KR101431493B1 - Method for controlling pore size of micromembrane and preprocessing filter using micromembrane manufactured thereby - Google Patents

Abstract

The present invention relates to a method for controlling an average pore size of a microfiltration membrane and a prefilter for pretreatment comprising a microfiltration membrane produced from the method.
The average pore size control method of the microfiltration membrane of the present invention is performed by casting a polymer solution made of a polysulfone polymer in an optimum condition in which the pore size of the inside and the surface of the membrane is controlled according to the air injection speed and the air exposure time , It is possible to provide a symmetric polysulfone-based microfiltration membrane in which pores on the surface and inside of the membrane satisfy an average pore size of 0.01 to 10 mu m. Furthermore, since the symmetric polysulfone-based microfiltration membrane manufactured by the average pore control method of the microfiltration membrane of the present invention is easily controlled and provided with an average pore size, it is excellent in the removal efficiency characteristic for each particle size to be removed, , Pre-filter for pretreatment in pharmaceutical and beverage industry process field.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for controlling an average pore diameter of a microfiltration membrane, and a pretreatment prefilter comprising a microfiltration membrane produced from the microfiltration membrane.

The present invention relates to a method for controlling an average pore diameter of a microfiltration membrane and a pretreatment prefilter comprising the microfiltration membrane produced from the method. More particularly, the present invention relates to a prefilter for pre- And a prefilter for pretreatment comprising a symmetric polysulfone-based microfiltration membrane produced therefrom.

Membranes are widely used in various fields and can be used for various applications such as microfiltration membranes, ultrafiltration membranes, gas separation membranes, pervaporation membranes, and reverse osmosis membranes. Various methods are known as a method for producing such a separation membrane. In general, a nonsolvent induced phase inversion (NIPI) process is used as a method for producing a separation membrane. The non-solvent-derived phase transfer method is a method in which a polymer is dissolved in an appropriate solvent to prepare a solution, which is then cast to a thin film and immersed in a non-solvent to obtain a solid phase membrane, and an asymmetric cellulosic acetate- From the fabrication of membranes to the present day, membranes used in a wide range from microfiltration to gas permeation have been fabricated by the non-solvent based induction phase transfer method.

The polymer membranes prepared by this method, in particular, polyether sulfone resin membranes have been widely used because they have high thermal stability, oxidation stability, and stability against temperature and are advantageous for water treatment.

Generally, it can be divided into symmetry in the cross-sectional structure of the membrane and an asymmetric polymer membrane. The asymmetric polymer separator is composed of a very dense selective layer at a predetermined position in a membrane section and a porous layer positioned in addition to the layer so that it has high selectivity to remove particles of a predetermined size or more by the selective layer, Due to the layer, it is designed to maintain mechanical strength and to achieve good selective permeate flow.

However, symmetric polymer membranes are less active than relatively asymmetric membranes because they point to the problem that contamination of the membrane surface is easily induced by particles in the raw water, resulting in reduced permeation flow rate and reduced service life.

As an example thereof, Patent Document 1 discloses a polysulfone-based contaminant film having hydrophilicity to hydrophilic polysulfone-based polymer separation membranes and having a reduced rate of flow reduction due to a contaminant source. However, such a polysulfone- On the other hand, the optimum condition for controlling the average pore size of the membrane is not clear, and it takes a lot of time and cost to adjust the desired symmetric structure and various pore sizes.

The present inventors have made efforts to solve the problems of the prior art. As a result, the present inventors have found that when casting a polymer solution in the production of a polymer membrane, the average pore size of the pores formed in the inside and the surface of the membrane is controlled, The present inventors have accomplished the present invention by securing a polymer membrane having a symmetric structure.

Korean Patent Publication No. 2011-0131681 (December 24, 2011)

It is an object of the present invention to provide an average pore control method of a microfiltration membrane capable of controlling the pore size formed on the inside and the surface of a membrane.

Another object of the present invention is to provide a pretreatment prefilter comprising a microfiltration membrane in which pores having a desired mean pore size are symmetrically formed on the inside and the surface of the membrane.

In the present invention, the temperature of the support is adjusted to 20 to 30 캜, the polymer solution of the polysulfone-based polymer is cast on the support to form the inner pores of the membrane, and after the casting, And air kept at a humidity of 30 to 80% at an injection speed of 1.0 to 20 m / min for 5 seconds to 10 minutes to form surface pores of the film, A method for controlling an average pore diameter of a filtration membrane is provided.

In order to form the inner pores of the membrane of the present invention, the polymer solution is maintained at 35 to 60 DEG C so that the inner pores of the membrane are controlled to satisfy the average pore size of 0.01 to 10 mu m.

According to the control method of the present invention, the surface pores of the film are formed with an average pore size of 0.01 to 10 mu m.

