KR101432579B1 - Multilayer PTFE hollow fibertype membrane for membrane distillation and manufacturing method thereof - Google Patents

Abstract

The multi-layered PTFE hollow membrane separator membrane produced by the production method of the present invention has excellent filtering ability and can be widely used in fields such as desalination apparatuses and the filtration ability of the multi-layered PTFE hollow membrane membrane is remarkably improved, .
In addition, since the problem of foreign substances being trapped in the pores in the filtration step is reduced, the filtration ability is remarkably improved, and filtration at a high flow rate becomes possible, and backwashing becomes very simple.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-layer PTFE hollow membrane separation membrane having different interlayer stretching ratios,

The present invention relates to a process for producing a multi-layer PTFE hollow membrane distillation separation membrane having different interlayer stretching ratios, and more particularly, to a process for producing a multi-layer PTFE hollow membrane separation membrane which has a different interlayer stretching ratio capable of remarkably improving filtration ability and backwashing efficiency And to provide a method for producing a multilayer PTFE hollow membrane separation membrane.

Membrane Distillation is a process in which a phase change occurs on the surface of a hydrophobic polymer membrane and condensation and separation are performed by passing the vapor through the micropores on the surface of the membrane. The membrane is separated and removed Process or an organic material having high volatility in an aqueous solution. For example, membrane distillation can be applied to separate ethanol from aqueous ethanol solutions such as bioethanol.

Membrane distillation membrane (MD) is advantageous to use hydrophobic polymer as a material of membrane, unlike reverse osmosis process, which is widely used at present, and MF membrane having a pore size of about 0.5 μm and a thickness of about 100 μm can be applied. Membrane distillation utilizes a hydrophobic polymer membrane. The membrane or membrane (hydrophilic material) has a surface tension greater than that of the membrane, so that it can not pass through the membrane pore in the liquid state and is repelled on the surface of the membrane. At the pore inlet, the substance to be separated is phase-converted into a vapor phase, diffused and permeated into pores, and finally condensed and separated at the permeation side. PTFE and PVDF, which are highly hydrophobic fluorinated polymers, are widely preferred as MD separator materials. Since polytetrafluoroethylene (PTFE) has a very strong hydrophobicity of the material itself, the contact angle to water is larger than that of polyvinylidene fluoride (PVDF), and the permeation rate of water vapor is also excellent under the same conditions. It is popular as a material.

Meanwhile. The existing single-layer PTFE hollow fiber has difficulty in controlling the fine size of the precise pore by controlling the size of the pore by using the stretching and shrinking process. However, there is a problem that it is difficult to control the precise pore size. It has a disadvantage that the backwashing efficiency is inferior due to the inability to discharge pollutants in the backwashing process because the layer for filtering contaminants is present both inside and outside in the filtration process of the pollutant.

Conventionally, a PTFE nonwoven fabric was used as a support and a PTFE layer was laminated thereon to prepare a hollow fiber. As a result, not only the manufacturing cost is significantly increased but also foreign substances are stuck in the outer pores of the PTFE, which makes it difficult to achieve the target of the high flow rate, and the backwashing efficiency is very low.

Furthermore, it is possible to produce a membrane using an external PTFE layer as an active layer in the manufacturing process of a multi-layer PTFE hollow membrane distillation membrane using a conventional PTFE paste extrusion. However, the size of the pores can be adjusted by the same stretching and shrinking process as that of the single- So that it is difficult to finely control the size of the pores, and the membrane distillation efficiency is remarkably deteriorated.

DISCLOSURE OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a membrane filtration apparatus capable of remarkably improving the filtration ability of a multi- layer PTFE hollow membrane separator membrane, Layer PTFE hollow membrane distillation separation membrane having different interlayer stretching ratios and a method for producing the same.

In order to solve the above-described problems, the present invention provides a method of producing a multi-layered PTFE hollow membrane separation membrane having different interlayer stretch ratios, comprising the steps of: (1) preparing a drawn and fired first PTFE hollow fiber; (2) compressing the PTFE paste in a compressor to preform the second PTFE hollow fiber; (3) preparing the multi-layered PTFE hollow fiber by extruding the first PTFE hollow fiber into the hollow interior of the preformed second PTFE hollow fiber and extruding it in an extruder; (4) stretching the multi-layered PTFE hollow fiber; And (5) calcining the elongated hollow fiber.

