KR20070102012A - Hydrophilic and porous poly(vinylidene fluoride) hollow fiber membranes with rod-like particulates and methods to make membranes - Google Patents

Abstract

A hydrophilic and porous type poly(vinylidene fluoride) hollow fiber membrane and a method for manufacturing the same are provided to improve water permeability of the hollow fiber membrane, by distributing spherical particles and rod-shaped particles in the hollow fiber membrane. A hydrophilic and porous type hollow fiber membrane comprises a plurality of rod-shaped particles and a plurality of spherical particles. The rod-shaped particles have an average diameter of about 5 um, and lengths of more than 5 um. The spherical particles have an average diameter of less than 5 um. The hydrophilic and porous type hollow fiber membrane has an external diameter of 0.8-1.2 um, and a membrane thickness of 0.1-0.4 mm.

Description

 Hydrophilic and porous poly (vinylidene fluoride) hollow fiber membranes with rod-like particulates and methods to make membranes}

1 is an electron scanning microscope photograph of a 1000-fold magnification of the surface of a polyvinylidene fluoride-based porous hollow fiber containing 2% by weight of a hydrophilic inorganic additive according to an embodiment of the present invention.

Figure 2 is an electron scanning microscope photograph of a 1000-fold magnification of the surface of the polyvinylidene fluoride-based porous hollow fiber containing 8% by weight hydrophilic inorganic additives according to an embodiment of the present invention.

3 is an electron scanning microscope photograph of a 70-fold magnification of the entire cross-section of a polyvinylidene fluoride-based porous hollow fiber containing 8 wt% hydrophilic inorganic additive according to one embodiment of the present invention;

4a and 4b schematically illustrate the membrane cross-section (a) and the membrane surface (b) of the entire structure of the polyvinylidene fluoride-based porous hollow fiber membrane containing 8% by weight of a hydrophilic inorganic additive according to an embodiment of the present invention Schematic diagram.

5 is an electron scanning microscope photograph of a 2,000 times magnification of the surface of a polyvinylidene fluoride-based porous hollow fiber without a hydrophilic inorganic additive of a conventional comparative example.

FIG. 6 is an electron scanning microscope photograph of a 90-fold enlarged overall cross section of a polyvinylidene fluoride-based porous hollow fiber without a hydrophilic inorganic additive of a conventional comparative example. FIG.

The present invention relates to a hydrophilized polyvinylidene fluoride-based porous hollow fiber membrane and a method for manufacturing the same, and more particularly, including rod-shaped particles on the cross-section of the membrane, having a suitable mechanical strength and at the same time excellent water permeability due to hydrophilicity It relates to a polyvinylidene fluoride-based porous hollow fiber membrane and a method for producing the same.

Recently, a variety of membranes and membrane separation processes using the same have been actively developed for various energy saving and environmental protection. In particular, membranes such as ultrafiltration membranes and microfiltration membranes are applied to a wide range of fields, including wastewater treatment, water production, food and medical industries, and the application of the membranes is increasing with increasing interest in drinking water.

For example, in the water treatment field, a high permeability and high pressure resistant membrane capable of treating a large amount of water with a small membrane area is required. In addition, in order to fundamentally prevent the problem of degradation of permeation performance due to contamination of the membrane surface during long-term operation, a membrane material having excellent fouling resistance is required. On the other hand, in order to suppress the problem of membrane damage caused by the introduction of various water treatment agents for easily removing contaminants attached to the membrane surface, there is a further demand for a membrane material having excellent chemical resistance. In order to fundamentally solve these various problems, a film material that has recently attracted attention is a polyvinylidene fluoride-based polymer. As is widely known, polyvinylidene fluoride-based materials have been widely used for coatings, piezoelectric materials, and separation materials for a long time because they are well known to have excellent mechanical and chemical properties compared to other polymer materials.

However, due to the inherent low surface energy of the polymer, it is very difficult to avoid a decrease in water permeability resulting from contamination by organic substances such as proteins during long-term operation. Accordingly, various means for hydrophilizing polyvinylidene fluoride-based porous hollow fiber membranes have been proposed.

