JP6944044B2 - Forward osmosis membrane and its uses - Google Patents

Description

The present invention relates to a forward osmosis membrane and its use.

Semipermeable membranes are useful for selectively separating a given component from a liquid or gas mixture, and are preferably used, for example, in the production of high-purity water or in the separation of a particular solute from a solution.

Of the reverse osmosis method and the forward osmosis method, which are membrane separation methods using a semipermeable membrane, the reverse osmosis membrane is exposed to high pressure in the conventional mainstream reverse osmosis method. Therefore, the reverse osmosis membrane includes a porous support (for example, a non-woven fabric), a porous polymer layer (for example, a polysulfone layer), and a layer (skin layer, a separation layer) that actually functions as a semipermeable membrane in order to obtain high strength. , Etc.) are laminated in this order, and a composite semipermeable membrane is the mainstream.

On the other hand, in the forward osmosis method, the osmotic pressure generated between the aqueous solutions having different solute concentrations separated by the forward osmosis membrane is used as a driving force, and the draw solution having a high salt concentration from the feed solution side having a low salt concentration (for example, fresh water) is used as a driving force. Water moves to the side (eg seawater). Therefore, unlike the reverse osmosis method, it is not necessary to apply a high pressure or film strength to overcome the osmotic pressure, and it is expected to have advantages such as excellent energy saving and a simple structure of the osmotic membrane.

However, the forward osmosis method has a problem that the permeation flux is small (for example, Patent Document 1), and when a large amount of water is treated using a forward osmosis membrane for agricultural water or water purification, low salt is used. Further improvement of the permeation flux from the concentration side to the high salt concentration side is required.

Japanese Unexamined Patent Publication No. 2014-21262

According to the studies by the present inventors, the forward osmotic membrane having a large water permeation flux from the feed solution tends to have a large amount of backdiffusion of salt from the draw solution. It has also been found that the amount of backdiffusion of salt per permeated flux is not necessarily low. Therefore, it can be said that there is room for further improvement in the conventional forward osmosis membrane from the viewpoint of achieving both high water permeability and high salt inhibition rate.

According to the study by the present inventors, a semipermeable membrane containing at least two kinds of protonic acid group-containing aromatic polyether resins having different mole fractions of the structural unit having a protonic acid group (protoic acid group-containing structural unit) is used. As a result, they have found that a forward osmotic membrane having high water permeability and high salt inhibition rate can be produced, and have completed the present invention.

That is, the present invention relates to the following [1] to [15].

[1] A forward osmotic membrane comprising a semipermeable membrane and a porous substrate arranged on at least one surface thereof, wherein the semipermeable membrane is an aromatic polyether resin having a protonic acid group-containing structural unit (1). A) is contained, and the resin (A) contains a protonic acid group-containing aromatic polyether resin (A1) and a protonic acid group having a larger molar proportion of a protonic acid group-containing structural unit than the resin (A1). A forward osmotic membrane containing at least an aromatic polyether resin (A2).

[2] The forward osmosis membrane according to the above [1], wherein the semipermeable membrane is formed of a mixture containing at least the resins (A1) and (A2).

[3] The forward osmosis membrane according to the above [2], wherein the semipermeable membrane has a structure separated into at least two phases corresponding to the resins (A1) and (A2), respectively.

[4] The forward osmotic membrane according to the above [1], wherein the concentration of the protonic acid group derived from the resin (A) in the semipermeable membrane has a gradient in the thickness direction of the semipermeable membrane.

[5] The forward osmosis membrane according to the above [4], wherein the semipermeable membrane has a layer (L1) containing the resin (A1) and a layer (L2) containing the resin (A2).

[6] The resins (A1) and (A2) have a structural unit (1) represented by the following formula (1) and a structural unit (2) represented by the following formula (2), respectively. The resin (A2) has the above-mentioned [1] to [5] in which the molar fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is larger than that of the resin (A1). ] The forward osmotic membrane according to any one of the items.

［式（１）および（２）において、
Ｒ¹〜Ｒ¹⁰は、それぞれ独立して、Ｈ、Ｃｌ、Ｆ、ＣＦ₃またはＣ_mＨ_2m+1（ｍは１〜１０の整数を示す。）であり、
Ｒ¹〜Ｒ¹⁰の少なくとも１つはＣ_mＨ_2m+1（ｍは１〜１０の整数を示す。）であり、
Ｒ¹〜Ｒ¹⁰は、それぞれ芳香環に２つ以上存在してもよく、１つの芳香環にＣ_mＨ_2m+1が２つ以上存在する場合には、各Ｃ_mＨ_2m+1は互いに同一であっても異なっていてもよい。

[In equations (1) and (2)
R ^{1 to} R ¹⁰ are independently H, Cl, F, CF ₃ or C _m H _{2m + 1} (m indicates an integer of 1 to 10).
At least one of ^{R 1 to} R ¹⁰ _{is C m} H _{2m + 1} (m indicates an integer of 1 to 10).
Two or more R ^{1 to} R ¹⁰ may be present in each aromatic ring, and when two or more C _m H _{2 m + 1} are present in one _{aromatic ring, each C m} H _{2 m + 1} is present with each other. It may be the same or different.

X ^{1 to} X ⁵ are independently H, Cl, F, CF ₃ or protonic acid groups, respectively.
At ^{least one of X 1 to} X ⁵ is a protonic acid group and
Two or more of X ^{1 to} X ⁵ may be present in each aromatic ring, and when two or more proton acid groups are present in one aromatic ring, the proton acid groups are different even if they are the same as each other. May be.

A ^{1 to} A ⁶ are independently directly bonded, −CH ₂ −, −C (CH ₃ ) ₂₋ , −C (CF ₃ ) ₂₋ , −O− or −CO−, respectively.

i, j, k and l independently represent 0 or 1, respectively. ]
[7] In the entire resin (A), the molar fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is 0.1 to 0.9. The forward osmosis membrane according to [6].

[8] In the resins (A1) and (A2), the absolute value of the difference in the mole fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2), respectively, is The forward osmosis membrane according to the above [6] or [7], which is 0.03 to 0.6.

[9] The forward osmosis membrane according to any one of the above [1] to [8], wherein the aromatic polyether resin (A) has a weight average molecular weight of 70,000 or more.

[10] The forward osmosis membrane according to any one of [1] to [9], wherein the semipermeable membrane has a thickness of 3.0 μm or less.

[11] The forward osmosis membrane according to any one of [1] to [10], which has the semipermeable membrane and the porous substrate arranged on both sides thereof.

^{[12] The porous substrate has an air permeability of 100 to 400 cm 3} / cm ² / s and a thickness of 50 to 700 μm measured by the method A (Frazier method) described in JIS L 1096. 1] The forward osmosis membrane according to any one of [11].

[13] A forward osmosis membrane element comprising the forward osmosis membrane and a spacer according to any one of the above [1] to [12].

[14] A forward osmosis membrane module in which the forward osmosis membrane element according to the above [13] is housed in a container.

[15] The forward osmosis membrane module according to the above [14] and the feed solution on one surface of the forward osmosis membrane included in the forward osmosis membrane module, and the solute concentration on the other surface is higher than that of the feed solution. A system having a drive pump for flowing a draw solution and capable of moving water contained in the feed solution to the draw solution through the forward osmosis membrane.

According to the present invention, it is possible to provide a forward osmosis membrane having an excellent balance between water permeability and salt blocking rate, specifically, a forward osmosis membrane having high water permeability and high salt blocking rate.

