JPS61236621A - Production of foamed fine glass grain - Google Patents

Abstract

PURPOSE:To obtain efficiently a foamed glass grain which is small in the bulk density and has enough single grain collapsing strength by kneading the glass powder and the foaming agent powder, dressing the mixture to a spherical shape, coating a mold release agent thereon, thereafter drying, heating and foaming it. CONSTITUTION:The foaming agent powder such as CaCO3 is blended to the finely crushed glass powder and a binder such as polyvinyl alcohol is added thereto and kneaded. The kneaded material is dressed to a spherical granular body having a fine grain size by using a spherical grain dressing machine. A mold release agent such as the natural glass powder for the block prevention is coated on the surface of the spherical granular body. After drying the coated spherical granular body, it is heated in the inside of an electric furnace to foam the inside of the granular body. The following foamed fine glass grain is obtained which is nearly uniform in the size, has a fine and independent cell structure, is high in the degree of independent foam and small in the water absorption and excellent in the heat insulating properties.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to low-temperature cold insulators for liquefied natural gas storage tanks, lightweight insulation materials and aggregates for civil engineering and construction, extenders for plastics, and thickeners for paints. The present invention relates to a method for producing microscopic foamed glass particles that can be used as an enzyme immobilizing agent in the field of bioreactors.

[Prior art]

A method for manufacturing glass foam particles is disclosed in Japanese Patent Application Laid-open No. 58-983.
A manufacturing method disclosed in Publication No. 3 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, and
The second granules are formed into granules, and the surfaces of the second granules are further coated with a powdered mold release agent to form third granules, and finally, the third granules are heated to form glass foam granules.

As a result, glass foam particles having an outer shell made of a glass layer and having air bubbles inside are obtained.

However, in the case of the above conventional example, a pan-type granulator is used in the granulation process. In the method using this pan-shaped granulator, the binder is granulated while being sprayed and added, and the powder cores are gradually grown as the bread-shaped container is transferred to form granules. Therefore, according to this method, 8~
It takes a long time to obtain grains of 9 mesh (approximately 2 fins φ). In addition, the particle size distribution of the particles produced in the bread mold is highly inconsistent, and when aiming for 8 to 9 mesh, the distribution is wider than that of powder and 3 mesh, and if you try to obtain the desired particle size, the yield will be lower, and additional sieving steps will be 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 a blocking phenomenon. 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-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, it is not possible to miniaturize the foamed glass particles. 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. Moreover, if you try to sinter and foam the noodle-shaped raw material granules to obtain a uniformly foamed product, a low bulk density, and a multicellular structured granule with low water absorption,
The sintering process requires complicated condition management as in the conventional example. Furthermore, because measures such as applying an anti-blocking agent are not taken during the noodle granulation process, particles may coalesce together at the stage of foaming during 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.

Therefore, the applicant has previously proposed a method for manufacturing glass foam particles that have a low bulk density, sufficient crushing strength, excellent heat insulation properties, and can be manufactured at high production efficiency and at low cost. (Patent Application No. 59-254624). This method includes a granulation step in which glass powder and an inorganic powder unfoamed agent are solidified with an adhesive to form granules, a sizing step in which the formed granules are sized into spherical granules, and a granulation step in which the spherical granules are sized. The structure includes a coating step of coating an anti-blocking agent, and a heating step of rotary sintering the coated spherical particles in a rotary kiln to obtain foamed glass particles.

However, although the above manufacturing method is suitable for producing glass foam particles having a relatively large particle size of 0.5 mm or more, it is suitable for producing glass foam particles having a relatively large particle size of about 0.5 mm or less. It is extremely difficult to obtain fine foamed glass beads at a high yield, and this method is not suitable as a manufacturing method for obtaining fine foamed glass beads.

[Purpose 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 produce foamed glass grains with low bulk density, sufficient single grain crushing strength, and excellent heat insulation properties with high production efficiency. The object of the present invention is to provide a method for producing microfoamed glass beads that can be produced at low cost and that can produce uniform microfoamed foam beads at a high yield.

[Structure of the invention]

The method for producing micro foamed glass granules according to the present invention involves kneading glass powder and foaming agent powder using a binder, omitting the granulation step and directly sizing the particles into spherical shapes, and then After coating the surface of the molded particles with a mold release agent, it is dried.
The granules thus obtained are heated to cause the inside of the granules to foam, thereby obtaining micro foamed glass particles having a small particle size.

〔Example〕

An embodiment of the method for producing microscopic foamed glass particles according to the present invention will be described below in the order of its steps.

(1) Add foaming agent powder to glass powder as a raw material,
A binder is added to this and kneaded using a mixer.

As the glass powder, there are mainly used soda glass, borosilicate glass, aluminosilicate glass, etc., which have a relatively low softening point, such as plate glass and bottle glass. These glass powders are used in the form of fine powders that have been pulverized to about 400 to 500 mesh passes. The finer the glass powder, the better the foaming properties, and the more uniform the foaming.

