JPS5969107A - Production of composite semipermeable membrane - Google Patents

Abstract

PURPOSE:To produce easily a composite semipermeable membrane having high performance by forming a film of PVA, etc. on one surface of a porous substrate, and bringing a water soluble polymer, etc. contg. a carboxylic group into reaction with said film in the presence of an insolubilizing catalyst. CONSTITUTION:An aq. soln. of PVA or partially hydrolyzed matter of polyvinyl acetate (>=70mol% degree of saponification) is stuck to one surface of a porous substrate (for example, polytetrafluoroethylene, etc.) and is dried, thereby forming a thin layer. An aq. soln. contg. a water soluble polymer contg. a carboxylic group (for example, a copolymer of polyacrylic acid and maleic anhydride, etc.) or the univalent water soluble chloride thereof and the insolubilizing catalyst thereof (for example, esterified catalyst, etc.) is stuck to the thin layer, and is heated to cause reaction, thereby forming an insolubilized film. The composite reverse osmosis membrane having excellent rate of water permeation and rate of desalting is obtd.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a composite semipermeable membrane.

Generally, when a semipermeable membrane is interposed between a solution and a solvent and a pressure greater than osmotic pressure is applied to the solution side, the phenomenon in which the solvent on the solution side diffuses into the solvent side through the semipermeable membrane is called reverse osmosis.
Although they are used in a wide range of fields such as seawater and brine desalination and wastewater treatment, many conventional semipermeable membranes are still unsatisfactory in terms of water permeability, selective permeability, strength, durability, heat resistance, etc. It should not be done, and there have been various proposals regarding its manufacturing method.

Furthermore, semipermeable membranes are generally manufactured by casting an odor liquid made of an organic polymer as an odor material, an organic solvent, water, a swelling agent, etc.; Due to the use of boiling point organic solvents and expensive organic solvents such as N-methyl-2-pyrrolidone, h,h-v methylacetamide, harmful solvent vapors are generated during the manufacturing process. However, there were also drawbacks such as the product being expensive.

The present invention has been made in consideration of the above points, and
It is an object of the present invention to provide a method for easily manufacturing a composite semipermeable membrane having high performance without requiring strict control of manufacturing conditions.

The first method for producing a composite semipermeable membrane according to the present invention is to form a membrane of partially saponified polyvinyl alcohol polyvinyl acetate (hereinafter, these may be collectively referred to as polyvinyl alcohol, etc.) on one side of a porous support. Then, a carboxyl group-containing water-soluble polymer or its monovalent water-soluble salt compound (hereinafter, these may be collectively referred to as a carboxyl group-containing polymer, etc.) is reacted with the membrane in the presence of an insolubilization catalyst. Second, a film of a carboxyl group-containing polymer or its monovalent salt compound is formed on one side of the porous support, and then a film of a polyvinyl alcohol or polyvinyl acetate moiety is formed on one side of the porous support. The method is characterized in that a saponified product is reacted with the polymer film in the presence of an insolubilization catalyst to form an insolubilized film.

The porous support used in the present invention can be any type of porous support that has been conventionally used in the production of composite reverse osmosis membranes, such as cellulose ester, polystyrene, polyester, Polysulfone, FRP, polytetrafluoroethylene, polychlorotrifluoroethylene, polyhexafluoropropylene,
In addition to porous polymer supports such as copolymers of these fluorinated olefins, porous glass, sintered metal, ceramics, etc. may be mentioned, but polytetrafluoroethylene and polysulfone porous supports are preferred.

In particular, a polytetrafluoroethylene support is a preferred support for forming a composite semipermeable membrane with excellent strength, heat resistance, durability, etc. Since wetting is not always good and defects such as pinholes may occur if a film is formed thereon, it is preferable to perform a hydrophilic treatment on the surface before forming the film. Examples of this hydrophilic treatment include a method of treating the polytetrafluoroethylene surface with a surfactant, a discharge treatment such as corona discharge, glow discharge, and sputter etching. ~I
Torr, the product of processing power density and processing time is 0.01
~50W・sec/C, preferably 0.1~30W・sec/C
A defect-free, high-performance composite semipermeable membrane can be produced by sputter etching a polytetrafluoroethylene support under the following conditions.

