KR100879127B1 - Method for controlling pore of porous body by freeze casting and porous body manufactured thereby - Google Patents

Abstract

A method for controlling air bubble of pore by using freeze casting is provided to control a pore size of pore, porosity and wall thickness using a simple method for controlling only a content of precursor or the freezing temperature. A method for controlling air bubble of pore by using freeze casting comprises steps of: comprising the raw material consisting of precursor, dispersing agent and freeze media; dispersing the precursor and the dispersing agent into the freeze media over a frozen temperature by using the raw material and manufacturing slurry; pouring slurry into a mold and freeze-casting the slurry at specific temperature below the frozen temperature; and removing the frozen media through freeze-drying and sublimation or melting.

Description

Method for controlling pore of porous body using freezing molding and porous body manufactured by the same {Method for controlling pore of porous body by freeze casting and Porous body manufactured}

The present invention relates to a method for controlling the pores of a porous body by freezing molding, and more particularly, the freezing temperature or the content of the precursor in the process of preparing the porous body by freezing and drying the precursor using a freezing medium. The present invention relates to a method for controlling pores of a porous body using cryoforming, and a porous body produced by the same, which can produce a porous body having a pore having a pore structure required by controlling the pore size, porosity, and wall thickness of the porous body by controlling.

Ceramic porous bodies are the core materials of high value-added industries that will lead the 21st century, including environment (ceramic diesel filter), energy (electrode for fuel cell), and bio (bone substitute). The physical properties of the ceramic porous body are greatly influenced not only by the properties of the material constituting the support body, but also by the pore structure such as porosity, pore interconnection, pore alignment, pore size, and the like. Therefore, pore structure control technology is a very important research field in the manufacture of ceramic porous bodies. The manufacturing technology currently being used in the development of bio artificial bones at home and abroad is as follows.

First, sponge replication is the most common method, which is a process of coating a ceramic slurry on a polyurethane sponge surface, burning a polymer sponge through heat treatment, and compacting the ceramic to prepare a porous body. This manufacturing technique is very useful for obtaining very high porosity (> 80%) and large pores connected in three dimensions, but it is easy to crack during heat treatment, and relatively weak in strength compared to other methods, and artificial pore structure control is impossible. .

Next, co-extrusion is a technique for manufacturing a ceramic green fiber using a co-extrusion method and laminating them to produce a porous body through heat treatment. Porosity, pore size and pore array can be easily controlled. However, there are disadvantages in that defects such as cracks and the like often occur during excessive heat treatment time and heat treatment.

In addition, solid freeform fabrication is the most advanced technology, and is a technique for manufacturing a porous ceramic body using computer CAD, which has a complex pore structure, but requires expensive equipment, limited production, and excessive heat treatment. There is a disadvantage in that expensive costs such as time.

On the other hand, freeze casting (freeze casting) is a technique for producing a ceramic porous body by removing the ice and heat treatment after freezing the ceramic slurry, a typical ceramic wet process is an environmentally friendly and very economical method.

Therefore, the technical problem of the present invention to solve the above problems is to freeze molding and drying the precursor using a freezing medium in the process of manufacturing the porous body by a simple method of controlling only the freezing temperature or the content of the precursor material It is to provide a pore control method of the porous body using the freezing molding to control the pore size, porosity and wall thickness.

 In addition, another technical problem of the present invention is to provide a porous body prepared by the method of controlling the pore of a porous body using the freeze-molding having a pore size, porosity and wall thickness controlled to be suitable for use as a porous filter, a cell support and a bone substitute. It is.

The present invention to solve the above technical problem,

(a) constructing a raw material comprising a precursor, a dispersant, and a freezing medium forming a porous body;

(b) preparing a slurry by dispersing a precursor and a dispersant in a freezing medium at a temperature above a freezing point using the raw material;

(c) subjecting the slurry to a mold and performing freeze molding at a specific temperature below freezing point; And

(d) removing the frozen medium through lyophilization and sublimation or dissolution in the freeze-molded material; It provides a pore control method of the porous body using a freezing molding comprising a.

The precursor may be a ceramic powder or a polymer material.

