KR20160127540A - Manufacturing method of flatsheet ceramic membrane - Google Patents

Abstract

The present invention relates to a method for manufacturing a flat membrane type ceramic separator. The method includes the steps of forming a semi-solid ceramic molding, and drying and sintering the semi-solid molding, wherein the step of forming the semi-solid ceramic molding comprises forming a ceramic slurry And is carried out by a method of impregnating and laminating using a pore-forming aid. Such a manufacturing method can advantageously produce a flat membrane type ceramic separator with greatly improved porosity and workability at a low cost and a high yield by a simple process.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing a flat membrane-

The present invention relates to a method for manufacturing a ceramic membrane, and more particularly, to a method for manufacturing a flat membrane type ceramic membrane.

In recent years, solid-liquid separation processes are required in various industrial fields such as environmental wastewater treatment, water treatment, waste oil treatment, chemical, food, medicine, refinery and bio. Particularly, in the field of environmental wastewater treatment and water treatment, such solid-liquid separation process is becoming more important with respect to water environment improvement and water reuse.

In the above-mentioned solid-liquid separation process, separation membranes having various shapes and materials are utilized. Particularly, since the ceramic separators have excellent heat resistance, chemical resistance, abrasion resistance, and the like, It is attracting attention.

Such a ceramic separator is classified into an in-out type and an out-in type according to the filtration direction. The inlet-outlet type is a method in which the external influent flows into the interior of the separation membrane, is filtered, and then is discharged to the outside of the separation membrane. The inlet-type ceramic separation membrane has a tubular structure having a simple structure and a honeycomb- , Generally operated in an orthogonal cross-flow manner. On the other hand, the out-in type is a method in which the external influent is introduced from the outside of the separator, filtered and discharged through the inside of the separator. The out-in type ceramic separator is manufactured in the form of a plate of several millimeters thick, Flatsheet type, and is generally operated in a dead-end manner. Since the outer surface of the flat membrane-type ceramic separator is a filtration surface, it is easy to clean the surface and has a small specific surface area, resulting in a small filtration surface per unit volume.

Conventionally, most ceramic separators including flat membrane type ceramic separators are manufactured by an extrusion method. That is, the ceramic raw material is manufactured by a series of processes such as mixing and extruding a ceramic raw material, a binder and a solvent, drying and sintering the ceramic raw material, forming a coating film on the surface, and drying and sintering the coating film.

When the ceramic separator is manufactured by such an extrusion method, the relative density of the sintered ceramic separator is 50% or more and the porosity of the sintered ceramic separator is about 50% There is a problem that the permeability to the ceramic separator increases in the process.

In this case, in order to lower the permeability, attempts have been made to control the content of the binder mixed with the ceramic raw material. However, there are limitations. In order to increase the porosity of the ceramic membrane, the method using the porosity- There is a difficult problem to be solved.

In addition, after the extrusion, the drying speed in the inside and outside of the material changes during the drying process, so that the shrinkage cracks easily occur and the cracks easily occur due to the difference in sintering shrinkage rate during the sintering process, . It is difficult to control the process conditions during the drying and sintering process because the size of the ceramic separator is increased due to the increase in the yield of the product due to the occurrence of cracks.

Also, there is a problem that the cost of the product increases due to an increase in the equipment cost accompanying the extrusion process depending on the size of the ceramic separator.

An object of the present invention is to provide a method for manufacturing a flat membrane type ceramic separator having improved porosity and processability at a low cost and a high yield by a simple process.

The gist of the present invention regarding the recognition of the above-mentioned problems and the solution means based on the above is as follows.

(1) forming a semi-solid ceramic formed body, and drying and sintering the semi-solid formed body, wherein the step of forming the semi-solid ceramic formed body comprises the steps of forming a ceramic slurry by pore formation Wherein the impregnating and laminating are carried out by using an impregnation method.

(2) The method for manufacturing a flat film-type ceramic separator according to the above (1), further comprising the step of forming a surface coating film after the sintering.