For example, Korean Patent Publication No. 2005-0056245 discloses a method of inducing radical generation of hydrophilic vinyl monomers by irradiating polyvinylidene fluoride microporous membranes with ionizing radiation and then graft polymerizing these radicals on the membrane surface. The formation of a hydrated film is disclosed. In addition, Korean Patent Publication No. 2006-0003347 discloses a hydrophilized polyvinylidene fluoride resin prepared by copolymerizing a hydrophilic monomer containing an epoxy group, a hydroxyl group, a carboxyl group, an ester group, and an amide group with a polyvinylidene fluoride monomer through suspension polymerization. A porous membrane is disclosed. In addition, Korean Patent Publication No. 2005-0078747 discloses a preparation example of a nanocomposite hollow fiber membrane containing hydrophilized organic clay. In addition, examples of preparing hydrophilized polyvinylidene fluoride-based porous membranes through chemical treatment with alkalis and oxidizing agents are also disclosed.

However, such prior art uses additional processes such as polymerization, expensive processes such as the use of radiation, and the like, and especially chemical treatment methods often impair the mechanical strength inherent in polyvinylidene fluoride-based resins. Therefore, it is more desirable to produce a porous membrane which is not deteriorated in mechanical strength while improving the water permeability due to hydrophilization.

Therefore, the inventors of the present invention provide a hollow fiber membrane having excellent water permeability and good tensile strength from a hydrophilized polyvinylidene fluoride-based polymer without a complicated and additional process such as drawing, to solve the conventional technical problems. Efforts have been made to produce a porous membrane structure consisting of spherical particles of several to tens of micrometers across the entire cross section of the membrane, while at the same time suitable for the outer surface of the membrane with a large number of diameters of tens to tens of microns The present invention was completed by preparing a hollow fiber membrane having fine water permeability at the same time by finely adjusting in one process to be positioned.

Accordingly, an object of the present invention is to provide a hydrophilized porous polyvinylidene fluoride-based hollow fiber membrane having excellent water permeability and high mechanical strength through a simple manufacturing process and low cost without additional processes such as stretching in terms of performance of the membrane. .

Another object of the present invention is to provide a porous polyvinylidene fluoride-based hollow fiber membrane having excellent water permeability by distributing spherical particles of several to several tens of microns evenly across the membrane cross-section.

It is still another object of the present invention to provide a porous polyvinylidene fluoride-based hollow fiber membrane having excellent mechanical performance and water permeability by forming a hydrophilized rod-like structure having a diameter of several tens of microns.

Another object of the present invention is to provide a method for producing a polyvinylidene fluoride-based porous hollow fiber membrane having low membrane fouling rate and excellent chlorine resistance through the formation of a hydrophilized rod-like structure.

In order to achieve the above object, the present invention has an average particle diameter of about 5 micrometers (µm), a plurality of rod-shaped particles having a length of 5 micrometers (µm) or more, and a number of average particles of 5 micrometers (µm) or less It provides a hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane containing a spherical particle of.

In addition, the present invention a) preparing a spinning solution comprising a polyvinylidene fluoride-based polymer, a hydrophilic inorganic additive and a solvent,

b) The spinning solution is transferred to an outer tube of a double nozzle maintaining a temperature of at least 100 ° C. or higher, and then discharged into an external coagulation liquid containing a good solvent and a non-solvent maintained at 40 ° C. or lower, and the amount of room temperature Manufacturing a hollow fiber membrane by transferring a hollow forming agent including a solvent, a non-solvent, and a polymer into the inside of the double nozzle;

It provides a method for producing a hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane comprising a.

More preferably, the method for producing a porous hollow fiber of the present invention

a) a polyvinylidene fluoride polymer, a hydrophilic inorganic additive, and a solvent for dissolving and dispersing the polyvinylidene fluoride resin and a hydrophilic inorganic additive substantially uniformly at 100 to 180 ° C. to prepare a spinning solution,

b) the spinning solution is transferred to an outer tube of a double nozzle maintained at a temperature of 100 to 180 ° C., followed by a mixture of a good solvent and a non-solvent for the polymer, and is kept at -40 to 40 ° C. At the same time as discharging in a solid solution, a hollow spherical agent containing a mixture of a good solvent, a non-solvent, and a polymer at room temperature is discharged into the inner tube of the double nozzle to form a fine spherical porous inner layer from the hollow center of the hollow fiber membrane toward the outermost surface; Forming a hollow fiber membrane comprising a two-layer structure of an outer surface layer composed of rod-shaped particles; And c) washing the hollow fiber membranes with water.