FIG. 1 is a schematic view of an apparatus used for evaluating the separation performance of a forward osmosis membrane in the examples.

Hereinafter, the present invention will be specifically described.

[Forward osmosis membrane]
The forward osmosis membrane of the present invention includes a semipermeable membrane and a porous substrate arranged on at least one surface thereof. Here, the semipermeable membrane contains an aromatic polyether resin (A) having a protonic acid group-containing structural unit.

The forward osmotic membrane of the present invention includes the semipermeable membrane and the porous substrate arranged on at least one surface thereof, and can realize a high water permeation flux and a high salt inhibition rate. ..

<Semipermeable membrane>
The semitransparent film contains an aromatic polyether resin (A) having a protonic acid group-containing structural unit, and the resin (A) is a protonic acid group-containing aromatic polyether resin (A1) and the resin. It contains at least a protonic acid group-containing aromatic polyether resin (A2) having a larger molar proportion of the protonic acid group-containing structural unit than (A1). Hereinafter, the resins (A), (A1) and (A2) are also simply referred to as "resin (A)", "resin (A1)" and "resin (A2)", respectively.

In the present invention, the protonic acid group means a functional group that easily releases a proton or a hydrogen atom thereof substituted with Na or K, and examples thereof include a sulfonic acid group (-SO ₃ H) and a carboxylic acid. Acid group (-COOH), phosphonic acid group (-PO ₃ H ₂ ), alkyl sulfonic acid group (-(CH ₂ ) _n SO ₃ H), alkyl carboxylic acid group (-(CH ₂ ) _n COOH), alkyl phosphon Examples thereof include acid groups (-(CH ₂ ) _n PO ₃ H ₂ ), hydroxyphenyl groups (-C ₆ H ₄ OH) and those in which the terminal hydrogen atoms thereof are substituted with Na or K. n is an integer of 1-10.

The mole fraction of the protonic acid group-containing structural unit is the following ratio: the number of protonic acid group-containing structural units / the total number of structural units constituting the aromatic polyether resin. Further, as the protonic acid group-containing structural unit, for example, a structural unit (1) represented by the formula (1) described later can be mentioned.

Since at least two kinds of aromatic polyether resins having different mole fractions of the protonic acid group-containing structural units are used in the present invention, the resin (A2) having a large mole fraction of the protonic acid group-containing structural units. As a result, the water permeability is improved, and the back diffusion of the salt can be prevented by the resin (A1) having a small mole fraction of the protonic acid group-containing structural unit.

In particular, since both the resin (A1) and the resin (A2) are aromatic polyether resins, it is considered that their dispersion is good. For this reason, it is considered that a dense and multi-step pseudo (A1) / (A2) unit continuous layer is formed, so that the water permeation characteristics and the effect of suppressing salt backdiffusion can be efficiently exhibited. Probably.

In one embodiment, the semipermeable membrane preferably has a gradient in the concentration of protonic acid groups derived from the resin (A) in the thickness direction of the semipermeable membrane. The concentration gradient may be a mode in which the concentration continuously increases, or a mode in which the concentration increases stepwise. As an example thereof, for example, the semipermeable membrane is a laminated membrane having a layer (L1) containing a resin (A1) and a layer (L2) containing a resin (A2). The ratio of the thickness of the layer (L1) to the layer (L2) (thickness of L1: thickness of L2) is usually 5:95 to 80:20, preferably 20:80 to 60:40. Such a multilayer structure provides a higher water permeation flux and salt blocking rate.

It can be said that this aspect is a preferable aspect from the viewpoint of more reliably expressing the effect of the above-mentioned (A1) / (A2) unit configuration.

Here, the concentration gradient of the protonic acid group derived from the resin (A) means that the concentration of the protonic acid group contained in the resin (A) changes in the thickness direction of the semipermeable membrane. When the protonic acid group is a sulfone group or a group in which the terminal hydrogen atom thereof is substituted with Na or K, the concentration gradient can be confirmed by analyzing the concentration distribution of sulfur atoms in the semipermeable membrane cross section by element mapping.

Here, when the forward osmosis membrane is used, the forward osmosis membrane is arranged so that the side having a high protonic acid group concentration faces the feed solution side and the side having a low protonic acid group concentration faces the draw solution side in the semipermeable membrane. Is preferable. For example, in the semipermeable membrane, the forward osmosis membrane is arranged so that the layer (L2) containing the resin (A2) faces the feed solution side and the layer (L1) containing the resin (A1) faces the draw solution side. It is preferable to do so. In such an embodiment, a higher water permeation flux and salt inhibition rate can be obtained.

In one embodiment, the semipermeable membrane is preferably formed from a mixture containing at least a resin (A1) and a resin (A2). As an example, the semipermeable membrane has a structure separated into at least two phases corresponding to each of the resin (A1) and the resin (A2). This phase-separated structure provides higher water permeation flux and salt blockage. In the mixture, the mass ratio (A1: A2) of the resin (A1) and the resin (A2) is usually 10:90 to 90:10, preferably 30:70 to 70:30.

Such a phase-separated structure can be confirmed by observation with an electron microscope (TEM or SEM). As the phase-separated structure, a sea-island structure, an interpenetrating structure, and the like can be considered, but the interpenetrating structure is more preferable from the viewpoint of preventing the backdiffusion of the salt from the draw solution. Further, in the case of a sea-island structure, it is preferable that the resin (A1) having a small mole fraction of the protonic acid group-containing structural unit forms a sea phase, and the resin (A2) having a large mole fraction forms an island phase. ..

In the present invention, a semipermeable membrane using the aromatic polyether resin (A) as a raw material can be produced as a self-supporting membrane, and by laminating this semipermeable membrane and the porous base material, water permeability is high. , A forward osmotic membrane having a high salt blocking rate can be obtained.

The semipermeable membrane is substantially composed of only the aromatic polyether resin (A), but the other components are contained in a small amount (for example, 1% by mass or less, or 0.1% by mass) so as not to impair the effect of the present invention. The following) may be included.

The thickness of the semipermeable membrane is usually 3.0 μm or less, preferably 0.01 to 3.0 μm, and more preferably 0.01 to 1.5 μm. A forward osmotic membrane using a semipermeable membrane whose thickness is within this range has sufficient membrane strength and exhibits a practically sufficiently large permeation flux of water. The thickness of the semipermeable membrane can be controlled by the manufacturing conditions of the semipermeable membrane, for example, the temperature and pressure during press molding, the varnish concentration during casting, the coating thickness, and the like.

It is preferable that the semipermeable membrane has as little unevenness in thickness as possible. Since pressure is applied to the semipermeable membrane when water is permeated, stress concentration may occur if the thickness is uneven. Therefore, when used as a water separation membrane, the durability as a membrane may decrease.

(Aromatic polyether resin (A))
The semipermeable membrane comprises an aromatic polyether resin (A) having a protonic acid group-containing structural unit. The resin (A) contains at least the above-mentioned resins (A1) and (A2).

The resins (A1) and (A2) preferably have a structural unit (1) represented by the following formula (1) and a structural unit (2) represented by the following formula (2), respectively. Here, with respect to the mole fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2), the mole fraction of the resin (A2) is higher than the mole fraction of the resin (A1). Is also preferable.

Here, the structural unit (1) in these resins (A1) and (A2) may be the same or different, and the structural unit (2) in the resins (A1) and (A2) may be the same or different. ..

