JP7147432B2 - composite semipermeable membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite semipermeable membrane having excellent abrasion resistance and high water permeability.

It is necessary or desirable in many technical fields to selectively remove either ion from a mixed solution of monovalent and divalent ions. For example, in a technology for recovering crude oil from an offshore oil field, a water injection method is used in which seawater is injected into the oil field and the crude oil is pushed out by the pressure of the seawater in order to improve the recovery rate. However, the water injection method has the problem that scale is generated by sulfate ions contained in seawater and Ba ²⁺ and Sr ²⁺ contained in crude oil, and the scale clogs the crude oil recovery piping. . Furthermore, the water injection method also has the problem that the quality of the crude oil deteriorates due to the generation of hydrogen sulfide by sulfate ion-reducing bacteria present in the crude oil. Therefore, in crude oil recovery by the water injection method, removal of sulfate ions from seawater by a membrane is required as a pretreatment process as a measure against scale and as a method for improving the quality of crude oil. In this pretreatment, if only divalent ions (especially sulfate ions) can be selectively removed from the mixed solution of monovalent ions and divalent ions, the difference in osmotic pressure before and after the pretreatment process will be small. can significantly reduce the energy required to remove sulfate ions from

Patent Document 5 discloses a composite semipermeable membrane obtained by reacting piperazine and trimesic acid chloride.

JP 2010-137192 A

After the semipermeable membrane is completed, the separation function layer may be physically damaged. Causes of damage include, for example, contact between semipermeable membranes when stacked for storage after manufacturing, or contact with packaging materials for storage. It is used in a state of being incorporated in an element having at least one semipermeable membrane and channel material inserted therebetween. During assembly of the element, contact with members of the assembly equipment or members of the element can also cause damage to the separation functional layer.

Forming a protective layer on the separation functional layer may be considered in order to suppress these damages. On the other hand, however, there is a problem that the presence of the protective layer reduces the permeation flow rate of the composite semipermeable membrane.

An object of the present invention is to provide a composite semipermeable membrane capable of achieving both water permeability and abrasion resistance.

The present inventors have made intensive studies to achieve the above object, and as a result, have found the following composite semipermeable membrane and completed the present invention.

That is, the present invention has the following configurations (1) to (9). (1) a support membrane comprising a substrate and a porous support layer; and a separating functional layer provided on the porous support layer and containing a polyamide that is a polymer of a polyfunctional amine and a polyfunctional acid halide. , a protective layer provided directly or via another layer on the separation functional layer and containing a hydrophilic polymer (A) having a weight average molecular weight of 5,000 or less and a hydrophilic polymer (B) having a weight average molecular weight of 30,000 or more; A composite semipermeable membrane comprising: (2) The composite semipermeable membrane according to (1), wherein the protective layer has a thickness of 300 nm or more.
(3) The composite semipermeable membrane according to (1) or (2), wherein the mass ratio of component (A) to component (B) is 9 or more.
(4) The composite semipermeable membrane according to any one of (1) to (3), wherein the hydrophilic polymer is polyvinyl alcohol, polyglycerin or polyvinylpyrrolidone.
(5) The composite semipermeable membrane according to any one of (1) to (4), wherein the polyfunctional amine is an aliphatic amine.

In the present invention, the protective layer protects the separation function layer of the semipermeable membrane before water passage. On the other hand, the hydrophilic polymer (A) with a weight-average molecular weight of 5,000 or less contained in the protective layer flows out when water is passed through. Therefore, the decrease in water permeability due to the protective layer is alleviated. Thus, according to the present invention, both scratch resistance and water permeability can be achieved.

1. Composite Semipermeable Membrane The composite semipermeable membrane of the present invention comprises a porous support membrane including a substrate and a porous support layer, and a polyamide separation function layer provided and formed on the porous support membrane. In addition, the composite semipermeable membrane of the present invention further comprises a protective layer made of a hydrophilic polymer and provided directly or via another layer on the polyamide separation function layer.

(1-1) Support Membrane The support membrane supports the polyamide separation function layer having separation performance (hereinafter also simply referred to as "separation function layer") and gives strength to the semipermeable membrane. By itself, it does not substantially have the ability to separate ions and the like. The support membrane includes a substrate and a porous support layer.

The thickness of the support membrane affects the strength of the resulting composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the thickness of the porous support membrane is preferably in the range of 50 µm to 300 µm, more preferably in the range of 100 µm to 250 µm.

