JPS63197501A - Composite semipermeable membrane and production thereof - Google Patents

Abstract

PURPOSE:To obtain a composite semipermeable membrane having high desalting properties even under operation at low pressure by forming an ultrathin membrane from cross-linked polyamide which has piperazine as an essential component and has an acid component shown in a specified formula as a constitutional component. CONSTITUTION:For example, a supporting polysulfone membrane reinforced with fiber is coated with an aq. soln. incorporating piperazine and secondary amine such as 1,3-bis(4-piperidyl)propane and furthermore a surfactant such as dodecyl sodium sulfate and a reaction accelerator such as trisodium phos phate and air-dried. Then a soln. obtained by dissolving multifunctional acid chloride such as isophthalic acid chloride and cyclohexane dicarboxylic acid chloride in an organic solvent immiscible with water such as trichlorotrifluoroe thane is applied and interfacial polycondensation is performed to produce a cross-linked polymer. By such a way, as an ultrathin membrane coating the supporting membrane, a composite membrane consisting of cross-linked polyam ide which has piperazine or its homologue as an essential component and contains a constitutional component shown in formula I, II is obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a semipermeable membrane for selectively permeating components of a liquid mixture, and particularly for desalinating and desalinating can water. It also selectively removes or recovers pollutants or effective substances contained therein from wastewater that causes pollution, such as dyeing wastewater and electrocoating paint wastewater, thereby contributing to the closure of wastewater. More specifically, the present invention relates to a high-performance composite semipermeable membrane that can be used to produce ultrapure water used in the production of semiconductors.

[Prior Art] Conventionally, semipermeable membranes that have been used industrially include asymmetric membranes made from cellulose acetate, such as those disclosed in US Patent No. 3.
There are lob-type membranes described in Patent No. 133.132 and Patent No. 3.133.131. However, this membrane has problems with hydrolysis resistance, microbial resistance, chemical resistance, etc. In particular, when trying to improve permeability, it is not possible to manufacture a membrane that has both pressure resistance and durability, so it is not used in some cases. However, it has not yet been put to practical use in a wide range of applications. Research into new materials that eliminate the drawbacks of these cellulose acetate asymmetric membranes is being actively conducted mainly in the United States and Japan, but aromatic polyamides, polyamide hydrazides (US Pat. No. 3,567, 632 @ specification), Polyamic acid (Japanese Patent Publication No. 55-37282), crosslinked polyamic acid (Japanese Patent Publication No. 5B-3769), polyimidazopyrrolone, polysulfonamide, polybenzimidazole, polybenzimidacylon, polyarylene oxide, etc. Although a material has been obtained that improves the disadvantages of cellulose acetate membranes, it is inferior to cellulose acetate membranes in terms of selective separation and permeability.

On the other hand, a composite membrane has been developed as a semipermeable membrane different from the lobe type, in which a microporous support membrane is coated with an active layer that substantially controls membrane performance. In composite membranes, it becomes possible to select the optimal materials for each application for the active layer and microporous support membrane, increasing the degree of freedom in membrane manufacturing technology. It also has the advantage of being able to be stored in a dry state, unlike a lobe-type membrane that must be stored in a constantly wet state.

There are two types of composite membranes: one in which the active layer is coated on a microporous support membrane via a gelling layer, and one in which the active layer is coated directly on the microporous support membrane. be. Specific examples of the former are JP-A No. 49-133282 and JP-A No. 5
Publication No. 5-38164, PB Report 80-18209
0, Japanese Patent Publication No. 59-27202, Japanese Patent Publication No. 56-40
No. 403, etc., and this type of membrane is said to be easier to form during industrial production than the latter membrane, and has been actively researched; however, when subjected to reverse osmosis treatment under low pressure, water permeability is often so low that satisfactory membrane performance cannot be obtained, and it is also difficult to obtain a membrane with sufficient chlorine resistance, which is important for the actual use of reverse osmosis membranes.

