JPS5930442B2 - Permselective charged membrane and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel permselective charged membrane having excellent performance as an electrodialysis membrane, an electrolytic diaphragm, a reverse osmosis membrane, etc., especially as a reverse osmosis membrane, and a method for producing the same. .

More specifically, a polyhydantoin having a novel pendant sulfonic monoacid group obtained by introducing a certain range of sulfonic acid groups into the aromatic nucleus of a polyhydantoin containing an aromatic group in the main chain is a selection method that is substantially the same as a polyhydantoin having a novel pendant sulfonic monoacid group. This invention relates to a transparent charged membrane and its manufacturing method.

The range of applications for selectively permeable charged membranes is likely to expand in the future, centering on water treatment, and the emergence of membranes with excellent practicality is strongly desired.

In particular, for reverse osmosis applications that utilize Donnan exclusion, if conventional ion exchange membranes were used as they were, they would in principle have a high water permeability rate, but the membrane thickness would be large, resulting in uncharged It is not possible to obtain the same amount of water permeability as a type of asymmetric membrane, for example, a cellulose acetate membrane. 〉 Therefore, it is easy to predict that if a non-homogeneous membrane can be formed even in a charged membrane, the amount of water permeation will increase dramatically.
However, in order to create a heterogeneous membrane using phase separation,
It must have solubility in a solvent even after the ion exchange group has been introduced, and it must be able to be molded into a strong and flexible film. The main chain structure of the charged polymer used for this purpose must be rigid, chemically stable, and have good solubility in polar solvents. From this point of view,
The present inventors focused on polyhydantoin and attempted to introduce a certain range of sulfonic acid groups into the aromatic groups in its main chain. ,, Sulfonic acid groups can be easily introduced into polyhydantoin, which does not have a charged group, using an ordinary sulfonating agent, and it maintains good film-forming properties, even forming asymmetric films. The present invention was achieved by discovering that it is possible to make a selectively permeable membrane containing the above-mentioned materials.

The present inventor has already proposed that polyhydantoin be made into an asymmetric membrane and used as a reverse osmosis membrane (see Japanese Unexamined Patent Publication No. 49-33888).

Asymmetric polyhydantoin membranes that do not contain more than a certain amount of ionically dissociable groups either have a high rejection rate and excellent chemical stability, or are not sufficiently hydrophilic and therefore have a high water permeability depending on the application. It has been found that there are cases where a large value is required, but the membrane of the present invention has succeeded in solving this problem. In addition, as an example of introducing pendant sulfonic acid groups into a polymer mainly composed of aromatic groups or main chains and using it as a selectively permeable charged membrane, conventionally, sulfonic acid groups were introduced into polyp-phenylene oxide. Example {Nd. Eng. Chem. PrOd. Res. Dev
elOp. Vol. 1O, Taki 3335 (1971)} Examples of introducing sulfonic acid groups into polyarylene ether sulfones (see JP-A-48-852 and JP-A-48-853) are known.

In contrast to these known examples, the membrane of the present invention has a polyarylene hytantoin in the basic bone core that is more rigid and superior in film-forming properties than the above-mentioned polymers, so that the membrane obtained is similar to that of the above-mentioned polymers. It has been found that the introduction of a sulfonic acid group to a certain degree is mechanically superior and highly practical. This can be an extremely advantageous feature when used under severe conditions under high pressure, such as in reverse osmosis membrane applications. The present invention has been achieved based on such knowledge (
1) The following general formula 4 [wherein -Hy- is a formula (where Rl, R2, R3 and R4 are the same or different hydrogen atoms or alkyl groups having 1 to 4 carbon atoms, cyclohexyl groups, phenyl groups and tolyl groups. Represents a monovalent organic group selected from among.

Note that the above formula also includes the form in which the left and right sides are reversed).
represents at least one type of (2+p)-valent organic group having an average carbon number of 6 to 40, of which 40% or more are aromatic nuclear carbon atoms. Moreover, -SO3H is bonded to the aromatic nuclear carbon atom of R, and p represents the average value defined below. Average value of p = 1 to 0, where q indicates a range of 0.01 to 1.5.

