JPS61132538A - Production of foamed glass particle - Google Patents

Abstract

PURPOSE:To obtain foamed glass particles having low bulk density, sufficiently high crush strength and excellent heat-insulation, at a low cost, by forming glass powder and powdery inorganic foaming agent with a binder in the foam of spheres, coating the spheres with an anti-blocking agent, and sintering under rotation. CONSTITUTION:Glass powder and powdery inorganic foaming agent are bonded with a binder in the form of particles, and reformed to spherical particles. The spherical particles are coated with an anti-blocking agent, and then heated in a rotary kiln under rotation to obtain the objective foamed glass particles. The powdery inorganic foaming agent is e.g. CaCO3 powder, Glauber's salt, sodium bicarbonate, etc., and its amount is preferably 0.5-10wt% based on the glass powder. The binder is preferably an aqueous solution of PVA, an aqueous solution of carboxymethylcellulose, etc., having a concentration of 0.5-10wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing glass foam particles used as heat insulating materials, aggregates, etc. in construction and other fields.

[Prior art]

As a conventional example of a method for producing this type of foamed glass beads, a method disclosed in Japanese Patent Application Laid-open No. 58-9833 is known. In this conventional example, a first raw material powder mainly composed of a first glass powder and a blowing agent powder is solidified with a binder to form a first granule, and a second glass powder containing no blowing agent is used as the main component. A second raw material powder as a component is coated on the surface of the first granule with a binder to form a second granule, and a powdered mold release agent is further coated on the surface of the second granule to form a third granule. and finally heat the third granular body to form glass foam granules,
As a result, glass foam particles having an outer shell made of a glass layer and an interior having a multicellular structure are obtained.

However, in the case of the above-mentioned conventional example, a pan-type granulator is used in the granulation process, and in this method, the powder is grown into grains by transferring the bread-type container.
It takes a long time to obtain grains of ~9 mesh (approximately 2 wmφ). In addition, the particle size distribution of the particles produced in the bread mold has a wide range from powder to 3+5 mesh (when aiming at 8 to 9 mesh), and if you try to obtain the desired particle size, the yield will be Moreover, a further sieving process is required. In addition, since the surface of the raw material granules exhibits viscosity due to the binder, coalescence of particles occurs during the growth process of the particles in the granulation process, resulting in blocking. As described above, the above 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-mentioned conventional example, as disclosed in Japanese Patent Application Laid-Open No. 53-142424, a mixture of glass particles and a blowing agent is granulated into noodle shapes, which are heated to form cellular glass beads. In the further cooling process, select the properties and amount of blowing agent, heating temperature, and heating time.
A method for producing foamed glass particles having a multicellular structure with low bulk density and low water absorption is also known.

However, in the case of this conventional example, the
I can't get any grains. Furthermore, since the raw material granules are noodle-shaped, the bonding force within the granules is uneven, 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 we try to sinter and foam noodle-shaped raw material particles to obtain a uniformly foamed product, a low bulk 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 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 glass foam particles having a uniform shape and a low bulk density.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned problems in the conventional examples, and it is an object of the present invention to produce foamed glass granules with low bulk density, sufficient crush resistance, and excellent heat insulation properties at low cost and with high production efficiency. The object of the present invention is to provide a method for producing foamed glass beads that can be used to produce foamed glass beads.

[First aspect 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 arranged into spherical granules. It is characterized by comprising a sizing step of granulating, a coating step of coating the spherical granules with an anti-blocking agent, and a heating step of rotary sintering the coated spherical granules in a rotary kiln to obtain foamed glass granules. It is something.

〔Example〕

An embodiment of the method for producing foamed glass beads of the present invention will be described below in accordance with its process order.

(1) Add an inorganic powder blowing agent to the raw glass powder,
PVA, a type of water-soluble thickener, is used as an adhesive.
(Polyvinyl alcohol) 5% aqueous solution (23 wt%) is added and kneaded using a mixer.

As the glass powder, Sing (72.5wt%)
, NazO (14,4 wt%), CaO (10,2
wt%), Ah03 (2,0wt%), BaO (0,
6wt%), KzO (0,2wt%), FezO
10 waste glass bottles with a composition of z (0.1 wt%)
Use a material that has been pulverized to 0 mesh pass (preferably 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.

Further, as the above-mentioned foaming agent, one that is finer than glass powder (preferably 300 mesh pass) and emits decomposed gas at 500 to 900°C, such as C'aCO.

Powder (2,0 wt%) is used.

(2) The kneaded material obtained by the above procedure is fed to a granulator and formed into granules with a diameter of about 2 φ and a length of about 5 ts.

The above-mentioned granulator is configured such that the forming raw material is placed on a screen in which extrusion holes with a hole diameter of 2 mφ are dispersed, and pressure is applied from above by a pressing means to extrude the raw material from the extrusion holes and form it into fine particles. A configured extrusion mold granulator is used. The hole diameter of the screen of this granulator can be arbitrarily selected, such as 0.5 to 5 flφ, depending on the diameter of the molded granules to be obtained, and the pressure It is desirable to set the pressure by means in the range of 3 to 100 kg/c1i.

(3) The molded granules obtained by the above granulation process were fed to a spherical granulator, and the rotation speed was 40 Or, p, m.

Sort the particles for 1 minute.