Examples of the base material include fabrics made of at least one selected from polyesters and aromatic polyamides. Particular preference is given to using mechanically and thermally stable polyesters.

Nonwoven fabrics such as long fiber nonwoven fabrics and short fiber nonwoven fabrics can be preferably used as the fabric used for the base material. Examples of long-fiber nonwoven fabrics include long-fiber nonwoven fabrics composed of thermoplastic continuous filaments. By using the long-fiber nonwoven fabric as the base material, it is possible to suppress non-uniformity during polymer solution casting and film defects caused by fluffing that occurs when a short-fiber nonwoven fabric is used. In addition, in the step of continuously forming the composite semipermeable membrane, it is preferable to use a long-fiber nonwoven fabric with excellent dimensional stability as the base material, because tension is applied in the film forming direction of the base material.

The thickness of the substrate is preferably in the range of 10 µm to 200 µm, more preferably in the range of 30 µm to 120 µm.

The size and distribution of the pores in the porous support layer are not particularly limited. It is preferable that the pore diameter gradually increases to the surface, that is, the substrate side surface, and that the size of the micropores on the surface on which the separation functional layer is formed is 0.1 nm or more and 100 nm or less.

As the type of resin constituting the porous support layer, for example, polysulfone, cellulose acetate, polyvinyl chloride, or a mixture thereof is preferably used. Polysulfone, which is chemically, mechanically and thermally stable, is particularly preferred.

The support layer is formed by, for example, casting the N,N-dimethylformamide (DMF) solution of the above polysulfone on a tightly woven polyester cloth or polyester nonwoven fabric to a certain thickness, and then wet coagulating it in water. Thus, a porous support membrane having fine pores with a diameter of several 10 nm or less on most of the surface can be obtained.

(1-2) Polyamide Separation Function Layer The separation function layer is a layer that performs a solute separation function in the composite semipermeable membrane, and contains polyamide in the present invention.

Specifically, the polyamide separation functional layer is made of a crosslinked polyamide obtained by interfacial polycondensation of a polyfunctional aliphatic amine and a polyfunctional acid halide.

Polyfunctional aliphatic amines are aliphatic amines having two or more amino groups in one molecule, preferably piperazine-based amines, components shown in (I) below, and derivatives thereof. Examples of piperazine-based amines include piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5 -triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine, ethylenediamine and the like. The above polyfunctional aliphatic amines may be used alone or in combination of two or more. Piperazine or dimethylpiperazine is particularly preferable from the viewpoint of stability of performance expression, and from the viewpoint of increasing water permeability, Dimethylpiperazine is more preferred.

(R1 and R2 are each -H or -( _CH2 )n- _CH3 , and n is an integer from 0 to 3.)
A polyfunctional acid halide is an acid halide having two or more halogenated carbonyl groups in one molecule, and is not particularly limited as long as it gives a polyamide by reaction with the above amine. Examples of polyfunctional acid halides include oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. , 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid. Among acid halides, acid chlorides are preferred, and acid halides of 1,3,5-benzenetricarboxylic acid are particularly preferred from the viewpoints of economic efficiency, availability, ease of handling, ease of reactivity, and the like. Trimesic acid chloride is preferred. The above polyfunctional acid halides may be used alone or in combination of two or more.

Methods for controlling the abundance ratio of the polyfunctional amine and the polyfunctional acid halide in the polyamide separation functional layer include a method of adjusting the ratio of the polyfunctional aliphatic amine concentration and the polyfunctional acid halide concentration during interfacial polycondensation, A method of changing the solvent that dissolves the polyfunctional acid halide, a method of disturbing the interfacial polycondensation field with a surfactant, a method of stopping the reaction during interfacial polycondensation, and a method of adding an additive that inhibits the reaction during interfacial polycondensation. ,and so on.

The average film thickness of the polyamide separation functional layer is preferably 40 nm or less. If the average film thickness is 40 nm or less, sufficient water permeability can be obtained while improving divalent ion removal performance.

The film thickness of the polyamide separation function layer can be analyzed using an observation technique such as transmission electron microscope, TEM tomography, focused ion beam/scanning electron microscope (FIB/SEM). For example, when observing by TEM tomography, the composite semipermeable membrane is treated with a water-soluble polymer to retain the shape of the polyamide separation function layer, and then stained with osmium tetroxide or the like for observation.

The average film thickness of the polyamide separation function layer is calculated from measured values at at least 50 points.

