JP2015029923A - Hollow fiber membrane for degassing and hollow fiber membrane module for degassing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow fiber membrane for degassing having a small pressure loss, capable of obtaining high degassing efficiency even when a hollow fiber membrane module is enlarged, and to provide a hollow fiber membrane module for degassing.SOLUTION: A hollow fiber membrane includes a homogeneous layer having a non-porous structure, and a support layer having a porous structure, for supporting the homogeneous layer. A hollow fiber membrane for degassing has an eccentric structure in which the homogeneous layer is arranged on the external surface of the hollow fiber membrane or on a region at 20 μm or shorter from the external surface, and the position of the center gravity is deviated from the position of the center of a cylindrical outer peripheral surface of the hollow fiber membrane.

Description

  The present invention relates to a deaeration hollow fiber membrane to which a crimp is applied and a deaeration hollow fiber membrane module using the hollow fiber membrane.

  Hollow fiber membranes equipped with separation membranes such as reverse osmosis membranes, ultrafiltration membranes, microfiltration membranes, deaeration membranes, dialysis membranes in separation processes such as pervaporation, solvent filtration, solvent treatment, chemical solution deaeration Module is in use. Among them, as a degassing membrane used for gas-liquid separation or the like, a hollow fiber membrane is widely used because a membrane area per unit volume is large, and a dissolved gas in a liquid to be treated can be efficiently degassed even in a small unit. .

  The degassing hollow fiber membrane module includes a housing case and a plurality of hollow fiber membranes fixed in the housing case so that the inner side and the outer side of the membrane are isolated from each other. Module. The hollow fiber membrane module for deaeration is roughly divided into an internal reflux type in which the liquid to be treated is flowed inside the hollow fiber membrane and the external side is decompressed, and a liquid to be treated is flowed inside the hollow fiber membrane from the inside. It is classified as an external reflux type that decompresses the side.

As the external reflux type, for example, a tubular core portion having one end closed and the other end opened and a plurality of holes formed in the side wall, and a membrane surrounding the core portion are provided. A plurality of hollow fiber membranes fixed so that the inner side and the outer side of the core are separated from each other, the liquid to be treated is flowed from the inner side of the core part to the outer side of the hollow fiber membrane through the hole, There is a hollow fiber membrane module in which the inside of the hollow fiber membrane is decompressed (Patent Document 1).
Furthermore, an external reflux type hollow fiber membrane module using a sheet in which each hollow fiber membrane is knitted in a monofilament state is also known (Patent Documents 2 and 3).

  In these hollow fiber membrane modules, further increase in performance and size are achieved by increasing the number of hollow fiber membranes in the container. However, when the number of hollow fiber membranes in the hollow fiber membrane module container is increased to increase the filling, the effective membrane area decreases due to the close contact between the hollow fiber membranes, and the occurrence of drift causes the diffusion performance in the hollow fiber membrane module. Causes a drop. Therefore, as a method of improving the flow of the target liquid that causes a decrease in diffusion performance in the hollow fiber membrane module and increasing the deaeration efficiency, a hollow fiber membrane is obtained by winding a fiber around the permeable membrane in a spiral shape to form a tubular body. There has been proposed a method for preventing close contact between them (Patent Document 4).

  However, the hollow fiber membrane module described in Patent Document 4 not only increases the cost due to the complexity of the manufacturing process, but also by arranging the covering yarn, Since the number of fillings is reduced, the size of the hollow fiber membrane module has to be increased, which further increases the cost.

  In addition, in the degassing hollow fiber membrane, it is possible to make a turbulent state by increasing the flow rate of the liquid to be treated flowing outside, but in this case, a detained portion is generated in the membrane hollow fiber membrane module. Qi efficiency decreases. To solve this problem, we try to create a turbulent flow effect by using hollow fiber membrane sheets or hollow fiber membrane sheets that are knitted in a sled shape. However, the monofilament hollow fiber membrane is processed into a sled shape. This has problems such as increased processing accuracy and cost.

  As a method for solving this problem, a method for imparting crimp to a hollow fiber membrane as typified by crimping has already been proposed. Regarding the method of applying crimp while suppressing the crushing and flattening of the hollow fiber membrane, for example, it is called a gear system, and it has a meshing tooth and pushes the thread between two continuously rotating gears, either simultaneously or continuously. A method of fixing the crimp by heat treatment (Patent Document 5), a method of conveying while twisting between a number of yarn guides traveling at constant intervals with continuous yarn, and a method of heat-setting by heat treatment (Patent Document 6) Etc. are raised.

JP 2010-269307 A Japanese Patent No. 4026037 JP 2012-161793 A Japanese Patent Publication No.59-18084 Japanese Patent Laid-Open No. 09-021024 JP-A-6-212520

  The present invention solves the problems of the prior art, and is to make the flow of the liquid to be treated flowing outside the hollow fiber membrane of the deaeration membrane hollow fiber membrane module uniform. In particular, a deaerated hollow fiber membrane provided with crimps to make the flow of the liquid to be treated uniform, a deaerated hollow fiber membrane module using the same, and a deaerated hollow capable of stably applying such crimps A method for producing a yarn membrane and a deaerated hollow fiber membrane module is provided.

  The gist of the present invention for solving the above problems is a hollow fiber membrane having a homogeneous layer having a non-porous structure and a support layer for supporting the homogeneous layer of the thin film with a porous structure, wherein the homogeneous layer is hollow. It is arranged in the outermost layer of the yarn membrane or in an area of 20 μm or less from the outer surface, and has a decentered structure in which the center of gravity is shifted from the center position of the cylindrical outer peripheral surface of the hollow fiber membrane. The purpose is to employ a hollow fiber membrane.