A specific example of the latter is U.S. Patent Nos. 3.74 & 64.
No. 2 Mei M, Specification No. 3.926.798, No. 4
, 277.344, JP-A-55-147106
No. 24303, Japanese Unexamined Patent Publication No. 58-24303, etc.
In order to achieve high permeability in this type of composite membrane, the active layer is coated very thinly, which tends to cause defects due to scratches or foreign matter in the microporous support membrane, and generally it is not stable during industrial production. It is said that it is difficult to obtain high-performance films with good reproducibility. However, most of the membranes that are said to have chlorine resistance, heat resistance, and chemical resistance are of the latter type, and piperazine-based membranes have attracted attention as chlorine-resistant membranes. Specific examples include U.S. Pat. However, the active layer is thick and the water permeability is low. Recently, a composite membrane with a high yield of water produced by crosslinking piperazine with an aromatic polyfunctional acid halide and producing 1qq by interfacial polycondensation has been proposed and attracted attention (for example, Japanese Patent Publication No. 5B-500062, U.S. Pat. No. 4,259).
．． 183 Specification, PB Report 288387) aThis membrane is an excellent membrane with high water permeability at low pressure,
It had the disadvantage that the rejection rate of sodium chloride was rather low at about 50%.

However, in the production of ultrapure water used in desalination processes and semiconductor manufacturing, recent trends have required membranes with high exclusion properties, and improvements to this piperazine-based composite membrane have been proposed. For example, JP-A-59-1791
No. 03, Japanese Patent Publication No. 61-27083), there was no membrane superior to the above-mentioned composite membrane using piperazine, such as poor water permeability.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned piperazine-based membrane (U.S. Pat. No. 4, 25
The object of the present invention is to obtain a composite semipermeable membrane that has high desalination properties even under low pressure operation by improving the method described in Japanese Patent Application No. 9.183.

[Means for solving problems] In order to achieve the above object, the present invention consists of the following configuration.

[(1) In a composite semipermeable membrane consisting of a microporous support membrane and an ultra-thin membrane covering the support membrane, the ultra-thin membrane contains piperazine or a homolog thereof as a main component, and has the following formula [I] and/or [II] C=O (R represents H or a hydrocarbon group with 1 to 3 carbon atoms.) (2) Microporous In a method for manufacturing a composite semipermeable membrane consisting of a support membrane and an ultra-thin membrane covering the support membrane, an aqueous solution containing piperazine or a homologue thereof represented by formula [IV] is applied onto a microporous support membrane, and a A water-immiscible organic solvent solution containing a polyfunctional acid halide containing formula [V] and/or [VI] is applied to the surface, and polycondensation is performed at the interface with the aqueous solution to form a crosslinked polymer. . A method for producing a composite semipermeable membrane, which comprises then performing a dry heat treatment.

(R- is a group or a CHt group, which may be the same or different, and n is an integer from O to 3.) (X is CI, -Br, -I, -F, and R is , ■ or C represents a hydrocarbon group of 1 to 3.) In the present invention, the ultra-thin film layer is usually made of a crosslinked polyamide formed by an interfacial polycondensation reaction, and is a crosslinked polyamide having a constituent represented by -N N-. It is a layer which has piperazine or its homologue polyamide as a main component and contains constituent components represented by formulas [I] and [I[] and has substantially separation performance. The thickness can be arbitrarily selected between 10nll and i, ooo depending on the purpose, but if it is thin, it is likely to cause defects, and if it is thick, the water passing rate will decrease, so from the viewpoint of balance, 2 Onl 11 ~300 nm is preferred.

In the present invention, crosslinked piperazine polyamide means -N
It is a cross-linked monopolymer whose main components are a constituent component represented by N-, a substituted and/or unsubstituted aromatic ring, and an amide bond that can connect them. 288387, 80-12757
It is listed in 4th grade. In the present invention, high desalination performance is made possible by containing components represented by formulas [I] and [II] in addition to these components.

Examples of the constituent components represented by formulas [I] and [I[] include the following compounds.

Among the above compounds, the following are preferred from the viewpoint of performance of the composite semipermeable membrane.

In the above description, the type and position of the substituent on the aromatic ring are not particularly limited in the present invention, nor is the position of the substituent particularly limited.