(1-3) Protective layer The protective layer is disposed on the separation functional layer directly or via another layer, and includes a hydrophilic polymer (A) having a weight average molecular weight of 5,000 or less and a hydrophilic polymer having a weight average molecular weight of 30,000 or more. (B).

By setting the weight-average molecular weight of the polymer (A) to 5000 or less, the film thickness of the protective layer is sufficiently thick to improve scratch resistance, while the polymer (A) is eluted at an early stage during membrane filtration. High water permeability can be expressed. In this case, the polymer (A) preferably has a weight average molecular weight of 5,000 or less, more preferably between 300 and 5,000. When the weight-average molecular weight is 300 or more, the amount of the polymer (A) that penetrates into the separation functional layer does not become too large, and the polymer (A) is rapidly eluted during operation, resulting in good water generation. . Polyvinyl alcohol is preferable as the hydrophilic polymer (A) from the viewpoints of economy, availability and ease of handling. In particular, as the polymer (A), the degree of saponification of polyvinyl alcohol is preferably 90% or less, and if it is 90% or more, the water-solubility is low and the elution during operation is delayed, resulting in a decrease in water-generating properties. .

As for the polymer ratio of the polymers (A) and (B), the mass ratio of the polymer (A) to the polymer (B) {mass of the polymer (A)/mass of the polymer (B)} is preferably 9 or more. Since a large amount of polymer is eluted during operation, high water permeability can be exhibited during operation.

When the weight average molecular weight of the hydrophilic polymer (B) forming the protective layer is 30,000 or more, the polymer (B) remains on the film even after the polymer (A) is eluted. The remaining polymer (B) can prevent the semipermeable membrane from being damaged due to contact with the channel material or the like during operation. In other words, even after the polymer (A) is eluted, the polymer (B) provides scratch resistance. In order for the polymer (B) to maintain the scratch resistance during operation, the mass ratio of the polymer (A) to the polymer (B) {mass of the polymer (A)/mass of the polymer (B)} must be 9.8 or less. is preferred.

In addition, since the polymer (B) remains on the membrane, the bivalent ion (especially sulfate ion) removal performance of the composite semipermeable membrane is improved, and the selective separation of monovalent and divalent ions is improved. . One of the reasons why the selective separation is improved is that the polymer (B) remaining on the separation functional layer neutralizes the membrane charge, thereby suppressing the electrostatic interaction between the ions and the membrane. , the removal of monovalent ions in the membrane can be reduced. Furthermore, the polymer (B) contained in the protective layer can close pores larger than divalent ions. As a result, it is thought that the removability of divalent ions (especially sulfate ions) can be enhanced.

The hydrophilic polymer (B) is not particularly limited as long as it does not dissolve the polyamide separation functional layer and the porous support membrane and does not elute during water treatment. Examples include propylcellulose, polyethylene glycol, chitosan, and saponified polyethylene-vinyl acetate copolymer.

In particular, as the polymer (B), the degree of saponification of polyvinyl alcohol is preferably 85% or more.

The thickness of the protective layer before passing water is not particularly limited, but is preferably 300 nm or more, more preferably 500 nm or more. Favorable scratch resistance is obtained because the thickness of the protective layer is 300 nm or more. The thickness of the protective layer is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less. By satisfying the mass ratio of the polymer (A) in the protective layer of 9 and the thickness of the protective layer of 5 μm or less, the polymer (A) is rapidly eluted by the passage of water, resulting in good water permeability.

2. Manufacturing Method Next, a method for manufacturing the composite semipermeable membrane will be described. The manufacturing method includes a step of forming a porous support membrane, a step of forming a separation functional layer, and a step of forming a protective layer.

(2-1) Step of Forming Porous Support Membrane The step of forming a porous support film includes a step of applying a polymer solution to a base material and immersing the base material coated with the solution in a coagulation bath to coagulate the polymer. including the step of allowing

In the step of coating the base material with the polymer solution, the polymer solution is prepared by dissolving the polymer, which is a component of the porous support layer, in a good solvent for the polymer.

The temperature of the polymer solution during coating is preferably in the range of 10° C. to 60° C. when polysulfone is used as the polymer. If the temperature of the polymer solution is within this range, the polymer will not precipitate, and the polymer solution will solidify after being sufficiently impregnated between the fibers of the substrate. As a result, the porous support layer is strongly bonded to the base material by the anchor effect, and a good porous support film can be obtained. The preferred temperature range of the polymer solution can be appropriately adjusted depending on the type of polymer used, desired solution viscosity, and the like.

