JPS60255109A - Sulfonated polysulfone semipermeable membrane and its production - Google Patents

Abstract

PURPOSE:To obtain a semipermeable membrane having >=99% NaCl removing rate and having excellent resistance to chlorine, pH, heat, and compaction by sulfonating a linear polysulfone copolymer. CONSTITUTION:A linear polysulfone copolymer consisting of repeating units shown by formulas I and II in sulfonated to obtain the sulfonated polysulfone copolymer insoluble in water, having >=0.5cm<2>/g logarithmic viscosity in a soln. at 30 deg.C obtained by dissolving 0.5g polymer in 100ml N-methyl-2-pyrolidone, and having <=2meg/g ion exchange capacity. The polymer is dissolved in alkylene glycol monoalkylether or in a mixture of said solvent and a small amt. of nonprotonic polar organic solvent to obtain 0.01-15wt% polymer concn. soln. The soln. is used as a film-forming soln., and a film having 0.05-5mum thickness is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polysulfone composite semipermeable membrane and a method for producing the same, and more particularly to a semipermeable membrane comprising a homogeneous membrane of a sulfonated water-insoluble polysulfone copolymer and a method for producing the same.

A linear polysulfone copolymer having NiA and NiB as repeating units has already been described in Canadian Patent No. 847.963, and a sulfonated product of this copolymer has also been described in JP-A No. It is described in No. 55-48222. That is,
This publication states that by dissolving the polysulfone copolymer in concentrated sulfuric acid and sulfonating, substantially all of the repeating units of formula A are sulfonated, but substantially all of the repeating units of formula A are sulfonated. It has been described that a hydrophilic sulfonated polysulfone is produced in which the sulfonated polysulfone remains in a non-sulfonated state. Additionally, it is mentioned that this sulfonated polysulfone copolymer is potentially useful as an ultrafiltration membrane.

In addition, a sulfonated polysulfone consisting of 2〇 repeating units is disclosed in U.S. Patent No. 3
, 709,841, and published in Japanese Unexamined Patent Publication No. 1973
0-99973 and JP-A-51-146379 disclose that by applying a solution of such sulfonated polysulfone onto a dense layer on the surface of an anisotropic ultrafiltration membrane and evaporating the solvent, A method for manufacturing a composite semipermeable membrane for reverse osmosis in which a semipermeable thin membrane is laminated on an ultrafiltration membrane is described. Similarly, office of H
ater Re5archand Technolo
gy Department of the Inte
rior.

In Report No. 2001-20, an anisotropic ultrafiltration membrane consisting of repeating units of the above formula C was packed in advance with an aqueous lactic acid solution, and on this ultrafiltration membrane, the same repeating units of the above formula C were packed.
A method is described in which a composite semipermeable membrane is obtained by applying a solution of a sulfonated polysulfone consisting of repeating units of and evaporating the solvent.

However, the present inventors have discovered that a sulfonated polysulfone copolymer obtained by sulfonating a linear polysulfone copolymer having formulas A and 2B has better physical properties and properties than the composite semipermeable membrane described above. In particular, in preferred cases, it has a high sodium chloride removal rate of 99% or more in salt water treatment, as well as chlorine resistance and plating resistance.
The present invention was achieved by discovering that it is possible to obtain a reverse osmosis membrane with excellent hydrogen resistance, heat resistance, and compaction resistance.

Therefore, the present invention aims to provide a semipermeable membrane made of a sulfonated polysulfone copolymer, and further aims to provide a method for treating an aqueous liquid using such a semipermeable membrane.

The sulfonated polysulfone semipermeable membrane according to the present invention is obtained by sulfonating a linear polysulfone copolymer consisting of repeating unit A and repeating unit B.
The logarithmic viscosity measured at a temperature of 30°C for a solution containing 15 g is 0.5 cn! /g or more and an ion exchange capacity of 2 milliequivalents/g or less.

