JP6081290B2 - Internal pressure type hollow fiber NF membrane and manufacturing method thereof - Google Patents

Description

  The present invention includes an internal pressure type hollow fiber type NF membrane for removing hardness components in tap water and natural water, a method for producing the same, a membrane module using an internal pressure type hollow fiber type NF membrane, and the membrane module. The present invention relates to a water treatment device.

  Methods for removing hardness components such as calcium ions and magnesium ions from raw water such as tap water include softening methods using ion exchange resins, methods using coagulants such as calcium hydroxide, reverse osmosis membranes and nanofiltration membranes A method of using is known.

  In the water softening method using an ion exchange resin, when the hardness component is adsorbed and saturated on the ion exchange resin, it is necessary to regenerate the ion exchange resin using salt. For this reason, when the density | concentration of a hardness component becomes high, the reproduction frequency will become high and will require an effort and expense.

  In the method using a coagulant such as calcium hydroxide, it is difficult to increase the removal rate because the addition amount of the coagulant increases in order to increase the removal rate of the hardness component.

In the method using a reverse osmosis membrane or a nanofiltration membrane (NF membrane), the conventional reverse osmosis membrane or nanofiltration membrane must remove high hardness components by applying a high pressure to the raw water side. Power increased and energy efficiency was poor. Moreover, although the membrane | film | coat with the removal rate with a high hardness part is obtained by low pressure (patent documents 1, 2), the water permeability was low also in that case, and the problem remained in processing efficiency.
Further, typical polyamide-based or polyimide-based reverse osmosis membranes and nanofiltration membranes have a problem of low heat resistance and difficulty in sterilization with hot water by heat treatment.

Patent Document 3 is an invention relating to a liquid separation membrane. In claim 6, paragraph 0024, after applying a polyfunctional amine aqueous solution on the support, an organic solvent solution containing a polyfunctional halogen compound is further applied, and the polyfunctional amine and the polyfunctional halogen compound are applied on the support. It describes that a liquid separation membrane is produced by a polycondensation reaction.
Paragraph 0021 describes that the zeta potential (pH 6-8) on the surface of the liquid separation membrane is preferably negative.

Japanese Patent Laid-Open No. 9-10666 Japanese Patent Laid-Open No. 2001-968 JP 2005-46659 A

It is an object of the present invention to provide an internal pressure type hollow fiber type NF membrane having a high removal rate and water permeability of hardness components, particularly divalent ions (calcium and magnesium), and suitable for water softening, and a method for producing the same. To do.
It is another object of the present invention to provide a membrane module having the internal pressure type hollow fiber type NF membrane and a water treatment apparatus provided with the membrane module having the internal pressure type hollow fiber type NF membrane.

As a means for solving the problems, the present invention
Provided is an internal pressure type hollow fiber type NF membrane in which a cationic polymer is bonded to a hollow fiber membrane comprising a mixture containing a sulfonated polyethersulfone and a polyethersulfone.

The present invention provides a solution to other problems.
A method for producing the above internal pressure type hollow fiber NF membrane,
Producing a membrane substrate from a mixture comprising sulfonated polyethersulfone and polyethersulfone;
Provided is a method for producing an internal pressure type hollow fiber type NF membrane, which comprises a step of bringing the membrane substrate obtained in the above step into contact with an aqueous solution of a cationic polymer.

  Furthermore, the present invention provides, as another means for solving the problem, a membrane module having a front hollow fiber type NF membrane and a water treatment apparatus including the membrane module having the hollow fiber type NF membrane.

  Since the hollow fiber type NF membrane of the present invention has a high removal rate of divalent ions, it has a high salt rejection and a high water permeability.

<Hollow fiber type NF membrane>
The hollow fiber type NF membrane of the present invention (NF hollow fiber membrane) is obtained by binding a cationic polymer to a hollow fiber membrane (hollow fiber membrane substrate) made of a mixture containing sulfonated polyethersulfone and polyethersulfone. is there.
Here, “bonded” does not mean that the cationic polymer is simply attached to the hollow fiber membrane (hollow fiber membrane substrate), and does not fall off even when washed with water in the membrane production stage. It means that the state is strongly coupled to such an extent that there is almost no decrease in filtration performance even during operation.
Although the details of the bonding state are unknown, it is cationic in the pores of the hollow fiber membrane (hollow fiber membrane substrate) that is ionically bonded between the sulfo group of the sulfonated polyethersulfone and the cationic polymer. It is considered that the state in which the polymer is permeated and held is included.