The time from application of the polymer solution on the substrate to immersion in the coagulation bath is preferably in the range of 0.1 to 5 seconds. If the time until immersion in the coagulation bath is within this range, the polymer-containing organic solvent solution is sufficiently impregnated between the fibers of the base material and then solidified. The preferred range of time until immersion in the coagulation bath can be appropriately adjusted depending on the type of polymer solution to be used, the desired solution viscosity, and the like.

Water is usually used as the coagulation bath, but any bath that does not dissolve the polymer component of the porous support layer may be used. The temperature of the coagulation bath is preferably -20°C to 100°C. More preferably, the temperature of the coagulation bath is between 10°C and 50°C. If the temperature of the coagulation bath is 100° C. or less, the vibration of the coagulation bath surface due to thermal motion can be suppressed, and the smoothness of the film surface after film formation can be maintained. Also, if the temperature is -20° C. or higher, the solidification rate can be maintained, so the film formability can be improved.

The porous support membrane thus obtained may then be washed with hot water to remove residual solvent in the membrane. The temperature of the hot water at this time is preferably 40°C to 100°C, more preferably 60°C to 95°C. If the washing temperature is equal to or lower than the upper limit, the degree of shrinkage of the porous support membrane does not become too large, and deterioration in water permeability can be suppressed. Also, if the washing temperature is 40° C. or higher, a high washing effect can be obtained.

(2-2) Step of Forming Separation Functional Layer Next, the step of forming the separation functional layer constituting the composite semipermeable membrane will be described. In the step of forming the polyamide separation functional layer, an aqueous solution containing a polyfunctional aliphatic amine and an organic solvent solution containing a polyfunctional acid halide are used to perform interfacial polycondensation on the surface of the porous support membrane. A polyamide separation function layer is formed.

The organic solvent for dissolving the polyfunctional acid halide is one that is immiscible with water, does not destroy the porous support membrane, and does not inhibit the production reaction of the crosslinked polyamide. SP value) is 15.2 (MPa) ^1/2 or more and logP is 3.2 or more. When the SP value is 15.2 (MPa) ^1/2 or more and the logP is 3.2 or more, the distribution and diffusion of the polyfunctional aliphatic amine during interfacial polycondensation are optimized, and the functional group amount is can be increased. Typical examples are octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene, etc., and mixtures thereof.

The aqueous solution containing the polyfunctional aliphatic amine preferably contains a surfactant. Examples thereof include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium dodecyldiphenyletherdisulfonate, and styrene bis(sodium naphthalenesulfonate). By containing the surfactant, the effect of increasing the adhesiveness between the separation functional layer and the porous support layer and the effect of increasing the amount of functional groups by disturbing the interfacial polymerization field can be obtained.

An aqueous solution containing a polyfunctional aliphatic amine and an organic solvent solution containing a polyfunctional acid halide each contain compounds such as an acylation catalyst, a polar solvent, an acid scavenger, and an antioxidant, if necessary. It may be

In order to carry out interfacial polycondensation on the porous support membrane, first, the surface of the porous support membrane is coated with an aqueous solution containing a polyfunctional aliphatic amine. As a method for coating the surface of the porous support membrane with the aqueous solution containing the polyfunctional aliphatic amine, the surface of the porous support membrane may be uniformly and continuously coated with the aqueous solution. , a method of coating the surface of the porous support membrane with an aqueous solution, a method of immersing the porous support membrane in an aqueous solution, or the like. The contact time between the porous support membrane and the aqueous solution containing the polyfunctional aliphatic amine is preferably 5 seconds or more and 10 minutes or less, more preferably 10 seconds or more and 2 minutes or less.

Next, it is preferable to remove the excessively applied aqueous solution by a draining process. As a method for draining the liquid, for example, there is a method of holding the film surface in a vertical direction and allowing the liquid to naturally flow down. After draining, the film surface may be dried to remove all or part of the water in the aqueous solution.

When piperazine is contained as the polyfunctional aliphatic amine, the piperazine concentration is preferably 1.0% by weight or more and 10.0% by weight or less. If the piperazine concentration is 1.0% by weight or more, a uniform separation function layer is formed and sufficient divalent ion removal performance is obtained. Further, when the content is 10.0% by weight or less, the thickness of the separation functional layer does not become too thick, and sufficient water permeability can be obtained and sufficient divalent ion selectivity can be obtained.

