KR20020065043A - Manufacturing method of porous ceramic pellets by using double emulsion method - Google Patents

Abstract

PURPOSE: A method of manufacturing porous ceramic pellets by using double emulsion method is provided, which is possible to control pore size, porosity thereof by varying agitation rate and the amount of distilled water to be added. CONSTITUTION: The preparation method of porous ceramic pellet includes the steps of (S10) mixing 100 parts by weight of inorganic powder together with 20-35 parts by weight of distilled water and 3-8 parts by weight of viscosity controller; (S20) ball-milling above mixture so as to prepare a slurry having an average diameter of 5μm and a viscosity of 80 to 2000 cp; (S30) adding 0.15-1.50 parts by weight of a foaming agent in the slurry and then agitate the mixture for foaming; (S40) adding 1-3 parts by weight of a gelation agent such as aqueous epoxy resin in the foamy slurry, followed by slow agitation at 600 rpm; (S50) adding a nonvolatile dispersion media having a specific gravity of 0.7 to 0.8 such as paraffin and silicon oil, followed by slow agitation at 50-200 rpm for 30 to 60 min for pelletization ; and (S60) after drying the pellet, calcining the dried pellet up to 1100-1600deg.C at a rate of 1-3deg.C/min.

Description

Manufacturing method of porous ceramic pellets by using double emulsion method

The present invention relates to a method for producing porous ceramic pellets, and more particularly, to forming a slurry droplet by double-emulsifying a ceramic slurry, forming a gel after firing it, and then preparing a porous ceramic pellet to form a porous ceramic pellet. The present invention relates to a method of manufacturing porous ceramic pellets using a dual emulsion process, in which not only high porosity porous ceramic pellets are maintained but also micropores are formed by oil droplets.

Generally, the porous ceramic pellets form a plurality of pores therein. The mechanical and thermal properties of the porous ceramic pellets manufactured according to the pore size, shape, porosity, and pore continuity present in the porous ceramic pellets This is determined.

In particular, porous ceramic pellets are used as lightweight building materials within a specific range due to their small specific gravity and light weight due to the large number of pores artificially formed therein. The usage is increasing due to various uses.

In recent years, as the value of use of the microorganisms is attached to the porous ceramic pellets and used as a carrier for wastewater treatment and odor removal, the development of porous ceramic pellets and research on them are being actively conducted.

Representative methods of manufacturing the porous ceramic pellets include a vibration assembly method, a sol gel method, a spray drying method and the like.

The vibration assembly method is a method of inducing the powder to agglomerate by vibrating or rotating after applying appropriate moisture to the ceramic raw powder.

However, the above-described manufacturing method imparts mechanical vibration to form pellets, so that the pore structure of the surface of the pellets hardly appears, and the pore structure can not be controlled, and it is difficult to manufacture pellets having high porosity.

On the other hand, for a method of manufacturing a porous ceramic 10-1999-0058380 filed by the applicant of the present invention on December 16, 1999 (name of the invention: a method of manufacturing porous ceramics using a foam method, hereinafter referred to as "first application" The present invention is to provide a pellet by applying the method of manufacturing a ceramic posted in the prior application.

The present invention is to solve the problem of the pellets prepared by the conventional method described above to prevent clogging of the surface pore structure and to produce pellets of several mm size, as well as to control the porosity and pore size. The technical problem is to provide a method for producing porous ceramic pellets by a double emulsion method that is not limited to the type of starting material.

1 is a flow chart of a method for producing pellets according to the present invention.

Figure 2 is a size distribution of the pellets according to the stirring speed in the present invention.

Figure 3 is a photograph of the appearance of the pellet prepared according to the present invention.

Figure 4 is a photo of the internal pore structure of the pellets prepared according to the present invention.

In order to achieve the above technical problem, the flow of the method of manufacturing pellets is shown in FIG.

The present invention comprises the steps of adding 20 to 35 parts by weight of distilled water and 3 to 8 parts by weight of the viscosity modifier with respect to 100 parts by weight of the inorganic powder used as a ceramic (S10);

Grinding the mixture with a ball mill to prepare a slurry having an average particle size of 5 µm or less and a viscosity of 80 to 2000 cps (S20);

Putting the slurry into a stirrer and adding 0.15 to 1.50 parts by weight of a foaming agent and stirring at high speed to form bubbles of the slurry (S30);

Adding 1 to 3 parts by weight of a gelling agent to the foamed slurry to stir again at low speed (S40);

A dispersion medium injection step (S50) of injecting the mixed slurry into the dispersion medium and gelling the pellets while stirring at a low speed; And

Drying the gelled pellets is made as a firing step (S60) of firing by heating up to 1100 to 1600 ℃ at a rate of 1 to 3 ℃ / min.