  Since the hollow fiber type NF membrane of the present invention has a cationic polymer bound to a hollow fiber membrane (hollow fiber membrane substrate), the zeta potential on the surface at pH 6 to 7 becomes +.

The sulfonated polyethersulfone can be produced by applying the method described in the production method in, for example, JP-A No. 02-208322 or US Pat. No. 4,508,852.
The degree of sulfonation (substitution degree) of the sulfonated polyethersulfone is preferably 0.04 to 0.22, more preferably 0.06 to 0.20, and still more preferably 0.10 to 0.18. When the sulfonation degree is within the above range, both the removal rate of the hardness component and the pure water permeability coefficient can be increased when the internal pressure type hollow fiber type NF membrane is used.

The content of the sulfonated polyethersulfone and the polyethersulfone in the total amount is preferably 20 to 50% by mass for the sulfonated polyethersulfone, more preferably 20 to 40% by mass, and 80 to 50 for the polyethersulfone-based polymer. % By mass is preferable, and 80 to 60% by mass is more preferable.
When the ratio of both components is within the above range, both the removal rate of the hardness component of the hollow fiber type NF membrane and the pure water permeability coefficient can be increased. In addition, a hollow fiber NF membrane having good alkali resistance and heat resistance can be obtained.

The sulfo group of the sulfonated polyethersulfone can be of a salt type or an acid type, but an acid type is preferred because solubility in a solvent can be increased.
Further, by using an acid type, the amount of foreign matter gel in the dope solution is reduced, and an effect of reducing membrane leakage of the obtained hollow fiber membrane can be obtained.
Furthermore, in the case of the acid type, the membrane strength of the hollow fiber is increased and the elongation is increased by about 1.5 times compared to the salt type. Therefore, a separation membrane having improved stability even in long-term use can be obtained. Can be obtained.

  In addition, the mixture containing the sulfonated polyethersulfone and the polyethersulfone can contain a small amount of polyethylene glycol, lithium chloride and the like.

  Examples of the cationic polymer include polydiallyldialkylammonium salts, copolymers containing structural units derived from diallyldialkylammonium salts, polyethyleneimine, hydroxypolyethyleneimine, polyallylamine, and polyamidines. Among these, Polydiallyldialkylammonium salts are preferred.

The polydiallyldialkylammonium salt has fluorine, chlorine, bromine, iodine or the like as a counter ion, and may have an anion such as sulfuric acid, nitric acid, phosphoric acid or carbonic acid.
As the polydiallyldialkylammonium salt, polydiallyldialkylammonium chloride is preferable.
The molecular weight of the polydiallyldimethylammonium salt is preferably in the range of 5,000 to 300,000.
Polydiallyldialkylammonium salts (polydiallyldialkylammonium chloride) are manufactured by Nittobo Co., Ltd., part number PAS-H-1L (molecular weight 8,500), part number PAS-H-5L (molecular weight 40,000), part number PAS-H-10L (molecular weight 200,000) ) Etc. can also be used.

  The inner diameter and outer diameter of the hollow fiber type NF membrane of the present invention are not particularly limited, but preferably the inner diameter is 0.2 to 1.0 mm, more preferably 0.3 to 0.7 mm, preferably The outer diameter is 1.3 to 1.8 times the inner diameter, more preferably 1.4 to 1.7 times. By setting the inner diameter and the outer diameter within the above ranges, it is preferable because the cleaning performance can be improved without damaging the membrane even when back-pressure cleaning is performed.

The hollow fiber type NF membrane of the present invention has a hardness component removal rate (removal rate of hardness component in tap water) determined from the following formula by the measurement method described in the examples at 80% or more under operating conditions of a recovery rate of 10%. And those with 50% or more under operating conditions with a recovery rate of 80% are preferred.
The hollow fiber type NF membrane of the present invention has a hardness component removal rate (removal rate of calcium chloride in the calcium chloride aqueous solution) determined from the following formula by the measurement method described in the examples under an operating condition where the recovery rate is 10%. % Or more is preferable, and 50% or more is preferable under the operating condition where the recovery rate is 80%.
Hardness component removal rate = [1- (hardness component amount in permeate) / {(hardness component amount in supply liquid + hardness component amount in concentrated liquid) / 2}]

The hollow fiber type NF membrane of the present invention preferably has a pure water permeability coefficient (PWP) of 5 L / m ² h · 0.1 MPa or more, more preferably 10 L / m ² h · 0.1 MPa or more, and further preferably 15 L / m. m ² h · 0.1 MPa or more.

