KR100477589B1 - Method for producing polyamide reverse osmosis composite membrane - Google Patents

Abstract

The present invention relates to a reverse osmosis composite membrane used to remove salts from surface water, seawater, etc. and to be used as drinking water or agricultural water, and more particularly, to provide a separation membrane exhibiting high flow rate characteristics as compared with a conventional separation membrane. Is there.

The present invention is to form a polyamide membrane by interfacial polymerization of a polyfunctional amine aqueous solution on a porous support layer and an organic solution containing an amine reactive compound selected from a polyfunctional acid halogen compound, a polyfunctional sulfone halogen compound, or a polyfunctional isocyanate. In the preparation of the reverse osmosis composite membrane of the present invention, a polyamide reverse osmosis composite membrane production method characterized in that the addition of a salt compound obtained by the reaction of a strong acid and a polyfunctional amine to the polyfunctional amine aqueous solution, the method By using this, it is possible to manufacture a separation membrane exhibiting a high flow rate compared with the conventional.

Description

Method for producing polyamide reverse osmosis composite membrane

The present invention relates to a reverse osmosis membrane used to selectively separate various dissolved substances from a solution, and more particularly, to a polyamide reverse osmosis composite membrane and a method of manufacturing the same.

The most economical method is to use a reverse osmosis membrane that can separate substances at the molecular level to remove salts from surface water, sea water, etc. and use them as drinking water, agricultural water, and industrial water.

In general, the solute can be separated from the solvent using various kinds of membranes. Examples of these are microfiltration, ultrafiltration and reverse osmosis. An example of the application of reverse osmosis is the desalination of semi-saline or seawater for industrial, agricultural and household purposes. This desalination is to obtain purified water through the reverse osmosis membrane by applying pressure to the water in which the ions or molecules are dissolved. Salt, dissociation ions and organic molecules do not pass through the membrane. Osmotic pressure is the reverse of reverse osmosis, and as the concentration of feedwater increases, the osmotic pressure gradually increases.

Membrane desalination must have some important performances for commercial use in large quantities of seawater or hemi- brine. The most important measures of performance are SALT REJETION and FLUX. In order to be more economical than other methods (evaporation method, ion exchange method, etc.), the flow rate of seawater is more than 10 gfd (gallons / ft ² · day) at 800 psi, more than 15 gfd at 220 psi, and the salt removal rate is It should be more than 97%.

The most common reverse osmosis membrane consists of a very thin polyamide film on a porous support layer. In particular, this polyamide film consists of interfacial polymerization between a polyfunctional amine and a polyfunctional acid halide. Examples of such composite membranes are described in US Pat. No. 4,277,344 to Cadot. This patent describes aromatic polyamides by interfacial polymerization between an aromatic polyfunctional amine having at least two primary amine groups and an aromatic polyfunctional acid halide having at least three acid halide groups. Specifically, the polysulfone support layer is immersed in an aqueous solution of meta-phenylenediamine, and then excess meta-phenylenediamine is removed from the surface, and a freon solution in which trimezoyl chloride is dissolved is applied. The contact time for the interfacial reaction is 10 seconds but the reaction is actually completed in 1 second. The polysulfone / polyamide composite membrane is then dried in air. The membranes of the cadots exemplified above showed excellent flow rates and salt rejection rates, but further studies have been conducted to increase the flow rate and salt rejection performance in various ways. Efforts have also been made to increase the membrane's resistance to phenomena such as chemical degradation. Many of these methods choose to use various additives in solution during interfacial polymerization. For example, in US Pat. No. 4,872,984, Tomaske is an aromatic polyfunctional acid halide compound obtained by applying an aqueous coating layer obtained by applying an aqueous solution containing an aromatic monomer polyfunctional amine and an amine salt compound having at least two or more amine groups on a microporous support. Or by contacting with an organic solution containing a mixture thereof to dry the membrane produced by interfacial polymerization to produce a reverse osmosis composite membrane, wherein the amine salt compound mentioned above is a monomeric amine salt made of strong acid and tertiary or quaternary amine. .

The amines used at this time are tertiary amines, trialkylamines, N-alkylcycloaliphatic amines, bicyclic tertiary amines or quaternary amines are tetraalkylammonium hydroxides, benzyltrialkylammonium hydroxides and mixtures thereof. Etc. are used.

However, the patent mentions only strong acids and monovalent tertiary amines and does not refer to the water soluble strong acids and polyfunctional tertiary amines described in the present invention.

It is an object of the present invention to provide a polyamide reverse osmosis composite membrane having a high flow rate and excellent salt rejection ratio compared to a conventional reverse osmosis membrane, and particularly using a salt compound that is a reactant of a polyfunctional tertiary amine during interfacial polymerization. The purpose is to produce a composite membrane having properties.

The present invention provides a polyamide membrane by interfacial polymerization of an aqueous polyfunctional amine solution and an organic solution containing an amine reactive compound selected from polyfunctional acid halogen compounds, polyfunctional sulfone halogen compounds, and polyfunctional isocyanates on a porous support layer. In preparing the composite membrane, a salt compound obtained by the reaction of the polyfunctional amine is added and reacted.