20 to 35 parts by weight of distilled water and 3 to 8 parts by weight of the viscosity modifier are mixed with 100 parts by weight of the inorganic powder used as the ceramic, and the mixture is pulverized so that the average particle size of the raw material particles is 5 µm or less with a ball mill or a stirring mill. To prepare a slurry having a viscosity of 80 to 2000cp.

At this time, when the ceramic raw material to be used is not a powder but a bulk, it is preferable to grind the bulk raw material in advance in order to facilitate grinding, and as a usable ceramic raw material, silica including wastes such as fly ash or waste slime can be used. (SiO ₂ ), clay material, zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), mullite (mullite: 3Al ₂ O ₃ · 2SiO ₂ ), silicon carbide (SiC), cordierite (Mg ₂ Al ₃ ( Inorganic raw materials that can be calcined and solidified such as AlSi ₅ ) O ₁₈ ), carbon, and cement may be used, and two or more ceramic raw materials may be mixed and used.

Distilled water is added to maintain the distance between the ceramic raw material particles to enable the dispersion of the slurry as well as to enable the generation of bubbles. If the amount is less than 20 parts by weight, the viscosity of the slurry becomes too high, There is a problem in that the fluidity is lowered and bubbles are not properly formed by stirring, and when the content exceeds 35 parts by weight, the viscosity is low, so that the flowability of the slurry is good. It is preferable to add 20 to 35 parts by weight of distilled water since the problem occurs that the foam is easily broken and the foam is not properly formed.

In addition, the viscosity modifier is added to not only facilitate the mixing of distilled water and inorganic raw materials, but also to maintain a constant viscosity so that sufficient strength can be exhibited when the foam of the slurry is gelled. If the amount is less than 3 parts by weight, the strength of the molded body is lowered, which lowers the workability and also makes it difficult to mix the inorganic raw material with the distilled water. There is a problem that the amount of the viscosity modifier is added in excess of 8 parts by weight. In this case, the mixing of the inorganic raw material and the distilled water is easy, but the gelling time is shortened and the workability is lowered, so that molding is difficult. Therefore, it is preferable to add 3 to 8 parts by weight of the viscosity adjusting agent.

In this case, as the viscosity regulator, sodium hexametaphosphate, sodium polyacrylate, sodium polyacrylate, ammonium polyacrylate, polyethyleneimine, and the like may be added.

After adding water and a viscosity modifier to the ceramic raw material, it is pulverized so that the average particle size is 5 µm or less in a ball mill, together with the mediated grind. However, when the average particle size exceeds 5 µm, it takes a long time to fire. It is preferable to grind to 5 micrometers or less.

In this case, the formation of bubbles is greatly influenced by the viscosity of the slurry prepared by grinding, but if the viscosity is less than 80 cps, the viscosity is low and the stability of bubbles generated in the foaming process is deteriorated, resulting in a problem that foam is not formed. If it exceeds the viscosity is too high agitation is not properly made in the foaming process it is difficult to form a foam, so it is preferable to adjust the viscosity to 80 to 2000cp.

The slurry prepared as described above was added to a stirrer and 0.15 to 1.50 parts by weight of a foaming agent was added thereto, followed by stirring at high speed to form a foam of the slurry. Then, 1 to 3 parts by weight of a gelling agent was added to the slurry foam, followed by stirring at a low speed. Will be mixed.

At this time, the foaming agent is added to control the pore size of the porous material and to control the foaming rate. If the foaming agent is added below 0.15 parts by weight, the foam volume can be formed up to twice the initial volume, but it is difficult to form more than that. Also, there is a problem that the foaming process takes a long time due to the low rate of foam formation, and if the amount exceeds 1.50 parts by weight, the foam volume can be formed up to 5 times and the foam forming time is shortened. Since the manufacturing cost increases and the fluidity of the slurry bubbles decreases, the amount of the foaming agent is preferably added in an amount of 0.15 to 1.50 parts by weight.

