Draw Solute and Water Treatment Equipment

Abstract

The invention provides a draw solute for a forward osmosis membrane method, the draw solute comprising a compound containing a structural site derived from an amine compound and a polyoxyalkylene structural site in which two or more oxyalkylene groups are randomly bonded.

Description

[Technical field]

[0001] The present disclosure relates to draw solutes and water treatment devices. [Background technology]

[0002] Various techniques for desalinating salts contained in seawater, brine, etc. have been known, including a separation technique using forward osmosis that uses an osmotic pressure inducer (draw solute). When performing water treatment using forward osmosis, it is necessary to move a solvent (water) through a semipermeable membrane to a solution (draw solution) that has a higher osmotic pressure than the solution to be treated, and then recover the solvent from the draw solution.

[0003] Patent Document 1 proposes, as a draw solute, a block copolymer having a glycerin skeleton as a basic skeleton and including an ethylene oxide group as a hydrophilic portion and a group consisting of propylene oxide and / or butylene oxide as a hydrophobic portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6172385 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, it is known that block copolymers having ethylene oxide groups and propylene oxide and / or butylene oxide are used as draw solutes for forward osmosis in desalination using the forward osmosis membrane process. However, there has been room for improvement in terms of easily transferring the solvent (water) from the solution to be treated to the draw solution. Therefore, an object of the present disclosure is to provide a draw solute for a forward osmosis membrane process that can produce a draw solution that exhibits high osmotic pressure and has excellent phase separation properties. [Means for solving the problem]

[0006] The present inventors have conducted various studies to achieve the above object and have come up with the present disclosure. That is, the present disclosure relates to a draw solute for a forward osmosis membrane process, which contains a compound having a structural portion derived from an amine compound and a polyoxyalkylene structural portion in which two or more types of oxyalkylene groups are randomly bonded. Effect of the Invention

[0007] The draw solute of the present disclosure exhibits high osmotic pressure and good phase separation properties, and can therefore be preferably used as a draw solute in, for example, a forward osmosis (FO) system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present disclosure will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present disclosure described below is also a preferred embodiment of the present disclosure.

[0009] [Draw solutes of the present disclosure] The draw solute for forward osmosis membrane process of the present disclosure (sometimes referred to as draw solute) includes a compound (hereinafter also referred to as "compound of the present disclosure") that includes a structural portion derived from an amine compound and a polyoxyalkylene structural portion in which two or more types of oxyalkylene groups are randomly bonded.

[0010] In the present disclosure, the term "structural moiety derived from an amine compound" refers to a structural moiety obtained by removing at least one hydrogen atom from at least one amino group contained in an amine compound.

[0011] In the present disclosure, the oxyalkylene group is not particularly limited, but may be any group having the general formula -CHCH(-R 0 )-O-, or -CH(-R 0 )CH2-O-. 0 is preferably selected from a hydrogen atom, an alkyl group which may have a substituent, and an aryl group which may have a substituent.

[0012] The oxyalkylene group is preferably a group having 2 to 20 carbon atoms, more preferably a group having 2 to 15 carbon atoms, and even more preferably a group having 2 to 10 carbon atoms. 0 is preferably a group having 0 or more and 18 or less carbon atoms, more preferably a group having 0 or more and 13 or less carbon atoms, and even more preferably a group having 0 or more and 8 or less carbon atoms. Examples of the oxyalkylene group include an oxyethylene group (-CH2CH2-O-), an oxypropylene group (-CH2CH(-CH3)-O-, or -CH(-CH3)CH2-O-), and an oxybutylene group (for example, -CH2CH(-C2H5)-O-, -CH(-C2H5)CH2-O-, or -CH(CH3)-CH(CH3)-O-).

[0013] The amine compound (sometimes called amine) is not particularly limited as long as it is a compound having one or more amino groups. However, in this disclosure, ammonia is included in the compounds having amino groups. For example, in the case of triethanolamine, N(CH2CH2OH)3, N is a structural part derived from the amine compound, and the three CH2CH2O- are treated as oxyalkylene groups.

