JP6645764B2 - Composite separation membrane and separation membrane element - Google Patents

Description

  The present invention relates to a composite separation membrane and a separation membrane element.

  BACKGROUND ART A separation membrane for separating a liquid substrate (for example, water) and a dissolved substance (for example, salts) is used for production of pure water, desalination of brine such as seawater, and wastewater treatment. One type of separation membrane is a composite separation membrane including a porous support and a separation functional layer formed on the porous support. The separation functional layer is selected from organic compounds such as polyamide, polysulfone, and cellulose acetate depending on the use of the composite separation membrane. As a composite separation membrane, a membrane composed of a polyamide formed by a reaction between a polyfunctional amine and a polyfunctional acid halide is known.

  At present, there is a need for a composite separation membrane with further improved separation characteristics. In particular, in recent years, the magnitude of the permeation flux of a substrate (hereinafter, simply referred to as "permeation flux") is required to be higher than the rejection rate of a dissolved substance, such as for use in wastewater treatment or pretreatment for seawater desalination. There is a strong demand to improve the separation properties to suit the application. Further, there is always a demand for increasing the permeation flux of the composite separation membrane in order to reduce the operating energy (energy saving) of the apparatus.

  Patent Documents 1 and 2 describe a composite semipermeable membrane in which a separation functional layer of a crosslinked polyamide is formed on a porous support membrane. In the composite semipermeable membrane described in Patent Document 1, the crosslinked polyamide is formed by a reaction of a mixed amine component of an aliphatic polyfunctional amine and an aromatic polyfunctional amine with a polyfunctional acid halide and a polyfunctional acid anhydride halide. can get. The molar ratio between the polyfunctional acid halide and the polyfunctional anhydride halide is in the range of 80/20 to 10/90.

  In the composite semipermeable membrane described in Patent Document 2, a separation functional layer of a crosslinked polyamide is formed on a porous support membrane by polycondensation from a polyfunctional amine and a polyfunctional acid halide and a polyfunctional acid anhydride halide. I have. The polyfunctional amine is a mixed amine of an aliphatic polyfunctional amine and an aromatic polyfunctional amine.

JP-A-2000-33243 JP-A-2000-202257

  The humic acid removal rate of the composite separation membranes described in Patent Documents 1 and 2 is high. However, the composite separation membranes described in Patent Documents 1 and 2 exhibit a high removal rate even for dissolved substances other than humic acid such as salts when used without being used in combination with other separation membranes. I'm not sure if I can do that. Therefore, one of the objects of the present invention is a composite separation membrane comprising a porous support and a separation functional layer formed on the porous support, and the separation target is improved while improving the permeation flux. It is an object of the present invention to provide a new composite separation membrane capable of suppressing a decrease in the rejection of a dissolved substance other than humic acid such as a salt contained in a liquid.

The present invention
A porous support, comprising a separation functional layer formed on the porous support,
The separation functional layer includes an aliphatic polyfunctional amine having two or more secondary amino groups, a primary amino group bonded to a terminal of a linear hydrocarbon chain, and another terminal of the linear hydrocarbon chain. Is composed of a polyamide formed by the reaction of a compound group containing a linear hydrocarbon chain-containing polyfunctional amine having a primary amino group or a secondary amino group and a polyfunctional acid halide,
Provided is a composite separation membrane, wherein the proportion of the linear hydrocarbon chain-containing polyfunctional amine in the polyfunctional amine in the compound group is less than 15 mol%.

  The present invention also provides a separation membrane element provided with the above composite separation membrane.

  According to the present invention, there is provided a composite separation membrane including a porous support and a separation functional layer formed on the porous support, wherein the salt contained in the liquid to be separated is improved while improving the permeation flux. Another object of the present invention is to provide a new composite separation membrane capable of suppressing a decrease in the rejection of dissolved substances other than humic acid.

It is a perspective view showing typically an example of a separation membrane element of the present invention.