The present invention provides a pretreatment prefilter consisting of a symmetric polysulfone based microfiltration membrane formed on the inside of the membrane and on the entire surface of the membrane with an average pore diameter ranging from 0.01 to 10 mu m.

In the pre-filter for pretreatment of the present invention, the symmetric polysulfone-based microfiltration membrane is preferably formed to a thickness of 100 to 190 탆, and satisfies a water permeability of 15 to 110 ml / min ㎠ m2 bar.

The average pore size control method of the microfiltration membrane of the present invention can provide a microfiltration membrane of a symmetric polysulfone system by determining optimum conditions for controlling the pore size of the inside of the membrane and the membrane surface.

Therefore, the symmetric polysulfone-based microfiltration membrane manufactured by the average pore control method of the present invention can be easily controlled and provided with an average pore size, It can be usefully used as a pre-filter for pretreatment in the pharmaceutical and beverage industry process field.

1 is a scanning electron microscope (SEM) image of a surface of a symmetric polysulfone microfiltration membrane (mean pore diameter 0.1 mu m) 5,000 times enlarged according to an air injection speed of 1.0 m / min in the method of the present invention,
2 is a scanning electron microscope (SEM) image of a surface of a symmetric polysulfone microfiltration membrane (average pore diameter 0.45 탆) enlarged 5,000 times according to an air injection speed of 1.5 m / min in the method of the present invention,
3 is a scanning electron microscope (SEM) image of a surface of a symmetric polysulfone microfiltration membrane (mean pore diameter 0.8 μm) enlarged 5,000 times according to the air injection speed 2.0 m / min of the method of the present invention,
4 is a scanning electron microscope (SEM) image of a surface of a symmetric polysulfone microfiltration membrane (average pore diameter 0.005 탆) enlarged 5,000 times according to an air injection rate of 0.1 m / min in the method of the present invention.

To achieve the above object, the present invention provides a method for controlling an average pore size of a microfiltration membrane. More specifically,

1) Prepare the support at a temperature of 20 to 30 캜,

2) casting a polymer solution composed of a polysulfone-based polymer on the support to contact the support to form internal pores of the membrane,

3) After the casting, air kept at a temperature of 20 to 60 캜 and a humidity of 30 to 80% is exposed to air at an injection speed of 1.0 to 20 m / min for 5 seconds to 10 minutes to form surface pores of the film,

4) immersing in a coagulation bath to solidify and peel off from the support.

Accordingly, the average pore size control method of the microfiltration film of the present invention will be described step by step. First, the support used in step 1) is a metal material, preferably stainless steel, aluminum, copper alloy or the like. Although the embodiment of the present invention is described using stainless steel, the present invention is not limited thereto.

The surface temperature of the support is maintained at 20 to 30 DEG C, and if the temperature is less than 20 DEG C, the pore size of the inside and the surface of the film becomes large and the asymmetry calculated therefrom becomes high. , The temperature difference between the polymer solutions becomes small and it is inefficient to control the structure of the pores by the heat induction phase transition method.

Then, step 2) is performed by casting a polymer solution made of a polysulfone-based polymer on the support to form an inner pore of the membrane in contact with the support. The inner pore of the membrane in contact with the support is 0.01 10 mu m.

Therefore, in order to form pores having a desired size, the temperature of the polymer solution to be cast on the support is maintained at a temperature higher than the temperature of the support, preferably, the polymer solution is maintained at 35 to 60 캜. The pore size herein means the average diameter of the pores.

At this time, when the polymer solution is cast on the support in step 2), the thickness of the film is preferably less than 200 mu m, more preferably 100 to 190 mu m, and most preferably 100 to 130 mu m.

The polymer solution used in step 2) is composed of 8 to 20% by weight of a polysulfone-based polymer, 10 to 30% by weight of a hydrophilic pore-controlling agent, and a residual solvent.

The polysulfone-based polymer may be selected from the group consisting of polysulfone, polyether sulfone, and polyallyl ether sulfone polymer, or a mixture thereof. In the examples of the present invention, a polysulfone-based polymer is used, But is not limited thereto.

The hydrophilic porosity controlling agent is a composition for forming internal pores, and any hydrophilic porosity controlling agent may be used as long as it can be mixed well with a solvent. More preferably, a hydrophilic porosity controlling agent selected from polyvinyl pyrrolidone and polyethylene glycol is used.

If the amount of the hydrophilic pore-controlling agent is less than 10% by weight, the effect of the hydrophilic pore-controlling agent is insufficient. When the amount of the hydrophilic pore-controlling agent is more than 30% by weight, And the mechanical performance of the membrane is disadvantageous.

When the hydrophilic pore-controlling agent is contained in a mixed form, glycols including ethylene glycol and glycerol; Alcohols including ethanol and methanol; And ketones including acetone; and a hydrophilic additive selected from the group consisting of:

At this time, it is preferable that the above-described hydrophilic additive is used in a proportion of less than 50%, and if it is more than 50%, molding of the film itself is difficult.