Further, according to the present invention, such a semipermeable membrane can be obtained by dissolving the above-mentioned sulfonated polysulfone copolymer in an alkylene glycol monoalkyl ether which may contain a small amount of an aprotic polar organic solvent. It is manufactured by coating this on a suitable base material and evaporating the solvent.

The sulfonated polysulfone copolymer used in the present invention can be easily obtained by dissolving the polysulfone copolymer described above in concentrated sulfuric acid and stirring at room temperature for several hours. Regarding the degree of sulfonation, as mentioned above, substantially all of the repeating units of 2A are sulfonated, but
Substantially all of the repeating units of NiB remain in a non-sulfonated state, so it can be easily controlled by using a copolymer in which the ratio of the repeating units of Formula A and NiB is varied. Moreover, by controlling the sulfonation conditions, the sulfonation itself of the repeating unit of formula A can also be controlled.

In the present invention, such a sulfonated polysulfone copolymer has an ion exchange capacity of 2 meq/g or less per 1 g of dry resin, and 0.5 g of this copolymer is added to 100 ml of N-methyl-2-pyrrolidone. @For the dissolved solution, the logarithmic viscosity measured at 30°C (hereinafter, the method for measuring the logarithmic viscosity of sulfonated polysulfone is the same) is 0.5 cJ / g or more, preferably 0.7
It is necessary that it is at least cJ/g. When the ion exchange capacity exceeds 2 milliequivalents/g, the sulfonated polysulfone becomes water-soluble and is unsuitable as a semipermeable membrane that often treats liquids containing aqueous media, and the logarithmic viscosity is 0. This is because when it is smaller than '5 cJ/g, it is difficult to form a uniform thin film without defects such as pinholes.

The sulfonic acid group possessed by the sulfonated polysulfone copolymer used in the present invention is represented by the formula -303M, where M represents hydrogen, an alkali metal, or a tetraalkylammonium. For example, by sulfonating a polysulfone copolymer, washing the sulfonated polysulfone copolymer with water, and drying it, a sulfonated polysulfone copolymer having free sulfonic acid groups can be obtained. Furthermore, by treating this sulfonated polysulfone copolymer with an aqueous solution, methanol, ethanol solution, etc. of alkali metal hydroxide or alkali metal alcohol-1, the sulfonic acid group can be converted into an alkali metal salt. As the alkali metal hydroxide, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. are used, and as the alkali metal alcoholade, for example, sodium methylate, potassium methylate, potassium ethylate, etc. are used.

In addition, if a tetraalkylammonium, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. is treated with the same solution as above, the corresponding tetraalkylammonium salt can be obtained. be able to.

The semipermeable membrane according to the present invention can be produced by various methods, but usually, the sulfonated polysulfone is dissolved in an organic solvent to prepare a membrane-forming solution, and this is coated on an appropriate support substrate. It can be produced by evaporating the solvent.

The organic solvent for preparing the membrane forming solution includes 0 dimethyl sulfoxide, N-methyl-2-pyrrolidone,
Aprotic polar organic solvents such as N,N-dimethylformamide and N,N-dimethylacetamide, and alkylene carbon atoms such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples include alkylene glycol monoalkyl ethers having 2 or 3 carbon atoms and an alkyl group having 1 to 4 carbon atoms. Depending on the sulfonated polysulfone copolymer used, it may not dissolve in the alkylene glycol monoether or may only swell; It dissolves well in a mixed solvent containing an aprotic polar organic solvent.

Using alkylene glycol monoalkyl ether or a mixed solvent of alkylene glycol monoalkyl ether and a small amount of the aprotic polar organic solvent as the solvent for the membrane forming solution 1. In the evaporation removal of the solvent described later, the solvent can be evaporated at room temperature or by slight heating. This is advantageous because it can be removed and a uniform thin film without defects can be obtained.

The concentration of the sulfonated polysulfone copolymer in the membrane forming solution is also related to the thickness of the semipermeable membrane obtained, but is usually 0,
A range of 0.01 to 15% by weight is preferred, particularly 0.1 to 1% by weight.
A range of 0% by weight is preferred.