  The composite separation membrane of the present invention includes a porous support and a separation functional layer formed on the porous support. The separation functional layer is composed of a polyamide formed by a reaction of a compound group including an aliphatic polyfunctional amine (A), a linear hydrocarbon chain-containing polyfunctional amine (B), and a polyfunctional acid halide. The aliphatic polyfunctional amine (A) has two or more secondary amino groups. The linear hydrocarbon chain-containing polyfunctional amine (B) comprises a primary amino group bonded to the terminal of the linear hydrocarbon chain and a primary amino group bonded to the other terminal of the linear hydrocarbon chain. Group or a secondary amino group. The number of carbon atoms in the above-mentioned straight chain hydrocarbon chain of the straight chain hydrocarbon chain-containing polyfunctional amine (B) is, for example, 2 to 6. Here, the ratio of the linear hydrocarbon chain-containing polyfunctional amine (B) to the polyfunctional amine in the compound group (hereinafter, may be referred to as “ratio R”) is less than 15 mol%. The term “primary amino group” means a monovalent functional group obtained by removing one hydrogen atom from a primary amine, and the term “secondary amino group” means removing one hydrogen atom from a secondary amine. Means a monovalent functional group described above.

  In this polyamide, each of the aliphatic polyfunctional amine (A) and the linear hydrocarbon chain-containing polyfunctional amine (B) reacts with the polyfunctional acid halide. Specifically, the polyamide has a structural unit formed by polymerization (polycondensation) of an aliphatic polyfunctional amine (A) and a linear hydrocarbon chain-containing polyfunctional amine (B). For this reason, the polyamide comprises a structural unit (AU) formed by the reaction of an aliphatic polyfunctional amine (A) with a polyfunctional acid halide, a linear hydrocarbon chain-containing polyfunctional amine (B) and a polyfunctional acid halide. And a structural unit (BU) formed by the reaction with Composite in which the polyamide contains the structural unit (BU) in an appropriate molar ratio in addition to the structural unit (AU), thereby improving the permeation flux while maintaining the rejection rate of the dissolved substance contained in the liquid to be separated. A separation membrane is obtained. From this viewpoint, the ratio R is less than 15 mol%. Even when the ratio R is relatively small, the permeation flux can be improved while maintaining the rejection of the dissolved substance contained in the liquid to be separated. For this reason, the lower limit of the ratio R is not particularly limited, but is, for example, 0.1 mol% or more.

  The proportion of the aliphatic polyfunctional amine (A) in the polyfunctional amine in the compound group is larger than 85 mol%.

  The polyfunctional amine is an amine having two or more reactive amino groups, for example, a diamine having two reactive amino groups. The compound group may contain two or more kinds of aliphatic polyfunctional amines (A), and may contain two or more kinds of linear hydrocarbon chain-containing polyfunctional amines (B).

  The aliphatic polyfunctional amine (A) is not particularly limited, but is, for example, an alicyclic polyfunctional amine. In this case, the combination with the linear hydrocarbon chain-containing polyfunctional amine (B) can improve the permeation flux of the composite separation membrane at a higher level.

  Examples of the aliphatic polyfunctional amine (A) include, but are not particularly limited to, a group consisting of 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, and piperazine and derivatives thereof. At least one selected from the following. It is desirable that the aliphatic polyfunctional amine (A) is piperazine or a piperazine derivative. In this case, it is possible to more reliably improve the permeation flux while maintaining the rejection of the dissolved substance contained in the liquid to be separated. Here, the piperazine derivative refers to a compound in which at least one hydrogen atom bonded to a carbon atom or a nitrogen atom of piperazine is substituted by a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms, an amino group, or a hydroxyl group. When the aliphatic polyfunctional amine (A) is a polyfunctional amine in which a hydrogen atom bonded to a nitrogen atom of piperazine is substituted, the substituent is an amino group. The piperazine derivative is, for example, at least one selected from 2,5-dimethylpiperazine and 4-aminomethylpiperazine.

  The linear hydrocarbon chain-containing polyfunctional amine (B) is desirably ethylenediamine or an ethylenediamine derivative. In other words, the linear hydrocarbon chain of the linear hydrocarbon chain-containing polyfunctional amine (B) has two carbon atoms. In this case, it is possible to more reliably improve the permeation flux while maintaining the rejection of the dissolved substance contained in the liquid to be separated. Here, the ethylenediamine derivative refers to a compound in which at least one hydrogen atom bonded to a nitrogen atom of ethylenediamine is substituted with a substituent. The substituent is, for example, an alkyl group having 1 to 4 carbon atoms or a phenyl group.

  The linear hydrocarbon chain-containing polyfunctional amine (B) is desirably at least one selected from the group consisting of N-phenylethylenediamine, N-methylethylenediamine, and ethylenediamine. In this case, it is possible to more reliably improve the permeation flux while maintaining the rejection of the dissolved substance contained in the liquid to be separated.