Regarding the relationship between the hardness component removal rate and the pure water permeability coefficient in the hollow fiber type NF membrane of the present invention, the pure water permeability coefficient decreases as the hardness component removal rate increases, and the hardness component removal rate decreases as the pure water permeability coefficient increases. Tend to be.
For this reason, from the viewpoint of maintaining the hardness component removal rate and the pure water permeability coefficient at a high level with good balance, the hardness component removal rate under the operating condition of the recovery rate of 10% is maintained at 80% or more, and the recovery rate is 80%. It is preferable to maintain the hardness component removal rate under the condition at 50% or more and maintain the pure water permeability coefficient in the range of 10 to 25 L / m ² h · 0.1 MPa.

The hollow fiber type NF membrane of the present invention is suitable as a membrane for producing soft water by removing hardness components from tap water, river water, lake water, seawater and the like.
The hollow fiber type NF membrane of the present invention can be applied to a soft water producing device, a pretreatment device for seawater desalination, a pretreatment device for producing purified water for medical use such as artificial dialysis, a water purifier, and the like.

<Method for producing hollow fiber type NF membrane>
The hollow fiber membrane used as the membrane substrate can be produced by applying a known spinning method using a membrane-forming solution.
The film forming solution is prepared by dissolving sulfonated polyethersulfone and polyethersulfone in a solvent.
The sulfonated polyethersulfone and the polyethersulfone may be added and dissolved together in the solvent, but it is desirable to add and dissolve the polyethersulfone after the sulfonated polyethersulfone is added and dissolved in the solvent first. .
As the solvent, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, N, N · dimethylformamide and the like can be used.
The weight average molecular weight (Mw) of the polyethersulfone is preferably 30,000 to 100,000.

The proportion of sulfonated polyethersulfone, polyethersulfone and solvent in the membrane-forming solution is:
The sulfonated polyethersulfone is preferably 5 to 20% by mass, more preferably 8 to 15% by mass,
The polyethersulfone is preferably 10 to 30% by mass, more preferably 15 to 25% by mass,
A solvent is the adjustment amount made into 100 mass% in total.
Furthermore, in order to increase the membrane strength, the total polymer component concentration (total concentration of sulfonated polyethersulfone and polyethersulfone) in the membrane-forming solution is preferably 20 to 40% by mass, and preferably 25 to 35% by mass. More preferably.

Thereafter, the obtained film forming solution is defoamed and then spun.
In spinning, a film forming solution is discharged from the outer peripheral portion of the double spinning nozzle, and at the same time, a non-solvent (internal coagulation liquid) as a film forming component is discharged from the central hole.
The temperature of the film forming solution during spinning is preferably 30 to 100 ° C.
Water can be used as the internal coagulation liquid, and the temperature is preferably 10 to 20 ° C, more preferably 5 to 10 ° C.

Thereafter, the spun hollow fiber is guided from the double spinning nozzle to the coagulation tank through the drying space and solidified to obtain a hollow fiber type NF membrane.
Water can be used as the coagulation liquid in the coagulation tank, and the temperature is preferably 20 to 80 ° C, more preferably 30 to 70 ° C.
The temperature of the drying space is preferably 20 to 80 ° C. and more preferably 30 to 60 ° C. in order to produce a film having a dense structure.
The distance of the drying space is preferably 10 to 150 mm.

In the next step, the hollow fiber membrane substrate produced by the above method is brought into contact with an aqueous solution of a cationic polymer.
The cationic polymer concentration in the aqueous cationic polymer solution can be in the range of 5 to 50% by mass.

The contact step is not particularly limited as long as the hollow fiber membrane substrate and the cationic polymer aqueous solution can be sufficiently contacted, but in the present invention,
(I) a method of immersing the hollow fiber membrane substrate in an aqueous cationic polymer solution,
(II) a method of filtering an aqueous cationic polymer solution through a hollow fiber membrane substrate,
(III) A method of feeding and filling the cationic polymer solution into the hollow fiber membrane module,
(IV) It is preferable to apply any of the contact methods of circulating the cationic polymer solution to the hollow fiber membrane module.