If the hollow fiber membrane for deaeration of this invention is used, between membranes can be disperse | distributed uniformly and high deaeration efficiency is obtained.
Furthermore, in the degassing hollow fiber membrane of the present invention, crimping can be generated by the inner ridges and heat treatment, and the flow of the liquid to be treated is promoted to turbulent flow as a whole, while being treated near the outer surface. It is suppressed that the liquid flow is disturbed excessively. Therefore, a stay part can be eliminated, promoting a turbulent flow.

It is a schematic diagram which shows an example of the hollow fiber membrane for deaeration of this invention. It is a schematic diagram which shows an example of the hollow fiber membrane for deaeration of this invention. It is a schematic diagram which shows an example of the hollow fiber membrane for deaeration of this invention. It is explanatory drawing which shows the wavelength of a crimp.

(Crimp)
The crimp referred to in the present invention refers to a waveform shape with respect to a straight line. In the crimp according to the present invention, it is preferable from the viewpoint of improving the liquid flow in the hollow fiber membrane module that the repetition of wave height and wavelength is constant. That the repetition is constant means that the crimp is continuously applied with a numerical value in which the change rate of the wave height and wavelength does not exceed the range of plus or minus 10% of the average value.
The wave height and wavelength are determined as follows. That is, the wavelength of the crimp represents the length from the top of the mountain shown in FIG. 4 to the top of the next mountain, and the wave height represents the length shown in FIG. 4 from the convex side of the top of the mountain to the concave side of the bottom of the valley. . In the method for measuring the wave height and wavelength, the hollow fiber membrane immediately after crimping or the hollow fiber membrane immediately after being inserted into the hollow fiber membrane module case is taken out as much as possible without applying tension as much as possible, and 10 hollow fiber membranes are taken out of them. Are randomly selected, and the wave height and wavelength of each yarn are measured arbitrarily, and the average value of the ten yarns is set as the wave height and wavelength of the hollow fiber membrane.

The crimp of the present invention preferably has a wavelength of 15 mm or more. Crimp wavelength is 1
When it is less than 5 mm, the flow of the dialysate or the buffer in the hollow fiber membrane module is improved even if the crimp wave height applied to the hollow fiber membrane is small, which is preferable from the viewpoint of improving the performance of the hollow fiber membrane module. When the inner diameter size of the hollow fiber membrane module case is increased, the filling rate is reduced and the cost is increased. On the other hand, it is preferably 40 mm or less from the viewpoint of securing a sufficient flow of the target liquid in the hollow fiber membrane module.
In this case, the wave height of the crimp is preferably 0.5 mm or more.
When the wave height is small, the hollow fiber membrane approaches a straight shape, so that the effect of suppressing adhesion between the hollow fiber membranes becomes thin. Further, when the wave height is large, the effect of suppressing the adhesion between the hollow fiber membranes becomes too large, so that the yarn bundle diameter becomes large and the hollow fiber membrane module size becomes too large.
From the above, the crimp amplitude is preferably 0.5 mm or more, and more preferably 1 mm or more. Moreover, 4 mm or less is preferable and 3 mm or less is more preferable.

(Number of hollow fiber membrane yarns)
The number of combined yarns of the crimped hollow fiber membrane 1 is preferably 2 to 32. When the number of combined yarns is more than 32, the overlap between the hollow fiber membranes becomes remarkable, so that crimping may be insufficient, or the charge amount may increase due to rubbing between the hollow fibers, and yarn disturbance may occur. .
In terms of yarn disturbance suppression, the number of combined yarns is preferably 32 or less. However, if the number of combined yarns is reduced to approach the state of single yarn splitting, the width of the machine is increased in order to achieve more reliable crimping. Therefore, it is necessary to suppress the overlap of the yarns, which is not suitable for cost reduction. Therefore, although there are places depending on the entire working weight of the hollow fiber membrane, the number of combined yarns is preferably 2 to 32, more preferably 4 to 24 or more, and still more preferably 8 to 16.
As a crimping method in the hollow fiber membrane of the present invention, a method of heat-treating the formed hollow fiber membrane is adopted, but crimping by a gear or the like may be performed together.
In addition, the above crimp property is manifested by the manifestation of the crimp in the hollow fiber membrane. In the state before the heat treatment, an actual crimp in which a three-dimensional crimp is completely expressed may be used, or a latent crimp type in which a crimp is expressed (a crimp expression is generated when heat is applied to a fiber) may be used.
In the case of a degassing hollow fiber membrane having a latent crimp property, it may be set to a temperature range in which crimp is expressed. For example, when Tm is the low melting peak temperature of either the support layer or the homogeneous layer, Tm− 10 (° C.) or more Preferably, it is set in the range of Tm−10 (° C.) to Tm + 60 (° C.).