In the above foaming agent, anionic surfactants and cationic surfactants having 10 to 17 carbon atoms in hydrophobic groups are used, and usable cationic surfactants are benzethonium chloride and stearyl trimethyl ammonium chloride. Cetyl trimethyl ammonium chloride and distearyl trimethyl ammonium chloride, and anionic surfactants include triethanloamine salt of lauoyl sarcosine, Sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine salt of lauryl sulfate polymethacrylate and sodium dodecylbenzene sulfonate sulfonate) There.

Since the size of the bubble and the stability of the slurry foam is different depending on the type of the surfactant used as the foaming agent, the pore size of the final product can be adjusted by changing the type of surfactant.

When foaming agent is added together with the slurry and high-speed agitation is performed at 1200 rpm or more in a stirrer, a foam layer of the slurry is formed, and the stirring is about 4 times the volume of the slurry foam compared to the volume before stirring. When it is formed, the stirring is stopped. Since the volume of the slurry foam is determined according to the stirring time as described above, the porosity can be adjusted to control the porosity of the product to be manufactured.

In the above, a stirrer for generating bubbles at a high speed stirring was used a general domestic or industrial stirrer, the number of rotary blades of the stirrer can be appropriately adjusted in consideration of the size of the stirrer and the volume of the slurry to be formed.

As described above, high-speed agitation has an advantage that pore formation is possible without using a method of forming a pore by adding a conventional sponge or a flammable additive and firing the same.

In addition, in the present invention, since the pores are formed before firing, the pore size can be increased as well as the pore size can be adjusted by adjusting the volume of the slurry foam during stirring.

The gelling agent is added to the foam formed in a constant volume as described above, wherein the gelling agent serves to maintain the form of the foam formed by gelling the slurry by reacting with the viscosity control agent.

In particular, when the amount of the gelling agent added is less than 1.0 part by weight, too much time is required for the gel molding, and the strength of the molded body is lowered. When the amount of the gelling agent is added more than 3.0 parts by weight, the gelling time is too fast, and molding is impossible. It is preferable that the amount of the gelling agent is added in an amount of 1.0 to 3.0 parts by weight, and in the present invention, a water-soluble epoxy resin is used as the gelling agent so that the foam generated when the gelling agent is added is not destroyed.

The mixture to which the gelling agent is added is stirred at low speed so that the gelling agent is evenly mixed so that the slurry can be gelled. At this time, the slow stirring is stirred at a speed of 600 rpm.

When the slurry foam to which the gelling agent is added is injected into the dispersion medium and stirred at a low speed at a constant speed, the slurry droplets are present in the form of pellets in the dispersion medium. The slurry is continuously stirred for about 30 to 60 minutes, which is the time taken for the slurry to gel. do. During stirring, the size of the resulting slurry is varied by varying the size of the slurry droplets to control the size of the resulting pellets. In other words, as the stirring speed increases, the shear stress acting on the slurry droplets increases, thereby decreasing the size of the droplets, thereby controlling the diameter of the pellet generated by controlling the stirring speed.

As the dispersion medium, a nonvolatile dispersion medium having a specific gravity of 0.7 to 0.8 may be used. Such a dispersion medium may include paraffin, silicon oil, and the like.

After gelling the slurry droplets in the dispersion medium, the slurry is dried at 80 ° C. for about 48 hours in a drier and calcined by heating up to 1100 ° C. to 1600 ° C. at a rate of 1 to 3 ° C./min.

At this time, if the temperature rises rapidly during the calcination process, the gas generated by the combustion of the gelling agent expands rapidly and cracks are generated. Therefore, the temperature increase rate is preferably 1 to 3 ° C./min. It is preferable to bake by adjusting suitably according to a raw material.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

<Example 1>

Polyethyleneimine was mixed with 100 parts by weight of the mullite, which is a ceramic raw material, with distilled water and a viscosity modifier in the weight parts shown in Table 1 below, and then the raw particles were pulverized in an agitated mill to have an average particle size of about 3 μm. The slurry was added to a stirrer, and sodium lauryl sulfate was added to the foaming agent in parts by weight shown in Table 1, followed by high speed stirring at 1200 rpm to form a foam of the slurry. Then, 2 parts by weight of an epoxy resin was added to the slurry foam, followed by 600 rpm. After stirring at low speed, the mixture was injected into paraffin as a dispersion medium, and then stirred at a low speed of about 50 to 200 rpm during the time of gelling of the gelling agent, followed by pulling up, raising the temperature at a rate of 2 ° C./min, and baking at 1450 ° C. for 360 minutes to make porous ceramic pellets. Was prepared, and the average group of the pellets by the following method using the prepared porous ceramic pellets Shows the shape of the produced showed a size distribution of the pellets according to the stirring speed of the double emulsion by measuring the deviation size and the specific surface area and were shown in Table 1 in FIG. 2 pellets in Fig.

