JPS6365617B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing foamed glass particles used as heat insulating materials, aggregates, etc. in construction and other fields. [Prior Art] As a conventional example of a method for manufacturing this type of glass foam beads, a manufacturing method disclosed in Japanese Patent Application Laid-Open No. 58-9833 is known. In this conventional example, a first raw material powder whose main components are a first glass powder and a blowing agent powder is hardened with a binder to form a first granule, and a second glass powder which does not contain a blowing agent is the main component. A second raw material powder is coated on the surface of the first granules with a binder to form a second granule, and a powdered release agent is further coated on the surface of the second granule to form a third granule. Finally, the third granules are heated to form glass foamed granules, thereby obtaining glass foamed granules in which the outer grain is made of a glass layer and the inside has a multicellular structure. However, in the case of the above-mentioned conventional example, a pan-shaped granulator is used in the granulation process, and in this method, the powder is grown by rolling in a pan-shaped container to form grains. ) takes a long time to obtain grains. In addition, the particle size distribution of the particles produced in the bread mold is larger than powder ~ 3.5 mesh (when aiming for 8 to 9 mesh), and the yield is low if you try to obtain the desired particle size. Moreover, an additional sieving step is required. Furthermore, since the surface of the raw material granules exhibits viscosity due to the binder, coalescence of grains occurs during the grain growth process in the granulation process, resulting in blocking. As described above, the above-mentioned method has serious industrial and economical problems because the granulation process requires a long time and it is not possible to efficiently produce large quantities of uniform products. Apart from the above conventional example, as disclosed in Japanese Patent Application Laid-open No. 142424/1983, a mixture of glass particles and a blowing agent is granulated into noodle shapes, which are heated to form cellular glass beads. In the step of further cooling, it is also known to select the properties and amount of blowing agent used, heating temperature, and heating time to produce foamed glass particles with a multicellular structure that has low bulk density and low water absorption. . However, in the case of this conventional example, uniform particles with good foamability cannot be obtained. Furthermore, since the raw material granules are noodle-shaped, the bonding force within the granules varies, and even if these are sintered, uneven foaming occurs within the granules. Furthermore, since water is used as a binder, the binding force is weak, and the noodle-like shape of the raw material granules is more likely to break into smaller pieces, resulting in the generation of fine powder. Furthermore, if you try to sinter and foam noodle-shaped raw material particles to obtain a uniformly foamed product, a low density, and a multicellular structured particle with low water absorption, the sintering process must be complicated as in the conventional example. Requires condition management. Furthermore, because measures such as applying an anti-blocking agent are not taken in the noodle granulation process, particles may coalesce together at the stage of foaming in the sintering process, or when sintered in a rotary kiln. There is a problem in that particles adhere to the kiln wall. Therefore, in the above method, a large number of defective products are produced, the production efficiency is extremely low, and it is extremely difficult to obtain foamed glass beads having a uniform shape and a low bulk density. [Object of the Invention] The present invention has been made in consideration of the above-mentioned problems in the conventional examples, and it is possible to efficiently produce glass foam particles having low bulk density, sufficient crushing strength, and excellent heat insulation properties. The object of the present invention is to provide a method for manufacturing glass foam beads that can be manufactured at low cost. [Structure of the Invention] The method for producing foamed glass granules of the present invention includes a granulation step in which glass powder and an inorganic powder foaming agent are solidified with an adhesive to form granules, and the shaped granules are sized into spherical granules. A coating step of coating the spherical particles with an anti-blocking agent, and a heating step of rotating and sintering the coated spherical particles in a rotary kiln to obtain foamed glass particles. It is. [Example] An example of the method for producing expanded glass beads of the present invention will be described below in accordance with the process order. (1) Mix an inorganic powder blowing agent with the raw glass powder, add a 5% aqueous solution (23wt%) of PVA (polyvinyl alcohol), a type of water-soluble thickener, as an adhesive, and knead with a mixer. do. As the above glass powder, SiO ₂ (72.5wt%),
_Na2O (14.4wt%), CaO ( _10.2wt %), _Al2O3
(2.0wt%), BaO (0.6wt%), _K2O (0.2wt%),
A waste glass bottle having a composition of Fe ₂ O ₃ (0.1 wt%) is used which has been crushed into a 100 mesh pass (preferably a 200 mesh pass). The finer the glass powder is, the better the foaming properties described below will be, and the more uniform the foaming will be. In addition, as the above-mentioned foaming agent, it is finer than glass powder (preferably 300mesh pass) and moreover
Use something that releases decomposition gas at 900°C, such as CaCO ₃ powder (2.0wt%). (2) The kneaded material obtained by the above procedure is fed to a granulator and formed into granules with a diameter of about 2 mmφ and a length of about 5 mm. In the above granulator, the forming raw material is placed on a screen in which extrusion holes with a hole diameter of 2 mmφ are dispersed.
An extrusion type granulator is used which is configured to apply pressure from above using a pressing means to extrude the raw material from the extrusion hole and mold it into fine particles.
The hole diameter of the screen of this granulator is 0.5 to 5 mmφ depending on the diameter of the molded granules to be obtained.
Depending on the diameter of the hole, the pressure applied by the pressing means can range from 3 to 100.
It is desirable to set it within the range of Kg/ ^cm2 . (3) The molded granules obtained through the above granulation process are fed to a spherical sizing machine and sized for 1 minute at a rotational speed of 400 rpm. As the above-mentioned spherical granulator, a Marumerizer (trade name, manufactured by Fuji Paudal Co., Ltd.) with a plate diameter of 230 mm is used here. This spherical granulator has a configuration in which a rotating plate having an uneven surface (the uneven size is 0.5 to 5 mm) is provided on the bottom of a fixed cylindrical container, and the shaped granules housed in the cylindrical container are As the rotary plate rotates, a vortex motion is repeated between the outer wall of the cylindrical container and the plate, and the impact at this time causes the corners of the molded granules to be sheared or pressed, and the entire molded granule is sheared or pressed. deforms into an almost spherical shape. or,
The sheared powder generated during the above action is coalesced into the molded granules due to the adhesive contained in the molded granules, so no raw material powder remains unused.
The optimum values for the rotational speed and driving time of the above-mentioned rotating plate vary depending on the size of the molded granules to be subjected to grading, but should be within the range of approximately 200 to 1000 rpm and 30 seconds to 3 minutes. is preferred. Through this sizing step, the shaped granules are sized into spherical granules with a substantially uniform particle size. The particle size distribution is shown in Table 1. This table confirms that the spherical particles are concentrated and distributed within a predetermined narrow particle size range.

