JPH03202131A - Preparation of hollow yarn membrane and cylindrical article used therein - Google Patents

Abstract

PURPOSE:To form a hollow yarn membrane with a high void ratio provided with pores having a mean pore size of about 0.02-2mum by a method wherein the yarn spun from a spinning nozzle is passed through a gaseous atmosphere containing the non-solvent mist from a coagulation bath before introduced into the coagulation bath. CONSTITUTION:The gaseous atmosphere between a tube-in-orifice type spinning nozzle spinning a film forming polymer raw solution and a core liquid for forming a hollow part and a coagulation bath composed of a non-solvent of a polymer or a liquid mixture of the non-solvent and solvent is shielded from the open air. At the same time, by controlling the temp. of the internal gaseous atmosphere so as to make the same lower than the temp. of the coagulation bath, mist composed of the non-solvent in the coagulation bath is generated in the internal gaseous atmosphere. The yarn spun from the spinning nozzle is passed through the mist-containing gaseous atmosphere and subsequently introduced into the coagulation bath to be coagulated to prepare a hollow yarn membrane.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a novel hollow fiber membrane, and more specifically, it relates to a method for producing a novel hollow fiber membrane, and more specifically, a method for producing a hollow fiber membrane, in which the diameter of the membrane pores on the outer surface can be increased and the porosity can be increased. The present invention relates to a method for easily producing a hollow fiber membrane and a cylindrical article used therein.

[Prior Art] Membrane separation technology has attracted attention for its energy saving and compactness, and has made remarkable progress. Many types of polymers have been researched and developed as membrane materials for selective separation membranes used in such membrane separation systems, and cellulose-based, polyamide-based, polyacrylonitrile-based, polysulfone-based polymers, etc. have been used. Furthermore, typical forms of separation membranes include flat membranes, tube membranes, and hollow fiber membranes. Semipermeable membrane modules obtained by further processing these various types of separation membranes are the heart of reverse osmosis, ultrafiltration, and precision filtration devices, and various types are used depending on the purpose. One of them, the hollow fiber membrane module, is widely used in various fields because of its compactness and small brimming volume.

Hollow fiber membranes are manufactured using the phase inversion method, which generally consists of a solution of the polymer that makes up the membrane. RL and a core liquid for forming a hollow part are simultaneously spun out from a tube-in-orifice type spinning nozzle, and the spun yarn is coagulated with a non-solvent of the polymer or a mixture of a non-solvent and a solvent. The method is to introduce it into a bath and gel it.

In the so-called mixed method, in which the spinning nozzle is immersed in a coagulation bath and the membrane-forming stock solution is spun directly from the nozzle into the coagulation bath, the outer surface of the hollow fiber membrane has a dense structure, making it difficult to perform external pressure filtration. You will find something suitable for your use.

In addition, a spinning nozzle is installed at the top a certain distance from the coagulation bath, and the yarn spun from the nozzle is passed through a gas atmosphere and then guided to the coagulation bath to form a film, the so-called wet-dry method. In this method, the outer surface tends to have a relatively porous structure, and it is advantageous in terms of water permeability to make the outer membrane structure porous, such as the inner skin type hollow fiber membrane used for internal pressure filtration. In some cases, this spinning method is adopted.

When spinning by the wet-dry method, the porous structure on the outer surface is easily affected by conditions such as the temperature and humidity of the gas atmosphere passing through, and it is known that the pore size on the outer surface becomes particularly large when the humidity is high. . For example, JP-A No. 59-228017 discloses that a polysulfone hollow fiber membrane having substantially pores of 0.02 to 2 μm on its outer surface can be obtained by passing it through air at a predetermined humidity. There is.

Furthermore, Japanese Patent Application Laid-open No. 1-49911 discloses that by contacting polysulfone with a non-solvent vapor having a vapor pressure 15 mm 1 g or more higher than the vapor pressure at the temperature of the stock solution and then immersing it in water, the outer surface is substantially coated. 0. O1~0.5μm
It is disclosed that a hollow fiber membrane having micropores of .

[Problem to be solved by the invention] The above-mentioned Japanese Patent Laid-Open No. 59-228017 and Japanese Patent Laid-Open No. 82
All of the methods disclosed in Publication No. 49911 utilize the effect of absorbing non-solvent vapor in the air into the spun yarn before entering the coagulation bath, and use hollow fiber membranes with large pores on the outer surface. It is an advantageous method for manufacturing.

However, the time it takes for spun yarn to pass through the air is generally only a few seconds at most, and the amount of non-solvent vapor that can exist in the air is limited to a very small amount. Even if the yarn is saturated with solvent vapor, the amount of non-solvent absorbed by the spun yarn is insufficient, so the pore size on the outer surface cannot be increased in many cases. Therefore, the present invention overcomes the drawbacks of the conventional hollow fiber membrane manufacturing method described above, easily and at low cost, has micropores with an average pore diameter of 0.02 to 2 μm on the outer surface, and has a porosity of An object of the present invention is to provide a method for manufacturing a hollow fiber membrane with high performance.