(Hollow fiber membrane for deaeration)
An example of the degassing hollow fiber membrane of the present invention will be shown and described.
As a method of imparting latent crimpability in the hollow fiber membrane of the present invention, the shape of the center of gravity deviated from the center of gravity assumed from the outer diameter of the hollow fiber membrane, or the thick part is 1/3 or less of the whole It is preferable to have a feature of being unevenly distributed in the region. FIG. 1 shows a schematic view of an embodiment in which the hollow portion of the present invention is eccentric so that the center does not coincide with the outer peripheral portion of the membrane.
Moreover, in FIG. 2, the schematic diagram of one Embodiment which shows the shape which a part of hollow part is cut and is made into the half-moon shape is shown. 3 and 4 are schematic views of an embodiment in which one or a plurality of protrusions are provided on the inner peripheral portion and the region is unevenly distributed in a region equal to or less than 1/3 of the entire region. In particular, an eccentric type cross section is preferable because a desired wave-shaped crimp and / or spiral crimp can be easily expressed. Furthermore, as shown in FIGS. 3 and 4, the inner protrusion 14 is formed on the inner surface 12 of the hollow fiber membrane 10 so as to continuously extend in the longitudinal direction of the hollow fiber membrane 10. By forming the inner ridge 14 on the inner surface 12 of the hollow fiber membrane 10, shrinkage spots due to a difference in film thickness occur in the circumferential direction. Specifically, since the shrinkage of the thick part is larger than that of the thin part, the crimp can be generated by the difference in the circumferential direction. By forming the crimp, it is possible to form uniform gaps between the membranes without arranging them evenly in the membrane hollow fiber membrane module. Therefore, the ratio of the gas in the liquid to be treated to the outer surface 12 is increased. Larger and better degassing performance is obtained.

As for the inner side protrusion 14, the cross-sectional shape cut perpendicularly to the longitudinal direction is not particularly limited, and examples thereof include a triangle, a quadrangle, a semicircle, and an oval semicircle. The cross-sectional shape of the inner ridge 14 has the same width from the root to the tip of the inner ridge 14 because the deposits deposited on the inner surface 12 of the hollow fiber membrane 10 are easily separated and discharged by physical cleaning. Alternatively, a shape in which the width decreases from the root portion toward the tip is preferable.
The height of the inner protrusion 14 is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more. If the height of the inner protrusion 14 is equal to or higher than the lower limit value, the turbulent friction coefficient on the inner surface 12 can be easily reduced. Further, the height of the inner ridge 14 is preferably not more than 3 times the width of the root portion, more preferably not more than 2 times. If the height of the inner ridge 14 is equal to or less than the upper limit value, it is easy to suppress the inner ridge 14 from being deformed or damaged due to the swinging of the hollow fiber membrane 10 or mutual collision. Moreover, the shape of the inner side protrusion 14 at the time of hollow fiber membrane manufacture becomes stable, and the productivity of the hollow fiber membrane 10 becomes better.
The height of the inner ridge 14 is the distance from the position of the inner surface 12 to the tip of the inner ridge 14 when the inner ridge 14 is not present in the portion where the inner ridge 14 is formed. Say.

The width of the inner protrusion 14 is preferably 5 μm or more, and more preferably 10 μm or more. If the width of the inner ridge 14 is equal to or greater than the lower limit value, the inner ridge 14 is unlikely to be deformed or damaged by the swinging of the hollow fiber membrane 10 during deaeration. Further, the width of the inner protrusion 14 is preferably 50 μm or less, and more preferably 40 μm or less. If the width | variety of the internal side protrusion 14 is below an upper limit, it will become easy to obtain the outstanding deaeration performance.
The width | variety of the inner side protrusion 14 means the length which the inner side protrusion 14 occupies in the periphery of the internal diameter of each protrusion part.
The cross-sectional shape, height, and width of the inner ridge 14 can be controlled by adjusting the shape of the groove provided to form the inner ridge 14 in the nozzle cap when the hollow fiber membrane is manufactured.
The ratio X of the projected area obtained by projecting the inner ridge 14 onto the inner surface 12 of the hollow fiber membrane 10 is the sum of the projected area and the area of the inner surface 12 where the inner ridge 14 is not formed. Therefore, 1/3 (33.3%) or less is preferable, more preferably 5 to 15%. If the ratio X of the projected area is equal to or greater than the upper limit value, it is not preferable because the shrinkage difference between the internal protrusion and other portions is less likely to cause crimping.
The number of the inner protrusions 14 may be plural or one. From the viewpoint of crimp expression, it is preferable to adjust the projected area ratio X so as to be within the above range.

The degassing hollow fiber membrane 10 (hereinafter referred to as “hollow fiber membrane 10”) of the present embodiment is formed with an inner ridge 14 having a continuous shape in the longitudinal direction on the inner surface 12 of the membrane. An external protrusion 18 having a shape continuous in the longitudinal direction is formed on the surface 16.
Examples of the hollow fiber membrane 10 include a composite membrane having a porous support layer and a non-porous homogeneous layer. The composite membrane may be a two-layer composite membrane of a homogeneous layer and a support layer, or a three-layer composite membrane in which a homogeneous layer is sandwiched between two support layers. Moreover, the number of homogeneous layers and support layers is not limited to those described above, and the total of them may be a composite membrane having four or more layers. As the hollow fiber membrane 10, a three-layer composite membrane is preferable.

(Homogeneous layer)
The homogeneous layer is a layer that is non-porous and has gas permeability.
The polymer constituting the homogeneous layer (hereinafter referred to as “polymer A”) is not particularly limited, and various polymers that can be used as a homogeneous layer having gas permeability of the degassing hollow fiber membrane can be used.
Examples of the polymer A include polyolefin-based resins obtained mainly from olefins, which may be polymers obtained using only olefins or copolymers of olefins and other monomers. The polymer A may be a modified polymer of the polymer or copolymer. Specific examples of the polymer A include, for example, an olefin block copolymer (OBC), a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), a linear very low density polyethylene (VLDPE), a reactor TPO, a soft poly And methyl pentene.

