JP2001242066A - Leak testing method for porous film having asymmetric structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method realizing a precise leak test by completely filling pores in a selective separation layer of a porous film having asymmetric structure with leak testing liquid. SOLUTION: In a leak testing method for a porous film constructed of the selective separation layer carrying out selective separation substantially and a supporting layer maintaining film strength and promoting permeation and provided with asymmetric structure, the porous film is immersed in a leak testing liquid having wettability to the film material, a space on the supporting layer side sectioned by the porous film is pressurized by gas after the leak testing liquid existing in the space is eliminated, and then, the gas leaking to the selective separation layer side through the porous film is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple method for performing a leak test of a porous membrane having an asymmetric structure comprising a selective separation layer for substantially performing selective separation and a support layer for maintaining membrane strength and promoting permeation. Things.

[0002]

2. Description of the Related Art Porous membranes having an asymmetric structure can increase the efficiency of membrane separation by reducing the thickness of the selective separation layer and improving the porosity of the support layer. Applications in a wide range of fields are attracting attention.

A film leak test is an indispensable process for using a film, and is always performed when the film is used. A leak test as a means for detecting a defect, a pinhole, breakage, or the like of a film is measured based on a principle equivalent to bubble point measurement. That is, the pores of the membrane are filled with a leak test liquid, and the pressure that is removed by the pressure of the gas is called a bubble point.If the membrane has defects, pinholes, breakage, etc., At a pressure below this bubble point, the liquid is removed from the defective portion and a pressure drop occurs, thereby detecting the presence or absence of a film defect. At this time, the liquid used for the leak test needs to have wettability to the porous film having the asymmetric structure. That is, if the pores present in the membrane are not filled with the liquid for the leak test, gas escapes from pores that are not clogged by the liquid, and a pressure drop occurs. Can not.
Therefore, it is difficult to completely fill the pores with the liquid for the leak test due to the thinning of the selective separation layer, and it is not possible to detect an accurate film defect. Further, these leak test liquids are easily removed by washing with evaporating water or the like so as not to cause a problem when using the membrane, and there must be no problem in safety.

[0004]

SUMMARY OF THE INVENTION The present invention has a problem of the prior art, that is, a liquid for a leak test is completely filled in pores of a selective separation layer of a porous membrane having an asymmetric structure, and an accurate leak is obtained. Providing a way to enable testing.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present invention has been reached. In other words, in a leak test method for a porous membrane having an asymmetric structure composed of a selective separation layer that substantially performs selective separation and a support layer that maintains the membrane strength and promotes permeation, the porous membrane is leaked with wettability to the membrane material. After being immersed in the test liquid and removing the leak test liquid present in the space on the support layer side separated by the porous membrane, the space is pressurized with a gas and permeated through the porous membrane. This is a leak test method for a porous membrane having an asymmetric structure, characterized by detecting gas leaking to the selective separation layer side.

[0006] Examples of liquids for leak test include alcohols such as ethyl alcohol and glycerin, halogenated hydrocarbons, ketones and water.
The material is not particularly limited as long as it has good wettability with the film material.

The gas is not particularly limited as long as it is an inert gas such as air or nitrogen and does not cause a chemical reaction with a film material or a liquid for leak test.

As the pores of the membrane, the average pore diameter on the selective separation layer side is preferably smaller than the average pore diameter on the support layer side. The leak test liquid filled in the high porosity part of the membrane moves by pressurization with gas, and the leak test liquid is filled in the smaller pores, which were insufficiently filled in the selective separation layer, to provide an accurate leak test. Becomes possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, a leak test of a membrane is performed after the membrane is assembled into a module, that is, in a usable state. The shape of the porous membrane having an asymmetric structure of the present invention is not particularly limited, such as a flat membrane and a hollow fiber membrane. The shape of the module may be any shape such as a linear double-ended type, a linear one-sided open type, and the like. Hereinafter, a specific example will be described.

Example 1 A hollow fiber membrane made of polyethersulfone was used as a porous membrane having an asymmetric structure. It has a selective separation layer inside the hollow fiber and its average pore size is 0.1 μm
And a support layer on the outside of the hollow fiber, and the average pore size is
A porous membrane having an asymmetric structure of 0.5 μm was used. Using this hollow fiber membrane, a linear open-ended module was produced using urethane resin as an adhesive. Water was used as the liquid for the leak test. Instrumentation air was used as the gas, the measurement pressure was 1.5 kgf / cm2, and evaluation was performed by measuring the transmembrane pressure loss for 10 seconds after reaching the measurement pressure.

Example 2 A hollow fiber membrane made of polysulfone was used as a porous membrane having an asymmetric structure. It has a selective separation layer inside the hollow fiber, its average pore size is 0.1 μm,
A porous membrane having a support layer on the outside of the hollow fiber and having an asymmetric structure with an average pore diameter of 0.6 μm was used. Using this hollow fiber membrane, a linear open-ended module was produced using urethane resin as an adhesive. Water was used as the liquid for the leak test. Instrument air is used for gas, and the measurement pressure is 1.5k
Evaluation was performed by measuring the transmembrane pressure loss for 10 seconds after reaching the measurement pressure of gf / cm2.

Comparative Example A hollow fiber membrane made of cellulose triacetate and having an average pore diameter of 0.1 μm was used as a porous membrane having a uniform structure. Using this hollow fiber membrane, a linear open-ended module was produced using urethane resin as an adhesive. Water was used as the liquid for the leak test. Instrumentation air was used as the gas, the measurement pressure was 1.5 kgf / cm2, and evaluation was performed by measuring the transmembrane pressure loss for 10 seconds after reaching the measurement pressure.

[0013]

[Table 1] In the case of a porous membrane having an asymmetric structure as shown in Table 1, when pressure is applied from the selective separation layer side, the pressure falls outside the measurement range.
When pressure is applied from the support layer side, a stable differential pressure value is obtained,
It was found that the film was free from defects, pinholes, etc. when the thickness was less than about 50 mmAq.

[0014]

According to the present invention, there is an advantage that the liquid for the leak test can be completely filled in the pores of the selective separation layer of the porous membrane having an asymmetric structure. Is the way.

Claims (2)

[Claims] In a leak test method for a porous membrane having an asymmetric structure comprising a selective separation layer for substantially performing selective separation and a support layer for maintaining membrane strength and promoting permeation, the porous membrane is wetted by a membrane material. Immersed in a leak test liquid having the following formula, and after removing the leak test liquid present in the space on the support layer side divided by the porous membrane, the space is pressurized with a gas to remove the porous membrane. A leak test method for a porous membrane having an asymmetric structure, characterized by detecting a gas that permeates and leaks to a selective separation layer side. 2. The leak test method for a porous membrane having an asymmetric structure according to claim 1, wherein the average pore diameter on the selective separation layer side is smaller than the average pore diameter on the support layer side.