In the methods (I) to (IV), the hollow fiber membrane substrate and the cationic polymer aqueous solution can be contacted after the hollow fiber membrane substrate and the alkaline aqueous solution are contacted.
Thus, the pretreatment using the alkaline aqueous solution can increase the rate of introduction of the cationic polymer into the hollow fiber membrane substrate.
As the alkaline aqueous solution, an aqueous solution of sodium hydroxide, potassium hydroxide or the like can be used.
The alkali concentration in the aqueous alkali solution is preferably 0.01 to 1N. The alkali treatment can be performed by heating an aqueous alkali solution to 60 ° C. to 90 ° C. and immersing the hollow fiber membrane in this solution for 1 to 4 hours.

In the contact method (I), the hollow fiber membrane substrate is placed in a cationic polymer aqueous solution of about 2 to 20 times the volume of the hollow fiber membrane substrate at 10 to 120 ° C. for 0.5 to 24 hours. A dipping method can be applied.
When the cationic polymer concentration in the aqueous solution is high and low, the contact time can be shortened as the concentration increases.
When the temperature is high and low, the contact time can be shortened as the temperature is higher. Therefore, it is preferable to make it contact at temperature higher than room temperature (10-30 degreeC).
When making it contact, the defoaming process by pressure reduction for removing the air contained in the inside of a hollow fiber membrane base material can also be performed.

  The contact method of (II) is, for example, a normal filtration operation in a state where a plurality of hollow fiber membrane base materials are bundled and the end portions are made into a normal membrane module in which the hollow fiber membranes are bonded with polyurethane or epoxy resin. A method of filtering an aqueous cationic polymer solution under conditions can be applied.

  The contact method of (III) is, for example, a cationic polymer aqueous solution in a state where a plurality of hollow fiber membrane base materials are bundled and the end portion is made into a normal membrane module in which the hollow fiber membranes are bonded with polyurethane or epoxy resin. And a method of filling the hollow fiber membrane with a cationic polymer aqueous solution can be applied.

  As the contact method of (IV), a method of circulating and feeding a cationic polymer aqueous solution in a state where a hollow fiber membrane module is formed as in the case of (III) can be applied.

It is preferable to wash with water after the contacting step.
The water washing step is a step of removing the unreacted cationic polymer by washing the hollow fiber membrane or the hollow fiber membrane module after the heating step with water.
The washing method is not particularly limited, and running water washing, running water circulation washing for circulating washing water, immersion washing, immersion stirring washing, and the like can be applied.
When applying immersion cleaning, a method is applied in which the hollow fiber membrane is immersed in water (tap water, ion-exchanged water, etc.) about 30 to 300 times the volume of the hollow fiber membrane for 1 to 20 hours. be able to.

  The obtained hollow fiber type NF membrane preferably has a desalination rate of 70% or more, more preferably 75% or more, and still more preferably 80% or more.

<Membrane module>
The membrane module of the present invention has the hollow fiber type NF membrane described above.
For example, a case housing having a liquid inlet / outlet can be filled with a number of hollow fiber membrane type NF membranes. Specifically, it can be the one shown in FIG. 1 of JP-A-11-333261 and the one shown in FIG. 1 of JP-A-2004-330081.

<Water treatment device>
The water treatment device of the present invention is a device provided with a membrane module having the hollow fiber type NF membrane of the present invention, together with the membrane module, other membrane devices (RO membrane device, UF membrane device, etc.), activated carbon treatment device. In addition, it can be combined with various known water treatment apparatuses such as a prefilter, a UV apparatus, and an aggregating apparatus.
For example, the apparatus shown in FIG. 1 for carrying out the invention of the method for producing low-concentration seawater described in JP 2010-58101 A, and the method for producing mineral liquid described in JP 2002-292248 are implemented. 1 to 4 for carrying out, the apparatus shown in FIG. 1 for carrying out the method for producing purified water for medical use disclosed in JP2009-39696, described in JP-T-11-504564 The hollow fiber type NF membrane module of the present invention can be used as the NF membrane module of the apparatus shown in FIG. 1 for carrying out the nanofiltration method of the aqueous solution.

