JPH04227833A - Semipermeable composite membrane - Google Patents

Abstract

PURPOSE:To provide a semipermeable composite membrane excellent in fractionating property in the medium and low mol.wt. region and excellent in membrane formability, water permeability and resistance to heat and chemicals or a charged semipermeable composite membrane capable of excellently separating ionic material. CONSTITUTION:The thin layer of a polyamine having >=500mol.wt. is formed on the porous surface consisting of the aromatic condensation polymer having a halomethyl group by chemical bonding to obtain the semipermeable composite membrane.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to improved semipermeable composite membranes. More specifically, by using chemical bonds to stably exist a thin film of polyamine such as polyethyleneimine on a porous film made of an aromatic condensation polymer having halomethyl groups, heat resistance, chemical resistance, and medium-low molecular weight can be achieved. This invention relates to a semipermeable composite membrane with excellent fractionation of components.

0002

[Prior Art and Problems to be Solved by the Invention] In general, a method of selectively permeating a specific component from a liquid mixture such as a solution or liquid mixture by membrane treatment to separate, concentrate, and purify it is an energy-saving method. It is widely used in practical applications. Particularly recently, membrane processing methods have been used in food processing, pharmaceutical industries,
It is applied in various fields such as water treatment.

However, in such membrane treatment methods, components with medium and low molecular weights, ie, molecular weights of about 50 to 2,000, are selectively separated from liquid mixtures having various molecular weights (hereinafter referred to as separation). Although there are some semipermeable membranes on the market that have the ability to produce a film, they do not satisfy user requirements for fractionation, permeation flux, and durability such as heat resistance and chemical resistance. something doesn't exist.

There is a strong demand for the development of semipermeable membranes having the above-mentioned performance, and various studies have been conducted. Some of them include membranes with medium-low molecular weight fractionation (
First, cellophane, cellulose acetate, cellulose nitrate, etc. are used as materials to form the membrane (hereinafter also simply referred to as fractionation membranes), and various film forming conditions such as polymer concentration, type of solvent, evaporation rate, type of additives, coagulation liquid composition, etc. After considering various heat treatments, etc.
Although there have been attempts to improve the targeted performance, sufficient results have not yet been achieved.

[0005] Polyion complex membranes composed of aromatic polycations and aromatic polyanions are also said to exhibit fractionation properties for medium and low molecular weights, but the large variation in products makes it impossible to produce membranes with large areas for practical use. is the reality.

Furthermore, in JP-A-63-240901, the aromatic etherimide polymer on the membrane is subjected to halomethylation such as chloromethylation, and then a polyamine compound is reacted with the halomethyl group to form a quaternary ammonium base. A method for producing a selectively permeable membrane for medium and low molecules having a crosslinked structure is disclosed. However, the polyamine compound used as this crosslinking agent has a relatively low molecular weight, and since it is a type of anion exchange membrane in which a quaternary ammonium salt exists throughout the membrane, it is However, there is a problem in that the membrane easily expands and contracts, which changes the fractionation performance.

On the other hand, a method has been proposed in which a composite membrane in which a dense layer with solute exclusion properties is provided on a porous support is used to exhibit fractionation in the target medium-low molecular weight region. For example, US Pat. No. 3,744,642 discloses a method for producing a composite membrane by crosslinking a polyamine on a porous support such as a cellulose ester through an interfacial polycondensation reaction using an acid chloride. Furthermore, in JP-A-49-133282, a polyethyleneimine film is first coated on a porous support such as polysulfone, and then crosslinked by interfacial polycondensation reaction using a polyfunctional crosslinking agent such as tolylene diisocyanate. A method of manufacturing a reverse osmosis membrane is disclosed. However, when these porous supports are coated with polyamines, the polyamines do not remain only on the surface of the porous supports, but tend to penetrate into the interior of the supports. Since the polyamine that has permeated into the interior is partially thermally polymerized during heating in subsequent operations, it has been difficult to produce a membrane with constant membrane performance with good reproducibility. Additionally, when using an interfacial polycondensation reaction, a solvent that is immiscible with water, such as hexane or heptane, is usually used as the solvent for the crosslinking agent, but if the membrane is post-treated with such a solvent, the membrane may warp. Or, because it is difficult for the reaction at the interface to proceed uniformly, it is difficult to obtain membrane performance in each part of the membrane, which makes it difficult to obtain a constant membrane performance, especially a constant permeation flux. Have difficulty. Furthermore, there is a problem that the chemical resistance and durability of the film are poor due to non-uniformity in each part of the film. In addition, in JP-A-54-15479, a thin film of a polyfunctional crosslinking agent having a functional group capable of reacting with the amino group of polyethyleneimine is formed on a porous support, and then the thin film is added to a solution of polyethyleneimine. A method is disclosed for obtaining a semipermeable composite membrane by treatment with. However, since there is only a weak adhesion between this porous support and the thin film of the polyfunctional crosslinking agent due to adsorption, the resulting composite film is structurally unstable, and the heat resistance and chemical resistance of the film are poor. There is a problem with being inferior in gender.