Any method may be used to incorporate these components into an ultra-thin film having substantial separation performance, but for piperazine, the secondary amine represented by formula [IV], and the crosslinking agent, the following formula is used: Forming an ultra-thin film by interfacial polycondensation using a polyfunctional acid halide represented by
This is preferable from the viewpoint of ease of handling raw materials and ease of film formation.

(n represents an integer from O to 3.) (X=CI, -Br, -I, -F) In the present invention, the microporous support membrane has substantially no separation performance, and It is a membrane that supports an ultra-thin film, and has uniform fine pores or fine pores that gradually become larger from one side to the other.
Preferably, the support membrane has a structure of 100 nlB.

In particular, a microporous support membrane made of polysulfone is preferred.

Next, a manufacturing method according to the second invention will be explained.

The procedure of the method for producing a composite semipermeable membrane of the present invention is to add an aqueous solution containing the above-mentioned piperazine and a secondary amine represented by formula [IV] (hereinafter collectively referred to as a composition) to a microporous support membrane. The porous support membrane is coated on one side, and then air-dried and/or heat treated to evaporate some or all of the water, and then a compound of the formula [V ], [VI] After applying a solution mainly composed of a polyfunctional acid halide and carrying out a crosslinking reaction,
Obtained by drying.

The ultra-thin membrane having substantially separation ability in the composite semipermeable membrane is a water-immiscible organic solvent solution containing the composition and a polyfunctional acid halide containing formulas [V] and [VI]. using
Although it is formed by interfacial polycondensation, in the present invention, it is possible to further incorporate additives into the composition to significantly improve the water transport rate of the composite semipermeable membrane. Examples of such additives include sodium alkyldiphenyl ether disulfonate, medilene bis (sodium naphthalene sulfonate), and nlubitol, and sodium alkyldiphenyl ether disulfonate is one of the most effective additives in the composition described later in terms of the performance of the composite semipermeable membrane. Since it also serves as a surfactant, it is a particularly preferred additive. The alkyl group is
From the viewpoint of effectiveness as a surfactant, a dodecyl group is preferred. However, in practice, alkyl groups other than dodecyl groups may be mixed, and two or more alkyl groups may be present.

It is also more effective to add an alkaline metal compound such as trisodium phosphate.

Furthermore, in order to improve the wettability of the composition to the surface of the microporous support membrane, it is effective to add a surfactant to ensure uniform adhesion.Among them, anionic surfactants are preferred, such as sodium dodecyl sulfate and alkylbenzene sulfone. Although sodium alkyl diphenyl ether disulfonate can be selected from sodium chloride, sodium alkyl diphenyl ether disulfonate is particularly effective in obtaining good membrane performance. As the surfactant, it is generally good to use about 0.01 to 4% by weight. A water-soluble organic solvent that does not deteriorate the microporous support membrane may be added to these compositions.

In addition, adding an alkaline metal salt, such as a hydrochloric acid scavenger such as trisodium phosphate or sodium hydroxide, is also effective in promoting the reaction between a secondary amine and a polyfunctional acid halide. The combined use of an acylation catalyst may also bring about good effects. Trisodium phosphate is also preferred from the viewpoint of improving the water transport rate of the composite semipermeable membrane.

In the present invention, the polyfunctional acid halide may be any compound that reacts with the secondary amines to form an ultra-thin film of crosslinked polyamide, such as trimesic acid halide,
Aromatic polyfunctional acid halides such as isophthalic acid halide, terephthalic acid halide, diphenyldisulfonic acid halide, and chlorosulfonic acid halide, and formula [V], [
Examples of aliphatic polyfunctional acid halides include those shown in VI], but in consideration of solubility in membrane forming solvents and performance of the composite semipermeable membrane, trimesic acid chloride, isophthalic acid chloride, terephthalic acid chloride, and cyclohexane are included. Tricarboxylic acid chloride, cyclohexanedicarboxylic acid chloride and mixtures thereof are preferred.

These mixing ratios are not particularly limited.

Further, the polyfunctional acid halide is used by dissolving the polyfunctional acid halide in an amount of usually 0.01 to 2.0% by weight, preferably 0.1 to 0.5% by weight in an organic solvent.