According to a preferred embodiment of the present invention, the hollow diameter of the second PTFE hollow fiber may be larger than the outer diameter of the first PTFE hollow fiber.

According to another preferred embodiment of the present invention, in step (3), the hollow of the second PTFE hollow fiber is passed through a mandrel in the extruder and is transported, and the first PTFE hollow fiber is injected into the mandrel, .

According to another preferred embodiment of the present invention, the first PTFE hollow fiber of step (1) may be 1.5 to 6 times of the first PTFE hollow fiber.

According to another preferred embodiment of the present invention, the step (2) may be carried out at a pressure of 18 to 25 ° C and a pressure of 1 to 3 MPa.

According to another preferred embodiment of the present invention, the step (3) may be carried out at a pressure of 60 to 100 ° C and a pressure of 15 to 25 MPa.

According to another preferred embodiment of the present invention, the stretching temperature in the step (4) may be 250 to 320 ° C.

According to another preferred embodiment of the present invention, the stretching ratio in the step (4) may be 1.2 to 8 times.

According to another preferred embodiment of the present invention, the firing temperature in the step (5) may be 300 to 400 ° C.

According to another preferred embodiment of the present invention, the step of heating the extruded PTFE multi-layered hollow fiber may further include the step (3) and the step (4).

According to another preferred embodiment of the present invention, the hollow interior of the preformed second PTFE hollow fiber is provided with: Layered PTFE hollow membrane separation membrane having different interlayer stretch ratios including a step of extruding and stretching a stretched and sintered first PTFE hollow fiber.

According to another preferred embodiment of the present invention, the hollow of the second PTFE hollow fiber is passed through a mandrel inside the extruder and the first PTFE hollow fiber can be injected into the mandrel and transferred.

According to another preferred embodiment of the present invention, the stretching ratio of the first PTFE hollow fiber before extrusion may be 1.2 to 8 times.

The multi-layer PTFE hollow membrane distillation separation membrane having different interlaminar stretching ratios according to the present invention comprises hollow; A first PTFE layer formed along the periphery of the hollow; And a second PTFE layer formed along an outer periphery of the first PTFE layer and having a stretch ratio smaller than a stretch ratio of the first PTFE layer.

According to a preferred embodiment of the present invention, the size of the hollow may be 200 to 800 탆.

According to another preferred embodiment of the present invention, the thickness of the first PTFE layer may be 150 to 500 탆.

According to another preferred embodiment of the present invention, the thickness of the second PTFE layer is 50 to 300 μm.

According to another preferred embodiment of the present invention, the stretching ratio of the first PTFE layer is 1.2 times or more, more preferably 1.5 times or more, more preferably 2 times or more, most preferably, 2 to 8 times larger.

According to another preferred embodiment of the present invention, the first PTFE layer may be a second stretch.

According to another preferred embodiment of the present invention, the first PTFE layer and the second PTFE layer may be made of the same material.

According to another preferred embodiment of the present invention, the size of the void and porosity may be such that the first PTFE layer is larger than the second PTFE layer and the density is small.

According to another preferred embodiment of the present invention, the size of the fibrils may be smaller than the first PTFE layer and the second PTFE layer.

According to another preferred embodiment of the present invention, the length of the node may be larger than the first PTFE layer and the second PTFE layer.

According to another preferred embodiment of the present invention, the first PTFE layer may not be a PTFE nonwoven fabric.

The multi-layer PTFE hollow membrane distillation membrane produced by the method of producing a multi-layer PTFE hollow membrane distillation membrane having different interlayer stretching ratios according to the present invention is characterized in that the filtration capacity of the multi-layer PTFE hollow membrane distillation membrane Can be remarkably improved.

In addition, since the problem of foreign substances being trapped in the pores in the filtration step is reduced, the filtration ability is remarkably improved, and filtration at a high flow rate becomes possible, and backwashing becomes very simple.