  A polyfunctional acid halide is an acid halide having two or more reactive carbonyl groups. The polyfunctional acid halide may be an aromatic polyfunctional acid halide or an aliphatic polyfunctional acid halide. The aliphatic polyfunctional acid halide may be an alicyclic polyfunctional acid halide. The compound group may contain two or more polyfunctional acid halides. When the compound group contains a polyfunctional acid halide having a valence of 3 or more, a separation functional layer composed of a polyamide having a crosslinked structure can be formed.

  The aromatic polyfunctional acid halide is not particularly limited, for example, trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyl dicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzene trisulfonic acid trichloride, benzene disulfonic acid dichloride and It is at least one selected from the group consisting of chlorosulfonylbenzenedicarboxylic acid dichloride.

  Aliphatic polyfunctional acid halide is not particularly limited, for example, propane dicarboxylic acid dichloride, butane dicarboxylic acid dichloride, pentane dicarboxylic acid dichloride, butane tricarboxylic acid trichloride, butane tricarboxylic acid trichloride, pentane tricarboxylic acid trichloride, glutaryl halide , Adipoyl halides, and alicyclic polyfunctional acid halides described below.

  The alicyclic polyfunctional acid halide is not particularly limited, for example, cyclopropanetricarboxylic acid trichloride, cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetricarboxylic acid trichloride, cyclopentanetetracarboxylic acid tetrachloride, cyclohexanetricarboxylic acid trichloride, It is at least one selected from the group consisting of tetrahydrofuran tetracarboxylic acid tetrachloride, cyclopentanedicarboxylic dichloride, cyclobutanedicarboxylic dichloride, cyclohexanedicarboxylic dichloride, and tetrahydrofurandicarboxylic dichloride.

  The configuration of the porous support is not limited as long as a separation functional layer can be formed thereon. The porous support is, for example, an ultrafiltration membrane having a microporous layer formed on a nonwoven fabric. The average pore size of the microporous layer is, for example, about 0.01 to 0.4 μm. The material of the microporous layer is, for example, polysulfone, polyarylethersulfone such as polyethersulfone; polyimide; polyvinylidene fluoride. Among them, polysulfone and polyarylethersulfone are preferred because of their high chemical, mechanical and thermal stability. The porous support may be a self-supporting support composed of a thermosetting resin such as an epoxy resin. In this case, the porous support has an average pore diameter of, for example, 0.01 to 0.4 μm. Having. The thickness of the porous support is not particularly limited, and is, for example, 10 to 200 μm, and preferably 20 to 75 μm.

  The method for forming the separation functional layer on the porous support is not particularly limited, and a known method can be employed. The method for forming the separation functional layer is, for example, an interfacial condensation method, a phase separation method, or a thin film coating method. In the interfacial condensation method, an amine aqueous solution containing a polyfunctional amine is brought into contact with an organic acid halide solution containing a polyfunctional acid halide, so that a reaction between the polyfunctional amine and the polyfunctional acid halide on the contact surface (interface) ( (Polycondensation) to form a separation functional layer composed of polyamide. The formation of the separation functional layer by the interfacial condensation can be performed on the porous support, and in this case, the separation functional layer is directly formed on the porous support. Of course, the separation functional layer formed at a place other than the porous support, for example, on the transfer substrate, may be placed on the porous support. The details of the interfacial condensation method are described in, for example, JP-A-58-24303, JP-A-1-180208, and the like, and the conditions described in these known documents can be appropriately employed. Also in the phase separation method and the thin film coating method, a method described in a known document can be employed.

  The separation functional layer is formed by applying an aqueous solution of an amine containing a polyfunctional amine component on a porous support to form an aqueous solution coating layer, and then applying an organic acid halide solution containing a polyfunctional acid halide to the porous support. It is desirable to form the layer by contacting with the coating layer and promoting interfacial polymerization.

  In this method, the concentration of the polyfunctional amine in the aqueous amine solution is not particularly limited, and is, for example, 0.1 to 10% by weight, and preferably 1 to 4% by weight. The concentration of the polyfunctional amine in the aqueous amine solution is, for example, 0.1% by weight or more, and is desirably 0.1% by weight or more, from the viewpoint of preventing the occurrence of defects such as pinholes in the separation function layer and maintaining a high rejection rate of the dissolved substance. 1% by weight. Further, from the viewpoint of preventing the permeation resistance from increasing due to the thickness of the separation function layer becoming too large and suppressing the permeation flux from decreasing, the concentration of the polyfunctional amine in the amine aqueous solution is, for example, 10% by weight or less. , Preferably 4% by weight or less.