Furthermore, in JP-A-57-174104, a semipermeable membrane made of polysulfones having various functional groups such as halomethyl groups is treated with a solution of a polyfunctional crosslinking agent such as polyamine to form a crosslinked structure. A method for obtaining a semipermeable membrane having a This semipermeable membrane is said to exhibit fractionation in the medium and low molecular weight region. However, since this semipermeable membrane has a crosslinked structure throughout the membrane, there is a problem in that the mechanical properties of the membrane are hard and brittle. That is, it is easily cracked and has poor durability. In addition, water permeability is low and not sufficient.

[0009] Accordingly, it is an object of the present invention to provide a semipermeable composite membrane that does not have the above-mentioned problems. That is, the object of the present invention is to provide a semipermeable composite membrane that has excellent fractionation properties in the medium and low molecular weight region, and is also excellent in film formability, water permeability, heat resistance, chemical resistance, and the like. Another object of the present invention is to provide a charged semipermeable composite membrane that can satisfactorily separate ionic substances.

0010

[Means for Solving the Problems] The present inventors have conducted extensive research in view of the above-mentioned problems. As a result, the present invention has been provided based on the knowledge that a composite membrane in which a thin layer of polyamine is present on the surface of a porous membrane through specific chemical bonds exhibits the desired performance. That is, according to the present invention, a thin layer of polyamine having a molecular weight of 500 or more is formed on the surface of a porous membrane made of an aromatic condensation polymer having halomethyl groups by chemical bonding through the halomethyl groups. A semipermeable composite membrane is provided.

[0011] In particular, the porous membrane serving as the base material in the composite membrane of the present invention has a thickness of about 5 μm or less on at least one surface.
A separation membrane is used that preferably has a dense layer of 1 μm or less and has an asymmetric structure with a porous interior, and generally has properties equivalent to an ultrafiltration membrane. In addition, aromatic condensation polymers that are materials for porous membranes include polysulfone, polyethersulfone, polyimide, polyetherimide, polyamide, polyphenylene oxide, poly-2, All conventional condensation polymers having an aromatic ring into which a halomethyl group can be introduced, such as 6-dimethylphenylene oxide and polyphenylene sulfide, are effective.

Such a porous membrane is prepared by dissolving an aromatic condensation polymer in a suitable solvent such as N-methyl-2-pyrrolidone, and adding polyvinylpyrrolidone, lithium chloride, potassium nitrate, etc. as necessary. A porous membrane is formed in any form such as a flat membrane, hollow fiber membrane, or tubular membrane by casting the solution onto a flat plate or extruding it from an annular nozzle and using a phase inversion method in a poor solvent. A membrane can be obtained. In addition, in the case of flat membranes and tubular membranes,
Using a woven fabric, non-woven fabric, net, etc. as a reinforcing packing material, a solution of the above-mentioned aromatic condensation polymer is used.
A porous membrane with excellent mechanical strength and dimensional stability can be obtained.

Next, a halomethyl group is introduced into the porous membrane made of the aromatic condensation polymer by a halomethylation reaction using an appropriate solvent or a gas phase reaction. Of course, a porous membrane can also be obtained in the same manner as above using an aromatic condensation polymer into which halomethyl groups have been introduced in advance. The halomethylation reaction is generally carried out using a halomethyl ether such as chloromethyl methyl ether as a halomethylation agent, and ZnCl2, SnCl4, TiCl4 as a catalyst.
, AlCl3, etc. are used as catalysts. When the aromatic condensation polymer is halomethylated in advance before film formation, in order to achieve uniform halomethylation, for example, 1,2-dichloroethane is used as a solubilizer or swelling agent for the aromatic condensation polymer. , halogenated hydrocarbons such as tetrachloroethane are preferably used. The degree of halomethylation in such a halomethylated aromatic condensation polymer is generally preferably introduced at a rate of 1 to 10% by weight, expressed as a halogen content measured by elemental analysis. In addition, the number of halomethyl groups introduced per repeating unit of the aromatic condensation polymer calculated from this halogen content is generally 0.
．． 01 to 2, preferably 0.01 to suppress expansion and contraction of the membrane, prevent cracks, etc., and obtain good durability.
~1.2 pieces, more preferably 0.01~0.4 pieces
The range is 5. In order to obtain the desired content of halomethyl groups with good reproducibility, by mixing an unmodified resin with a resin into which halomethyl groups have been introduced in an appropriate ratio, the amount of halomethyl groups in the entire resin used for film formation can be increased. Controlling the content of is also an effective method.

[0014] By 1H-NMR measurement, it can be confirmed that a halomethyl group has been introduced into the aromatic ring of the above polymer.

