KR101025754B1 - Macrovoid free hollow fiber membrane and manufacturing method threrof - Google Patents

Abstract

The present invention relates to a high-performance hollow fiber membrane and a method for producing the same, which have no macropores in the polymer membrane structure, thereby improving separation efficiency and mechanical strength.

The present invention provides a compact micropores without macropores in the polymer membrane structure from the manufacturing method that can control the formation of the macropores by controlling the spinning conditions, without changing the spinning solution composition and ratio or additional process introduced in the conventional method. By providing a hollow fiber membrane made of only, to solve the problem of membrane fouling rejection, mechanical strength and membrane life degradation problems due to large pores, and particularly excellent oxygen permeability, the hollow fiber membrane of the present invention is a water purification process It can provide excellent performance as a hollow fiber membrane for liquid / gas separation as well as for water treatment used in water and wastewater processes.

Polymer membrane, macropore, hollow fiber, separator

Description

Hollow fiber membrane without macropore and its manufacturing method {MACROVOID FREE HOLLOW FIBER MEMBRANE AND MANUFACTURING METHOD THREROF}

The present invention relates to a hollow fiber membrane without a macropore in the polymer membrane structure and a method for manufacturing the same, and more specifically, to control the formation of macropores by controlling the spinning conditions, without changing the composition and ratio of the polymer solution or additional process introduction. The present invention relates to a high-performance hollow fiber separator and a method for producing the same, which have improved separation efficiency and mechanical strength.

The polymer membrane is the most widely used membrane type in the membrane separation process, which is an efficient separation process.A nonsolvent induced phase separation method in which a polymer membrane is dissolved in a solvent and immersed in a nonsolvent is used to form the membrane. thermally induced phase separation (TIPS) method, which forms a separator while melting and cooling a polymer with additives at a temperature above the glass transition temperature (Tg). Is widely used.

Among them, the polymer separation membrane manufactured by the NIPS method is easy to manufacture the membrane and the manufacturing cost is low, so that it can be applied to a variety of membrane production, it is the most used. However, in the above production method, in the process of solidifying the polymer solution in the non-solvent, due to non-uniform intrusion of the non-solvent and different coagulation force difference, the diameter of the polymer membrane in the solidification process in the solidification process, the cross-section in the cross section of 4㎛ or more Macro-voids are generated to cause leakage of the polymer membrane. Therefore, the macropores in the polymer membrane structure are known to contribute to lowering the separation efficiency, lower mechanical strength and lower chemical resistance of the membrane, it is recognized as a problem that must be removed in the manufacturing process of the polymer membrane using the NIPS process.

In order to solve this problem, in the preparation of polymer membrane using NIPS process, the size of air gap and spinneret was adjusted to control the formation of macropores [ Industrial & Engineering Chemistry Research , 2006 , 45 , 7618-7626.], The problem is still not solved to the extent that partial removal, rather than complete macropore control technology, is possible.

In addition, an attempt was made to increase the concentration of the polymer in the polymer solution to suppress the formation of macropores. However, when the concentration of the polymer is increased, the formation of the macropores in the polymer membrane structure is somewhat suppressed. And deteriorate the membrane performance (US Pat. No. 4,871,494, Journal of Applied Polymer Science , 1990 , 40 , 1557).

As another method, it has been reported that the production of polymer membranes inhibits the formation of macropores by adding TiO ₂ nanoparticles to the polyimide material. The additional cost of re-extracting is required, which increases the manufacturing cost due to the complicated process [ Chemical Engineering Science , 2006 , 61 , 6228].

In addition, according to the Republic of Korea Patent No. 129816, using a triple nozzle including a two-stage polymer solution discharge port by modifying the spinning nozzle in the spinning process for the production of hollow fiber membrane for water treatment, by generating a macropore by adjusting the polymer solution composition and solidification rate The separator which suppressed this is disclosed. However, the use of the triple nozzle has a disadvantage that the manufacturing cost is high, since the manufacturing method is complicated and additional supplementary manufacturing equipment is required compared to the use of the single nozzle.

Therefore, in the present invention, while trying to provide a manufacturing method for efficiently suppressing the macropore generation while solving the problems of the prior art attempted to suppress the macropore generation in the manufacturing process of the polymer hollow fiber membrane using the NIPS method, The present invention has been completed by providing a high performance polymer membrane without macropores by developing a spinning process capable of suppressing the generation of macropores even in the production equipment and the polymer solution composition.

An object of the present invention is to provide a hollow fiber membrane without a macropore in the polymer membrane structure.