In the following, the present invention is described in more detail.

The porous hollow fiber of the present invention comprises a plurality of tens of micrometers of rod-shaped particles and a plurality of spherical particles. Preferably, the hollow fiber membrane of the present invention includes rod-shaped particles and spherical particles from the hollow center of the hollow fiber membrane to the outside in the cross section on the surface layer of the hollow fiber membrane without a dense layer as in the prior art, wherein the rod-shaped particles have a cross-sectional shape. It is contained in the surface layer of. Therefore, the present invention has excellent water permeability and high mechanical strength through a simple manufacturing process and low cost without additional processes such as stretching in terms of the performance of the membrane, spherical particles of several to several tens of microns in size are distributed evenly across the membrane In addition to exhibiting excellent water permeation performance, it is possible to provide a hydrophilic membrane having excellent mechanical performance, low membrane fouling rate, and excellent chlorine resistance by forming a hydrophilized rod-like structure of several tens of microns in size.

Hereinafter, with reference to the accompanying drawings illustrating a preferred embodiment of the hollow fiber membrane of the present invention.

1 is an electron scanning microscope photograph of a 1000-fold magnification of the surface of a polyvinylidene fluoride-based porous hollow fiber containing 2 wt% hydrophilic inorganic additive according to an embodiment of the present invention. FIG. 2 is an electron scanning microscope photograph of a 1000-fold magnification of the surface of a polyvinylidene fluoride-based porous hollow fiber containing 8 wt% of a hydrophilic inorganic additive according to an embodiment of the present invention. FIG. 3 is an electron scanning microscope photograph of a 70-fold magnification of the entire cross-section of a polyvinylidene fluoride-based porous hollow fiber containing 8 wt% of a hydrophilic inorganic additive according to an embodiment of the present invention. 4a and 4b schematically illustrate the membrane cross-section (a) and the membrane surface (b) of the entire structure of the polyvinylidene fluoride-based porous hollow fiber membrane containing 8% by weight of a hydrophilic inorganic additive according to an embodiment of the present invention It is a schematic diagram.

As shown in Figs. 1 to 4B, the hollow fiber membrane of the present invention has an average particle diameter of about 5 micrometers (µm), a plurality of rod-shaped particles having a length of 5 micrometers (µm) or more, and an average particle diameter over the membrane cross section. It contains a plurality of spherical particles up to 5 micrometers (μm). At this time, as shown in Figure 2, in the hollow fiber membrane of the present invention, a large number of rod-shaped particles and a few spherical particles may be present on the surface by the hydrophilic inorganic concentration. In Figs. 4A and 4B, reference numeral 1 denotes an inner porous layer composed of spherical particles on the membrane cross section, 2 denotes an outer surface layer composed of rod-shaped particles, 3 denotes rod-shaped particles on the surface of the hollow fiber membrane, and 4 denotes a spherical shape. Particles are shown and include a two-layered structure of rod-shaped particles and spherical particles.

The hollow fiber membrane of the present invention having the above structure is formed by using a hollow forming agent at room temperature while simultaneously discharging a spinning solution of 120 ° C. or higher to an external coagulation solution of 40 ° C. or lower, and the spinning solution is a polyvinylidene fluoride-based polymer. , Hydrophilic minerals and solvents. In addition, the external coagulant may include a good solvent and a non-solvent, and the hollow forming agent may include a good solvent, a non-solvent, and a polymer.

In the present invention, the rod-shaped particles are exposed to the surface of the membrane and are evenly distributed outwardly from the hollow center of the membrane. The rod-shaped particles are located above the spherical particles on the cross section, and their average particle diameter is about 5 micrometers in length. It is defined as 5 micrometers or more. In addition, the spherical particles are generally distributed on the cross section of the membrane from the hollow center to the outside, and are located below the rod-shaped particles, and are defined as having an average particle diameter of 5 micrometers or less.

In the present invention, the rod-shaped particles and the spherical particles are preferably included in the weight ratio of 60 to 90 and 10 to 40.

The average particle diameter of the rod-shaped particles is 1 to 10 μm and the length is 1 to 100 μm, respectively, and the average particle diameter of the spherical particles is preferably 1 to 10 μm.

In addition, it is preferable that the outer diameter of the hollow fiber membrane is 0.8 to 1.2 mm, the inner diameter is 0.4 to 0.6 mm, and the film thickness is 0.1 to 0.4 mm.