式（１）および（２）において、
ｉ，ｊ，ｋおよびｌは、それぞれ独立して、０または１を示す。

In equations (1) and (2)
i, j, k and l independently represent 0 or 1, respectively.

R ^{1 to} R ¹⁰ are independently H, Cl, F, CF ₃ or C _m H _{2 m + 1} (m indicates an integer of 1 to 10), and C _m H 2 m + 1 is used as _{C m H 2 m + 1.} For example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group can be mentioned.

At least one of ^{R 1 to} R ¹⁰ _{is C m} H _{2m + 1} (m represents an integer of 1 to 10). Specifically, i, j, k and l and R ^{1 to} R ¹⁰ contain at least a group in which the structural unit (1) and / or the structural unit (2) is _{represented by C m} H _{2 m + 1.} Selected to have one. That is, when i, j, k and l are all 1, at least one of ^{R 1 to} R ¹⁰ _{is C m} H _{2 m + 1} , but for example i = 0, j = 1, k = 0 and l. When = 1, at least one of ^{R 1 to} R ³ , R ^{5 to} R ⁸ and R ¹⁰ _{is C m} H _{2 m + 1} .

Two or more R ^{1 to} R ¹⁰ may be present in each aromatic ring, and when two or more C _m H _{2 m + 1} are present in one _{aromatic ring, each C m} H _{2 m + 1} is present with each other. It may be the same or different.

X ^{1 to} X ⁵ are independently H, Cl, F, CF ₃ or protonic acid groups.

At ^{least one of X 1 to} X ⁵ is a protonic acid group. Specifically, i and j and X ^{1 to} X ⁵ are selected such that the structural unit (1) has at least one protonic acid group. That is, when i = 1 and j = 1, ^{at least one of X 1 to} X ⁵ is a protonic acid group, but when j = 0 ^{, at least one of X 1 to} X ³ is a protonic acid group. , I = 0 and j = 1 ^{, at least one of X 1 to} X ³ and X ⁵ is a protonic acid group.

Two or more of X ^{1 to} X ⁵ may be present in each aromatic ring, and when two or more proton acid groups are present in one aromatic ring, the proton acid groups are different even if they are the same as each other. May be.

A ^{1 to} A ⁶ are independently directly bonded, −CH ₂ −, −C (CH ₃ ) ₂₋ , −C (CF ₃ ) ₂₋ , −O− or −CO−, and A ¹ At least one of ~ A ⁶ is preferably −CO−.

The lines at both ends of equations (1) and (2) indicate the connection with adjacent structural units.

In the present invention, the protonic acid group means a functional group that easily releases a proton or a hydrogen atom thereof substituted with Na or K, and examples thereof include a sulfonic acid group (-SO ₃ H) and a carboxylic acid. Acid group (-COOH), phosphonic acid group (-PO ₃ H ₂ ), alkyl sulfonic acid group (-(CH ₂ ) _n SO ₃ H), alkyl carboxylic acid group (-(CH ₂ ) _n COOH), alkyl phosphon Examples thereof include acid groups (-(CH ₂ ) _n PO ₃ H ₂ ), hydroxyphenyl groups (-C ₆ H ₄ OH) and those in which the terminal hydrogen atoms thereof are substituted with Na or K. n is an integer of 1-10. Examples of the protonic acid _{group, -C n 'H 2n' -SO} 3 Y (n ' is an integer of 0, preferably 0, Y is H, Na or K) are preferred.

Examples of the structural unit (1) include structural units represented by the following equation (1-1) or the following equation (1-2), and in these structures, A ¹ is −CO−. Is preferable

さらに具体的には下式（１−３）または下式（１−４）で表される構造単位が挙げられる。

More specifically, structural units represented by the following equation (1-3) or the following equation (1-4) can be mentioned.

（式中、Ｚはそれぞれ独立に前記プロトン酸基であり、ｓはそれぞれ独立に０〜３の整数であり、ｔはそれぞれ独立に０〜４の整数であり、両末端の線は隣り合う構造単位との結合を示す。これら以外の記号の定義は前述したとおりである。）
また、構造単位（２）の例としては、下式（２−１）または下式（２−２）で表される構造単位が挙げられ、

(In the formula, Z is the protonic acid group independently, s is an integer of 0 to 3 independently, t is an integer of 0 to 4 independently, and the lines at both ends are adjacent to each other. Indicates a combination with a unit. Definitions of symbols other than these are as described above.)
Further, as an example of the structural unit (2), a structural unit represented by the following equation (2-1) or the following equation (2-2) can be mentioned.

さらに具体的には、下式（２−３）または下式（２−４）で表される構造単位が挙げられる。

More specifically, structural units represented by the following equation (2-3) or the following equation (2-4) can be mentioned.

（式中、ｔはそれぞれ独立に０〜４の整数であり、両末端の線は隣り合う構造単位との結合を示す。ｔ以外の記号の定義は前述したとおりである。）
樹脂（Ａ）全体において、前記構造単位（１）および前記構造単位（２）の合計量に対する前記構造単位（１）のモル分率は、水透過性の高い半透膜を形成できることから、好ましくは０．１以上、より好ましくは０．２以上、さらに好ましくは０．２５以上であり；また、塩阻止率が高く、かつゲル化しない半透膜を形成できることから、好ましくは０．９以下、より好ましくは０．７以下、さらに好ましくは０．６以下である。

(In the formula, t is an integer of 0 to 4 independently, and the lines at both ends indicate the connection with the adjacent structural unit. The definitions of symbols other than t are as described above.)
In the entire resin (A), the mole fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is preferable because a semipermeable membrane having high water permeability can be formed. Is 0.1 or more, more preferably 0.2 or more, still more preferably 0.25 or more; and because it has a high salt inhibition rate and can form a semipermeable membrane that does not gel, it is preferably 0.9 or less. , More preferably 0.7 or less, still more preferably 0.6 or less.

From the viewpoint of the balance between water permeability and salt inhibition rate in the mole fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2), the molar fraction of the resin (A1). The absolute value of the difference between the fraction and the mole fraction of the resin (A2) is preferably 0.03 to 0.6, more preferably 0.1 to 0.4.

In the above specification of the difference in mole fraction, the aromatic polyether resin contained in the resin (A) is not limited to two types. When the resin (A) contains three or more kinds of aromatic polyether resins having different mole fractions of the structural unit (1), the above-mentioned provision of the difference in the mole fraction of the structural unit (1) is at least one set of ". It suffices to be filled with "two kinds of aromatic polyether resins".

The aromatic polyether resin (A) may further contain a structural unit derived from a polyfunctional compound described later. The aromatic polyether resin (A) may be a crosslinked product or a non-crosslinked product.

The weight average molecular weight (Mw) of the aromatic polyether resin (A) measured by the GPC (Gel Permeation Chromatography) method under the following conditions (1) to (6) is preferably 70,000 or more. It is preferably 80,000 or more, more preferably 90,000 or more. When the molecular weight is in the above range, the obtained semipermeable membrane has high mechanical properties and is not easily torn during film formation or use. The weight average molecular weight is preferably 180,000 or less from the viewpoint of gel generation rate.

(1) Measurement temperature: 40 ° C
(2) Developing solvent: N, N-dimethylformamide (DMF)
(3) Flow rate: 1.0 ml / min
(4) Injection amount: 500 μl
(5) Detector: UV detector
(6) Molecular weight standard substance: Standard polystyrene The weight average molecular weight shall be controlled by adjusting the molar ratio of the raw material monomer and the amount of the terminal encapsulant when producing the aromatic polyether resin (A). Can be done.