] A selectively permeable charged membrane consisting essentially of a polyhydantoin having a pendant sulfonic acid group as a repeating unit represented by the formula (2) A pendant membrane consisting essentially of a repeating unit represented by the above formula (4). A method for producing a selectively permeable charged membrane, which comprises dissolving a polyhydantoin having a succinic acid group in an organic polar solvent or an organic polar solvent to which a solubility regulator is added if necessary, and solidifying the solution after casting. It is. In the present invention, -Hy- in the force χ is represented by the formula (where Rl, R2, R3 and R4 are the same or different hydrogen atoms or alkyl groups having 1 to 4 carbon atoms, cyclohexyl groups, phenyl groups and tolyl groups). represents a monovalent organic group selected from

However, the above formula is at least one type of the formula (including its left-right reversed form). R, , R2, R3, and R4 forming the above hydantoin ring may be the same or different hydrogen atoms or monovalent organic groups, including monovalent aliphatic groups, alicyclic groups, and aromatic groups. However, lower alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, and propyl group, and aromatic groups such as cyclohexyl group, phenyl group, and tolyl group are inexpensive raw materials, and are particularly preferred from an industrial standpoint. preferable. In the present invention, R in the general formula represents at least one type of (2+p)-valent organic group having an average carbon number of 6 to 40, of which 40% or more are aromatic nuclear carbon atoms. Examples of the organic groups constituting each R include aliphatic groups, alicyclic groups, aromatic groups, etc., but also include divalent groups in which these are bonded through acid amide and/or imide bonds. be done. However, the characteristics of the present invention are as described above, in addition to the excellent physical and chemical properties of polyhydantoin, a selectively permeable charged membrane in which a part of the aromatic group in the main chain is replaced with sulfonic acid. be. Therefore, in this sense, if too much R is applied to the hydantoin ring, its characteristics will be diminished, and if the amount of aromatic group Φ among the groups constituting R is small, the site for introducing sulfonic acid will be reduced. Otherwise, the effect of the pendant's sulfonic acid group will be weakened.

Therefore, the average value of the total carbon number of R in the present invention is 6 to 6.
40, and approximately 40% or more of the total number of carbon atoms constituting R must constitute an aromatic nucleus. When the average number of carbon atoms in R is less than 6, the content of aromatic nuclei is low;
If the amount exceeds %, the effect of the R group on the hydantoin ring becomes strong, and the excellent effects of the hydantoin ring, such as polarity and hydrophilicity, are impaired. Furthermore, if the aromatic nucleus of the total number of carbon atoms constituting R is less than 40%, it will naturally become difficult to introduce a sulfonic acid group, and the characteristics of the permselective charged membrane of the present invention will be impaired. In the present invention, examples of aliphatic groups suitably used as R include -f-CH2+2 to 20, and examples of aromatic groups include acid amides and/or imides with one bond, such as aralkyl groups such as What is suitably used as a heterogeneous bonding group such as a bond is carboxylic acid amide (-
Examples include tetracarboxylic acid diimide bonds such as CNH);jl.

The sulfonation rate p of the polyhydantoin having a pendant sulfonic acid group in the present invention is expressed in the form of q = 0.01 to 1.5, preferably 70.03 to 1.
．． Used between 0 and 0.

When Kq is 0.01 or less, no effect on the permselectivity of the pendant sulfonic acid groups is observed, and when q is 1.5 or more, the degree of swelling in water etc. is large, resulting in poor practicality as a membrane. is lost. As q increases, the water permeability increases, but the salt rejection performance decreases. Therefore, the membrane performance can be adjusted arbitrarily by adjusting the magnitude of q. The degree of polymerization of the sulfonated polyhydantoin used in the present invention can be expressed in terms of viscosity, but the polymer of the present invention exhibits typical polymer electrolyte behavior and the viscosity increases significantly in dilute solutions, resulting in so-called FuOss. According to the viscosity formula.

Therefore, the viscosity is preferably a value measured at a high concentration of about 0.59/dl (solvent) as a measure of molecular weight deficiency.

The viscosity of the sulfonated polyhydantoin tetrapolymer in the present invention is 0.2 to 5.0 d1/9, preferably 0.4 to 4.0 d1/9, expressed as a logarithmic viscosity measured at such a high concentration.
0d1/9, particularly preferably 0.5d1/f! The above is advantageous.

Furthermore, in the polymer used in the present invention, the sulfonated hydantoin units represented by the above formula are equivalent to all repeating units.
) 70% or more, preferably 80% or more.

The permselective charged membrane of the present invention is not limited to the method for producing polyhydantoin having pendant sulfonic acid groups, but generally (!) the force method (11) sulfonate method in which polyhydantoin is disulfonated with a sulfonating agent. Examples include a method of forming polyhydantoin using a monomer having an acid group.

Conventional methods are used to sulfonate polyhydantoin, for example, sulfonating agents such as chlorosulfonic acid and fuming sulfuric acid are used.

