KR20130040625A - Polyvinylidenefluoride hollow fiber membrane with secondary barrier for water treatment and preparation thereof - Google Patents

Abstract

The present invention relates to a hollow fiber membrane for water treatment comprising a hollow fiber support layer 40, a secondary blocking layer 30, an active support layer 20, and a separation active layer 10 sequentially from the inside of the hollow fiber separator. Of the hollow fiber membrane having the secondary blocking layer 30 by preparing the spinning solution and molding the spinning solution into a hollow fiber membrane through double-detention, and then dissolving the surface of the hollow fiber membrane in a re-dissolution tank. It relates to a manufacturing method.

Description

Polyvinylidene fluoride hollow fiber membrane with secondary barrier for water treatment and preparation according to the present invention

The present invention is a polyvinylidene fluoride hollow fiber separator for water treatment having a secondary blocking layer (30),

The separation membrane is an external pressure hollow fiber membrane having a separation active layer 10 on the outside, and an active support layer 20 and a hollow fiber support layer 40 supporting the hollow fiber support layer 40 and the separation active layer 10 having large pores therein. And a secondary blocking layer 30 between the active support layer 20 and a hollow fiber membrane for water treatment, and a method of manufacturing the same.

Polysulfone (Polysulfone; PSf), Polyethersulfone (PES), Polyvinylidenefluoride (PVDF), Polyethylene, Polypropylene (Polypropylene; PP), Polytetrafluoroethylene (PTFE), Polycarbonate (PC), Polyamide (PA), Polyester, Polyvinylchloride (PVC), Cellulose Nitride Cellulose nitrate, Regenerated Cellulose, Celluloseacetate (CA), Cellulosetriacetate (CTA), Polyacrylonitrile (PAN) and the like are used. Polysulfone (PSf), polyethersulfone (PES), and polyvinylidene fluoride (PVDF) are hydrophobic materials, and generally, ultrafiltration membranes or microfiltration hollow fiber membranes are prepared using a phase transfer method. Polysulfone or polyisulfone have a much higher phase transition speed and lower viscosity than polyvinylidene fluoride, so that a large amount of hollow fiber membranes can be produced in a short time, but the mechanical strength is weak, so that the membrane surface is easily damaged or cut, Due to chemistry, the membrane deteriorates rapidly during long-term use, and there is a problem of long-term use due to membrane contamination due to the relatively large pore size of the membrane. Although the permeation rate is large, the fouling phenomenon of the membrane is severe and there is a problem of causing the passage of fine organic materials. Polyethylene or polypropylene is a typical crystalline polymer, and mainly melts the polymer and extrudes it, and then stretches the amorphous region existing between the crystal and the crystal to form voids, thereby having a very high porosity. Therefore, the hollow fiber membrane produced by this method has a high permeation flux, but the pores are slit-shaped, have a relatively large pore and pore distribution, it is difficult to control the membrane contamination, and the separation performance is limited, so sewage treatment There is a problem that is used extremely limited. Polycarbonate or polyester material is manufactured as a separation membrane using the track etching method due to the characteristics of the material, but this method has the advantage of producing a uniform void, but is extremely limited in the microfiltration membrane with a very small porosity, a large void, Large scale membrane production has a difficult problem. Polymers such as cellulosenitrate, Regenerated Cellulose, Celluloseacetate (CA), Cellulosetriacetate (CTA), Polyacrylonitrile (Polyacrylonitrile; PAN) As a separator, a separation membrane is manufactured by using a solvent induction phase transition method, and has a high permeation flux, but has a weak chemical resistance and durability, and has a problem of long-term use due to breakage or damage when forming into a hollow fiber membrane.

