JP3098282B2 - Hollow fiber membrane module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hollow fiber membrane module suitable for long-term storage.

[0002]

2. Description of the Related Art Recently, a hollow fiber membrane module for fluid separation has recently been used to supply a large amount of ultrapure water for semiconductor production.
High water production capacity per module is often required, and the size of modules is increasing. Therefore, it is required to reduce the weight of the module as much as possible and to simplify the mounting and dismounting. For example, a hollow fiber membrane module that supplies ultrapure water for semiconductor production is usually stored in a state filled with a bactericide such as formalin. As an encapsulation method, when the module is used at an internal pressure, a preservative solution containing less fine particles and the like can be supplied to the outside by supplying a preservative solution from the hollow portion side of the hollow fiber membrane and filtering the solution outward.
The filtration is continued until the storage solution is full on both the hollow side and the outside. In the case of using an external pressure, on the contrary, it is sufficient to supply and filter from the outside.

[0003] It is sufficient that the storage solution is stored in this state and the storage solution is withdrawn immediately before use. However, the total weight of the module in which the storage solution is sealed may be 10 kg or more, and handling is difficult. In addition, the connection port with the equipment piping must be covered, and in general, the blind flange plate on which the O-ring is applied is tightened with a V-band to seal it, which is heavy and requires a lot of trouble in mounting and removing. It was hanging.

On the other hand, it has been known that a hydrophilic polymer membrane such as polyvinyl alcohol has an initial water permeability even when stored in a dry state if water is allowed to pass therethrough. It was said that the initial permeability was not enough. For this reason, the module of the hydrophobic polymer membrane has not been stored without filling the storage solution with water. In particular, it has been said that the strong hydrophobic materials such as polyethylene, polypropylene, polyvinylidene fluoride, polysulfone, polyethersulfone, etc. lose their ability only in air unless chemically hydrophilized.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hollow fiber membrane module which can be reduced in weight and stored for a long time without deteriorating its original performance.

[0006]

According to the present invention, in a hollow fiber membrane module comprising a hydrophobic polymer hollow fiber membrane, a preservation solution is sealed so that the impregnation rate c represented by the formula (1) is 80% or more and 500% or less. It is a hollow fiber membrane module characterized by the above-mentioned.
As the hydrophobic polymer, polyethylene, polypropylene,
Examples thereof include polyacrylonitrile, polysulfone, polyethersulfone, polyvinylidene fluoride, polyimide, and polyetherimide. If the substrate film is a hydrophobic polymer, a composite film is also included.

The inner and outer diameters of the hollow fiber membrane are not particularly limited, and may be any. The type of the membrane is effective for known separation membranes such as ultrafiltration membranes and microfiltration membranes, particularly liquid separation membranes. When micron-order pores are formed, such as microfiltration membranes, performance can be recovered by treatment with alcohol etc. even when completely dried, but such processing is unnecessary for the present invention. Is also effective.

As a preservative solution, it can be applied to known preservative solutions such as pure water, hot water, an aqueous solution of formaldehyde, an aqueous solution of sodium hypochlorite, an aqueous solution of dilute nitric acid and sodium hydroxide, and a mixture thereof. The impregnation rate c is defined by the following equation (1). c = (Wm−Wd) / Wf × 100 (1) where c = impregnation rate Wm = weight of module in storage liquid (kg) Wd = weight of module in dry state (kg) Wf = hollow in dry state Weight (kg) of fiber membrane The preservation solution is sealed so that the impregnation rate c is in the range of 80% to 500%. When c is less than 80%, the influence of drying of the membrane cannot be ignored, and the water permeability tends to decrease. When c exceeds 500%, the preservation solution considerably remains. The upper limit of c varies depending on the ratio of the hollow fiber membrane in the module. As the number of hollow fiber membranes decreases in the module, the upper limit of c increases. Normally, a commercially available module is about 1000% full. In the range of more than 500% to reach a full state, the preservation solution moves in the module during transportation, for example, and thus tends to cause defects such as breakage of the hollow fiber membrane.

