JPH06339617A - Hollow fiber composite membrane and its preparation - Google Patents

Abstract

PURPOSE:To enlarge gas permeation characteristics and to attempt to improve membrane characteristics by placing a plurality of hollow separation membranes with separation function therein along the longitudinal direction of a fibrous body consisting of a porous layer with reinforcing function and laminating a porous layer with reinforcing function on the inner surface of a separation membrane. CONSTITUTION:A plurality of hollow separation membranes B with separation function therein along the longitudinal direction of a fibrous body consisting of a porous layer A with reinforcing function exist and a porous layer C with reinforcing function is laminated on the inner surface of a separation membrane. Gas permeation characteristics is made thereby about 3.8 times larger than the conventional composite membrane even when the outer diameters and the fine pore structures of the porous layers A and C and the thickness of the separation membrane B are the same as those for the conventional composite membrane and the membrane characteristics can be improved by increase in the membrane area of the separation membrane B. In addition, it is possible to miniaturize furthermore various membrane modules wherein the conventional composite membranes are used by using this multifilament type hollow fiber composite membrane.

Description

Detailed Description of the Invention

[0001]

The present invention relates to gas separation, solvent separation,
The present invention relates to a high-performance multifilament hollow fiber composite membrane used for deaeration and the like.

[0002]

2. Description of the Related Art Many techniques for separating and refining substances have been developed and improved since ancient times. Membrane separation technology is one of them, but looking at the progress of its improvement, the development of excellent membrane materials and the development of thin film technology to improve the separation efficiency were the major technological development flows.

As one of thinning techniques, a method of forming a thin film on a porous base material by a coating method or a vapor deposition method is widely used. However, in order to coat on a porous base material, It was difficult to obtain a substantial thin film because the thin film material entered the pores of the base material. As a solution to this drawback,
There is a method of previously filling the pores of the porous substrate with a soluble substance to form a thin film layer on the surface and then eluting the soluble substance in the porous substrate.

However, even in this method, it is difficult to obtain a uniform thin film layer, the thin film layer is easily damaged during the elution process, and the thin film layer is easily peeled off from the obtained composite film. There was a problem.

A multilayer composite membrane hollow fiber membrane disclosed in Japanese Patent Publication No. 3-44811 is known as a membrane structure which can be industrially produced by thinning a separation membrane. The membrane structure of these composite membranes is, as shown in FIG. 3, a hollow separation membrane having a separation function in which a porous layer (A) having a reinforcing function is laminated on the inner surface thereof. The structure has only one (B).

[0006]

However, as is apparent from FIG. 3, the membrane structure of these composite membranes has a reinforcing function in the case where the hollow separation membrane (B) having the separation function is the hollow fiber composite membrane. There was only one in the porous layer (A).

Permeation speed is one of the performance indexes as a multilayer composite separation membrane, but if the membrane materials are the same, in order to increase the permeation speed, the separation membrane (B) is made thinner and It is important to increase the effective membrane area of the separation membrane (B). Furthermore, it is important to set the pore diameter, porosity, and film thickness of the porous layers (A) and (C) so that they do not become a resistance to permeation.

As the separation membrane (B) is made thinner, the rate of occurrence of membrane defects increases, so there is a limit to thinning. Therefore, increasing the effective membrane area of the separation membrane (B) is a very effective means.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a hollow separation membrane (B) having a separation function inside along the longitudinal direction of a fibrous object comprising a porous layer (A) having a reinforcing function. )
In the multifilament type hollow fibrous composite membrane in which a plurality of layers are present and the porous layer (C) having a reinforcing function is laminated on the inner surface of the separation membrane (B).

Further, a nozzle for distributing the fluid in the hollow portion, a nozzle for distributing the reinforcing layer polymer (A '), a nozzle for distributing the separation membrane polymer (B'), and the reinforcing layer polymer (C ').
Using a spinning nozzle in combination with a nozzle for distributing, the reinforcing layer polymer (A ') and the reinforcing layer polymer (C') are composite-spun in a form of sandwiching the separation membrane polymer (B ') and stretched. By making at least the reinforcing layer polymer (A ') and the reinforcing layer polymer (C') part porous by the porous layer (C), the inner surface and the outer surface of the hollow fibrous composite membrane have a reinforcing function. And a method for producing a multifilament type hollow fiber composite membrane having a structure comprising a porous layer (A) having a reinforcing function.

The multifilament type hollow fiber composite membrane of the present invention will be described below with reference to the drawings. Figure 1
2 and 2 show examples of sectional views of the composite membrane of the present invention. This shows a membrane structure in which a plurality of separation membranes (B) having a separation function in which a porous layer (C) having a reinforcement function is laminated on the inner surface are present inside the porous layer (A) having a reinforcement function.

