A method for preparing a polyamide composite membrane containing hyperbranched polyamide

Abstract

The present invention relates to a method for preparing a polyamide composite membrane, and in particular to a method for preparing a polyamide composite membrane containing hyperbranched polyamide. Specifically, the present invention proposes a method for preparing a polyamide composite membrane containing amino-terminated hyperbranched polyamide, by preparing a support body by phase conversion of amino-terminated hyperbranched polyamide and sulfonated polymer, modifying the surface of the support body by a modified solution of polyacid chloride, and then performing interfacial polymerization again to form a polyamide composite membrane.

Description

Technical Field

[0001] The invention relates to a method for preparing a polyamide composite membrane, in particular to a method for preparing a polyamide composite membrane containing hyperbranched polyamide. Background Art

[0002] Polyamide composite membrane is a common type of membrane material in water treatment membranes, and has been widely used in nanofiltration, reverse osmosis, forward osmosis and other sub-fields. Therefore, the preparation of polyamide composite membranes has always been a hot topic for researchers.

[0003] Polyamide composite membranes generally include a polyamide separation layer and a support layer. For polyamide composite membranes, the interception rate, water flux and stability are the most critical characterization data. Among them, in order to improve the water flux, researchers have tried to add hydrophilic or macroporous structure substances to the polyamide separation layer or the support layer, and to improve the stability, researchers have tried to add substances containing amino, carboxyl and other groups to the support layer to increase the binding force between the support layer and the separation layer. However, there are compatibility issues between external additives and the separation layer / support layer.

[0004] Hyperbranched polyamide is a substance with a cavity structure. Its addition to the sulfonated polymer support can be expected to increase the water flux of the membrane and improve the stability of the membrane. However, the inventors found in the early test process that the surface of the support prepared after the two were blended was rough, and it was difficult to form a polyamide composite membrane with a dense separation layer. Therefore, it is necessary to optimize the above method to achieve the optimization of the support by hyperbranched polyamide. Summary of the invention

[0005] In view of the above problems, the present invention proposes a method for preparing a polyamide composite membrane containing terminal amino group hyperbranched polyamide, by preparing a support body by phase conversion of terminal amino group hyperbranched polyamide and sulfonated polymer, and modifying the surface of the support body by a modified solution of polyacyl chloride, followed by interfacial polymerization again to form a polyamide composite membrane.

[0006] Specifically, the present invention provides a method for preparing a polyamide composite membrane containing hyperbranched polyamide, comprising the following steps:

[0007] (1) dissolving the amino-terminated hyperbranched polyamide and the sulfonated polymer in an organic solvent in a mass ratio of 1:1-3, stirring continuously for 12-48 hours under heating conditions, and then standing to degas to form a support blend casting solution;

[0008] (2) taking the above-mentioned support body mixed casting liquid, scraping it on a glass plate to form a film, and then phase-converting it in a coagulation bath and drying it to form a support body;

[0009] (3) immersing the support in a modification solution containing polyacyl chloride to modify the surface of the support, and drying;

[0010] (4) The surface-modified support is immersed in an aqueous solution containing polyamine, the surface liquid is removed and the support is dried in the shade, and the support is further immersed in an oil solution containing polyacyl chloride, the support is removed and dried to obtain a polyamide composite membrane.

[0011] Preferably, the sulfonated polymer is one of sulfonated polysulfone or sulfonated polyethersulfone.

[0012] Preferably, the organic solvent is one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0013] Preferably, the heating temperature is 50-80°C.

[0014] Preferably, the mass concentration of the amino-terminated hyperbranched polyamide and the sulfonated polymer mixture in the support blend casting solution is 7-20wt%.

[0015] Preferably, the casting solution further comprises 0.5-8wt% of a pore former, wherein the pore former is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol and lithium chloride.

[0016] Preferably, the coagulation bath is deionized water or ethanol, or a mixture of the two in any proportion.

[0017] Preferably, the polyacyl chlorides in the modified solution and the oil phase solution are independently selected from one of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride and isophthaloyl chloride, wherein the concentration of the polyacyl chloride in the modified solution is 0.001-0.5wt%, and the concentration of the polyacyl chloride in the oil phase solution is 0.01-5wt%.

[0018] Preferably, the polyamine solution is selected from one of piperazine, ethylenediamine, propylenediamine, hexylenediamine, triethylamine, diethylenetriamine, diethylenediamine, m-phenylenediamine and p-phenylenediamine, and its concentration is 0.01-10wt%.

[0019] The present invention also provides a polyamide composite membrane prepared by the method, wherein the support of the polyamide composite membrane is prepared by blending amino-terminated hyperbranched polyamide and sulfonated polymer.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] Firstly, the present invention prepares a support by blending terminal amino hyperbranched polyamide with a sulfonated polymer. The cavity structure of the hyperbranched polyamide provides a transmission channel for water molecules, thereby increasing the water flux of the membrane.