  In this method, the concentration of the polyfunctional acid halide in the organic acid halide solution is not particularly limited, and is, for example, 0.01 to 5% by weight, and preferably 0.05 to 3% by weight. From the viewpoint of suppressing the unreacted polyfunctional amine from remaining in the separation function layer, preventing defects such as pinholes from occurring in the separation function layer, and maintaining a high rejection rate of dissolved substances, the acid halide organic solution is used. The concentration of the polyfunctional acid halide is, for example, 0.01% by weight or more, and desirably 0.05% by weight or more. Further, from the viewpoint of suppressing the remaining of unreacted polyfunctional acid halide in the separation function layer, and preventing the permeation resistance from increasing due to the thickness of the separation function layer becoming too large, thereby suppressing a decrease in permeation flux. The concentration of the polyfunctional acid halide in the acid halide organic solution is, for example, 5% by weight or less, preferably 3% by weight or less.

  The organic solvent used for the acid halide organic solution is not particularly limited as long as it has low solubility in water, does not deteriorate the porous support, and dissolves the polyfunctional acid halide. Hydrocarbon: a halogen-substituted hydrocarbon such as 1,1,2-trichlorotrifluoroethane. The organic solvent is desirably a saturated hydrocarbon having a boiling point of 300 ° C. or less, and more desirably a saturated hydrocarbon having a boiling point of 200 ° C. or less.

  The time from application of the aqueous amine solution on the porous support to application of the acid halide organic solution depends on the composition and viscosity of the aqueous amine solution and the pore size of the surface of the porous support, but is 1 to 180 seconds. Degree, desirably 2 to 120 seconds, more desirably 2 to 40 seconds, and particularly desirably 2 to 10 seconds. If the coating interval between the two is excessively long, the aqueous amine solution penetrates and diffuses deep inside the porous support before the organic acid halide solution is applied, so that the unreacted polyfunctional amine is supported on the porous support. May remain in large quantities in the body. Further, unreacted polyfunctional amine that has penetrated deep inside the porous support tends to be difficult to remove even by a subsequent washing treatment. On the other hand, if the coating interval between the two is excessively short, the aqueous amine solution hardly penetrates the porous support before the application of the organic acid halide solution, and the excess aqueous amine solution is present on the porous support. In some cases, the characteristics of the separated functional layer deteriorate.

  In this method, after a coating layer of an aqueous amine solution formed on a porous support is brought into contact with an organic acid halide solution, excess organic solution present on the porous support is removed, and the porous support is removed. It is desirable to heat and dry the film formed on the body to form a separation functional layer. By heating and drying, the mechanical strength and heat resistance of the separation function layer can be increased. The temperature of the heating and drying is, for example, 70 to 200C, and preferably 80 to 130C. The heating time is, for example, about 30 seconds to 10 minutes, and preferably about 40 seconds to 7 minutes.

  In addition to the aliphatic polyfunctional amine (A), the linear hydrocarbon chain-containing polyfunctional amine (B), and the polyfunctional acid halide, the compound group facilitates the formation of a separation functional layer or obtains a composite separation membrane. Various additives can be included for the purpose of improving the properties. The additive may be contained, for example, in an aqueous amine solution and / or an organic acid halide solution in the interfacial condensation method. Depending on the type of the additive, it remains in the formed separation function layer and contributes, for example, to the improvement of the characteristics of the composite separation membrane.

  For example, the compound group further includes a hydrophilic polymer as an additive. The hydrophilic polymer is, for example, at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid, and polyvinyl alcohol is desirable. When forming the separation functional layer by the interfacial condensation method, the aqueous polyfunctional amine solution may contain a hydrophilic polymer such as polyvinyl alcohol. The hydrophilic polymer is copolymerized with a polyfunctional amine and a polyfunctional acid halide to improve the hydrophilicity on the surface and inside of the formed separation function layer. Thereby, the permeation flux of the composite separation membrane can be further improved. The amount of the additive is preferably about 0.01 to 20% by weight, more preferably 0.05 to 5% by weight.