The hollow fiber membrane of the present invention has a net permeability of at least 5,000 l / m ² hr or more.

On the other hand, the method of producing a porous hollow fiber membrane of the present invention, a) polyvinylidene fluoride-based polymer, a hydrophilic inorganic additive and a solvent to prepare a spinning solution, b) the amount of the spinning solution at a temperature of at least 120 ℃ or more Preparing a hollow fiber membrane by using a hollow former composed of a good solvent, a nonsolvent, and a polymer, while discharging to an external coagulating solution maintaining a temperature of at least 40 ° C. consisting of a solvent and a non-solvent. do. Through this step, a plurality of rod-shaped particles and spherical particles are simultaneously formed on the membrane cross section.

Hereinafter, the manufacturing process of the hollow fiber membrane of this invention is demonstrated concretely.

(a) Manufacturing process of spinning solution

As described above, in the present invention, the spinning solution is composed of a polyvinylidene fluoride resin, a hydrophilic inorganic additive, and a solvent for forming a hollow fiber membrane, and refers to a uniform mixture without forming precipitates or suspended solids at a temperature of 100 ° C. or higher. Therefore, in the present invention, the spinning solution is preferably prepared at 100 to 180 ° C., and is generally present as a polymer solution having a uniform composition at a temperature of 100 ° C. or more, and forms a hollow fiber membrane by phase separation upon contact with a non-solvent. Promote. In addition, at the time of formation of a hollow fiber membrane, it is preferable to discharge a spinning liquid to an external coagulating liquid through the nozzle which maintains the temperature of at least 100 degreeC or more, Preferably it is 120-180 degreeC.

In the spinning solution, the composition ratio of each component is preferably 25 to 55% by weight of the polyvinylidene fluoride polymer, 1 to 10% by weight of the hydrophilic inorganic additives and 35 to 74% by weight of the solvent based on the total spinning solution composition , More preferably, it is comprised of 30 to 45 weight% of a polymeric material, 2 to 8 weight% of inorganic additives, and 47 to 68 weight% of a solvent.

In this case, when the content of the polyvinylidene fluoride-based polymer is less than 25% by weight, it is impossible to manufacture a continuous membrane due to low viscosity and single yarns, and a hollow fiber membrane having a very low tensile strength is produced, even though manufactured by 55% by weight. If exceeded, the production of the membrane is almost impossible due to the high viscosity of the spinning solution, and the prepared membrane also exhibits low water permeability.

The polyvinylidene fluoride-based polymer may be a homopolymer or a copolymer, but is preferably a single polymer such as polyvinylidene fluoride (PVDF), hexafluoropropylene (PVDF-HFP) or chlorotrile in the polymer. It may be selected from the group consisting of copolymers containing fluoroethylene (PVDF-TCFE) and the like and mixtures thereof. In addition, the polyvinylidene fluoride-based polymer is more preferably used a mixture of a single polymer and a copolymer rather than a homopolymer in order to improve the mechanical strength, such as tensile strength, when using a mixture, the ratio of the single polymer is 5 to 50 More preferably used in weight percent. Moreover, it is preferable that it is the weight average molecular weight of 50,000-500,000 or less about all the polymers with respect to molecular weight, More preferably, it is good to use 100,000-400,000 or less.