[Table] (4) Just before the end of the above sizing process, an antiblocking agent is added into the spherical sizing machine, and the surface of the resulting spherical granules is coated with the antiblocking agent. The above anti-blocking agents include fly ash, talc, clay, and other inorganic fine powders.
Quantity of substances with a melting point of 100℃ or higher: 1
~10wt% (preferably 4wt%) is used. (5) The coated spherical particles obtained through the above sizing process and coating process were heated at 100°C
After drying for 10 hours, it is continuously fed to a rotary kiln at a furnace temperature of 750°C and kept there for 7 minutes. Through this heating process, the supplied spherical particles are foamed and sintered while rolling in the rotary kiln (the blowing agent contained in the spherical particles generates decomposed gas), resulting in uniform foaming and low bulk density glass foam particles. is obtained. Furthermore, during this foaming and sintering, the spherical particles, which have been coated with an anti-blocking agent in advance, do not coalesce into a lump-like shape. Furthermore, there is no possibility that the particles will adhere to the rotary kiln wall. The above-mentioned drying process, which is carried out prior to foam sintering, is carried out in order to remove moisture contained in the used adhesive before sintering. This is effective in preventing explosions during sintering. Note that the drying conditions may be 100 to 400°C for 5 minutes or more. The rotary kiln used in the above heating step had an inner diameter of 106 mmφ, a length of 2 m, an inclination angle of 0.5 degrees, and a rotation speed of 24 rpm. If the residence time of the spherical particles in the furnace is too long, the final product will shrink.
It is preferable to set it within the range of 1 minute. Further, the temperature inside the rotary kiln is preferably 700 to 900°C. The various properties of the glass foam particles thus obtained are as follows. Bulk density: ρ = 0.18g/cm ³ (particle size 6mmφ) Crushing strength: 3.5Kg Water absorption: 10wt% (according to JIS-A-9511 measurement standards) The particle size of the above glass foam particles is determined by various factors during the process. By changing the conditions, it is possible to manufacture products with diameters ranging from 0.5 to 15 mmφ, and the characteristics of the product in this case are: Bulk density: ρ = 0.1 to 0.6 g/cm ³ Crush resistance: 0.5 kg or more Water absorption: It will be less than 20wt%. Note that the bulk density of the product, in other words, the foamability varies depending on the heating time (residence time of the spherical particles in the furnace) during the foaming sintering. The graph shown by the solid line in the figure shows the relationship between each heating time and the bulk density of the product in each case where only the heating time was successively changed in the above example. In the above example, CaCO ₃ powder (2.0wt%) was used as an inorganic powder blowing agent to be added to the raw material glass powder.
However, other carbonates, those that generate carbon dioxide gas when heated such as carbon powder, and those that generate a lot of decomposition gas at high temperatures (500 to 900℃) such as mirabilite, sodium bicarbonate, and calcium bicarbonate. Of course, it can also be applied. In addition, it is preferable that the amount of the foaming agent added is 0.5 to 10wt% based on the glass powder.If the amount added is less than this, the product will have poor foaming properties and a high bulk density. If the amount is too large, the bubbles generated will be destroyed by the foaming agent itself, resulting in the inconvenience that uniform cells will not be formed. In addition, in the above example, a PVA aqueous solution is used as an adhesive to harden the glass powder containing the blowing agent, but in addition, highly water-soluble thickeners such as carboxymethyl cellulose and starch, which are a type of water-soluble thickener, are used. Aqueous solutions of molecular materials are preferred. Aqueous solutions of these thickeners should be added in an amount of 0.5 to 10 wt% relative to water.
(optimally 2 to 5 wt%) is suitable as the above-mentioned pressure-sensitive adhesive. In addition, the amount of the above-mentioned adhesive added to the glass powder mixed with the foaming agent is 15 to 15%.
It is preferable to add 35 wt% (optimally 22 to 25 wt%); if the amount added is too small, the compacted granules will be easily destroyed in the sizing process, resulting in a large amount of powder; If it is too much, the molded granules tend to adhere to each other and form large lumps. Incidentally, in order to prevent the spherical particles from coalescing during heating and foaming, an inorganic powder such as talc is usually used as an anti-blocking agent added just before the end of the sizing step. However, when talc or the like is used, not only does the final product, the foamed glass particles, have the problem of dusting, but also during the heating and foaming process using a rotary kiln.
The anti-blocking agent such as talc falls off in the rotary kiln and prevents the rotation of the granules, which prevents uniform heating and impairs uniform foaming of the product. Therefore, in order to solve this problem, hard glass powders such as E and B-150 with high melting points (Table 2
The respective compositions are shown below) are preferably employed as antiblocking agents. In other words, although these hard glasses melt in the foaming temperature range (around 750°C) of the raw material granules (glass powder mixed with a blowing agent, hardened with an adhesive and sized), the raw material granules do not coalesce. The viscosity does not reach such a level that it sticks to the product, which improves the effect of preventing blocking and also prevents powder from sticking to the product.

