KR20140096628A

KR20140096628A - Continuous Process of Preparing Hollow Fiber Membrane Wherein Uniform Bead Structures Are Evenly Formed Throughout the Membrane Using Extruder

Info

Publication number: KR20140096628A
Application number: KR1020130009427A
Authority: KR
Inventors: 이수민; 이준석
Original assignee: 엘지전자 주식회사
Priority date: 2013-01-28
Filing date: 2013-01-28
Publication date: 2014-08-06
Also published as: KR102019466B1

Abstract

The present invention relates to a method for producing a hollow fiber membrane in which a spherical structure of uniform size is uniformly formed over the entire membrane by a continuous process using an extruder. The method of the present invention uses an extruder without using a conventional stirrer type extruder, and the spherical structure formation by spearlite, which is a result of heat-induced phase separation in the membrane cross-sectional structure, So that it is possible to produce a microfiltration hollow fiber membrane having a high strength and a uniform pore size.
The hollow fiber membrane thus obtained is excellent in mechanical strength and water permeability and is suitable for water treatment such as purification, recycling, process water, and ultrapure water pretreatment, and can be used as a support for a hollow fiber ultrafiltration membrane.

Description

Technical Field [0001] The present invention relates to a hollow fiber membrane, and more particularly, to a hollow fiber membrane having uniformly sized spherical structures formed by continuous processes using an extruder,

The present invention relates to a method for producing a hollow fiber membrane in which a spherical structure of uniform size is uniformly formed over the entire membrane by a continuous process using an extruder.

Separation membranes used to separate gases, liquids or solids, especially ionic materials, such as ionic materials, combine dense or porous structures to selectively permeate and exclude certain components, thereby providing selectivity to the removed material, The material is designed to pass through low resistance.

Recently, a technology using a separation membrane having such a structure has been applied to processes for treating water and wastewater. These water treatment membranes are classified into polymer membranes, ceramic membranes, metal membranes and organic / inorganic composite membranes depending on the material. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO) It is divided into membranes.

Meanwhile, a method for producing a separator using a polymer resin includes casting and extrusion spinning a polymer solution containing both solvents and a pore-forming agent at a low temperature at which phase separation by heat does not occur, thereby forming a polymer resin Is coagulated to form a porous structure is generally used. The non-solvent-derived phase separation method has an advantage in that the size of the pores can be freely controlled. However, when finger-like macrovoids are formed, the mechanical strength of the separation membrane is low, .

As another method, the heat-induced phase separation method is a method of mixing a polymer resin with a poor solvent and spinning at a temperature elevated to a temperature above the temperature at which the phase separation occurs by heat, thereby cooling and solidifying the polymer. It is common to have spherical structure by spherulite. Such a heat-induced phase separation method has an advantage in that it is easy to manufacture a separation membrane having a high mechanical strength, but it is difficult to reduce the pore size.

In this regard, Korean Patent No. 10-1179161 discloses a process for producing a polyvinylidene fluoride (PVDF) resin, a pore-forming agent, a good solvent and a poor solvent by melting and mixing in a reactor, And a method of producing a hollow fiber membrane in which cells are connected to each other. However, the above-mentioned technique has disadvantages in that the spherical size of the prepared membrane cross-sectional structure is as large as 5 to 10 탆 or more, so that the porosity is high but the strength is weak. Also, as a discontinuous film-forming method using a reactor, It is difficult to control the temperature of the pipe connected to the nozzle when the temperature of the solution is increased and the temperature of the pipe connected to the nozzle is controlled.

Accordingly, there is a demand for a hollow fiber membrane manufacturing technology capable of appropriately controlling the shape and pore size and shape of the membrane by controlling the manufacturing parameters according to the type of polymer and diluent and the phase separation process, while securing excellent productivity in a continuous process exist.

Numerous papers and patent documents are referenced and cited throughout this specification. The disclosures of the cited papers and patent documents are incorporated herein by reference in their entirety to better understand the state of the art to which the present invention pertains and the content of the present invention.