Porous polysulfone is also one of the supports that can be suitably used in the present invention, but like polytetrafluoroethylene, it does not always have good wettability with aqueous solutions such as polyvinyl alcohol and polyacrylic acid. It is preferable to carry out a hydrophilic treatment, particularly a sputter etching treatment under the above-mentioned conditions, before formation.

In the above sputter etching process, the stability of discharge,
Sustainability depends on the atmospheric pressure and the distance between the electrodes, but from the practical standpoint of the processing equipment, the atmospheric pressure is 0.0005~ITOr.
r, and under this atmospheric pressure, when the product of processing power density (supplied power/electrode area) and discharge time is within the above range, polytetrafluoroethylene or polytetrafluoroethylene having hydrophilicity suitable for use in the present invention A porous support of polysulfone can be obtained. In addition, the power source is several hundred K.
High frequency power of Hz to several tens of MHz, especially 13.56 MHz, which is the industrially allocated frequency in practical use, is used, and the distance between the electrodes is proportional to the reciprocal of the square root of the atmospheric pressure, so for example, when the atmospheric pressure is 0 In the case of .005 Torr, it is 30 or more. In addition, as the atmospheric gas, inert gas,
Nitrogen, air, water vapor, carbon dioxide gas, etc. are used.

Incidentally, the porous polytetrafluoroethylene film was 0. When processed under an argon atmosphere of I Torr so that the product of processing power density and processing time was 3 W sec/Ca, and when polysulfone porous IQ was 0° I To
The following table shows the effect of improving wetting when G treatment is carried out in an argon atmosphere at 300 mA so that the product of treatment power density and treatment time is 30 W·sec/-.

Both the advancing angle and receding angle with respect to water are significantly reduced. As a result, the wetting of an aqueous solution such as polyvinyl alcohol to a porous support is improved, and when an insolubilized film is formed on a support according to the present invention, pin A composite semipermeable membrane with no defects such as holes can be obtained, and productivity and workability are also significantly improved.

In the method of the present invention, 'ζ is a partially saponified product to a substantially completely saponified product (saponification degree of about 98 mol%) of polyvinyl acetate in the presence of an insolubilizing catalyst on one side of the porous support.
(above), that is, an insolubilized film is formed by reacting polyvinyl alcohol with a carboxyl group-containing water-soluble polymer, and polyvinyl alcohol/L/colka is preferably used rather than partially saponified polyvinyl acetate. When using partially saponified polyvinyl acetate, consider the solubility in water and the wettability of the above-mentioned porous support,
It is desirable to use a material having a saponification degree of 70 mol% or more. The degree of polymerization of polyvinyl alcohol and the like is not particularly limited, but in terms of viscosity, those having a viscosity of 3 to 100 centiboise (Brookfield viscometer) when made into a 4% by weight aqueous solution are preferably used.

In the first method of the present invention, after forming a thin film of polyvinyl alcohol or the like on one side of a porous support, a water-soluble polymer containing a carboxyl group or a monovalent salt thereof is added in the presence of an insolubilizing catalyst. An insolubilized film is formed by reacting with a thin film of polyvinyl alcohol or the like. The composite reverse osmosis membrane thus obtained has excellent water permeability and salt removal rate.

In this method, an aqueous solution containing polyvinyl alcohol, etc. and its insolubilizing catalyst is first deposited on a porous support, and heated to form an insolubilized film, and then a carboxyl group-containing polymer, etc. and its insolubilizing catalyst are deposited on a porous support. A carboxyl group-containing polymer, etc. may be reacted with an insolubilizing film of polyvinyl alcohol or the like by attaching an aqueous solution containing the polyvinyl alcohol or the like and heating it. By attaching it to one side of a support and drying it to form a thin layer, then attaching an aqueous solution containing a carboxyl group-containing polymer etc. and its insolubilization catalyst and heating.
The insolubilized film may be formed by reacting polyvinyl alcohol or the like with a carboxyl group-containing polymer.