The freezing medium may be any one of water, camphor, tetrahydrofuran, xylene, hexane, cyclohexane.

The content of the precursor in relation to the freezing medium in step (a) is preferably used in the range of 5 to 70% by volume, and the dispersant compared to the precursor is preferably used in the range of 0 to 10% by weight. .

When the precursor is a ceramic powder, a heat treatment step may be accompanied as a subsequent step for imparting strength, and the heat treatment step is preferably cooled to room temperature after maintaining for 1 to 5 hours in the range of 1000 to 2000 ° C.

 In addition, the present invention provides a porous body produced by the method for controlling the pore of the porous body using the freezing molding in order to solve the above other technical problem.

According to the pore control method of the porous body of the present invention as described above,

In the preparation of a porous body by freezing and drying the precursor using a freezing medium, the pore size, porosity, and wall thickness of the porous body can be controlled by a simple method of controlling only the freezing temperature or the content of the precursor.

In addition, the porous body prepared by the pore control method can be controlled to form any desired pore size, porosity and wall thickness is suitable for use as a porous filter, cell support and bone substitute.

The present invention provides a pore size in the range of less than 1 to 100㎛, porosity in the range of 30 to 95% and wall thickness in the range of 0.1 to 50㎛ according to the control of the freezing temperature and precursor content in the preparation of the porous body by freezing medium removal after freezing The present invention provides a method for simultaneous control and a porous body having a pore size in the range of less than 1 to 100 μm, a porosity in the range of 30 to 95% and a wall thickness in the range of 0.1 to 50 μm.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and reproduce the present invention.

1 is a flow chart illustrating a method for controlling porosity of a porous body using freezing molding according to the present invention, after preparing a slurry of a precursor and a freezing medium at a freezing point, poured into a mold, and freezing after freezing at a freezing point The process for producing a porous body by removing the medium is schematically shown.

Referring to the drawings in more detail, the method for controlling the pore of a porous body using freezing molding according to the present invention first goes through the raw material composition step (S1).

The raw material is composed of a ceramic powder or polymer that will form a porous body, a precursor, a dispersant, and a freezing medium. The precursor may be a ceramic powder or a polymer material depending on the purpose of manufacturing a porous body such as a porous filter, a cell support, or a bone substitute. Can be. Ceramic powders include both oxides and nonoxides.

The freezing medium may be any solvent capable of dispersing the precursor in the case of ceramic powder, but is limited to a freezing medium in which the precursor is dissolved in the case of a polymer material. For example, when the precursor is polycarbosilane, camphor, tetrahydrofuran, xylene, hexane, etc., which can be dissolved are used.

In addition, the dispersant uses a commonly used ceramic dispersant.

Next, the present invention undergoes a slurry manufacturing step (S2) using a precursor and a freezing medium, which is a step of preparing a slurry in a good fluidity state by dispersing a precursor in a freezing medium at a temperature at which the freezing medium is higher than a freezing point. to be.

Here, as a method for controlling physical properties such as porosity, wall thickness, and strength of the porous body, the content of the precursor is compared to the freezing medium. The content of the precursor relative to the freezing medium is 5 to 70% by volume, and the dispersant may be used in the range of 0 to 10% by weight relative to the precursor to help the precursor is dispersed in the freezing medium.

That is, in order to control the porosity of the porous body to suit the demand, a method of controlling the content of the precursor is used. For proper strength, the content of the precursor to the freezing medium should be at least 5% by volume, and the pore connectivity Considering it should be up to 70%. That is, the volume ratio of the precursor to the freezing medium is in the range of 5 to 70%. Accordingly, the porosity of the porous body after removing the freezing medium can be adjusted in the range of 95% to 30%.

Next, the pore control method of the present invention is subjected to the freezing molding step (S3).

After the slurry is poured into the mold, freezing is performed at a specific temperature below the freezing point of the freezing medium, and in this step, the size of the pores is controlled by controlling the freezing temperature, which varies the freezing temperature in the freezing molding. By varying the distance between the condensation phase of the freezing medium to control the size of the pores.