The composite membrane of the present invention has at least a three-layer structure when viewed as each separation membrane (B). Basically, the separation membrane (B) is sufficient in one layer, but may have a multilayer structure of two or more layers depending on the purpose.

In the separation, the layer having the separating function is the most important, and if the separation membrane (B) is on the surface layer, the surface of the separation membrane may be damaged during handling, but the composite of the present invention is used. The membrane does not have such a danger because the separation membrane (B) is covered with the porous layer.

The membrane performance of the composite membrane of the present invention depends on the porous layer (A).
If the porosity and average pore diameter of the porous layer (C) are the same and the thickness is about several hundreds of microns or less, it is determined by the thickness and the membrane area of the separation membrane (B) present in the porous layer. It

Therefore, by thinning the separation membrane (B) and increasing the number of existing separation membranes (B), the membrane area is increased and the membrane performance is improved. The method for reducing the thickness of the separation membrane (B) has a limit depending on the manufacturing method or the material.

Moreover, the risk of occurrence of film defects increases as the film becomes thinner. Therefore, when the thinning becomes close to the limit or the risk of the occurrence of membrane defects is reduced and the membrane performance is enhanced, the membrane area of the separation membrane (B) present in the porous membrane is increased. Is effective.

In order to increase the membrane area of the separation membrane (B), conventionally, when observed in its cross section, one composite membrane has one hollow separation membrane as shown in FIG. However, the composite membrane of the present invention has a form in which a plurality of hollow separation membranes are present in one composite membrane as shown in FIG. 1 or 2.

The form in which a plurality of hollow separation membranes are present in the present invention is such that the separation membrane has at least the same or more membrane area as compared with the case of a single hollow membrane form as shown in FIG. It means having multiple B). The sizes of the plurality of separation membranes (B) may not be the same, but it is preferable that they are the same.

According to the present invention, a plurality of hollow separation membranes (B) having a separation function are present inside the fibrous object comprising the porous layer (A) having a reinforcement function, and the separation membrane ( The porous layer (C) having a reinforcing function is laminated on the inner surface of B) means that the porous layer (A) and the separation membrane (B), and the separation membrane (B) and the porous layer (C). It means that there is no special void between them.

The separation membrane (B) is a portion having a separation function and is preferably as thin as possible in order to maintain a high transmission rate. Therefore, the thickness of this separation membrane (B) is 2μ.
If it exceeds m, the meaning of thinning is diminished.

On the other hand, the lower limit of the thickness of the separation membrane (B) is not particularly limited, but it is preferably about 0.005 μm or more, and more preferably 0.01 μm or more.

The position range in which a plurality of separation membranes (B) are present in the porous layer is smaller than the outer surface of the porous layer (A) in order to protect the separation membrane (B) from external damages such as handling. 5 μm
The inner side is preferable, and the inner side is more preferably 2 μm or more. The cross-sectional shape of the separation membrane (B) may be any shape such as rectangular or corrugated, but a circular shape is more preferable in consideration of maintaining high strength and processing.

The separation membranes (B) may come into contact with each other, but in order to effectively use their functions, it is preferably 0.06 times or more the outer diameter of the separation membrane (B). The porous layer (A) and the porous layer (C) having a reinforcing function, in addition to being responsible for reinforcement and protection, exert an effect of preventing the occurrence of a membrane defect when the separation membrane (B) is thinned.

In the composite membrane of the present invention, when the separation membrane (B) is thinned, the thinner the separation membrane (B) is,
It is important to control the pore size of the porous layers (A) and (C),
If the control is not performed properly, defects are likely to occur in the separation film (B).

Therefore, the separation function of the separation membrane (B) can be sufficiently exhibited without the occurrence of membrane defects, and the separation membrane (B) can be obtained.
The preferable porous structure of the porous layers (A) and (C) such that the above does not resist the separation function, the average pore diameter is 0.005 to 0.5 μm, preferably 0.01 to 0.3.
μm, porosity 20 to 90%, preferably 30 to 70%,
The outer diameter of the composite membrane is 10 to 1000 μm.

The thickness of the porous layer (C) is preferably 0.01 times or more the outer diameter of the separation membrane (B), more preferably 0.06 times or more. When the pore diameter is 0.005 μm, the permeation resistance of the substance to be separated increases, and when it exceeds 0.5 μm, it tends to cause defects in the separation membrane (B). 20% porosity
When the ratio is less than the above, the ratio of the separation membrane (B) facing the openings of the pores of the porous layers (A) and (C) is too small, and the effective utilization rate of the separation membrane (B) is significantly reduced. It becomes difficult to reinforce and hold the composite membrane of the present invention.

