JPS60172309A - Preparation of compound film comprising hollow yarn - Google Patents

Abstract

PURPOSE:To provide compound film of hollow yarn having thin thickness and uniform characteristics by treating the surface of porous hollow yarns with corona discharge and applying a coating agent thereto. CONSTITUTION:Porous hollow yarns 1 are wound around treating rolls 3, 3' and the surface of the yarns is treated through corona discharge electrodes 2, 2'. The yarns are then led to a coating tank 4 by a driving roll, and dipped in a soln. 6 of a coating agent to apply the soln. on the surface of the yarn, then the solvent is evaporated in a drying tower 7. Obtd. compound film of the hollow yarn is allowed to contact with a roll 8 coated with a soln. 9 of a film protecting agent, and the solvent is evaporated by drying rolls 10, 10'; the compound film of hollow yarns is thus prepd. Since the surface of porous hollow yarn is treated with corona discharge, the wettability of the surface is improved, and compound film coated iniformly with the coating agent is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hollow fiber separation membrane for selectively separating at least one gas from a gas mixture.

Research on gas separation using membranes has been going on for a long time, including recovery of hydrogen gas from natural gas etc. using polyethylene terephthalate hollow fiber membranes, recovery of helium gas from helium mixed exhaust gas, and recovery of helium gas from air using silicone rubber films. Concentrated suds of oxygen gas have been reported. Furthermore, in recent years, various separation methods based on different gases have been proposed. For example, if oxygen or nitrogen in the air could be easily and cheaply separated and concentrated from the air, it would be possible to greatly contribute to combustion equipment, the medical field, internal combustion machinery, the chemical industry, the food industry, etc. There are methods to separate air without using a polymer membrane that use zeolite or special carbon, but these take advantage of the difference in the adsorption and desorption properties of oxygen and nitrogen gases, so the adsorption and desorption process It has the disadvantage that it cannot be performed continuously. On the other hand, when a polymer membrane is used, separation can be carried out continuously, but few membranes have reached the stage of practical use due to insufficient gas permeability and gas separation properties. Gas permeation amount Q when gases A and B are separated by membrane
(=/8θ0) is expressed as.

Here, DA and DB are the permeability coefficients (c
j-elII/sea-, cj% emHg)
, A is the membrane area in contact with the feed gas (ciJ), t and P! are the partial pressures (-9) of the gas on the feed and permeate sides of the membrane.

According to this formula, in order to increase the gas permeation amount QA, a material with a high gas permeability coefficient DA is used, the area A of the membrane is increased, and the thickness T of each membrane is decreased. Possible measures include increasing the pressure difference between the supply side and the permeate side. Note that, in general, the higher the gas permeation temperature, the higher the QA.

Therefore, as a gas permeable membrane, DA, minute ME gf, and several DA
It is desirable that the /DB is high, the film area is large or the film has sufficient durability and abrasion resistance even if it is made thin, and that it has appropriate heat resistance and pressure resistance. What is important in terms of this is to reduce the film thickness T and increase the size of the gas permeable membrane, but the prerequisites are uniform processability and a stable composite membrane structure, as well as a composite membrane with continuous and stable performance. A manufacturing method is needed that can absorb the

Furthermore, when putting separation membranes into practical use, membranes are assembled into modules housed in a certain pressure vessel so that they can be used efficiently. Plant equipment costs can be reduced by increasing the membrane area per module and reducing the number of modules per processing amount. Forms of such membrane modules include hollow fiber type, flat membrane spiral type, plate and frame type, and tubular type, but the hollow fiber type has the highest membrane packing density in the module and is the cheapest in terms of module cost. Very advantageous.

From these viewpoints, the inventors of the present invention have conducted intensive research on the manufacturing method of hollow fiber composite membranes, and as a result, have developed a practical method for producing composite membranes that are thin and have excellent uniformity.

That is, the method for producing a hollow fiber composite membrane is characterized in that the surface of the porous hollow fiber is subjected to a discharge surface treatment, and then a coating agent and, if necessary, a membrane surface protective agent are applied.