Korean Patent Publication No. 2005-18624 discloses the preparation and application of a porous membrane having both a three-dimensional mesh structure and a spherical structure. In this patent, in order to achieve the porous membrane, the thermoplastic resin is dissolved in a solvent, and the resin solution is solidified by ejecting the resin solution from the spinning nozzle into the cooling liquid to change the composition of the cooling liquid on one side and the other side of the membrane. A method having both a three-dimensional mesh structure and a spherical structure, a method of forming a three-dimensional mesh structure by applying a resin solution to at least one side of the porous membrane having a spherical structure, and then immersing in a coagulating solution, and a resin for forming a three-dimensional mesh structure A method having both a three-dimensional mesh structure and a spherical structure in which a solution and a resin solution for forming a spherical structure are simultaneously discharged from a triple spinning nozzle and then solidified. However, such a hollow fiber membrane manufacturing method is too complicated to increase the manufacturing cost, and also may cause problems such as peeling due to the interfacial adhesion failure in the heterogeneous process and manufacturing process between each layer. Bulte et al., Published in 1996, published by A.M.W. Bulte, M.H.V. Mulder, C. A. Smolders, H. Strathmann, Diffusion induced separation with crystallizable nylons. II. (Relation to final membrane morphology, Journal of membrane science, 121, 51-58 (1996)], when preparing a membrane using a thermoplastic resin, the membrane having a spherical structure by dissolving at high temperature and immersing in a low temperature coagulation bath The production is started. Lee et al., Published in 1994, S.-G. Li, G.H. Koops, M.H.V. Mulder, T. van den Boomgaard, C.A. Smolders, Wet spinning of integrally skinned hollow fiber membranes by a modified dual-bath coagulation method using a triple orifice spinneret, Journal of membrane science, 94, 329-340 (1994), albretz et al. W. Albrecht, K. Kneifel, Th. Weigel, R. Hilke, R. Just, M. Schossig, K. Ebert, A. Lendlein, Preparation of highly asymmetric hollow fiber membranes from poly (ether imide) by a modified dry-wet phase inversion techniquie using a triple spinneret, Journal of membrane science, 262, 69-80 (2005)] discloses the production of hollow fiber membranes for pervaporation using triple spinning nozzles. Korean Patent Publication No. 2007-102012 discloses a hydrophilic polyvinylidene fluoride resin porous hollow comprising a plurality of rod-shaped particles having an average particle diameter of about 5 microns, a length of 5 microns or more, and a plurality of spherical particles having an average particle diameter of 5 microns or less. Started manufacturing of the desert. In Korean Patent Laid-Open Publication No. 2007-113374, a plurality of polymer nanofibers, which are located inside the separation membrane from the hollow center of the hollow fiber membrane to the outside, are exposed on the cross-section of the membrane and have an average particle diameter of 1 to 5 microns or less. An inner layer comprising a plurality of microspherical particles, a plurality of polymer nanofibers located on top of the inner layer and having an average diameter of 500 nanometers or less are exposed to the cross-section, and at the same time, a plurality of intermediates having an average particle diameter of more than 5 microns and 10 microns An intermediate layer comprising spherical particles, and a plurality of polymer nanofibers, which are located on top of the intermediate layer and have an average diameter of 500 nanometers or less, are exposed on the cross-section, and at the same time, include a plurality of microspherical particles having an average particle diameter of 1 to 5 microns or less. Production of polyvinylidene fluoride porous hollow fiber membrane comprising surface layer And. In addition, Korean Patent Publication No. 2007-113375 discloses the production of a polyvinylidene fluoride resin porous hollow fiber membrane having four layers having different particle diameters from a hollow central part of a hollow fiber membrane. Disclosed is a production of a polyvinylidene fluoride resin porous hollow fiber membrane comprising an inner layer comprising a plurality of spherical particles outward from a central portion of the hollow fiber membrane and a surface layer comprising a plurality of spherical fibrous particles. However, this method has a drawback of limiting water permeation because it is difficult to form large voids due to the small voids between the particles due to the spherical structure of the support layer forming the thick layer inside. In addition, since there is no separation active layer 10 on the surface of the porous membrane, it has a drawback that the removal efficiency of microparticles, pathogenic bacteria, microorganisms, etc. is not high. Korean Patent Laid-Open Publication No. 2005-0056245 discloses the formation of hydrophilic vinyl monomers by irradiating polyvinylidene fluoride microporous membranes with ionizing radiation, followed by graft polymerization of these radicals on the membrane surface. It is starting to form. In addition, Korean Patent Publication No. 2006-0003347 discloses a porous 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. The film is starting. 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 a hydrophilized polyvinylidene fluoride resin porous membrane through chemical treatment with alkali and oxidizing agent 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 particularly, chemical treatment methods often have the disadvantage of impairing the mechanical strength inherent in polyvinylidene fluoride resin.