Thereafter, the porous support membrane coated with the aqueous solution containing the polyfunctional aliphatic amine is coated with the organic solvent solution containing the polyfunctional acid halide described above to form a crosslinked polyamide separation functional layer by interfacial polycondensation. . The time for interfacial polycondensation is preferably 0.1 seconds to 3 minutes, more preferably 0.1 seconds to 1 minute.

The coating temperature of the organic solvent solution containing the polyfunctional acid halide is preferably 10° C. or lower, more preferably 5° C. or lower. If the coating temperature is 10° C. or less, the thickness of the separation functional layer will be thin and the water permeability will be high.

When trimesic acid chloride is contained as the polyfunctional acid halide, the concentration of trimesic acid chloride in the organic solvent solution is preferably about 0.30% by weight or more and 0.70% by weight or less. If the concentration of trimesic acid chloride is 0.30% by weight or more, a high divalent ion removing property can be obtained. Also, if the content is 0.70% by weight or less, high divalent ion selectivity can be obtained.

When piperazine is contained as the polyfunctional aliphatic amine and trimesoyl chloride is contained as the polyfunctional acid halide, the piperazine concentration/trimesoyl chloride concentration is preferably 2.0 or more and 33.0 or less. It is more preferably 0 or more and 25.0 or less. Within this range, high divalent ion selectivity can be obtained.

Next, it is preferable to remove the organic solvent solution after the reaction by a draining step. The organic solvent can be removed by, for example, holding the membrane vertically and removing the excess organic solvent by allowing it to naturally flow down, drying the organic solvent by blowing air with a blower, or using a mixed fluid of water and air. Methods for removing excess organic solvent can be used. In particular, removal with a mixed fluid of water and air is preferred. When a mixed fluid of water and air is used, the separation functional layer swells due to the inclusion of water, and the water permeability increases. In the case of gravity flow, the time for gripping in the vertical direction is preferably between 1 minute and 5 minutes, more preferably between 1 minute and 3 minutes. When the holding time is 1 minute or more, it is easy to obtain a separation functional layer having the desired function, and when the holding time is 3 minutes or less, the occurrence of defects due to overdrying of the organic solvent can be suppressed, thereby suppressing deterioration in performance. can be done.

The composite semipermeable membrane obtained by the above method is further subjected to a washing treatment with hot water at 25°C to 90°C for 1 minute to 60 minutes to improve the solute blocking performance of the composite semipermeable membrane. and water permeability performance can be further improved.

(2-3) Protective Layer Forming Step Next, the protective layer forming step will be described. In the protective layer forming step, a protective layer containing a polymer component is formed directly on the separation functional layer or via another layer.

Specifically, the step of forming the protective layer is a step of applying a solution containing a polymer component onto the polyamide separation functional layer directly or via another layer (e.g., a hydrophilic layer containing a hydrophilic resin). , and then drying the solution.

Examples of coating methods include spraying, coating, and showering. As the solvent, in addition to water, an organic solvent that does not deteriorate the performance of the polyamide separation functional layer may be used in combination. Such organic solvents include, for example, aliphatic alcohols such as methanol, ethanol, propanol, and butanol; lower alcohols such as methoxymethanol and methoxyethanol. Of course, these may be used alone or as a mixed solvent of two or more.

The concentration of the polymer component in the solution is preferably 0.01-1% by weight, more preferably 0.1-0.8% by weight.

The temperature of the solution is not particularly limited as long as it is within the temperature range in which the solution exists as a liquid. It is more preferably from 10 to 45°C, more preferably from 10 to 45°C. After applying the solution onto the polyamide separation function layer, the step of drying the solution is carried out, for example, by heating or blowing air. The temperature at which the drying treatment is performed is not particularly limited, but is preferably about 20 to 160°C, more preferably 40 to 130°C, even more preferably 60 to 120°C. When the drying temperature is 20° C. or higher, the time required for drying can be shortened, and by sufficiently drying the solution, good film performance can be obtained. On the other hand, when the temperature is 160° C. or less, structural changes in the film due to heat are suppressed, so good film performance can be obtained.

As a method for cross-linking the polymer component, a cross-linking method in the case of using polyvinyl alcohol is given below. As a cross-linking method, for example, a method of immersing in an acidic polyhydric aldehyde solution after drying (method A), or an acidic solution containing polyvinyl alcohol and polyhydric aldehyde is applied to the polyamide separation function layer and dried by heating. A method (Method B) of cross-linking polyvinyl alcohol to the polyamide separation functional layer with polyhydric aldehyde at the same time as forming a protective layer by using polyhydric aldehyde. The acid may be either an inorganic acid or an organic acid. For example, sulfuric acid, hydrochloric acid, etc. are used. Furthermore, there is a method (Method C) in which an aqueous solution containing polyvinyl alcohol and an organic titanium compound or an organic zirconium compound is applied onto the polyamide separation function layer and dried by heating to form a protective layer of crosslinked polyvinyl alcohol (Method C). be done. Method B is more preferable from the viewpoints of economy, operability, and the like.