Korean Patent No. 10-1179161

The present inventors have made efforts to develop a method for simultaneously securing high strength and high permeability by effectively controlling the structure of a separator while ensuring excellent productivity by using a continuous process method without using a conventional extruder of the stirrer type. As a result, by adopting the continuous process using the compressor and the heat-induced phase separation using the poor solvent and effectively controlling the spherical structure by spear light, the hollow spherical structure having the uniformly sized spherical structure uniformly formed on the whole membrane, Thereby completing the invention.

Accordingly, an object of the present invention is to provide a method for producing a hollow fiber membrane in which a spherical structure of uniform size is evenly formed on the entire membrane by a continuous process using an extruder.

Another object of the present invention is to provide a high-permeability, high-strength hollow fiber membrane having uniformly sized spherical structures uniformly formed on the entire membrane.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims and drawings.

According to one aspect of the present invention, there is provided a method for producing a hollow fiber membrane having a structure in which a uniform spherical structure having a uniform particle size within a range of 0.5 to 3 탆 is formed uniformly throughout the membrane, Feeding a raw material containing polyvinylidene fluoride (PVDF) based resin and a poor solvent to an extruder; (ii) mixing and melting the supplied materials by rotation of the screw cylinder and the cylinder temperature of the extruder; And (iii) extruding and spinning the mixed solution.

The present invention overcomes the disadvantages of the conventional non-solvent-derived phase separation method and the method of manufacturing a polyvinylidene divinylbenzene separator by the heat-induced phase separation method, and the characteristics of the produced membrane, and adopts a continuous process using an extruder and heat- The spherical structure of the hollow fiber membrane was effectively controlled, and as a result, a spherical structure having a uniform size within a range of 0.5 to 3 μm was formed to have a uniform cross-sectional structure distributed over the entire membrane, At the same time, the mechanical strength could be increased.

Spherical structure formed by spearlite is always formed. In order to secure both high strength and high permeability at the same time, it is necessary to control the structure so that the sphere is not excessively adhered and the strength of the film is not weakened at the same time Most importantly, the method of the present invention ensures that the spherical shape is uniformly distributed throughout the membrane while allowing the spherical structure to be evenly distributed over the membrane at appropriate intervals without over-tightening. At the same time, since the spherical shape is formed to have a small diameter of 3 占 퐉 or less, excellent strength can be ensured at the same time. Hereinafter, each step of the method of the present invention will be described in detail.

(i) Polyvinylidene fluoride ( PVDF ) Based resin and Poor solvent Feeding the raw material containing therein to the extruder

Among these components, the polyvinylidene resin (PVDF), which is the first polymer, may have a weight average molecular weight of 250,000 to 400,000, preferably 20 to 50% by weight, more preferably 30 to 40% It can be used in quantities. Polyvinylidene fluoride (PVDF) may be dried in a dehumidifying dryer at a drying temperature of 40 to 90 ° C prior to being fed to the extruder.

A poor solvent among the above-mentioned components means a solvent having a weak ability to dissolve a polymer, meaning that the interaction energy between the solvent and the polymer is smaller than the average of the interaction energy between the solvent molecules. In one embodiment, the poor solvent may include gamma-butylolactone (GBL), ethylene glycol (EG), propylene glycol, diethylene glycol (DEG), triethylene glycol (TEG), dipropylene glycol (DPG), glycerol, Maleic anhydride, propylene carbonate (PC), or a combination thereof may be used, but the present invention is not limited thereto.

Preferably, the raw material may further comprise a hydrophilic resin, which is mixed together to complement the low miscibility of the polyvinylidene resin with water and to perform its function as a pore former. A hydrophilic resin is a polymer having a polar or charged functional group so as to have compatibility with water and can be used without limitation as long as it satisfies these conditions. Examples of the hydrophilic resin include polyvinylpyrrolidone (PVP), polyphenylene glycol (PEG), acrylamide resin, other acrylic resins, amine resins such as allylamine, ethyleneimine and oxazoline, But it is not necessarily limited thereto.