The solvent used for the polymer solution of step 2) is at least one selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, dimethylsulfoxide and dimethylacetamide, The remaining amount excluding the content of the above components is used at 100% by weight in total.

Thereafter, in the production method of the present invention, step 3) is a step of forming pores of the film surface by air injection after casting in step 2), and forming on the surface of the film according to the optimum air injection speed and air exposure time It is possible to control the average pore size of the pores to be formed.

Preferably, the conditions for forming the pores on the surface of the membrane are such that the air jetting rate is 1 to 20 m / min, more preferably 1 to 10 m / min under the condition that the air injection temperature is maintained at 20 to 60 DEG C and the humidity is 30 to 80% Air injection. At this time, the air exposure time is performed for 5 seconds to 10 minutes.

By the step 3), the pores formed on the surface of the film are controlled to an average pore size of 0.01 to 10 mu m. At this time, if the air injection speed is less than 1 m / min, there is a problem of process control. If the air blowing speed is higher than 20 m / min, scratches occur on the surface of the film, .

FIGS. 1 to 3 are schematic diagrams showing a case where air is injected at a rate of 1.0 m / min, 1.5 m / min and 2.0 m / min, respectively, when casting a polymer solution made of a polysulfone- The average pore size of the sample. From the above results, it can be seen that the surface pore size of the membrane can be controlled according to the air injection speed during casting.

Also, Fig. 4 shows that, in the casting step, air purging was not observed on the surface of the film when the air injection speed was set to 0.1 m / min, i.e., the air was not sprayed.

When air is injected, the air exposure time is preferably 5 seconds to 10 minutes, and if it is less than 5 seconds, formation of pores on the surface is insufficient. Therefore, it is preferable to sufficiently control the residence time for solidifying Do. At this time, if the air exposure time exceeds 10 minutes, the appearance of the membrane is not preferable.

Thereafter, step 4) of the present invention is immersed in a coagulation bath to peel the membrane from the support to obtain a polysulfone-based microfiltration membrane.

That is, the support on which the polymer solution exposed to air is applied is passed through a coagulation bath not dissolving the polymer solution to solidify the membrane, and the solidified membrane is peeled from the support. At this time, the coagulation bath may be selected from isopropyl alcohol or water, but is not limited thereto.

Further, in the manufacturing method of the present invention, a post-step of dipping the peeled membrane into a water bath to extract residual solvent components contained in the membrane matrix to form pores may be further performed.

From the above, it can be seen that the present invention is characterized in that the pores inside the film satisfy the average pore diameter of 0.01 to 10 m and the pores which satisfy the average pore size of 0.01 to 10 m on the surface of the film which is the opposite surface to the inside, A polysulfone-based microfiltration membrane having a symmetrical structure formed in an average pore size range of 10 mu m.

Therefore, the symmetric polysulfone-based microfiltration membrane manufactured by the average pore control method of the present invention is useful as a microfiltration membrane due to its high removal efficiency for each particle size by controlling the average pore diameter. Particularly, It is useful as a pre-filter for pretreatment in the pharmaceutical, pharmaceutical and beverage industry process industries that require stability at the same time.

Accordingly, the present invention provides a pre-filter for pretreatment comprising a symmetric polysulfone-based microfiltration membrane in which the inside and the surface of the membrane are formed in the entire membrane with an average pore size range of 0.01 to 10 mu m.

In the field of pharmaceuticals, biotechnology, and food and beverage, the pre-filter for the purpose of pre-treatment, that is, the pre-filter for keeping the process influent water constantly while removing impurities, is required to remove selective particles having a size of 10 μm or less. In the symmetric polysulfone- Is optimized for its use because the inside and the surface of the membrane are formed in the entire membrane with an average pore size range of 0.01 to 10 mu m.

Further, the thickness of the symmetric polysulfone-based microfiltration membrane of the present invention is formed to be less than 200 占 퐉, more preferably 100 to 190 占 퐉 in thickness, and securing a water permeability within 15 to 110 ml / min 占 ㎠ m2 bar, It is advantageous to manufacture membranes having appropriate thicknesses with various mean pores depending on the application of the membrane, and are suitable for pharmaceutical, pharmaceutical and beverage industry processing fields depending on the characteristics of the membranes.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The present invention is intended to more specifically illustrate the present invention, and the scope of the present invention is not limited to these embodiments.

≪ Example 1 >

17% by weight of a polysulfone-based polymer was dissolved in 53% by weight of dimethylacetamide, 15% by weight of polyethylene glycol (molecular weight 200) and 15% by weight of polyvinylpyrrolidone were added, and the mixture was stirred in a water bath at 50 ° C for 12 hours Followed by stirring to prepare a polymer solution.

