KR100477590B1 - Method for the reverse osmosis membrane with high flux - Google Patents

Abstract

The present invention relates to a method for producing a reverse osmosis membrane which is useful for separating water at a molecular level and removing salts from brackish water or seawater, which is useful for supplying water for household, construction, and chemical processes. The purpose is to provide a semi-permeable reverse osmosis membrane with excellent salt rejection.

The present invention is coated with an aqueous solution of one or two or more water-soluble polyfunctional amines on a porous support layer and the excess solution is removed, and then an organic solvent in which an amine-reactive compound such as polyfunctional acyl halide and phosphinyl alkyl chloride are dissolved together. The membrane formed by contacting the support layer to cause interfacial polymerization on the surface of the support layer is produced by washing with a basic aqueous solution. The reverse osmosis membrane prepared by the above method has a characteristic of high flow rate, and thus, during braking or seawater treatment. useful.

Description

High-flow reverse osmosis membrane manufacturing method {METHOD FOR THE REVERSE OSMOSIS MEMBRANE WITH HIGH FLUX}

The present invention relates to the preparation of a reverse osmosis membrane having a high flow rate and excellent salt rejection rate useful for treatment of seawater or semi-saline water.

In general, dissociated materials can be separated from the solvent by membranes having selectivity such as microfiltration, ultrafiltration, and reverse osmosis membranes. Reverse osmosis membranes are economical for the separation of molecular materials and for the removal of salts from brackish or seawater to provide water for domestic, construction and chemical processes. Important desalination factors are membrane desalination and flow rates, and considering the economics of the membrane process, the flow rate should be at least 10 gallon / ft ² -day (gfd) at 800 psi in seawater and at least 15 gfd at 220 psi in brackish water. .

Known semipermeable reverse osmosis membranes used in desalination are several forms of polyamide membranes, in particular crosslinked aromatic polyamide membranes are mentioned in US Pat. Nos. 3,904,519, 3,996,318, 4,277,344.

According to US Pat. No. 4,277,344, filed by Cadette, it is mentioned that a salt removal rate of 99.5% and a flow rate of 35 gfd can be produced under seawater desalination conditions. Such reverse osmosis membranes are obtained by interfacial polymerization of aromatic polyamines containing two primary amine substituents and aromatic acyl halides having three or more acyl halide functional groups on the microporous polysulfone support. In particular, it was reported that its performance was excellent when the methylphenyldiamine (MPD) dissolved in water was reacted with trimesoyl chloride (TMC) dissolved in Freon (trichlorotrifluoroethane, Freon TF, DuPont).

Freon has been used as a very good solvent for interfacial polymerization because of its inertness, but since 1990 it is restricted to use due to the ozone depletion effect of freon, and since 2002, all freon production is banned. Replacement was required. Since then, a patent has been published that uses hexane as an alternative solvent, and it has been proposed to use a solvent having a boiling point higher than that of hexane due to the risk of fire that may occur due to the volatility of hexane. Drying requirements were required, and this change in manufacturing conditions lowered the permeability of the membrane. In order to prevent degradation of the properties of the membrane during the drying process, additives were added or a study on the post treatment method was conducted.

According to Tomashke, U.S. Patent No. 4,872,984, when an amine salt is added to an amine aqueous solution layer interfacially polymerized with an acyl halide dissociated in a hydrocarbon solvent having 8 to 12 carbon atoms, the surface is polymerized, and the membrane is dried in the range of 70 to 100 ° It is said that the performance of the amine salt is more than 20gfd under the brackish condition of 220psi.

U.S. Patents 4,950,404 and 4,983,291, invented by Chau et al., Disclose a membrane preparation method for adding nonpolar and polar solvents in an amine solution and post-treatment with acid. This method also prevents the decrease in flow rate by increasing the temperature to 100 ° C. after the membrane is manufactured.