When using Method B, the polyvinyl alcohol concentration in the solution is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.7% by weight. A polyvinyl alcohol concentration of 0.01% by weight or more in the solution is suitable for obtaining the above-mentioned function as a protective layer. Further, it is preferable that the concentration of polyvinyl alcohol in the solution is 1% by weight or less in order to achieve both the above function as a protective layer and the water permeability of the film.

Also, the polyhydric aldehyde concentration is preferably 0.001 to 0.5% by weight, more preferably 0.01 to 0.3% by weight.

The acid concentration is in the range of 0.01 to 1 mol/liter, more preferably in the range of 0.01 to 0.5 mol/liter, still more preferably in the range of 0.01 to 0.3 mol/liter. do it. When the concentration is 0.01 mol/liter or more, the function of the acid as a catalyst is sufficiently exhibited. Also, if the acid concentration is extremely high, the cross-linking reaction may be inhibited.

The temperature of the solution that forms the protective layer is not particularly limited as long as the solution exists as a liquid, but it is 10 to 90° C. from the viewpoint of preventing deterioration of the polyamide separation functional layer and ease of handling. more preferably 10 to 60°C, particularly preferably 10 to 45°C.

The temperature at which the solution is applied onto the polyamide separation functional layer and then dried is not particularly limited, but is about 20 to 160°C, preferably 40 to 130°C, more preferably 60 to 120°C. °C. When the temperature is 20° C. or higher, the time required for the drying process is shortened, and sufficient drying and cross-linking can be performed, so excellent membrane performance can be obtained. On the other hand, when the temperature is 160° C. or less, deterioration in film performance due to structural changes in the film is suppressed.

Further, in order to improve the salt blocking property, water permeability, oxidizing agent resistance, etc. of the composite semipermeable membrane, various conventionally known treatments may be performed.

3. Use of Composite Semipermeable Membrane The composite semipermeable membrane of the present invention can be suitably used for removing divalent ions. This composite semipermeable membrane can be applied, for example, to removing salt or adjusting minerals from brine or seawater, and removing salt or adjusting minerals in the food field.

The composite semipermeable membrane of the present invention includes a raw water channel material such as a plastic net, a permeated water channel material such as tricot, and, if necessary, a film for increasing pressure resistance, and a cylindrical shape having a large number of holes. is wound around the water collection pipe of the spiral type, and is suitably used as a spiral type composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and housed in a pressure vessel can also be formed.

Further, the composite semipermeable membranes, elements thereof, and modules described above can be combined with a pump for supplying raw water thereto, a device for pretreating the raw water, and the like to form a fluid separation device. By using this separator, it is possible to separate raw water into permeated water such as drinking water and concentrated water that has not permeated the membrane, thereby obtaining desired water.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited by these Examples.

<Performance evaluation>
The following operations were carried out without performing treatment using a bar coater, which will be described later.

( _MgS04 removal rate)
Membrane filtration was performed by supplying salt water adjusted to a temperature of 25° C., a pH of 7.0, and a MgSO ₄ concentration of 2000 mg/L to the composite semipermeable membrane at an operating pressure (that is, operating pressure) of 0.48 MPa. Permeated water was collected for 0.5 hours from 3 hours after the start of filtration to 3.5 hours after the start of filtration. The electrical conductivity of the feed water and the permeated water was measured with an electrical conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain the practical salinity, that is, the MgSO4 concentration of _each . The MgSO ₄ removal rate was calculated based on the MgSO ₄ concentration thus obtained and the following formula. MgSO ₄ removal rate (%)={1−(MgS0 ₄ concentration in permeate)/(MgS0 ₄ concentration in feed)}×100
(NaCl removal rate)
Evaluation water adjusted to a temperature of 25° C., a pH of 7.0 and an NaCl concentration of 500 ppm was supplied to the composite semipermeable membrane at an operating pressure of 0.48 MPa to perform membrane filtration. Permeated water was collected for 0.5 hours from 3 hours after the start of filtration to 3.5 hours after the start of filtration. The electrical conductivity of the feed water and the permeated water was measured with an electrical conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain practical salinity, ie, NaCl concentration. The NaCl removal rate was calculated based on the NaCl concentration thus obtained and the following formula. NaCl removal rate (%) = 100 × {1-(NaCl concentration in permeate water/NaCl concentration in feed water)}
(membrane permeation flux)
In the test of the preceding paragraph, the membrane permeation water amount of the feed water (MgSO ₄ aqueous solution or NaCl aqueous solution) was measured, and the value converted to the daily water permeation amount (cubic meter) per square meter of the membrane surface was the membrane permeation flux (m ³ / m ² /day).