Another object of the present invention is to provide a method for producing a high-performance hollow fiber membrane that improves the separation efficiency and mechanical strength by controlling the generation of macropores without additional process introduction.

The present invention provides a hollow fiber separator in which the macropores in the cut surface of the hollow fiber separator are present at 0 to 20 holes / μm ² .

The hollow fiber has an outer diameter of 0.4 to 5.0 mm, an inner diameter of 0.1 to 4.8 mm, and has a pore volume of 20% or more. The hollow fiber membrane of the present invention has an oxygen permeability of 10 to 150,000 LMH (L / m ² h) under 1 atm. Because of its high oxygen permeability, it can be suitably utilized not only for water treatment but also for liquid / gas separation.

The present invention is a hollow fiber membrane for controlling the formation of macropores in the manufacturing process of the polymer membrane using the NIPS method, without additional process introduction, such as adjusting the polymer solution composition and ratio, performing expensive additional equipment and post-treatment process, etc. It provides a method of manufacturing.

In the manufacturing method of the hollow fiber membrane of the present invention, a polymer solution and an additive are dissolved in a solvent to prepare a spinning solution, and when the spinning solution is spun through a spinneret having a circular discharge port, a solvent and a non-solvent filled in the annular discharge port. After contact with the internal coagulant consisting of, the spinning solution and discharged to the non-solvent, the external coagulant, the temperature difference is maintained within 80 ℃, and during spinning, the winding while maintaining the winding speed at 10m / min or more to manufacture .

At this time, the winding speed during spinning is 10 to 100 m / min, the temperature difference between the spinning solution and the external coagulant should be maintained within 0 to 80 ℃.

Among the coagulants of the present invention, in the internal coagulant comprising a mixture of a solvent and a non-solvent, the composition ratio of the solvent is suitably 30% or more by weight and 100% or less, more preferably 50% or more and less than 100%. Preferred solvates are N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, dimethylformamide, glycerin, polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol and diethylene glycol Any solvent selected may be used, and pure water (DI water) and alcohols may be used as the non-solvent.

In the manufacturing method of the present invention, pure coagulant is used as the external coagulant for discharging the spinning solution.

In the spinning solution of the present invention, the polymer resin is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichlorofluoroethylene, polyphenylsulfone, polyethersulfone, polysulfone, poly Preference is given to single or mixed forms of one or more selected from the group consisting of acrylonitrile and cellulose acetate.

The polymer is dissolved in a solvent and mixed with an additive to prepare a spinning solution. Preferred solvents include N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, dimethylformamide, and the like, which are used alone or in combination of one or more. In addition, the additive is alone or selected from the group consisting of polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol, diethylene glycol, polyethylene oxide, methoxyethanol, butoxyethanol, tetrahydrofuran and pentanol Use one or more mixed forms.

The present invention provides a hollow fiber membrane consisting only of dense micropores without macropores in the polymer membrane structure, thereby eliminating problems such as degradation of membrane fouling material rejection, mechanical strength, and membrane lifespan.

In particular, the present invention exhibits excellent oxygen permeability without degrading gas or liquid permeability, thereby providing a high performance hollow fiber membrane which is more useful for liquid / gas separation.

In addition, the present invention provides a manufacturing method that can control the formation of macropores by controlling the spinning conditions, without changing the composition and ratio of the polymer solution used in the conventional manufacturing process of the polymer membrane using the NIPS method or additional process introduction By using the manufacturing method of the present invention, it can be used in the water purification process and wastewater process as well as gas separation membrane field.

Hereinafter, the present invention will be described in detail.

The present invention provides a hollow fiber separator consisting of dense micropores without macropores in the polymer membrane structure. That is, the macropores in the cut plane of the hollow fiber membrane of the present invention is present in the cutting surface of 0 ~ 20 / μm ² [ Fig. 1 ], the large pore size of 4㎛ or more found in the cross section of the conventional polymer membrane using the NIPS method is observed Not [ FIG. 2 ].

The hollow fiber of the present invention has an outer diameter of 0.4 to 5.0 mm, an inner diameter of 0.1 to 4.8 mm, and has a pore volume of 20% or more. The hollow fiber membrane of the present invention is made of only dense pores without macropores in the structure. It is possible to solve the problems such as the reduction of membrane contaminant exclusion capacity, mechanical strength and membrane life.

In particular, the present invention exhibits an excellent oxygen permeability of 10 to 150,000 LMH (L / m ² h) under 1 atmosphere of pressure, without degrading gas or liquid permeability, thereby separating liquid and gas. It provides a high performance hollow fiber membrane that can be suitably utilized for the purpose.