The optimum range of c depends on the porosity of the hollow fiber membrane. The porosity h is defined by equation (2). h = (Mw−Md) / ((Mw−Md) + Md / D) × 100 (2) where h = porosity of hollow fiber membrane Mw = weight of hollow fiber membrane in wet state (gram) Md = dry Weight of hollow fiber membrane in state (gram) D = specific gravity of polymer constituting hollow fiber membrane The weight of hollow fiber membrane in wet state is measured as follows. That is, water adhering to the surface of the hollow fiber membrane in a wet state of about 20 cm is wiped off with a filter paper or the like, and water in the hollow part is blown off by blowing 2 cc of air with a syringe or the like. The weight in this state is Mw
And Subsequently, the hollow fiber membrane is dried until a constant weight is obtained in a constant temperature dryer controlled at 50 ° C. The weight at this time is Md.

The porosity h of general hydrophobic hollow fiber ultrafiltration membranes, microfiltration membranes and the like is in the range of 65 to 85%, but in these cases, the impregnation ratio c is 200% to 400%.
% Is more preferable. 2
When it is less than 00%, the water permeability is not affected, but an air leak due to drying may be detected. Porosity h
In the case of a film having a low value, c tends to be small when the storage solution is dripped off and removed by gravity or the like. Therefore, it is more preferable that the storage solution is left slightly and the value of c becomes 400 to 500%.

The term "sealed" means that the inside of the module is isolated from the outside. Specifically, the raw water supply port and the filtrate port may be sealed with a cap or the like. Alternatively, even when each port is left open, the port may be sealed by forming a bag made of a material having low water vapor permeability such as polyethylene or polyethylene terephthalate. The hollow fiber membrane module of the present invention is obtained as follows.

That is, the storage solution is supplied from the raw water side to the hollow fiber membrane module comprising the hydrophobic polymer hollow fiber membrane. The module should be upright and supplied from the bottom entrance. On the filtrate side, the filtered stock solution comes out. When the raw water side and the filtrate side are full, after a lapse of a predetermined time, the storage solution is extracted until a predetermined value of c is reached. The disinfecting effect of sodium hypochlorite and the like varies greatly depending on the hydrogen ion concentration of the solution. When the hydrogen ion concentration is high, that is, pH
When the pH is low, the bactericidal effect increases in a short time, but as the pH decreases, more time is required. Therefore, the time until the sterilization is sufficiently performed for the pH, temperature, concentration, and the like is measured in advance, and conditions such as the time until the storage solution is extracted are determined.

[0013]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The water permeability was measured using ultrapure water at 25 ° C. and an average membrane differential pressure of 1 kg / cm ² . The unit of the water permeability is (m ³ / hr). The air leak is 1 kg from the filtrate side after filling the water on both the raw water side and the filtrate side.
/ Cm ² , and the presence or absence of bubbles in the hollow fiber and from the cut surface was visually observed in the water tank. To check for viable bacteria, supply 30 ml of pure water from the raw water side, sample the filtrate coming out to the filtrate side, and use Millipore Water Tester T
Viable cells were counted using OTALCOUNT (registered trademark).

At the initial stage, the water permeability measurement, the air leak test, and the live bacteria test were performed in this order. After storage, the test was performed in the order of live bacteria test, air leak test, and water permeability measurement.

[0015]

Example 1 Polysulfone hollow fiber ultrafiltration membrane having an inner diameter of 0.75 mm and an outer diameter of 1.35 mm (porosity h = 72%)
Approximately 90mm in diameter and 1100m in length
m was sufficiently wetted to measure the capacity, and the results shown in Table 1 were obtained. The water in the module was extracted, and a 1% aqueous formaldehyde solution was supplied instead from the raw water side. When both the raw water side and the filtrate side were full, the rubber caps were put on all the ports once and the weight was measured. As a result, Wt was 7.76 kg. Immediately drain the liquid, reattach the rubber cap and measure the weight W
m = 4.04 kg. Furthermore, it was put in a polyethylene bag, the mouth was sealed, stored in a cardboard box, and stored at 25 to 30 ° C. for one month. Table 1 summarizes the performance and the like at this time together with the data of the module which was filled and stored with water. No air leak due to drying, no reduction in water permeability, and no generation of bacteria were observed. After rinsing the water in this module, dry air at 50 degrees
The weight Wd was 2.46 kilograms when dried by continuously flowing for days. (Weight of the used hollow fiber membrane Wf =
0.48 kilograms. ) From this result, the impregnation rate c
= 329%. 3.72 kilograms (about 50%) could be handled in a lighter state than when stored in a full state.