[Means for Solving the Problems] As a result of intensive research into means for increasing the amount of non-solvent absorbed by the spun yarn, the present inventors discovered that □ A mist of non-solvent was introduced into the gas atmosphere. If it is included, in addition to a saturated amount of non-solvent vapor, there will be >& non-solvent in the form of a mist in the gas atmosphere, so the amount of non-solvent absorbed by the spun yarn will increase. The inventors have discovered that it is possible to easily produce a hollow fiber membrane with a highly porous outer surface and a dramatic increase in the amount of porosity, and have completed the present invention.

That is, the present invention provides a tube-in-orifice type spinning nozzle for spinning a membrane-forming raw wave consisting of a solution of a polymer constituting a membrane and a core liquid for forming a hollow part, and a non-solvent or non-solvent for the polymer. By shielding the gas atmosphere between the coagulation bath consisting of a solvent and a mixture of solvents from the outside air and controlling the temperature of the internal gas atmosphere to be lower than that of the coagulation bath, the internal gas atmosphere consists of the non-solvent in the coagulation bath. A method for producing a hollow fiber membrane, characterized by generating a mist, passing the thread spun from a spinning nozzle through a gas atmosphere containing the mist, and then guiding it to a coagulation bath to gel it; Furthermore, it is a cylindrical object installed between the spinning nozzle and the coagulation bath, which is equipped with a cooling jacket having at least an inlet and an outlet for the yarn spun from the spinning nozzle and an outlet and outlet for the coolant, and the coolant is caused to flow through the jacket. This relates to a cylindrical object used in the production of hollow fiber membranes that generates a mist consisting of the non-solvent in the coagulation bath in the internal gas atmosphere by controlling the temperature of the internal gas atmosphere to be lower than that of the coagulation bath. be.

In the present invention, the polymer constituting the membrane may be any polymer that can be formed into a film by a phase separation method, such as cellulose, polyamide, polyacrylonitrile, or polysulfone. It is desirable to use polysulfone polymers because they have excellent chemical resistance.

The film-forming stock solution is prepared by dissolving the above polymer in a suitable solvent. As the solvent, a good solvent for the polymer to be used can be appropriately selected and used, but it is necessary to select a solvent that is compatible with the coagulation liquid used in the coagulation bath, and preferably one that can be mixed in an arbitrary ratio. Further, the good solvent may be used alone or in an appropriate mixture, and a non-solvent for the polymer or commonly used additives may be mixed as long as the solubility of the good solvent is not extremely impaired. The content of the polymer in the membrane-forming stock solution greatly affects the structure of the hollow fiber membrane, but it is usually prepared at 10 to 30% by weight.

The core liquid is a fluid for forming a hollow part during spinning of a hollow fiber membrane, and a gas or liquid is used. Although it is known that the structure of the inner surface of a hollow fiber membrane is greatly affected by the liquid used as the core liquid, there is no restriction at all as to what to use as the core liquid in the present invention.

The coagulation bath may be any non-solvent for the polymer used, and is not particularly limited, but from the viewpoint of ease of handling and cost, water is preferably used industrially. Further, a solvent or commonly used additives may be mixed with the non-solvent to the extent that the non-solvent exhibits coagulation ability.

A gaseous atmosphere containing a mist made of a polymer nonsolvent is one in which the nonsolvent vapor of the polymer used is supersaturated, and both the gaseous nonsolvent vapor and the mist made of microscopic droplets of the nonsolvent are present in the gaseous atmosphere. means the state of being. The gas in the gas atmosphere can be appropriately selected from gases that are inert to the membrane forming stock solution and the coagulation bath, but air is particularly preferred from the viewpoint of ease of handling and cost.

The non-solvent in the gas atmosphere can be appropriately selected from the non-solvents of the polymers used, and can be used alone or in combination; however, in that the desired gas atmosphere can be generated by a simple method as described below, It is desirable that it be the same as the non-solvent in the coagulation bath. Furthermore, it is desirable that both the nonsolvent in the gas atmosphere and the nonsolvent in the coagulation bath be water.

The generation of a gas atmosphere containing a mist made of a non-solvent in the coagulation bath is achieved by shielding the gas atmosphere between the spinning nozzle and the coagulation bath from the outside air, and by controlling the temperature inside the coagulation bath to be lower than that of the coagulation bath. A simple method is to cool non-solvent vapor from a coagulation bath and generate a mist made of the non-solvent.