[Reference 1] KR 10-2005-018624 [Document 2] KR 10-2007-102012 [Reference 3] KR 10-2007-113374 [Document 4] KR 10-2007-113375 [Reference 5] KR 10-2007-103187 [Document 6] KR 10-2005-056245 [Document 7] KR 10-2006-003347 8 KR 10-2005-078747

[Reference 1] A.M.W. Bulte, M.H.V. Mulder, C. A. Smolder, H. Strathmann, Journal of Membrane Science, 1996, Vol 121, 51-58 [2] S.-G. Li, G.H. Koops, M.H.V. Mulder, T. van den Boomgaard, C.A. Smolders, Journal of Membrane Science, 1994, Vol 94, pp. 329-240 [3] W. Albrecht, K. Kneifel, Th. Weigel, R. Hilke, R. Just, M. Schossig, K. Ebert, A. Lendlein, Journal of membrane science, 2005, Vol 262, pp. 69-80

In order to solve the above problems, the present inventors add one or more selected from inorganic additives, organic additives, and solvent additives to a polymer resin, and then dissolve it in a solvent to dissolve the solvent in a non-solvent induced phase separation method (NIPS). ) Or hollow fiber membranes through diffusion induced phase separation (DIPS), or melted to prepare spinning solutions, and then hollow fiber membranes through thermally induced phase separation (TIPS). After preparing, drying, and then immersed in a solvent such as normal methylpyrrolidone, dimethylformamide, dimethylsulfuroxide, dimethylacetamide, etc., and then immersed in a non-solvent such as water to dissolve and phase-separate the surface rearrangement and The present invention has been completed by having the inner secondary blocking layer 30.

In the hollow fiber membrane for water treatment having a secondary blocking layer 30,

Separation membrane consists of hollow fiber support layer 40, secondary blocking layer 30, active support layer 20, separation active layer 10 sequentially from the inside, the separation active layer 10 has a thickness of about 0.1 to 3㎛ The size of is made of 0.001 to 0.1㎛. However, when applied to water treatment has a secondary blocking layer 30 having a pore size of 0.1 to 3㎛ to prevent serious contamination damage when the separation active layer 10 is damaged by harsh operating conditions and environment.

Separation membrane is a step of making a spinning solution by mixing a polymer and an additive and then dissolving or melting with a solvent, spinning the spinning solution to an external coagulation tank with an internal coagulant through a double detention, drying the hollow fiber membrane solidified in the external coagulation bath The step of immersing the dried hollow fiber membrane in a re-dissolution tank to which a solvent and various additives are added, and the re-dissolution step of dissolving the surface, and finally the re-dissolution coagulation tank.

In particular, the present invention is to add a hydrophilic polymer for improving the permeation flow rate or to promote pore formation to various polymer resins that can be formed into a hollow fiber membrane by the solvent induction phase separation method or thermal induction phase separation method in the first hollow fiber membrane manufacturing step Or by adding a nucleating agent to promote the liquid phase-solid phase phase transition of the polymer, improve the formability, and solvent-based additives for controlling pore formation, etc., to prepare a spinning solution After manufacturing a spinning solution by melting and spinning through a double-deposit, dried and then re-dissolution process to produce a hollow fiber membrane having a secondary blocking layer 30 to be able to be used stably in the field of water treatment.

Hereinafter, the present invention will be described in detail.