If necessary, additives such as antioxidants, ultraviolet absorbers, lubricants, antiblocking agents, colorants, flame retardants, and the like are added to the homogeneous layer as long as the purpose of the present invention is not impaired. May be.
The thickness of the homogeneous layer is preferably 0.5 to 10 μm. When the thickness of the homogeneous layer is 0.5 μm or more, the pressure resistance of the hollow fiber membrane module including the hollow fiber membrane 10 becomes better. If the thickness of the homogeneous layer is 10 μm or less, the gas permeability becomes better.
The region occupied by the homogeneous layer in the hollow fiber membrane is preferably in the range of 1/10 to 1/3 from the outer surface when the thickness of the hollow fiber membrane is 1. When the hollow fiber membrane is fixed in the hollow fiber membrane module, the potting material is impregnated from the outer surface of the membrane to produce an anchor effect. The homogeneous layer is non-porous and cannot be impregnated with the potting material.

Further, if the region occupied by the homogeneous layer is a region of 1/10 or more from the outer surface, the polymer A is dragged by the polymer B of the inner layer in the stretching step for making the polymer B forming the support layer porous. It is easy to suppress defects that occur.
Moreover, if the region occupied by the homogeneous layer is made 1/3 or less from the outer surface, the region where the potting material is impregnated increases, and it is easy to suppress damage to the membrane due to the influence of bending or the like.
The inner diameter of the hollow fiber membrane 10 is preferably 10 to 500 μm, and more preferably 50 to 200 μm. If the inner diameter of the hollow fiber membrane 10 is equal to or greater than the lower limit value, it is easy to reduce the pressure loss when the inside of the hollow fiber membrane 10 is deaerated. If the inner diameter of the hollow fiber membrane 10 is equal to or less than the upper limit value, it is preferable because the outer membrane diameter can be reduced and a sufficient membrane area can be secured.

(Support layer)
The support layer is a porous layer that supports the homogeneous layer. The polymer constituting the support layer (hereinafter referred to as “Polymer B”) is a material that is compatible with or adheres to Polymer A, and that can be formed into a porous material that does not delaminate during the stretching process. If there is no particular limitation.
As the polymer B, high-density polyethylene, polypropylene, and polymethylpentene are preferable. It is preferable that the polymer A and the polymer B have the same melting characteristics from the viewpoint of moldability. Specifically, the smaller the difference between the MFRD (the melt flow rate of Code D. JIS K7210, 190 ° C., 2.16 kg load), the polymer A and the polymer B are more preferable.
If necessary, additives such as antioxidants, ultraviolet absorbers, lubricants, antiblocking agents, colorants, flame retardants are added to the support layer as long as the purpose of the present invention is not impaired. May be.

The thickness of the support layer is preferably 10 to 200 μm. When the thickness of the support layer is 10 μm or more, the mechanical strength of the hollow fiber membrane 10 becomes better. When the thickness of the support layer is 200 μm or less, the outer diameter of the hollow fiber membrane 10 becomes thinner, and the filling rate of the hollow fiber membrane 10 in the hollow fiber membrane module can be easily increased.
The thickness of the support layer is the thickness of each support layer when the hollow fiber membrane has a plurality of support layers.
As for the porosity of a support layer, 30-80 volume% is preferable with respect to the whole support layer (100 volume%). When the porosity is 30% by volume or more, excellent gas permeability is easily obtained. When the porosity is 80% by volume or less, mechanical strength such as pressure resistance becomes better.
The size of the pores in the support layer is not particularly limited as long as sufficient gas permeability and mechanical strength are satisfied.
The outer diameter of the hollow fiber membrane 10 is preferably 100 to 2000 μm, and more preferably 100 to 300 μm. If the outer diameter of the hollow fiber membrane 10 is equal to or greater than the lower limit value, it is easy to make a sufficient gap between the hollow fiber membranes during the production of the hollow fiber membrane module, and the potting material can easily enter between the hollow fiber membranes. If the outer diameter of the hollow fiber membrane 10 is less than or equal to the upper limit value, the size of the entire hollow fiber membrane module can be reduced even when a hollow fiber membrane module using a large number of hollow fiber membranes is manufactured. Thereby, since the volume of the potting portion is also reduced, it is easy to suppress a decrease in dimensional accuracy due to shrinkage of the potting material during the potting process.

(Production method)
The inner ridge 14 of the hollow fiber membrane 10 can be formed by using a nozzle cap in which a groove having a shape complementary to the shape of the inner ridge 14 is formed on the inner peripheral side. Similarly, the outer ridge portion 18 of the hollow fiber membrane 10 can be formed by using a nozzle cap in which a groove having a shape complementary to the shape of the outer ridge portion 18 is formed on the outer peripheral side. Further, the outer ridge portion 18 may be formed by manufacturing a hollow fiber membrane in which the outer ridge portion 18 is not formed, and then supplying a molten polymer to the outer surface of the hollow fiber membrane. . Examples of the method for producing the hollow fiber membrane 10 include a method having a spinning step and a stretching step described later.

(Spinning process)
For example, in the case of the hollow fiber membrane 10 having a three-layer structure, the innermost layer nozzle portion, the intermediate layer nozzle portion, and the outer side protrusion, each having a groove having a shape complementary to the shape of the inner protrusion 14, are formed on the inner peripheral side. The outermost layer nozzle portion in which a groove having a shape complementary to the shape of the strip portion 18 is formed on the outer peripheral side uses a composite nozzle base arranged concentrically.
In this case, the molten polymer B is supplied to the outermost layer nozzle portion and the innermost layer nozzle portion, and the molten polymer A is supplied to the intermediate layer nozzle portion. Then, the polymer A and the polymer B are extruded from the respective nozzle portions, and are cooled and solidified in an unstretched state while appropriately adjusting the extrusion speed and the winding speed. Thereby, a hollow fiber membrane precursor having a three-layer structure in which an unstretched homogeneous layer precursor is sandwiched between two unstretched support layer precursors in a non-porous state is obtained.
The discharge temperature of the polymer A and the polymer B may be in a range where they can be sufficiently melted and spun.