Specifically, between the spinning nozzle and the coagulation bath, a cylindrical body equipped with a cooling jacket having at least an inlet and an outlet for the yarn spun from the spinning nozzle and an outlet and outlet for the coolant is installed;
A preferred method is to flow a constant temperature refrigerant through the jacket to control the temperature of the internal gas atmosphere to be lower than that of the coagulation bath. The double back method is usually used for jackets,
A coil method may also be used. The refrigerants that flow through the jacket include water, brine, ethylene glycol, nitrogen,
Any liquid or gas such as air, ammonia, or freon may be used, but constant temperature water is conveniently used.

This method is excellent in that not only can the amount of mist generated be controlled by the temperature of the gas atmosphere, but also that sufficient nonsolvent is always supplied to the film-forming raw solution because the gas inside the cylinder is convected.

In addition, reducing the pressure inside the cylindrical object and forcibly drawing in the non-solvent vapor in the coagulation bath into the internal gas atmosphere increases the amount of mist generated and increases the amount of mist that is spun out. The chances of contact with other people also increase, which is favorable.

Moreover, further feeding non-solvent vapor into the gas atmosphere inside the cylindrical object further increases the concentration of the mist made of the non-solvent, and is an effective means for the present invention.

It should be noted that using transparent plastic as the material for the cylindrical object is advantageous in that it is possible to observe the inside of the cylindrical object, and if the structure of the cylindrical object can be divided vertically, it will be easier to maintain. It's advantageous.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

In addition, the pure water permeation performance in Examples and Comparative Examples is shown as a value based on the inner surface of the hollow fiber membrane.

Example 1 20% by weight of polyether sulfone (Pictrex P ES 5200P powder manufactured by ICI Corporation),
A film-forming stock solution containing 30% by weight of triethylene glycol and 50% by weight of dimethyl sulfoxide was prepared. Using the manufacturing apparatus shown in the schematic diagram of FIG.
Spun from a tube-in-orifice type spinning nozzle with a core liquid consisting of a mixture of 0% by weight and 50% by weight of dimethyl sulfoxide,
The spun yarn was passed through a tube and then introduced into a coagulation bath using water to coagulate it, thereby obtaining a hollow fiber membrane. The cylinder used was
The shape is shown in Figure 2, the height of the cylinder is 21 (7), the inner diameter is 8clTl, and the entrance of the spun yarn is 2cn in diameter.
The + hole is open.

The upper opening of the tube was in close contact with the bottom of the spinning nozzle, and the lower opening was immersed in the coagulation bath from the liquid level to 1c+n, and the tube was installed so that the yarn passed through the center axis of the tube.

The film-forming stock solution, core solution, and coagulation bath were controlled at 60°C, and constant temperature water at 30°C was flowed through the jacket of the cylinder.

At this time, water mist was observed to be generated in the gas atmosphere inside the cylinder.

Under the above spinning conditions, a hollow fiber membrane with an inner diameter of 0.5 mm and an outer diameter of 0.8 mm was wound at a speed of 10 m/min.

When the membrane performance of this hollow fiber membrane was evaluated, the pure water permeation performance was 700j)/rd-hr-atm, and the myoglobin rejection rate was 95%.

Figures 3 and 4 are enlarged scanning electron microscope photographs of the inner and outer surfaces of this hollow fiber membrane (magnification to, 0).
00). The inner surface is highly dense and extremely smooth, with no micropores observed. On the other hand, the outer surface has 0.1 to 0
．． It can be seen that there are a large number of 5 μm micropores.

Comparative Example 1 Water at 60°C is poured into the jacket of the cylinder to lower the temperature inside the cylinder to 60°C.
Spinning was carried out in the same manner as in Example 1 except that the temperature was changed to .degree.

Although the humidity inside the cylinder was 10 (1%), no mist generation was observed.

The myoglobin exclusion rate of the obtained hollow fiber membrane was 95%, which was the same as that of the hollow fiber membrane of Example 1, but the pure water permeation performance was low, at 300 iJ/d.hr.atm.

Figures 5 and 6 are enlarged photographs (magnification: 10,000) of the inner and outer surfaces of this hollow fiber membrane, respectively. The inner surface shows no difference from Example 1, but the outer surface clearly has a lower porosity than Example 1, with a porosity of 0. Only a few micropores of i 34 to 0.5 μM were observed.

Example 2 In the manufacturing apparatus shown in FIG. 1, a gap of about 1c+n was provided between the lower opening of the cylinder and the liquid level of the coagulation bath, and an opening with an inner diameter of 1cn+ for pressure reduction was provided at the upper part of the cylinder. The spinning was carried out in the same manner as in Example 1, except that suction was carried out using an aspirator at a linear speed of 10(7)7 seconds. When the membrane performance of this hollow fiber membrane was evaluated, the pure water permeability was 900jl/rd・h.
The elimination rate of r◆atm'q myoglobin was 80%.

Figure 7 is an enlarged photograph of the outer surface of this hollow fiber membrane (magnification: 1.0
．． 000), it was observed that a large number of micropores of 0.1 to 0.5 μm were formed.