The semipermeable composite membrane which is the object of the present invention has a polyamine having a molecular weight of generally 500 or more attached to the surface of the asymmetric porous membrane having halomethyl groups by chemical bonding through the halomethyl groups. Generally a thin layer of 0.
This can be obtained by allowing the film to exist in a thickness of 1 μm or less. The polyamine in the present invention is a polymer having a molecular weight of generally 500 or more and having one or more primary, secondary or tertiary amino groups in the polymer. in particular,
Particularly preferred is linear or branched polyethyleneimine, but also polyvinylamine, polyallylamine, a partial reaction product of polyethyleneimine and ethylene oxide,
Partial reactants of polyethyleneimine and propylene oxide, condensates of aniline and formalin, and reactants of polybenzyl chloride and ammonia and/or primary and secondary amines are suitable. Polyethyleneimine that is generally commercially available as an aqueous solution can be used as it is. Usually the molecular weight is 500 or more, 1,000
,000 or less, a range of 10,000 to 100,000 is particularly preferred.

In the present invention, a composite membrane in which a thin layer of polyamine is formed on the surface of a porous membrane is prepared by contacting the membrane with a solution of polyamine dissolved in water or a solvent at room temperature or under heating. It is obtained by a method of chemically bonding primary, secondary, and tertiary amino groups with halomethyl groups of the membrane to form secondary, tertiary, and quaternary groups, respectively. The polyamine solution generally contains 0.1% to 10% by weight,
Particularly suitable is a range of 0.2% by weight to 8% by weight. When using commercially available polyethyleneimine, the resin is available as a 30-99% aqueous solution, so it can be used as a solution diluted to the above concentration range using water as a solvent. It is also possible to use a part or all of it by replacing it with a water-miscible solvent such as an alcohol. In addition, the pH value of such a polyethyleneimine solution needs to be in a basic region where amino groups do not protonate, and if necessary, add sodium hydroxide or the like to adjust the pH value of the solution to 7 or more, preferably 9 to 9. 1
It is recommended to keep it at 2.

Methods for bringing the porous membrane into contact with the polyamine solution include, for example, floating the membrane on the polyamine solution, casting the polyamine solution on the membrane, spraying the polyamine solution, or placing the membrane in contact with the polyamine solution. Examples include a method of soaking for a certain period of time. Furthermore, the contact temperature ranges from room temperature to 150°C, preferably 50°C.
It is desirable to heat at a temperature of .degree. C. to 90.degree. C. for a certain period of time. The time required for heating is from 1 minute to 24 hours or more, preferably from 5 minutes to 60 minutes. By using a compound having one or more functional groups capable of crosslinking polyamine with its amino group, such as a jupoxy compound, aldehydes, diisocyanate compound, dihalogen compound, etc., a covalent crosslinking structure is imparted through the amino group. , a semipermeable composite membrane with excellent chemical resistance and heat resistance can be obtained. It is also effective to impart an ionic crosslinked structure using a polybasic acid crosslinking agent such as sulfuric acid, phosphoric acid, citric acid, or malonic acid. The solvent for dissolving these crosslinking agents is preferably water, methanol, or a mixture thereof, but is not particularly limited as long as it does not dissolve the porous membrane and the thin layer of polyamine and dissolves the crosslinking agent. . The concentration of the crosslinking agent solution can be arbitrarily selected depending on the type of crosslinking agent and the solvent used.
Preferably it is 0.05% to 35% by weight.

Furthermore, the composite membrane of the present invention can be treated with, for example, hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, formic acid, acetic acid, etc. to protonate the amino groups of the polyamine of the membrane, thereby imparting a positive charge to the semipermeable membrane. Composite membranes are also useful. That is,
By using the charged semipermeable composite membrane of the present invention to filter a solution containing charged and uncharged molecules with similar molecular weights or molecular diameters, only the uncharged molecules permeate. However, since it is possible to perform separations in which positively charged molecules remain or only negatively charged molecules pass through while uncharged molecules remain, it is extremely effective, for example, in the separation of biopolymers.

[0019]

EXAMPLES Examples and comparative examples of the present invention will be shown below, but the present invention is not limited to these examples.

[0020] The water permeability shown in Examples and Comparative Examples is the flux measured at an operating pressure of 4 kg/cm2 using pure water, and the permeability is the flux measured using pure water at an operating pressure of 4 kg/cm2.
Measurements were made using a monodispersed aqueous solution (concentration 1,000 ppm) of EG), and the rejection rate (%) was calculated using the following formula, and the molecular weight of standard PEG with which the rejection rate was 90% or more was defined as the molecular weight cutoff.

Example 1 Repeating unit represented by the following formula obtained from Amoco Chemical Japan

[0022]

[Chemical formula 1]

Polysulfone (trade name: Ude
l Polysulfone, weight average molecular weight 35,
000) was uniformly dissolved in 570 g of dichloroethane under a nitrogen atmosphere at 50°C while heating and stirring, and then 21 g of chloromethyl methyl ether and 4.2 g of zinc chloride were dissolved.
was added and reacted at 50° C. for 8 hours with stirring. Next, the reaction solution was cooled to 30°C, precipitated in a large amount of methyl alcohol, dried under reduced pressure, and dissolved in chloroform.
It was reprecipitated, purified, and used for membrane production. The obtained chloromethylated polysulfone has a chlorine content of 7.5% by weight as measured by elemental analysis, and the amount of chlormethyl groups introduced per repeating unit of the polysulfone calculated from this content is calculated from this content. The number is 1.
There is one. Furthermore, 4. evaluated by 1H-NMR method.
The concentration of methylene groups at 57 ppm was consistent with that of chloromethylation. From these analysis results, the structure of chloromethylated polysulfone was identified as the following formula.