(Stretching process)
The unstretched hollow fiber membrane precursor obtained by melt spinning is preferably subjected to a constant length heat treatment (annealing treatment) below the melting points of the polymer A and the polymer B before stretching.
The constant-length heat treatment is preferably performed at 105 to 140 ° C. for 8 to 16 hours with polyethylene. If the temperature of the constant length heat treatment is 105 ° C. or higher, a hollow fiber membrane with good quality can be easily obtained. If the temperature of the constant-length heat treatment is 140 ° C. or less, sufficient elongation can be easily obtained, stability during stretching is improved, and stretching at a high magnification is facilitated. Moreover, if processing time is 8 hours or more, it will be easy to obtain a hollow fiber membrane with good quality.
The hollow fiber membrane precursor is stretched under conditions that satisfy the following requirements (i) and (ii).
(I) The relationship between the stretching temperature T (° C.) and the melting point Tm (° C.) of the polymer A is Tm−20 ≦ T ≦ Tm + 40.
(Ii) The stretching temperature T is not higher than the Vicat softening point of the polymer B.
The melting point of the polymer is measured using a differential scanning calorimeter (DSC). The Vicat softening point of the polymer is measured according to JIS K7206.
When the stretching temperature T is Tm−20 (° C.) or higher, the support layer precursor is easily made porous, and the hollow fiber membrane 10 having excellent gas permeability is easily obtained. When the stretching temperature T is Tm + 40 (° C.) or less, it is easy to suppress the occurrence of defects such as pinholes due to disturbance in the polymer molecules.
If the stretching temperature T is equal to or lower than the Vicat softening point of the polymer B, it is preferable to perform cold stretching before stretching (hot stretching) performed at the stretching temperature T in the porous stretching step of the support layer precursor. . Specifically, two-stage stretching in which hot stretching is performed subsequent to cold stretching, or multi-stage stretching in which hot stretching is divided into two or more multi-stages subsequent to cold stretching is preferable.

Cold stretching is stretching that causes structural cracking of the film at a relatively low temperature and generates microcracking. The temperature of cold drawing is preferably within a range from 0 ° C. to a temperature lower than Tm-20 (° C.).
The draw ratio varies depending on the types of the polymer A and the polymer B to be used, but the final ratio (total draw ratio) with respect to the unstretched hollow fiber membrane precursor is preferably 2 to 5 times. If the total draw ratio is 2 times or more, the porosity of the support layer tends to be high, and excellent gas permeability can be easily obtained. If the total draw ratio is 5 times or less, the breaking elongation of the hollow fiber membrane 10 tends to be high.

Furthermore, for the hollow fiber membrane 10 obtained by the stretching, in order to improve the dimensional stability of the hollow fiber membrane, the hollow fiber membrane 10 is in a fixed length state or 40% or less of the fixed length. It is preferable to perform heat setting in a slightly relaxed state within the range.
In order to effectively perform heat setting, the heat setting temperature is preferably not less than the stretching temperature T and not more than the melting points of the polymer A and the polymer B.
In the degassing hollow fiber membrane of the present invention described above, the hollow portion is eccentric or the inner side protrusion is formed on the inner surface, so that the thick part is within 1/3 or less of the outer periphery of the membrane. By being formed, a difference is caused in the thermal shrinkage rate in the film thickness direction, and crimps are generated. By causing the crimp, the liquid to be processed in the vicinity of the outer surface is easily renewed, and the ratio of the gas in the liquid to be processed to be in contact with the outer surface of the film is increased, so that high deaeration efficiency is obtained.

(Hollow fiber membrane module for deaeration)
The degassing hollow fiber membrane module of the present invention can adopt the same form as a known hollow fiber membrane module except that the degassing hollow fiber membrane of the present invention is used. Hereinafter, a hollow fiber membrane module having a hollow fiber membrane 10 will be described as an example of the degassing hollow fiber membrane module of the present invention.
The degassing hollow fiber membrane module 1 (hereinafter referred to as “hollow fiber membrane module 1”) of the present embodiment has a housing case 20 and a plurality of hollow fiber membranes 10 bundled as shown in FIG. The hollow fiber membrane bundle 22 and potting portions 24A and 24B for fixing the hollow fiber membrane bundle 22 in the housing case 20 are provided.
The housing case 20 has a liquid inlet 26 formed at one end, a liquid outlet 28 formed at the other end, and a gas suction port 30 formed at the side. The gas suction port 30 is connected to decompression means such as a decompression pump.
Both ends of the hollow fiber membrane bundle 22 are fixed in the housing case 20 by potting portions 24A and 24B.