That is, in general, the lower the freezing temperature, the faster the nucleation rate, and thus the narrower the gap between condensation phases, which are usually dendritic phases. Therefore, when the freezing temperature is removed by lyophilization and sublimation or dissolution, The pores of the size are to be formed, the size of the pores of the porous body is changed according to the difference in freezing temperature.

In the embodiment of the present invention, the temperature was controlled by using liquid nitrogen (-196 ℃) and dry ice-alcohol (-80 to 0 ℃) and water (0 to 100 ℃).

FIG. 2 is a view schematically illustrating a process in which precursors are separated while the freezing medium is frozen according to the present invention, and shows the principle of freezing molding by the freezing medium that grows dendriticly.

Next, the present invention undergoes a freeze medium removal step (S4), which is a step of forming a porous body by removing the frozen medium through lyophilization, sublimation and dissolution from the freeze-molded material.

That is, the freeze-molded raw material is vacuumed in a frozen state and rapidly dried to form a porous body having a pore size and porosity required by sublimation of the frozen medium or dissolving the frozen medium in the frozen state.

And, if the precursor is a ceramic powder, a heat treatment step (S5) is accompanied, which is a subsequent step for imparting strength to the porous body formed of ceramic.

The heat treatment step (S5) is completed by maintaining the furnace for 1 to 5 hours in the range of 1000 to 2000 ℃ and then cooled to room temperature.

On the other hand, in order to control the wall thickness of the porous body by the pore control method of the porous body using the freezing molding of the present invention together with the control of the freezing temperature in the slurry production step (S2) and the control of the precursor content in the freezing molding step (S3) It can be made by using, by the method the wall thickness can also be controlled in the range of 0.1 to 50㎛.

Examples according to the present invention are described below, but the present invention is not limited thereto.

Example 1

In this embodiment, a polycarbosilane, which is a kind of polymer, as a precursor is dissolved in camphor (C ₁₀ H ₁₆ ), which is a freezing medium, without a dispersant.

First, the polycarbosilane was dissolved in the campanine at a temperature of 60 ° C to prepare a polycarbosilane-campin solution, poured into a mold, and then frozen at 20, 0, -20, -40, and -196 ° C for 30 minutes, and then After removal, the process of preparing a porous body was performed by removing the frozen camphor resin phase through lyophilization (-50 ° C.), and the results are shown in FIGS. 3 and 4.

Figure 3 is a photograph showing the wall thickness pattern according to the freezing temperature in the cross section of the porous body prepared by Example 1 of the present invention, after removing the pin (formula: C ₁₀ H ₁₆ , a kind of freezing medium) of the precursor The cross section of polycarbosilane porous body shows the pore size and wall thickness according to freezing temperature. As can be seen in the figure, it can be seen that the higher the freezing temperature, the larger the pores and the thicker the wall.

Figure 4 is a graph showing the change in pore size according to the freezing temperature of Figure 3, Figure 4a is a graph showing the relationship between the temperature and the pore size, Figure 4b is a log showing the relationship between the pore size and the subcooling degree It is a graph. Referring to Figure 4b, it can be seen that the pore size of the log scale is inversely proportional to the subcooling degree of the log scale. Based on this result, it can be seen that any pore size within the range of 1 to 100 μm can be obtained by controlling the freezing temperature.

Example 2

In this embodiment, a precursor of a ceramic (hydrydyayapatite) was used as a precursor, and the content thereof was varied and dispersed in a freezing medium camppin with a dispersant to prepare a porous body.

10 to 20 vol% of apatite hydroxide relative to campanine at 60 ° C was dispersed in campine with 6 wt% of a dispersant compared to apatite hydroxide to prepare a slurry, poured into a mold, and frozen in a water bath at 20 ° C for 30 minutes. After removing the template, the frozen camphor dendritic was removed by lyophilization (-50 ° C.).

In addition, since the precursor is a ceramic powder, a heat treatment step is performed as a subsequent step for imparting strength. In the heat treatment step, the temperature is raised to 1250 ° C. at a temperature rising rate of 5 ° C. per minute for 3 hours, and then the furnace is cooled to room temperature. A porous body was prepared, and the results are as shown in FIGS. 5 and 6.