1) Preparation of spinning solution by solvent

Hollow fiber membranes using polymer resins can be manufactured using non-solvent phase separation method, thermally phase separation method, stretching method, sintering method, track etching method ( Track-etching method). Solvent-induced phase separation and heat-induced phase separation are effective in the present invention. The solvent induction phase separation method is to degas the polymer resin in a solvent to prepare a spinning solution, and to remove bubbles remaining in the solution by decompression or the like. The degassed spinning solution is filtered to remove impurities, particularly solid impurities, in the liquid. After filtering, it is sent to the spinning nozzle for molding into hollow fiber. Since a constant discharge amount is very important, a metering pump or nitrogen pressure is used. Spinning nozzles generally consist of concentric double nozzles with an internal coagulant in the center. The internal coagulant is mainly a non-solvent, but a mixed solvent in which a poor solvent and a solvent are mixed may be used, if necessary. Instead of internal coagulants, some gases such as nitrogen and air are blown. The hollow fiber-type polymer resin discharged together with the internal coagulant is introduced into the external coagulation bath while the nonsolvent in the external coagulation bath penetrates into the polymer resin solution molded into the hollow fiber, resulting in separation of the polymer and the solvent. Hollow yarn is completed. Immediately before the polymer and the solvent become unstable, the polymer liquid phase and the solvent phase separation, that is, liquid-liquid demixing occurs, whereby the solvent is replaced by a non-solvent and exists as pores of the separator. Usually, the polymer resin is used alone or in combination. Particularly, in order to impart hydrophilicity, a blend of a hydrophilic polymer, polyethyleneglycol, polyvinylpyrrolidone, polyethyleneoxide, dextran, polymethylmethacrylate, or lithium chloride Zinc chloride, magnesium sulfate and magnesium chloride may also be added. The external coagulant uses a total nonsolvent, preferably water. The spinning solution is usually prepared at room temperature and spun because the polymer is dissolved in a solvent, but is generally performed at about 20 ° C to 80 ° C. If the spinning temperature is less than 20 ℃, the pore size is small and the porosity is reduced to reduce the permeation flux. On the other hand, the rejection rate increases and the mechanical strength tends to increase. In the spinning conditions exceeding 80 ℃, compared with the spinning conditions of less than 20 ℃, the pore size increases and the porosity increases, the permeation flux increases, but the exclusion rate tends to decrease and the mechanical strength tends to decrease. Since the temperature of the internal coagulant passes through the elongated stainless steel tube, it is almost dependent on the temperature of the spinning solution. Therefore, if the temperature difference between the spinning solution and the spinning solution is not large, there is almost no difference in the temperature. The temperature of the external coagulation bath also affects the performance and properties of the hollow fiber membranes. In addition, the composition of the internal coagulant, the composition of the external coagulant also greatly influences the size of the pores, the porosity, the mechanical strength. The weight average molecular weight of the polymer resin is also very important. If the molecular weight is high, the viscosity is high, it is difficult to spin, the pore size is small, the porosity is also reduced to decrease the permeation flux, but the mechanical strength increases. When the hollow fiber membrane is prepared by the solvent induction phase separation method, the polymer is usually in the range of 10 to 30% by weight. If less than 10% by weight, the mechanical strength is small and easily judged, and the voids are so large that it is difficult to achieve the purpose of separation. If it exceeds 30% by weight, the viscosity is too high to be difficult to spin, the pore is small and the porosity is small, the permeation flow rate is too small to produce a module and applied to the water treatment process is difficult to secure economic feasibility. For example, when preparing a hollow fiber membrane using a solvent-induced phase separation method with polyvinylidene fluoride resin, 10 to 25% by weight of polyvinylidene fluoride resin is added, and an inorganic additive and an organic additive are added, and then the temperature is 20 ° C. to 100 ° C. It was dissolved in a solvent to prepare a spinning solution. The polyvinylidene fluoride resin has a weight average molecular weight of 200,000 Daltons to 700,000 Daltons in accordance with the object of the present invention. If the weight average molecular weight of the polyvinylidene fluoride resin is less than 200,000 Daltons, the permeation flux is high when molded into the hollow fiber membrane, but the mechanical strength is small, so it is easily broken or damaged when applied to the water treatment process. When the polyvinylidene fluoride resin has a weight average molecular weight of more than 700,000 Daltons, the viscosity is very high, so it is difficult to spin and there is a problem of decreasing the permeation flux with small pores.