In the present invention, the aqueous solution of polyvinyl alcohol, etc. described above varies depending on the molecular weight of the polyvinyl alcohol, etc., but is usually 0.03 to 3% by weight, preferably 0.1% by weight.
A concentration of ~1.0% by weight is used.

As insolubilization catalysts such as polyvinyl alcohol, usually
Inorganic acids such as sulfuric acid and hydrochloric acid, organic acids such as p-toluenesulfonic acid are used, and 0% is used in aqueous solutions such as polyvinyl alcohol.
．． 005-1.0% by weight, preferably 0.03-0.5
wt% added.

To deposit an aqueous solution containing polyvinyl alcohol or the like and optionally an insolubilization catalyst on one side of a porous support,
There are methods such as casting the aqueous solution onto the support, and leaving one side of the support still or in contact with the surface of the aqueous solution.Usually, the latter method is used to contact the support for several seconds to several tens of hours. A good composite membrane can be obtained by a simple method of attaching a thin film of an aqueous solution of polyvinyl alcohol or the like and an insolubilizing catalyst to one side of the support. Note that the contact time is not particularly limited.

A support having an aqueous solution of polyvinyl alcohol or the like and an insolubilization catalyst adhered to one side is usually dried using a heating dryer or the like.
An insolubilized film is formed by heating at a temperature of 80 to 240°C, preferably 105 to 210°C, for several minutes to several hours, preferably for 3 to 60 minutes.

In order to increase the water resistance or mechanical strength of the insolubilized thin film of polyvinyl alcohol etc. formed on the support, an inorganic crosslinking agent such as a boron compound, diisocyanate, diisocyanate, etc. is added to the aqueous solution of polyvinyl alcohol etc. It is of course possible to perform appropriate modifications such as adding an organic crosslinking agent such as aldehyde, irradiating with radiation after film formation, or performing an acetalization reaction.

Examples of water-soluble polymers containing carboxyl groups include polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymers, copolymers of methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and maleic anhydride. can be mentioned. Furthermore, monovalent salt compounds of each of the above polymers, such as alkali metal salts such as lithium, potassium, and sodium salts and ammonium salts, are also suitably used.

The molecular weight of these carboxyl group-containing polymers is not particularly limited, but polyacrylic acid, polymethacrylic acid, etc. usually have a polymer degree of 100 to 1.
0,000, preferably 500 to 6,000.

Catalysts for insolubilizing carboxyl group-containing polymers or monovalent salt compounds thereof are usually esterification catalysts, in particular inorganic and organic acids such as sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid, as well as lithium hydroxide, Alkali metal bases such as potassium hydroxide and sodium hydroxide and organic bases such as pyridine are also used.

The concentration of the aqueous solution of the carboxyl group-containing water-soluble polymer is not particularly limited, but it is usually 0.05 to 3% by weight, preferably 0.61 to 1.0% by weight, depending on its molecular weight. This aqueous solution usually contains 0.005
The insolubilization catalyst is added in a proportion of ~1.0% by weight, preferably 0.03-0.5% by weight.

In order to attach an aqueous solution of the above-mentioned carboxyl group-containing water-soluble polymer to a thin film of polyvinyl alcohol or the like, for example,
A surface on which a thin film of polyvinyl alcohol or the like is formed is brought into contact with the surface of an aqueous solution containing a carboxyl group-containing polymer or the like and an insolubilization catalyst.J,S.

Thereafter, by heating and drying, the carboxyl group-containing polymer or the like reacts with polyvinyl alcohol or the like to form an insolubilized thin film.

The time period for which an aqueous solution of a carboxyl group-containing polymer and an insolubilizing catalyst is brought into contact with a thin film of polyvinyl alcohol, etc. is usually from several seconds to several hours, preferably from several seconds to one hour. , usually at a temperature of 130 to 210°C for 1 minute to several hours, preferably 1 minute to 1 hour.