1 is a flowchart illustrating a method of manufacturing a multi-layered PTFE hollow membrane separation membrane having a different interlayer stretch ratio according to a preferred embodiment of the present invention.
2 is a schematic diagram of a compressor that can be used in the present invention.
FIG. 3 is a schematic diagram of an extruder which can be used in the present invention, and FIG. 4 is a schematic diagram of a rear stage of an extruder which can be used in the present invention.
5 is a cross-sectional view of a multi-layered PTFE hollow membrane separation membrane according to a preferred embodiment of the present invention.
6 is a perspective view showing a membrane distillation separation membrane module according to a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings.

As described above, in order to produce a conventional multi-layered PTFE hollow membrane distillation membrane PTFE multi-layered hollow fiber, a hollow fiber was prepared by laminating a PTFE nonwoven fabric as a support and a PTFE layer thereon. As a result, not only the manufacturing cost is significantly increased but also foreign substances are stuck in the outer pores of the PTFE, which makes it difficult to achieve the target of the high flow rate, and the backwashing efficiency is very low.

Accordingly, the present invention provides a method for producing a multi-layer PTFE hollow membrane separation membrane having different interlayer stretch ratios, comprising the steps of: (1) preparing a drawn and fired first PTFE hollow fiber; (2) compressing the PTFE paste in a compressor to preform the second PTFE hollow fiber; (3) preparing the multi-layered PTFE hollow fiber by extruding the first PTFE hollow fiber into the hollow interior of the preformed second PTFE hollow fiber and extruding it in an extruder; (4) stretching the multi-layered PTFE hollow fiber; And (5) sintering the elongated hollow fiber to solve the above-described problem. This can significantly improve the filtration capability of the multi-layer PTFE hollow membrane distillation membrane while minimizing the increase in manufacturing costs.

In addition, since the problem of foreign substances being trapped in the pores in the filtration step is reduced, the filtration ability is remarkably improved, and filtration at a high flow rate becomes possible, and backwashing becomes very simple.

1 is a flow chart showing a method for producing a multi-layer PTFE hollow membrane distillation separation membrane having different interlayer stretching ratios according to a preferred embodiment of the present invention, and a method for producing the multi-layer PTFE hollow membrane separation membrane of the present invention, As follows.

First, the first PTFE hollow fiber drawn and fired as the step (1) is prepared (S1). Generally, in order to produce a multi-layered PTFE hollow fiber, PTFE is fused and stretched using a PTFE nonwoven fabric as a support, or a first PTFE layer and a second PTFE layer paste are prepared and a multi-layered PTFE hollow fiber is produced in a preliminary molding and / , Whereas in the present invention, a first PTFE hollow fiber already drawn and fired is used as a PTFE support layer forming the first PTFE layer (inner layer). Thereafter, the first PTFE hollow fiber is used as a first PTFE layer (support layer), and the preformed PTFE hollow fiber is extruded thereon to produce a multilayer hollow fiber, which is then stretched so that the first PTFE layer (inner layer) . As a result, the first PTFE layer has a higher stretch ratio than the second PTFE layer, thereby giving a difference in various physical properties of the first PTFE layer and the second PTFE layer. As a result, It is possible to manufacture an improved multilayered PTFE hollow membrane separation membrane. The first PTFE hollow fiber may be produced by a conventional PTFE hollow fiber manufacturing method, and may be manufactured through PTFE paste production, preforming, extrusion, drying, stretching and firing. Among them, the stretching process may be stretched by 1.1 to 8 times, but is not limited thereto. On the other hand, the size of the first PTFE hollow fiber may be sufficient to be inserted into the hollow interior of the preformed second PTFE hollow fiber in the extrusion step.

Next, in step (2), the PTFE paste is compressed in a compressor to preform the second PTFE hollow fiber (S2). The PTFE powder contained in the paste of the present invention can be used without limitation as long as it is usually used in a PTFE hollow fiber membrane. Preferably, the PTFE powder may have an average particle size of 300 to 500 탆, but is not limited thereto. The molecular weight and the like are not particularly limited, and commercially available products may be used. Examples thereof include Polyflon F-104 (Daikin Industries) and Fluon CD-123 (Asahi ICI Fluoropolymers Co., Ltd.).

The liquid lubricant included in the paste of the present invention is for performing smooth extrusion and preform formation while wetting the surface of the PTFE fine powder and is not particularly limited as long as it is a material that can be removed by means such as evaporation extraction by heat after forming into a hollow fiber . For example, as the liquid lubricant, various alcohols, ketones, esters, and the like may be used in addition to hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, and xylene.