Other additives include, for example, surfactants such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium lauryl sulfate that improve the wettability of the solution to the porous support; Basic compounds such as sodium hydroxide, trisodium phosphate, and triethylamine for removing hydrogen halide generated by the reaction; acylation catalysts for catalyzing the reaction; solubility parameters described in JP-A-8-224452 Is a compound of 8 to 14 (cal / cm ³ ) ^1/2 . These compounds may be added to the aqueous amine solution as needed.

  Further, for example, the additive is a salt of a tetraalkylammonium halide or trialkylammonium with an organic acid. This salt has effects such as easier formation of the separation functional layer, improvement of the absorbability of the aqueous amine solution on the porous support, and promotion of the reaction between the polyfunctional amine and the polyfunctional acid halide. This salt may be added to the amine aqueous solution as needed.

  The thickness of the separation function layer is not particularly limited, and is usually about 0.05 to 2 μm, and preferably 0.1 to 1 μm. It is desirable that the thickness of the separation function layer is uniform.

  The shape of the separation function layer is not particularly limited. It may be a single separation functional layer formed on a porous support, or may be a separation functional layer having a “double fold structure” described in JP-A-2011-189340.

  The separation function layer is a layer composed of polyamide. As long as the effects of the present invention can be obtained, the separation function layer may include a material other than polyamide. At this time, the separation function layer is a layer containing polyamide as a main component. The main component is a component having the largest content, and the content is usually 50% by weight or more, for example, 60% by weight or more, 70% by weight or more, 80% by weight or more, and 90% by weight or more. The separation function layer may be a layer made of polyamide.

  The composite separation membrane of the present invention may be a membrane further subjected to chlorination. Chlorine treatment further improves the permeation flux of the composite separation membrane, for example, by removing portions of the polyamide where bonding is unstable. Further, in the composite separation membrane of the present invention, a decrease in the rejection rate of dissolved substances due to chlorination is suppressed. The composite separation membrane of the present invention may be a membrane that has not been subjected to chlorination.

  A known method can be used for the chlorination. For example, chlorination can be performed by bringing an aqueous solution containing free chlorine into contact with a separation functional layer. The aqueous solution containing free chlorine is not particularly limited, and is, for example, an aqueous solution of a chlorine compound having an action of generating free chlorine in water, such as sodium hypochlorite and calcium chloride. The concentration of the chlorine compound in the aqueous solution is preferably about 100 to 1000 mg / L, and the free chlorine concentration at that time is about 10 to 1000 ppm. The conditions for the chlorination are not particularly limited, and can be controlled according to the free chlorine concentration of the aqueous solution, the material of the separation functional layer, and the like. For example, the treatment time is controlled in the range of 10 minutes to 100 hours. The specific method of bringing the aqueous solution into contact with the separation functional layer is not particularly limited.For example, the composite separation membrane is immersed in the aqueous solution, the aqueous solution is applied or sprayed on the separation functional layer, or the aqueous solution is applied to the composite separation membrane. There is a way to let water flow. When passing water, it is desirable to apply a pressure of about 1 to 5 MPa to the aqueous solution and to pass water under pressure.

  A coating layer may be provided on the surface of the composite separation membrane of the present invention. The coating layer is, for example, a nonionic hydrophilic layer, and is a layer composed of a polymer. When a coating layer that is a hydrophilic layer is provided, the permeation flux of the composite separation membrane is further improved by improving the hydrophilicity of the surface of the composite separation membrane. The coating layer is desirably provided on the surface of the composite separation membrane on the separation function layer side.

  The polymer used for the coating layer is not particularly limited as long as it does not dissolve the separation function layer and the porous support, and elutes when the composite separation membrane is used (for example, during water treatment). The polymer is, for example, at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropylcellulose, polyethylene glycol, and a saponified ethylene-vinyl acetate copolymer. The polymer is desirably polyvinyl alcohol, and desirably polyvinyl alcohol having a saponification degree of 99% or more. The coating layer can be formed on the surface of the composite separation membrane, for example, by immersing the composite separation membrane in a solution in which the polymer is dissolved and drying the composite separation membrane.