[0024]

[Case 2]

(wherein a+b=1) 30 g of the above chloromethylated polysulfone, 5 g of polyvinylpyrrolidone having a weight average molecular weight of 40,000, and N
After stirring a mixture of 150 g of -methyl-2-pyrrolidone at room temperature for 10 hours, a solution with a viscosity of 30 poise was obtained. Next, this solution was spread on a glass plate by approximately 300 μm.
A chloromethylated polysulfone membrane with a thickness of about 100 μm was obtained by casting the film to a thickness of 100 μm and solidifying it by immersing it in pure water at 10° C. The permeation flux of pure water was measured for this chloromethylated polysulfone membrane, and the result was 1260 liters/m2·hr. In addition, a monodisperse aqueous solution of PEG with a weight average molecular weight of 21,000 (concentration 1.0
As a result of measuring the permeability of 00ppm), the rejection rate was 98%.
Met. Similarly, the weight average molecular weights are 12 and 6, respectively.
As a result of measuring the permeability of monodispersed aqueous solutions of PEG 00 and 7,100, the rejection rates were 56% and 3%, respectively.

Next, using a chloromethylated polysulfone membrane, with the membrane surface of the dense layer facing down, 50% of the solution was placed on the surface of various polyethyleneimine solutions prepared under the specified conditions shown in Table 1.
A floating reaction was carried out at ℃ for 1 hour to obtain a polyethyleneimine-chloromethylated polysulfone composite membrane. After that, it was thoroughly washed with water. Table 1 shows the results of measuring the permeation flux of pure water and the permeability of aqueous PEG solution for the obtained composite membranes.

[0027]

[Table 1]

Furthermore, No. 1 in Table 1. The composite membrane obtained in step-10 was immersed in a 2% by weight potassium chromate solution adjusted to pH 2, and the amino groups of polyethyleneimine were protonated and ion-exchanged with chromate ions. As a result of observing the cross section of the membrane using an analyzer, a distribution of chromium with a thickness of about 0.05 μm was confirmed in the surface layer of the membrane. Further, as a result of observing the cross section of the membrane using a scanning electron microscope, a layer having a thickness of about 0.05 μm and having a denser structure was observed on the dense layer of the chloromethylated polysulfone membrane. In addition, this composite membrane was
When the film was immersed in pyrrolidone, it dissolved instantly and the film could not maintain its shape.

Comparative Example 1 Using the same polysulfone as in Example 1, a film was formed under the same conditions as in Example 1 without being subjected to chloromethylation treatment. The pure water permeation flux of this membrane is 1150 liters/
m2・hr, and the rejection rate is when the weight average molecular weight is 2100
9 for 0, 12600, 7100 PEG, respectively
They were 7%, 53%, and 1%.

[0030] Next, this polysulfone membrane was
．． The treatment was carried out under the same conditions as in Example 1 using the same polyethyleneimine solution as in -10. The pure water permeation flux of the obtained membrane was 1090 liters/m2・hr, and the rejection rate was 21000, 12600, 71
97% and 5 for 00,4250 PEG, respectively.
They were 2%, 2%, and 0%. Further, when this X film was treated with an aqueous potassium chromate solution and the cross section of the film was observed using an X-ray microanalyzer, the presence of chromium could not be confirmed.

Example 2 No. 1 in Table 1 in Example 1. In order to impart a covalent crosslinked structure to the polyethyleneimine-chloromethylated polysulfone composite membrane obtained in -10, the composite membrane was immersed in a 0.5% by weight glutaraldehyde aqueous solution at 50°C for 10 hours, and then washed with water. . Regarding the composite membrane obtained through such treatment, the pure water permeation flux was measured to be 62 liters/m2・hr, and the rejection rates of PEG aqueous solutions of various weight average molecular weights are as shown in Table 2. Met.

[0032]

[Table 2]

Next, in order to examine the heat resistance of the polyethyleneimine-chloromethylated polysulfone composite membrane having the above-mentioned crosslinked structure, the membrane was heated to 1.7 kg at 121°C.
/cm2 of high pressure steam for about 20 minutes. Using this treated composite membrane, the permeation flux and PEG
As a result of measuring the rejection rate, the pure water permeation flux was 61 liters/m2·hr, and the rejection rates of PEG of various average molecular weights were as shown in Table 3.

[0034]

[Table 3]

Example 3 Under the same conditions as in Example 2, various crosslinking agents were used to impart a crosslinked structure through covalent or ionic bonds to a polyethyleneimine-chloromethylated polysulfone composite membrane.

