mm, core material made of obsidian granules. ] Compared to conventional methods, the method of the present invention uses a core material during granulation, so it can significantly shorten the time required for the granulation process, and furthermore, by using a core material of a predetermined particle size in advance, uniformity can be achieved. Granulation with a suitable particle size can be easily carried out. Therefore, substantially uniform glass foam particles with a narrow particle size distribution can be obtained in a short time.

Such glass-shelled granules are useful as noncombustible heat insulating materials, lightweight aggregates, and the like. Note that the size of the obtained foamed glass particles depends on the size of the core material and the degree of foaming of the core material, but the particle size can be controlled as appropriate.

[Experimental Example 1] Natural obsidian was used as pearlite raw stone, and it was crushed into granules of about 1.5 fins. The granules were fed to a pan-type granulator, and 1% polyvinyl alcohol was added as a binder.
The surface of the obsidian granules was wetted with the binder by spraying an aqueous solution. On the other hand, as a glass component, Sto! (70wt%
), AJz 03 (5-t%), Bz Oz
(14wt%), Fez 03 (0.5wt%)
%), CaO (1wt%) K, O (2wt%
%), NazO (6.5wt%), Ba
200m of hard glass with a composition of O (1wt%)
The glass powder was pulverized into a glass powder having a size of esh or less, and 3 parts by weight of CaC0 powder (approximately 300 to 400 mesh) as a foaming agent was added thereto and mixed using a super mixer.

The above mixture was supplied to the pan-type granulator containing the obsidian granules, and the surface of each granule was coated with a glass coating layer to a thickness of about 0.5 mm to form the granules. Obtained. After further drying, this granulated material was heated for 10 minutes in an electric furnace set at 900°C.

The glass shell-coated granules obtained as described above have a composite granular structure in which the core material obsidian is foamed and the outside is further covered with glass foam, and the bulk density is 0.19.
g/cc, water absorption rate 3.1 wt%, crushing strength 1.10
It was kg.

[Experimental Example 2] Obsidian granules similar to those in Experimental Example 1 were fed to a sugar coating machine, and a 1% aqueous solution of polyvinyl alcohol was sprayed as a binder to wet the surface of the obsidian granules. Next, the same mixture of hard glass and foaming agent as in Example 1 was fed to a sugar coating machine to obtain granules coated with glass powder to a thickness of about 11 m. After drying this granulated material, it was heated for only 7 minutes in an electric furnace set at 900°C. The glass shell-coated granules obtained as described above have a bulk density of 0.18 g.
/cc, water absorption rate of 3.54%, and crushing strength of 2.3 kg, and had a composite grain structure in which the core material, obsidian, was foamed and the outside was further covered with glass foam.

〔Effect of the invention〕

As described above, the method for manufacturing glass shell-coated granules according to the present invention uses pearlite raw granules as a core material, coats the core material with glass powder using a binder, and then dries and heats the core material. processing to foam and sinter the pearlite raw stone,
At the same time, the glass powder layer is sintered, so even if communicating pores are formed in the foamed pearlite and the water absorption rate increases, the characteristics of the pearlite itself are utilized and the glass acid forming the outer shell increases the water absorption rate. This makes it possible to keep it low. Furthermore, since it is formed into a double structure with glass acid having pearlite as its core, it has low bulk density and light weight, and also has high single-grain crushing strength.

In addition, when producing the glass-shelled granules, the pearlite, which is the core material of the glass-shelled granules, is granulated before being grown, so the granulation time can be significantly shortened, and the particle size of the glass-shelled granules can be uniform. can be easily maintained.

Furthermore, since the firing step for the pearlite raw stone before granulation is omitted and the pearlite raw stone coated with glass acid is foamed by heating and firing in the final step, the manufacturing process can be shortened.

Furthermore, since it is possible to foam the pearlite raw stone as the core material and the glass layer covering it at the same time, it has the excellent effect that the inner and outer layers are easily fused and a tightly sintered state can be obtained. It is something to play.

[Brief explanation of drawings]

FIG. 1 is a microscopic cross-sectional view of the glass shell-coated granules produced according to the present invention, and FIG. 2 is a graph showing the dependence of bulk density on the coating layer thickness of the glass-shell coated granules.

Claims (1)

[Claims] 1. Pulverize raw pearlite to produce granules, use the granules as a core material, attach a binder to the surface, coat with glass powder, and then use the granules as a core material. A method for producing glass shell-coated granules, which comprises drying and heat-treating the raw pearlite granules, which serve as the core material, in a final step of foaming and sintering the glass powder layer to the core material. 2. The method for producing glass-shelled granules according to claim 1, wherein the pearlite raw stone is an obsidian-based natural stone. 3. The method for producing glass shell-coated granules according to claim 1, wherein the pearlite raw stone is a pearlite-based natural stone. 4. The method for producing glass shell-coated granules according to claim 1, wherein the glass powder has foaming properties.