5a to 5c is a photograph showing the change of the porous body according to the content of the precursor in the cross-section of the porous body prepared by Example 2 of the present invention, a precursor of a precursor and a freeze medium of the camphor system It shows the change of pore according to material content. In Example 2, since the precursor was ceramic, the cross-section of the porous body after the freeze treatment at 1250 ° C. for 3 hours was shown. Referring to the drawings, it can be seen that the pore size decreases as the content of the precursor increases.

FIG. 6 is a graph showing porosity according to the amount of apatite hydroxide, which is the precursor of FIG. 5, and it can be seen that the porosity tends to decrease as the precursor content increases. Based on this result, it can be seen that by controlling the content of the precursor, a porous body having an arbitrary porosity in the range of 95 to 30% can be produced. At porosity of less than 30%, each void connectivity may be significantly reduced, and thus are excluded from the scope of the present invention.

FIG. 7 is a graph showing compressive strength according to porosity in the apatite hydroxide porous bodies shown in FIGS. 5 and 6, and shows that the strength of the porous body can be controlled by adjusting the porosity. In the embodiment of the present invention represented only the compressive strength, but suggests the possibility of changing the air permeability, filter performance, bone regeneration ability according to the change in porosity and pore size.

As described above, the present invention provides a method for producing a porous body having any value of pore size in the range of less than 1 to 100 μm, porosity in the range of 30 to 95% and wall thickness in the range of 0.1 to 50 μm. For example, if you want to prepare a porous apatite hydroxide having a pore size of 10 ㎛ and porosity of 75%, by using the process of the pin in the Example 10 vol% slurry by freezing at a temperature of -20 ℃ You can predict it.

By preparing a porous body that can meet the required physical properties such as strength and breathability by the pore control method, it can be applied to the demands of various fields such as porous filter, cell support and bone regeneration support.

1 is a flow chart schematically showing a method for controlling the pore of a porous body using freezing molding according to the present invention.

2 is a view schematically illustrating a process in which the precursor is separated while the freezing medium is frozen according to the present invention.

3 is a photograph showing the wall thickness according to the freezing temperature in the cross section of the porous body prepared by Example 1 of the present invention.

Figure 4 is a graph showing the change in pore size according to the freezing temperature of Figure 3, Figure 4a is a graph showing the relationship between the temperature and the pore size, Figure 4b is a log showing the relationship between the pore size and the subcooling degree It is a graph.

5a to 5c is a photograph showing the change of the porous body according to the content of the precursor in the cross section of the porous body prepared by Example 2 of the present invention.

6 is a graph showing the porosity according to the precursor content of FIG.

7 is a graph showing compressive strength according to porosity in the apatite hydroxide porous body shown in FIGS. 5 and 6.

Claims (8)

(A) forming a raw material consisting of a precursor and a dispersant and a freezing medium forming a porous body (S1); (B) preparing a slurry by dispersing a precursor and a dispersant in a freezing medium at a temperature above the freezing point using the raw material (S2); (c) performing freeze molding at a specific temperature below the freezing point after pouring the slurry into the mold (S3); And (d) removing the frozen medium through lyophilization and sublimation or dissolution in the freeze-molded material (S4); Pore control method of the porous body using a freezing molding comprising a. The method of claim 1, wherein the precursor is a ceramic powder or a polymer material. The porous body of claim 1, wherein the freezing medium is any one of water, camphor, xylene, hexane, cyclohexane, and tetrahydrofuran. Control method. The method of claim 1, wherein when the precursor is a ceramic powder, a porosity control method of a porous body is characterized by a heat treatment step as a subsequent step. 5. The method of claim 4, wherein the heat treatment is performed by maintaining the apparatus at a temperature in a range of 1000 to 2000 ° C. for 1 to 5 hours and then cooling the furnace to room temperature. The method of claim 1, wherein the content of the precursor relative to the freezing medium in step (a) is in the range of 5 to 70% by volume. The method of claim 1, wherein the dispersing agent in comparison with the precursor in step (a) is in the range of 10% or less by weight.  A porous body produced by the method for controlling the pore of a porous body using the cryoforming according to any one of claims 1 to 7.

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