As the hydrophilic inorganic additive used in the present invention, it is preferable to use a hydrophobic montmorillonite having a layered structure as the aluminum-silicate component. The montmorillonite may be hydrophilized by conventional methods before use (Cammer, 2005, Vol. 17, pages 1691-1697). As an example of the hydrophilization method, montmorillonite initially modified in sulfuric acid or hydrochloric acid in proton form is silane containing a hydrophilic group such as amine group, carboxyl group, sulfonic acid group, hydroxyl group, chloride group, epoxy group in toluene solvent. By condensation with the series monomers can be prepared more montmorillonite. Examples of the silane-based hydrophilic monomer include merctopropyltrimethoxysilane (-SH), hydroxypropyl trimethoxysilane (-OH), aminopropyltrimethoxysilane (-NH ₂ ), and chloropropyltrimethoxy Silane (-Cl), carboxypropyltrimethoxysilane (-COOH), trimethoxysilylpropylethylenediamine (-NHCH ₂ CH ₂ NH ₂ ), trimethoxysilylpropyldiethylenetriamine (-NHCH ₂ CH ₂ NHCH ₂ CH ₂ NH ₂ ), trimethoxysilylpropylurea (-NHCONH ₂ ), epoxypropyltrimethoxysilane (-COC), and the like. As described above, the hydrophilic inorganic additive is used in an amount of 1 to 10% by weight, more preferably in an amount of 2 to 8% by weight. When the content of the hydrophilic inorganic additive is less than 1% by weight, it is difficult to observe the formation of hydrophilic and rod-shaped particles, and when it exceeds 10% by weight, it is difficult to uniformly disperse the inorganic material. In the structure of the membrane, the rod-shaped particles are formed by the addition of the inorganic material, and rod-shaped particles are not formed unless the inorganic material is added. Therefore, the formation of rod-shaped particles is formed by crystallization and gelation through hydrogen bonding or ion-dipole interaction between the hydrophilic inorganic material and the polyvinylidene fluoride polymer. In addition, hydrophobic montmorilite before reforming may be used to form rod-shaped particles, but rod particles are not well formed due to low dispersion, and it is more preferable to use hydrophilized montmorillonite to obtain high water permeability. .

In addition, according to the present invention, for uniform dispersion of the inorganic additive, it is preferable that a certain amount of the inorganic additive is previously dispersed in a certain amount of the solvent. Ultrasonic waves can also be used for efficient dispersion. The homogeneously dispersed inorganic additives are added to a homogeneously dissolved polymer solution with a continuous amount of other solvents, which method is particularly preferred for uniform dispersion of the inorganic additives in the polymer solution.

The solvent used in the preparation of the spinning solution may be defined as uniformly dissolving and dispersing 55% by weight or less of polyvinylidene fluoride resin at a high temperature of 100 ° C or higher. Solvents that can be used include γ-butyrolactone, cyclonuxanone, 3-hexanone, 3-heptanone, 3-octanone, N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide, dimethylformamide and 2 Mixtures of species or more. For the formation of spherical particles of more uniform size, more preferably γ-butyrolactone is used. A polyvinylidene fluoride polymer solution containing such a solvent is generally present as a polymer solution having a uniform composition without forming spherical particles at a temperature of 100 degrees or higher, and when spherical particles are separated by solid-liquid phase separation upon cooling to room temperature. Expressed to have.

(b) Preparation of hollow fiber membranes

(Composition of External Coagulant and Temperature Control of Coagulant)

In the present invention, a hollow fiber membrane having a two-layer structure including rod-shaped particles and spherical particles is prepared by discharging the spinning solution prepared above to an external coagulation solution and simultaneously using a hollow forming agent.

At this time, the external coagulation solution used in the present invention is composed of a non-solvent containing a certain amount of a good solvent, a large number of rod-shaped particles in the outer membrane layer by rapidly reducing the concentration of the polymer at the interface upon contact with a solvent in the spinning solution And a role of promoting the formation of spherical particles. In addition, the non-solvent is defined as being capable of being uniformly mixed with the good and poor solvents without substantially dissolving the polymer at all over the entire temperature range. The good solvent may be defined as completely dissolving the polyvinylidene fluoride polymer and the hydrophilic inorganic additive up to 55% by weight at a temperature of 60 ° C. uniformly without formation of a precipitate. Preferably, the good solvent uses dimethylacetamide. Examples of the non-solvent include glycerol, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol and mixtures thereof, and more preferably ethylene glycol.

The selection of such external coagulant provides an advantage that the temperature control range of the coagulant can be expanded in various ways compared to using conventional water, and the formation of a porous layer having a distribution of particles of different sizes inside and outside. Very advantageous.

The composition ratio of the external coagulation solution is preferably 10 to 60% by weight and non-solvent 40 to 90% by weight relative to the total solvent mixture, more preferably 30 to 55% by weight of the good solvent and 45 to 70 Non-solvent by weight percent. If the content of the good solvent is out of the composition range, it is impossible to form the hollow fiber membrane by dissolving the membrane, or a dense layer is formed on the inner and outer surfaces to form a hollow fiber membrane having a very low water permeability.

