JPS62286508A - Production of hollow yarn separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane high in a permeation amount per unit volume, by holding a porous hollow yarn separation membrane module under vacuum and introducing a polymerizable substance into the inside of a pipe in a gaseous state, and thereafter uniformly emitting high-frequency electromagnetic wave from the outside of the module. CONSTITUTION:A hollow yarn membrane which has 1-200nm mean pore diameter and has 1X10<-4>-1X10<-2>ml/cm.sec.cmHg air permeation velocity at 25 deg.C at a drying time is made to a module by an ordinary method. This module is held under vacuum and sufficiently dried. The degree of reduced pressure is preferably regulated to 10<-3>-10Torr. While keeping constant that degree of reduced pressure, a polymerizable substance is introduced into the inside of a pipe in a gaseous state. High-frequency electromagnetic wave is uniformly emitted from the outside of the module. The polymerizable gas is polymerized on the inner wall of the hollow yarn pipe and stuck on the inner surface of the pipe and a dense thin membrane is formed, which can be used as an activated separation layer.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Industrial Application Field) The present invention is directed to selectively separating a specific component from a liquid in which organic and/or inorganic substances are mixed or from a mixed gas. The present invention relates to a method for manufacturing a hollow fiber separation membrane used for.

(Prior art) A membrane with a hollow fiber shape is used as a membrane to separate liquids or gases. -1
The 1Ai module is characterized by a large membrane area per unit volume.

In addition, composite membranes in which dense thin layers made of different materials are laminated on a porous support and serve as a separation active layer have excellent separation performance and have been put into practical use. In particular, a thin film obtained by plasma polymerization is one of the membrane manufacturing methods that has recently attracted attention because its thickness is extremely small, the permeation rate is high, and the membrane has a unique structure.

Among hollow fiber separation membranes, those having the form of a composite membrane are
As shown in Japanese Patent Application Laid-open No. 53-86684, etc., all of these methods form a thin selective separation layer on the outer surface of the hollow fiber. In membranes that have a selective separation layer on the outer surface of the hollow fiber tube, the thin membrane that is the separation active layer may be damaged due to the membrane surface being rubbed during handling during module creation or due to contact between hollow fibers during use, resulting in membrane performance. A phenomenon in which the amount of water was significantly decreased was observed.

By forming a separation layer on the inner surface of the hollow fiber tube using a plasma polymerization method after modularizing the hollow fiber-like porous support, the present inventors maintained the membrane performance as it was at the time of creating the scar bonded membrane over a long period of time. As a result of focusing on what can be done and conducting repeated studies, we have arrived at the present invention.

(Objective of the Invention) The object of the present invention is to form a thin film having a separation function on the inner surface of a hollow fiber porous support after module molding using a plasma polymerization method, thereby achieving high membrane performance and long-term use. The object of the present invention is to obtain a stable separation membrane for liquids or gases.

(Structure of the Invention) The present invention maintains a porous hollow fiber separation membrane module under vacuum, introduces a polymerizable substance in gaseous form into the inside of the tube, and uniformly irradiates high-frequency radio waves from the outside of the separation membrane module. This is a method for producing a hollow fiber separation membrane, characterized in that the polymerizable substance is polymerized, the polymer is attached to the inner surface of a porous hollow fiber, and this is used as a separation active layer.

Porous separation membranes include hollow fibers made of organic polymers such as polysulfone, polyethersulfone, polyacrylonitrile, cellulose acetate, and polyvinylidene fluoride, or inorganic polymers such as porous glass and ceramics. Bundle it up and make it into a module.

The pore diameter of the inner surface of the porous hollow fiber is preferably 1/3 to 1/1O of the thickness of the polymer to be attached as the separation active layer. Furthermore, the pore size and membrane thickness generally vary depending on whether the object to be separated is a liquid or a gas. Usually, in the case of gas separation, it is desirable that the pore diameter is smaller, and the average pore diameter is preferably 1 lnm-100n. For liquid separation membranes, the average pore size is 3 nm to 200 nm.
It is preferable that it is m. Furthermore, the pore diameter of the inner surface of the hollow fiber must be smaller than that of the outer surface of the tube. The air permeation rate at 25°C during drying of this porous support is I X 10-' to I X 10-2 m1/cm・s
Preferably, it is ec, cmHg. If it is smaller than this, the permeation rate is low and it is not practical, and if it is larger than this, the thin film that will be formed later by plasma polymerization cannot be mechanically maintained, so it cannot be used. The pore size distribution of the support is also important, and it is desirable that it be as uniform as possible, but the maximum pore size for liquid separation is preferably 20 nm or less.

Such porous hollow fibers are modularized by a conventional method.