Table 4 shows the results of measuring the pure water permeation flux and the rejection rate of PEG of various average molecular weights for the types of crosslinking agents and the resulting composite membranes having crosslinked structures.

[0037]

[Table 4]

Example 4 Polyethyleneimine having a crosslinked structure obtained in Example 2
In order to investigate the positive charge effect of the chloromethylated polysulfone composite membrane, an aqueous solution (concentration 100
Table 5 shows the results of a permeation test (0 ppm).

[0039]

[Table 5]

Example 5 The polysulfone membrane obtained in Comparative Example 1 was immersed in a solution of 21 g of chloromethyl methyl ether and 4.2 g of zinc chloride dissolved in 570 g of methyl alcohol. After keeping the temperature of the solution at 50°C and reacting for 10 hours with stirring,
Washed with copious amounts of water or methyl alcohol. When a part of the membrane was sampled and elemental analysis was performed, the chlorine content was 0.074% by weight, and the number of chloromethyl groups introduced per polysulfone unit calculated from this content was 0.01. . Furthermore, 1H-
The methylene group appearing at 4.57 ppm evaluated by NMR method also showed a similar value, confirming that it was chloromethylated.

Next, the above-mentioned chloromethylated polysulfone membrane was placed with its dense layer side down, and the weight average molecular weight was 10.
0,000 in a 10% by weight aqueous solution of polyethyleneimine for 5 hours to obtain a polyethyleneimine-chloromethylated polysulfone composite membrane. At that time, the temperature was maintained at 60°C. After that, it was thoroughly washed with water. Regarding the obtained polyethyleneimine-chloromethylated polysulfone composite membrane, the permeation flux of pure water was measured to be 199 liters/m2·hr, and the weight average molecular weight was 147.
The rejection rate of monodisperse PEG with 0 was 92%. Further, the membrane was treated with an aqueous potassium chromate solution, and the cross section of the membrane was observed using an X-ray microanalyzer. As a result, a distribution of chromium with a thickness of about 0.02 μm was confirmed in the surface layer of the membrane. Further, as a result of observing the cross section of the membrane using a scanning electron microscope, a layer having a thickness of about 0.02 μm and having a denser structure was observed on the dense layer of the chloromethylated polysulfone membrane.

Example 6 In order to impart a covalent crosslinked structure to the polyethyleneimine-chloromethylated polysulfone composite membrane obtained in Example 5, a 1.0% by weight aqueous glutaraldehyde solution was heated at 70°C.
It was soaked in water for 2 hours and then washed with water. As a result of measuring the pure water permeation flux of the composite membrane having the crosslinked structure thus obtained, the result was 59 liters/m2・hr, and the rejection rate of aqueous solutions of PEG having various weight average molecular weights shown in Table 6 was , as shown in Table 6.

[0043]

[Table 6]

Example 7 Chloromethylated polysulfone was obtained in exactly the same manner as in Example 1 except that the time for the chloromethylation reaction was changed to 2 hours. This chloromethylated polysulfone has a chlorine content of 3.2% by weight as determined by elemental analysis, and the number of chloromethyl groups introduced per repeating unit of polysulfone calculated from this content is 0.4.
There are 2 pieces.

Next, a film was formed using the above-mentioned chloromethylated polysulfone in the same manner as in Example 1 to obtain a chloromethylated polysulfone film. The permeation flux of pure water was measured for this chloromethylated polysulfone membrane, and the result was 1,220 L/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous solution (concentration 1,000 ppm) of PEG having a weight average molecular weight of 21,000, the rejection rate was 99%. Similarly, the weight average molecular weight is 1
As a result of measuring the permeability of monodisperse aqueous solutions of PEG with 2,600 and 7,100, the rejection rates were 55% and 4, respectively.
%Met.

Next, using a chloromethylated polysulfone membrane, the surface of various polyallylamine solutions prepared under the predetermined conditions shown in Table 7 was heated at 40°C with the membrane surface of the dense layer facing down.
The reaction mixture was floated for 2 hours to obtain a polyallylamine-chloromethylated polysulfone composite membrane. Note that since polyallylamine is commercially available as a hydrochloride, it was dehydrochlorinated using a strongly basic ion exchange resin. Further, the pH of the solution was adjusted using sodium hydroxide. After the reaction, the mixture was thoroughly washed with water. The permeation flux of pure water and the permeability of aqueous PEG solution were measured for each of the obtained composite membranes. The results are shown in Table 7.

[0047]

[Table 7]

Furthermore, No. 7 in Table 7. The composite membrane obtained in -9 was immersed in a 2% by weight potassium chromate solution adjusted to pH 2, and the amino groups of polyallylamine were protonated and ion-exchanged with chromate ions.
As a result of observing the cross section of the membrane with an X-ray microanalyzer,
A distribution of chromium with a thickness of about 0.04 μm was confirmed on the surface layer of the film. Further, as a result of observing the cross section of the membrane using a scanning electron microscope, a layer having a thickness of about 0.04 μm and having a denser structure was observed on the dense layer of the chloromethylated polysulfone membrane.