In the corona discharge treatment used in the present invention, the surface of the porous hollow fiber is subjected to corona discharge treatment to improve the wettability of the surface (1) and improve the uniform adhesion of the coating agent solution (1). That is, the surface of the hollow fiber is oxidized by the corona discharge treatment to form polar groups, thereby improving the wettability. Therefore, the adhesion performance of the coating agent solution is improved, and thinning of the film is facilitated. In particular, the effect is remarkable when the surface of the hydrophobic porous hollow fiber is subjected to corona treatment. Furthermore, uniformity can be improved if the coating agent is applied immediately after the corona discharge treatment.

A known corona discharge treatment method can be used. For example, when using a vacuum tube oscillation type corona discharge method, two electrodes with a width of IC11 and a length of LOOEM are used, the output is 0.5 to 1.0 kW, and the processing time is 2 to 60 watts. The distance between the electrode and the processing roll is preferably 0.5 to 1 mm.

The porous hollow fiber used in the present invention preferably has a structure in which the surface thereof has micropores of several tens to hundreds of ongestrons (A), and the fibers become larger toward the back surface. Any material can be used as long as it is a porous hollow fiber. For example, polyvinylidene fluoride polysulfone,
Examples include porous hollow fibers such as polyether sulfone, polysulfonamide, polyamide, polycarbonate 1 polyester, and cellulose ester. In addition, it is preferable that the porous hollow fiber has a smooth and uniform structure in a dry state with no irregularities in order to form a thin film.

The polymer of the coating agent can be, but is not limited to, those known to separate components of a gas mixture, such as cellulose acetate, ethyl cellulose, polydimethylsiloxane, silicone-modified polymer 1 polycarbonate 1 polyvinyl alcohol, polystyrene, etc. It's not a thing.

The solvent for the above polymer can be used as the solvent for the coating agent solution. For example, when cellulose acetate is used as the polymer, seven tons of acetone, dioxane, cyclohexanone nitromethane or meta/-
A mixed solution of 1,000 ml, etc. is suitable.

The concentration of the polymer in the coating agent solution cannot be limited because the viscosity of the solution varies depending on the type of polymer and solvent, but it is usually 0.1 to 10% by weight. The solution temperature during coating may be in the range of 10 to 50°C.

Any known coating method can be applied to the surface of the porous hollow fiber with the coating agent solution. Examples include a method in which porous hollow fibers are immersed in a coating agent solution, a reverse roll method using a roller, and an air doctor method. Among these methods, the method of immersion in a coating agent solution is preferred from the viewpoint of uniformity of the thickness of the coating layer and durability of the film.

The hollow fibers coated with the coating agent are dried to remove the solvent and form a composite membrane. Drying varies depending on the drying method used, that is, the type of dryer, but in the case of a commonly used hot air dryer, it is preferable to dry at a temperature of 60 to 120° C. until the residual solvent is 1% by weight or less.

The membrane surface protective agent of the present invention functions advantageously in terms of the durability of permeation performance in the active coating layer when the composite hollow fiber membrane is rolled up into a bundled shape through a fiber channel or the like. Such protective agents include solid paraffin-dimethylsiloxane emulsified with a surfactant, solid paraffin silicone polymer dissolved in an organic solvent, polyvinyl alcohol, polyvinyl acetate, polystyrene, etc.
A poly-dissolved material can be used. The solution concentration of the protective agent varies depending on the type of the protective agent and the solvent, as well as the method and conditions of attachment, but is usually in the range of 0.5 to 6% by weight, resulting in a decrease in performance. On the other hand, if the thickness is less than 0.2 μm, the first effect as a protective layer, that is, mechanical protection, will be insufficient.

Any known coating means can be used to coat the composite film with the protective agent solution. Examples include a method of coating a protective agent solution on a hollow composite membrane, a method of dipping a hollow repellent membrane, and a method of spraying a protective agent solution onto a hollow composite membrane. Among these, the coating method using a roller is preferred because the thickness can be easily adjusted.

