JPS6151927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a tubular permeable membrane.

Precision membranes, ultrafiltration membranes, reverse osmosis membranes, etc. (hereinafter referred to as permeation membranes) are used as liquid separation devices in various forms, but among them, liquid separation devices using tubular permeation membranes are It is widely used because the stock solution can be flowed at high speed and high pressure, making it possible to treat turbid liquids with less influence of concentration polarization, and also because the equipment is easy to clean.

The tubular permeable membrane used at this time is manufactured by spreading a membrane-forming liquid on the inner surface of the tube and subjecting the spread thin film to a coagulation process.

Conventionally, when spreading a membrane-forming liquid on the inner surface of a tube, the tube is supported horizontally, one end of the tube is filled with the membrane-forming liquid, and a bullet-shaped core having an outer diameter slightly smaller than the inner diameter of the tube is inserted. The core was then moved from one end of the tube to the other end of the tube by pulling the core with a string or blowing compressed air.

However, since the weight of the bullet-shaped core is greater than the weight of the film-forming liquid occupying the same volume as the core,
During membrane formation, due to the weight of the core, the thickness of the membrane at the bottom in the circumferential direction of the tube becomes thinner than that at the top, resulting in uneven thickness of the membrane, resulting in an uneven permeable membrane.

In order to solve the drawbacks of the prior art, the present invention has been made based on the discovery that by running a bag-shaped core inside the tube, a tubular permeable membrane with extremely low thickness unevenness can be obtained. This led to the invention.

That is, in the present invention, one end of the tube is filled with a membrane-forming liquid and a core with an outer diameter slightly smaller than the inner diameter of the tube is disposed, and then the core is passed from the tube end to the other end of the tube. A method for producing a tubular permeable membrane comprising means for spreading the membrane-forming liquid on the inner surface of the tube by running it inside the tube, characterized in that a bag-shaped core is used as the core. A manufacturing method is provided.

The present invention will be explained below based on the drawings showing examples thereof.

In FIG. 1, 1 is a tube and supports 2, 2'
It is supported horizontally by Reference numeral 3 denotes a film-forming liquid, and 4 a bag-shaped core, each of which is filled in the end of the tube.
As shown in FIG. 2, the bag-shaped core 4 is composed of a hollow portion 41, a tip portion 42, and a cylindrical portion 4'. A nozzle 5 for blowing compressed air is elastically fitted into the end of the tube, and a safety cover 6 for the bag-shaped core 4 is arranged at the other end of the tube. 7 is an air compressor, 8 is a pressure storage tank, and these are connected to a filter 9 and a pressure regulating valve 1.
They are communicated via piping 11 via 0. 12
is a pressure switch, and when the pressure in the pressure storage tank 8 reaches a certain pressure, the pressure regulating valve 10 is closed and the compressed air from the compressor 7 is discharged from the relief valve 13. 14 is a pipe that communicates the pressure accumulation tank 8 and the compressed air blowing nozzle 5, and 15 is an on-off valve. 16 is a pressure gauge, and this pressure gauge 1
After confirming that the pressure in the pressure storage tank 8 has reached the specified pressure by step 6, the valve 15 is opened and the bag-shaped core 4 can be moved into the pipe by compressed air from the pressure storage tank 8. .

The core used in the present invention has a bag-like shape, and more specifically, a conventional bullet-shaped core is modified to have a hollow portion that is approximately symmetrical about the axis of the core. , which is hollowed out from the back surface of the core. The weight of the bag-shaped core obtained at this time is usually about 1/2 or less of the weight of the bullet-shaped core (the lower limit is usually 1/10), and the center of gravity is the weight of the bag-shaped core. Preferably, it is located approximately at the center of the cylindrical portion 4'. When the bag-shaped core obtained in this way is applied to the present invention, it is usually used in consideration of the specific gravity of the membrane-forming liquid used. In other words, the specific gravity of the film forming solution is S
When manufacturing a permeable membrane using this membrane forming solution, the specific gravity per specific volume of the bag-shaped core used (the specific gravity of the bag-shaped core when the cavity is also integrated as the core volume) is usually It is said to be 0.8S to 4S.

The wall thickness of the bag-shaped core used in the present invention is determined by the predetermined weight of the core, and is usually 0.3 to 2 mm.
That's about it. Furthermore, due to problems such as the complexity of manufacturing the bag-shaped core and the distortion of the core, the wall thickness of the bag-shaped core cannot be approximately uniform at all peripheral parts, as shown in Fig. 2. preferable.

In FIG. 2, the outer diameter d of the bag-shaped core 4 is slightly smaller than the inner diameter of the tube 1, and is appropriately determined depending on the thickness of the film to be formed. Further, the viscosity of the film-forming liquid 3 is usually adjusted to 100 to 5000 poise, and the length l ₁ of the cylindrical portion 4' of the bag-shaped core 4 varies depending on the viscosity of the film-forming liquid, but usually l ₁ = 1.2 to 1.2. It is preferable to use 3D. l ₁
If it is less than 1.2d, it is difficult for the core to run stably in the pipe, resulting in the inconvenience that it is difficult to obtain a uniform film.