Hereinafter, the present invention will be described in detail.

In the present invention, the support layer is a porous substrate. The porous support layer used in the present invention should generally have sufficient pore size to allow the production water to pass through, and also should not be so large that the pore size is too large to sink. The pore size of the support layer is generally about 1 to 300 nm, and when it exceeds 300 nm, the thin film sinks and the flat membrane shape is broken.

Examples of the porous support layer include various kinds of halogenated polymers such as polysulfone, polyethersulfone, polyimide, polyamide, polypropylene, polyvinylidene fluoride. The thickness of the porous support layer is not critical in the present invention but generally the thickness of the porous support layer is 25-125 μm (more preferably 40-75 μm).

In the present invention, the polyfunctional amine is preferably used having at least two or more amine groups (more preferably, two to three amine groups). The amine group is a primary or secondary amine group (more preferably a primary amine group). The polyfunctional amine used in the present invention uses one kind or a mixture of two or more kinds. Examples of suitable polyfunctional amines are aromatic primary amines such as meta-phenylenediamine, para-phenylenediamine or substituents thereof. Substituents include alkoxy groups such as methyl or ethyl groups, hydroxy alkyl groups, hydroxy groups or halogen atoms. Examples of suitable polyfunctional amines include N-alkyl, N-aryl substituents and unsubstituted in 1,3-propanediamine derivatives and cyclohexanamine, piperazine in aliphatic primary diamines in cyclic polyfunctional amines. And their alkyl derivatives, metaphenylene diamines and paraphenylenediamines in aromatic polyamines, and derivatives thereof including alkyl, alkoxy and halogen substituents. In addition, there are aromatic secondary amines N, N'-dimethyl-1,3-phenylenediamine, N, N'-diphenylenediamine, benzidine, xylenediamine and derivatives thereof. Of these, preference is given to the aromatic primary secondary amines, among which metaphenylenediamine is more preferred. The aqueous solution of the polyfunctional amine contains about 0.1-20% by weight of the amine (more preferably 0.5-8% by weight). In addition, it is good to adjust the pH of the amine solution so that it is in the range of 7 to 10, wherein the pH can be adjusted by adding a basic substance, but the amine solution contains an amine salt that can act as an acid acceptor of at least one amine group. In this case, it is not particularly necessary to add a basic substance. In the present invention, the amine salt is a reactant of a strong acid and a polyvalent amine, more preferably a reactant of a strong acid and a tertiary polyamine, wherein the polyamine has n tertiary amine groups, where n is 2 or more and reacts with a strong acid. Reacts at least 1: 1 and 1: n at molar ratios More specifically, the reaction molar ratio of the tertiary polyamine salt and the strong acid is 1: 1 or more and 1: (0.95) n or less (more preferably 1: 1 or more and 1: (0.9) n or less). More preferably, only one functional group of the tertiary polyamine is present as a salt and the other functional groups act freely as a base.

In the present invention, regardless of the specific theory, the tertiary polyamine salt acts as a pore-forming agent of the polyamide membrane to improve the flow rate, and at the same time, the tertiary amine receives the acidic acid generated during the interfacial reaction between the polyfunctional amine and the acid halide ( acts as a proton acceptor. Due to the co-functionality of these tertiary polyamine salts, tertiary polyamine salts with partial salts rather than being fully salted result in an improved flow rate membrane.

Tertiary polyamine salts used in the present invention are salts of strong acids with tertiary polyamines comprising two or more amine groups. Examples of strong acids are aromatic sulfonic acid, aliphatic sulfonic acid, cycloaliphatic sulfonic acid, trifluoroacetic acid, nitric acid, hydrochloric acid, sulfonic acid and mixtures thereof, and specific examples thereof. Methanesulphonic acid (MS), toluenesulphonic acid (TSA), camphorsulphonic acid (CSA), ethanesulphonic acid (ESA), benzenesulphonic acid (BSA) and the like.

Tertiary amines include 1,4-diazabicyclo [2,2,2] octane (DABCO), 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU), 1,5 -Diazabicyclo [4,3,0] non-5-ene (DBN), 1,4-dimethylpiperazine, 4- [2- (dimethylamino) ethyl] morpholine, N, N, N ', N ', -Tetramethylethylenediamine, N, N, N', N, -tetramethyl-1,3-butanediamine, N, N, N ', N',-tetramethyl-1,4-butanediamine (TMBD ), N, N, N ', N',-tetramethyl-1,3-propanediamine, N, N, N ', N',-tetramethyl-1,6-hexanediamine (TMHD), 1,1 , 3,3-tetramethylguanidine (TMGU), N, N, N ', N ",-pentamethyldiethylenetriamine and mixtures thereof.

Aqueous polyfunctional aqueous solution contains 0.2-12 weight% of tertiary polyamine salts. Examples of polyfunctional acid halide compounds include trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) and mixtures thereof, such as di- or tricarboxyl acid halides. The reaction compound of the polyfunctional amine is used to adjust the concentration of 0.01 ~ 10% (more preferably 0.01 ~ 0.5%) in the organic solution, wherein the organic solvent used is hexane, cyclohexane, heptane and not mixed with water Alkane derivatives of the same 8 to 12 carbon atoms and halogenated hydrocarbons such as freon.