The blowing agent powder is usually carbon blank (C), silicon carbide (SiC), calcium carbonate (C).
A powder such as aCO3) is used. These blowing agent powders are oxidized during the heating process and themselves generate carbon dioxide gas (Cog) through thermal decomposition. An agent that causes a thermal decomposition reaction of the blowing agent powder is used.

In addition, the glass powder has an appropriate viscosity in the temperature range where carbon dioxide gas is generated, which is an important factor in manufacturing expanded granules. If the viscosity of the glass is too high, cells of glass foam particles will be difficult to form, and if the viscosity is too low, the cells will easily break.

r7) Furthermore, as a binder, an aqueous solution of dextrin, polyvinyl alcohol, methylcellulose, etc. is used,
The type of binder is not limited to those mentioned above. The concentration of the binder solution is also important;
It is used within the range of t% to 10-t%, thereby making it possible to control the size of the resulting expanded beads within a certain range.

That is, if the concentration of the binder is too high, the particles tend to coalesce together in the sizing process, and on the other hand, if the concentration is too low, the granules cannot be maintained after drying.

For example, if a 2wt% polyvinyl alcohol aqueous solution is used and the amount of binder is 25% and 20% for the above raw materials, the yield of foamed beads having a particle size of 40 to 80 mesh will be 65%, and the particle size of 120 to 200 mesh will be obtained. Expanded granules with a yield of 35% are obtained. In addition, in a 5iyt% aqueous solution of polyvinyl alcohol, if the amount of binder is 25% and 20% with respect to the raw material, respectively, 20 to 30%
A yield of 55% mesh and 48% yield of 40-80 mesh is obtained.

The above-mentioned binder is added to the blended raw materials of the above-mentioned glass powder and blowing agent powder and kneaded, but the mixer used at this time is
Types of equipment used include kneaders, ribbon blenders, etc. It goes without saying that the type of mixer is not limited to those mentioned above.

Through the above-mentioned kneading step, glass powder and blowing agent powder adhere around the particles of the binder, resulting in a moist powder kneaded product.

(2) Next, the kneaded material obtained in the above step is directly fed to a spherical sizing machine without being applied to a granulator, and the kneaded material is sized into a spherical shape.

As the above-mentioned spherical granulating machine, widely used granulating machines can be used, but here we use the highly effective Marumerizer (manufactured by Fuji Paudal Co., Ltd.) or Super Mixer (manufactured by Yoda Seisakusho ■). are using.

The former marmerizer has a structure in which a rotating plate with an uneven surface is provided at the bottom of a fixed cylindrical container,
As the rotating plate rotates, the kneaded material supplied into the cylindrical container advances in the direction of the resultant force of the force rotating with the plate and the centrifugal force, and collides with the outer wall of the cylindrical container. The granulated kneaded material that hits the outer cylinder wall is once returned to the inner circumferential side, and then driven again to the outer circumferential side by the centrifugal force. The vortex motion is repeated.

The impact at this time shears or presses the corners of the kneaded material, shaping it into an almost spherical shape.On the other hand, as the swirling motion described above is repeated, particles of the binder become cores. The glass powder and the blowing agent powder combine and grow, and the resulting granules have a particle size of approximately 20 to 200'm larger than the glass powder and blowing agent powder.
It becomes a spherical shape of about sh. Since the sheared material generated during the above action is bonded to the granules by the binder, no raw material powder remains unused. The optimal values for the rotational speed and driving time of the rotating plate vary depending on the type of raw material powder to be sized, the type and concentration of the binder, the shape of the uneven surface of the rotating plate, etc., but in general, the rotational speed of the rotating plate The higher is set, the smaller the particle size of the sized product becomes.

The latter super mixer is equipped with a mixing arm and a high-speed chopper for finely dividing and grading, and grading is performed inside a ball container by the rotation of each, and the specially shaped mixing arm is located at the center of the container. While the raw material is stirred by the high-speed chopper, which is driven separately from this, the raw material is finely sized to a uniform particle size, and by repeating adhesion and dispersion, a finely sized product of about 20 to 200 mesh is obtained.

Through the above-mentioned sizing process, the kneaded material is sized into spherical particles having a substantially uniform, minute particle size. Its particle size is about 20-200m
They are about the size of esh and are minute particles.

(3) After completing the above sizing process, in order to prevent particles from blocking each other, a release agent is added to the surface of the resulting spherical granules to prevent blocking while the spherical sizing machine is being operated. Coat with mold release agent.

As the mold release agent, natural glass powder, talc, calcium carbonate powder, etc. are used. In this case, the amount of the release agent must be sufficient to uniformly coat the surface of the particles, and is preferably about 5 to 10 parts by weight based on the raw material powder.

(4) The coated spherical particles obtained through the above-mentioned sizing process and mold release agent coating process are further heated at 110°C x 6
The binder contained in the spherical particles is completely dried under conditions for more than an hour. 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 It goes without saying that the above drying conditions are not specifically limited.