U.S. Patent 5,576,057, invented by Hirose et al., Shows a method for improving the flow rate to 24 gfd in desalination process by adding 10-50 wt% alcohol to an amine solution similar to U.S. Patent 4,872,984. U.S. Patent 5,614,099 also proposes a method of using various organic solvents containing alcohol, ether, ethylene glycol derivatives, ketones, and sulfur as additives. For example, by adding 20% by weight alcohol to an amine solution containing an amine salt, it was announced that the flow rate exceeded 40 gfd under brackish water treatment conditions. The improved flow rate of the membrane produced by this example is explained by the increase in roughness of the epidermal layer. In addition, the reverse osmosis composite membrane prepared by the method of drying at 120 ° C. by adding 10-20% by weight of alcohol and 6% by weight of amine salt showed high flow rate, but it was not satisfactory and required to develop a more economical method. It is done.

It is an object of the present invention to provide a reverse osmosis membrane with improved performance compared to the above-described methods, and is particularly intended to produce a semipermeable reverse osmosis membrane having a high flow rate and excellent salt rejection useful for brackish water and seawater treatment. .

The present invention is a polyfunctional amine aqueous solution containing 0.1 to 20% by weight of at least one water-soluble polyfunctional amine selected from the group consisting of polysulfone, polyethersulfone, polyimide, polyamide, polypropylene and polyvinylidene difluoride. 0.005-5% by weight of any one amine-reactive compound selected from the group consisting of a polyfunctional acyl halide, a polyfunctional sulfonyl halide and a polyfunctional isocyanate, coated on either porous support layer, and removing excess solution A solution in which 0.01 to 1% by weight of chloride is dissolved together in an organic solvent is prepared, and the solution prepared above is brought into contact with the surface of the support layer by dipping or spraying for 5 seconds to 10 minutes to form an interfacial polymerization reaction to form a film. And washing the formed membrane with a basic aqueous solution. It provides a method of making the amount of the reverse osmosis membrane. More specifically, phosphinylmethyl alkyl chloride to a chloride there was obtained: 3-Chloro-phenyl phosphinylmethyl propionyl represented by the general formula (1), it is more preferable to add 0.01 to 0.2% by weight. In addition, the organic solvent is selected from the group consisting of hexane, cyclohexane, heptane, halogenated hydrocarbons containing alkanes having 8 to 12 carbon atoms and freon.

Hereinafter, the present invention will be described in detail.

The microporous support layer used in the present invention uses a material having a pore size of approximately 1 to 500 nm. When the support layer having a pore size of 500 nm or more is used, the film of the surface layer obtained by interfacial polymerization penetrates between the pore diameters of the support layer, thereby preventing the formation of a normal flat film. Currently used as such a microporous support layer are halogenated polymers such as polysulfone, polyethersulfone, polyimide, polyamide, polypropylene and polyvinylidene difluoride.

Aqueous polyfunctional amine solutions include cyclic polyfunctional amines, metaphenylenediamines, such as alkane diamines, cyclohexanediamines, piperazine and piperazine derivatives, with or without N-alkyl or aryl derivatives such as 1,3-propanediamine, Dilution is carried out by preparation of aromatic polyfunctional amines such as paraphenylenediamine and derivatives thereof by hand coating or continuous mechanical coating on a porous support layer. Derivatives here include alkyl groups such as methyl, ethyl, alkoxy groups such as methoxy, ethoxy, hydroxy alkyl groups, hydroxy groups, halogen atoms and the like. Other usable polyfunctional amines include N, N-dimethyl-1,3-phenylenediamine, xylenediamine, benzidine, benzidine derivatives and mixtures thereof. Currently, polyfunctional amines widely used include metaphenylenediamine having two aromatic primary amines. The aqueous polyfunctional amine solution preferably contains 0.1 to 20% by weight (preferably 0.5 to 8% by weight) of the polyfunctional amine, and the pH of the aqueous polyfunctional amine solution is 0.001 to 5% of the acid acceptor material. It can be adjusted by adding degree. Alkali metal hydroxides, alkali metal carboxylates, alkali metal carbonates, alkali metal phosphates and tertiary amines are widely used as such acid acceptor materials.