The secondary amine that is a component of the composition of the present invention is preferably piperazine and 1,3-bis(4-piperidyl)propane of the following formula.

The concentration of these components is 0.1 to 10% by weight, preferably 1
~4% by weight. The composition ratio of piperazine and 1,3-bis(4-piperidyl)propane is 1 part by weight of piperazine to 0.0 part of 1,3-bis(4-piperidyl)propane.
The amount is preferably 5 to 0.5 parts by weight.

In the present invention, an organic solvent is one that is immiscible with water, dissolves acid chloride, does not destroy the microporous support membrane, and is capable of forming a crosslinked polyamide through interfacial polycondensation. It may be either.

Preferred examples include hydrocarbon compounds, cyclohexane,
Examples include trichlorotrifluoroethane, but from the viewpoint of reaction rate and volatility of the solvent, at least one selected from n-hexane and trichlorotrifluoroethane is preferred, and considering the safety issue of flammability, it is more preferred. Preferred is trichlorotrifluoroethane.

Any known application method can be applied to coating the microporous support membrane with the composition, such as coating the composition on the support membrane, dipping the support membrane in the composition, etc. Can be mentioned. Among these methods, the method of coating the composition is preferable from the viewpoint of uniform coating on one side of the microporous support membrane, and also from the viewpoint of workability. When the microporous support membrane is immersed in the composition, it is preferable to take measures in advance to prevent the composition from adhering to the other side of the microporous support membrane in the coating step.

In such a coating process, a draining process is generally provided to remove excess composition. As a method for draining the liquid, for example, there is a method of holding the membrane surface vertically and allowing it to flow down by gravity.

The coated microporous support membrane is dried using an air dryer or a heated dryer, usually in the range of room temperature to 150°C, and the drying speed varies depending on the method, that is, the heat introduction method or the type of dryer. Therefore, the time should be selected in the range of 0.5 to 60 minutes. A solution of a polyfunctional acid halide in a water-immiscible organic solvent is applied to a colander, the liquid is drained off, and then air-dried or heat-treated to obtain a composite semipermeable membrane. This drying process is typically performed at room temperature
The temperature is 150°C, and the time is determined depending on the temperature. This drying and heat treatment step has the effect of preventing the ultra-thin film from peeling off from the microporous support membrane.

The composite semipermeable membrane thus obtained can be used as is, but the surface of the ultra-thin layer of the composite semipermeable membrane can be covered with a protective polymer film, and it is practically desirable to cover it with a protective film. The protective film is coated on the surface of the ultra-thin film layer by applying a polymer solution of the protective film to the surface of the dried composite semipermeable membrane and then drying it.

Examples of such polymers include water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone, with polyvinyl alcohol being particularly preferred from the viewpoint of coating strength.

These polymers are generally used as a 0.5 to 10% by weight aqueous solution, and the coating method is not limited to the dipping method, but can also be applied by spraying or spacing. The composite semipermeable membrane coated in this manner is dried in a hot air drying conveyor to form a final product. The drying conditions are generally 6
Drying at a temperature in the range of 0 to 120°C for 2 to 10 minutes is suitable.

EXAMPLES In the following examples, the selective separation performance, salt rejection, was determined by conventional means by measuring electrical conductivity.

In addition, as permeation performance, the water permeation rate was determined by the amount of water permeation per unit area and unit time.

Reference example Taffeta made of polyester fibers with a length of 30 CI 11 and a width of 20 cm (multifilament yarn of 150 denier in both warp and weft, weaving density of 90 pieces/inch in length, 67 pieces/inch in width, thickness 160 μm) was fabricated with glass. It was fixed on a board, and 16% by weight of polysulfone (trade name: UdelP-3500, manufactured by Conion Carbide) was placed on it.
A W4 fiber-reinforced polysulfone support membrane (hereinafter abbreviated as FR-PS support membrane) was prepared by casting a dimethylformamide (DMF) solution to a thickness of 200 μm at room temperature (20°C), immediately immersing it in pure water, and leaving it for 5 minutes. Create. The FR-PS support film thus obtained (thickness 21
The pure water permeability coefficient between 0μm and 215μm is 1Ky/pressure.
~, 0.005-0.019/m measured at room temperature 25°C
-5ee -atm T- was there.