The permselective charged membrane of the present invention is prepared by using the above-mentioned sulfonated polyhydantoin in an organic polar solvent or as necessary.
It is obtained by dissolving it in an organic polar solvent to which a solubility regulator has been added, and solidifying it after casting.

Such an organic polar solvent may be one that can dissolve 0.5% or more of the polymer, such as N-methylpyrrolidone, N-methylcaprolactam, N,N-dimethylacetamide, hexamethylphosphoramide, and tetramethyl. So-called amide type such as urea? Medium; sulfoxide solvents such as dimethyl sulfoxide; carboxylic acid solvents such as formic acid, dichloroacetic acid, trifluoroacetic acid, etc.; among them, amide solvents and sulfoxide solvents are preferably used. When forming an asymmetric membrane, it is preferable to add a solubility regulator to the organic polar solvent for the purpose of promoting phase separation. Such solubility regulators include those that have appropriate miscibility with the polymer solvent and are capable of regulating the solubility of the polymer to promote phase separation when the sipolymer is solidified by a method such as drying. Preferably, swelling agents or non-solvents for polymers such as water, methanol, ethanol, formamide, dichloromethane and dichloroethane, inorganic salts such as lithium chloride, calcium chloride and lithium nitrate, or mixtures thereof can be used. The concentration of sulfonated polyhydantoin in the stock solution for membrane formation is preferably 0.5 to 50%, and preferably 10 to 50% in membrane formation of an asymmetric membrane.

Further, the amount of the solubility modifier varies depending on the type thereof and the concentration of the polymer in the film-forming stock solution, but it is generally preferably used in an amount of 10 to 200% by weight based on the amount of the polymer. Alternatively, when preparing the stock solution, other additives may be included for the purpose of adjusting the solution viscosity. As a casting substrate for obtaining a membrane from such a film-forming stock solution, a flat molding support such as glass or metal, or a porous support such as plastic, metal, woven fabric, or knitted fabric is used.

The shape of the support is usually preferably flat or tubular. The film thickness during casting is preferably 50 to 700μ, or preferably 200 to 700μ when an asymmetric film is intended. As a method for removing the solvent and solubility agent and solidifying the polymer, a conventionally known dry method, wet method, or a combination of the two may be used.

When forming an asymmetric membrane, for example, in hot process, only one side of the membrane is brought into contact with the coagulation liquid and coagulation proceeds from that side; in dry process, the membrane surface is similarly A method that combines a dry method and a wet method, in which the solvent is evaporated from only one side of the membrane, and the membrane is immersed in a coagulation solution with some solvent still remaining to extract and remove the remaining solvent, etc. can be given. The drying temperature for removing the solvent varies depending on the type of solvent, but generally -
A temperature of 30° C. to 250° C. is preferably used.

The coagulating liquid used in the wet method etc. is a non-solvent for the sulfonated polyhydantoin and is miscible with the solvent, solubility regulator and other additives, such as methanol, ethanol, water, inorganic An aqueous salt solution or a mixture thereof can be used.

The obtained permselective charged membrane can be subjected to heat treatment in a medium such as water or ethylene glycol, if necessary, to adjust the performance of the membrane.

As the treatment temperature, 50 to 150°C is preferably used. The charged membrane of sulfonated polyhydantoin obtained by the present invention is put to practical use in a modular type such as a spiral or tubular type, but a hollow fiber type permeable membrane is also included in the present invention. Such a charged membrane has excellent water permeability due to the introduced sulfonic acid groups, and since the polymer of the membrane base is mainly formed from rigid and straight chains, it exhibits excellent chemical and mechanical stability, so it can be used for a long period of time. Durable in use, with little drop in water permeability even under high pressure.

Furthermore, the membrane performance can be arbitrarily controlled by changing the amount of sulfonic acid groups introduced, so it can be said to be a selectively permeable charged membrane with extremely excellent practical performance. The charged membrane of the present invention has extremely high water permeability due to the introduced sulfonic acid groups, and can be used for desalination from water-inorganic salt fibers by reverse osmosis method using Donnan exclusion, such as brackish water, seawater, or sewage water. It is effectively used for desalination such as processing.

It is also effective in treating wastewater from various metal surface treatment industries such as plating and recovering valuable materials. Furthermore, it can be used for a wide range of applications such as separating and concentrating various components in pharmaceutical biochemistry and food factories. The present invention will be explained in more detail with reference to Examples below, but the Examples are for illustrative purposes only and are not intended to be limiting.