-Average pore size and pore size deviation-

An image analysis system was used to measure the pore size distribution of porous ceramic pellets with foam-type pore structure. The image analysis system uses a zoom camera or an electron microscope to measure the pore size using the surface photograph of the porous ceramics. After the surface photographs were obtained, the average size and the deviation were calculated by measuring about 1000 pore sizes for each sample using an image analysis system.

-Pellet size and specific surface area-

The size distribution of the pellets was measured by standard sieving analysis. The specific surface area of the pellets was measured on the basis of the BET isothermal equation (Isothermal adsorption equation presented by Brunauer, Emmet and Teller) using nitrogen gas.

<Example 2>

A porous ceramic pellet was prepared in the same manner as in Example 1 except that benzethonium chloride was added as a foaming agent in the ratio shown in Table 1 below, and then the porous ceramic pellets prepared above were the same as in Example 1. The average pore size, pore size deviation, and specific surface area were measured by the method and are shown in Table 1 below.

division water Viscosity Modifier Foam Average pore size (㎛) Pore size deviation (㎛) Specific surface area (m ² / g) Example 1 15 4.7 0.31 61 52.3 2.4 20 4.7 0.31 70 40.3 2.9 30 4.7 0.31 98 34.7 3.2 35 4.7 0.31 130 35.2 3.2 40 4.7 0.31 203 45.7 3.2 30 2.0 0.31 72 42.8 2.8 30 5.0 0.31 99 35.1 3.3 30 9.0 0.31 111 41.7 3.1 30 4.7 0.10 73 39.7 2.8 30 4.7 0.50 98 32.9 3.5 30 4.7 1.67 125 37.4 3.0 Example 2 15 4.7 0.31 124 45.2 2.6 30 4.7 0.31 201 65.2 3.5 40 4.7 0.31 310 73.5 3.2 30 2.0 0.31 117 77.3 2.9 30 5.0 0.31 200 69.4 3.3 30 9.0 0.31 196 73.5 2.9 30 4.7 0.10 148 78.0 3.0 30 4.7 0.48 209 68.4 3.3 30 4.7 1.67 211 71.9 3.2

Since the present invention forms pellets in the dispersion medium, it does not damage the pore structure of the surface of the pellets and can produce porous pellets of high porosity as well as control the size of the pellets by adjusting the stirring speed, and it is configured according to the amount of distilled water added. Because the size of the bubble can be adjusted, the pore structure can be maintained, high porosity can be maintained, pellets of various sizes can be prepared, and pellets used in various fields can be manufactured by changing the pore size and porosity. It works.

Claims (3)

Generating a mixture by adding 20 to 35 parts by weight of distilled water and 3 to 8 parts by weight of a viscosity modifier based on 100 parts by weight of the inorganic powder used as the ceramic (S10); Grinding the mixture with a ball mill to prepare a slurry having an average particle size of 5 µm or less and a viscosity of 80 to 2000 cps (S20); Putting the slurry into a stirrer and adding 0.15 to 1.50 parts by weight of a foaming agent and stirring at high speed to form bubbles of the slurry (S30); Adding 1 to 3 parts by weight of a gelling agent to the foamed slurry to stir again at low speed (S40); A dispersion medium injection step (S50) of injecting the mixed slurry into the dispersion medium and gelling the pellets while stirring at a low speed; And Drying the gelled pellets and heating up to 1100 to 1600 ℃ at a rate of 1 to 3 ℃ / min firing step (S60), characterized in that made of a porous ceramic pellets using a double emulsion method. The method of claim 1, wherein the dispersion medium in the step S50 is a non-volatile paraffin (paraffin) or silicon oil (silicon oil) having a specific gravity of 0.7 to 0.8. The method of claim 1, wherein in the step S50, the stirring speed is 50 to 200 rpm and the stirring time is 30 minutes to 60 minutes.