(3) The ceramic slurry may contain, by weight, 55 to 60% by weight of alumina powder, silica powder or mixed powder thereof; 15 to 20% by weight binder; 0 to 0.1% by weight of defoamer; 0 to 1% by weight of a dispersant; And the remainder is water. The method for manufacturing a ceramic separation membrane according to the above (1)

(4) The process for producing a flat membrane-type ceramic separator according to the above (1), wherein the impregnation and laminating process is performed by a rolling or scraping method using a pore-forming aid.

(5) The method of manufacturing a flat film-type separation membrane according to (1), further comprising degreasing the semi-solid compact after drying.

(6) The method for manufacturing a flat film-type ceramic separator according to (2), further comprising machining the surface coating film before forming the surface coating film.

The method for producing a flat membrane type ceramic separator according to the present invention comprises the steps of impregnating and laminating a ceramic slurry with controlled viscosity and content using a fiber pore forming aid and then removing the pore forming agent through drying, The porosity of the ceramic separation membrane can be greatly improved and the permeability of the membrane can be reduced.

Further, the manufacturing method according to the present invention improves workability and dimensional accuracy of the processed product because a large amount of pores are contained in the ceramic separator main body.

In addition, the production method according to the present invention can effectively improve the problem that the product yield is lowered by conventional shrinkage cracks without complicated process control by uniformly controlling the shrinkage of the ceramic slurry in the drying and sintering process of the fiber pore- have.

In addition, since the manufacturing method according to the present invention does not require an expensive facility such as an extrusion facility, the cost of the product can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram of a method for manufacturing a flat membrane type ceramic separator according to an embodiment of the present invention; FIG.
FIG. 2 is an electron micrograph of a pore-forming auxiliary used in the production of the flat membrane-type ceramic membrane body.
3 is an electron micrograph of a surface and a cross section of a flat membrane-type ceramic separator having a surface coating film formed thereon.
FIG. 4 is a graph showing pore analysis of a flat membrane-type ceramic separator according to an embodiment of the present invention. FIG.
5 is a photograph of a product of a flat membrane type ceramic separator fabricated according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as including, it is understood that it can include other elements, not excluding other elements, unless the context clearly indicates otherwise. In addition, when an element is referred to as being 'provided', is included or included, it is not necessarily a component adopted in connection with the solution of the present invention, but it is arbitrarily or advantageously adopted .

1 is a process diagram for a method of manufacturing a flat-film-type ceramic separator according to the present invention. The manufacturing method includes a step (S10) of manufacturing a separator main body and a step (S20) of forming a coating layer selectively on the separator main body surface.

The step of preparing the separator main body is a step of forming a sufficient porosity on the inner surface of the separator main body, and the ceramic slurry is prepared by impregnating and laminating the ceramic slurry with controlled viscosity and content by using a pore forming auxiliary agent. That is, the ceramic separator main body having sufficient porosity can be manufactured by drying and sintering the semi-solid formed body impregnated and laminated with the ceramic slurry.

First, a ceramic slurry is prepared (S110). The ceramic slurry contains 55 to 60% by weight of a ceramic powder; 15 to 20% by weight binder; 0 to 0.1% by weight of defoamer; 0 to 1% by weight of a dispersant; And the remainder being water. In this case, the ceramic slurry can be produced by performing ball milling for more than 24 hours.

The ceramic powder may be a material to be used as a raw material of the separation membrane. Preferably, the ceramic powder may include alumina powder having a purity of 99% or more and an average particle size of 5 탆, a silica powder having a purity of 99% and an average particle size smaller than that of alumina, or a mixed powder thereof have.

The binder serves to secure a dry strength at room temperature of the molded article, and may be selected from, for example, a methylcellulose-based binder. When the content of the binder is less than 15% by weight, the strength of the formed article is lowered, which is not preferable.

Next, a semi-solid compact is produced (S120). The semi-solid compact may be prepared by uniformly impregnating the ceramic slurry between the fibrous phases of the unit pore-forming auxiliary having a predetermined thickness and sequentially laminating the ceramics slurry to a desired thickness of the unit pore-forming auxiliary impregnated with the ceramic slurry.