Example 1 1.0% by weight of piperazine, 0.2% by weight of 1,3-bis(4-piperidyl)propane, and 0.5ffl of sodium dodecyl sulfate were added to the FR-PS support membrane obtained in Reference Example.
An aqueous solution (composition) containing 1% FF and 10% by weight trisodium phosphate was applied and air-dried for 2 minutes at room temperature. Thereafter, a mixture of isophthalic acid chloride and cyclohexanedicarboxylic acid chloride (
Apply a solution containing 0.5% by weight of 4:1),
Thereafter, it was heat-treated with hot air at 100°C for 5 minutes. The thus obtained composite membrane was subjected to a reverse osmosis test under the conditions of a pressure of 15 kg/cat, a 0.15% NaCl aqueous solution in raw water, 25°C, and a pf of -16.5 for 14 hours.
, it exhibited a water permeation rate of 1.1 m''/m2·day.

Example 2 1.0% by weight of piperazine, 0.21i% of 1,3-bis(4-piperidyl)propane, and 0.5% by weight of sodium dodecyl Is were added to the FR-PS support membrane obtained in the reference example.
, an aqueous solution (composition) containing 1.0% by weight of trisodium phosphate was applied and dried with hot air at 70° C. for 1 minute. Thereafter, a solution containing 0.5% by weight of a mixture of trimesic acid chloride and cyclohexanetricarboxylic acid chloride (weight ratio 4:1) was applied to trichlorotrifluoroethane, and then heat treated with hot air at 100°C for 5 minutes. The thus obtained composite membrane was subjected to a reverse osmosis test under the same conditions as in Example 1, and as a result showed performance at a salt weight of 5% for 20 hours and a water permeation rate of 1.3 tn'/m2/day. .

Example 3 Piperazine 1.0% by weight, sodium dodecyl sulfate 0.5% by weight,
An aqueous solution (composition) containing 1.0% by weight of trisodium phosphate was applied and dried for 2 minutes at room temperature. After that, a mixture of isophthalic acid chloride and cyclohexanedicarboxylic acid chloride (weight ratio 4:
A solution containing 0.5% by weight of 1) is applied, and then 1
Heat treatment was performed with hot air at 00°C for 5 minutes. When the thus obtained composite membrane was subjected to a reverse osmosis test under the same conditions as in Example 1, the salt removal rate was 70% after 24 hours, and the water permeation rate was 1.3.
v! /m2·day.

Example 4 Piperazine 1.0% by weight, sodium dodecyl sulfate 0.5% by weight,
An aqueous solution (composition) containing 1.0@1% trisodium phosphate was applied and dried with hot air at 70° C. for 1 minute. Thereafter, a solution containing 0.5% by weight of a mixture of trimesic acid chloride and cyclohexanetricarboxylic acid chloride (weight ratio 2:1) was applied to trichlorotrifluoroethane, and then heat treated with hot air at 100° C. for 5 minutes. The thus obtained composite membrane was subjected to a reverse osmosis test under the same conditions as in Example 1, and the results showed that after 20 hours, the salt content was 70% and the water permeation rate was 1.4 m'/m2·day. .

Example 5 The composite membrane obtained in Example 2 was cut to an appropriate size, and the ultra-thin layer was peeled off by immersing it in methylene chloride.

This was absorbed and filtered through a glass filter and passed from house to house.

30 ml of the sample thus obtained was hydrolyzed together with 6NJHa12- at 180°C. The liquid from which insoluble matter was removed was dried and its weight was measured, and the weight was 25~. This was dissolved in a mixed solution of methyl alcohol (2 Inl) and ethyl ether (10 m>), and methyl esterification was performed by blowing in diazomethane. After distilling off the solvent under reduced pressure, 2 Inl of methyl acetate and 0.5!nl of trifluoroacetic acid was added and allowed to stand for 5 minutes. After distilling off the solvent under reduced pressure, it was dissolved in 1 m of methyl alcohol and analyzed by GC-MS.
The composition was investigated by the method.