The liquid lubricant included in the paste of the present invention is for performing smooth extrusion and preform formation while wetting the surface of the PTFE fine powder and is not particularly limited as long as it is a material that can be removed by means such as evaporation extraction by heat after forming into a hollow fiber . For example, as the liquid lubricant, various alcohols, ketones, esters, and the like may be used in addition to hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, and xylene. According to a preferred embodiment of the present invention, the paste may include 10 to 50 parts by weight of a liquid lubricant based on 100 parts by weight of polytetrafluoroethylene (PTFE) powder.

Thereafter, the paste is compressed in a compressor and preformed into a hollow fiber. Specifically, the compressor that can be used in the present invention can be used without limitation as long as it is usually used for forming a polymer hollow fiber membrane. 2 is a schematic view of a compressor that can be used in the present invention. When the paste is introduced into the compressor 20 for producing a hollow fiber membrane, it flows through the outer space 22 of the hollow forming portion 21, The paste can be preformed in the form of a hollow fiber. The cross-sectional shape of the hollow forming portion 21 may be circular, and the diameter may be adjusted according to the hollow size of the desired hollow fiber.

On the other hand, the temperature and pressure inside the compressor can be set according to the condition of the compressor applied when manufacturing a conventional PTFE hollow fiber membrane, preferably at a temperature of 18 to 25 ° C and a pressure of 1 to 3 MPa.

Next, (3) the first PTFE hollow fiber is inserted into the hollow interior of the preformed second PTFE hollow fiber and extruded in an extruder to produce a multi-layer PTFE hollow fiber (S3). Specifically, the extruder which can be used in the present invention can be used without limitation as long as it is usually used for the production of a polymer hollow fiber membrane.

Meanwhile, according to a preferred embodiment of the present invention, the first PTFE hollow fiber is inserted into the hollow interior of the preformed second PTFE hollow fiber and extruded through an extruder to produce a multi-layer PTFE hollow fiber.

3 is a schematic view of an extruder according to a preferred embodiment of the present invention. The second PTFE hollow fiber 120 preliminarily formed through the step (2) has a mandrel 110 ), And is extruded while being conveyed to the rear end of the extruder (right side in Fig. 3). At this time, the first PTFE hollow fiber 150 drawn and fired in step (1) is introduced into the hollow part 111 of the mandrel, and the first PTFE hollow fiber 150 inserted is also fed to the rear end of the extruder (Right side in Fig. 3).

FIG. 4 is an enlarged schematic view of the rear end (right side) of the extruder of FIG. 3, wherein the mandrel 110 is in communication with the nipple 130 and the hollow portion 111 of the mandrel is connected to the hollow portion 131 of the nipple 130 ). As a result, the first PTFE hollow fiber 150 injected into the hollow portion 111 of the mandrel is transferred to the hollow portion 131 of the nipple 130, and the first PTFE hollow fiber 150, which is transported through the mandrel 110, The yarn 120 is transferred to the nipple 130 communicated with the mandrel 110 and extruded and then transferred to the outside of the extruder 100. At this time, The first PTFE hollow fiber 150 forms the inner layer (first PTFE layer) while the second PTFE hollow fiber 120 is extruded directly into the hollow interior of the second PTFE hollow fiber 120, 2 PTFE layer) is produced. Subsequently, the extruded PTFE hollow fiber including the low-temperature gas therein is continuously subjected to a drying and stretching process described later. Meanwhile, the coupling between the nipple 130 and the mandrel 110 can be achieved by various known means, and the coupling portion 125 of the nipple and the mandrel is coupled through the threaded coupling, The feed amount of the hollow fiber can be appropriately adjusted.

The extrusion conditions may be performed under the condition of the extrusion process of a conventional PTFE hollow fiber membrane, and preferably the step (3) may be carried out at a pressure of 15 to 25 MPa at 60 to 100 ° C.

Next, in step (4), the extruded hollow fiber is heated to remove the liquid lubricant (S4). Specifically, the heating temperature of the hollow fiber may be in the range of a temperature at which the liquid lubricant is removed, and preferably 110 to 150 ° C. The heating time can be performed for 10 seconds to 10 minutes.