The potting portion 24A for fixing the end of the hollow fiber membrane bundle 22 on the liquid inlet 26 side is located between the liquid inlet 26 and the gas suction port 30 in the housing case 20 and the interior of the housing case 20 is on the liquid inlet 26 side. And the gas suction port 30 side. In addition, the potting portion 24B for fixing the end portion of the hollow fiber membrane bundle 22 on the liquid outlet 28 side is located between the liquid outlet 28 and the gas suction port 30 in the housing case 20 and the liquid outlet is provided inside the housing case 20. It is provided so as to be divided into 28 side and gas suction port 30 side.
The opening 10a of each hollow fiber membrane 10 in the hollow fiber membrane bundle 22 is exposed at the end surface of the potting portion 24A on the liquid inlet 26 side. Moreover, the outlet side opening 10b of each hollow fiber membrane 10 of the hollow fiber membrane bundle 22 is exposed at the end surface of the potting portion 24B on the liquid outlet 28 side.

As described above, in the hollow fiber membrane module 1, the inner side (primary side) and the outer side (secondary side) of the hollow fiber membrane 10 are separated by the potting portions 24A and 24B inside the housing case 20.
In the hollow fiber membrane module 1, the liquid to be treated supplied from the liquid inlet 26 into the housing case 20 enters the membrane through the inlet-side opening 10a of the hollow fiber membrane 10 exposed on the surface of the potting portion 24A. The liquid to be processed that flows through the inside of the membrane 10 and exits from the outlet opening 10 b flows out from the liquid outlet 28. In addition, the gas contained in the liquid to be treated passes through the hollow fiber membrane 10 and flows out from the gas suction port 30.

(Filling rate of hollow fiber membrane module)
The hollow fiber membrane provided with the fins and crimps of the present invention as described above is housed and filled in a hollow fiber membrane module case to form a degassing hollow fiber membrane module. At this time, the filling rate of the hollow fiber to be filled is preferably 40 to 55%. When the filling rate is less than 40%, the hollow fiber membrane module size is increased, and the drift prevention effect is halved. On the other hand, when the filling rate is higher than 55%, it is difficult to fill the yarn, and the possibility of damaging the yarn during filling increases. Here, the filling rate represents the percentage of the sum of the cross-sectional areas (including fin portions) of the filled hollow fibers to the hollow fiber membrane module case inner diameter area.

(Hollow fiber membrane module potting resin)
The potting material for forming the potting portions 24A and 24B is not particularly limited, and various adhesives, sealing materials, potting agents, polymers, and the like that are usually used for hollow fiber membrane modules can be used. Examples of the potting material include an epoxy adhesive and a urethane adhesive.
If the hardness of the potting portions 24A and 24B is too high compared to the hollow fiber membrane 10, the hollow fiber membrane 10 cracks in the vicinity of the end surfaces 24a and 24b opposite to the exposed end surface of the hollow fiber membrane 10 in the potting portion 24. Is likely to occur. Therefore, the potting material is preferably a urethane adhesive that does not have a very high hardness after curing.
The means for curing the potting material is not particularly limited, such as a two-component mixing reaction, ultraviolet curing, heat curing, solvent extraction and the like. However, it is essential that the hollow fiber membrane itself is not adversely affected.

(Deaeration method using hollow fiber membrane module)
Examples of the method for degassing the liquid to be treated using the hollow fiber membrane module 1 include the following methods.
A liquid to be treated containing dissolved gas is supplied from the liquid inlet 26 into the housing case 20, and the liquid to be treated flows to the outside (primary side) of the hollow fiber membrane 10, so that the inside of the hollow fiber membrane 10 (secondary) Pressure). Thereby, the dissolved gas in the liquid to be treated permeates the membrane and is separated to the inner side of the hollow fiber membrane 10 by the driving force proportional to the partial pressure difference of the dissolved gas, and is discharged from the gas suction port 30. The liquid to be treated after the deaeration process is collected from the liquid outlet 28 of the housing case 20. (External reflux system)
Moreover, in the degassing hollow fiber membrane module of the present invention, the flow of the liquid to be treated can be made uniform compared to the case where crimping is not performed, degassing efficiency can be improved, and pressure loss can be reduced. it can.
A plurality of degassing hollow fiber membrane modules of the present invention may be connected in series, or a plurality may be connected in parallel.
In addition, when the degassing hollow fiber membrane module of the present invention is used in an internal reflux system, the liquid to be treated flowing inside the hollow fiber membrane tends to be in a turbulent state, and high degassing efficiency is obtained. Moreover, the hollow fiber membrane module for internal reflux type deaeration of the present invention uses a plurality of hollow fiber membranes in a bundle, and it is easy to prevent the hollow fiber membrane module from becoming excessive.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Melting point (Tm)]
A differential scanning calorimeter (DSC) was used for measuring the melting point (Tm). Specifically, about 5 mg of sample was melted at 200 ° C. for 5 minutes, crystallized by cooling to 40 ° C. at a rate of 10 ° C./minute, and then further heated to 200 ° C. at 10 ° C./minute for melting. Melting peak temperature and end of melting [melt flow rate (MFR)]
According to JIS K7210, the melt flow rate (MFR 2.16) (g / 10 min) is measured by measuring the mass of the resin extruded in a strand shape for 10 minutes at 190 ° C. under a load of 2.16 kg using a melt indexer. Asked.

[density]
In accordance with JIS K7112, a strand obtained at the time of MFR measurement at 190 ° C. under a load of 2.16 kg was heat-treated at 100 ° C. for 1 hour, and was gradually cooled to room temperature over 1 hour, and measured using a density gradient tube. .
[Measurement method of oxygen transmission rate and nitrogen transmission rate]
The obtained gas permeable composite hollow fiber membrane was bundled in a U shape, and the end of the hollow fiber membrane was solidified with urethane resin to produce a hollow fiber membrane module. Oxygen or nitrogen is supplied from the outside of the composite hollow fiber membrane, the oxygen transmission rate (Q _O2 ) (unit: m / hour · MPa) and nitrogen at 25 ° C. with the inside (hollow part side) of the hollow fiber membrane as normal pressure The permeation rate (Q _N2 ) (unit: m / hour · MPa) was measured. The membrane area was calculated based on the inner diameter of the hollow fiber membrane. And the separation factor ( _QO2 / _QN2 ) was calculated _| required from the measured oxygen transmission rate ( _QO2 ) and nitrogen transmission rate ( _QN2 ).