The protonic acid group equivalent of the aromatic polyether resin (A), that is, the mass of the aromatic polyether resin (A) per mole of the protonic acid group was insoluble in water or methanol, and swelling was suppressed. Since a semitransparent film having a small amount of film permeation can be obtained, it is preferably 200 g / mol or more. Further, since a semipermeable membrane having a large permeation flux of water and high economy can be obtained, it is preferably 5000 g / mol or less, more preferably 1000 g / mol or less.

(Manufacturing method of aromatic polyether resin (A))
The aromatic polyether resin (A) can be obtained by condensation of a monomer having an aromatic ring according to a conventionally known method (for example, the method described in International Publication No. 2003/3566). For example, the following equations (1a) and (2a)

で表されるハロゲン置換基を有する単量体と、下式（１ｂ）および（２ｂ）：

A monomer having a halogen substituent represented by the following formulas (1b) and (2b):

で表される水酸基を有する単量体との縮合重合によって、前記樹脂を得ることができる。

The resin can be obtained by condensation polymerization with a monomer having a hydroxyl group represented by.

In the formula, Y is a halogen atom, and the meaning of each of the other codes is the same as the meaning of the same code used in the above formulas (1) and (2). Preferred examples of the halogen atom include fluorine and chlorine.

It is preferable to use a basic catalyst such as K ₂ CO _{3 for condensation.}

Examples of the monomer represented by the above formula (1a) ( ^{where at least one of X 1 to} X ² is a protonic acid group) include 5,5'-carbonylbis (2-fluorobenzenesulfonic acid). Examples thereof include protonic acid group-containing aromatic dihalide compounds such as sodium) and 5,5'-carbonylbis (sodium 2-chlorobenzenesulfonate).

Examples of the monomer represented by the above formula (2a) include, for example.
4,4'-difluorobenzophenone, 3,3'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 3,3'-dichlorobenzophenone, 4,4'-difluorobiphenyl, 4,4'-difluorodiphenylmethane, 4, Aromatic dihalide compounds such as 4'-dichlorodiphenylmethane, 4,4'-difluorodiphenyl ether; and 3,3'-dimethyl-4,4'-difluorobenzophenone, 3,3'-diethyl-4,4'-difluorobenzophenone , 3,3', 5,5'-tetramethyl-4,4'-difluorobenzophenone, 3,3'-dimethyl-4,4'-dichlorobenzophenone, 3,3', 4,4'-tetramethyl- Examples thereof include alkyl group-containing aromatic dihalide compounds such as 5,5'-dichlorobenzophenone.

Monomer represented by the formula (2b) (or the monomer (however represented by the formula (1b), X ³ to X ⁵ are those wherein all hydrogen atoms.)) As, for example,
4,4'-Dihydroxybiphenyl, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxybenzophenone, 2,2-bis (4-hydroxyphenyl) propane, 1,1,1 , 3,3,3-hexafluoro-2,2-bis (4-hydroxyphenyl) propane, 1,4-bis (4-hydroxyphenyl) benzene, α, α'-bis (4-hydroxyphenyl) -1 , 4-Dimethylbenzene, α, α'-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -1,3-diisopropylbenzene, 1,4- Aromatic dihydroxy compounds such as bis (4-hydroxybenzoyl) benzene, 3,3'-difluoro-4,4'-dihydroxybiphenyl; and 3,3'-dimethyl-4,4'-dihydroxybiphenyl, 3,3'. , 5,5'-tetramethyl-4,4'-dihydroxybiphenyl, 3,3'-dimethyl-4,4'-dihydroxydiphenylmethane, 3,3', 5,5'-tetramethyl-4,4'- Dihydroxydiphenylmethane (also known as bis (3,5-dimethyl-4-hydroxyphenyl) methane), 3,3', 5,5'-tetraethyl-4,4'-dihydroxydiphenylmethane, 3,3'-dimethyl-4, 4'-Dihydroxydiphenyl ether, 3,3', 5,5'-tetramethyl-4,4'-dihydroxydiphenyl ether, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis ( 3-Ethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, α, α'-bis (3-methyl-4-hydroxyphenyl) -1,4 -Diisopropylbenzene, α, α'-bis (3,5-dimethyl-4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α'-bis (3-methyl-4-hydroxyphenyl) -1,3 Examples thereof include alkyl group-containing aromatic dihydroxy compounds such as −diisopropylbenzene and α, α'-bis (3,5-dimethyl-4-hydroxyphenyl) -1,3-diisopropylbenzene.

A polyfunctional compound may be copolymerized with the monomer as long as the solvent solubility of the aromatic polyether resin (A) is not impaired. By copolymerizing the polyfunctional compound, the aromatic polyether resin (A) can have a microcrosslinked structure. Examples of the polyfunctional compound include those having three or more hydroxyl groups in one molecule, for example, (2,4-dihydroxyphenyl) (4-hydroxyphenyl) methanone, 4- [1- (4-hydroxyphenyl) -1. -Methylethyl] -1,3-benzenediol, 4-[(2,3,5-trimethyl-4-hydroxyphenyl) methyl] -1,3-benzenediol, 4-[(4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, (4-hydroxyphenyl) (2,3,4-trihydroxyphenyl) methanone, 4-[(3,5-dimethyl-4-hydroxyphenyl) methyl] -1,2 , 3-benzenetriol, 4-[(2,3,5-trimethyl-4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4,4'-[1,4-phenylenebis (1-) Methylethylidene)] bis [benzene-1,2-diol], 5,5'-[1,4-phenylene bis (1-methylethylidene)] bis [benzene-1,2,3-triol], α, α , Α'-Tris (4-hydroxyphenyl) -1-ethyl-4-isopropylbenzene, fluoroglucin, pyrogallol and the like.

These copolymerization amounts are preferably from the viewpoint of preventing a decrease in the solvent solubility of the aromatic polyether resin (A), a decrease in the fluidity of the resin during film formation, and a decrease in the elongation rate of the semitransparent film. 0 to 8 mol% / total OH equivalent (that is, 0 to 0 out of the total amount (100 mol%) of OH groups contained in the monomer of the above formula (1b), the monomer of the formula (2b) and the polyfunctional monomer. 8 mol% is an OH group derived from a polyfunctional monomer), more preferably 0 to 5 mol% / total OH equivalent.

(Varnish of aromatic polyether resin (A))
Since the molecular structure of the aromatic polyether resin (A) is basically linear and the amount thereof is small even if it has a crosslinked structure derived from the polyfunctional compound, it is solvent-soluble. Excellent in sex. Therefore, it can be in the form of a varnish in which the resin (A) is dissolved in a solvent.

Examples of the solvent are not particularly limited, and alcohols such as water, methanol, ethanol, 1-propanol, 2-propanol and butanol, hydrocarbons such as toluene and xylene, and halogenated carbides such as methyl chloride and methylene chloride are used. Hydrogens, dichloroethyl ethers, ethers such as 1,4-dioxane and tetrahydrofuran, fatty acid esters such as methyl acetate and ethyl acetate, ketones such as acetone and methyl ethyl ketone, cellosolves such as 2-methoxyethanol and 2-ethoxyethanol. Examples include aprotonic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and dimethyl carbonate. These can be used alone or in admixture of two or more. Among them, lower alcohols (methanol, ethanol, 1-propanol, 2-propanol, t-butyl alcohol, etc.), tetrahydrofuran, N, N-dimethylformamide, N-methyl-2-pyrrolidone, etc. are preferable because they are water-soluble. Further, a mixed solvent of these and water is also preferable. The resin concentration in the varnish can be selected depending on the method of using the varnish, but is preferably 1% by mass or more and 80% by mass or less.