When the outer diameter of the composite membrane of the present invention is less than 10 μm, it is difficult to handle and the strength tends to be insufficient. In order to increase the membrane area of a plurality of separation membranes (B) present in the porous layer, it is advantageous that the outer diameter of the composite membrane is large.
If it exceeds 000 μm, the resistance of the substance to be separated in the porous layer becomes too large, and the separation function of the separation membrane (B) at the center of the composite membrane is likely to deteriorate.

The diameter of the hollow portion in the porous layer may be 1 μm or more, preferably 10 μm or more. If the diameter of the hollow portion is less than 1 μm, the permeation resistance of the substance to be separated increases and the separation function is likely to deteriorate.

The method for producing the composite membrane of the present invention is described below. A nozzle for distributing the fluid in the hollow portion, a nozzle for distributing the polymer for reinforcing layer (A '), a nozzle for distributing the polymer for separating membrane (B') and a nozzle for distributing the polymer for reinforcing layer (C ') were combined. Melt shaping temperature of 15 with spinning nozzle
A plurality of separation membrane polymers (B ') are sandwiched between the reinforcing layer polymers (A') and (C ') in the range of 0 to 300 ° C to form a plurality of hollow composite membranes, and further each composite membrane is formed. After being joined and integrated with the reinforcing layer polymer (A ') of the outer layer,
Spinning is performed in a draft ratio range of 5 to 9000.

The melt-formed composite film precursor is annealed as necessary and then stretched to form a porous layer (A).
The portions of the reinforcing layer polymers (A ') and (C') used in (C) and (C) are made porous.

As a method for stretching and porosifying, a known method used for polyolefin can be adopted. That is, the reinforcing layer polymers (A ') and (C') used for the porous layers (A) and (C) are caused to whiten by microcracking by a small amount of stretching at around room temperature, and then, by heat stretching. It is possible to enlarge the holes and stabilize the hole shape.

During this period, the separation membrane polymer (B ') used for the separation membrane (B) is not made porous, and thus becomes thin as the draw ratio increases. The stretching conditions are not particularly limited, and the optimum conditions can be set depending on the types of the reinforcing layer polymers (A ') and (C') and the separation membrane polymer (B '). For example, the porous layer (A) When polyethylene is used for the reinforcing layer polymers (A ′) and (C ′) used in (C) and (C), the cold stretching conditions are 40 to 200% at room temperature and the hot stretching conditions are 80 to 125 ° C. Preferably, the conditions are such that the total draw ratio is about 100 to 300% at 90 to 105 ° C. To further improve the thermal stability, a constant length or relaxation heat treatment may be performed at 80 to 125 ° C, preferably 105 to 120 ° C.

In the composite membrane of the present invention, the separation membrane polymer (B ') used for the separation membrane (B) is silicone rubber, a silicone-based polymer such as a copolymer of silicone and polycarbonate, or poly-4-methylpentene. -1, polyolefin polymers such as linear low-density polyethylene, perfluoroalkyl fluorine-containing polymers, polyurethane polymers, polyphenylene oxide, poly-4-vinylpyridine, and copolymers of the monomers constituting these polymers , And copolymers of the monomers constituting these polymers,
And mixtures thereof.

As the reinforcing layer polymers (A ') and (C') used in the porous layers (A) and (C), any polymer can be used as long as it is a material that can be made porous by a stretching operation. May be polyethylene, polypropylene, poly 4-
Crystalline polymers such as polyolefins such as methylpentene-1 and halogen-containing polyolefins such as polyvinylidene fluoride and tetrafluoroethylene are preferred.

[0035]

The present invention will be described in detail with reference to the following examples. The "average pore diameter" was measured with a mercury porosimeter, and the pore diameter when the pore volume was 1/2 was taken as the average pore diameter from the relationship between the pore diameter and the pore volume. The “thickness of the intermediate layer” was measured by electron microscope observation.

Example 1 Five hollow separation membranes (B) having a separation function were formed inside along the longitudinal direction of a fibrous object composed of a porous layer (A) having a reinforcement function to form a separation membrane. Using a multi-membrane manufacturing nozzle arranged so as to form a shape in which a porous layer (C) having a reinforcing function is laminated on the inner surface of (B), the porous layers (A) and (C) are High density polyethylene (Hisex 2200J, manufactured by Mitsui Petrochemical Co., Ltd.) with a density of 0.968 g / cc and a melt index value of 5.5 is supplied as a polymer material to the separation membrane (B) segment. Polyurethane (TECOFLEX EG-80A, manufactured by Thermedeck Co., Ltd.) was used, and melt spinning was performed at a discharge temperature of 165 ° C. and a winding speed of 205 m / min.