The temperature of the external coagulant promotes the formation of spherical particles across the membrane cross section, which is similar to the result of solid-liquid phase separation in crystalline polymer and solvent mixtures. In the present invention, the lower the temperature of the coagulation solution, the more advantageous it is to change the spherical particle size of the outer and inner surface layer. Therefore, the preferable temperature of the coagulation liquid is 40 degrees C or less, More preferably, it is 5 degrees C or less, Most preferably, it is -40-40 degreeC. If the temperature of the coagulation liquid exceeds 40 ℃, the outer dense layer is formed or the membrane is partially dissolved to form a desirable hollow fiber membrane.

The hollow forming agent includes a non-solvent, a good solvent, and a polymer, and the temperature is maintained at 0 to 40 ° C., preferably at room temperature. The non-solvent may be selected from one or more of the above-mentioned non-solvent crowds, more preferably ethylene glycol. In addition, the preferred good solvent in the hollow forming agent may be selected from one or more of the above-mentioned good solvent groups, more preferably dimethylacetamide. Polymers used in the hollow forming agent include polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, and the like, and these may be used alone or in combination of one or more, and more preferably, polyvinylpyrrolidone. The composition ratio of the hollow forming agent is preferably composed of 10 to 60% by weight of a good solvent, 30 to 80% by weight of a non-solvent, within 10% by weight of a polymer, more preferably a good solvent 30 To 60% by weight, non-solvent 65 to 35% by weight, polymer 5% by weight. If the polymer is not included in the hollow forming agent, it is difficult to continuously manufacture a hollow fiber membrane having a uniform outer diameter. If the content of the solvent exceeds 60% by weight, uniform blow molding is impossible due to the actual dissolution of the membrane. In addition, when the non-solvent content exceeds 65% by weight, a dense layer is formed on the subsurface in the hollow, resulting in the formation of a membrane having a low water permeability.

(Washing process)

In addition, the present invention may further include a washing process to remove the organic matter including the solvent remaining in the membrane of the hollow fiber membrane transferred to the air from the coagulation solution. Water is preferably used as the washing liquid, and the washing time is not particularly limited, but at least one day or more and five days or less is preferable.

Hereinafter, the configuration and operation of the present invention will be described through the following examples. However, the present invention is not limited by the following examples.

EXAMPLE

(Examples 1 to 5)

On the outer surface  Fabrication of Porous Hollow Fiber Membranes with Rod-shaped Particles

To obtain a polymer concentration of 40% by weight to the content as shown in Table 1, polyvinylidene fluoride (Kureha, KF1300) was slowly added to γ-butyrolactone to prepare a uniform spinning solution. In addition, the inorganic additive containing a hydroxyl group (MMT-OH) is previously dispersed in a predetermined amount of γ-butyrolactone to 2 to 8% by weight of the total composition, and then added to the uniformly dissolved polymer solution Mixed. Then, the air bubbles contained in the prepared polymer spinning solution were removed using a vacuum pump, and then the spinning solution was transferred to a double nozzle maintained at 140 ° C. with an inner diameter of 0.6 mm and an outer diameter of 1.4 mm using a gear pump. It was continuously spun into an external coagulation solution. At this time, the solution discharge amount was 3.5 cc / min, and the hollow forming agent was a dimethylacetamide / ethylene glycol / polyvinylpyrrolidone mixture (50 wt% / 45 wt% / 5 wt%) at room temperature. The composition of the external coagulation solution was the same as the hollow forming agent except for the polymer, but the hollow fiber membrane was prepared by changing the temperature as shown in Table 1 below. Subsequently, the hollow fiber membrane passed through the external coagulating solution was continuously transferred to the atmosphere for 30 seconds, immediately wound up through a winding bobbin immersed in water for about 1/2 second, and then washed in a water washing tank to remove more remaining organic solvent. Washed for 96 h. The completely washed hollow fiber membrane was immersed in 50% by weight aqueous solution of glycerin for 24 hours, and dried at room temperature. The membrane area was approximately 21 cm with an effective length of about 21 strands of hollow fiber membrane having an inner diameter of 0.6 mm and an outer diameter of 1.0 mm. A membrane module having 0.2 m ² was prepared.