The base material for applying the film-forming solution is not particularly limited, but
For example, materials with smooth surfaces made of glass, stainless steel, aluminum, polyethylene resin, polypropylene resin, etc. are preferably used. Heating may be applied if necessary to evaporate the solvent. The heating temperature may be appropriately selected depending on the solvent used. Incidentally, in order to promote evaporation of the solvent after coating the film-forming solution on the substrate, the film-forming solution may be heated in advance.

The semipermeable membrane according to the invention can then be obtained by evaporating the solvent from the membrane forming solution applied onto the support substrate. After the solvent has been evaporated and removed, the membrane can be easily peeled off from the supporting substrate by immersing the supporting substrate in water.

The thickness of the resulting semipermeable membrane depends on the concentration of the sulfonated polysulfone copolymer in the membrane-forming solution and the thickness of the coating of the membrane-forming solution on the supporting substrate, but the thinner the membrane is, the higher the water permeation rate. Often, the thicker the better for strength. Therefore, although not particularly limited, the film thickness is usually in the range of 0.05 to 5 μm.

The semipermeable membrane of the present invention obtained in this way has no anisotropy, is homogeneous in the thickness direction, has excellent chlorine resistance, pH resistance, heat resistance, etc., and is suitable for reverse osmosis membranes. Further, the semipermeable membrane according to the present invention can be used continuously for a long period of time without becoming compacted.
Maintain the initial high water permeation rate.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In the examples, the solute removal rate and water permeation rate of the obtained semipermeable membrane were measured by conducting an i3 filtration experiment at a temperature of 25°C and a pressure of 50 kg/cJ using an aqueous sodium chloride solution with a concentration of 5000 ppm3 as a stock solution. , were determined by the following formulas.

Example 1 11) Production of polysulfone copolymer A linear polysulfone copolymer consisting of 57 mol% of repeating units of formula A1 and 43 mol% of repeating units of NiB was prepared according to the method described in Japanese Patent Publication No. 46-21458. A polymer was produced.

That is, 4,4'-dihydroxydiphenylsulfone 15
, Og (0.06 mol) and hydroquinone 8.8 g (0
, 08 mol) was placed in a flask equipped with a stirrer, a nitrogen gas inlet tube, a water drain tube and a thermometer, and 200 ml of sulporan and 100 ml of xylene were added thereto.

155 while stirring while heating with a mantle heater.
Refluxing was carried out at ℃ for 1 hour, during which time 5.6 ml of water was extracted.

Next, the temperature was lowered to 110° C., and 40.2 g (0.14 mol) of 4,4°-dichlorodiphenylsulfone and 27.6 g (0.20 mol) of potassium carbonate were added to start the polymerization reaction. After refluxing at 162°C for 1 hour, the temperature was raised to 200°C while removing water for 2.5 hours, and then heated for 2.5 hours.
Refluxing was continued for 4 hours at 00-215°C. The amount of water drawn off during this reaction was 2.0 ml.

After confirming that a film could be formed when a portion of the reaction solution was applied to a glass plate and immersed in water, the temperature was lowered to 100° C. and 20 ml of dichloromethane was added. The reaction mixture thus obtained was poured into pure water to coagulate the polysulfone copolymer, washed with pure water and then with acetone, and then dried at 80° C. for 6.5 hours.

5 The polysulfone copolymer thus obtained (yield: 1
00%) is a pale yellow particulate matter, and this (7)
Logarithmic viscosity measured at 30°C as a solution dissolved in 100 ml of polymer N-methyl-2-pyronidone (hereinafter, the measurement conditions for the logarithmic viscosity of the polysulfone copolymer are the same).

) was 0.84 cJ/g.