In the next step (5), the hollow fiber having the liquid lubricant removed is stretched to form pores in the hollow fiber (S5). Specifically, a conventional PTFE hollow fiber is fed through a roller. In this case, the PTFE hollow fiber can be stretched in the longitudinal direction by using the speed difference between the rollers, but not limited thereto. The PTFE hollow fiber can be stretched according to a stretching method used in ordinary hollow fiber production. The stretching temperature may also be 250 to 320 ° C, but is not limited thereto, and the stretching ratio may be stretched by 1.2 to 8 times. After the stretching process, pores are formed by forming fibrils and nodes inside the hollow fiber.

Next, in step (6), the stretched PTFE hollow fiber membrane is sintered to prevent heat shrinkage (S6). The firing temperature in the step (6) may be performed at 300 to 400 ° C for 10 seconds to 10 minutes.

The multi-layer PTFE hollow membrane distillation membrane produced by the above-mentioned method can maximize the filtration ability because the interlayer stretching ratio is different. 5 is a cross-sectional view of a multi-layer PTFE hollow membrane distillation separation membrane according to an embodiment of the present invention. Referring to FIG. 5, the multi-layer PTFE hollow membrane separation membrane 200 according to an embodiment of the present invention includes hollow A first PTFE layer 220 formed along the periphery of the hollow and a second PTFE layer 230 formed along the periphery of the first PTFE layer 220.

The multi-layer PTFE hollow membrane distillation membrane produced by the above-mentioned method can maximize the filtration ability because the interlayer stretching ratio is different. 5 is a cross-sectional view of a multi-layer PTFE hollow membrane distillation separation membrane according to an embodiment of the present invention. Referring to FIG. 5, the multi-layer PTFE hollow membrane separation membrane 200 according to an embodiment of the present invention includes hollow A first PTFE layer 220 formed along the periphery of the hollow and a second PTFE layer 230 formed along the periphery of the first PTFE layer 220.

First, the thickness a of the hollow 210 may be 200 to 800 탆. The thickness (b) of the first PTFE layer 220 formed along the periphery of the hollow 210 may be 150 to 500 탆. The thickness (b) of the second PTFE layer 230 formed along the outer periphery of the first PTFE layer 220 may be 50 to 300 탆.

On the other hand, the first PTFE layer 220 and the second PTFE layer 230 have different stretching ratios. Preferably, the stretching ratio of the first PTFE layer 220 may be greater than the stretching ratio of the second PTFE layer 230. As a result, the density of the first PTFE layer becomes smaller than that of the second PTFE layer, and the inner porosity decreases and the pore size decreases as the oil progresses from the inside to the outside. As a result, the outer dense layer has an improved removal rate, and the inner porous layer has a structure favorable for securing a high flow rate. Also, the length of the fibril becomes long and the length of the node decreases. Preferably, the porosity of the first PTFE layer is 80% or more, the strength is 60 MPa, the porosity of the second PTFE layer is 50% or more, and the strength is 60 MPa.

The multi-layered PTFE hollow membrane separation membrane of the present invention may be employed in a conventional membrane separation membrane module and used in a membrane distillation apparatus. 6 is a perspective view illustrating a membrane separation membrane module according to an embodiment of the present invention. Specifically, the membrane separation membrane module 400 includes a housing 410, an inlet 411 through which the induction solution flows, an outlet 412 through which fresh water flows after the gas is discharged, a gas outlet 413 and 414, respectively. Inside the housing 410, a distribution tube 430 and a cartridge 420 surrounding the distribution tube 430 are embedded. In the distribution tube 430, a plurality of openings 431 through which only the gas can pass without the liquid passing therethrough are located since the membrane is a hydrophobic film. The induction solution introduced from the inlet 411 flows into the distribution tube 430 and the gas or vapor separated from the induction solution by Henry's law flows from the distribution tube 430 into the opening 431 To the cartridge 420 and then to the outside through the gas outlets 413 and 414. [

Cartridge 420 includes a plurality of multi-layer PTFE hollow membrane distillation membranes of the present invention. To describe this process in more detail, a vacuum can be formed in the cartridge 420 by a vacuum pump (not shown). In this environment, when the induction solution introduced through the inlet 411 passes through the distribution tube 430, the gas is separated from the induction solution by Henry's law. The separated gas is discharged to the outside of the induction solution and passes through the opening 431 and the multilayered PTFE hollow membrane separation membrane 421 of the present invention and consequently passes through the gas outlet 413 and 414 to the membrane distillation membrane module 400, And is discharged to the outside.