As a result, the mass spectrum revealed that piperazine, 1.3
Molecular ion peaks and fragment ion peaks corresponding to the trifluoroacetyl compound of -bis(4-piperidyl)propane, trimesic acid chloride, and methyl ester of cyclohexanetricarboxylic acid chloride were detected.

According to gas chromatography analysis using an internal standard method, the ratio of trimesic acid chloride to cyclohexanetricarboxylic acid chloride was about 4:1.

Comparative Example 1 1.0% by weight of piperazine and 0.5% by weight of sodium dodecyl sulfate were added to the FR-PS support membrane obtained in the reference example.
, an aqueous solution (composition) containing 1.0% by weight of trisodium phosphate was applied and dried for 2 minutes at room temperature. After that, a mixture of isophthalic acid chloride and trimesic acid chloride (weight ratio 2:1) was added to trichlorotrifluoroethane.
．． A solution containing 5% by weight was applied and air-dried. The composite membrane thus obtained was heated at a pressure of 15 KI/ci,
Raw water 0.15% NaCl aqueous solution 25°C, pI-16.

As a result of a reverse osmosis test under the conditions of No. 5, it showed a performance of 15 hours desalination weight of 4% and a water permeation rate of 2.8 m'/m''·day.

Comparative Example 2 Piperazine 1.0% by weight, sodium dodecyl sulfate 0.5% by weight,
An aqueous solution (composition) containing 1.0% by weight of trisodium phosphate was applied and air-dried for 2 minutes at room temperature. After that, a solution of 0.5Wffi% trimesic acid chloride dissolved in trichlorotrifluoroethane was applied, and then 10% of trimesic acid chloride was dissolved.
Heat treatment was performed with hot air at 0° C. for 5 minutes. The thus obtained composite membrane was subjected to a reverse osmosis test under the same conditions as in Example 1. As a result, the 20-hour contact desalination rate was 55%, and the water passing rate was 1°6 m'.
/m2・day.

[Effects of the Invention] The composite semipermeable membrane of the present invention is for selective permeation separation of liquid mixtures, and in particular can be used for producing ultrapure water used in the production of kansui and semiconductors. At the same time, it has become possible to provide a membrane that has both high desalination properties and high water passage rates, which were previously difficult to achieve.

Claims (1)

[Scope of Claims] (1) A composite semipermeable membrane consisting of a microporous support membrane and an ultra-thin membrane covering the support membrane, wherein the ultra-thin membrane contains piperazine or a homolog thereof as a main component, and has the following formula [I] and/or [II
A composite semipermeable membrane comprising a crosslinked polyamide containing an acid component represented by the following as a constituent component. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [I] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [II] (R represents H (or a hydrocarbon group with 1 to 3 carbons) (2) Patent In claim (1), a composite semipermeable membrane characterized in that piperazine or a homolog thereof is a component represented by formula [III]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [III ] (R' is H or CH_3 group and may be the same or different, n represents an integer from 0 to 3.) (3)
The composite semipermeable membrane according to claim (1), wherein the microporous support membrane is made of polysulfone. (4) In a method for producing a composite semipermeable membrane consisting of a microporous support membrane and an ultra-thin membrane covering the support membrane, an aqueous solution containing piperazine or a homolog thereof represented by formula [IV] is applied to the microporous support membrane. Formula [V] and/or [VI]
A water-immiscible organic solvent solution containing a polyfunctional acid halide containing polyfunctional acid halide is applied, polycondensation is performed at the interface with the aqueous solution to form a crosslinked polymer, and then a dry heat treatment is performed. A method for manufacturing a composite semipermeable membrane. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [IV] (R' is H or CH_3 group, and may be the same or different, n indicates an integer from 0 to 3.) ▲Mathematical formulas, chemical formulas, tables, etc. etc.▼[V] ▲Mathematical formulas, chemical formulas, tables, etc.▼[VI] (X represents Cl, -Br, -I, -F, R is H or a hydrocarbon group with 1 to 3 C )