2) Preparation of Spinning Solution by Melting

Thermally induced phase separation is generally performed by quenching a mixture of a polymer-plasticizer two-component system below the phase separation temperature at an appropriate cooling rate using a polymer material without a proper solvent at room temperature to prevent phase separation between the continuous phase and the dispersed phase. A process of manufacturing a separator by imparting porosity to the entire matrix after the formation of the polymer, and in general, a polymer and a plasticizer are made through melt blending to form a homogeneous solution, molded into hollow fibers, and then cooled to induce phase separation. And solidify the polymer. The plasticizer is then removed to produce a microporous structure. Polymers for preparing the hollow fiber membranes by thermally induced phase separation are polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, and the like. The spinning solution is prepared by adding a pore-forming agent such as lithium chloride, zinc chloride, magnesium sulfate, magnesium chloride, magnesium chloride, silica, poor solvent or plasticizer, and a hydrophilic polymer for hydrophilicity to the polymer resin. Unlike the solvent-induced phase separation method, polymer resins generally use relatively high concentrations, and thus have high mechanical strength after molding into hollow fiber membranes. For example, forming the hollow fiber membrane by the thermal induction phase separation method using polyvinylidene fluoride resin is a temperature of 110 ℃ to 200 ℃ by mixing a solvent with a polymer resin for the purpose of strengthening the flexibility of the inorganic additive, organic additive, plasticizer, etc. Melt at to prepare a spinning solution. More specifically, the polyvinylidene fluoride resin 20 to 60% by weight of the weight average molecular weight of 200,000 Daltons to 700,000 Daltons composed of a single or a mixture of two or more, when used alone to use a polymer of 250,000 Daltons to 700,000 Daltons In the case of using a mixture of two or more kinds, a low molecular weight polyvinylidene fluoride resin of 200,000 Daltons to 400,000 Daltons and a high molecular weight polyvinylidene fluoride resin of 400,000 Daltons to 700,000 Daltons is preferably used. If the polymer is less than 20% by weight, the mechanical strength is weak, so it is easily cut when used for water treatment by forming into a hollow fiber membrane, and inconvenient in use.In the case of more than 60% by weight, the molding is difficult due to the high viscosity and the void is small. Low permeation flow rate makes it unsuitable for use as a hollow fiber membrane for water treatment. When the weight average molecular weight of the polymer is less than 200,000 Daltons, the mechanical strength is weak, which is not suitable for use as a hollow fiber membrane for water treatment. When the weight average molecular weight is 700,000 Daltons or more, the viscosity is high, so it is difficult to radiate, or the voids formed are small. It is not suitable for use as a hollow fiber membrane for the desired water treatment. Because polyvinylidene fluoride resin is hydrophobic, it has a weak affinity with water, so that the phase transition speed is increased and inorganic additives are used to control them. These inorganic additives play an important role in forming voids in the polyvinylidene fluoride resin hollow fiber membrane. . 1-20% by weight of one or more inorganic additives selected from lithium chloride (LiCl), zinc chloride (ZnCl ₂ ), magnesium chloride (MgCl ₂ ), magnesium sulfate (MgSO ₄ ) is used. If the inorganic additive is less than 1% by weight, the effect of addition is insignificant, and the pore formation is poor. If the inorganic additive is more than 20% by weight, the presence and dispersibility of insoluble additives are deteriorated. There is a problem. Organic additives are hydrophilic polymers or materials such as polyethylene glycol (PEG), dextran (Dextrane), polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene oxide (PEO), Polyvinylacetate (PVAc), maleic acid (maleic acid) at least one selected from 1 to 20% by weight is mixed. If the hydrophilic organic additive is less than 1% by weight, the effect of exhibiting hydrophilicity is insignificant, which shows a low permeation flux when forming into a hollow fiber membrane, and when the hydrophilic organic additive is more than 20% by weight, it shows a high permeation flux. There is a problem in long-term use due to chemical resistance. Solvents include dimethylformamide (N, N-Dimethylformamide; DMF), dimethylacetamide (N, N-Dimethylacetamide; DMAc), normal methylpyrrolidone (N-Methyl-2-pyrrolidone; NMP), and dimethylsulfoxide 1 to 10% by weight of any one or more in DMSO), the effect of the addition of the solvent is not very effective when the good solvent is less than 1% by weight, the excess dissolution of the polymer resin by solvent Due to the hollow fiber membrane after molding, the size of the pores is large, there is a disadvantage that the physical properties are lowered. 3 to 50% by weight of plasticizer is added to gamma butyrolactone (γ-Butyrolactone), cyclohexanone (Cyclohexanone), isophorone (Isophorone), dibutylphthalate (DBP), diethylhexylphthalate (Di-2) -ethylhexylphthaltate (DOP). One or more mixed solvents selected from these plasticizers are used, which facilitates molding in forming the hollow fiber membranes and plays a very important role in forming voids. If the plasticizer is less than 3% by weight, it is difficult to obtain the effect, and if it is 60% by weight or more, it can have a large porosity and porosity. Not.

3) Preparation of Hollow Fiber Membrane

The spinning solution prepared in step 1) and 2) is flowed into the outer tube of the double detention, and the inner coagulant flows into the central tube of the double detention, and is spun into an external coagulation bath to solidify the spinning solution to prepare a hollow fiber membrane. The hollow fiber membrane is wound up after the solvent and organic additives remaining in the washing tank are removed. The temperature of the double detention is in the range of 20 ° C to 100 ° C and preferably 30 ° C to 80 ° C in the case of the solvent induction phase separation method. In the case of thermally induced phase separation, various temperature ranges are applied because they depend on the melting temperature or the crystallization temperature of the polymer resin. In the solvent-induced phase separation method, when the temperature of the double-detention is less than 20 ° C., the spinning solution has a high viscosity, which makes it difficult to spin. The hollow fiber membranes cannot be continuously formed because they are cut. The washing tank is configured to control the increase of the extracted solvent by continuously exchanging a predetermined amount because water is used alone and the extracted solvent increases during long-term use.