The present invention provides a method for producing a hollow fiber membrane to control the formation of macropores by controlling the spinning conditions, without changing the polymer solution composition and ratio or the additional process introduced in the manufacturing process of the polymer membrane using the conventional NIPS process. .

More specifically, the manufacturing method of the hollow fiber membrane of the present invention is to prepare a spinning solution by dissolving the polymer resin and additives in a solvent, when the spinning solution is spun through a spinneret having a circular discharge port, a part of the annular discharge port After contacting with an internal coagulant composed of a solvent and a non-solvent filled in the above, the spinning solution is discharged into a non-solvent, which is an external coagulant maintained at a temperature difference of 80 ° C or less, and during spinning, the winding speed is 10 m / min or more. It consists of winding and manufacturing, maintaining.

In the spinning solution, the internal coagulant may be a solvent / non-solvent exchange rate by the non-solvent induced phase separation method (NIPS) method by using a mixed solvent in which a non-solvent is added to a solvent that is commonly used, and thus, macropores. Production can be suppressed.

At this time, in the internal coagulant consisting of a mixture of a solvent and a non-solvent, the weight ratio of the solvent is suitably 30% or more and 100% or less, more preferably 50% or more and 100% or less. Preferred solvates are N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, dimethylformamide, glycerin, polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol and diethylene glycol It is preferable to use any one solvent selected from the above, and the non-solvent is to use pure water (DI water) and alcohols, it can be used by mixing with components that can be used as a non-solvent other than pure water.

In the manufacturing method of the hollow fiber membrane of the present invention, the external coagulant is maintained at an appropriate temperature to suppress the formation of macropores, thereby inhibiting the formation of macropores due to nonsolvent infiltration. The temperature of the external coagulant is determined according to the dissolution conditions of the spinning solution, and it is preferable that the temperature difference between the spinning solution and the external coagulant is maintained within 0 to 80 ° C., more preferably, the solvent is appropriately maintained at 0 to 50 ° C. It is preferable to maintain at the exchange rate. If the temperature difference between the spinning solution and the external coagulant is 80 ° C. or more, macropores are formed, which causes degradation of the membrane performance.

The external coagulant used in the present invention preferably uses pure water, but may be used by mixing with components which can be used as a non-solvent in addition to pure water.

In the manufacturing method of the hollow fiber membrane of the present invention, in order to prevent the formation of macropores, the winding speed is 10 m / min or more, more preferably 10 to 100 m / min, and most preferably the winding speed. 20 to 50 m / min. At this time, when spinning, if the winding speed is less than 10m / min, it is difficult to inhibit the formation of macropores in the spinning process, when it exceeds 100m / min, the spinning itself is difficult to make the hollow fiber membrane membrane.

That is, the manufacturing method of the present invention maintains the winding speed at 10m / min or more during spinning, and by selecting the appropriate internal coagulant, by delaying the inflow rate and coagulation speed of the non-solvent from the outside during the coagulation process of the spinning solution Hollow fiber membranes having a compact pore distribution without pores can be prepared.

In the manufacturing method of the hollow fiber membrane of the present invention, in the spinning solution, the polymer resin can be used as long as the polymer is soluble in a soluble solvent, and preferred examples thereof include polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene. , Polyvinylidene fluoride-trichlorofluoroethylene, polyphenylsulfone, polyethersulfone, polysulfone, polyacrylonitrile and cellulose acetate are used alone or in combination of one or more thereof. More preferably, polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile is used.

The spinning solution is prepared by mixing a polymer resin and an additive in a solvent, and preferred solvents include N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, and the like. Use

The additive in the spinning solution is used to control the pore structure and porosity of the formed polymer layer, and improve the hydrophilicity of the separator.

Preferred additives include polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol, diethylene glycol, polyethylene oxide, methoxyethanol, butoxyethanol, tetrahydrofuran and pentanol alone or It is to use one or more mixed forms.

The spinning solution of the present invention preferably contains 45 to 90% by weight of the solvent and 10 to 55% by weight of the mixed content of the polymer resin and the additive, and more preferably, 65 to 85% by weight of the solvent and the mixture of the polymer resin and the additive. It contains content of 15 to 35% by weight. In this case, when the mixing content of the polymer resin and the additive is less than 10% by weight, it is impossible to form the hollow fiber membrane due to the low viscosity, and when the content exceeds 55% by weight, the productivity of the membrane is significantly reduced due to the high viscosity of the solution.