The gas is discharged from the induction solution and the gas concentration in the induction solution is significantly lowered. By controlling the partial pressure of the dissolved gas using the temperature and / or the degree of vacuum, almost all the gas present in the induction solution can be separated to desalinate the induction solution have. Fresh water is discharged to the outside through the outlet 412. The derivatizing solution may be a commonly used one, and NH ₄ HCO ₃ may preferably be used.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, this embodiment is only an example for explaining the present invention in more detail, and the scope of the present invention is not limited to these embodiments.

<Examples>

75% by weight of PTFE fine powder (DF-130, Solvay) and 25% by weight of liquid paraffin (product of Exxon Mobil, trade name: Isopar-H) as a liquid lubricant were mixed to form a PTFE paste. The PTFE paste was compressed at a pressure of 3 MPa at 20 占 폚 to form a hollow preform, which was then extruded at 80 占 폚 under a pressure of 20 MPa (200 kg / cm2) and an inner diameter of 4 mm and an inner diameter of 2 mm. Then, the formed PTFE hollow fiber was heated at 120 DEG C for 5 minutes to remove liquid paraffin. Continuously, the formed PTFE hollow fiber membrane was stretched twice in the longitudinal direction at 320 DEG C by the speed difference between the rollers to form a node and a fibril to form a pore to prepare a drawn and sintered first PTFE hollow fiber.

Then, PTFE paste was formed by mixing 75% by weight of PTFE fine powder (DF-130, Solvay) and 25% by weight of liquid paraffin (Exopon Mobil product, trade name: Isopar-H) as a liquid lubricant. The PTFE paste was compressed at a pressure of 3 MPa at 20 캜 to form a hollow pre-form to prepare a second PTFE hollow fiber.

Then, the first PTFE hollow fiber was supplied through the inside of the ram extruder, and the second PTFE hollow fiber was extruded at 80 ° C through a hollowed mandrel to a pressure of 20 MPa (200 kg / cm 2) . The continuous multi-layer PTFE hollow fiber was then heated at 120 DEG C for 5 minutes to remove the liquid paraffin. The formed PTFE hollow fiber membrane was continuously stretched twice at 320 ° C in the longitudinal direction by the speed difference between the rollers to form pores with the nodes and the fibrils. The porous multi - layered PTFE hollow membrane separator was prepared by calcination at 350 ℃. The fabricated PTFE hollow fiber membrane has a structure in which the inner layer has a low density and the outer layer has a high density.

The prepared porous multi-layer PTFE hollow membrane distillation membrane had a hollow size of 0.9 mm, a single layer thickness of 0.5 mm and a double layer thickness of 0.25 mm. At this time, the average pore size is 0.4 μm and the porosity is 77.8%. A multilayer PTFE hollow fiber membrane with different interlaminar stretching ratios was prepared and the volume of the hollow fiber membranes was set to 41% in the module. A 3.5% aqueous solution of NaCl at 80 ° C was supplied at 2.0 ± 0.1 m / s to the outside of the hollow fiber membrane And the permeate side was subjected to direct contact membrane distillation (DCMD) by passing cooling water at 10 ° C at 1.0 ± 0.05 m / s. At this time, the permeability was 47.2 kg / m 2 · h and the removal rate was 99%.

<Comparative Example>

75% by weight of PTFE fine powder (DF-130, Solvay) and 25% by weight of liquid paraffin (product of Exxon Mobil, trade name: Isopar-H) as a liquid lubricant were mixed to form a PTFE paste. The PTFE paste was compressed at a pressure of 3 MPa at 20 占 폚 to form a hollow preform and extrusion molded at 80 占 폚 in a multilayered hollow shape having an outer diameter of 1.0 mm and an inner diameter of 0.5 mm at a pressure of 20 MPa (200 kg / Then, the formed multi-layered PTFE hollow fiber was heated at 120 ° C for 5 minutes to remove liquid paraffin. Continuously, the formed PTFE hollow fiber membrane was stretched twice in the longitudinal direction at 320 DEG C by the speed difference between the rollers to form a node and a fibril to form pores, thereby producing a drawn and fired multi-layered PTFE hollow membrane distillation membrane Respectively. The prepared porous multi - layer PTFE hollow membrane distillation membrane had a hollow size of 0.9 mm, a single layer thickness of 0.6 mm and a double layer thickness of 0.45 mm. At this time, the average pore size is 1.0 탆 and the porosity is 60%.