[Measurement method of crimp wave height and wavelength]
A hollow fiber membrane was taken out from a bundle of hollow fiber membranes of 200 mm or more incorporated in the hollow fiber membrane module case so as not to apply a tension that would change the crimp shape during extraction. Take 10 pieces randomly from the taken out hollow fiber membranes, place an arbitrary part 18cm on the black paper with the largest height, and take care not to apply tension, (Within 0.5 cm from the top) with tape, and as shown in Fig. 1, connect one line at any position from the top to the top of the next peak with a line, measure the length, and measure the wavelength. It was.
The wave height was defined as a distance between two adjacent valleys at an arbitrary position by a straight line and a peak between the peaks between the two valleys and a straight line drawn from the peaks.
This measurement was performed on the ten hollow fiber membranes taken out, and an average value was taken. The average value is expressed in millimeters, and the second decimal place of the average value is rounded off, and the values up to the first decimal place are the wave height and wavelength, respectively.

[Example 1]
For spinning of the hollow fiber membrane, a composite nozzle base capable of forming a three-layered hollow fiber membrane in which a groove for forming the inner ridge of the membrane was formed at one location on the inner peripheral portion was used.
The polymer B forming the inner layer and the outer layer support layer includes high-density polyethylene (trade name Suntech B161, manufactured by Asahi Kasei Chemicals Corporation, MFR 1.1 g / 10 min, density 0) manufactured using a Ziegler-Natta catalyst. 964 g / cm ³ , melting point 140 ° C.).
The polymer A forming the homogeneous layer includes a low density polyethylene (trade name Harmolex NF324A, manufactured by Nippon Polyethylene Co., Ltd., MFR 1.0 g / 10 min, density 0.906 g / cm ³ , melting point 120, produced using a metallocene catalyst. ° C.) Was used.
Spinning was performed at a discharge temperature of 190 ° C. and a winding speed of 140 m / min to obtain an unstretched hollow fiber membrane precursor. The inner diameter of the hollow fiber membrane precursor was 190 μm, and the three layers were arranged concentrically.
The hollow fiber membrane precursor was annealed at 108 ° C. for 8 hours. Next, the film is stretched 1.25 times at 23 ± 2 ° C., and subsequently stretched 3.6 times in a heating furnace at 105 ° C., and then becomes 0.6 times the constant length in a heating furnace at 115 ° C. In this relaxed state, heat setting was performed to obtain a degassing hollow fiber membrane with a final total draw ratio of 4 times.

The degassing hollow fiber membrane has a three-layer structure in which a homogeneous layer is sandwiched between two support layers, and is a hollow fiber membrane having a triangular inner cross-section as shown in FIG. It was. The height of the inner protrusion was 10 μm and the width was 10 μm.
When the air permeation rate of the obtained degassing hollow fiber membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.11 m / hour · MPa, and the nitrogen permeation rate (Q _N2 ) was is 0.033m / time · MPa, separation factor _(Q O2 _/ Q _N2) was 3.0. The separation factor by the film measurement of the polymer A used for the homogeneous layer was 3.0, and this value was maintained. A knitted fabric sheet in which both ends of the sheet were constrained by a warp yarn was produced by Russell knitting, and heat treatment was performed at 70 ° C. for 1 hour to develop crimps.
Using the crimped knitted fabric sheet, a hollow fiber membrane module for measurement was prepared at a filling rate of 40%, and the end of the hollow fiber membrane module was potted so that the relaxation rate was 3% compared to the crimped knitted fabric. Further, the end fixing potting resin was cut to open the end portion of the hollow fiber membrane to form a hollow fiber membrane module.
Furthermore, no leak occurred even when a butyl carbitol acetate (BCA) liquid used as a cleaning agent for solvent-based inks, etc. was fed under pressure at 0.5 MPa on the outer side of the obtained degassing hollow fiber membrane. .
Using the obtained degassing hollow fiber membrane, an external reflux-type degassing hollow fiber membrane module with an effective membrane length of 90 cm and a filling rate of 40% was prepared, and ultrapure water was poured outside the hollow fiber membrane to make it hollow The pressure loss of the yarn membrane module was measured. The pressure loss at the outflow part of the hollow fiber membrane module when the liquid feeding pressure was 100 kPa was 10 kPa.