(2) Production of sulfonated polysulfone copolymer 10 g of the polysulfone copolymer obtained as described above was dissolved in 97% concentrated sulfuric acid 801, stirred at room temperature for 4 hours, and a blackish brown viscous mixture was obtained. A reaction solution was obtained. This was placed in a water bath to solidify the sulfonated polysulfone copolymer. After washing with water, 0.5N sodium hydroxide aqueous solution 8
00ml overnight. Next, the polymer was washed until the washing solution became neutral, and then vacuum-dried at 60° C. for 5 hours.

The pale yellow particulate sulfonated polysulfone copolymer thus obtained has an logarithmic viscosity of 0.84 ctl/g,
The ion exchange capacity was 1.23 meq/g.

6 (3) Production of semipermeable membrane 8 g of the sulfonated polysulfone copolymer obtained as described above was dissolved in 110 g of N,N-dimethylformamide, and foreign matter was removed using a filter paper with a pore size of 10 μm to obtain a uniform product. A membrane solution was prepared. This film-forming solution was cast onto a glass plate heated to 60° C. with a gap of 55 μm, and hot air was blown onto the coating film on the glass plate using a hot air dryer to evaporate and remove the solvent. The glass plate was immersed in water, and the membrane was peeled off from the glass plate and scooped onto a polysulfone ultrafiltration membrane as a support membrane. The thickness of the semipermeable membrane was 0.3 μm.

An aqueous orange solution with a concentration of 50 ppm was applied to the surface of this semipermeable membrane, and since the polysulfone ultrafiltration membrane was not colored, it was confirmed that the semipermeable membrane had no defects such as pinholes.

(4) Evaluation of membrane properties The sulfonated polysulfone semipermeable membrane peeled off from the glass plate in water as described above was scooped up onto a polysulfone ultrafiltration membrane, and a permeation experiment was conducted under the conditions described above. The results are shown in Table 1.

Example 2 Repeating unit A1 and repeating unit B were prepared in the same manner as in Example 1.
Linear polysulfone copolymers with various composition ratios were prepared and sulfonated to obtain semipermeable membranes. The membrane performance of the semipermeable membrane thus obtained is shown in Table 1.

Example 3 A membrane forming solution was prepared by dissolving 0.1 g of the partially sulfonated polysulfone obtained in Example 1 in 10 g of ethylene glycol monomethyl ether and removing foreign matter using a 10 μm filter paper. This was cast onto a glass plate at a temperature of 25°C with a gap of 55 μm, left for 30 minutes, and
The solvent was removed by heating at °C for 30 minutes. Next, the glass plate was immersed in water, and the film was peeled off from the long glass plate. The thickness of this film was 0.2 μm.

The performance of this membrane is a removal rate of 99.3% and a water permeation rate of 0°9r.
It was d/day.

Example 4 8 0.1 g of the sulfonated polysulfone copolymer consisting of 17 mol% repeating unit A and 83 mol% repeating unit B obtained in Example 2 was mixed with 10 g of ethylene glycol monomethyl ether and N,N- Dimethylformamide 0.1g
A membrane forming solution was prepared by dissolving the mixture in a solvent and removing foreign matter using a 10 μm filter paper.

This was cast onto a glass plate at a temperature of 25°C with a gap of 55μm, left for 30 minutes, and further coated at 80°C for 1 hour.
The solvent was removed by heating for an hour. Next, the glass plate was immersed in water to peel off the film from the glass plate. The thickness of this film was 0.2 μm.

The performance of this membrane is that the removal rate is 99.8% and the water permeation rate is 0.15.
rI? /rrf・day.

Example 5 In Example 1, the polysulfone copolymer was sulfonated, the reaction solution was put into a water bath, the sulfonated polysulfone copolymer was coagulated, and after washing with water, it was washed with 0.5N aqueous sodium hydroxide solution. 60° without any processing
It was dried at C for 6 hours.

A membrane forming solution was prepared by dissolving 0.1 g of this sulfonated polysulfone copolymer in 10 g of ethylene glycol monomethyl ether and removing foreign matter using a filter paper with a pore size of 10 μm.