Using the hollow fiber membranes and modules, pure permeability, particle blocking rate (polystyrene monodisperse particles; diameter 200 nm) and tensile strength were measured by the method described below, and the results are shown in Table 1, and representative film surface photographs are illustrated. 1 and 2 are shown. At this time, Figure 1 is an electron scanning micrograph (1000 times magnification) of the cross-sectional surface of the polyvinylidene fluoride-based porous hollow fiber membrane containing 2% by weight of a hydrophilic inorganic additive according to an embodiment of the present invention, Figure 2 Electron scanning micrograph (1000 times magnification) of the cross-sectional surface of the polyvinylidene fluoride-based porous hollow fiber membrane containing 8% by weight hydrophilic inorganic additive according to an embodiment of the present invention. 1 and 2, the hollow fiber membrane of the present invention has a cross-sectional outer layer without a dense layer, includes a plurality of rod-shaped particles of several tens of micrometers, and includes a structure composed of a plurality of spherical particles having an inner layer of 5 μm or less. It can be seen that.

(1) Measurement of pure permeability

The prepared hollow fiber membrane module was supplied with pure water at room temperature to one side of the module in a dead-end manner under 1.0 atm, and the amount of water permeated was measured, and then converted into unit time, unit membrane area and per unit pressure.

(2) measurement of blocking rate

A 500 ppm aqueous particle solution was prepared by dispersing an aqueous monodisperse polystyrene particle (polyscience, 200 nm size) in pure water at room temperature. Particle aqueous solution was supplied to one side of the prepared module at a pressure of 0.5 kg / cm ² , and the polystyrene concentration dispersed in the permeated aqueous solution and the initially supplied raw water was measured using an ultraviolet spectrometer (Shimadzu, UV-1601PC). . Thereafter, the blocking ratio was determined by converting the relative ratio of the absorption peaks measured at the wavelength of 240 nm into percentage using the following equation.

(Equation 1)

Percentage Blocked (%) = (Stock Concentration-Permeate Concentration) ÷ Stock Concentration x 100

(3) Measurement of tensile breaking strength

Tensile strength was measured by using a tensile tester and a sample having a holding distance of 60 mm was measured five times at a crosshead speed of 50 mm / min.

Example Composition (% by weight) Coagulation liquid temperature (℃) Pure Permeability (l / m ² hr) Polystyrene Particle Blocking Rate (%) Tensile Strength at Break (kgf / piece) Membrane Structure (Surface Layer + Inside) One PVDF / DMAC / MMT-OH 40/58/2 -20 4971 96.0 0.31 Bar + Spherical 2 PVDF / DMAC / MMT-OH 40/58/2 0 5835 97.0 0.35 Bar + Spherical 3 PVDF / DMAC / MMT-OH 40/58/2 20 5775 99.0 0.44 Bar + Spherical 4 PVDF / DMAC / MMT-OH 40/52/8 -20 6021 99.0 0.43 Bar + Spherical 5 PVDF / DMAC / MMT-OH 35/57/8 -20 6240 97.0 0.39 Bar + Spherical

(Comparative Examples 1 to 3)

Fabrication of porous hollow fiber without rod-shaped particles

 A hollow fiber membrane was prepared under the same conditions as in Example 1 except that no hydrophilic inorganic material was added. Then, pure permeability, polyester particle blocking rate and tensile strength at break were measured in the same manner as described above, and the results are shown in Table 2. In addition, electron micrographs of the microstructures of representative film sections of Comparative Examples 1 and 2 are shown in FIGS. 5 and 6.

Comparative example Composition (% by weight) Coagulation liquid temperature (℃) Pure Permeability (l / m ² hr) Polystyrene Particle Rejection (%) Tensile Strength at Break (kgf / piece) Membrane Structure (Surface Layer + Inside) One PVDF / DMAC 40/60 -20 483 96.5 0.49 Dense Layer + Spherical 2 PVDF / DMAC 40/60 0 517 97.0 0.57 Dense Layer + Spherical 3 PVDF / DMAC 40/60 20 345 98.0 0.64 Dense Layer + Spherical

5 and 6 according to the comparative example, it can be seen that including a dense layer in the membrane structure.

Therefore, as observed in the above Examples and Comparative Examples, when the polyvinylidene fluoride-based hollow fiber membrane is prepared, it can be seen that when a hydrophilic inorganic material is added, a hollow fiber membrane having rod-shaped particles and spherical particles is formed. It can be seen that the formation of rod-shaped particles is very preferable in terms of water permeability. From the actual measured results, it can be seen that the embodiment of the present invention has a noticeably improved water permeability without a significant decrease in the blocking rate and the tensile strength compared to the comparison.