(1) Sulfonation degree (substitution degree)
The sulfonated polyethersulfone after purification and drying was dissolved in deuterated dimethylsulfoxide and measured by 600 MHz H-NMR (BRUKER AVANCE 600). The degree of sulfonation (substitution degree ) was calculated from the peak integrated value of aromatic ring hydrogen obtained by 1H-NMR spectrum and the following formula (1).
Sulfonation degree (substitution degree )
= [ Integrated value of 8.2 to 8.5 ppm ((1) in the following chemical formula ) ] / { ([Integrated value of 6.8 to 8.2 ppm ((2) to (5) in the following chemical formula )]-[8.2 to 8.5 ppm Integral value] × 2 ) / 4 + [8.2 to 8.5 ppm integral value] }

(2) Hardness component removal rate (desalting rate)
A hollow fiber membrane module for testing was manufactured by using five hollow fiber membranes obtained by opening the both ends of the hollow fiber membranes obtained in Examples and Comparative Examples, and sealing both ends with an epoxy resin in a case housing. .
An internal pressure cross flow for discharging concentrated water from the other end side while supplying tap water having a hardness of 50 mg / L to the inside of the hollow fiber membrane by applying a pressure of 0.5 MPa from one end side of the test hollow fiber membrane module. Filtration was performed. The cross flow speed was 1 m / s.
After draining the initial filtrate for about 1 minute immediately after the start of the internal pressure crossflow filtration, the feed liquid, the permeate and the concentrated liquid were collected and collected, and the hardness was measured by measuring the total hardness. The total hardness was measured using a drop test (WAD-TH manufactured by Kyoritsu Riken Corporation).

  Further, in place of tap water having a hardness of 50 mg / L, an internal pressure cross flow filtration is performed under exactly the same conditions as in the case of the tap water except that a 100 mg / L (100 ppm) aqueous solution of calcium chloride is used. The concentrated solution was collected and the hardness (calcium content) was measured by a drop test.

The hardness component removal rate (%) was calculated from the following formula using the measured hardness value of each sample solution.
Hardness component removal rate (and calcium chloride removal rate)
= [1- (hardness component amount in permeate) / {(hardness component amount in supply liquid + hardness component amount in concentrate) / 2}]
The recovery rate (%) was calculated from the following equation by measuring the amount of permeate and the amount of concentrate.
Recovery rate = [(Amount of permeate) / (Amount of permeate + Amount of concentrate)] × 100

(3) Pure water permeability coefficient (PWP)
After draining the initial filtrate for about 1 minute immediately after the start of internal pressure crossflow filtration with pure water supplied at 0.5 MPa from the other end side with one end side of the above test hollow fiber membrane module closed The mass of pure water permeating from the hollow fiber membrane for a certain time was measured. This mass was divided by the sampling time (h), the membrane area (m ² ) on the inner surface of the hollow fiber membrane, and the pressure (0.5 MPa) to obtain a pure water permeability coefficient [L / m ² h · 0.1 MPa].

Example 1
<Synthesis of sulfonated polyethersulfone>
Polyethersulfone (PES) (manufactured by Sumitomo Chemical Co., Ltd., Sumika Excel 5200) was dried at 100 ° C. for 12 hours. PES was added to a 20 L four-necked flask under an argon stream, and sulfuric acid (5.0 L) was added with stirring.
After the addition, the temperature in the flask was raised to 40 ° C., dissolved over 6 hours, and then allowed to cool. Chlorosulfonic acid (3366 g) was added dropwise while stirring this solution at a flask internal temperature of 0 ° C. Immediately after the dropping, the foam was vigorously foamed, so the dropping was performed slowly, and after the foaming stopped, the speed was increased to complete the dropping.
After completion of dropping, the reaction was stirred for 4.2 hours at 30 ° C. in the flask, and PES was sulfonated.
The reaction solution was dropped into ion-exchanged water (36 L) over 120 minutes to precipitate a white polymer, and sulfonated polyethersulfone (SPES) was collected by filtration. The recovered SPES was repeatedly washed with water until the conductivity of the cleaning solution was 200 μS or less, and recovered by filtration.
The collected SPES was dried at 80 ° C. for 91 hours to obtain an acid-type SPES having a sulfo group. The acid type SPES obtained had a sulfonation degree (substitution degree) of 0.16.

<Production of hollow fiber membrane>
(Preparation of film forming solution and defoaming step)
The above acid type SPES (10% by mass) was added to 65% by mass of dimethyl sulfoxide (DMSO) and dissolved by heating at 90 ° C. for about 1 hour.
Next, 25% by mass of polyethersulfone (PES) (manufactured by Sumitomo Chemical Co., Ltd., Sumika Excel 5003; Mw = 30,000) is added to the solution, and the mixture is heated and dissolved at 90 ° C. for about 6 hours to form a film forming solution. Got.
Thereafter, the film forming solution was degassed at 90 ° C. for 15 hours.