The obtained unstretched fiber has a film form as shown in FIG. 2, and has a structure in which five hollow segmented polyurethanes having an inner surface laminated with polyethylene are formed inside a cylindrical polyethylene. , Outer diameter 300 μm, film thickness 3 μ of the porous layer (C) laminated on the inner surface of the separation membrane (B)
m, the minimum distance between adjacent separation membranes (B) was 3 μm, the thickness of the separation membrane (B) was 1 μm, and the inner diameter of the hollow portion was 41.7 μm.

This unstretched fiber was annealed at 115 ° C. for 1 hour. Next, the annealed fiber is heated at room temperature for 14
0% cold drawing is performed, and then hot drawing is performed in a heating furnace heated to 105 ° C. until the total draw ratio becomes 170%,
Furthermore, the total draw ratio is 1 in a heating furnace heated at 120 ° C.
Relaxation heat setting was performed so that it would be 00%.

As a result of evaluating the membrane performance of the obtained composite membrane,
Porosity 40.2%, average pore diameter 0.155 μm, outer diameter 2
60 μm, thickness of the porous layer (C) laminated on the inner surface of the separation membrane (B) 2.8 μm, minimum distance between adjacent separation membranes (B) 2.8 μm, thickness of the separation membrane (B) Is 0.7 μm,
The inner diameter of the hollow portion was 39.3 μm.

When the air permeation rate of the obtained composite membrane was measured, the oxygen permeation rate (QO ₂ ) at room temperature was 8.65 × 1.
0 ⁻⁶ cm ³ / cm ² · sec · cmHg, nitrogen permeation rate (QN ₂ ) is 3.2 × 10 ⁻⁶ cm ³ / cm ² · sec ·
cmHg, and the separation factor (QO ₂ / QN ₂ ) is 2.7.
Met.

Example 2 19 hollow separation membranes (B) each having a separation function were formed inside the fibrous substance comprising the porous layer (A) having a reinforcement function in the longitudinal direction. Using a nozzle arranged so as to form a shape in which a porous layer (C) having a reinforcing function is laminated on the inner surface of (B), the same polymer as in Example 1 is used, and spinning is performed under the same spinning conditions. did.

The obtained unstretched fiber has a membrane form as shown in FIG. 1, the outer diameter is 300 μm, the thickness of the porous layer (C) laminated on the inner surface of the separation membrane (B) is 3 μm, The thickness of the separation membrane (B) was 1 μm, and the inner diameter of the hollow portion was 41.7 μm.

The unstretched fiber was annealed, cold-stretched, hot-stretched and relaxation heat-set in the same manner as in Example 1 to evaluate the membrane performance. As a result of evaluating the obtained composite film, the porosity was 40.
2%, average pore diameter 0.155 μm, outer diameter 260 μm, film thickness 2.8 μm of porous layer (C) laminated on inner surface of separation membrane (B), minimum distance 2 between adjacent separation membranes (B) .8
μm, the thickness of the separation membrane (B) was 0.7 μm, and the inner diameter of the hollow portion was 39.3 μm.

When the air permeation rate of the obtained composite membrane was measured, the oxygen permeation rate (QO ₂ ) at room temperature was 3.29 × 1.
0 ^-5 cm ³ / cm ² · sec · cmHg, nitrogen permeation rate (QN ₂ ) is 1.22 × 10 ^-5 cm ³ / cm ² · sec
CmHg, and the separation factor (QO ₂ / QN ₂ ) is 2.
It was 7.

Comparative Example 1 A hollow separation membrane (B) having a separating function inside was formed as a porous layer (A) along the longitudinal direction of a fibrous object composed of a porous layer (A) having a reinforcing function. An example using a composite membrane manufacturing nozzle arranged so as to form a single concentric circle and a porous layer (C) having a reinforcing function laminated on the inner surface of a separation membrane (B) was used. The same polymer as in 1 was used and spun under the same spinning conditions. The resulting undrawn fiber has an outer diameter of 30.
The thickness of the porous layer (C) laminated on the inner surface of the separation membrane (B) was 17.5 μm, the thickness of the separation membrane (B) was 1 μm, and the inner diameter of the hollow portion was 230 μm.

The unstretched fiber was annealed, cold-stretched, hot-stretched and relaxation heat-set in the same manner as in Example 1 to evaluate the membrane performance. As a result of evaluating the obtained composite film, the porosity was 40.
2%, average pore diameter 0.155 μm, outer diameter 260 μm, film thickness 1 of porous layer (C) laminated on inner surface of separation membrane (B)
15 μm, the thickness of the separation membrane (B) was 0.7 μm, and the inner diameter of the hollow portion was 200 μm.