  The coating layer may have a crosslinked structure with the polyamide constituting the separation function layer. In this case, elution of the coating layer during use of the composite separation membrane can be suppressed. The coating layer having a crosslinked structure with polyamide is, for example, a layer containing polyvinyl alcohol having a saponification degree of 90% or more. The method for crosslinking polyvinyl alcohol and polyamide is not particularly limited. For example, a composite separation membrane having a polyvinyl alcohol layer formed on the surface of a separation functional layer may be immersed in a hydrochloric acid-acidic polyhydric aldehyde solution. The polyhydric aldehyde is, for example, a dialdehyde such as glutaraldehyde or terephthalaldehyde. Instead of or together with the polyhydric aldehyde, an organic cross-linking agent such as an epoxy compound and a polycarboxylic acid and / or an inorganic cross-linking agent such as a boron compound may be used as a cross-linking agent.

  The rejection (salt rejection) exhibited by the composite separation membrane of the present invention is a value at an operating pressure of 1.0 MPa with respect to a magnesium sulfate aqueous solution (concentration: 0.20% by weight, pH 6.5, temperature: 25 ° C.). 98.5% or more, and may be 99.0% or more, 99.5% or more, or even 99.7% or more, depending on the composition of polyamide and the type and amount of additives.

The permeation flux of the composite separation membrane of the present invention is, for example, 1.00 (m ³ / (m ² · day)) or more when the operating pressure is 1.0 MPa. (M ³ / (m ² · day)) or more, 1.40 (m ³ / (m ² · day)) or more, and 1.60 (m ³ / (m ² · day)) or more, and more than 1.80 (m ³ / (m ² · day)). In addition, the above-mentioned rejection value can be achieved simultaneously.

  For example, a separation membrane element is manufactured using the composite separation membrane of the present invention. As shown in FIG. 1, the separation membrane element 1 includes a composite separation membrane 31 which is the composite separation membrane of the present invention. The separation membrane element 1 is a spiral type membrane element, and a spiral is formed around a central pipe (water collecting pipe) 35 in a state where a composite separation membrane 31, a supply-side flow path material 32, and a permeation-side flow path material 33 are laminated. It has a laminate 30 wound in a shape. The separation membrane element 1 is manufactured, for example, by fixing the laminated body 30 with an end member and an exterior material (both not shown). The separation membrane element 1 is used in a state where it is loaded in a pressure vessel (vessel) as necessary.

  The composite separation membrane of the present invention can be used for the same applications as conventional composite separation membranes. Such applications are, for example, use as reverse osmosis (RO) membranes, ultrafiltration (NF) membranes, microfiltration (MF) membranes, forward osmosis (FO) membranes. More specific applications include, for example, the production of pure water or ultrapure water, desalination of brine such as seawater, wastewater treatment such as removal of harmful components or recovery of useful components, and concentration or recovery of active ingredients in the food or pharmaceutical fields. It can be used for applications such as advanced processing.

  Hereinafter, the present invention will be described in more detail with reference to examples. Note that the present invention is not limited to the embodiments described below.

  First, a method for evaluating the composite separation membrane manufactured in this example will be described.

[Rejection]
The rejection (salt rejection) of the prepared composite separation membrane was determined as follows. An aqueous solution of magnesium sulfate (MgSO ₄ ) (concentration: 0.20% by weight, temperature: 25 ° C., pH: 6.5) was passed through the composite separation membrane at an operating pressure of 1.0 MPa for 30 minutes. Conductivity measuring device (Kyoto Electronics Ltd., CM-117) with a make conductivity measurements of membrane permeate and feed, the result and the calibration curve - from (Concentration conductivity), on the basis of the following equation, MgSO ₄ Was calculated.
Rejection = (1-(MgSO ₄ concentration of MgSO ₄ concentration / feed in the membrane permeate)) × 100 (%)

[Permeate flux]
The permeation flux of the prepared composite separation membrane was determined by the following equation from the amount of the permeated liquid that was also measured when the rejection rate was evaluated.
Permeate flux (m ³ / (m ² · day)) = permeate volume / (membrane area × sampling time)

<Example 1>
0.998% by weight of piperazine hexahydrate, 0.002% by weight of N-phenylethylenediamine (PED), 0.15% by weight of sodium lauryl sulfate, 0.45% by weight of sodium hydroxide, and 0.1% by weight of polyvinyl alcohol (PVA). An aqueous solution of amine containing 25% by weight is applied to a porous polysulfone support membrane (an asymmetric membrane having an average pore diameter of 20 nm on the side where the separation function layer is formed and an average pore diameter different on the side opposite to that side) as a porous support. After application, the excess aqueous solution was removed. The ratio of piperazine to polyfunctional amine contained in the aqueous amine solution was 99.7 mol%, and the ratio of PED was 0.3 mol%. Next, an isooctane solution containing 0.9% by weight of trimesic acid chloride is brought into contact with the surface of the porous support to which the amine aqueous solution has been applied to allow the interfacial condensation polymerization reaction to proceed, and a polyamide separation function is formed on the porous support. A layer (thickness: 1 μm) was formed to obtain a composite separation membrane according to Example 1. Note that the composite separation membrane according to Example 1 was not subjected to chlorination.