(Spinning process)
Using the defoamed membrane-forming solution, spinning was performed at 40 ° C. with a double spinning nozzle. 20 ° C. water was used as the internal coagulation liquid (non-solvent).
After discharging from the double spinning nozzle, it was dried through a drying space (40 ° C.) at a distance of 100 mm and passed through a coagulation tank containing 40 ° C. water.
Then, the hollow fiber membrane used as a film | membrane base material was wound up through the washing tank containing 40 degreeC water further.

<Contact process>
Hollow fiber membrane (inner diameter 0.5mm, outer diameter 0.8mm, length 1000mm) was added to polydiallyldimethylammonium chloride (molecular weight 40,000) (manufactured by Nittobo, PAS-H-5L) in an aqueous solution of 2.8% by mass at room temperature. In the soaked state, vacuum degassing was performed for 1 minute.
Thereafter, the hollow fiber membrane was heated to 80 ° C. while being immersed in the aqueous solution, and then contacted in a heated state for 3 hours.
After 3 hours, the hollow fiber membrane was taken out, immersed in tap water for 15 hours, and the excess polydiallyldimethylammonium chloride was washed to obtain an NF hollow fiber membrane.

Example 2
In the contact step of Example 1, an NF hollow fiber membrane was obtained in the same manner except that it was heated at 40 ° C. for 3 hours.

Example 3
In the contacting step of Example 1, an NF hollow fiber membrane was obtained in the same manner except that PAS-H-10L (molecular weight 200,000) manufactured by Nittobo Co., Ltd. was used as polydiallyldimethylammonium chloride.

Example 4
The degree of sulfonation was the same as in Example 1 except that the reaction conditions for sulfonation of PES in Example 1 <Synthesis of Sulfonated Polyethersulfone> were changed to a stirring reaction at a flask internal temperature of 30 ° C. for 6 hours. 0.18 SPES was synthesized.
An NF hollow fiber membrane was obtained in the same manner as in Example 1 except that SPES having a sulfonation degree of 0.18 was used.

Example 5
<Production of hollow fiber membrane>
(Preparation of film forming solution and defoaming step)
10% by mass of the acid type SPES obtained in Example 1 was added to 65% by mass of dimethyl sulfoxide (DMSO) and dissolved by heating at 90 ° C. for about 1 hour.
Next, 25% by mass of polyethersulfone (PES) (BASF's Ultrason (R) E 6020P; Mw = 51,000) is added to the solution and dissolved by heating at 90 ° C. for about 6 hours to obtain a film forming solution. It was.
Thereafter, the film forming solution was degassed at 90 ° C. for 15 hours.

(Spinning process)
Using the defoamed membrane-forming solution, spinning was performed at 80 ° C. with a double spinning nozzle. 20 ° C. water was used as the internal coagulation liquid (non-solvent).
After discharging from the double spinning nozzle, it was dried through a drying space (40 ° C.) at a distance of 100 mm, and passed through a coagulation tank containing 60 ° C. water.
Then, the hollow fiber membrane used as a film | membrane base material was wound up through the washing tank containing 40 degreeC water further.

<Contact process>
A hollow fiber membrane (inner diameter 0.5 mm, outer diameter 0.8 mm, length 1000 mm) was immersed in an alkaline aqueous solution (0.1N aqueous solution of NaOH) for 2 hours. After the alkali treatment, the hollow fiber membrane was taken out and washed with running water for about 5 minutes with ion exchange water.
Then, the hollow fiber membrane was degassed under reduced pressure for 1 minute in a state where it was immersed in an aqueous solution of 2.8% by mass of polydiallyldimethylammonium chloride (molecular weight 40,000) (manufactured by Nittobo Co., Ltd., PAS-H-5L) at room temperature.
Thereafter, the hollow fiber membrane was heated to 80 ° C. while being immersed in the aqueous solution, and then contacted in a heated state for 3 hours.
After 3 hours, the hollow fiber membrane was taken out, immersed in tap water for 15 hours, and the excess polydiallyldimethylammonium chloride was washed to obtain an NF hollow fiber membrane.