[0016]

Examples 2 and 3 Two modules of the same brand as in Example 1 were prepared and the same experiment was carried out except for changing the storage period.
Table 2 shows the results.

[0017]

Example 4 A hollow fiber ultrafiltration membrane made of polyether sulfone having an inner diameter of 0.75 mm and an outer diameter of 1.35 mm (porosity h =
75%) Approximately 90 mm in diameter and about 1 in length
When a 100 mm cylindrical module was sufficiently wetted and its performance was measured, the results shown in Table 3 were obtained. The water in this module was extracted, and instead, a 100 ppm aqueous solution of sodium hypochlorite (pH = about 9.8) was supplied from the raw water side. Once both the raw water side and the filtrate side were full, the rubber caps were put on all the ports once and the weight was measured. As a result, Wt was 7.70 kg. One day later, the liquid was drained, the rubber cap was replaced, and the measured weight Wm = 4.
It was 14 kilograms. Further, the mouth is sealed in a polyethylene bag, stored in a cardboard box and stored in a cardboard box for 25 to 30 minutes.
Stored for 1 month in an environment of ° C. Table 3 summarizes the abilities at this time. Air leak due to drying, decrease in water permeability,
No outbreak of bacteria was observed. The weight Wd was 2.25 kg when dried by continuously flowing dry air at 50 ° C. for 3 days after the water in the module was removed. (The weight Wf of the hollow fiber membrane was 0.50 kg.) The impregnation rate c was 378%. 3.56 kilograms (about 45%) could be handled in a lighter state than when stored in a full state.

[0018]

Example 5 Polyethylene hollow fiber microfiltration membrane having an inner diameter of 0.67 mm and an outer diameter of 1.25 mm (porosity h = 70%)
A cylindrical module having a diameter of about 141 mm and a length of about 2485 mm comprising 4200 pieces and 77 hollow fiber microfiltration membranes made of polyethylene having an inner diameter of 4.0 mm and an outer diameter of 5.5 mm (when assembled, the weight is Wd. = 15 kg. The dry weight of both hollow fiber membranes was Wf =). After hydrophilizing the membrane with 100% ethanol, it was sufficiently wetted with water and the ability was measured.
Was obtained. The water in the module was extracted, and a 1% aqueous formaldehyde solution was supplied instead from the raw water side. When the raw water side and the filtrate side were full, once all caps were put on rubber caps and the weight was measured.
t = 38 kilograms. Immediately drain the liquid,
The weight Wm of the re-fitted rubber cap was 21 kg. Furthermore, it was put in a polyethylene bag, the mouth was sealed, stored in a cardboard box, and stored at 25 to 30 ° C. for one month. Table 4 summarizes the abilities at this time. No air leak due to drying, no reduction in water permeability, and no generation of bacteria were observed. The impregnation rate c = 10
5%. It could be handled 17 kg lighter than the full water condition.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

According to the present invention, the following effects are obtained. (1) While the performance was not deteriorated due to storage compared to the storage in a full state, the weight of the module was significantly reduced and the handling was remarkably improved. (2) As a secondary effect, the storage solution is conventionally disposable because the storage solution was drained when the device was attached. However, in the present invention, the storage solution was extracted during the manufacturing process of the module, so that the storage solution can be reused and cost reduced. Led to down.

(3) The amount of waste liquid can be further reduced, which contributes to prevention of environmental pollution.

Claims (1)

(57) [Claims] 1. In a hollow fiber membrane module comprising a hydrophobic polymer hollow fiber membrane, the impregnation ratio c represented by the formula (1) is 80.
%. A hollow fiber membrane module, wherein a preservation solution is enclosed so as to be at least 500%. c = (Wm−Wd) / Wf × 100 (1) where c = impregnation rate Wm = weight of module in storage liquid (kg) Wd = weight of module in dry state (kg) Wf = hollow in dry state Thread membrane weight (kg)