Example 8 No. 7 in Table 7 in Example 7 In order to impart a covalent crosslinked structure to the polyallylamine-chloromethylated polysulfone composite membrane obtained in -9, 1.0% by weight of the composite membrane was added.
The sample was immersed in an aqueous glutaraldehyde solution at 60°C for 20 hours, and then washed with water. The pure water permeation flux of the composite membrane obtained through such treatment was measured to be 60L/m.
2.hr, and the inhibition rates of PEG aqueous solutions of various weight average molecular weights were as shown in Table 8.

[0050]

[Table 8]

Example 9 In order to investigate the heat resistance of the polyallylamine-chloromethylated polysulfone composite membrane having a crosslinked structure obtained in Example 8, the membrane was heated at 121° C. at 1.7 kg/kg.
After treatment with high-pressure steam of cm2 for about 20 minutes, the permeation flux of pure water and the rejection rate of PEG having a weight average molecular weight of 960 were measured. Furthermore, the same treatment was repeated and the membrane performance was measured in the same manner. The results are shown in Table 9.

[0052]

[Table 9]

Example 10 Under the same conditions as in Example 9, various crosslinking agents were used to impart a crosslinked structure through covalent or ionic bonds to a polyallylamine-chloromethylated polysulfone composite membrane. Table 10 shows the types of crosslinking agents and the results of measuring the pure water permeation flux and the rejection rate of PEG of various weight average molecular weights for the composite membranes having the obtained crosslinked structures.

[0054]

[Table 10]

Example 12 In order to investigate the effect of positive charge on the polyallylamine-chloromethylated polysulfone composite membrane having a crosslinked structure obtained in Example 9, a quaternary ammonium salt, which is a cationic substance, and an anionic substance were used. An aqueous solution of an organic acid (
Table 1 shows the results of a permeation test at a concentration of 1000 ppm).

[0056]

[Table 11]

Example 13 The chlorine content obtained in Example 1 and measured by elemental analysis was 7.5% by weight, and the number of chloromethyl groups introduced per repeating unit of polysulfone was calculated from this content. After stirring a mixture of 10 g of chloromethylated polysulfone, 20 g of unmodified polysulfone, 5 g of polyvinylpyrrolidone with a weight average molecular weight of 10,000, and 150 g of N-methyl-2-pyrrolidone at room temperature for 10 hours, A solution with a viscosity of 30 poise was obtained. Next, this solution was cast onto a polyester nonwoven fabric to a thickness of about 300 μm, and then immersed in pure water at 5° C. to solidify, thereby obtaining a chloromethylated polysulfone/polysulfone blend film with a thickness of about 100 μm. Ta. The number of chloromethyl groups introduced into the entire polysulfone resin component in this film was 0.37 per repeating unit of polysulfone. As a result of measuring the permeation flux of pure water for this chloromethylated polysulfone/polysulfone blend membrane, it was found to be 1,250 L/m2・hr.
Met. Further, as a result of measuring the permeability of a monodisperse aqueous solution (concentration 1,000 ppm) of PEG having a weight average molecular weight of 21,000, the rejection rate was 99%. Similarly, the weight average molecular weights are 12,600 and 7, respectively.
As a result of measuring the permeability of a monodisperse aqueous solution of PEG 100, the rejection rates were 57% and 7%, respectively.

Next, using the chloromethylated polysulfone/polysulfone blend membrane, the membrane surface of the dense layer was placed facing down on the surface of various polyethyleneimine solutions prepared under the predetermined conditions shown in Table 12 at 40°C. After floating reaction for a time, polyethyleneimine-chloromethylated polysulfone/
A polysulfone blend composite membrane was obtained. After the reaction, the mixture was thoroughly washed with water. The permeation flux of pure water and the permeability of aqueous PEG solution were measured for each of the obtained composite membranes. The results are shown in Table 12.

[0059]

[Table 12]

Furthermore, No. 1 in Table 12. The composite membrane obtained in -8 was immersed in a 2% by weight potassium chromate solution adjusted to pH 2, and the amino groups of polyethyleneimine were used as protonates to undergo ion exchange with chromate ions, and then an X-ray microanalyzer was used. As a result of observing the cross section of the membrane, it was confirmed that chromium was distributed in the surface layer of the membrane with a thickness of about 0.05 μm. Further, as a result of observing the cross section of the membrane using a scanning electron microscope, a layer having a thickness of about 0.05 μm and having a denser structure was observed on the dense layer of the chloromethylated polysulfone/polysulfone blend membrane.

Example 14 No. 1 in Table 12 in Example 13 In order to impart a covalent crosslinked structure to the polyethyleneimine-chloromethylated polysulfone/polysulfone blend composite membrane obtained in -8, the composite membrane was immersed in a 1.0% by weight glutaraldehyde aqueous solution at 60°C for 20 hours, Then, it was washed with water. Regarding the composite membrane obtained through such treatment, the pure water permeation flux was measured to be 63 L/m2・hr, and the rejection rates of PEG aqueous solutions of various weight average molecular weights are as shown in Table 13. there were.