In the present invention, after removing the excess solution on the surface of the porous support layer coated with the polyfunctional amine solution, and the interface with the organic solution containing an amine-reactive compound such as polyfunctional acyl halide polyfunctional sulfonyl halide, polyfunctional isocyanate and phosphinyl alkyl chloride Let reaction. The contact with the organic solution is generally performed by dipping or spraying for about 5 seconds to 10 minutes, and sufficient reaction proceeds in about 20 seconds to 4 minutes.

The polyfunctional acyl halides used in the interfacial polymerization reaction are aromatic compounds having 2 to 3 carboxylic acid halides, and trimezoyl chloride, isophthaloyl chloride, terephthaloyl chloride and mixtures thereof are widely used. The content in the organic solvent is preferably in the range of 0.005 to 5% by weight.

The organic solvent used in the present invention has a property of not being mixed with water, and hexane, cyclohexane, heptane, halogenated hydrocarbons such as alkenes having 8 to 12 carbon atoms and freon are mainly used, and especially mixed solutions of alkanes having 8 to 12 carbon atoms. Suitable for this is the ISOPAR solvent commercialized as a mixture of this kind.

Meanwhile, in the present invention, a phosphinylalkyl chloride compound is added in the range of 0.01 to 1% by weight together with the amine reactive compound as described above. For example, benzene phosphorus dichloride (BPO) and acrylic acid ( By adding 3-phenylchlorophosphinyl propionyl chloride synthesized in AA), the effect of improving the flow rate was improved from 15-18 gfd to 25-40 gfd in the brackish test condition.

The phosphinyl alkyl chloride compound is a polyfunctional acyl compound having a specific structure having an alkyl group and an acyl halide in phosphorus. The phosphinyl alkyl chloride compound has a functional group similar to the known trimezoyl chloride and isophthaloyl chloride, but there are structural differences, that is, Aromatic polyfunctional acyl compounds, such as trimezoyl chloride and isophthaloyl chloride, have a certain symmetry in polymer formation, but the compound has a functional group but a change in symmetry, so that one side has a rigid structure and the other side has fluidity. By having a structure, it can be interpreted that it has a fluidity | liquidity and unity, compared with the compound which consists only of an aromatic polyfunctional acyl compound, and plays a role which densifies a fine surface structure.

The reverse osmosis membrane obtained by the interfacial polymerization as described above is finally subjected to a step of washing for 5 seconds or more with a basic aqueous solution of pH 7-14.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

<Example 1>

93.6 g of acrylic acid was placed in a 1 L round flask, and the temperature was raised to 70 ° C., and the vessel was placed in a nitrogen atmosphere, and 179 g of phosphorus dichloride was slowly added to the vessel for 1 hour, followed by stirring to be sufficiently mixed. At this time, since the exothermic reaction was severe, the temperature was adjusted to 80 ± 5 ° C., and when the addition was completed, the temperature was maintained at 90 ° C. and stirred for 2 hours. The pale yellow liquid thus obtained was distilled under reduced pressure at 1 torr and 160 ° C. to obtain 3-phenylchlorophosphinyl propionyl chloride (Compound 1).

A 2 wt% aqueous solution of metaphenylenediamine was immersed for 40 seconds on a 140 μm-thick microporous support layer made by applying polysulfone to a nonwoven fabric, and then the excess amine solution was removed from the support layer. EXXON Co., Ltd.) was immersed in an organic solution in which 0.09% by weight of trimezoyl chloride and 0.01% by weight of Compound 1 were dissolved for 1 minute, and excess organic solvent was poured out. The reverse osmosis composite membrane thus obtained was washed with sodium carbonate solution at 40 ° C. to 60 ° C. and washed again with water to measure physical properties. In this case, the physical properties of the reverse osmosis membrane was measured by passing the membrane at 225 PSI aqueous sodium chloride solution of 2000 PPM.

<Example 2-15>

Except for changing the type and the amount of the polyfunctional acyl halide and compound 1 dissolved in the isowave solvent in Example 1 as shown in Table 1 was carried out in the same manner as in Example 1.

<Comparative Example 1-3>

Except for using the compound 1 in Example 1 and changing the type and amount of acyl halide as shown in Table 1 and was carried out in the same manner as in Example 1.