[0014] Examples of the amine compound include aliphatic amines, aromatic amines, and heterocyclic amines. Examples of the aliphatic amines include aliphatic primary amines such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-pentylamine, 3-pentylamine, neopentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, pentadecylamine, cetylamine, laurylamine, stearylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, and 1-adamantanamine; dimethylamine, ethylmethylamine, diethylamine, methylpropylamine, methylisopropylamine, ethylpropylamine, ethylisopropylamine, butylmethylamine, and methylt aliphatic secondary amines such as N-butylamine, dipropylamine, diisopropylamine, ethyl t-butylamine, N-ethyl-1,2-dimethylpropylamine, dibutylamine, diisobutylamine, di(t-butyl)amine, ethylhexylamine, dipentylamine, dihexylamine, di(2-ethylhexyl)amine, dioctylamine, didecylamine, dilaurylamine, dicetylamine, distearylamine, methylstearylamine, ethylstearylamine, butylstearylamine, methylcyclohexylamine, ethylcyclohexylamine, Nt-butylcyclohexylamine, dicyclohexylamine, and di(2-methylcyclohexyl)amine; and the like.

[0015] Other aliphatic amines include aliphatic polyamines, alkanolamines such as monoethanolamine, diethanolamine, dipropanolamine, etc. Among these, it is preferable to use aliphatic polyamines as the amine compound.

[0016] Examples of the aliphatic polyamine include aliphatic compounds having two or more amino groups. Examples of the aliphatic polyamine include N,N'-dimethyl-1,3-propanediamine, 1,3-pentanediamine, ethylenediamine, diethylenetriamine, triethylenetetramine (N,N'-di(2-aminoethyl)ethylenediamine), etc. Among these, it is preferable to use diethylenetriamine as the amine compound.

[0017] The aliphatic polyamine preferably has 2-20 amino groups, more preferably 2-10 amino groups, and further preferably 2-5 amino groups.

[0018] The molecular weight of the aliphatic polyamine is preferably 50-5,000, more preferably 75-3,000, and even more preferably 100-2,000.

[0019] The amine value of the aliphatic polyamine is not particularly limited, but can be, for example, 5 to 40 (mmol / g solid).

[0020] Examples of aromatic amines include aromatic primary amines such as benzylamine, phenylpropylamine, phenylbutylamine, 1,1-dimethyl-2-phenylethylamine, 3,4-dimethylbenzylamine, aniline, methylaniline, ethylaniline, propylaniline, isopropylaniline, butylaniline, laurylaniline, stearylaniline, dimethylaniline, diethylaniline, methylbenzylamine, 4,4'-methylenedianiline, naphthylamine, trimethylaniline, and 4-methylphenethylamine; and aromatic secondary amines such as methylbenzylamine, ethylbenzylamine, t-butylbenzylamine, diphenylamine, and dibenzylamine.

[0021] Other aromatic amines include aromatic polyamines such as N-benzyl-1,3-propanediamine, 2,4,6-trimethyl-1,3-phenylenediamine, and 4-aminobenzylamine.

[0022] Examples of heterocyclic amines include aziridine, azetidine, pyrrolidine, 2-methylpyrrolidine, piperidine, 2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine, 2,4-dimethylpiperidine, 3,5-dimethylpiperidine, 2,6-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-isobutylpiperazine, and N-cyclohexylpiperidine. Silpiperazine, N-cyclopentylpiperazine, N-phenylpiperazine, 1-(2-pyridyl)piperazine, 1-(4-pyridyl)piperazine, 1-(2-pyrimidyl)piperazine, morpholine, pyrrole, 2-methylpyrrole, 2,4-dimethylpyrrole, 3,4-dimethylpyrrole, pyrazole, 3,5-dimethylpyrazole, imidazole, 3-methylindole, 2-phenylindole; and the like.