In order to make the high flow rate reverse osmosis membrane in the present invention, the porous support layer exemplified above is applied by a manual or continuous method using the aqueous polyfunctional amine solution exemplified above, and after removing the excess solution from the applied porous support layer, the polyfunctional acid halogen The reaction is coated on the surface of the porous layer by contacting the organic solution of the compound or polyfunctional sulfonhalogen compound or polyfunctional isocyanate for 5 seconds to 10 minutes (more preferably 20 seconds to 4 minutes). After coating is dried for 5 to 20 minutes (more preferably 4 minutes) at 50 ~ 130 ℃ after washing for 1 to 30 minutes in an alkaline aqueous solution of room temperature to 95 ℃ temperature to prepare a reverse osmosis membrane.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, in which the following experimental examples are described for illustrative purposes only and are not intended to limit the scope of the present invention.

<Measurement of performance>

As the performance of the membrane, the flow rate was measured at a concentration of 2000 ppm sodium chloride (NaCl) at 25 ℃, 225 psig, the salt excretion was calculated by the following equation. Where R is the salt excretion rate, C _f is the concentration of solute in feed water and C _p is the concentration of solute in permeate.

<Example 1>

A 140 μm-thick polysulfone microporous substrate was immersed in an aqueous solution containing 2 wt% metaphenylenediamine, 1 wt% DABCO, 0.85% MSA for 40 seconds, and the surface was drained, and then placed in a 0.1 wt% trimezoyl chloride solution. Immersion was for 1 minute. The composite membrane thus prepared was dried at 90 ° C. for 3.5 minutes, washed well with 60 ° C., 0.2% Na ₂ CO ₃ aqueous solution, and washed with distilled water again. As a result of measuring physical properties, the salt rejection rate was 97% and the flow rate was 32.3 gfd.

<Example 2>

In the same manner as in Example 1, but the aqueous polyfunctional amine solution was used 2% by weight metaphenylenediamine, 2% by weight DABCO, 1.7 MSA. As a result of measuring the physical properties, the salt rejection rate was 28.4 gfd for the flow rate of 96.7%.

<Example 3-25 and Comparative Example A>

Except that the composition of the polyfunctional amine aqueous solution was carried out in the same manner as in Example 1 except that the composition was shown in Table 1, the physical properties thereof are shown in Table 1.

TABLE 1

As can be seen from the above examples and comparative examples, the polyamide membrane obtained by interfacial polymerization with an amine reactive compound by adding a salt compound obtained by the reaction of a strong acid and a polyfunctional amine to an aqueous polyfunctional amine solution according to the present invention has excellent high flow rate. Has performance.

Claims (6)

A method for producing a polyamide reverse osmosis composite membrane, in which a polyamide membrane is formed by interfacial polymerization by contacting an aqueous solution containing a polyfunctional amine solution with a polyfunctional amine reactive compound on a porous support layer, wherein a strong acid and A method for producing a polyamide reverse osmosis composite membrane, comprising 0.1 to 12% by weight of a tertiary polyamine salt prepared by reaction with a polyfunctional tertiary amine. The method of claim 1, wherein the polyfunctional amine-reactive compound is any one selected from the group consisting of a polyfunctional acid halogen compound, a polyfunctional sulfone halogen compound, and a polyfunctional isocyanate. The method according to claim 1, wherein the strong acid is any one selected from the group consisting of aromatic sulfonic acid, aliphatic sulfonic acid, cycloaliphatic sulfonic acid, trifluoro acetic acid, nitric acid and hydrochloric acid. The method for producing the polyamide reverse osmosis composite membrane. The method of claim 1, wherein the multifunctional tertiary amine is 1,4-diazabischloro [2,2,2] octane, 1,8-diazabischloro [5,4,0] undec-7-ene, 1 , 5-diazabicyclo [4,3,0] is -5-ene, 1,4-dimethylpiperazine, 4- [2- (dimethylamino) ethyl] morpholine, N, N, N ', N' , -Tetramethylethylenediamine, N, N, N ', N-tetramethyl-1,3-butanediamine, N, N, N', N ',-tetramethyl-1,4-butanediamine, N, N , N ', N',-tetramethyl-1,3-propanediamine, N, N, N ', N',-tetramethyl-1,6-hexanediamine, N, N, N ', N', N ″, -Pentamethyldiethylenetriamine and 1,1,3,3, -tetramethylguanidine is a single or a mixture of two or more selected from the group consisting of the method for producing a polyamide reverse osmosis composite membrane. The method according to claim 1, wherein the tertiary polyamine salt is prepared by reaction with a strong acid and a tertiary polyamine having n tertiary amine groups, wherein n is 2 or more. The polyamide reverse osmosis composite membrane according to claim 1, wherein the tertiary polyamine salt is prepared at a reaction molar ratio of 1: 1 to 1: n with a tertiary polyamine having a strong acid and n tertiary amine groups. Way.