Also in one embodiment, the raw material is characterized in that it does not contain an inorganic pore-former. When an inorganic fine powder such as silica, alumina, titanium oxide or the like is used in the formation of a large amount of an inorganic pore forming agent, an additional process for removing the inorganic fine powder after the film formation is required. As a result, The object of the present invention can not be achieved.

The continuous process using the extruder of the present invention can be carried out without using the above-mentioned inorganic pore-forming agent, even if the spherical structure formed by spearlite is not overly concentrated and uniformly distributed at suitable intervals and the particle size is high It is possible to form uniform pores with uniformity.

In a preferred embodiment, the content and the weight percentage of each component contained in the raw material may be as follows.

First polymer (P1): 30 to 40% by weight of polyvinylidene resin (PVDF)

Second polymer (P3): 5 to 20% by weight of polyphenylene glycol (PEG)

The first poor solvent (S1): 10 to 30% by weight of? -Butylolactone (GBL)

Second poor solvent S2: 10 to 30% by weight of propylene carbonate (PC)

In addition to the above-mentioned components, additives for the purpose of imparting porosity, imparting strength, imparting other functions and the like can be supplied to the extruder together. The polymer component of these components is mixed with polyvinyl fluoride vinylidene resin, A poor solvent and a hydrophilic polymer such as polyethylene glycol (PEG) having a low molecular weight may be supplied to the extruder through a liquid pump.

( ii ) The cylinder temperature of the extruder Screw Mixing and melting the supplied materials by rotation,

Membrane preparation As a mixing step of the polymer solution raw materials, all mixing processes are carried out in the cylinder screw of the extruder. Although it is possible to use a single-screw extruder, it is preferable to use a twin-screw extruder to increase the mixing efficiency.

In one embodiment, the cylinder of the extruder can be temperature controlled for each cylinder, and each temperature can be controlled within 50 to 250 DEG C in consideration of the melting point of the polymer resin. Specifically, the portion where the polymer solvent enters may be adjusted to about 50 캜, the melting zone to about 150 to 200 캜, and the portion to be discharged to about 110 to 140 캜.

In order to increase the mixing efficiency, the configuration of the segment of the screw can be optimized. For example, the rotational speed of the screw can be adjusted to 150 to 300 rpm. In this case, the supplied materials are simultaneously melted while being mixed by the rotation of the screw and the temperature of the cylinder.

( iii ) The mixed solution was extruded and Radiant step

This is a step of extruding and spinning the mixed solution. The polymer solution mixed and melted by screw rotation of the cylinder is extruded and transferred to the gear pump, and the polymer solution is extruded and radiated through the nozzle by the metering gear pump And preferably, the mixed solution can be radiated together with the inner coagulating liquid.

The method of the present invention may further comprise cooling and solidifying the radiated solution through the coagulation bath in addition to the steps (i) to (iii) described above.

Another aspect of the present invention is to provide a high permeability, high strength hollow fiber membrane characterized in that a spherical structure having a uniform size within a range of 0.5 to 3 占 퐉 in particle size is uniformly formed throughout the membrane.

The hollow fiber membrane of the present invention formed by forming the raw material containing the polyvinylidene fluoride (PVDF) resin and the poor solvent by adopting the continuous process using the extruder and the heat-induced phase separation is characterized in that the result of the heat- Spherulite formation by spherulite can be controlled to a range of 3 탆 or less, that is, 0.5 to 3 탆.

In addition, the hollow fiber separator of the present invention is characterized in that a spherical structure having a uniform size is evenly distributed over the entire film, and the pore size as a whole is extremely uniform.

Thus, the spherical structure of 0.5 to 3 탆 is uniformly distributed at appropriate intervals without being overly dense, and the uniformity of the particles is very high throughout the film, so that the resistivity of the water flow can be minimized. Therefore, the hollow fiber membrane of the present invention can attain excellent mechanical strength and water permeability at the same time, and as a result, it is very suitable for water treatment such as purification, reuse, process water, and ultrapure water pretreatment.

In addition, since the resistance of the water flow can be minimized while being excellent in mechanical strength, it can be used particularly as a precursor of a hollow fiber ultrafiltration membrane.