[0062]

[Table 13]

Example 15 In order to examine the heat resistance of the polyethyleneimine-chloromethylated polysulfone/polysulfone blend composite membrane having a crosslinked structure obtained in Example 14, the membrane was exposed to a high pressure of 1.7 kg/cm2 at 121°C. It was treated with water vapor for about 20 minutes, and the permeation flux of pure water and the rejection rate of PEG having a weight average molecular weight of 960 were measured. Furthermore, the same treatment was repeated and the membrane performance was measured in the same manner. The results are shown in Table 14.

[0064]

[Table 14]

Example 16 Under the same conditions as in Example 15, various crosslinking agents were used to impart a crosslinked structure through covalent or ionic bonds to a polyethyleneimine-chloromethylated polysulfone/polysulfone blend composite membrane. Table 15 shows the types of crosslinking agents and the results of measuring the pure water permeation flux and the rejection rate of PEG of various weight average molecular weights for the composite membranes having the obtained crosslinked structures.

[0066]

[Table 15]

Example 17 In order to investigate the effect of positive charge on the polyethyleneimine-chloromethylated polysulfone/polysulfone blend composite film having a crosslinked structure obtained in Example 14, a quaternary ammonium salt, which is a cationic substance, and an anion were used. Table 16 shows the results of a permeation test for an aqueous solution (concentration 1000 ppm) of an organic acid, which is a chemical substance.

[0068]

[Table 16]

Example 18 Repeating unit expressed by the following formula

[0070]

[Chemical formula 3]

Polyetherimide (trade name:
Ultem 1000, manufactured by General Electric Company, weight molecular weight: 40,000) 100g dichloroethane 8
After uniformly dissolving the solution in 32 g under a nitrogen atmosphere at 50° C. while stirring, 67 g of chloromethyl methyl ether and 11 g of zinc chloride were added and reacted at 50° C. for 8 hours with stirring. Then, after cooling the reaction solution to 30°C,
It was precipitated in a large amount of methyl alcohol, dried under reduced pressure, dissolved in chloroform, reprecipitated, purified, and used for membrane production. The obtained chloromethylated polyetherimide has a chlorine content of 6.6% by weight as measured by elemental analysis, and the number of chloromethyl groups introduced per repeating unit of polyetherimide is calculated from this content. is 1.2 pieces. Furthermore, the concentration of methylene groups appearing at 4.56 ppm, which was evaluated by 1H-NMR method, matched, and it was confirmed that chloromethylation occurred. From these analysis results, the structure of chloromethylated polyetherimide was identified as the following formula.

[0072]

[C4]

(In the formula, a+b=1.2) 5.4% by weight of the above chloromethylated polyetherimide, 10.8% by weight of unmodified polyetherimide, weight average molecular weight 4
A mixture consisting of 2.7% by weight of N-methyl-2-pyrrolidone and 81.1% by weight of N-methyl-2-pyrrolidone was stirred at room temperature for 10 hours to obtain a film-forming solution with a viscosity of 25 poise. Next, using this solution, a hollow fiber membrane is extruded from an annular nozzle for producing hollow fibers, and pure water at 5°C is used as a coagulation liquid to coagulate from the inside and outside of the hollow fiber, and the chloromethylated polyetherimide/polyetherimide blend is A hollow fiber membrane having an inner diameter of 0.79 mm and an outer diameter of 1.3 mm was obtained. The number of chloromethyl groups introduced into the entire polyetherimide resin component in this hollow fiber membrane is 0.4 per repeating unit of polyetherimide.
It is individual. Using this chloromethylated polyetherimide/polyetherimide blend hollow fiber membrane,
A module with a diameter of 0 mm and 20 hollow fibers was manufactured, and the permeation flux of pure water was measured to be 750 L/m2·hr. Also, PE having a weight average molecular weight of 21,000
As a result of measuring the permeability of a monodispersed aqueous solution of G (concentration 1,000 ppm), the rejection rate was 99%. Similarly, the weight average molecular weights are 12,600 and 7,10, respectively.
As a result of measuring the permeability of a monodisperse aqueous solution of PEG with a
The inhibition rates were 65% and 8%, respectively.

Next, using the chloromethylated polyetherimide/polyetherimide blend hollow fiber membrane module, various polyethyleneimine solutions prepared under the predetermined conditions shown in Table 17 were poured into the hollow fiber membrane at 40°C for 2 hours. The mixture was circulated and reacted using a pump for a period of time to obtain a polyethyleneimine-chloromethylated polyetherimide/polyetherimide blend composite hollow fiber membrane. After the reaction, the mixture was thoroughly washed with water. The permeation flux of pure water and the permeability of aqueous PEG solution were measured for each of the obtained composite membranes. The results are shown in Table 17.