4) Re-melting process

The hollow fiber separator prepared in step 3) is rearranged through a surface remelting process. Surface dissolution is basically done in the surface dissolution tank. The surface dissolution tank contains solvents such as dimethylformamide, dimethylacetamide, normal methylpyrrolidone and dimethyl sulfoxide, such as lithium chloride, zinc chloride, magnesium sulfate and magnesium chloride. Hydrophilic substances such as inorganic additives, polyethylene glycol, dextran, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, polyvinylacetate and the like are added. The hollow fiber membrane prepared in step 3) is first dried to remove water remaining on the surface, and then immersed in a re-dissolution tank to allow re-dissolution process on the surface. If soaked for too long, re-dissolution may be too deep and liquid polymer may flow, so be careful. If re-dissolution occurs, soak it in the coagulation bath to cause the phase separation and the hollow fiber membrane to solidify.

5) washing process

When re-dissolution and coagulation occurs to produce a hollow fiber membrane having the final secondary blocking layer 30 may further include a washing process to remove the organic matter including the solvent remaining in and out of the hollow fiber membrane. The use of water as the washing liquid is preferred, and the washing time is not particularly limited, but at least 4 hours or more and 2 days or less.

As described in detail above, when the hollow fiber separator having the secondary blocking layer 30 manufactured according to the present invention is manufactured as a module and applied to water treatment, the secondary jersey is used even under severe conditions, even if the separation active layer 10 is destroyed and damaged. Since the layer 30 can prevent water contamination, it can be used in a water treatment membrane filtration process, especially a membrane filtration process for water purification.

1 is a schematic diagram schematically showing a cross section of a hollow fiber membrane composed of a hollow fiber support layer 40, a secondary blocking layer 30, an active support layer 20, and a separation active layer 10 sequentially from the inside of the hollow fiber membrane.
2 is a scanning electron micrograph of the cross section of the hollow fiber membrane in which the secondary blocking layer 30 is present.
Figure 3 is a scanning electron micrograph of the secondary blocking layer 30 of the separator prepared by the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example

Example 1

8 wt% of lithium chloride, an inorganic additive for forming pores in 42 wt% of polyvinylidene fluoride resin having a weight average molecular weight of 573,000 Daltons, 3 wt% of hydrophilic polymer polyethylene glycol, 5 wt% of polyvinylpyrrolidone, and diethylene 2 wt% of glycol, 5 wt% of normal methylpyrrolidone, and 35 wt% of gamma butyrolactone were mixed and stirred at 150 to prepare a spinning solution. The prepared spinning solution was maintained at 150 to remove bubbles present in the solution by using a pressure reduction device. The internal coagulant was prepared at room temperature with a ratio of water to normal methylpyrrolidone 6 to 4, and then degassed using a decompression device and maintained at 25 ° C. during spinning. The external coagulant used pure water and cooled using a chiller to be 1 ℃ to 2 ℃. The spinning solution is transferred to the outer tube of the double-detention holding the 150 ℃ by a pulse-free metering gear pump, and the internal coagulant is also transferred to the center tube of the double-detention using a fixed-quantity gear pump and spun into an external coagulation tank. The spun polymer solution solidified as the phase transition occurred as it flowed into the external coagulant, was formed into a hollow fiber membrane, and the molded hollow fiber membrane was wound up through a washing tank. The hollow fiber membrane wound up was immersed in a re-dissolution tank after drying by hot air. The redissolver was added to the normal methylpyrrolidone 9% by weight of lithium chloride, 5% by weight of polyethylene glycol and maintained at 30 ℃. The hollow fiber membrane removed from the remelting tank was immersed in a coagulation bath containing water to resolidify the redissolved polymer resin to complete the hollow fiber membrane having the secondary blocking layer 30. Finally, the prepared hollow fiber membrane was immersed in pure water for 4 hours to remove the remaining solvent. After dipping out the immersed hollow fiber membrane and drying, an experimental mini module was manufactured to measure pure permeability and rejection rate, and the same value was measured after surface damage. In addition, the breaking strength of the hollow fiber membrane was measured using a universal testing machine.