Next, according to the second method of the present invention, a carboxyl group-containing water-soluble polymer or a monovalent water-soluble salt compound thereof is first attached to one side of the porous support, and after drying, polyvinyl alcohol A composite semipermeable membrane with excellent water permeability and salt removal rate can be obtained by depositing an aqueous solution containing the above and an insolubilization catalyst and heating and drying the membrane. Concentration of aqueous solutions of carboxyl group-containing polymers, etc. and polyvinyl alcohol, etc.
The amount of the insolubilization catalyst added, the time for contact with the surface of the aqueous polymer solution, the time for standing still, etc. are the same as described above.

That is, in this method, first, a carboxyl group-containing water-soluble polymer or its monovalent salt compound is attached to one side of the porous support, and then 80 to 24
After heating and drying at a temperature of 0° C., preferably 105 to 210° C. for several seconds to several hours, an aqueous solution containing polyvinyl alcohol or the like and its insolubilization catalyst is attached to the thin layer of the carboxyl group-containing polymer, etc. Heat and dry to form an insolubilized film.

In the present invention, when one side of the porous support is placed on the liquid surface of an aqueous solution of polyvinyl alcohol or the like or a carboxyl group-containing polymer, it is necessary to take appropriate precautions to prevent the polymer aqueous solution from adhering to the other side of the support. It is possible to take measures such as adhering a synthetic resin film etc. to the surface in advance or applying an appropriate organic solvent to seal it, and then removing the film or removing the solvent after forming the insolubilized film. Needless to say.

As described above, the method for producing a composite semipermeable membrane of the present invention involves depositing an aqueous polymer solution on one side of a porous support and heating it in the presence of an insolubilization catalyst to form a thin film and insolubilize it. Because of this, it has excellent mechanical strength and heat resistance, and unlike conventional methods, it does not use low boiling point or expensive organic solvents, so no harmful solvent vapor is generated during the manufacturing process. There is no need to strictly control the casting, gelling, heat treatment temperature, etc. of the membrane-forming solution, and a high-performance composite semipermeable membrane can be easily manufactured. In particular, if a hydrophilically treated fluorinated olefin polymer is used as the porous support, it will not shrink during the reverse osmosis separation operation.
A composite semipermeable membrane with even better mechanical strength, durability, and heat resistance can be obtained.

Examples of the present invention are listed below. In addition, in the following examples, as the polytetrafluoroethylene support,
0. Under an argon atmosphere of I Torr, the processing power density I W/cn! , the average pore size was 0 under the condition of treatment time of 3 seconds.
．． 20μ, maximum pore diameter 0.28μ (ASTM-F316-
A polytetrafluoroethylene porous film having a thickness of about 150 μm was used, one side of which was subjected to sputter etching treatment, and the treated side refers to the side subjected to the above sputter etching treatment. In addition, in the following, the composite reverse osmosis membrane was tested using 0.5% by weight saline and in a pressurized batch method at 40kg/cn! , water permeability and salt removal rate were measured under conditions of 25°C.

Example 1 Polytetra was placed with the treated side facing down on the surface of a 0.3% by weight aqueous solution of polyvinyl alcohol (Kuraray #217, degree of saponification 88 mol%) and 0.06% by weight of sulfuric acid. The fluoroethylene support was allowed to stand at room temperature for 5 minutes, and then heated and dried at 150° C. for 10 minutes. Next, place the polyacrylic acid (
Toagosei Chemical Industry side layer Aron A-20 (H), 25℃
The viscosity of a 25% by weight aqueous solution is 9600 centiboise (the same applies hereinafter).
After being allowed to stand on the surface of the aqueous solution to which % by weight had been added, it was dried by heating at a temperature of 160° C. for 15 minutes, and thoroughly washed with water.

This composite reverse osmosis membrane has a water permeability of 0.42 rd/rd
・On Sunday, the desalination rate was 96.2%.

Example 2 Polyvinyl alcohol similar to that used in Example 1
．． The polytetrafluoroethylene support was left standing on the surface of the 5% by weight aqueous solution at room temperature for 10 minutes with the treated side facing down, and then dried by heating at a temperature of 150° C. for 10 minutes. next,
The support was placed at room temperature with the polyvinyl alcohol coated side facing down on the surface of an aqueous solution prepared by adding 0.2% by weight of pyridine to a 0925% by weight aqueous solution of the same polyacrylic acid used in Example 1. After leaving it for 3 minutes at 160'
It was heated and dried at C for 30 minutes. The composite reverse osmosis membrane obtained by thorough washing with water has a water permeability of 0.42 n? / rri・
The desalination rate was 97.9%.