The method of impregnating and laminating the ceramic slurry with the pore forming auxiliary agent is effective in that a small amount of the ceramic slurry is applied to the pore forming auxiliary agent and adhered to each other while being pressurized by rolling or scraping in a mutually overlapped state. It is possible to produce a semi-solid molded article having a thickness of 1 mm.

2 is an electron micrograph of a pore-forming auxiliary for impregnating the ceramic slurry with a semi-solid formed product. Such pore-forming auxiliaries may be composed of fibrous polymeric materials such as, for example, PET or PP Nylon, whose surfaces are irregularly entangled with fibers having diameters of about 10 to 20 μm, voids are observed between the fibers 2), and the fibers arranged in the plane direction can be identified on the cross section (right photograph in FIG. 2).

In this case, when the ceramic slurry is impregnated with the fibrous pore forming agent as shown in Fig. 2, ceramic powder is filled in the void space between the fibers, and the fiber pore forming agent is removed in the following degreasing and / The ceramic powder is sintered to produce a porous ceramic separator main body in which a pore tunnel is formed in the surface direction.

Next, the semi-solid shaped article in which the ceramic slurry-impregnated pore forming assistant is laminated to a desired thickness is dried (S130). The drying process is firstly dried at room temperature for 24 hours or more, and then the secondary drying is sufficiently performed at 120 ° C for 24 hours or more. In order to suppress the warpage of the semi-solid molded body during the drying process, a suitable load can be applied as required, with the dry plate capable of ventilation being attached to the upper and lower surfaces of the semi-solid molded body.

Next, degreasing and sintering are performed in a state where the dried ceramic separator main body is accommodated in the electric furnace (S140, S150).

The degreasing process (S140) is preferably a process for pyrolyzing and removing the additive such as a binder, a defoaming agent and a dispersant contained in the ceramic slurry and the fibrous pore forming agent, and is preferably performed at about 600 ° C or lower for 12 hours or more.

The sintering process (S150) may vary depending on the particle size and distribution of the alumina, the content and the particle size of the silica, and the composition and content of the sintering auxiliary agent selectively added. The sintering process (S150) may be performed at 1200 ° C to 1300 ° C for 2 to 6 hours .

Next, the sintered ceramic separator main body can be processed into a desired thickness and shape (S160). In this case, since the sintered ceramic body contains a large amount of pores, the workability is very excellent, so that the shape processing can be performed by simple machining such as a polishing step. As shown in FIG. 5, the flat membrane type ceramic separator according to the present invention can be processed into various shapes due to excellent processability.

Next, after the manufacturing process of the ceramic separator main body is completed, a process of forming a coating film on the main body surface is performed (S20). The process of forming the coating film on the surface is carried out through the application of a coating film, drying, degreasing and sintering.

The coating layer coating process (S210) is not particularly limited, but is preferably performed by a screen printing process in terms of coating a large area with an accurate thickness and a relatively low processing cost.

In this case, the coating liquid is prepared in the form of a ceramic slurry, and it is preferable to use a ceramic powder having a uniform particle size equal to or about twice the desired surface pore size. Component of the coating liquid is alumina or silica or a mixed powder thereof as a ceramic powder and Terpineol, Buty carbitol or a mixed solution thereof as a solvent, and 50 to 60% by weight of a ceramic powder; 1 to 3% by weight binder; 0 to 1% by weight of a dispersant; And the remainder may be composed of a solvent.

The viscosity of the coating liquid is preferably controlled so that the coating liquid can be uniformly applied to the surface of the body without being easily absorbed by the body of the ceramic separator during the screen printing process. By controlling the content of the ceramic powder and the content of the binder and the solvent, .

The thickness of the applied coating film is related to the water permeability and can be controlled by the mesh conditions of the screen printing and the number of printing, and is preferably controlled to about 10 mu m to 100 mu m.

Next, the coating film is sufficiently dried (S220) at 120 deg. C for 6 hours or more, and then degreasing (S230) and sintering (S240) are performed on the coating film.

In this case, the degreasing process for the coating film is preferably performed in accordance with the characteristics of the binder used in the coating liquid, similar to the degreasing process for the ceramic separator main body.