[Example 2]

To 15% by weight of polyvinylidene fluoride resin having a weight average molecular weight of 573,000 Daltons, 5% by weight of lithium chloride, an inorganic additive for forming pores, 2% by weight of hydrophilic polymer polyethylene glycol and 2% by weight of polyvinylpyrrolidone were added. After dissolving in 80 ℃ dimethylformamide to prepare a spinning solution. The prepared spinning solution was used to remove the air bubbles in the solution by using a pressure reduction device while maintaining the 80 ℃. The internal coagulant was prepared at room temperature with a ratio of water to dimethylformamide of 7 to 3, and then degassed using a decompression device and maintained at 25 ° C. during spinning. The external coagulant used pure water and maintained at 30 ° C. The spinning solution was transferred to the outer tube of the double-detention holding the 80 ° C by a pulse-free metering gear pump, and the internal coagulant was also transferred to the central tube of the double-detention using a fixed-quantity gear pump and spun into an external coagulation tank. The spun polymer solution solidified as the phase transition occurred as it flowed into the external coagulant, was formed into a hollow fiber membrane, and the molded hollow fiber membrane was wound up through a washing tank. The hollow fiber membrane wound up was immersed in a re-dissolution tank after drying by hot air. The redissolver was added to the normal methylpyrrolidone 9% by weight of lithium chloride, 5% by weight of polyethylene glycol and maintained at 30 ℃. The hollow fiber membrane removed from the remelting tank was immersed in a coagulation bath containing water to resolidify the redissolved polymer resin to complete the hollow fiber membrane having the secondary blocking layer 30. Finally, the prepared hollow fiber membrane was immersed in pure water for 4 hours to remove the remaining solvent. After dipping out the immersed hollow fiber membrane and drying, an experimental mini module was manufactured to measure pure permeability and rejection rate, and the same value was measured after surface damage. In addition, the breaking strength of the hollow fiber membrane was measured using a universal testing machine.

Comparative Example 1

In Example 1, a hollow fiber membrane was manufactured in the same manner as in Example 1, by omitting a re-dissolution tank process.

Comparative Example 2

In Example 2, a hollow fiber membrane was manufactured in the same manner as in Example 2, except that the re-dissolution tank process, which is a post-process, was omitted.

[Experimental Example 1]

The hollow fiber membranes prepared in Examples and Comparative Examples were prepared as modules to measure pure permeability, rejection rate (polystyrene monodisperse particles; diameter of 100 nanometers), and tensile strength by the following method.

Measurement of pure permeability;

50 hollow fiber membranes were inserted into a 30 cm polycarbonate transparent tube, and both ends were potted using a polyurethane or epoxy adhesive to prepare an experimental minimodule having an effective membrane area of 0.0651 m 2. 20 ° C. pure water was supplied to one side of the module in a cross flow method under 50 kPa to measure the amount of permeated water, and then converted into unit time and per unit membrane area.

Measurement of exclusion rate;

A 500 nanometer aqueous solution was prepared by dispersing an aqueous solution of monodisperse polystyrene particles having a size of 100 nanometers in pure water at 20 ° C. Two hollow fiber membranes were inserted into a 20 cm transparent tube, and both sides were potted to prepare a mini-module for measuring exclusion rate. Particle aqueous solution was supplied to one side of the prepared module at a pressure of 50 kPa to measure the permeated aqueous solution and polystyrene concentration dispersed in the initially supplied raw water using an ultraviolet spectrometer (Shimadzu, UV-1601PC).

Then, the exclusion rate was determined by converting the relative ratio of the absorption peak measured at a wavelength of 240 nanometers into a percentage using the following equation.

Exclusion rate (percent) = (feed water concentration-permeate concentration) ÷ feed water concentration X 100

Measurement of tensile strength elongation;

Tensile strength and elongation were averaged by measuring a crosshead speed 5 times at a rate of 50 millimeters per minute using a tensile tester.

The results of each transmission experiment are shown in Table 1.