Acyl halides Concentration (% by weight) Flow rate (GFD) Salt removal rate (%) Example 1 Trimesoylchloride / Compound 1 0.09 / 0.01 27.5 98.2 Example 1 Trimesoylchloride / Compound 1 0.05 / 0.05 31.0 96.8 Example 1 Trimesoylchloride / Compound 1 0.1 / 0.1 40.2 89.1 Comparative Example 1 Isoftharoyl chloride 0.1 14.4 98.7 Example 4 Isophthaloylchloride / Compound 1 0.09 / 0.01 22.0 98.1 Example 5 Isophthaloylchloride / Compound 1 0.07 / 0.03 26.4 95.4 Example 6 Isophthaloylchloride / Compound 1 0.05 / 0.05 28.7 92.9 Example 7 Isophthaloylchloride / Compound 1 0.1 / 0.1 36.7 88.4 Comparative Example 2 Trimesoyl chloride / isophtharoyl chloride 0.05 / 0.05 16.1 98.5 Example 8 Trimesoylchloride / Isophthaloylchloride / Compound 1 0.05 / 0.05 / 0.01 20.1 97.5 Example 9 Trimesoylchloride / Isophthaloylchloride / Compound 1 0.05 / 0.05 / 0.03 23.3 94.4 Example 10 Trimesoylchloride / Isophthaloylchloride / Compound 1 0.05 / 0.05 / 0.05 29.3 92.6 Example 11 Trimesoylchloride / Isophthaloylchloride / Compound 1 0.05 / 0.05 / 0.1 34.3 85.0 Comparative Example 3 Trimesoyl chloride / terephthaloyl chloride 0.05 / 0.05 20.1 94.5 Example 12 Trimesoylchloride / terephthaloylchloride / Compound 1 0.05 / 0.05 / 0.01 24.1 94.1 Example 13 Trimesoylchloride / terephthaloylchloride / Compound 1 0.05 / 0.05 / 0.03 29.3 91.9 Example 14 Trimesoylchloride / terephthaloylchloride / Compound 1 0.05 / 0.05 / 0.05 33.3 84.4 Example 15 Trimesoylchloride / terephthaloylchloride / Compound 1 0.05 / 0.05 / 0.1 40.3 80.1

In Table 1, the reverse osmosis membrane prepared by using only aromatic diacyl or triacyl halides has a high salt removal rate in the case of comparative examples of general reverse osmosis membranes. Show that having This phenomenon is believed to be the result of copolymerization between aromatic diacyl or triacyl halides, which are highly reactive with the flexibility of alkyl halides and the stericity of phosphinyl halides. In the case of industrial reverse osmosis membranes can be put to practical use only to show the salt removal rate of 98% or more, the domestic reverse osmosis membrane is a trend that wants to high flow rate than the salt removal rate, the present invention is very useful in the region of the reverse osmosis membrane desired 90% moderate salt removal rate.

Claims (3)

The aqueous polyfunctional amine solution containing 0.1 to 20% by weight of one or more water-soluble polyfunctional amines is any one selected from the group consisting of polysulfone, polyethersulfone, polyimide, polyamide, polypropylene and polyvinylidene difluoride. Coating on the porous support layer and removing excess solution, A solution in which 0.005 to 5% by weight of an amine-reactive compound selected from the group consisting of polyfunctional acyl halides, polyfunctional sulfonyl halides and polyfunctional isocyanates and 0.01 to 1% by weight of phosphinyl alkyl chloride are dissolved in an organic solvent together. Manufacturing, The solution prepared above is brought into contact with the surface of the support layer for 5 seconds to 10 minutes by dipping or spraying to form an interfacial polymerization reaction to form a film. Method for producing a high flow rate reverse osmosis membrane, characterized in that the membrane is prepared by washing with a basic aqueous solution. The method of claim 1, wherein the phosphinyl alkyl chloride is 3-phenylchlorophosphinyl propionyl chloride represented by the following Chemical Formula 1, and 0.01 to 0.2% by weight is added. Formula 1 The method of claim 1, wherein the organic solvent is selected from the group consisting of hexane, cyclohexane, heptane, a halogenated hydrocarbon containing 8 to 12 carbon atoms and a freon.