(5) Finally, the dried spherical particles are heated and foamed in an electric furnace. This heating and foaming step may be carried out using a commonly used electric furnace, but in view of productivity, it is preferable to use a rotary kiln, a held-con kiln, a brush-contact kiln, or the like. The microspherical particles are linearly heated in an electric furnace kiln to the foaming temperature of the foaming agent contained in the particles, and after the particles become foamed particles, they are allowed to cool at room temperature. In addition, in the heating process using the rotary kiln, the supplied spherical particles are foamed and sintered (the foaming agent contained in the spherical particles generates decomposed gas) while rolling in the rotary kiln, resulting in uniform foaming and a high bulk density. Glass foam particles with low viscosity can be obtained. or,
During this foaming and sintering, the spherical particles whose spherical surfaces have been coated with a release agent in advance do not coalesce into a lump-like shape. Further, the particles do not adhere to the rotary kiln wall.

The rotary kiln used in the heating step has an inner diameter of 106 mφ, a length of 2 m, an inclination angle of 0.5 degrees, and a rotational speed of 24 r, p, n+, for example.

Furthermore, 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. Further, the temperature inside the rotary kiln is preferably 700 to 900°C.

As shown in the enlarged view of the structure in Figure 1, the microscopic foamed glass particles thus obtained are approximately uniform in size and have a very fine and independent cell structure. , has a high closed cell ratio, low water absorption, and excellent heat insulation properties. To express the characteristics of micro glass foam particles in concrete numbers, the crushing strength of a single particle of approximately 0.4 to 0.51 ■φ is 0.
．． 15 kg, the bulk density of foamed particles is 0.58 g/cc,
Also, the crushing strength of a single grain of 0.5~1.0 *Otoriφ is 0.19 kg, and the bulk density of the expanded grain is 0.51 g/c
It is c.

[Experiment example]

As a glass powder component, S i Oz (72,5w
t%), Naz O (14.4wt%), Ca0 (10
,2wt%), A 1203 (2,0wt%), Ba
O (0.6 wt%), Kg O (0.2 wt%), Fe
20+ (0.1 wt%) of waste glass powder (200 mesh or less) was mixed with calcium carbonate powder (approximately 400 mesh L2 parts by weight) as blowing agent powder.

Next, 20 parts by weight of an aqueous solution of polyvinyl alcohol (2 ivt%) as a binder was added to the above blended raw materials,
The mixture was kneaded for 2 minutes using a mixer Niegoo. This kneaded material is shaken, and after passing through a sieve that does not clog (for example, l Omesh), it is sized for 1 minute at 700 r, p, n+ using a spherical sizing machine Marumerizer (rotating plate diameter 200 x 1 ψ). After the spheroidizing process, obsidian powder (approximately 20 O
10 parts by weight of mesh) was added, and the spherical sizing machine was operated for 15 seconds to cover the surface of each particle with obsidian. This was dried at 110°C for 15 hours, and then
It was heated and fired for 12 minutes in a rotary kiln with a furnace temperature set at 770°C to decompose the foaming agent (Ca C03) contained in the sized particles and foam the micro glass particles.

The micro glass foam particles obtained as described above had a particle size distribution in the range of 20 to 20 Omesh, and the particle size, bulk density, single particle crushing strength, and closed cell ratio were as follows.

(Hereinafter, the margin) [Effects of the Invention] Since the method for producing microscopic foamed glass particles according to the present invention has the above-mentioned structure, it has excellent foamability and low bulk density, and also has sufficient single particle crushing strength. Since the closed cell ratio is high, foamed glass particles with low water absorption and excellent heat insulation properties can be obtained. In addition, since the kneaded material of the raw materials is directly shaped into spheres by passing it through a sizing machine without passing it through a granulator, it is possible to suppress the growth of particles by adding an appropriate amount of binder to the raw material powder.

As a result, the resulting glass foam particles are finely divided and have a particle diameter of 20 to 20 0mesh, and are substantially uniform in size. The micro glass foam particles obtained in this way can be used, for example, as a low-temperature cold insulator for liquefied natural gas storage tanks, or as lightweight insulation materials used in civil engineering and construction, by taking advantage of their small particle size. It is effectively used as a material for lumber and aggregate. Furthermore, by omitting the granulation step, productivity is improved and microscopic foamed glass particles can be efficiently produced.

[Brief explanation of drawings]

FIG. 1 is an enlarged view of the structure of microscopic foamed glass particles obtained by implementing the present invention.

Claims (1)

[Claims] 1. After kneading glass powder and blowing agent powder using a binder, they are directly sized into spherical particles through a spheroidizing process, and then the surface of the spheroidized particles is coated with a mold release agent and dried. A method for producing micro foamed glass beads in which micro foamed glass beads are obtained by subsequently heating the obtained granules and foaming the granules.