(Bivalent ion selectivity)
Using the MgSO ₄ removal rate and NaCl removal rate obtained in the test in the previous section, divalent ion selectivity was obtained based on the following equation. Divalent ion selectivity = ( _MgS04 removal rate)/(NaCl removal rate)
<Scratch resistance evaluation>
- A scratch bar coater (No. 10 manufactured by AS ONE) was rolled while being in contact with the surface of the separation functional layer side of the composite semipermeable membrane before water was passed through, and the operation of passing through at a speed of 200 mm/sec was performed twice.

Measurement of change in performance After scratching, the _MgSO4 removal rate was measured. The measurement method was as described above.

(100-removal rate of scratched film)/(100-removal rate of non-scratched film) was calculated as an index for evaluation of scratch resistance. It can be said that the smaller this value (closer to 1), the higher the scratch resistance.

<Preparation of composite semipermeable membrane>
(Reference example: base film)
・Reference example 1
A 15 wt% dimethylformamide (DMF) solution of polysulfone was applied at room temperature (25°C) to a thickness of 180 µm on a non-woven fabric made of polyester fibers (air permeability: 1.0 cc/cm ² /sec) manufactured by a papermaking method. Immediately after casting, the substrate was immersed in pure water for 5 minutes to form a porous support layer on the substrate, thereby producing a porous support membrane.

Next, this porous support membrane was immersed in an aqueous solution containing 1.0% by weight of piperazine and 200 ppm of sodium dodecyldiphenyletherdisulfonate for 10 seconds, and the excess aqueous solution was removed by blowing nitrogen from an air nozzle. Furthermore, a solution of 0.50% by weight of trimesic acid chloride dissolved in n-decane was uniformly applied to the entire surface of the porous support layer (application temperature: 20°C). Next, in order to remove excess solution from the membrane, the membrane was vertically drained and dried by blowing air at 25° C. using an air blower. After that, it was washed with pure water at 80° C. for 2 minutes to obtain a composite semipermeable membrane. Performance and abrasion resistance of the composite semipermeable membrane thus obtained were evaluated, and the results are shown in Table 1.

Reference Example 2 A separation functional layer was formed in the same manner as in Reference Example 1 except that piperazine in Reference Example 1 was changed to 2,5-dimethylpiperazine to obtain a composite semipermeable membrane. Table 1 shows the evaluation results of this film.

(Film with protective layer)
Using the film of Reference Example 1 or 2 as a base film, a protective layer was formed thereon as follows.

<Comparative Example 1> For the film obtained in Reference Example 1, an aqueous solution containing 0.2% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) was applied to the surface of the film, and dried at 65°C with a hot air dryer. for 2 minutes and crosslinked. After that, it is washed with hot water at 70°C to remove uncrosslinked materials and acid catalysts, brought into contact with an aqueous solution containing 10% by weight of isopropyl alcohol for 10 minutes, and then thoroughly washed with water to obtain a composite semipermeable membrane. rice field. Table 1 shows the evaluation results of this film.

<Comparative Example 2> A protective layer was formed in the same manner as in Comparative Example 1 except that the polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 500) was changed to polyvinyl alcohol (degree of saponification 98%, weight average molecular weight 5000). A semipermeable membrane was obtained. Table 3 shows the evaluation results of this film.

<Comparative Example 3> A protective layer was formed in the same manner as in Comparative Example 1 except that the polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 500) was changed to SELVOL205 (degree of saponification 87-89%, weight average molecular weight 31000-50000). to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Comparative Example 4> A protective layer was formed in the same manner as in Comparative Example 1, except that polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) was changed to polyvinyl alcohol (degree of saponification: 90%, weight average molecular weight: 130,000). , to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

< Comparative Example 5> An aqueous solution of 0.2% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 500) of Comparative Example 1 was mixed with 0.02 weight of SELVOL205 (degree of saponification 87 to 89%, weight average molecular weight 31000 to 50000). % and 0.18% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 5500). Table 3 shows the evaluation results of this film.