Example 3 In the manufacturing apparatus shown in Fig. 1, a pipe for supplying water vapor is provided at the bottom of the cylinder so that the outlet hole faces the liquid level of the coagulation bath to supply water vapor, and an exhaust port is installed at the top of the cylinder. Spinning was carried out in the same manner as in Example 1, except that .

The pure water permeability of the obtained hollow fiber membrane was 900ρ/boh
It was r' atm.

[Effect of the invention] In the conventional technology, before the yarn spun from a spinning nozzle enters a coagulation bath, non-solvent vapor in a gas atmosphere is used as a source of non-solvent absorbed from the outer surface of the yarn. However, according to the method of the present invention, the gas atmosphere between the spinning nozzle and the coagulation bath is shielded from the outside air, and the non-solvent vapor is In addition, since it generates a mist consisting of droplets of non-solvent, the amount of non-solvent absorbed from the outer surface of the thread increases significantly, so the pore diameter on the outer surface of the hollow fiber membrane is large. , and can easily produce a highly porous hollow fiber membrane with a high porosity and excellent water permeability. Further, the cylindrical object used in the production of the hollow fiber membrane of the present invention has a simple structure and can easily generate a mist made of a non-solvent, so that a hollow fiber membrane having the above characteristics can be obtained at low cost. Therefore, the present invention
It has great industrial value and will contribute to the membrane separation industry.
It's 5 6.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a hollow fiber membrane manufacturing apparatus showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a cylindrical object used in manufacturing the hollow fiber membrane of the present invention, and FIG. Scanning electron micrograph of the inner surface of the hollow fiber membrane fiber obtained in Example 1 (magnification IQ
, GQo), FIG. 4 is a scanning electron micrograph of the outer surface of the same fiber obtained in Example 1 (magnification to, ooo),
FIG. 5 is a scanning electron micrograph of the inner surface of the hollow fiber membrane fiber obtained in Comparative Example 1 (magnification 1 (1, (100), 6
The figure is a scanning electron micrograph (magnification: 10.0DD) of the outer surface of the same fiber obtained in Comparative Example 1, and Figure 7 is a scanning electron micrograph of the outer surface of the hollow fiber membrane fiber obtained in Example 2. This is a photograph (magnification: 1.0.000). ]...Spinning nozzle, 2...Jacket type tube, 3...
... Coagulation bath, 4... Yarn spun from the spinning nozzle,
5... Guide roller, 6... Winder, 7...
Constant temperature water inlet/outlet, 8... Population of yarn spun from the spinning nozzle. 7 Figure 1 Figure Figure Immediate Figure Figure Part 6 Figure 7 Figure

Claims (8)

[Claims] (1) A tube-in-orifice type spinning nozzle for spinning a membrane-forming stock solution consisting of a solution of a polymer constituting a membrane and a core liquid for forming a hollow part, and a non-solvent for the polymer or a non-solvent and a solvent. By shielding the gas atmosphere between the coagulation bath consisting of a mixed liquid of A method for producing a hollow fiber membrane, which comprises passing the yarn generated and spun out from a spinning nozzle through a gas atmosphere containing the mist, and then introducing the mist into a coagulation bath to coagulate it. (2) A method of shielding the gas atmosphere between the spinning nozzle and the coagulation bath from the outside air and generating a mist made of non-solvent is by installing a cylindrical object equipped with a cooling jacket between the spinning nozzle and the coagulation bath. The method for producing a hollow fiber membrane according to claim 1. (3) The method for producing a hollow fiber membrane according to claim 1, wherein the nonsolvent in the coagulation bath is water. (4) The method for manufacturing a hollow fiber membrane according to claim 2, wherein the tubular member is installed so that the spun fiber passes through the central axis thereof. (5) The method for manufacturing a hollow fiber membrane according to claim 2, wherein the inside of the cylindrical body is reduced in pressure and the non-solvent vapor in the coagulation bath is forcibly drawn into the gas atmosphere inside the cylindrical body. (6) The method for producing a hollow fiber membrane according to claim 2, wherein non-solvent vapor is further supplied to the gas atmosphere within the cylindrical body. (7) The method for producing a hollow fiber membrane according to claim 6, wherein both the supplied non-solvent vapor and the non-solvent in the coagulation bath are water. (8) A cylindrical object installed between the spinning nozzle and the coagulation bath, which is equipped with a cooling jacket having at least an inlet and an outlet for the yarn spun from the spinning nozzle and an inlet and outlet for the coolant, and the coolant is allowed to flow through the jacket. A cylindrical object used in hollow fiber membrane production, which generates a mist consisting of the non-solvent in the coagulation bath in the internal gas atmosphere by controlling the temperature of the internal gas atmosphere to be lower than that of the coagulation bath.