The polymer solution was uniformly coated on a stainless steel support at 20 캜 at a rate of 0.2 m / min so as to have a thickness of 120 탆.

Thereafter, the pore size of the surface was controlled by treating the coated polymer solution by exposing the air at a rate of 1.0 m / min at a rate of 1.0 m / min for 30 seconds by using a gradient apparatus at a temperature of 30 ° C and a humidity of 60%. The composition ratio of isopropyl alcohol / And the mixture was allowed to solidify by passing through a coagulation tank. Thereafter, the membrane was peeled off from the support, the residual solvent component contained in the membrane was extracted in a water bath, and the membrane was dried with air at 80 ° C to prepare a membrane.

≪ Example 2 >

A membrane was produced in the same manner as in Example 1 except that the air injection speed was changed to 1.5 m / min in the membrane production process of Example 1.

≪ Example 3 >

A film was produced in the same manner as in Example 1 except that the air injection speed was changed to 2.0 m / min and the air was exposed for 60 seconds in the film manufacturing process of Example 1. [

<Example 4>

A film was produced in the same manner as in Example 1 except that the air injection speed was changed to 5.0 m / min and the air was exposed for 15 seconds in the film manufacturing process of Example 1. [

&Lt; Example 5 >

A film was produced in the same manner as in Example 1 except that the air injection speed was changed to 8.0 m / min and the air was exposed for 5 seconds in the film manufacturing process of the first embodiment.

&Lt; Comparative Example 1 &

A membrane was produced in the same manner as in Example 1 except that the air injection speed was set to 0.1 m / min in the membrane production process of Example 1.

&Lt; Comparative Example 2 &

A membrane was produced in the same manner as in Example 1 except that the air injection speed was 21.0 m / min in the membrane production process of Example 1.

<Experimental Example 1> Measurement of film properties

The membranes prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured at a constant pressure (1 bar) through a sample holder having a diameter of 90 mm (manufactured by Woongjin Chemical Co., Ltd.) Were measured.

The results are shown in Table 1 below.

As shown in Table 1, the average pore size of the prepared membrane was increased as the air injection rate including the constant air exposure was increased. In particular, the formation of the average pore size of the surface / interior of the membrane is determined by the mass transfer rate difference of the surface.

Example 4 and Example 5 show that the commercially available membrane surface appearance can be maintained by reducing the air exposure time while increasing the air injection speed.

The results of Comparative Example 1 show that formation of pores is too small to form a microfiltration membrane when air is not sprayed. In the case of Comparative Example 2, the air injection speed is increased to increase the average pore size The membrane surface is excessively large and shrinkage of the membrane surface is serious and can not be utilized as a microfiltration membrane.

As described above,

The present invention relates to a microfiltration membrane capable of controlling the pores on the surface and inside of the membrane to an average pore size of 0.01 to 10 μm according to the air injection speed and the air exposure time when casting the polymer solution made of the polysulfone- An average pore control method was provided.

The symmetric polysulfone-based microfiltration membrane produced by the average pore control method of the microfiltration membrane of the present invention realizes excellent removal efficiency characteristics for each particle size to be removed by easily controlling the average pore size.

Thus, the symmetric polysulfone microfiltration membrane formed inside the membrane of the present invention and having an average pore size range of 0.01 to 10 mu m as the surface of the membrane of the present invention is a prefilter for pretreatment in pharmaceutical, pharmaceutical and beverage industry processes requiring stability useful.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

The surface temperature of the support is maintained at 20 to 30 DEG C and the support is cast with a polymer solution made of a polysulfone polymer and maintained at a temperature of 35 to 60 DEG C and the temperature difference between the support and the polymer solution makes contact with the support Is controlled to have an average pore size of 0.01 to 3.05 mu m,
After the casting, the air kept at a temperature of 20 to 60 DEG C and a humidity of 30 to 80% was exposed to air for 5 seconds to 10 minutes at an injection speed of 1 to 20 m / min to form pores having an average pore size of 0.01 to 3.05 mu m Respectively,
Wherein the support is immersed in a coagulation bath to be solidified and peeled from the support, wherein the average pore diameter of the microfiltration membrane of the symmetrical pore structure is controlled. delete delete delete A pre-filter for pretreatment comprising a polysulfone-based microfiltration membrane formed in a symmetric pore structure across the membrane in the range of 0.01 to 3.05 mu m in average pore size of the inner pores of the membrane and the surface pores of the membrane. 6. The pre-filter for pretreatment according to claim 5, wherein the polysulfone-based microfiltration membrane of the symmetric pore structure has a thickness of 100 to 190 mu m. 6. The pre-filter for pretreatment according to claim 5, wherein the polysulfone-based microfiltration membrane of the symmetric pore structure satisfies a water permeation amount of 15 to 110 ml / min.

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