As described in detail above, the hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane according to the present invention improves the water permeation performance of the membrane without reducing the rejection rate (also referred to as blocking rate) by using a hydrophilic inorganic material and at the same time It can be seen that the formation of particles simultaneously inhibits a significant decrease in mechanical performance. Therefore, the water treatment membrane of the present invention is suitable for the next generation high efficiency separation process including microfiltration and ultrafiltration.

Claims (10)

A plurality of rod-shaped particles having an average particle diameter of about 5 micrometers (μm) and having a length of 5 micrometers (μm) or more, and Many spherical particles with an average particle diameter of 5 micrometers (µm) or less Hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane comprising a. The hydrophilic polyvinylidene fluoride-based porous hollow fiber of claim 1, wherein the rod-shaped particles have an average particle diameter of 1 to 10 µm, a length of 1 to 100 µm, and an average particle diameter of the spherical particles of 1 to 10 µm. The hydrophilic polyvinylidene fluoride-based porous hollow fiber of claim 1, wherein the hollow fiber membrane has an outer diameter of 0.8 to 1.2 mm and a film thickness of 0.1 to 0.4 mm. The method of claim 1, wherein the hollow fiber membrane is formed by using a hollow forming agent at room temperature while discharging the spinning solution 100 ℃ or more to the external coagulation solution below 40 ℃, the spinning solution is a polyvinylidene fluoride-based polymer A polyvinylidene fluoride-based porous hollow fiber membrane comprising a good solvent and a poor solvent, wherein the external coagulating solution includes a good solvent and a non-solvent, and the hollow former includes a good solvent, a non-solvent, and a polymer. a) preparing a spinning solution containing a polyvinylidene fluoride polymer, a hydrophilic inorganic additive, and a poor solvent, b) The spinning solution is transferred to an outer tube of a double nozzle maintaining a temperature of at least 100 ° C. or higher, and then discharged into an external coagulation liquid containing a good solvent and a non-solvent maintained at 40 ° C. or lower, and the amount of room temperature Manufacturing a hollow fiber membrane by transferring a hollow forming agent including a solvent, a non-solvent, and a polymer into the inside of the double nozzle; Method for producing a hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane comprising a. The method of claim 5, wherein the temperature of the double nozzle is maintained at a temperature of 120 to 180 ℃, the temperature of the external coagulation liquid is maintained at -40 to 40 ℃ of the hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane Manufacturing method. The method of claim 5, wherein the method further comprises the step of washing the hollow fiber membrane with water. The method of claim 5, wherein the spinning solution comprises 25 to 55% by weight of polyvinylidene fluoride-based polymer, 1 to 20% by weight of hydrophilic inorganic additives and 25 to 74% by weight of the solvent, the external coagulation solution is a good solvent 10 to 60 wt% and non-solvent 40 to 90 wt%, wherein the hollow former comprises 10 to 60 wt% good solvent, 30 to 80 wt% non solvent, and polymer within 10 wt% Method for producing a hydrophilic polyvinylidene fluoride-based porous hollow membrane. The silane-based monomer according to claim 5, wherein the hydrophilic inorganic additive is a protonated montmorillonite and a hydrophilic group containing a hydrophilic group selected from the group consisting of an epoxy group, a hydroxyl group, a carboxyl group, a sulfonic acid group, an amine group, a thiol group, and a chloride group. A method for producing a hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane, wherein at least one of montmorillonite-based inorganic additive compounds obtained by condensation reaction with is selected. The method of claim 5, wherein the polyvinylidene-based polymer is selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichlorofluoroethylene, and mixtures thereof. The solvent used in the spinning solution is γ-butyrolactone, cyclonucleanone, 3-hexanone, 3-heptanone, 3-octanone, N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, dimethylform Selected from the group consisting of amides and mixtures thereof, The good solvent included in the hollow forming agent and the external coagulant is selected from the group consisting of γ-butyrolactone, cyclonucleanone, 3-hexanone, 3-heptanone, 3-octanone, and mixtures thereof. The non-solvent is selected from the group consisting of glycerol, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, and mixtures thereof, The polymer used in the hollow forming agent is polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone and a method of producing a hydrophilic polyvinylidene fluoride-based porous hollow fiber membrane is selected from the group consisting of.

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