Pure Permeate Flux
(L / ㎡-hr) at 20 ℃, 50kPa % Rejection
at 20 ℃, 50kPa Breaking Strength (N) Example 1 Before damage 312 99.1 6.5 After damage 789 68.7 Example 2 Before damage 320 99.8 4.2 After damage 812 71.0 Comparative Example 1 Before damage 421 88.7 6.6 After damage 956 5.6 Comparative Example 2 Before damage 387 89.5 4.5 After damage 1002 3.2

As shown in Table 1, in the case of Examples 1 to 2 according to the present invention, the breaking strength slightly decreased compared with the comparative example but did not show a big difference, and the pure permeate flux was 387 to 421 L / m 2 -hr. At 312 to 320 L / m 2 -hr. However, the exclusion rate rose from 88.7 to 89.5 to 99.1 to 99.8. In addition, in the case of Example, after the surface is damaged, the rejection rate is 68% or more, while in the Comparative Example, it can be seen that the reduction is significantly less than 5%.

When the hollow fiber membrane for water treatment having the secondary blocking layer 30 is manufactured as a module, and used in water purification, sewage treatment, sewage reuse, seawater desalination pretreatment, etc., the membrane has a high stability through the secondary blocking layer 30, thereby severely separating the membrane under harsh conditions. Even if this breakage or damage occurs, it can prevent the hydration contamination that can occur immediately, so it can be used as a hollow fiber membrane for the next-generation high efficiency water treatment with stability.

(10) Separation active layer (20) Active support layer
(30) Secondary Jersey Floor (40) Hollow Fiber Support Floor

Claims (8)

In the polyvinylidene fluoride hollow fiber separator for water treatment having a secondary blocking layer (30),
Polyvinylidene fluoride having a secondary blocking layer 30, characterized in that the inner rotor of the hollow fiber membrane is sequentially composed of a hollow fiber support layer 40, a secondary blocking layer 30, an active support layer 20, a separation active layer 10 Liden hollow fiber separator. The method of claim 1,
Polyvinylidene fluoride-based hollow fiber membrane having a secondary blocking layer 30, characterized in that the hollow fiber support layer 40 has an average pore size of 5 to 20㎛ with a thickness of 100 to 300㎛. The method of claim 1,
The secondary blocking layer 30 has a sponge-like structure with a thickness of 1 to 10 μm, and has an average pore size of 0.1 to 3 μm, and polyvinylidene fluoride-based hollow fiber having a secondary blocking layer 30. Separator. The method of claim 1,
The active support layer 20 is a polyvinylidene fluoride-based hollow fiber having a secondary blocking layer 30, wherein the active support layer 20 has a thickness of 5 to 50 μm, and has a cylindrical multi-tubular structure, and has a diameter of 5 to 30 μm. Separator. The method of claim 1,
Separation active layer 10 is a polyvinylidene fluoride-based hollow fiber membrane having a secondary blocking layer 30, characterized in that the average pore size of 0.001 to 0.1 with a thickness of 0.1 to 3㎛. One or more additives selected from lithium chloride, magnesium chloride, zinc chloride and magnesium sulfate in the polyvinylidene fluoride resin, and one selected from polyethylene glycol, dextran, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, and polyvinylacetate After adding the above additives, the solution was dissolved in a solvent selected from dimethylformamide, dimethylacetamide, normal methylpyrrolidone, and dimethylsulfuroxide to prepare a spinning solution. A method of manufacturing a polyvinylidene fluoride-based hollow fiber separator having a secondary blocking layer (30), wherein the water is removed from the hollow fiber membrane and then immersed in a re-dissolution tank to redissolve the surface. One or more additives selected from lithium chloride, magnesium chloride, zinc chloride and magnesium sulfate in the polyvinylidene fluoride resin, and one selected from polyethylene glycol, dextran, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, and polyvinylacetate The above additives and at least one solvent selected from dimethylformamide, dimethylacetamide, normal methylpyrrolidone and dimethylsulfuroxide and gamma butyrolactone, cyclohexanone, isophorone, dibutylphthalate and diethylhexylphthalate. The mixture of one or more plasticizers is melted to prepare a spinning solution, which is then spun through a double detention to prepare a hollow fiber membrane. Secondary blocking layer 30, characterized in that for resolidification by Method for producing a polyvinylidene fluoride-based hollow fiber membrane having a). The method according to any one of claims 6 to 7,
The remelting bath is one or more solvents selected from dimethylformamide, dimethylacetamide, normal methylpyrrolidone and dimethylsulfuroxide, and at least one additive selected from lithium chloride, magnesium chloride, zinc chloride, magnesium sulfate, polyethylene glycol and dextran. And polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, polyvinylacetate, and a method for producing a polyvinylidene fluoride-based hollow fiber separator having a secondary blocking layer (30), wherein the additive is added.

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