The rejection (rejection of MgSO ₄ ) of the composite separation membrane according to Example 1 thus obtained was 99.9%, and the permeation flux was 1.44 (m ³ / (m ² · day)). Was.

<Examples 2 to 7, Comparative Examples 1 to 5>
Examples 2 to 7 and Comparative Examples 1 to 5 were performed in the same manner as in Example 1 except that the ratio of the piperazine and the PED to the polyfunctional amine contained in the aqueous amine solution (monomer charging ratio) was changed as shown in Table 1. Were prepared. The rejection and permeation flux of the obtained composite separation membrane are shown in Table 1 below together with the results of Example 1. In Comparative Example 5, the permeate could not be recovered.

As shown in Table 1, in Examples 1 to 7, the permeation flux was improved while maintaining the rejection of MgSO ₄ as compared with the comparative example.

<Examples 8 to 13, Comparative Examples 6 to 9>
Example 1 Example 1 was repeated except that N-methylethylenediamine (MED) was used in place of PED, and the ratio (monomer charge ratio) of piperazine and MED in the polyfunctional amine contained in the aqueous amine solution was adjusted as shown in Table 2. A composite separation membrane was produced in the same manner as described above. Table 2 below shows the MgSO ₄ rejection and permeation flux of the obtained composite separation membrane. Comparative Example 1 is shown again in Table 2 for reference.

  As shown in Table 2, in Examples 8 to 13, the permeation flux was improved while maintaining the rejection as compared with Comparative Examples.

<Examples 14 to 18, Comparative Examples 10 to 13>
In the same manner as in Example 1 except that ethylenediamine (EDA) was used instead of PED, and the ratio of the piperazine and EDA in the polyfunctional amine contained in the amine aqueous solution (monomer charging ratio) was adjusted as shown in Table 3. Thus, a composite separation membrane was prepared. Table 3 below shows the MgSO ₄ rejection and permeation flux of the obtained composite separation membrane. Comparative Example 1 is shown again in Table 3 for reference.

As shown in Table 3, in Examples 14 to 18, the permeation flux was improved while maintaining the rejection of MgSO ₄ as compared with the comparative example.

Reference Signs List 30 laminated body 31 composite separation membrane 32 supply-side flow path material 33 permeation-side flow path material 35 central pipe (water collecting pipe)

Claims (6)

A composite separation membrane,
A porous support, comprising a separation functional layer formed on the porous support,
The separation functional layer includes an aliphatic polyfunctional amine having two or more secondary amino groups, a primary amino group bonded to a terminal of a linear hydrocarbon chain, and another terminal of the linear hydrocarbon chain. Is composed of a polyamide formed by the reaction of a compound group containing a linear hydrocarbon chain-containing polyfunctional amine having a primary amino group or a secondary amino group and a polyfunctional acid halide,
The proportion of the linear hydrocarbon chain-containing polyfunctional amine in the polyfunctional amine in the compound group is less than 15 mol%,
The linear hydrocarbon chain containing polyfunctional amine, Ri least 1 Tanedea selected from N- phenyl ethylenediamine and N- methyl ethylenediamine,
When the linear hydrocarbon chain-containing polyfunctional amine is N-phenylethylenediamine, the composite separation membrane has a permeation flux of 1.6 m ³ / (m ² · day) or more at an operating pressure of 1.0 MPa. Have,
Composite separation membrane.   The composite separation membrane according to claim 1, wherein the aliphatic polyfunctional amine is an alicyclic polyfunctional amine.   3. The composite separation membrane according to claim 1, wherein the aliphatic polyfunctional amine is piperazine or a piperazine derivative.   The composite separation membrane according to claim 1, wherein the compound group further includes a hydrophilic polymer.   The composite separation membrane according to claim 4, wherein the hydrophilic polymer is polyvinyl alcohol.   A separation membrane element comprising the composite separation membrane according to claim 1.

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