<< Tension elastic modulus, tensile breaking strength and elongation >>
The tensile elastic modulus of the semipermeable membrane is preferably 0.8 to 2.0 GPa, more preferably 1.2 to 1.6 GPa. The tensile breaking strength of the semipermeable membrane is preferably 40 MPa or more, and the upper limit thereof is, for example, 100 MPa. The elongation rate of the semipermeable membrane is preferably 40% or more, and the upper limit thereof is, for example, 200%. These tensile elastic modulus, tensile breaking strength and elongation rate are those measured under the following conditions.

Prepare a test piece of length x width x thickness = 100 mm x 10 mm x 5 μm, pull it at a speed of 50 mm / min using a tensile tester, and test the strength (tensile load value) when the test piece is cut (broken). (Value divided by the cross-sectional area of one piece) and the elongation rate are obtained.

The growth rate is calculated by the following formula.

Elongation rate (%) = 100 x (L-L ₀ ) / L ₀
(L ₀ : Test piece length before test L: Test piece length at break)
The tensile elastic modulus is a value obtained by dividing the load at break by the cross-sectional area of the test piece and the strain amount at break, that is, (L−L ₀ ) / L _0.

The tensile strength at break and the elongation rate can be increased, for example, by increasing the molecular weight of the aromatic polyether resin (A).

<< Solubility and mass reduction rate >>
The solubility of the semipermeable membrane in dimethyl sulfoxide (hereinafter, also referred to as "DMSO") and water can be evaluated by the following mass reduction rates. The mass reduction rate is preferably less than 2% by mass, more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less.

The semipermeable membrane is allowed to stand at 150 ° C. for 4 hours in a nitrogen atmosphere to dry, and then weighed. The semipermeable membrane is immersed in DMSO or water and allowed to stand at 25 ° C. for 24 hours. The semipermeable membrane is removed from DMSO or water, allowed to stand at 150 ° C. for 4 hours in a nitrogen atmosphere, dried, and then weighed. Based on the mass before and after immersion of the semipermeable membrane, the mass reduction rate is calculated from the following formula.

Mass reduction rate = (mass before immersion of semipermeable membrane-mass after immersion of semipermeable membrane) / mass before immersion of semipermeable membrane x 100
The dissolved amount can be reduced, for example, by cross-linking the protonic acid group-containing aromatic polyether resin, and therefore the dissolved amount can be within the above range even if the proton acid group equivalent is small.

(Manufacturing method of semipermeable membrane)
The semipermeable membrane can be produced as a self-supporting membrane from the aromatic polyether resin (A) having a protonic acid group-containing structural unit.

The semipermeable membrane can be easily produced by press-molding or extruding the aromatic polyether resin (A). Further, the film of the aromatic polyether resin (A) may be subjected to a stretching treatment or the like.

The semipermeable membrane can also be produced from the above-mentioned varnish by a casting method. That is, a semipermeable membrane can be obtained by applying the varnish on the support and volatilizing and removing the solvent. Further, the semipermeable membrane may be peeled off from the support to form a self-supporting membrane.

If an organic solvent or the like at the time of casting remains in the semipermeable membrane, the mechanical strength of the semipermeable membrane may decrease and the semipermeable membrane may be easily damaged. Therefore, it is preferable that the semipermeable membrane produced by the casting method is sufficiently dried and / or washed with water, an aqueous sulfuric acid solution, hydrochloric acid or the like.

When the protonic acid group of the aromatic polyether resin (A) used for producing the semitransparent film has a hydrogen atom substituted with Na or K in a functional group that easily releases a proton. , A film of the aromatic polyether resin (A) may be formed, and then Na or K of the protonic acid group may be replaced with a hydrogen atom by contacting the film with an aqueous solution of hydrochloric acid or sulfuric acid.

The semipermeable membrane in which the concentration of the protonic acid group described above has a gradient in the thickness direction of the semipermeable membrane, specifically, the laminated membrane forms, for example, a layer (L1) containing a resin (A1). It can be obtained by subsequently forming a layer (L2) containing a resin (A2) on the layer (L1), and also forming a layer (L2) containing a resin (A2), followed by the above. It can also be obtained by forming a layer (L1) containing a resin (A1) on the layer (L2). Each layer can be obtained by, for example, press molding, extrusion molding, or casting method.

Further, the semitransparent film formed from the above-mentioned mixture containing at least the resins (A1) and (A2) is obtained by, for example, press-molding or extruding a mixed resin containing at least the resin (A1) and the resin (A2). It can also be obtained by applying and drying a varnish containing at least the resin (A1) and the resin (A2). Here, the size of the phase-separated structure can be adjusted by the stirring speed of the mixed resin or the varnish.

<Porous medium>
The air permeability of the porous substrate ^{is preferably 100 to 400 cm 3} / cm ² / s. This air permeability is measured as follows based on the A method (Frazier type method) described in JIS L 1096.

A 20 cm × 20 cm test piece is attached to the testing machine, the suction fan and the air hole are adjusted so that the inclined barometer has a pressure of 125 Pa, and the pressure indicated by the vertical barometer is measured. From the measured pressure and the type of air holes, determine the amount of air passing through the test piece from the conversion table attached to the tester.

The thickness of the porous substrate is usually 50 to 700 μm, preferably 80 to 600 μm, and more preferably 100 to 500 μm.

As the forward osmosis membrane, a thin porous substrate having such high air permeability is preferably used, so that the concentration polarization generated inside the porous substrate when the forward osmosis membrane is used is suppressed, and water is used. It is considered that the fluid resistance when permeating through the forward osmosis membrane can be reduced, and as a result, the permeation flux of water in the forward osmosis membrane can be increased. The air permeability and thickness of the porous substrate can be controlled by a conventional method.

Preferred materials constituting the porous base material include synthetic resins and natural fibers.

Examples of the synthetic resin include a thermoplastic resin and a thermosetting resin, and the thermoplastic resin is preferable. Specific examples of the thermoplastic resin include olefin polymers, polyester resins, polyamide resins, polyvinyl chlorides, and (meth) acrylic resins. Among these, olefin-based polymers and polyester resins are preferable, and olefin-based polymers are particularly preferable.

Specifically, the olefin-based polymer is a homopolymer or copolymer of an α-olefin, or a copolymer of an α-olefin and another monomer. Examples of the α-olefin include α-olefins having 2 to 8 carbon atoms such as ethylene, propylene and 1-butene. Olefin-based polymers include polypropylene, polyethylene, poly1-butene, poly4-methyl-1-pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, and ethylene / 4-methyl-1-pentene. Copolymers, propylene / 1-butene copolymers, polyolefin resins such as 4-methyl-1-pentene / 1-decene copolymers, α-olefins such as ethylene / vinyl alcohol copolymers, and other monomers Contains copolymers.

Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate. Examples of the polyamide resin include nylon 6 and nylon 66.

Examples of natural fibers include plant fibers such as cotton and hemp, and animal fibers such as silk and wool. Of these, cotton and silk are preferred.

Examples of the porous base material include woven fabrics, non-woven fabrics, cloth-based materials such as knitted fabrics, foam sheets, and the like. Among them, cloth-based materials are preferable, woven fabrics and non-woven fabrics are more preferable, and non-woven fabrics are particularly preferable.