Example 3 Polysulfone (Union Carbide P-1700)
) 170 g and 70 g of lithium nitrate to N-methyl-
Prepared by dissolving in 860g of 2-pyrrolidone! ! The membrane solution was cast onto a glass plate, left to stand for 2 seconds at room temperature, and then
It was immersed in water at 0.degree. C. and gelled to obtain a polysulfone porous membrane support with a thickness of 150 .mu.m.

of polyvinyl alcohol similar to that used in Example 1.
．． The above polysulfone support was placed on the surface of a 3% by weight aqueous solution with the surface side having a dense layer called a skin layer facing down at room temperature for 10 minutes, and then at a temperature of 150°C for 5 minutes. It was heated and dried.

Next, 0.0% of the same polyacrylic acid used in Example 1 was used.
The support was left standing at room temperature for 1 minute with the side on which the polyvinyl alcohol film was formed facing down on the surface of an aqueous solution prepared by adding 0.05% by weight of sulfuric acid to a 25% by weight aqueous solution.
It was dried by heating at 0°C for 10 minutes.

The composite reverse osmosis membrane obtained by thorough washing with water has a water permeability of 0.
49n(/r&·day), desalination rate was 96.2%.

Example 4 A polysulfone porous support was obtained in exactly the same manner as in Example 3, and this support was coated with the same skin layer down as 0.3% by weight of polyvinyl alcohol as used in Example 1.
After standing on the surface of the aqueous solution for 10 minutes at room temperature,
It was heated and dried for 5 minutes.

Next, 0.0% of polymethacrylic acid (degree of polymerization about 5000) was added.
After leaving the polysulfone support at room temperature with the side on which the polyvinyl alcohol film was formed facing down on the surface of an aqueous solution prepared by adding 0.05% by weight of sulfuric acid to a 25% by weight aqueous solution, 1
It was dried by heating at a temperature of 50° C. for 10 minutes. The composite reverse osmosis membrane obtained by thorough washing with water had a water permeability of 0.39 m/day and a salt removal rate of 98.8%.

Example 5 A polytetrafluoroethylene support was left standing at room temperature for 5 minutes with the treated side facing down on the surface of a 0.125% by weight aqueous solution of the same polyacrylic acid as in Example 1, and then heated to a temperature of 150°C. and dried for 10 minutes.

Next, the side on which the polyacrylic acid film was formed was placed facing down on the surface of an aqueous solution prepared by adding 0.06% by weight of sulfuric acid to a 0.3% by weight aqueous solution of polyvinyl alcohol similar to that used in Example 1. Then, the polytetrafluoroethylene support was allowed to stand at room temperature for 1 minute, heated and dried at 150° C. for 30 minutes, and then thoroughly washed with water.

The composite reverse osmosis membrane thus obtained has a water permeability of 0.4
~0.65 i/d·day, and the salt removal rate was 98% or more.

Example 6 The treated surface of the polytetrafluoroethylene support was coated with sodium polyacrylate (A-20 (L) manufactured by Toagosei Chemical Industry Co., Ltd.).
), intrinsic viscosity 0.1-0.2), and was left standing at room temperature for 10 minutes on the surface of a 0.3% by weight aqueous solution, and dried at 150° C. for 10 minutes. Next, a film of sodium polyacrylate was formed on the surface of an aqueous solution prepared by adding 0.20% by weight of p-toluenesulfonic acid to a 0.5% by weight aqueous solution of polyvinyl alcohol similar to that used in Example 1. The support was left standing at room temperature for 3 minutes with the side facing down, dried by heating at a temperature of 160° C. for 20 minutes, and then thoroughly washed with water.

The composite reverse osmosis membrane thus obtained has a water permeability of 0.4
0rd/rd·day, the desalination rate was 96.8%.