The method of the present invention uses an extruder to produce a separator by a continuous process without using a conventional stirrer-type extruding machine, and a spherulite, which is a result of heat-induced phase separation in the cross- To adjust the spherical structure formation to 0.5 to 3 탆, thereby making it possible to produce a microfiltration hollow fiber membrane having a uniform pore size of high strength.

The hollow fiber membrane thus obtained is excellent in mechanical strength and water permeability, and is suitable for water treatment such as purification, re-use, process water, and ultrapure water pretreatment. Especially, it can be used as a precursor of a hollow fiber ultrafiltration membrane.

1 is a scanning electron microscope (SEM) image of a separation membrane prepared in Example 1 (Fig. 1A: separation membrane section, Fig. 1B: enlarged separation membrane section, Fig. 1C: separation membrane surface enlarged).
FIG. 2 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 2 (FIG. 2A: enlarging the cross section of the separation membrane; FIG. 2B: enlarging the surface of the separation membrane).
Fig. 3 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 3 (Fig. 3a: enlarging the cross section of the separation membrane; Fig. 3b: enlarging the surface of the separation membrane).
FIG. 4 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 4 (FIG. 4A: enlarging the cross section of the separation membrane; FIG. 4B: enlarging the surface of the separation membrane).
5 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 5 (Fig. 5A: enlarging a cross section of the separation membrane; and Fig. 5B: enlarging the surface of the separation membrane).
FIG. 6 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 6 (FIG. 6A: enlarging the cross section of the separation membrane; and FIG. 6B: enlarging the surface of the separation membrane).
FIG. 7 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 7 (FIG. 7A: enlarged sectional view of the separation membrane; and FIG. 7B: expanded surface of the separation membrane).
FIG. 8 is a scanning electron microscope (SEM) image of the separation membrane prepared in Example 8 (FIG. 8A: enlarging the cross section of the separation membrane; and FIG. 8B: enlarging the surface of the separation membrane).

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be construed as limiting the scope of the present invention. It will be self-evident.

Example

Example One

40% by weight of polyvinylidene fluoride resin PVDF (solvay 6010 grade, molecular weight 322 kDa), 20% by weight of gammabutylolactone (GBL), 20% by weight of propylene carbonate (PC) and 20% by weight of polyethylene glycol The mixing ratio was determined, the polyvinylidene resin was fed into the hopper of the extruder, and the GBL, PC and PEG were fed to the cylinder of the extruder through the liquid feed pump. The temperatures of the zones 0 to 9 (C0 to C9) of the extruder were set according to each composition and composition ratio. The screw rotation speed was 300 times / min. The mixed material in the extruder cylinder was melt extruded in a twin-screw extruder and then finally radiated through a gear pump and nozzle into a coagulation bath. The outer diameter and the inner diameter of the nozzle were 2.0 mm and 1.2 mm, respectively, and the distance between the nozzle and the coagulation tank was set to 50 mm. (GBL: EG (ethylene glycol) = 8: 2) was used as the internal coagulation solution. A mixture of external coagulation solution (GBL: PC: D.I. = 4: 1: 1) was used and the temperature of the coagulating solution was set at 20 ° C. The hollow fiber membrane through the coagulation bath was extracted from the washing bath for more than one day and then dried at room temperature to produce the hollow fiber membrane product of the present invention.

The PVDF hollow fiber membrane prepared by the above method had an outer diameter in the range of 1 to 1.2 mm and an inner diameter in the range of 0.5 to 0.8 mm. The tensile strength was 12.32Mpa, the elongation was 20%, and the mechanical strength was excellent. The average pore size of hollow fiber membranes measured by permporometer (PMI) was 0.14 ㎛. It was also confirmed that the membrane was a microfiltration membrane having a net permeation flow rate of 790 L / m 2 · hr and a porosity of 65% at 1 bar and 25 ° C.

SEM photographs of the prepared separation membranes are shown in FIG. 1 (FIGS. 1A to 1C) in which there is no fingers and spherical structures as a whole are connected, and spherical particles have a diameter of about 2 .mu.m Respectively. In addition, it was confirmed that the diameter of the bead particles distributed over the entire separation membrane was almost the same, and the dispersity of the particles was very high.