The material used for the outer case of the module may be any material as long as it does not interfere with the irradiation of high-frequency radio waves during plasma polymerization later, such as polysulfone, polytetrafluoroethylene copolymer, polycarbonate, polymethyl methacrylate, etc. Examples include polyacrylonitrile and glass.

The hollow fiber module is kept under vacuum and thoroughly dried under reduced pressure so that gaseous substances are not generated and do not interfere with the next plasma polymerization. The drying module is installed in a vacuum chamber for plasma polymerization equipment, and polymerization processing is performed.

The degree of reduced pressure is preferably 10-3 to 10 Torr,
10-' to 5 Torr is particularly preferred. While maintaining the degree of vacuum at a constant level, the polymerizable substance is fed into the tube inside the porous hollow fiber module in a gaseous state.

The polymerizable substance can be arbitrarily selected depending on the intended use of the membrane module. For example, the separation membrane for reverse osmosis can be selected from vinylamine, allylamine, vinylpyridine, etc., and the oxygen enrichment membrane can be selected from fluoroalkylamine, trimethylsiloxane, etc. While flowing a fixed amount of these polymerizable substances in gaseous form, high-frequency radio waves are irradiated and the output is appropriately adjusted to cause polymerization. Although some of the polymerizable gas permeates through the membrane, most of it passes through the hollow fiber tubes and is polymerized on the inner wall of the hollow fibers. As the polymerization progresses, the polymerized substance adheres to the inner surface of the tube and forms a dense thin film, which can be used as a separation active layer. The thickness of the thin film changes depending on the degree of reduced pressure, the flow rate of polymerizable gas, the polymerization time, etc., so these polymerization conditions must be selected appropriately to produce a composite film. As long as the film has strength, the thinner the film, the better.

By the method described above, a hollow fiber composite membrane having a separation function can be obtained on the inner surface of the porous hollow fiber support.

(Effects of the Invention) The hollow fiber separation membrane according to the present invention has an extremely high permeation amount per unit volume and excellent separation selectivity, so it can be used as a separation membrane for various purposes.

(Example) The present invention will be specifically explained below using Examples.

Reference example Production of polyethersulfone porous hollow fiber support Polyethersulfone (20 parts by weight), polyethylene glycol (20 parts by weight), dimethyl sulfoxide (6 parts by weight)
(0 parts by weight) are mixed uniformly and extruded from the outside of the double tube nozzle. At the same time, dimethyl sulfoxide/water (+/1) is allowed to flow from the inside. The extruded solution is 50c
After falling through m space, it was immersed in water and solidified from the membrane surface. Furthermore, it is immersed in water for 10 minutes and washed.

The produced hollow fiber thread was cut into a certain length and then dried at room temperature. The thoroughly dried hollow fibers were bundled and both ends were solidified with adhesive in the usual manner.

The membrane module obtained in the reference example was installed in the plasma polymerization apparatus shown in FIG. 1, and the polymerizable gas inlet was connected to the nozzle of the module. After reducing the pressure inside the chamber with a vacuum pump, the valve of the gas introduction tube is opened to send perfluorobutylamine in gaseous form. The pressure in the room was regulated using an automatic pressure regulating valve to be constant, and 13.56 MHz radio waves were applied to the entire module while maintaining it at IO-'Torr.

After plasma discharge was performed under high frequency voltage for 10 minutes, the valve connected to the vacuum pump was closed, and nitrogen was added to return the pressure to normal pressure.

The gas permeation performance of the membrane module after plasma polymerization is PN2 = 7.2X for oxygen gas and nitrogen gas, respectively.
10-”+11e/Cm”SeC,CmHgPo
, = 2, Ox l 0-5m/7cm2-se
c, cmHg.

Also, disassemble the module, take out the hollow fibers inside, and
- When immersed in methylpyrrolidone, the polyether sulfone dissolved and a tubular thin film was observed afterwards.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus flow for implementing the present invention. ■... Vacuum chamber 2... Polymerizable gas tank 3... Electrode 4... Membrane module 5... Automatic pressure regulating valve 6... Vacuum pump 7.
・High-frequency radio wave generator 8...Polymerizable gas inlet patent applicant Daicel Chemical Industries, Ltd. Agent
Patent Attorney Takashi Koshiba Figure 1

Claims (1)

[Claims] A porous hollow fiber separation membrane module is held under vacuum, a polymerizable substance is introduced in gaseous form into the inside of the tube, and high-frequency radio waves are uniformly irradiated from the outside of the separation membrane module to polymerize the polymerizable substance and create pores. 1. A method for producing a hollow fiber separation membrane, which comprises adhering a polymer to the inner surface of a hollow fiber and using this as a separation active layer.