[0023] The amine compound preferably has 1-100, more preferably 1-70, and further preferably 1-50 amino groups.

[0024] The amine compound may be used alone or in combination of two or more kinds.

[0025] In the compounds of the present disclosure, the polyoxyalkylene structural portion contains two or more types of oxyalkylene groups.

[0026] In the present disclosure, the fact that two or more kinds of oxyalkylene groups are randomly bonded may be interpreted in the usual sense. For example, in the polyoxyalkylene structure portion, the first oxyalkylene group OA 1 and a second oxyalkylene group OA 2 may be bonded in an irregular order.

[0027] The first oxyalkylene group OA contained in the polyoxyalkylene structure portion of the compound of the present disclosure 1 and a second oxyalkylene group OA 2The molar ratio of the first oxyalkylene group OA contained in the polyoxyalkylene structure portion is preferably 1:1 or more and 1:30 or less, more preferably 1:1 or more and 1:20 or less, and even more preferably 1:1 or more and 1:10 or less. 1 and a second oxyalkylene group OA 2 When the molar ratio is within the above range, the osmotic pressure and phase separation properties exhibited by the draw solute of the present disclosure tend to be good.

[0028] The first oxyalkylene group OA contained in the polyoxyalkylene structure portion of the compound of the present disclosure 1 and a second oxyalkylene group OA 2 is preferably an oxyethylene group (-CH2CH2-O-), an oxypropylene group (-CH2CH(-CH3)-O-, or -CH(-CH3)CH2-O-) or an oxybutylene group (e.g., -CH2CH(-C2H5)-O-, -CH(-C2H5)CH2-O-, or -CH(CH3)-CH(CH3)-O-).

[0029] In the compound of the present disclosure, the number of moles of oxyalkylene groups per mole of the structural portion derived from the amine compound is preferably 5 moles or more. More preferably, it is 10 moles or more, and even more preferably, it is 20 moles or more. On the other hand, the number of moles of oxyalkylene groups per mole of the structural portion derived from the amine compound is preferably 100 moles or less, more preferably 80 moles or less, and even more preferably 70 moles or less. When the number of moles of oxyalkylene groups per mole of the structural portion derived from the amine compound is within the above range, the osmotic pressure and phase separation property exhibited by the draw solute of the present disclosure tend to be good.

[0030] The compound of the present disclosure may include a structural portion derived from an amine compound and a structural portion other than a polyoxyalkylene structural portion. In the compound of the present disclosure, the structural portion derived from an amine compound and the polyoxyalkylene structural portion may be directly bonded, or a bonding group may be inserted between them. In the compound of the present disclosure, the polyoxyalkylene structural portion is usually bonded to the structural portion derived from an amine compound at at least one end directly or via a bonding group, but may be bonded to another group at the other end. Examples of the other group include a hydrogen atom and an organic group having 1 to 30 carbon atoms.

[0031] Regarding the molecular weight of the compound of the present disclosure, from the viewpoint of suppressing leakage of the compound from the membrane, the number average molecular weight is preferably 500 to 10000, more preferably 1250 to 7000, and even more preferably 1500 to 5000. The weight average molecular weight is preferably 500 to 10000, more preferably 1250 to 7000, and even more preferably 1500 to 5000. The number average molecular weight and weight average molecular weight can be measured by gel permeation chromatography (GPC). When the number average molecular weight and weight average molecular weight of the compound of the present disclosure are within the above ranges, the osmotic pressure and phase separation property exhibited by the draw solute of the present disclosure tend to be good. The compounds of the present disclosure preferably have a cloud point (lower critical solution temperature). The cloud point refers to the temperature at which a transparent or translucent liquid undergoes phase separation upon temperature change, resulting in the liquid becoming opaque.