[0075]

[Table 17]

Furthermore, No. 1 in Table 17. - Disassemble the composite hollow fiber membrane module obtained in step 8, take out the composite hollow fiber membrane, and
After immersing it in a 2% by weight potassium chromate solution adjusted to H2 to protonate the amino groups of polyethyleneimine and ion-exchanging them with chromate ions,
As a result of observing the cross section of the membrane with an X-ray microanalyzer,
A distribution of chromium with a thickness of about 0.05 μm was confirmed in the inner surface layer of the hollow fiber membrane. In addition, as a result of observing the cross section of the hollow fiber membrane using a scanning electron microscope, it was found that the thickness of the inner dense layer of the chloromethylated polyetherimide/polyetherimide blend hollow fiber membrane was approximately 0.0 mm.
A layer of 0.05 μm was observed.

Example 19 No. 1 in Table 17 in Example 17 In order to impart a covalent cross-linked structure to the polyethyleneimine-chloromethylated polyetherimide/polyetherimide blend composite hollow fiber membrane obtained in step 8, 1.
A glutaraldehyde aqueous solution of % by weight was circulated and reacted at 60° C. for 20 hours using a pump, and then washed with water. Regarding the composite hollow fiber membrane module obtained through such treatment, the pure water permeation flux was measured to be 45 L/m2・h.
r, and the rejection rates of PEG aqueous solutions of various weight average molecular weights were as shown in Table 18.

[0078]

[Table 18]

Example 20 Regarding the polyethyleneimine-chloromethylated polyetherimide/polyetherimide blend composite hollow fiber membrane module having a crosslinked structure obtained in Example 19,
In order to investigate its heat resistance, the module was treated with high-pressure steam of 1.7 kg/cm2 at 121°C for about 20 minutes, and the permeation flux of pure water and PEG with a weight average molecular weight of 960
The inhibition rate was measured. Furthermore, the same treatment was repeated and the membrane performance was measured in the same manner. The results are shown in Table 19.

[0080]

[Table 19]

Example 21 Under the same conditions as in Example 20, various crosslinking agents were used to impart a crosslinked structure through covalent or ionic bonds to a polyethyleneimine-chloromethylated polyetherimide/polyetherimide blend composite hollow fiber membrane. I went. Table 20 shows the type of crosslinking agent and the pure water permeation flux of the composite membrane with the obtained crosslinked structure and PE of various weight average molecular weights.
The results of measuring the inhibition rate of G are shown.

[0082]

[Table 20]

Example 22 The polyethyleneimine-chloromethylated polyetherimide/polyetherimide blend composite hollow fiber membrane module having a crosslinked structure obtained in Example 19 was treated with a cationic substance in order to investigate the effect of its positive charge. Table 21 shows the results of a permeation test for an aqueous solution (concentration 1000 ppm) of a certain quaternary ammonium salt and an anionic organic acid.

[0084]

[Table 21]

Comparative Example 2 The chlorine content obtained in Example 1 and measured by elemental analysis was 7.5% by weight, and the number of chloromethyl groups introduced per repeating unit of polysulfone calculated from this content was 7.5% by weight. 1. A membrane made of 1 chloromethylated polysulfone was added to an aqueous solution of polyethyleneimine with a molecular weight of 10,000 at a concentration of 3% by weight and a pH of 10.
The mixture was immersed for 2 hours at a temperature of 0.degree. C. to react, thereby obtaining a polyethyleneimine-chloromethylated polysulfone membrane. After the reaction, the mixture was thoroughly washed with water. When the obtained membrane was immersed in N-methyl-2-pyrrolidone, there was no change in the shape of the membrane and it was found to be insoluble.

[0086] Next, a part of this membrane was cut out and the pH
After protonating the amino groups of polyethyleneimine and ion-exchanging them with chromate ions by immersing them in a 2% by weight potassium chromate solution adjusted to
As a result of observing the cross section of the membrane using a line microanalyzer, it was confirmed that chromium was distributed throughout the cross section of the membrane.

Further, this membrane was immersed in a 1.0% by weight aqueous glutaraldehyde solution at 60° C. for 20 hours, and then washed with water. The pure water permeation flux of the obtained membrane was measured and the result was 4.1 L/m2·hr, and the rejection rate of various PEG aqueous solutions having a weight average molecular weight of 960 was 97%.

In order to examine the heat resistance of this membrane, it was treated with high-pressure steam of 1.7 kg/cm2 at 121°C for about 20 minutes, and the permeation flux of pure water and the rejection rate of PEG with a weight average molecular weight of 960 were measured. It was measured. Furthermore, the same treatment was repeated and the membrane performance was measured in the same manner. As a result, no deterioration in performance was observed up to 4 treatments, but cracks occurred in the film by the 5th treatment, and PEG
The blocking rate was 0%.

Claims (2)

[Claims] Claim 1: A semi-permeable membrane in which a thin layer of polyamine having a molecular weight of 500 or more is formed on the surface of a porous membrane made of an aromatic condensation polymer having halomethyl groups through chemical bonding through the halomethyl groups. composite membrane 2. The semipermeable composite membrane according to claim 1, wherein the thin layer of polyamine has a crosslinked structure;
] The semipermeable composite membrane according to claim 1, wherein the amino groups of the polyamine are protonated.