Examples of the non-woven fabric include long-fiber non-woven fabric by the spunbond method, short-fiber non-woven fabric by the melt blown method, long-fiber non-woven fabric such as flash-spun non-woven fabric, spunlace non-woven fabric, air-laid non-woven fabric, thermal bond non-woven fabric, needle punch non-woven fabric, and chemical bond non-woven fabric. However, spunbonded non-woven fabrics and melt-blown non-woven fabrics are preferable. Of these, spunbonded non-woven fabrics are preferable, and polyethylene terephthalate or polypropylene spunbonded non-woven fabrics are particularly preferable.

The non-woven fabric may be a core-sheath type or side-by-side type composite fiber in which the constituent fibers are composite fibers made of different resins and different resins are arranged on the outer surface side of the fibers. Examples of the composite fiber include a polyethylene / polypropylene core-sheath type or side-by-side type composite fiber.

The non-woven fabric may be a laminated non-woven fabric. Examples of the laminated non-woven fabric include a laminated non-woven fabric including a spunbonded non-woven fabric and a melt-blown non-woven fabric, in which a spun-bonded non-woven fabric and a melt-blown non-woven fabric are laminated (SM), and a spun-bonded non-woven fabric, a melt-blown non-woven fabric and a spunbonded non-woven fabric are used. Examples thereof include those laminated in order (SMS).

In order to obtain such a laminated non-woven fabric, a spunbonded non-woven fabric and a melt-blown non-woven fabric are laminated and both are integrally formed. Examples of the method of integrating are a method of superimposing a spunbonded non-woven fabric and a melt blown non-woven fabric and heating and pressurizing them, a method of adhering them with an adhesive such as a hot melt adhesive or a solvent-based adhesive, and a method of adhering them on a spunbonded non-woven fabric. Examples thereof include a method of depositing fibers by a melt blown method and heat-sealing them.

The non-woven fabric may be a laminated non-woven fabric in which a porous film having micropores is sandwiched between the non-woven fabrics. Examples of such a laminated non-woven fabric include polypropylene (PP) non-woven fabric, porous PP film, and PP non-woven fabric (SFS) laminated in this order, PP non-woven fabric, porous PP film, and rayon PP non-woven fabric (SFR). ) And are laminated in this order.

Basis weight of the nonwoven fabric (basis weight of the laminated nonwoven fabric in the case of a layered nonwoven fabric) is preferably 10 to 80 g / m ^2, more preferably about 20 to 40 g / m ² approximately.

The forward osmosis membrane of the present invention may be provided with the porous substrate on both sides of the semipermeable membrane. In this embodiment, the strength of the forward osmosis membrane is further improved.

The forward osmosis membrane of the present invention contains layers other than the porous base material on both sides or one side of the semipermeable membrane in the order of the semipermeable membrane / the layer other than the porous base material / the porous base material. However, it is preferable that a layer other than the porous substrate is not included from the viewpoint of obtaining a good permeation flux. A polyamide layer may be included as a layer other than the porous substrate, but the thickness thereof is preferably 100 μm or less.

<Manufacturing method of forward osmosis membrane>
The forward osmosis membrane can be manufactured, for example, by manufacturing the semipermeable membrane as a self-supporting membrane and sandwiching the semipermeable membrane between two porous substrates from both sides thereof.

Specifically, the forward osmosis membrane can be produced by the following procedure. For example, a dilute solution of the aromatic polyether resin (A) is applied onto a substrate made of PET or the like so that the thickness after drying becomes the desired thickness, and after drying, the formed film is peeled off as a self-supporting film. The free-standing membrane can be sandwiched between two porous substrates such as non-woven fabric to produce a forward osmosis membrane. When the area of the forward osmosis membrane is large, in order to maintain the distance between the semipermeable membrane and the porous substrate, both are adhered with an adhesive so as not to affect the permeation flux. May be good.

The forward osmosis membrane can also be manufactured by producing the semipermeable membrane as a self-supporting membrane and laminating it on the porous substrate. At this time, the two may be bonded together using an adhesive.

According to the above-mentioned manufacturing method, the semipermeable membrane described above is first manufactured as a self-supporting membrane, and this is laminated on a porous base material (non-woven fabric or the like) or sandwiched between two porous base materials (non-woven fabric or the like). Therefore, since the forward osmosis membrane is produced, the thickness of the semipermeable membrane is controlled, and the forward osmosis membrane exhibiting high water permeability and high salt blocking rate can be easily produced.

[Use of forward osmosis membrane]
The forward osmosis membrane element of the present invention comprises the above-mentioned forward osmosis membrane and spacer of the present invention. In other words, the forward osmosis membrane element of the present invention is a conventional forward osmosis membrane element provided with a forward osmosis membrane and a spacer, in which the forward osmosis membrane of the present invention is used as the forward osmosis membrane. As the spacer, a conventionally known spacer used for the forward osmosis membrane element can be used.

The forward osmosis membrane module of the present invention comprises the forward osmosis membrane element of the present invention in a container. In other words, the forward osmosis membrane module of the present invention uses the forward osmosis membrane element of the present invention as the forward osmosis membrane element in the conventional forward osmosis membrane element in which the forward osmosis membrane element is housed in a container. .. As the container, a conventionally known container used for the forward osmosis membrane module can be used.

The system of the present invention has a forward osmosis membrane module of the present invention, and a feed solution (FS) on one surface of the forward osmosis membrane of the present invention included in the forward osmosis membrane module, and a feed solution on the other surface. It has a drive pump for flowing a draw solution (DS) having a high solute concentration such as salt, and is configured to be able to move water contained in the feed solution to the draw solution through the forward osmosis membrane. There is.

With such a device, pressure can be applied from the FS side to the DS side. In the aspect of the present invention, it may be preferable to apply a pressure from the FS side to the DS side. For example, if a pressure of 15 kPa or less, more preferably 12 kPa or less, still more preferably 10 kPa or less is applied from the FS side to the DS side. It may be preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The contents of the abbreviations used in this embodiment are shown.

(1) Solvent DMSO: Dimethyl sulfoxide DMF: N, N-dimethylformamide (2) Constituents of aromatic polyether DFBP: 4,4'-difluorobenzophenone DSDFBP:
5,5'-carbonylbis (sodium 2-fluorobenzenesulfonate)
TMBPF:
The test methods for various tests of 3,3', 5,5'-tetramethyl-4,4'-dihydroxydiphenylmethane are as follows.

Resin Evaluation-Weight Average Molecular Weight (Mw)
Using the GPC (Gel Permeation Chromatography) method, the weight average molecular weight (Mw) was determined under the following conditions.

(1) Measurement temperature: 40 ° C
(2) Developing solvent: DMF
(3) Flow rate: 1.0 ml / min
(4) Injection amount: 500 μl
(5) Detector: UV detector
(6) Molecular Weight Standard Material: Standard Polystyrene More specifically, the high performance liquid chromatograph (HPLC) used for the GPC measurement uses the following devices in combination by a conventional method.
HPLC: Shimadzu RID-10A-LC-10AT type system Column oven: Shimadzu CTO-10A type equipment
UV detector: 875-UV type device guard column manufactured by JASCO Corporation (JASCO): MD-G type column manufactured by Nitto Denko Corporation
GPC column: Two KD805M type columns, one KD8025 type column, and one 802 type column manufactured by Nitto Denko were connected in series and used.