As the above-mentioned spherical granulating machine, here the plate diameter is 230 mm.
Asφ Marmerizer (trade name, manufactured by Fuji Paudal Co., Ltd.) is used. This spherical granulator has an uneven surface (the uneven size is 0.5 to 5 m) on the bottom of a fixed cylindrical container.
), in which the molded granules housed in the cylindrical container are rotated, and as the rotary plate is driven to rotate, a vortex flow is generated between the outer wall of the cylindrical container and the plate. The motion is repeated, and the resulting impact shears or presses the corners of the molded granules, deforming them into a substantially spherical shape as a whole. In addition, the shear powder generated during the above action is
Since the adhesive contained in the molded granules is used to bind the raw material powder to the molded granules, no raw material powder remains unused. The optimum values for the rotation speed and driving time of the above rotating plate are as follows:
Although it varies depending on the size of the shaped granules to be subjected to sizing, approximately 200 to 1000 r, p, m, and 30 seconds to 3
It is preferable to set it within the range of minutes.

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 1 (4) Just before the end of the sizing process, an antiblocking agent is added into the spherical sizing machine to coat the surface of the resulting spherical granules with the antiblocking agent.

As the above-mentioned block inhibitor, flyafshe, talc, clay, or other inorganic fine powder having a melting point of 1000°C or higher is used in an amount of 1 to 19w1% (preferably 4wt%).

(5) After drying the coated spherical particles obtained through the above-mentioned sizing step and coating step under the conditions of 100° C. 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 performed prior to foam sintering, is performed to remove moisture contained in the adhesive used before sintering, and is intended to shorten the sintering time and remove moisture contained in the adhesive. 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 for the above heating process has an inner diameter of 1
06 cabinet φ, length 2m, inclination angle 0.5 degrees, rotation speed 24r
, p, m. If the residence time of the spherical particles in the furnace is too long, the final product will shrink, so it is desirable that the residence time be within the range of 3 to 20 minutes. Also, the temperature inside the rotary kiln is 700.
~900°C is desirable.

The various properties of the glass foam particles thus obtained are as follows.

Bulk density: ρ-0.18 g/cd (particle size 6 mm) crushing strength: 3.5 kg Water absorption: 10 wt% (according to the measurement standard of J I 5-A-951i) The particle size of the above glass foam particles is By changing the various conditions during the process, it is possible to manufacture products with diameters ranging from 0.5 to 15 mφ, and the characteristics of the product in this case are bulk density: ρ = 0.1 to 0.6 g/cal, crushing strength, :0
．． Water absorption of 5 kg or more: 20 wt% or less.

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, CaCO3 powder (2, Qwt%) was used as an inorganic powder blowing agent blended with the raw material glass powder, but other carbonates and carbon powders that generate carbon dioxide gas when heated are also used. It goes without saying that materials that generate a large amount of decomposition gas at high temperatures (500 to 900° C.), such as glauber's salt, sodium bicarbonate, and calcium bicarbonate, can also be used. Also, the amount of the foaming agent added is 0.5 to the glass powder.
~lQwt% is suitable; if the amount added is less than this, the product will have poor foaming properties and a high bulk density; on the other hand, if the amount added is too large, the bubbles generated will be destroyed by the foaming agent itself. This causes the inconvenience that uniform cells cannot be formed.

In addition, in the above example, a PVA aqueous solution is used as an adhesive for solidifying the glass powder containing the blowing agent, but
- In addition to the above, an aqueous solution of a water-soluble polymeric material such as carboxymethyl cellulose, which is a type of water-soluble thickener, or starch is suitable. An aqueous solution of these thickeners in an amount of 0.5 to LOwt% (optimally 2 to 5 wt%) relative to water is suitable as the adhesive. The amount of the adhesive added to the glass powder mixed with the blowing agent was 15
It is preferable to set the amount to ~35 wt% (optimally 22 to 25 wt%); if the amount added is too small, the molded granules will be easily destroyed in the sizing process, resulting in a large amount of powder; If the amount is too large, the molded particles tend to adhere to each other and form large lumps.

In order to prevent 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 granules, have the problem of powder adhesion, but also the anti-blocking agent such as talc falls off in the rotary kiln during the heat foaming process. This prevents the rotation of the granules and prevents uniform heating, which impairs the uniform foaming of the product.

Therefore, in order to solve this problem, it is preferable to use hard glass powders such as E and B-150, which have high melting points (their compositions are shown in Table 2), as an anti-blocking agent. 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, solidified with an adhesive and sized), the raw material granules do not coalesce together. The viscosity does not reach such a level that it sticks to the product, which improves the blocking prevention effect and also prevents the product from getting powdered.

Table 2 Table 3 shows the properties of the products obtained in the above-mentioned examples when 5 wt% of the hard glasses E, B-150 and talc were used as block inhibitors, and when no block inhibitor was added at all. Shown below.

(Margins below) Table 3 As is clear from the above results, when talc is used as an anti-blocking agent, the amount of falling powder is 1.5 wt%, while hard glass E and B-150 powders are prevented from being blocked. When used as an agent, it can completely prevent powder shedding caused by anti-blocking agents. In addition, the amount of blocking is about the same as when talc is used as an anti-blocking agent.
This is much improved compared to the case where no block inhibitor is added.

〔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 as desired. 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 Ca C03 (2.0 wt%) was added to the same waste glass bottle powder as in the above example as a blowing agent.
and a 5% aqueous solution of PVA (23
wt%) was added 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 bulk density was also 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.
The particle size distribution of the product is also narrow (we can confirm that it is possible to manufacture products with the desired particle size with high production efficiency. Also, since the raw material particles are granulated into spherical shapes, it is possible to produce products with a narrow particle size distribution). , raw material granules rotate smoothly,
Foaming becomes uniform and coalescence is avoided.

[Brief explanation of the drawing]

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)

[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; A method for producing foamed glass granules, comprising a coating step of coating the granules with an anti-blocking agent, and a heating step of rotating and 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.