At a temperature of 25°C, this film-forming solution was spread on a glass plate for 5 minutes.
Cast coating with a gap of 5 μm, and keep it at an ambient temperature of about 30 μm.
The solution was allowed to stand for a minute to evaporate the solvent.

The membrane was peeled off from the glass plate by immersing it in water. The thickness of this film is 0.4 μm, and the removal rate is 98.5%.
, the water permeation rate was 1.1 rrr/rrr·day.

Comparative Example 2 Polysulfone having the repeating unit (P manufactured by ICr)
-1700) by the method of No5hay et al. (J.

Applied Polymer Sci, 20.
1885 (1976)).

That is, 60 g of the above polysulfone was dissolved in 300 ml of 1,2-dichloroethane to prepare a polysulfone solution. Separately, 11.5 ml (0.07 mol) of triethyl phosphate and 83 ml of 1,2-dichloroethane were placed in a 200 ml Erlenmeyer flask with a stopcock, and 6 ml (0.16 mol) of sulfur trioxide was added to this while stirring while cooling in a water bath. ) to prepare a sulfur trioxide solution.

1,2-Dichloroethane 120111 was placed in a flask equipped with a stirrer, two dropping funnels, and a calcium chloride tube, and while stirring, the above polysulfone solution was poured into one dropping funnel and the above sulfur trioxide solution was poured into the other dropping funnel. The mixture was added dropwise into the flask over a period of time, and stirring was continued for 2 hours at room temperature. Thereafter, it was washed with isopropyl alcohol and then with pure water, and then dried at 90°C for 13 hours.

The sulfonated polysulfone copolymer thus obtained (yield 75%) had a logarithmic viscosity of 0.91 CI/g and an ion exchange capacity of 1.0 meq/g.

Using this sulfonated polysulfone, a semipermeable membrane with a thickness of 0.3 μm was prepared in the same manner as in Example 1. The performance of this membrane is as follows: removal rate 98.2%, water permeation rate 0.6n (/rd
・It was day.

Example 6 A polysulfone consisting of 43 mol% of the repeating unit of formula A2 and 57 mol% of the repeating unit of 2B was prepared in the same manner as in Example 1 except that resorcinol was used instead of hydroquinone. Preparing the copolymer, Example 1
This was sulfonated in the same manner as above, and the logarithmic viscosity was 1. Oc
A sulfonated polysulfone copolymer having an ion exchange capacity of 1.03 meq/g and an ion exchange capacity of 1.03 meq/g was obtained.

Using this sulfonated polysulfone copolymer, a semipermeable membrane having a thickness of 0.2 μm was prepared in the same manner as in Example 1. The membrane performance was a removal rate of 99.3% and a water permeation rate of 0°8 d/d·day.

Example 7 A polysulfone copolymer consisting of 57 mol% of repeating units of 3 and 43 mol% of repeating units of 2B was produced in the same manner as in Example 1, except that catechol was used instead of hydroquinone. Example 1
This was sulfonated in the same manner as , and the logarithmic viscosity was 0.9.
c+a/g, ion exchange capacity 1.32 meq/g
A sulfonated polysulfone copolymer was obtained.

Using this sulfonated polysulfone copolymer, a semipermeable membrane having a thickness of 0.3 μm was prepared in the same manner as in Example 1. The membrane performance was a removal rate of 98.4% and a water permeation rate of 1°4♂/day.

Example 8 Table 2 4 (Consolidation Resistance) The semipermeable membrane obtained in Example 1 was subjected to continuous permeation experiments of an aqueous sodium chloride solution under the same conditions as in Example 1 to examine changes in membrane performance over time. It was measured. As the results are shown in Table 2, the membrane performance did not change over time and no consolidation of the membrane occurred.

(Evaluation of heat resistance) The semipermeable membrane obtained in Example 1 was immersed in hot water at 95° C. for 30 minutes, and the removal rate and water permeation rate were measured. Furthermore, the removal rate and water permeation rate were measured in the same manner by repeating the process of immersing the sample in hot water for 30 minutes. The results are shown in Table 3. The semipermeable membrane according to the present invention does not substantially change its membrane performance even after repeated immersion in hot water, and therefore can be suitably used for treating high temperature liquid mixtures.