[Table] In the above-mentioned examples, the characteristics of each product obtained when 5 wt% of the above hard glasses E, B-150 and talc were used as anti-blocking agents, and when no anti-blocking agents were added are shown. Shown in 3.

【table】

〔Effect of the invention〕

Since the method for producing foamed glass beads of the present invention has the above-mentioned structure, foamed glass beads with good foamability (that is, low bulk density), sufficient crushing strength, and excellent heat insulation properties can be produced with a narrow particle size distribution. It can be produced intensively and with high production efficiency by adjusting the particle size. As reference data for confirming the effect of the production method of the present invention, a comparative example will be shown below in which the same raw materials as in the above-mentioned example were used but the product was produced by a different method. [Comparative Example] Approximately 400 mesh of CaCO ₃ (2.0wt%) was added as a foaming agent to the same waste glass bottle powder as in the previous example, and a 5% aqueous solution of PVA (23wt%) was added as an adhesive and kneaded. . The obtained kneaded product was fed to the same granulator as in the example and granulated. As shown in Table 1 above, the particle size distribution at this time is a wide distribution that does not concentrate in a predetermined particle size range, and it can be seen that there are many particles with a small particle size close to that of a powder. The molded granules thus obtained were not sized into spherical shapes, but were subjected to the same drying and foaming sintering treatment as in the previous example to obtain foamed glass granules. A large number of coalescent particles were attached to the foamed glass particles, and the density was high (0.22 g/cc). In the above case where sizing treatment is not performed, the relationship between the heating time during foam sintering and the corresponding bulk density of each product is determined as follows:
This is shown by the dashed line graph in the figure. Comparing the results of the above-mentioned examples and the above-mentioned comparative examples, by sizing the raw material granules into spherical shapes, the foaming properties are improved (the bulk density is reduced) even with the same amount of foaming agent and foaming conditions. It can be confirmed that the particle size distribution of the product is also narrowed and that products with desired particle sizes can be manufactured with high production efficiency. In addition, since the raw material granules are granulated into spherical shapes, the raw material granules rotate smoothly during the foaming sintering process using a rotary kiln.
Foaming becomes uniform and coalescence is avoided.

[Brief explanation of drawings]

The figure is a graph showing the relationship between product bulk density and heating time during foam sintering, comparing foamed glass grains obtained by one example of the present invention with foamed glass grains obtained by other methods. be.

Claims (1)

[Scope of Claims] 1. A granulation step of solidifying glass powder and an inorganic powder foaming agent with an adhesive to form granules, a sizing step of sizing the molded granules into spherical granules, and a granulation step of sizing the spherical granules. 1. A method for producing foamed glass granules, comprising a coating step of coating the body with an antiblocking agent, and a heating step of rotary sintering the coated spherical granules in a rotary kiln to obtain foamed glass granules. 2. The method for producing foamed glass granules according to claim 1, wherein the coating step is carried out just before the end of the sizing step. 3. The method for producing foamed glass granules according to claim 1 or 2, wherein the granulation step is granulation by extrusion molding. 4. The method for manufacturing glass foam beads according to any one of claims 1 to 3, wherein the adhesive comprises a water-soluble thickener.