Evaluation of Semipermeable Membrane-Thickness The thickness of the semipermeable membrane was measured using a spectrophotometer (elypsometri) manufactured by JASCO Corporation. Specifically, when light is incident on a film having a refractive index n at a certain angle (θ), the reflected light A from the front surface of the film and the reflected light B from the back surface interfere with each other to generate a wavy interference spectrum. The thickness (d) was calculated from Eq. (1) by counting the number (Δm) of the peaks (peaks or valleys) of the interference spectrum within a certain wavelength range (λ _{1 to λ 2).}

（単量体合成例１）
特開２０１４−５３３号公報の［００６１］段落（合成例１）に記載の方法で、下式で表されるＤＳＤＦＢＰの白色結晶を得た。収量は１５５．２ｇ（０．３８６ｍｏｌ、収率７０％）であった。

(Monomer Synthesis Example 1)
White crystals of DSDFBP represented by the following formula were obtained by the method described in paragraph [0061] (Synthesis Example 1) of JP-A-2014-533. The yield was 155.2 g (0.386 mol, yield 70%).

（樹脂合成例１）
窒素導入管、温度計、還流冷却器、及び撹拌装置を備えた５つ口反応器に、単量体合成例１で得られたＤＳＤＦＢＰ６４．２ｇ（０．１５２ｍｏｌ）、ＤＦＢＰ４９．８ｇ（０．２２８ｍｏｌ）、ＴＭＢＰＦ９７．４ｇ（０．３８０ｍｏｌ）および炭酸カリウム６５．７ｇ（０．４７５ｍｏｌ）を秤取した。これにＤＭＳＯ８４５．４ｇとトルエン２８１．８ｇを加え、窒素雰囲気下で撹拌し、１３０℃で１２時間加熱し、生成する水を系外に除去した後、トルエンを留去した。

(Resin Synthesis Example 1)
DSDFBP 64.2 g (0.152 mol) and DFBP 49.8 g (0.228 mol) obtained in Monomer Synthesis Example 1 were placed in a five-port reactor equipped with a nitrogen introduction tube, a thermometer, a reflux condenser, and a stirrer. ), TMBPF 97.4 g (0.380 mol) and potassium carbonate 65.7 g (0.475 mol) were weighed. To this, DMSO 845.4 g and toluene 281.8 g were added, stirred in a nitrogen atmosphere, heated at 130 ° C. for 12 hours, the water produced was removed from the system, and then toluene was distilled off.

Subsequently, the reaction was carried out at 160 ° C. for 12 hours to obtain a viscous polymer solution. After diluting by adding 570 g of toluene to the obtained solution, it is discharged to 2400 g of methanol, the precipitated polymer powder is filtered, washed, and dried at 150 ° C. for 4 hours to 168.7 g of polyether ketone powder (yield 86%). ) (Resin 1) was obtained.

The resin 1 is used as the structural unit (1).

で表される構造を、前記構造単位（２）として

The structure represented by is used as the structural unit (2).

で表される構造を有している。ここで、前記構造単位（１）：前記構造単位（２）＝４０ｍｏｌ：６０ｍｏｌである。また、Ｍｗ＝１２６，０００であった。

It has a structure represented by. Here, the structural unit (1): the structural unit (2) = 40 mol: 60 mol. Moreover, Mw = 126,000.

(Resin Synthesis Example 2)
Resin raw materials and solvents such as DSDFBP 40.1 g (0.095 mol), DFBP 62.2 g (0.284 mol), TMBPF 97.4 g (0.380 mol) and potassium carbonate 65.7 g (0.475 mol), and DMSO 798.4 g and 156.5 g (yield 85%) (resin 2) of polymer powder was obtained in the same manner as in Resin Synthesis Example 1 except that the amount of toluene was 266.2 g. Here, the structural unit (1): the structural unit (2) = 25 mol: 75 mol. Moreover, Mw = 123,000.

[Manufacturing Example 1]
The resin 1 produced in Resin Synthesis Example 1 and the resin 2 produced in Resin Synthesis Example 2 were each dissolved in DMF to prepare varnishes having a resin concentration of 5% by mass. Each varnish was weighed in a beaker so that the mass ratio of resin 1 and resin 2 (resin 1: resin 2) was 3: 7, mixed with a magnetic stirrer, and then cast on a release sheet. After the sheet is dried at 150 ° C. for 10 minutes, the film formed on the sheet is peeled off, and the semipermeable membrane 1 which is a self-standing film having a mass ratio of resin 1 and resin 2 of 3: 7 and a thickness of 0.6 μm. Got

In the following examples, all varnishes were prepared with a resin concentration of 5% by mass.

[Manufacturing Example 2]
A resin film was obtained in the same manner as in Production Example 1 except that the resin 1 and the resin 2 were mixed at a mass ratio (resin 1: resin 2) of 7: 3, and this was peeled off from the release sheet. A semipermeable membrane 2 having a thickness of 0.6 μm was obtained as a free-standing membrane.

[Manufacturing Example 3]
The resin 1 produced in Resin Synthesis Example 1 was dissolved in DMF to prepare a varnish, and the resin 2 produced in Resin Synthesis Example 2 was dissolved in DMF to prepare a varnish. The varnish of resin 1 is cast on a release sheet and dried at 150 ° C. for 10 minutes to form a film having a thickness of 0.4 μm, and then the varnish of resin 2 is further cast on it and dried at 150 ° C. for 10 minutes. After drying, a laminated film having a total thickness of 0.6 μm was obtained. This was peeled off from the release sheet to form a self-supporting membrane, and a semipermeable membrane 12 was obtained. In the evaluation described later, the laminated film was arranged so that the resin 2 film (0.2 μm) faces the DS side and the resin 1 film (0.4 μm) faces the FS side.

[Manufacturing Example 4]
The resin 1 produced in Resin Synthesis Example 1 was dissolved in DMF to prepare a varnish, and this varnish was cast on a release sheet and dried at 150 ° C. for 10 minutes to obtain a film of the resin 1. This was peeled off from the release sheet to form a self-supporting membrane, and a semipermeable membrane c1 having a thickness of 0.6 μm was obtained.

[Manufacturing Example 5]
The resin 2 produced in Resin Synthesis Example 2 was dissolved in DMF to prepare a varnish, and this varnish was cast on a release sheet and dried at 150 ° C. for 10 minutes to obtain a film of the resin 2. This was peeled off from the release sheet to form a self-supporting membrane, and a semipermeable membrane c2 having a thickness of 0.6 μm was obtained.

[Production example of forward osmosis membrane (Example and reference example)]
Next, a non-woven fabric (thin ^{) having an air permeability of 300 cm 3} / cm ² / s, a thickness of 290 μm, a grain size of 25 g / m ² , and a material of polypropylene measured by the A method (Frazier method) described in JIS L 1096. Two TEX (registered trademark) PS-105 manufactured by Mitsui Chemicals, Inc. are prepared, the semipermeable membrane obtained in each production example is sandwiched between these non-woven fabrics, and these are integrated to obtain a forward osmosis membrane. rice field. The following evaluation was performed using the obtained forward osmosis membrane.

FIG. 1 shows a schematic view of the apparatus 10 used for evaluating the separation performance of the forward osmosis membrane.