(Acid resistance) The semipermeable membrane obtained in Example 1 was immersed in distilled water for 2 hours,
Next, after being immersed in a 0.5N hydrochloric acid aqueous solution at 25° C. for 2 hours, the membrane performance was measured with respect to a sodium chloride aqueous solution under the same conditions as in Example 1. Removal rate is 98.6%, water permeation rate is 1.2r+? /rrr·day, and there was virtually no change. Therefore, it is understood that the semipermeable membrane of the present invention has excellent acid resistance.

(Alkali resistance) The semipermeable membrane obtained in Example 1 was immersed in distilled water for 2 hours,
Next, the film was immersed in a 0.5 N aqueous sodium hydroxide solution at 25° C. for 2 hours, and then the membrane performance with respect to the aqueous sodium chloride solution was measured under the same conditions as in Example 1. Removal rate is 98
．． 4%, and the water permeation rate was 1.36/rrl·day, which was virtually unchanged. Therefore, it is understood that the semipermeable membrane of the present invention has excellent alkali resistance.

(Drying resistance) The semipermeable membrane obtained in Example 1 was immersed in distilled water for 2 hours,
Then, after drying at 25° C. for 2 hours, the membrane performance with respect to an aqueous sodium chloride solution was measured under the same conditions as in Example 1. Removal rate is 98.5%, water permeation rate is 1.2 rrr/r
rf.day, with virtually no change. Therefore,
It is understood that even after the semipermeable membrane of the present invention has been dried, if it is rewetted, it will have the same membrane performance as the original.

Patent applicant: Nitto Electric Industry Co., Ltd. Agent Patent Attorney Itsu Makino Department 7

Claims (6)

[Claims] (1) A linear polysulfone copolymer consisting of repeating unit A and repeating unit B is sulfonated.
．． The logarithmic viscosity measured at a temperature of 30 ° C. for a solution in which 5 g is dissolved is 0.5 cJ / g or more, and
A semipermeable membrane made of a water-insoluble sulfonated polysulfone copolymer having an ion exchange capacity of 2 milliequivalents/g or less. (2) Semi-transparent sulfonated polysulfone according to claim 1, wherein the sulfonated polysulfone copolymer consists of 10 mol% or more of repeating units A and 90 mol% or less of repeating units B. film. (3) Claim 1, characterized in that the sulfonic acid group possessed by the sulfonated polysulfone copolymer is represented by the formula -3o3M (where M represents hydrogen, an alkali metal, or tetraalkylammonium). Or the sulfonated polysulfone semipermeable membrane according to item 2. (4) A linear polysulfone copolymer consisting of repeating unit A and repeating unit B is sulfonated, and 0 ml of N-methyl-2-pyrrolidone is added to 1°Oml of N-methyl-2-pyrrolidone.
．． A water-insoluble sulfonated polysulfone copolymer having a logarithmic viscosity of 0.5 all'/g or more and an ion exchange capacity of 2 milliequivalents/g or less when measured at 30°C for a solution containing 5 g of , a sulfone characterized by dissolving it in an alkylene glycol monoalkyl ether which may contain a small amount of an aprotic polar organic solvent to obtain a film-forming solution, applying this onto a suitable substrate, and evaporating the solvent. polysulfone semipermeable membrane. (5) The sulfonated polysulfone semi-transparent copolymer according to claim 4, characterized in that the sulfonated polysulfone copolymer consists of 10 mol% or more of repeating units A and 90 mol% or less of repeating units B. Membrane manufacturing method. (6) Claim 4, characterized in that the sulfonic acid group possessed by the sulfonated polysulfone copolymer is represented by the formula -303M (where M represents hydrogen, an alkali metal, or tetraalkylammonium). Or the method for producing a sulfonated polysulfone semipermeable membrane according to item 5.