In addition, the mixing ratio of the polymer resin and the additive is preferably 1: 0.1 to 0.7 by weight, if out of the ratio, it is difficult to form the film forming and the desired structure.

In the manufacturing method of the hollow fiber membrane of the present invention to maintain the temperature of the non-solvent, which is an external coagulant during spinning, to suppress the formation of large pores by infiltration of the non-solvent, to maintain the winding speed at 10m / min or more during spinning, By selecting an appropriate internal coagulant, it is possible to produce a hollow fiber membrane having a dense pore distribution without macropores by delaying the inflow rate and the coagulation rate of the non-solvent from the outside during the coagulation of the spinning solution.

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

This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

≪ Example 1 >

Slowly add 20 wt% of polysulfone (PSf, Solvay) to 70 wt% of N, N-dimethylacetamide (DMAc) -containing solvent and gradually add 10 wt% of polyethylene glycol (PEG) as an additive. After mixing to wt%, a uniform spinning solution was prepared at 100 ° C. At this time, the internal coagulant-containing solvent is prepared by adding pure water to N, N- dimethylacetamide (DMAc), in this case, a mixed solution of DMAc / pure water = 80/20 weight ratio was used. When the spinning solution is spun through a spinneret having an annular discharge port, pure water is added to the internal coagulant composition filled in a part of the annular discharge port, thereby acting as an internal coagulant in the spinning solution to help form hollow fibers.

A vacuum pump was used to remove bubbles in the uniform spinning solution prepared above, and the polymer spinning solution was moved to a double nozzle by spinning using a gear pump to prepare a hollow fiber membrane having an outer diameter of about 1.0 mm. At this time, the discharge weight of the spinning solution was 25 g / min, and the air gap was 20 cm. 100% pure water was used as the external coagulant for hollow fiber formation, and the extruded hollow yarn was dipped in pure water, which is an external coagulant maintained at 60 ° C., and solidified, and wound up using a winder at a speed of 20 m / min.

In the experiment, after continuously spinning and coagulating hollow fiber, the hollow fiber was washed for 48 hours in a water washing tank, and then immersed in ethanol and immersed in glycerine solution for one day to remove the remaining organic mixture. Then, dried for one day in room temperature air, to prepare a hollow fiber membrane.

<Example 2>

Instead of the internal coagulant used in Example 1, was prepared in the same manner as in Example 1, except that the mixing ratio of NMP: pure as an internal coagulant was used in an 80: 20 weight ratio to prepare a hollow fiber membrane. .

Comparative Example 1

Instead of the internal coagulant used in Example 1, except that only 100% pure water was used as the internal coagulant, the hollow fiber membrane was prepared in the same manner as in Example 1.

Comparative Example 2

A hollow fiber separator was prepared in the same manner as in Example 1, except that the winding speed during spinning in Example 1 was changed to 7 m / min.

Comparative Example 3

A hollow fiber separator was prepared in the same manner as in Example 1, except that the external coagulant temperature was maintained at 5 ° C. during spinning in Example 1.

Experimental Example 1 Measurement of Oxygen Permeability

20 strands of the hollow fiber separator prepared in Examples 1 to 2 and Comparative Examples 1 to 3 were prepared by measuring a module having a length of 20 cm and an outer diameter of 4 cm. Oxygen permeability performance of the prepared hollow fiber membrane was analyzed using pure oxygen gas (99.9%). Using the hollow fiber membrane, the oxygen gas was permeated at an upper temperature of 1 atm and a lower pressure at room temperature, and then oxygen permeability was measured.

Experimental Example 2 Tensile Strength Measurement

A tensile strength analyzer (LLOYD) was used to measure the tensile strength of the hollow fiber membrane prepared in Examples 1 to 2 and Comparative Examples 1 to 3. At this time, the length of the prepared hollow fiber membrane was 450mm, the test speed was tested at 100mm / min, the results are shown in Table 1.

Experimental Example 3 Macroporosity Measurement

The hollow pores membranes prepared in Examples 1 to 2 and Comparative Examples 1 to 3 were subjected to SEM analysis to calculate macropores having a diameter of 4 μm or more in cross section (number, n). Dividing this by the area (μm ² ) of the cross section of the hollow fiber membrane, the macroporosity per unit area (n / μm ² ) was calculated and the results are shown in Table 1 below.

As shown in Table 1, the hollow fiber membrane prepared in Examples 1 to 2 was prepared a hollow fiber membrane without the macropore, the tensile strength of the hollow fiber membrane of the present invention improved from the structure without the macropore . In particular, the hollow fiber membranes prepared in Examples 1 to 2 showed excellent oxygen permeability, thereby confirming the excellent performance as the hollow fiber membranes for liquid / gas separation.

