JPH0146457B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to the production of lightweight glass-shelled granules useful as materials for heat insulating materials, heat retaining materials, various wall materials, aggregates, etc. used in civil engineering, construction materials, and other uses. It is about law. [Prior Art] A conventional method for obtaining relatively lightweight granular molded bodies made of glass is to mix glass powder and decomposable blowing agent powder, add a mixture to the mixture, granulate it, and then granulate it. A known method is to heat the granules to melt and sinter the glass powder while foaming it to obtain spherical foamed glass particles. However, since the glass foam particles produced by the above method had a single structure, they had low strength and high bulk density. Furthermore, since the glass foam granules 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, and the particle size The distribution becomes wide and the yield decreases when trying to obtain the desired particle size. On top of that,
When glass foam particles with uniform particle size are intended,
It was necessary to perform a sieving process on the granules before the sintering/foaming process. On the other hand, perlite (including expanded perlite), which has been commercially available as a material for construction materials,
is an inorganic granular material made by crushing pearlite, etc. and firing it. However, it has a high continuous porosity and extremely high water absorption (more than 70% by volume), and is also weak in strength, so its uses are severely limited. There is a drawback that
For example, they have the problem of being unsuitable for building wall materials, heat insulation materials, etc. that require low water absorption.
Therefore, the applicant first proposed a method for producing glass-shell-coated granules by producing glass-shell-coated granules using the above-mentioned pearlite (foamed), thereby compensating for the above-mentioned drawbacks of pearlite itself. did. However, the above manufacturing method uses pearlite (non-combustible particles with communicating holes) that has been foamed by heating and firing pearlite raw stone in advance.
This produces glass-shelled granules. 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 sintering state between the pearlite which forms the core material which is sintered by heating and firing and the outer glass shell is not tightly sintered. [Object 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 having foamability to suppress water absorption to a low level and significantly improve strength. In addition, the present invention provides a method for manufacturing glass shell-coated granules that achieves weight reduction, shortens the granulation process, ensures uniform particle size, etc., reduces heating and firing processes, and provides a good sintered state. The purpose is to [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. Then, the granules are dried and heat-treated, and in the final step, the raw pearlite granules that serve as the core material are foamed, and the glass powder layer is used as the core material. By sintering, it is possible to easily obtain glass shell-coated granules that take advantage of the properties of non-combustible pearlite particles that serve as the core material, keep water absorption and bulk density low, and have significantly improved single-grain crushing strength. Shortening granulation time, making particle size uniform, and heating/
It is characterized by being configured to reduce the number of firing steps and to obtain a good sintered state. [Example] An example of the present invention will be described as follows. Granules are produced by crushing raw pearlite.
This pearlite raw stone is originally foamable and can be heated and
It has the property of foaming when fired, and is made of obsidian-based natural stone, pearlite-based natural stone, or pinestone-based natural stone. The above granules serve as the core material of the glass-shelled granules, and after pulverization, the desired particle size (e.g.
Use a sieve (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,
For example, in addition to polyvinyl alcohol, aqueous solutions of water-soluble polymers such as carboxymethyl cellulose and starch are exemplified. On the other hand, a foaming agent is mixed with glass powder to obtain a mixture. The glass powder and the foaming agent are usually mixed using a super mixer (manufactured by Kawada Seisakusho Co., Ltd.). 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 on one side. The powder is mixed and granulated internally. The above glass powder contains, for example, SiO ₂ (70wt%), Al ₂ O ₃ (5wt%), B ₂ O ₃ (14wt%) as glass components.
%), Fe ₂ O ₃ (0.5wt%), CaO (1wt%) K ₂ O (2wt
%), Na ₂ O (6.5wt%), and BaO (1wt%). Glass powder of 200mesh or less is used. Further, as the foaming agent, for example, about 300 to 400 mesh calcium carbonate (CaCO ₃ ) powder is used, and 3 parts by weight is added to the glass powder. This blowing agent is
Examples include various powder compositions that can be thermally decomposed to generate gas during the heat treatment described below, including decomposable foaming 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 will be too little blowing agent and the absolute amount of decomposed gas will be insufficient, and if it exceeds 10 parts by weight, some of the decomposition products of the blowing agent will crystallize and become denser, resulting in a lighter weight. This is because it is unfavorable in terms of compatibility. 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 rolling motion 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. When a predetermined period of time has elapsed in this state, a granulated product is produced by coating the pearlite raw stone 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. The coating layer is formed by rolling the mixture over the agent mixture to adhere the mixture to the outer periphery of the mixture, and continuing to roll while appropriately spraying the 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 rolling 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 applying the foaming agent to the glass powder 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 caused by the moisture content. It is effective in preventing Finally, the dried granules are heat-treated in an electric furnace to simultaneously sinter the glass shell and raw pearlite granules. 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 a foaming property including a foaming agent, in the heating step of the final treatment, it is heated linearly to the foaming temperature of the foaming agent, and after this 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 is usually 70~
900℃ 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 made by firing granules of raw pearlite, and has countless communicating pores (coexisting with closed cells). ), the foamed pearlite itself has a very high open porosity and a water absorption rate of over 70% by volume. This pearlite is usually a single particle (particle size 5 to 7 mesh) with a relatively low crushing strength of 0.373 kg, but the foamable glass shell coating obtained as described above The granules have a low bulk density and are lightweight, and their water absorption rate is kept low.
Moreover, the single grain crushing strength is also significantly improved. Furthermore, 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 coating layer of the glass shell and the bulk density. found. As shown in the graph of the same figure, if the thickness of the coating layer forming the glass shell is 0.5 mm or less, it is simply a coating, and this coating does not contribute to foaming properties. Moreover, if the coating layer becomes too thick, the ratio of the glass foam layer to the core material will increase, and the bulk density of the glass shell-coated granules will increase. In other words, the optimal thickness of the coating layer of the glass shell, which is made up of pearlite raw stone as its core and its outer shell, is approximately 0.7 to 0.9 mm, thereby minimizing the bulk density of the particles (0.17 g/cc). ) can be suppressed. At least the thickness of the coating layer is desirably set within the range of 0.5 mm to 1.3 mm in consideration of the relationship with bulk density. The foamability (bulk density) relative to the thickness of the coating layer is as shown in Table 1. (However, the pearlite raw stone that is the core material is 10 to 12 mesh, and its average diameter is 1.54 mm.)