The device 10 includes a feed solution tank 1, a flow path 2, a pump 3, a draw solution tank 11, a flow path 12, a pump 13, and an evaluation cell 21. The feed solution tank 1 is installed on the balance 4, and the draw solution tank 11 includes an electric conductivity meter 15. At the start of the evaluation, 500 g of Milli-Q water having an electrical conductivity of 50 μS / cm or less is stored in the feed solution tank 1 as the feed solution FS (Feed Solution), and the draw solution DS is stored in the draw solution tank 11. As (Draw Solution), 800 g of 0.2, 0.4, 0.6 or 0.8 mol / L NaCl aqueous solution is stored. The feed solution in the feed solution tank 1 flows through the flow path 2 at a rate of 0.6 L / min by using the pump 3, and the draw solution in the draw solution tank 11 is 0.6 L / min by using the pump 13. It flows through the flow path 12 at a speed. The pressing force from the FS to the DS is about 0 kPa or about 1 kPa. The feed solution flowing through the flow path 2 and the draw solution flowing through the flow path 12 are in contact with each other inside the evaluation cell 21 via the forward osmosis film 22 having an ^{effective film area of 0.0042 m 2, and the forward osmosis film 22 is formed.} The water in the feed solution permeates through the draw solution, and a part of the salt (NaCl) in the draw solution diffuses into the feed solution.

Water permeation flux (Jw)
The weight loss of the feed solution was measured every minute with the balance 4, and the weight loss per unit area of the forward osmosis membrane was defined as the water permeation flux Jw (L / (m ² · h)) for a unit time. The average value for 30 to 60 minutes after the start of circulation is shown in each table.

Salt back diffusion amount (Js)
The change in the electric conductivity of the draw solution was measured every minute with the electric conductivity meter 15, and this was converted into the change in the molar concentration of the draw solution. From this, the amount of reverse diffusion Js (g / (m ² · h)) of salt per unit area of the forward osmosis membrane was calculated for a unit time. Each table shows Js / Jw calculated from the average value of Js and Jw for 30 to 60 minutes after the start of circulation.

表１の結果から、半透膜１および２では、半透膜ｃ１およびｃ２よりも、Ｊｓ／Ｊｗが小さく、したがって水透過流束および塩阻止率のバランスに優れていた。

From the results in Table 1, the semipermeable membranes 1 and 2 had smaller Js / Jw than the semipermeable membranes c1 and c2, and therefore had an excellent balance between the water permeation flux and the salt inhibition rate.

表２の結果から、半透膜１２では、半透膜ｃ１と同程度の水透過流束Ｊｗを維持しつつ、半透膜ｃ１と比べて塩逆拡散量Ｊｓが小さく、よってＪｓ／Ｊｗが小さかった。

From the results in Table 2, the semipermeable membrane 12 maintains the same level of water permeation flux Jw as the semipermeable membrane c1, while the amount of salt reverse diffusion Js is smaller than that of the semipermeable membrane c1, so Js / Jw is higher. It was small.

Further, although there is a difference in the tendency depending on the membrane, it can be seen that under the condition of pressurizing from FS to DS, the value of back diffusion of the salt is equal to or less than that under the condition of no pressurization. It is considered that this is because the water permeated from the feed liquid by pressurization showed the effect of reducing the back diffusion of the salt. Alternatively, it is considered that the (A1) / (A2) layer may have been slightly changed to a suitable structure.

1 Feed solution tank 2, 12 Flow path 3, 13 Pump 4, 14 Balance 10 Evaluation device 11 Draw solution tank 15 Electrical conductivity meter 21 Evaluation cell 22 Forward osmosis membrane DS Draw solution FS Feed solution

Claims (15)

Semipermeable membrane and
A forward osmotic membrane comprising a porous substrate disposed on at least one surface thereof.
The semitransparent film contains an aromatic polyether resin (A) having a protonic acid group-containing structural unit, and the resin (A) is a protonic acid group-containing aromatic polyether resin (A1) and the resin. A positive osmotic film containing at least a protonic acid group-containing aromatic polyether resin (A2) having a larger molar fraction of the protonic acid group-containing structural unit than (A1). The forward osmosis membrane according to claim 1, wherein the semipermeable membrane is formed of a mixture containing at least the resins (A1) and (A2). The forward osmosis membrane according to claim 2, wherein the semipermeable membrane has a structure separated into at least two phases corresponding to the resins (A1) and (A2), respectively. The forward osmotic membrane according to claim 1, wherein the concentration of the protonic acid group derived from the resin (A) in the semipermeable membrane has a gradient in the thickness direction of the semipermeable membrane. The forward osmosis membrane according to claim 4, wherein the semipermeable membrane has a layer (L1) containing the resin (A1) and a layer (L2) containing the resin (A2). The resins (A1) and (A2) have a structural unit (1) represented by the following formula (1) and a structural unit (2) represented by the following formula (2), respectively, and the resin (A2). ) Is any one of claims 1 to 5, wherein the molar fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is larger than that of the resin (A1). The forward osmosis membrane described in.

[In equations (1) and (2)
R ^{1 to} R ¹⁰ are independently H, Cl, F, CF ₃ or C _m H _{2m + 1} (m indicates an integer of 1 to 10).
At least one of ^{R 1 to} R ¹⁰ _{is C m} H _{2m + 1} (m indicates an integer of 1 to 10).
Two or more R ^{1 to} R ¹⁰ may be present in each aromatic ring, and when two or more C _m H _{2 m + 1} are present in one _{aromatic ring, each C m} H _{2 m + 1} is present with each other. It may be the same or different.
X ^{1 to} X ⁵ are independently H, Cl, F, CF ₃ or protonic acid groups, respectively.
At ^{least one of X 1 to} X ⁵ is a protonic acid group and
Two or more of X ^{1 to} X ⁵ may be present in each aromatic ring, and when two or more proton acid groups are present in one aromatic ring, the proton acid groups are different even if they are the same as each other. May be.
A ^{1 to} A ⁶ are independently directly bonded, −CH ₂ −, −C (CH ₃ ) ₂₋ , −C (CF ₃ ) ₂₋ , −O− or −CO−, respectively.
i, j, k and l independently represent 0 or 1, respectively. ] According to claim 6, the molar fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) in the entire resin (A) is 0.1 to 0.9. The described positive osmosis membrane. In the resins (A1) and (A2), the absolute value of the difference in the mole fraction of the structural unit (1) with respect to the total amount of the structural unit (1) and the structural unit (2) is 0.03. The forward osmotic membrane according to claim 6 or 7, which is ~ 0.6. The forward osmosis membrane according to any one of claims 1 to 8, wherein the aromatic polyether resin (A) has a weight average molecular weight of 70,000 or more. The forward osmosis membrane according to any one of claims 1 to 9, wherein the semipermeable membrane has a thickness of 3.0 μm or less. The forward osmosis membrane according to any one of claims 1 to 10, further comprising the semipermeable membrane and the porous substrate arranged on both sides thereof. ^{Claims 1 to 11 in which the porous substrate has an air permeability of 100 to 400 cm 3} / cm ² / s and a thickness of 50 to 700 μm measured by the method A (Frazier method) described in JIS L 1096. The forward osmotic membrane according to any one of the above. A forward osmosis membrane element comprising the forward osmosis membrane and spacer according to any one of claims 1-12. A forward osmosis membrane module in which the forward osmosis membrane element according to claim 13 is housed in a container. A feed solution is flowed on one surface of the forward osmosis membrane module according to claim 14 and the forward osmosis membrane included in the forward osmosis membrane module, and a draw solution having a solute concentration higher than that of the feed solution is flowed on the other surface. A system having a drive pump for the purpose of allowing water contained in the feed solution to be transferred to the draw solution through the forward osmosis membrane.

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