Note that the logarithmic viscosity in the examples is the value measured with a 0.5% N methylpyrrolidone solution at 3'C, and the ion exchange amount is ±N- after immersing the sulfonated polyhydantoin in NKOH.
This value was determined by back titration with HC2.

Sulfonated product of the hydantoin polymer shown in Example 1 (logarithmic viscosity 2.7 d1/9, ion exchange amount 2.23 meq/9
) was prepared as a 10% N-methylpyrrolidone solution and used as a film-forming stock solution.

This stock solution was cast onto a well-polished glass plate using a doctor blade with an opening of 120μ, heated at 130°C for 20 minutes, and then
The temperature was raised from 30°C to 21°C in 30 minutes, and then further raised to 210°C.
After drying at 2C for 10 minutes and cooling the glass plate to room temperature, the thin film was peeled off from the glass plate in water. The thickness of the obtained thin film was 9.5μ. A portion of the thin membrane (however, the membrane area was larger than that required for the reverse osmosis test described below) was placed in a pressurized container in the order of the thin membrane filter paper and the perforated plate.

The container was immersed in water and pressurized at a pressure of 1.5 k9/d through the nitrogen gas inlet that appeared on the water surface. After applying pressure for 5 minutes, it was confirmed that there were no pinholes in the thin film.

The thin film thus obtained was attached to a reverse osmosis test cell and a performance test was conducted.

The reverse osmosis experiment used an experimental cell with an effective membrane area of 11 cwL.
A thin film, a porous base material (Siliboa Filter Vj 04700 manufactured by Siliboa), and a sintered metal (pore diameter 3 μm) were installed in this cell in this order. The operating conditions were a 1.0% sodium chloride aqueous solution circulating system, and a pressure of 80k9/Cd.
The temperature was 25° C. and the feed water circulation rate was 1001/Hour. As a result, 312 hours after the start of operation, the amount of permeated water was 4.
．． 9×1 “4f! /CTL. sec, salt rejection rate 82.7
%showed that. Examples 2 to 5 Sulfonated polyhydantoin obtained from the same hydantoin polymer as shown in Example 1 and having various ion exchange amounts shown in Table 1 was formed into a film in the same manner as in Example 1, and then reversely A penetration experiment was conducted and the results shown in Table 1 were obtained.

[Comparative Sample 0] Polyhydantoin shown in Example 1 was formed into a film in the same manner, and a reverse osmosis test was conducted.

As a result, the amount of permeated water was 1.0X10-79/(V7F.S
It showed an eCl exclusion rate of 99.91%. The results clearly demonstrate the excellent high water permeability of the sulfonated polyhydantoins of Examples 1 to 5. Example 6 The sulfonated polyhydantoin used in Example 5 was dissolved in a mixed solvent of dimethylformamide and methylene chloride at a weight ratio of 80:20 at a concentration of 15% by weight to obtain a stock solution for membrane formation.

Claims (1)

[Claims] 1 The following general formula [A] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [A] [However, in the formula -
Hy- is a formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc.
represents a monovalent organic group selected from an alkyl group, a cyclohexyl group, a phenyl group, and a tolyl group. Note that the above formula also includes the form in which the left and right sides are reversed).
represents at least one type of (2+p)-valent organic group having an average carbon number of 6 to 40, of which 40% or more are aromatic nuclear carbon atoms. Moreover, -SO_3H is bonded to the aromatic nuclear carbon atom of R, and p indicates an average value defined below.
Average value of p = q × ((average of total number of aromatic nuclear carbon atoms in R/6))
Here, q is in the range of 0.01 to 1.5. A selectively permselective charged membrane consisting essentially of a polyhydantoin having pendant sulfonic acid groups consisting mainly of repeating units represented by the following. 2 The following general formula [A] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [A] [However, in the formula -
Hy- is a formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc.
4 represents a monovalent organic group selected from the alkyl group, cyclohexyl group, phenyl group, and tolyl group. Note that the above formula also includes the form in which the left and right sides are reversed).
represents at least one type of (2+p)-valent organic group having an average carbon number of 6 to 40, of which 40% or more are aromatic nuclear carbon atoms. Moreover, -SO_3H is bonded to the aromatic nuclear carbon atom of R, and p indicates an average value defined below. Average value of p = q × ((average of total number of aromatic nuclear carbon atoms in R/6))
Here, q is in the range of 0.01 to 1.5. A polyhydantoin having a pendant sulfonic acid group consisting mainly of repeating units represented by ] is dissolved in an organic polar solvent or an organic polar solvent to which a solubility regulator is added if necessary, and solidified after casting. A method for producing a permselectively charged membrane.