[Table] In addition, glass shell-coated granules (in an unfoamed state before heating and firing), which are made by using obsidian as pearlite raw stone 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】

【table】

【table】

〔Effect of the invention〕

As described above, the method for producing glass shell-coated granules according to the present invention uses pearlite raw granules as a core material,
This core material is coated with glass powder using a binder, and then dried and heat treated to foam and sinter the pearlite raw stone, and at the same time sinter the glass powder layer. Even if communicating pores are formed in the foamed pearlite and its water absorption rate increases, it is possible to utilize the characteristics of the pearlite itself and to suppress the water absorption rate to a low level by the glass shell forming the outer shell. Also, because it is formed in a double structure with a glass shell with pearlite as the core,
It has a low bulk density, is lightweight, and has high single grain crushing strength. In addition, during the production of glass-shelled granules, pearlite, which is the core material of the glass-shelled granules, is grown while being granulated, which significantly shortens the granulation time and improves the uniformity of the particle size of the glass-shelled granules. It can be easily maintained. Furthermore, since the firing step for the pearlite raw stone before granulation is omitted and the pearlite raw stone covered with the glass shell is foamed by heating and firing in the final step, the manufacturing process can be shortened.
Furthermore, it is possible to foam the raw pearlite stone as the core material and the glass layer covering it at the same time, making it easy to fuse the inner and outer layers and create a tightly sintered state. It is effective.

[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. Pulverizing raw pearlite to produce granules;
This granule is used as a core material, and after a binder is attached to its surface, it is coated with glass powder, and then this granule is dried and heat-treated to produce raw pearlite granules that will become the core material in the final process. A method for producing glass shell-coated granules, characterized by foaming and sintering a glass powder layer into a core material. 2. The method for producing glass shell-coated 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.