[0032] By heating a liquid containing the compound of the present disclosure, phase separation can be caused into a liquid mainly composed of the compound of the present disclosure and a liquid mainly composed of the solvent (water).

[0033] The cloud point of the compound of the present disclosure can be appropriately adjusted by changing the constitution of the compound of the present disclosure, for example, the amine structure, the type and number of moles of oxyalkylene group added, etc. The cloud point of the compound of the present disclosure is preferably 80° C. or lower. The cloud point of the compound of the present disclosure is more preferably 20 to 80° C., and further preferably 30 to 80° C.

[0034] The compound of the present disclosure contained in the draw solute of the present disclosure may be one type alone or two or more types.

[0035] In the compounds of the present disclosure, the polyoxyalkylene structural portion is not particularly limited, but may be formed by an alkylene oxide. In the present disclosure, examples of alkylene oxides include, but are not limited to, ethylene oxide (EO), propylene oxide (PO), 1,2-butylene oxide (1,2-BO), 2,3-butylene oxide (2,3-BO), styrene oxide, epichlorohydrin, tetrahydrofuran, oxetane, dioxirane, trioxane, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether. The compound of the present disclosure can be obtained by random addition polymerization of alkylene oxide to amine compound. The number of moles of alkylene oxide per mole of amine compound is preferably 5 moles or more, more preferably 10 moles or more, and even more preferably 20 moles or more. On the other hand, the number of moles of alkylene oxide per mole of amine compound is preferably 100 moles or less, more preferably 80 moles or less, and even more preferably 70 moles or less.

[0036] The reaction conditions for random addition polymerization (alkoxylation) of alkylene oxide are not particularly limited. For example, an amine compound and an alkylene oxide can be reacted as they are or diluted with a solvent as necessary at preferably 0 to 200°C, more preferably 120 to 180°C. In this case, an alkali catalyst such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) may be used as a catalyst. The reaction can be carried out, for example, by adding a catalyst to an amine compound and then feeding an alkylene oxide into the reaction system. When two or more alkylene oxides are randomly added, they may be mixed and then fed, or may be fed separately. When two or more alkylene oxides are fed separately, they may be fed simultaneously or sequentially. After feeding the alkylene oxide, the reaction rate can be further increased by aging for 1 to 2 hours until the reaction is sufficiently carried out.

[0037] After the random addition polymerization reaction of alkylene oxide, an acid such as acetic acid, lactic acid, or phosphoric acid is added to neutralize the product. Furthermore, it is preferable to carry out a step of removing impurities. The method of removal is not particularly limited, but examples thereof include centrifugation, filtration, evaporation, and distillation. It is preferable to remove light impurities such as 2,3-butadione contained in the compound by heating the mixture under reduced pressure at 120 to 200°C, more preferably at 140 to 180°C.

[0038] [Drawing solution of the present disclosure] The draw solution of the present disclosure contains the above-mentioned draw solute. The content of the draw solute is preferably 20 to 100% by mass, more preferably 50 to 100% by mass, and further preferably 75 to 100% by mass, based on the total amount of the draw solution. The draw solution may contain a solvent. The solvent may be appropriately selected depending on the conditions of the forward osmosis membrane method using the draw solution, and one or more solvents selected from water, methanol, ethanol, etc. may be used. It is more preferable that the solvent contains the same solvent as the solution to be treated (sometimes called the feed solution). The content of the solvent may be, for example, 80 to 0 mass % with respect to the total amount of the draw solution.

[0039] The draw solution may contain draw solutes other than the draw solutes, but the content of the draw solutes is preferably 20 mass% or less based on the total amount of the draw solutes. The draw solution is preferably composed of the draw solutes, any solvent, and any other draw solutes, and more preferably composed of the draw solutes and any solvent.

[0040] The draw solution preferably has a cloud point (lower critical solution temperature). The cloud point refers to the temperature at which a transparent or translucent liquid undergoes phase separation by changing its temperature, resulting in an opaque liquid. A draw solution having a cloud point can undergo phase separation between the draw solute and the solvent by heating.