FIG. 1 is a conceptual diagram of the manufacturing process of the coating apparatus of the present invention. The porous hollow fiber 1 is wound around treatment rolls 3, 3' several times to several tens of times, and the surface of the porous hollow fiber is treated by the corona discharge electrodes 2, 2'. It is then guided into the coating tank 4 by drive rollers. The coating tank has a pair of externally driven rollers 5, 5' into which the coating solution 6 is placed. The porous hollow fibers immersed in the coating agent solution had the coachine agent solution adhered to their surfaces, and were continuously led to the drying tower 7 to evaporate the solvent, so that the coating agent was uniformly adhered to the surface of the porous hollow fibers. A hollow fiber composite membrane is obtained. Next, in order to apply the film protective agent to the surface of the composite membrane, the hollow composite membrane is brought into contact with the membrane protective agent solution 9 that has adhered to the roller surface by rotating the roller 8, and the membrane protective agent solution 9 is applied to the surface of the composite membrane. By applying the solution to the surface of the hollow bonded membrane and evaporating the solvent with drying rollers lo and 10', a hollow fiber composite membrane having the membrane preservative adhered to the surface can be obtained.

Then, it is wound onto a bobbin by a winding machine 11.

The hollow fiber composite membrane produced by the method of the present invention has excellent stability and durability due to uniform coating thickness and addition of a surface protective agent, and is useful as an industrial production method. In addition, since it is easy to form a thin film, it has excellent permeability as a gas separation membrane.

The present invention will be specifically explained below using examples.

Example 1 As a support for a composite membrane, wet-spun polysulfone hollow fibers with an outer diameter of 310μ, an inner diameter of 160μ, and a surface average pore Mlo
A dry thread of sμ was used. The corona discharge treatment device uses a vacuum tube oscillator, and as shown in Figure 1, uses two treatment rolls as electrodes to produce a discharge output of 1, . The discharge treatment time was changed by adjusting the number of turns of the hollow fiber glue at 5KW and a yarn speed of 5 m/min.

Table 1 shows the results of measuring the surface tension of the treated hollow fibers and the contact angle between the hollow fibers and water.

Example 2 The polysulfone hollow fibers that had been subjected to the corona discharge treatment under the conditions of Example 1 were then placed in a coating tank as shown in Table 1, and 1.5% by weight of polydimethylsiloxane was dissolved in a toluene solvent as a coating agent solution. The hollow fibers were immersed in a solution, and then the toluene was evaporated in a drying tower to form a single composite membrane. A 3.0% by weight aqueous solution of dimethylsiloxane emulsified with a surfactant was applied using a roller method, and then dried with hot air at 80°C. It was dried in a machine and wound up at a yarn speed of 5 m/min.

Table 2 shows the results of measuring the oxygen and nitrogen permeability of this composite membrane.

A composite membrane that has not been subjected to corona discharge treatment has a high oxygen permeation rate due to defective parts, and a low oxygen to nitrogen permeation rate ratio. Also, if the corona discharge treatment time is 4.4 seconds or more,
Since there are no defects, the permeation rate ratio between oxygen and nitrogen is large, indicating the separation coefficient of the polydimethylsiloxasane material.

Example-3 Wet-spun vinylidene fluoride hollow fiber with an outer diameter of 340μ
Inner diameter 170μ, surface average pore diameter 110μ, nitrogen permeation rate 3
．． 5 X 10 ec/7. Dry threads of sea, oaHg were used as supports for the composite membranes.

Corona discharge treatment was performed for 8.8 seconds under the conditions of Example-1, and then a composite membrane was prepared under the same conditions as Example-2. The results of measuring the surface tension of the hollow fibers without corona discharge treatment and the hollow fibers after treatment, and the oxygen and nitrogen permeation performance of the composite membrane are shown in the third section.
O shown in the table Table 3

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the manufacturing process of the coating device. 1 is a porous hollow fiber, 2.2' is a corona discharge electrode. 3.3' is a processing rail, and 4 is a coating tank. 5.5' is a roller, 6 is a coating agent solution. 7 is a drying tower, and 8 is a roller for adhesion of a preservative. 9 is a protectant solution, 10.10' is a drying roller. 11 is a winding machine. Patent applicant: Toyobo Co., Ltd.

Claims (2)

[Claims] (1) Corona discharge surface treatment on the surface of the porous hollow fiber,
A method for producing a hollow fiber composite membrane, which comprises subsequently applying a coating agent. (2) The manufacturing method according to claim (1), wherein a membrane protective agent is applied to the surface of the hollow fiber composite membrane.