<Comparative Example 6> An aqueous solution of 0.2% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) of Comparative Example 1 was added to 0.02% by weight of polyvinyl alcohol (degree of saponification: 89%, weight average molecular weight: 25,000). A protective layer was formed in the same manner except that the solution was changed to an aqueous solution containing 0.18% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Example 1> An aqueous solution of 0.2% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) of Comparative Example 1 was mixed with 0.02 weight of SELVOL205 (degree of saponification: 87 to 89%, weight average molecular weight: 31,000 to 50,000). % and 0.18% by weight of polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500). Table 3 shows the evaluation results of this film.

<Example 2> Same as Example 1 except that SELVOL205 (degree of saponification 87-89%, weight average molecular weight 31000-50000) was changed to SELVOL125 (degree of saponification 99.3% or more, weight average molecular weight 85000-124000). A protective layer was formed to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Example 3> A protective layer was formed in the same manner as in Example 1 except that the polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) was changed to polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 5000). A semipermeable membrane was obtained. Table 3 shows the evaluation results of this film.

<Example 4> Same as Example 3 except that SELVOL205 (degree of saponification 87-89%, weight average molecular weight 31000-50000) was changed to SELVOL125 (degree of saponification 99.3% or more, weight average molecular weight 85000-124000). A protective layer was formed to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Example 5> 0.02% by weight of SELVOL205 (degree of saponification 87 to 89%, weight average molecular weight 31,000 to 50,000) and polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 500) were added to the film obtained in Reference Example 2. An aqueous solution containing 0.18% by weight was applied to the surface of the film and dried at 65° C. for 2 minutes in a hot air dryer to crosslink. After that, it is washed with hot water at 70°C to remove uncrosslinked materials and acid catalysts, brought into contact with an aqueous solution containing 10% by weight of isopropyl alcohol for 10 minutes, and then thoroughly washed with water to obtain a composite semipermeable membrane. rice field. Table 3 shows the evaluation results of this film.

<Example 6> Same as Example 5 except that SELVOL205 (degree of saponification 87-89%, weight average molecular weight 31000-50000) was changed to SELVOL125 (degree of saponification 99.3% or more, weight average molecular weight 85000-124000). A protective layer was formed to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Example 7> A protective layer was formed in the same manner as in Example 1, except that polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) was replaced with glycerin to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

<Example 8> A protective layer was formed in the same manner as in Example 1, except that polyvinyl alcohol (degree of saponification: 88%, weight average molecular weight: 500) was replaced with diglycerin to obtain a composite semipermeable membrane. Table 3 shows the evaluation results of this film.

As is clear from the results in Tables 1 and 3, the use of the composite semipermeable membrane of the present invention can selectively and highly remove divalent ions (especially sulfate ions), and the abrasion resistance is improved. high.

INDUSTRIAL APPLICABILITY The present invention is applicable to semipermeable membranes such as reverse osmosis membranes and nanofiltration membranes. In particular, a semipermeable membrane having a separation function layer formed of a polyamide containing a monomer component derived from an aliphatic amine can be used as a nanofiltration membrane and selectively removes divalent ions (especially sulfate ions) from seawater. can do. Therefore, when crude oil is efficiently recovered from offshore oil fields by the water injection method, injection water that can effectively prevent scale formation and deterioration of crude oil quality is supplied from seawater stably at a high recovery rate. be able to.

Claims (5)

a support membrane comprising a substrate and a porous support layer;
a separation functional layer provided on the porous support layer and containing a polyamide that is a polymer of a polyfunctional amine and a polyfunctional acid halide;
A composite semipermeable material comprising a protective layer provided on the separation functional layer and containing a hydrophilic polymer (A) having a weight average molecular weight of 5,000 or less and a hydrophilic polymer (B) having a weight average molecular weight of 30,000 or more. film. 2. The composite semipermeable membrane according to claim 1, wherein the protective layer has a thickness of 300 nm or more. 3. The composite semipermeable membrane according to claim 1, wherein the mass ratio of polymer (A) to polymer (B) is 9 or more. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the hydrophilic polymer (B) is polyvinyl alcohol, polyglycerin or polyvinylpyrrolidone. The composite semipermeable membrane according to any one of claims 1 to 4, wherein said polyfunctional amine is an aliphatic amine.