[0041] The cloud point of the draw solution can be appropriately adjusted by changing the constitution of the compound of the present disclosure, for example, the type of amine compound, the type of polyoxyalkylene structural portion, the number of moles of polyoxyalkylene groups, etc., and a draw solution with an appropriate cloud point can be selected according to the intended use.

[0042] For example, when applying the forward osmosis membrane method to water treatment using low-temperature waste heat from a factory, it is preferable that the draw solution does not undergo phase separation at a temperature around room temperature where the forward osmosis membrane treatment is performed, and that the draw solution undergoes phase separation at a temperature around the low-temperature waste heat temperature from the factory. The suitable cloud point of the draw solution used in such applications varies depending on the concentration of the draw solute in the draw solution, but for example, when the draw solute is made into a 50 mass% aqueous solution, the cloud point is preferably 20 to 80°C, more preferably 30 to 80°C.

[0043] [Water treatment method of the present disclosure] In the forward osmosis membrane process, the feed solution and the draw solution are brought into contact with each other through a semipermeable membrane, and the solvent moves from the feed solution side, which has a low osmotic pressure, to the draw solution, which has a high osmotic pressure. As the solvent moves, the concentration of the draw solution gradually decreases. Therefore, in order to continue the forward osmosis membrane process, it is necessary to separate the draw solute and the solvent contained in the draw solution. With the draw solution having a cloud point, the draw solute and the solvent can be phase-separated by heating.

[0044] In the forward osmosis membrane process using a draw solution having such a cloud point, for example, the forward osmosis membrane process can be continuously performed by repeating the following treatment. The feed solution is placed on one side of the semipermeable membrane and the draw solution on the other side so that they are in contact with the semipermeable membrane, and the solvent is transferred from the feed solution side through the semipermeable membrane to the draw solution side. The reduced concentration draw solution is removed and heated to cause phase separation between the draw solute and the solvent. The phase-separated draw solute is circulated again to the other side. The phase-separated solvent is further purified, for example, using a nanofiltration membrane (NF membrane), to obtain the desired processed product (purified water, etc.).

[0045] The temperature at which the forward osmosis membrane method is carried out is not particularly limited, but is usually around room temperature, for example, 5 to 40°C.

[0046] As the semipermeable membrane used in the forward osmosis membrane method, a conventionally known one can be used, but in order to maintain the strength of the membrane, it is preferable to use a combination of a dense active layer, which determines the selective permeability of the membrane, and a porous support layer. Since the support layer is more likely to adsorb dirt than the active layer, it is generally preferable to provide the active layer of the semipermeable membrane on the feed liquid side from the viewpoint of reducing membrane dirt.

[0047] The draw solution can be applied to various applications that utilize the forward osmosis membrane method. Among them, water treatment devices and power generation devices are applications where the forward osmosis membrane method is expected to be used, and the draw solution can be suitably applied to these applications. EXAMPLES

[0048] The present disclosure will be described in more detail below by showing examples, but the scope of the present disclosure is not limited to these examples, and all modifications and implementations that do not deviate from the gist of the present disclosure are included in the technical scope of the present disclosure. In addition, unless otherwise specified, "%" means "% by mass". [Synthesis of Compounds] The compounds of Example 1 and Comparative Examples 1 to 3 were synthesized as shown below. For each compound, the core molecule before addition polymerization, the sequence structure, the molar ratio of alkylene oxide added to the core molecule, and the designed molecular weight are all shown in Table 1. The designed molecular weight was calculated as the sum of the molecular weight of the core molecule and the value obtained by multiplying the molecular weight of the alkylene oxide by the molar ratio of alkylene oxide added to 1 mole of the core molecule.