<Experimental Example>

(1) Backwash recovery rate

The flow rate was measured after backwashing for 1 minute after 29 minutes of operation, and the value of [backwash flow rate / initial (initial operation start flow rate)] was expressed as backwash recovery rate.

Contact angle (°)
(advancing) Average pore (탆) Thermal conductivity
(W / mK) Porosity (%)
(porosity) Removal rate (%) Transmittance (kg / ㎡ · h) Backwash recovery rate (%) Tensile Strength (MPa) Example 1 121 0.4 0.20 77.8 99 52.1 82 48 Comparative Example 1 121 1.0 0.20 60 99 37.3 31 48

As can be seen from Table 1, the multi-layered PTFE hollow membrane separation membrane of the present invention having different interlayer stretching ratios of the present invention has an asymmetric structure as compared with the multilayered PTFE separation membrane having the same interlaminar stretching ratio as the comparative example, , It can be confirmed that the permeability is very excellent because the porosity on the permeation side is higher.

The multi-layer PTFE hollow membrane distillation separation membrane produced by the production method of the present invention has excellent filtering ability and can be widely used in fields such as a desalination apparatus.

Claims (19)

(1) preparing a stretched and sintered first PTFE hollow fiber;
(2) compressing the PTFE paste in a compressor to preform the second PTFE hollow fiber;
(3) preparing the multi-layered PTFE hollow fiber by extruding the first PTFE hollow fiber into the hollow interior of the preformed second PTFE hollow fiber and extruding it in an extruder;
(4) stretching the multi-layered PTFE hollow fiber; And
(5) firing the elongated hollow fiber; and (5) firing the elongated hollow fiber. The method according to claim 1,
Wherein the first PTFE hollow fiber has a larger hollow fiber diameter than the first PTFE hollow fiber, and the second PTFE hollow fiber has a larger hollow fiber diameter than the first PTFE hollow fiber. The method according to claim 1,
In the step (3), the hollow of the second PTFE hollow fiber is passed through a mandrel in the extruder, and the first PTFE hollow fiber is injected into the mandrel and transferred. The multi-layer PTFE (Method for producing a hollow membrane distillation separation membrane). The method according to claim 1,
Wherein the first PTFE hollow fiber of step (1) is stretched by 1.2 to 8 times, and wherein the interlaminar stretching ratio is different. The method according to claim 1,
Wherein the step (2) is carried out at a pressure of 18 to 25 ° C and a pressure of 1 to 3 MPa, and the step (3) is carried out at a pressure of 60 to 100 ° C and a pressure of 15 to 25 MPa. (Method for manufacturing PTFE hollow membrane distillation separation membrane). The method according to claim 1,
Wherein the stretching temperature in the step (4) is 250 to 320 ° C and the stretching ratio is 1.2 to 8 times. The method according to claim 1,
Wherein the calcination temperature in the step (5) is 300 to 400 ° C. The method according to claim 1,
Further comprising the step of heating the extruded PTFE multi-layered hollow fiber between the step (3) and the step (4), wherein the interlayer stretching ratio is different. In the hollow interior of the preformed second PTFE hollow fiber; Layer PTFE hollow membrane separation membrane having different interlaminar stretching ratios, including a step of extruding and stretching a stretched and sintered first PTFE hollow fiber. 10. The method of claim 9,
Wherein the hollow of the second PTFE hollow fiber is passed through a mandrel in the extruder and is transported while the first PTFE hollow fiber is fed into the mandrel and transported. &Lt; / RTI &gt; 10. The method of claim 9,
Wherein the stretching ratio of the first PTFE hollow fiber prior to the extrusion is 1.2 to 8 times and the stretching ratio of the multilayer PTFE hollow fiber after the extrusion is 1.2 to 8 times the interlaminar stretching ratio.


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