Comparative Example 1
The hollow fiber membrane manufactured in Example 1 and not subjected to the contact process was used as the hollow fiber membrane of Comparative Example 1.

Comparative Example 2
The hollow fiber membrane produced in Example 4 and not subjected to the contact process was designated as the hollow fiber membrane of Comparative Example 2.

  The NF hollow fiber membrane of the present invention has a well-balanced PWP and hardness component removal rate. In Example 1, the hollow fiber membrane substrate and the polydiallyldimethylammonium chloride are strongly bonded as confirmed from the fact that the excess polydiallyldimethylammonium chloride was washed by immersing in tap water for 15 hours. It is.

Example 6 (alkali resistance test)
A test hollow fiber membrane module was manufactured by using five NF hollow fiber membranes of Example 3 with both ends opened and sealing both ends with an epoxy resin in a case housing.
A pH 12 sodium hydroxide aqueous solution was passed through the module, the hollow fiber membrane was immersed in the sodium hydroxide aqueous solution for 15 hours, and then the alkaline solution was drained and washed, and each measurement shown in Table 2 was performed.

Example 7 (heat resistance test)
A test hollow fiber membrane module was produced in the same manner as in Example 6.
Hot water at 90 ° C. was passed through the module, and the module was cooled to room temperature after maintaining the heated state at 90 ° C. for 8 hours. Thereafter, each measurement shown in Table 2 was performed.

  As can be confirmed from Table 2, the NF hollow fiber membrane of the present invention was excellent in both alkali resistance and heat resistance.

Example 8 (long-term operation test)
Using the NF hollow fiber membrane of Example 3, a membrane module for the following test was produced.
Forty NF hollow fiber membranes having both ends opened were cut to a required length and then accommodated in a case housing.
Thereafter, temporary caps were attached to both ends, and epoxy resin was put on one side and sealed.
After the epoxy resin was solidified, the bonded portions at both ends were cut so that both ends of the hollow fiber membrane were opened, and a membrane module for testing was obtained.
<Membrane module>
Membrane area: 0.019m ²
Number of hollow fibers: 40 Effective length: 25 cm

  Using the membrane module for testing, continuous operation using tap water (hardness 50) in Himeji City, Hyogo Prefecture under conditions of membrane inlet pressure 0.3 MPa, recovery rate 80%, no back pressure cleaning The pure water permeability coefficient (PWP) and hardness component removal rate for each period shown in Table 3 were measured.

Even in the long-term filtration operation using the membrane module using the NF hollow fiber membrane of Example 3, a stable hardness component removal rate was shown.
This fact also confirms that the hollow fiber membrane substrate and polydiallyldimethylammonium chloride are strongly bonded in the NF hollow fiber membrane of the present invention.

Claims (6)

Look including a sulfonated polyether sulfone and polyether sulfone state, and are not cationic polymer in the hollow fiber membrane made of a mixture containing no polyvinylpyrrolidone is coupled,
The content ratio in the total amount of the sulfonated polyethersulfone and the polyethersulfone is sulfonated polyethersulfone 20 to 40% by mass, polyethersulfone 80 to 60% by mass,
The sulfonation degree of the sulfonated polyethersulfone is 0.10 to 0.18,
An internal pressure type hollow fiber type NF membrane , wherein the cationic polymer is a polydiallyldialkylammonium salt . In the recovery of 10% of the operating conditions, the hardness component removal rate obtained from the following formula is 75% or more, according to claim 1 inner pressure hollow fiber NF membrane according.
Hardness component removal rate = [1- (hardness component amount in permeate) / {(hardness component amount in supply liquid + hardness component amount in concentrated liquid) / 2}] A method for producing an internal pressure type hollow fiber NF membrane according to claim 1 or 2 ,
Producing a hollow fiber membrane from a mixture comprising sulfonated polyethersulfone and polyethersulfone;
A method for producing an internal pressure type hollow fiber type NF membrane, comprising a step of bringing the hollow fiber membrane obtained in the above step into contact with an aqueous solution of a cationic polymer. The method for producing an internal pressure type hollow fiber type NF membrane according to claim 3 , wherein the contacting step is a step of heating the hollow fiber membrane in a state of being immersed in an aqueous solution of a cationic polymer. A membrane module having the internal pressure type hollow fiber type NF membrane according to claim 1 or 2 . The water treatment apparatus provided with the membrane module which has an internal pressure type hollow fiber type NF membrane of Claim 1 or 2 .