When the air permeation performance of the obtained composite membrane was measured, the oxygen permeation rate (QO ₂ ) at room temperature was 8.65 ×.
10 ⁻⁶ cm ³ / cm ² · sec · cmHg, nitrogen permeation rate (QN ₂ ) is 3.20 × 10 ⁻⁶ cm ³ / cm ² · se
c · cmHg, and the separation factor (QO ₂ / QN ₂ ) was 2.7.

[0048]

As is apparent from the examples, the multifilament type hollow fibrous composite membrane of the present invention has a plurality of hollow separation membranes (B) in the porous layer (A), and thus is porous. Even though the pore structure and outer diameter of the quality layers (A) and (C) and the thickness of the separation membrane (B) are the same as those of the conventional composite membrane, the gas permeation performance is increased by about 3.8 times. Separation membrane (B)
The membrane performance is improved due to the increase in the membrane area of the membrane. Further, by using the multifilament type hollow fiber composite membrane of the present invention, it becomes possible to further miniaturize various membrane modules using the conventional composite membrane.

[Brief description of drawings]

[Figure 1]

FIG. 2 is a schematic diagram of a composite membrane of the present invention in which a plurality of hollow separation membranes (B) having a porous layer (C) laminated on the inner surface along the longitudinal direction thereof are present in the porous layer (A). FIG.

FIG. 3 is a schematic cross-sectional view of a conventional composite film.

[Explanation of symbols]

 A porous layer B separation membrane C porous layer

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The separation membranes (B) may be brought into contact with each other, but the separation membranes adjacent to each other in order to effectively use their functions.
The distance between (B) is preferably 2 μm or more . The porous layer (A) and the porous layer (C) having a reinforcing function, in addition to being responsible for reinforcement and protection, exert an effect of preventing the occurrence of a membrane defect when the separation membrane (B) is thinned.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

The method for producing the composite membrane of the present invention is described below. A nozzle for distributing the fluid in the hollow portion, a nozzle for distributing the polymer for reinforcing layer (A '), a nozzle for distributing the polymer for separating membrane (B') and a nozzle for distributing the polymer for reinforcing layer (C ') were combined. Melt shaping temperature of 15 with spinning nozzle
In the range of 0 to 300 ° C., a plurality of separation membrane polymers (B ′) are sandwiched between the reinforcing layer polymers (A ′) and (C ′) to form a hollow composite membrane, and each composite membrane is further formed. Are joined and integrated by the reinforcing layer polymer (A ') of the outer layer , and then spun in a draft ratio of 5 to 9000.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

The obtained unstretched fiber has a membrane form as shown in FIG. 1, the outer diameter is 300 μm, the thickness of the porous layer (C) laminated on the inner surface of the separation membrane (B) is 3 μm, Adjacent
The minimum distance between the separation membranes (B) was 3 μm, the thickness of the separation membrane (B) was 1 μm, and the inner diameter of the hollow portion was 41.7 μm.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

The unstretched fiber was annealed, cold-stretched, hot-stretched and relaxation heat-set in the same manner as in Example 1 to evaluate the membrane performance. As a result of evaluating the obtained composite film, the porosity was 40.
2%, average pore diameter 0.155 μm outer diameter 260 μm, film thickness 15 of the porous layer (C) laminated on the inner surface of the separation membrane (B) 15
μm, thickness of separation membrane (B) 0.7 μm, inner diameter of hollow part is 2
It was 00 μm.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Okamoto 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. A plurality of hollow separation membranes (B) having a separation function are present inside a fibrous object composed of a porous layer (A) having a reinforcement function, and the separation membrane (B (3) A multifilament type hollow fibrous composite membrane, wherein a porous layer (C) having a reinforcing function is laminated on the inner surface of (1). 2. A nozzle for distributing a fluid in a hollow portion, a nozzle for distributing a polymer for reinforcing layer (A '), a nozzle for distributing a polymer for separating membrane (B'), and a polymer for reinforcing layer (C ').
Using a spinning nozzle in combination with a nozzle for distributing, the reinforcing layer polymer (A ') and the reinforcing layer polymer (C') are composite-spun in a form of sandwiching the separation membrane polymer (B ') and stretched. At least the reinforcing layer polymer (A ') and the reinforcing layer polymer (C') are made porous by the above method, and
A method for producing a multifilament type hollow fibrous composite membrane, which comprises producing the described composite membrane.