[0049] <Production Example 1> In a 1L autoclave, 150.0g of diethylenetriamine and 8.75g of 48% KOH aqueous solution were charged at room temperature, and the gas phase was replaced with nitrogen gas. The pressure was reduced to -0.1MPa while bubbling nitrogen gas at 20mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20MPa, the bubbling was stopped and 320.2g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours.

[0050] 210.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to set the gauge pressure to 0.20 MPa. 283.5 g of ethylene oxide and 232.0 g of butylene oxide were injected over a period of 2 hours while stirring, and the mixture was aged for 3 hours.

[0051] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to set the gauge pressure to 0.20 MPa. 175.8 g of ethylene oxide and 95.9 g of butylene oxide were injected over 4 hours while stirring, and aged for 3 hours. After that, the temperature was lowered to 60°C, the pressure was released, and 1.23 g of 50% lactic acid was added. Nitrogen gas was bubbled at 20 mL / min while the gauge pressure was reduced to -0.1 MPa, and stirring was performed at 125°C for 3 hours. This resulted in the compound (1) of Example 1.

[0052] <Production Example 2> 150.0g of diethylenetriamine and 8.75g of 48% KOH aqueous solution were charged into a 1L autoclave at room temperature, and the gas phase was replaced with nitrogen gas. The nitrogen gas was bubbled at 20mL / min while the pressure was reduced to -0.1MPa. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20MPa, the bubbling was stopped, and 320.2g of ethylene oxide was injected over 4 hours, and then aged for 3 hours. 150.0g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas, and the gauge pressure was set to 0.20MPa. 506.2g of ethylene oxide was injected over 4 hours while stirring, and aged for 1 hour.

[0053] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to adjust the gauge pressure to 0.20 MPa. 69.4 g of ethylene oxide was injected over a period of 2 hours while stirring, and the mixture was aged for 1 hour.

[0054] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to set the gauge pressure to 0.20 MPa. 77.7 g of butylene oxide was injected over 1 hour while stirring, and aged for 3 hours. After that, the temperature was lowered to 60°C, the pressure was released, and 0.67 g of 50% lactic acid was added. Nitrogen gas was bubbled at 20 mL / min while the gauge pressure was reduced to -0.1 MPa, and stirring was performed at 125°C for 3 hours. This resulted in the compound (2) of Comparative Example 1.

[0055] <Production Example 3> In a 1L autoclave, 150.0g of diethylenetriamine and 8.75g of 48% KOH aqueous solution were charged at room temperature, and the gas phase was replaced with nitrogen gas. The pressure was reduced to -0.1MPa while bubbling nitrogen gas at 20mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20MPa, the bubbling was stopped and 320.2g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours.

[0056] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to adjust the gauge pressure to 0.20 MPa. 202.5 g of ethylene oxide was injected into the autoclave over a period of 2 hours while stirring, and the mixture was aged for 1 hour.

[0057] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to set the gauge pressure to 0.20 MPa. 70.5 g of butylene oxide was injected over 1 hour while stirring, and aged for 3 hours. After that, the temperature was lowered to 60°C, the pressure was released, and 1.07 g of 50% lactic acid was added. Nitrogen gas was bubbled at 20 mL / min while the gauge pressure was reduced to -0.1 MPa, and stirring was performed at 125°C for 3 hours. This resulted in the compound (3) of Comparative Example 2.

[0058] <Production Example 4> After 150.0 g of glycerin and 8.40 g of 50% KOH aqueous solution were charged into an autoclave at room temperature, the gas phase was replaced with nitrogen gas, and the pressure was reduced to -0.1 MPa while bubbling nitrogen gas at 20 mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20 MPa, the bubbling was stopped, and 440.0 g of ethylene oxide and 160.0 g of butylene oxide were injected over 2 hours, followed by aging for 3 hours.