Meanwhile, the sintering process for the coating film is preferably performed at a temperature lower than the sintering temperature of the separator main body by about 100 ° C or more to suppress deformation or shrinkage of the ceramic separator main body.

In this case, since the ceramic powder contained in the coating liquid has a particle size smaller than that of the ceramic powder contained in the ceramic slurry used for producing the ceramic body, the sintering temperature can be lowered. However, In order to improve the dimensional accuracy of the final product, it is necessary to sufficiently lower the sintering temperature of the coating film by adding a sintering auxiliary agent to the coating liquid as necessary.

Fig. 3 shows surface and cross-sectional photographs of a flat-film-type ceramic separator having a surface coating film formed thereon. As can be seen from the left side surface photograph of FIG. 3, the surface of the coating film is well formed with pores. As can be seen from the photograph of the right side of FIG. 3, the coating film is well formed with a uniform thickness on the upper surface of the ceramic separator main body . Also, in the ceramic separator main body, alumina particles having a size of 5 mu m are hardly sintered to form a large pore channel having a size of 10 to 20 mu m.

4 is a graph showing pore analysis of the flat membrane-type ceramic separator according to an embodiment of the present invention. Porosity analysis was performed by porosimetry analysis. FIG. 4 (a) is a pore analysis graph of the ceramic membrane body, and FIG. 4 (b) is a pore analysis graph of the coating film formed on the ceramic membrane body.

Referring to FIG. 4A, the porosity of the ceramic separator according to the present invention is about 60%, which is much better than the porosity of 40-50% of the ceramic separator manufactured by the conventional extrusion method. The pore structure is divided into two groups. The pore group in the vicinity of 1 mu m is a pore formed between alumina powders having a particle size of 5 mu m. The pore group in the vicinity of the size of 10 to 20 mu m is a fibrous material Pore-forming agents. Referring to FIG. 4 (b), it has been confirmed that the pore size of the coating film can be precisely controlled between 0.1 μm and 0.5 μm through process control.

As described above, the method for manufacturing a flat membrane-type ceramic separator according to the present invention comprises forming a ceramic slurry having controlled viscosity and content by using a fiber pore forming aid, removing the pore forming agent through a degreasing and sintering process, The porosity of the ceramic separation membrane can be greatly improved and the permeability of the membrane can be reduced. Further, the manufacturing method according to the present invention improves workability and dimensional accuracy of the processed product because a large amount of pores are contained in the ceramic separator main body. In addition, the production method according to the present invention can effectively improve the problem that the product yield is lowered by conventional shrinkage cracks without complicated process control by uniformly controlling the shrinkage of the ceramic slurry in the drying and sintering process of the fiber pore- have. In addition, since the manufacturing method according to the present invention does not require an expensive facility such as an extrusion facility, the cost of the product can be reduced.

While the foregoing is directed to a specific embodiment of the present invention, it is to be understood that the above-described embodiment of the present invention has been disclosed for the purpose of illustration and is not to be construed as limiting the scope of the present invention, It should be understood that various changes and modifications may be made to the disclosed embodiments without departing from the spirit of the invention. It is therefore to be understood that all such modifications and alterations are intended to fall within the scope of the invention as disclosed in the following claims or their equivalents.

Claims (6)

A method of manufacturing a flat membrane type ceramic separation membrane including the steps of forming a semi-solid ceramic formed body and drying and sintering the semi-solidified shaped body, wherein the step of forming the semi-solid ceramic formed body comprises the steps of: Impregnating and laminating the ceramic membrane.
The method of claim 1, further comprising forming a surface coating layer after the sintering.
The ceramic slurry of claim 1,
55 to 60% by weight of alumina powder, silica powder or mixed powder thereof; 15 to 20% by weight binder; 0 to 0.1% by weight of defoamer; 0 to 1% by weight of a dispersant; And the remainder is water.
The method of claim 1, wherein the impregnating and laminating process is performed by a rolling or scraping method using a pore forming aid.
The method as claimed in claim 1, further comprising degreasing the semi-solid formed article after drying.
The method as claimed in claim 2, further comprising machining the surface coating film before forming the surface coating film.

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