[Example 2]
Film formation was performed using the same polymer as in the example except that the hollow fiber membrane as shown in FIG. 2 was formed so that 1/3 of the inner peripheral portion of the hollow fiber membrane was thick. The degassing hollow fiber membrane was a hollow fiber membrane having a three-layer structure in which a homogeneous layer was sandwiched between two support layers and having a cross-sectional shape as illustrated in FIG.
When the air permeation rate of the obtained degassing hollow fiber membrane was measured, the oxygen permeation rate (Q _O2 ) at room temperature (23 ± 2 ° C.) was 0.09 m / hour · MPa, and the nitrogen permeation rate (Q _N2 ) was is 0.030m / time · MPa, separation factor _(Q O2 _/ Q _N2) was 3.0. The separation factor by the film measurement of the polymer A used for the homogeneous layer was 3.0, and this value was maintained. A knitted fabric sheet in which both ends of the sheet were constrained by a warp yarn was produced by Russell knitting, and heat treatment was performed at 70 ° C. for 1 hour to develop crimps.
The wave height of the hollow fiber membrane at that time was 3 mm, and the wave wavelength was 30 mm.
Using the crimped knitted fabric sheet, a hollow fiber membrane module for measurement was prepared at a filling rate of 40%, and the end of the hollow fiber membrane module was potted so that the relaxation rate was 3% compared to the crimped knitted fabric. Further, the end fixing potting resin was cut to open the end portion of the hollow fiber membrane to form a hollow fiber membrane module.
Furthermore, no leak occurred even when a butyl carbitol acetate (BCA) liquid used as a cleaning agent for solvent-based inks, etc. was fed under pressure at 0.5 MPa on the outer side of the obtained degassing hollow fiber membrane. .
Using the obtained degassing hollow fiber membrane, an external reflux-type degassing hollow fiber membrane module with an effective membrane length of 90 cm and a filling rate of 40% was prepared, and ultrapure water was poured outside the hollow fiber membrane to make it hollow The pressure loss of the yarn membrane module was measured. The pressure loss at the outflow part of the hollow fiber membrane module when the liquid feeding pressure was 100 kPa was 10 kPa.

[Comparative Example 1]
A hollow fiber membrane for deaeration was obtained in the same manner as in Example 1 except that the inner protrusion was not formed. Using the obtained degassing hollow fiber membrane, an external reflux degassing hollow fiber membrane module was produced in the same manner as in Example 1, and the pressure loss was measured. The pressure at the outflow part of the hollow fiber membrane module when the liquid feeding pressure was 100 kPa was 70 kPa.

[Comparative Example 2]
A hollow fiber membrane for deaeration was obtained in the same manner as in Example 1 except that the inner protrusion was not formed. Using the obtained degassing hollow fiber membrane, a sheet was formed by raschel knitting to produce a degassing hollow fiber membrane module, and the pressure loss was measured by flowing the degassing target liquid through the hollow portion of the membrane. The pressure at the outflow part of the hollow fiber membrane module when the liquid feeding pressure was 100 kPa was 30 kPa.
When the oxygen permeation rate (Q _O2 ), nitrogen permeation rate (Q _N2 ), separation factor (Q _O2 / Q _N2 ), and pressure loss in the measurement of pressure loss of the degassing hollow fiber membrane obtained in each example were 100 kPa Table 1 shows the pressure at the outflow part of the hollow fiber membrane module.

DESCRIPTION OF SYMBOLS 1, 2 Hollow fiber membrane module for deaeration 10 Hollow fiber membrane for deaeration 12 Inner surface 14 Inner side protrusion 16 Outer surface 20 Housing case 22 Hollow fiber membrane bundle 24A, 24B Potting part

Claims (10)

  A hollow fiber membrane comprising a homogeneous layer having a non-porous structure and a support layer having a porous structure and supporting the homogeneous layer, wherein the homogeneous layer is 20 μm or less from the outer surface or outer surface of the hollow fiber membrane A hollow fiber membrane for deaeration, wherein the hollow fiber membrane for deaeration has an eccentric structure in which the position of the center of gravity is shifted from the center position of the cylindrical outer peripheral surface of the hollow fiber membrane. A hollow fiber membrane having a homogeneous layer having a non-porous structure and a support layer supporting a thin homogeneous membrane with a porous structure, wherein the homogeneous layer is disposed on the outermost layer of the hollow fiber membrane or an outer surface To 20 μm or less,
The inner surface appearing in the longitudinal cross section of the hollow fiber membrane is composed of a circular or elliptical peripheral surface and an internal ridge extending in the longitudinal direction that is unevenly distributed in a range of at least 1/3 or less of the circular or elliptical peripheral surface. Hollow fiber membrane for deaeration.   The hollow fiber membrane for deaeration according to claim 2, wherein the height of the inner ridge is 5 µm or more from the circumferential surface of the circle or ellipse. The hollow fiber membrane for deaeration according to claim 2 or 3, wherein the inner protrusion has a width of 5 µm or more.   The ratio of the projected area obtained by projecting the inner ridge on the inner surface of the film is such that the projected area obtained by projecting the inner ridge on the inner surface of the film is the area of the circular or elliptical peripheral surface on the inner surface of the film. On the other hand, it is 1 to 20%, The hollow fiber membrane for deaeration according to any one of claims 2 to 4.   The hollow fiber membrane for deaeration according to any one of claims 1 to 5, wherein the innermost layer is a homogeneous layer having a non-porous structure.   When the supporting layer and the homogeneous layer are made of a polymer, and the melting point of the polymer constituting the supporting layer and the homogeneous layer, which is not higher among the melting points, is Tm (° C.), the melting point constituting the other layer is Tm ( The hollow fiber membrane for deaeration according to any one of claims 1 to 6, which is not lower than (° C) and not higher than (Tm + 60) (° C).   The hollow fiber membrane for deaeration according to any one of claims 1 to 7, which has a latent crimping property that causes crimping by heating.   A hollow formed of a housing case and a plurality of degassing hollow fiber membranes according to any one of claims 1 to 8, which are fixed so that the inner side and the outer side of the membrane are isolated in the housing case. A hollow fiber membrane module for deaeration having a yarn membrane bundle. The hollow fiber membrane module for degassing according to claim 8, wherein a filling rate of the hollow fiber membrane is 40 to 55%.