Claims (16)

[Claims] (1) A film of partially saponified polyvinyl alcohol or polyvinyl acetate is formed on one side of a porous support, and then a carboxyl group-containing water-soluble polymer or its monovalent water-soluble salt compound is applied in the presence of an insolubilizing catalyst. react with the membrane,
A method for producing a composite semipermeable membrane, which comprises forming an insolubilized membrane. (2) Form an insolubilized film on one side of the porous support with partially saponified polyvinyl alcohol or polyvinyl acetate in the presence of an insolubilizing catalyst, and then insolubilize the carboxyl group-containing polymer or its monovalent salt compound. 2. The method for producing a composite semipermeable membrane according to claim 1, wherein the membrane is reacted with the membrane in the presence of a catalyst to form an insolubilized membrane. (3) The method for producing a composite semipermeable membrane according to claim 1 or 2, wherein the degree of saponification of the partially saponified polyvinyl acetate is 70 mol% or more. (4) Claim 1 or 2, characterized in that the carboxyl group-containing polymer is polyacrylic acid, polymethacrylic acid, or an acrylic acid-methacrylic acid copolymer.
A method for producing a composite semipermeable membrane as described in section. (5) The composite according to any one of claims 1, 2, or 4, wherein the insolubilization catalyst for the carboxyl group-containing polymer or its monovalent salt compound is an acid or a base. Method for manufacturing semipermeable membrane. (6) The method for producing a composite semipermeable membrane according to any one of claims 1 to 3, wherein the insolubilization catalyst of polyvinyl alcohol or partially saponified polyvinyl acetate is an acid. (7) The method for producing a composite semipermeable membrane according to claim 1 or 2, wherein the porous support is porous polytetrafluoroethylene or porous polysulfone. (8) The porous support has an atmospheric pressure of 0.0005 to I To
rr, product of processing power density and processing time 0.01 to 50W
- The method for producing a composite semipermeable membrane according to claim 7, characterized in that the membrane is sputter etched under conditions of sec/Cd. (9) An aqueous solution of polyvinyl alcohol or partially saponified polyvinyl acetate is adhered to one side of the porous support, heated and dried to form a film of the polymer, and then a carboxyl group-containing polymer or its monovalent An aqueous solution containing a salt compound and its insolubilization catalyst is attached to the membrane surface and heated,
2. The method for producing a composite semipermeable membrane according to claim 1, wherein the composite semipermeable membrane is formed into an insolubilized membrane. (10) forming a film of a carboxyl group-containing water-soluble polymer or its monovalent water-soluble salt compound on one side of the porous support;
A method for producing a composite semipermeable membrane, comprising: then reacting partially saponified polyvinyl alcohol or polyvinyl acetate with the polymer membrane in the presence of an insolubilizing catalyst to form an insolubilized membrane. (11) Saponification degree of partially saponified polyvinyl acetate is 70
Claim 1 characterized in that the amount is mol% or more.
A method for producing a composite semipermeable membrane according to item 0. (12) The carboxyl group-containing polymer is polyacrylic acid,
11. The method for producing a composite semipermeable membrane according to claim 10, wherein the membrane is polymethacrylic acid or an acrylic acid-methacrylic acid copolymer. (13) The method for producing a composite semipermeable membrane according to claim 10, wherein the catalyst for insolubilizing the carboxyl group-containing polymer or its monovalent salt compound is an acid or a base. (14) The method for producing a composite semipermeable membrane according to claim 10, wherein the porous support is porous polytetrafluoroethylene or porous polysulfone. (15) The porous support has an atmospheric pressure of 0.0005 to I T
orr. Product of processing power density and processing time: 0.01 to 50 W・sec/
cn! 15. The method for producing a composite semipermeable membrane according to claim 14, wherein the composite semipermeable membrane is sputter etched under the following conditions. (16) An aqueous solution of a carboxyl group-containing polymer or its monovalent salt compound is attached to one side of the porous support, heated to form a film of the polymer, and then a polyvinyl alcohol or polyvinyl acetate portion is formed. Claim 1, characterized in that an aqueous solution containing a saponified substance and its insolubilization catalyst is attached to the membrane surface and heated to form an insolubilized membrane.
A method for producing a composite semipermeable membrane according to item 0.