[0059] 150.0 g of the intermediate thus obtained was charged into an autoclave at room temperature, and the gas phase was replaced with nitrogen gas to set the gauge pressure to 0.20 MPa. 497.6 g of ethylene oxide and 181.0 g of butylene oxide were injected over 2 hours while stirring, and aged for 3 hours. After lowering the temperature to 60°C, the pressure was released, and 1.16 g of 85% phosphoric acid was added. While bubbling nitrogen gas at 20 mL / min, the pressure was reduced to -0.1 MPa, and stirring was performed at 125°C for 3 hours. This resulted in the compound (4) of Comparative Example 3.

[0060] [Table 1]

[0061] [Compound evaluation] <Example 1, Comparative Examples 1 to 3> The compounds of Example 1 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Table 2. (Cloud Point Rating) An aqueous solution containing 50% by mass of each compound was prepared and sealed in a screw vial. This was left to stand in an oven at 97°C for 1 hour to separate into layers, and then cooled while measuring the internal temperature. The temperature at which a uniform layer was visually observed was taken as the cloud point. (Phase separation evaluation) An aqueous solution containing 50% by mass of each compound was prepared and sealed in a screw vial. This was left overnight in a 70 or 85°C oven to fully equilibrate, and then approximately 1g of the upper phase and approximately 1g of the lower phase were taken in three samples and placed in aluminum cups. The aluminum cups were left in a 97°C oven for 2 hours to dry, and the compound concentrations in the upper and lower phases were calculated from the weight difference before and after drying. (Effective osmotic pressure evaluation) An aqueous solution containing 50% by mass of each compound was prepared and sealed in a screw vial. This was left to stand overnight in an oven at 70 or 85°C to allow it to reach sufficient equilibrium, after which about 5 mL of the aqueous solution in the lower phase was taken in a dedicated sample cup and the water activity at 25°C was measured using a water activity measuring device (AquaLab Series4 TDL). Measurements were performed 3 to 5 times, and the average value was taken as the measured water activity value. The osmotic pressure (bar) was calculated from the measured water activity value using a formula and unit conversion. Osmotic pressure (bar) = ((1 - [measured water activity]) / 18.015) x 10 x 8.31 x (273.15 + [measurement temperature]))

[0062] [Table 2]

[0063] The results in Table 2 reveal that the draw solute of the present disclosure has the function of producing a draw solution having high osmotic pressure and good phase separation properties.

Claims

1. The compound includes a structural portion derived from an aliphatic polyamine and a polyoxyalkylene structural portion in which an oxybutylene group and an oxyethylene group are randomly bonded, the molar ratio of oxybutylene groups to oxyethylene groups contained in the polyoxyalkylene structural portion is 1:1 or more and 1:30 or less; The compound has a number average molecular weight of 500 to 10,000.

2. The draw solute for forward osmosis membrane process according to claim 1, wherein the cloud point of a 50% by mass aqueous solution of the compound is 80° C. or lower.

3. 3. The draw solute for a forward osmosis membrane process according to claim 1, wherein the number of moles of the oxybutylene group and the oxyethylene group per mole of the structural portion derived from the aliphatic polyamine is 5 moles or more.

4. The draw solute for forward osmosis membrane process described in any one of claims 1 to 3, wherein the number of amino groups in the aliphatic polyamine is 2 to 10.

5. A draw solute for a forward osmosis membrane process described in any one of claims 1 to 4, wherein the number of moles of the oxybutylene group and the oxyethylene group per 1 mole of the structural portion derived from the aliphatic polyamine is 70 moles or less.

6. The method for producing the draw solute for forward osmosis membrane process according to any one of claims 1 to 5, comprising a step of randomly adding and polymerizing butylene oxide and ethylene oxide to an aliphatic polyamine to obtain a compound containing a structural portion derived from the aliphatic polyamine and a polyoxyalkylene structural portion to which an oxybutylene group and an oxyethylene group are randomly bonded.

7. A draw solution comprising the draw solute for forward osmosis membrane processing according to any one of claims 1 to 5.

8. A method for treating water using the draw solution according to claim 7.

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