In addition, if l ₁ exceeds 3d, the resistance of the film-forming liquid acting on the core becomes large when the core is driven by compressed air, and the film-forming speed becomes extremely slow. Although the film forming speed is constant when the core is pulled, the resistance of the film forming liquid increases, resulting in the inconvenience that a large output is required from the motor. Furthermore, since it is preferable that the center of gravity of the bag-shaped core 4 is located approximately at the center of the cylindrical portion 4' of the core, the length l ₂ of the tip portion 42 of the core is equal to the length of the cylindrical portion 4'. It is determined by l ₁ and is usually preferably between 0.3 and 1 l ₁ . The shape of the tip 42 of the core is a conical shape, preferably a smooth conical shape, so that the core can run stably on the axis inside the tube.

Metal or plastic materials are used as the material for the core 4, but metal materials such as stainless steel, which are resistant to scratches and dirt on the surface and have good wettability with the film-forming solution, are usually preferred.

In the present invention, a nonwoven fabric tube, a glass tube, a metal tube, etc. are used as the tube.

To carry out the invention using the apparatus of FIG.
First, the tube 1 is supported horizontally, the membrane-forming liquid 3 and the bag-shaped core 4 are filled into the tube end, and then the compressed air blowing nozzle 5 is elastically fitted into the tube end.
Next, compressed air from the pressure accumulating tank 8 is fed into the tube end through the compressed air blowing nozzle 5, thereby causing the bag-shaped core 4 to travel inside the tube. The film-forming liquid 3 filled in the tube 1 in this way is poured into the core 4.
The film-forming liquid is caused to flow through the annular gap formed between the outer surface of the tube 1 and the inner surface of the tube 1, and is spread onto the inner surface of the tube as an annular thin film 3'. When the core 4 is discharged from the end of the pipe into the safety cover 6 after traveling in the pipe, the opening/closing valve 15 is closed and the blowing of compressed air is stopped. In addition to the above-mentioned air, the compressed gas is preferably an inert gas such as nitrogen or carbon dioxide.

In the above-mentioned example of the present invention, the film-forming liquid is spread on the inner surface of the tube by moving the bag-shaped core 4 inside the tube using compressed air, but there is a hole in the tip of the membrane-forming liquid. It is also possible to spread the film-forming liquid onto the inner surface of the tube by using a bag-shaped core having a core with a string passed through the through hole and pulling the core with the string to make it travel inside the tube. It is.

After the film-forming liquid is spread on the inner surface of the tube to form a thin film in this manner, a coagulation process is performed according to a conventional method. For example, when a cellulose derivative solution is used as a film-forming solution, the solvent in the film-forming solution is partially evaporated by leaving it to stand after forming a thin film, gelling it by immersion in cold water, and then subjecting it to hot water treatment. conduct.

Other methods of wet film forming include forming a thin film on the inner surface of the tube and then immersing the tube in a non-solvent of the film forming solution, and forming micropores by extracting additives from the film forming solution. The method used is to form a thin film on the inner surface of the tube and then immerse the tube in an additive solvent.

As mentioned above, since the core used in the method for producing a tubular permeable membrane of the present invention has a bag-like shape, the weight of the bag-shaped core is extremely smaller than that of a conventional bullet-shaped core, and therefore This method has the advantage that it is possible to manufacture a tubular permeable membrane with extremely little thickness deviation without being affected by the weight of the core during membrane formation.

Further, in the above-mentioned embodiment of the present invention, the tube is supported horizontally, but even if the tube is supported in an inclined state, for example, uneven thickness of the tubular permeable membrane due to the weight of the core can be similarly prevented.

Furthermore, in the method for manufacturing a tubular permeable membrane of the present invention, when compressed air is used to move the bag-shaped core into the tube and spread the membrane forming liquid on the inner surface of the tube, the pressure due to the compressed air is almost the same. Because the pressure acts on the inner surface of the tip of the bag-shaped core, compared to the conventional case where pressure acts on the back surface of the bullet-shaped core, when the film-forming liquid is spread on the inner surface of the tube, Since the tip of the core does not wobble, the core can run stably, which has the advantage that an extremely uniform tubular permeable membrane can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of the apparatus used in carrying out the present invention, and FIG. 2 is a longitudinal sectional view of the bag-shaped core used in FIG. 1. 1...tube, 3...film forming liquid, 3'...annular thin film,
4... Bag-shaped core, 5... Nozzle for blowing compressed air.

Claims (1)

[Claims] 1 One end of the tube is filled with a membrane-forming solution and a core with an outer diameter slightly smaller than the inner diameter of the tube is placed, and then the core is run into the tube from the tube end to the other end. A method for producing a tubular permeable membrane, comprising means for spreading the membrane-forming liquid on the inner surface of the tube by spreading the membrane-forming solution onto the inner surface of the tube, the method comprising using a bag-shaped core as the core.