Example 2

The same procedure as in Example 1 was carried out except that the PEG concentration was changed to 15%.

Example 3

The same procedure as in Example 1 was carried out except that the PEG concentration was changed to 10%.

Example 4

The same procedure as in Example 1 was carried out except that the PEG concentration was changed to 5%.

Example 5

The composition of the polymer solution and the composition ratio were PVDF 40% and GBL 60%.

Example 6

The composition and composition ratio of the polymer solution were PVDF 40%, GBL 42% and DEG 18%.

Example 7

The same procedure as in Example 1 was carried out except that the polymer solution temperature was set to 120 ° C under the same conditions.

Example 8

The same procedure as in Example 1 was carried out except that the polymer solution temperature was set to 100 ° C under the same conditions.

The basic physical properties measured for the membranes prepared in Examples 1 to 8 are summarized in Table 1 below. The content of each component of the present invention is not limited to the values shown in Table 1, Based on reasonable summary and reasoning. The parameters in Table 1 are only one embodiment of the present invention and should not be construed as an essential condition of the present invention.

Number of embodiment One 2 3 4 5 6 7 8 Polymer solution composition and composition ratio PVDF (%) 40 40 40 40 40 40 40 40 PEG (%) 20 15 10 5 - - 20 20 GBL (%) 20 22.5 25 27.5 60 42 20 20 PC (%) 20 22.5 25 27.5 - - 20 20 DEG (%) - - - - - 18 - - Polymer solution temperature (캜) 110 110 110 110 110 110 120 100 Air gap (mm) 50 50 50 50 50 50 50 50 Composition of cooling liquid GBL (%) 66.6 66.6 66.6 66.6 66.6 66.6 66.6 66.6 PC (%) 16.7 16.7 16.7 16.7 16.7 16.7 16.7 16.7 D.I. (%) 16.7 16.7 16.7 16.7 16.7 16.7 16.7 16.7 Cooling temperature (℃) 20 20 20 20 20 20 20 20 Average pore size (占 퐉) 0.15 0.38 0.09 0.25 0.30 0.16 0.10 0.31 Pure permeate flow rate (L / m2h) 790 1250 196 352 425 845 542 957 Tensile Strength (MPa) 12.32 7.40 11.18 12.90 7.52 7.96 11.40 13.10 Spherical particle diameter (占 퐉) 2.0 1.0 1.0 2.2 1.8 1.8 3.0 1.0

Claims

A method for producing a hollow fiber membrane in which a spherical structure having a uniform size within the range of 0.5 to 3 占 퐉 is formed uniformly throughout the membrane by continuous process using an extruder,
(i) feeding a raw material containing a polyvinylidene fluoride (PVDF) based resin and a poor solvent to an extruder;
(ii) mixing and melting the supplied materials by rotation of the screw cylinder and the cylinder temperature of the extruder; And
(iii) extruding and spinning the mixed solution.

The method of claim 1, wherein the raw material further comprises a hydrophilic resin.

The method of claim 1, wherein the source material does not comprise an inorganic pore former.

The method of claim 2, wherein the hydrophilic resin is selected from the group consisting of polyvinylpyrrolidone (PVP), polyphenylene glycol (PEG), acrylamide resin, acrylic resin, amine resin, polyetherimide (PEI) , Polyamide (PA), and cellulose acetate (CA).

The method of claim 1, wherein the temperature of the cylinder is adjusted to 50 to 250 占 폚.

The method of claim 1, wherein the rotational speed of the screw is adjusted to 150 to 300 rpm.

The method according to claim 1, wherein in (iii), the mixed solution is radiated together with an inner coagulating solution.

The method of claim 1, further comprising cooling and solidifying the solution sparged in (iii) through a coagulation bath.

Characterized in that a spherical structure having a uniform size within a range of 0.5 to 3 占 퐉 in particle size is formed uniformly throughout the membrane.

The hollow fiber membrane of claim 9, wherein the hollow fiber membrane is to be used as a support for an ultrafiltration membrane.