In more detail, in the same manner as in Example 1 and Example 2, but Comparative Example 1 using only pure water as an internal coagulant, it was confirmed that the macropores 20 / 탆 ² , tensile strength of Example 1 and It was relatively lower than Example 2, and in particular, oxygen permeability was significantly lowered.

In addition, the hollow fiber membrane of Comparative Example 2 prepared by performing the same as the conditions of Example 1, but was carried out at the winding speed of 7m / min, it was confirmed that the macropores 25 / ㎛ ² , tensile strength Was relatively lower than that of Example 1, and in particular, the oxygen permeability was remarkably lowered.

Comparative Example 3 was carried out in the same manner as in Example 1, but was carried out by maintaining the temperature of the external coagulant at 5 ℃, it was confirmed that the macropores 30 / ㎛ ² , tensile strength and oxygen permeability of Example 1 It was significantly lower than the film.

As described above, the present invention provides a hollow fiber membrane for water treatment consisting of only dense micropores without macropores in the hollow fiber membrane structure, thereby reducing membrane pollutant rejection by mechanical pores, weakening mechanical strength, and membrane lifetime. The problem of the fall was solved.

In particular, the present invention provides a high performance hollow fiber membrane useful for liquid / gas separation, as it exhibits excellent oxygen permeability without reducing gas or liquid permeability.

In addition, the present invention provides a manufacturing method that can control the formation of macropores by controlling the spinning conditions, without changing the composition and ratio of the polymer solution used in the manufacturing process of the polymer membrane using a conventional NIPS process or introducing additional processes By using the manufacturing method of the present invention, it can be used in the water purification process and wastewater process as well as gas separation membrane field.

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.

1 is a cross-sectional photograph of a hollow fiber membrane prepared in Example 1 of the present invention,

2 It is a cross-sectional photograph of a polymer membrane using a conventional NIPS method.

Claims (15)

A hollow fiber separation membrane, characterized in that the macropores in the cut surface of the hollow fiber separation membrane is 0 to 20 / ㎛ ² , the oxygen permeability is 10 to 150,000 LMH (L / m ² h) under 1 atm. The hollow fiber separation membrane according to claim 1, wherein the hollow yarn has an outer diameter of 0.4 to 5.0 mm and an inner diameter of 0.1 to 4.8 mm, and has a pore volume of 20% or more. delete The hollow fiber membrane according to claim 1, wherein the hollow fiber membrane is a liquid / gas separation membrane. Dissolving the polymer resin and additives in a solvent to prepare a spinning solution, When the spinning solution is spun through a spinneret having an annular discharge port, after contact with an internal coagulant made of a solvent and a non-solvent filled in a part of the annular discharge port, the outer solution and the temperature difference is maintained within 80 ℃ It discharges and spins to a non-solvent which is a coagulant, When spinning, the manufacturing method of the hollow fiber membrane, characterized in that the winding while maintaining the winding speed at 10m / min or more. The method of claim 5, wherein the winding speed during spinning is 10 to 100 m / min. The method of claim 5, wherein the temperature difference between the spinning solution and the external coagulant is 0 to 80 ℃. The method of claim 5, wherein the solvent weight ratio of the internal coagulant is 30 to 100%. The method of claim 8, wherein the solvent is N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, glycerin, polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol and diethylene glycol Method for producing the hollow fiber membrane, characterized in that the single or mixed form of one or more selected from the group consisting of. The method of claim 5, wherein the non-solvent in the internal coagulant is selected from pure water or alcohols. The method of claim 5, wherein the external coagulant is pure water. The method of claim 5, wherein the polymer resin is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride- trichlorofluoroethylene, polyphenylsulfone, polyethersulfone, polysulfone, poly A method for producing the hollow fiber membrane, characterized in that the single or mixed form selected from the group consisting of acrylonitrile and cellulose acetate. The group of claim 5, wherein the additive is polyvinylpyrrolidone, vinylpyrrolidone, polyethylene glycol, ethylene glycol, diethylene glycol, polyethylene oxide, methoxyethanol, butoxyethanol, tetrahydrofuran and pentanol Method for producing the hollow fiber membrane, characterized in that the single or mixed form selected from one or more. The method of claim 5, wherein the spinning solution contains 45 to 90% by weight of the solvent and 10 to 55% by weight of the mixed content of the polymer resin and the additive. 15. The method of claim 14, wherein the polymer resin and the additive are in a weight ratio of 0.1 to 0.7.

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