[0022] Secondly, in order to solve the problem of rough surface of the support prepared by blending hyperbranched polyamide and sulfonated polymer, the present invention adopts simple polyacyl chloride for modification, and the polyacyl chloride and the amino group of the hyperbranched polyamide on the surface of the support undergo one interfacial polymerization to modify the defects on the surface of the support.

[0023] In addition, the present invention performs interfacial polymerization again on the surface of the modified support, and the acyl chloride on the surface of the modified layer reacts with the amino group in the aqueous solution, thereby improving the bonding strength between the support, the modified layer and the polyamide separation layer. Moreover, the terminal amino group of the hyperbranched polyamide forms an intermolecular hydrogen bond with the sulfonic acid group of the sulfonated polymer, thereby improving the compatibility between the two. DETAILED DESCRIPTION

[0024] Example 1

[0025] Example 1 The polyamide composite membrane is prepared by the following steps:

[0026] The amino-terminated hyperbranched polyamide and sulfonated polyether sulfone are dissolved in dimethyl sulfoxide in a mass ratio of 1:2.5, and the mass concentration of the amino-terminated hyperbranched polyamide and sulfonated polymer mixture is 15wt%, and then 2wt% of lithium chloride is added as a pore-forming agent, and the mixture is continuously stirred for 24 hours under heating conditions of 65°C, and then allowed to stand for degassing to form a support blended casting liquid; then the support blended casting liquid is scraped onto a glass plate to form a film, and then phase-converted in a pure water coagulation bath and air-dried at room temperature to form a support; the support is immersed in a n-hexane solution containing 0.25wt% of isophthaloyl chloride for 10s, and dried at 60°C; finally, the support is immersed in an aqueous solution containing 5wt% of m-phenylenediamine for 120s, and the surface liquid is removed and dried in the shade after being taken out, and the support is further immersed in a n-hexane solution containing 2wt% of trimesoyl chloride for 20s, and then taken out and dried to obtain a polyamide composite membrane.

[0027] Example 2

[0028] Example 2 The polyamide composite membrane is prepared by the following steps:

[0029] The amino-terminated hyperbranched polyamide and sulfonated polyether sulfone are dissolved in dimethyl sulfoxide in a mass ratio of 1:1, and the mass concentration of the amino-terminated hyperbranched polyamide and sulfonated polymer mixture is 15wt%, and then 2wt% of lithium chloride is added as a pore-forming agent, and the mixture is continuously stirred for 24 hours under heating conditions of 65°C, and then allowed to stand for degassing to form a support body blended casting liquid; then the above-mentioned support body blended casting liquid is scraped onto a glass plate to form a film, and then phase-converted in a pure water coagulation bath and air-dried at room temperature to form a support body; the support body is immersed in a n-hexane solution containing 0.25wt% of isophthaloyl chloride for 10s, and dried at 60°C; finally, the support body is immersed in an aqueous solution containing 5wt% of m-phenylenediamine for 120s, and the surface liquid is removed and dried in the shade after being taken out, and the support body is further immersed in a n-hexane solution containing 2wt% of trimesoyl chloride for 20s, and then taken out and dried to obtain a polyamide composite membrane.

[0030] Comparative Example 1

[0031] Comparative Example 1 The polyamide composite membrane was prepared by the following steps:

[0032] 15wt% of sulfonated polyethersulfone and 2wt% of lithium chloride are dissolved in dimethyl sulfoxide, stirred for 24 hours, and then allowed to stand for degassing to form a support blended casting liquid; the support blended casting liquid is then scraped onto a glass plate to form a film, and then phase-converted in a pure water coagulation bath and air-dried at room temperature to form a support; the support is immersed in an aqueous solution containing 5wt% of m-phenylenediamine for 120s, the surface liquid is removed and dried in the shade after being taken out, and the support is further immersed in a n-hexane solution containing 2wt% of trimesoyl chloride for 20s, and the support is dried after being taken out to obtain a polyamide composite membrane.

[0033] Comparative Example 2

[0034] Comparative Example 2 The polyamide composite membrane was prepared by the following steps:

[0035] The amino-terminated hyperbranched polyamide and sulfonated polyether sulfone are dissolved in dimethyl sulfoxide in a mass ratio of 1:2.5, and the mass concentration of the amino-terminated hyperbranched polyamide and the sulfonated polymer mixture is 15wt%, and then 2wt% of lithium chloride is added as a pore-forming agent, and the mixture is continuously stirred for 24 hours under heating conditions of 65°C, and then allowed to stand for degassing to form a support blended casting liquid; then the support blended casting liquid is scraped onto a glass plate to form a film, and then phase-converted in a pure water coagulation bath and air-dried at room temperature to form a support; finally, the support is immersed in an aqueous solution containing 5wt% of m-phenylenediamine for 120s, and the surface liquid is removed and dried in the shade after being taken out, and the support is further immersed in a n-hexane solution containing 2wt% of trimesoyl chloride for 20s, and then taken out and dried to obtain a polyamide composite membrane.

[0036] The polyamide composite membranes of Example 1-2 and Comparative Example 1-2 were tested for separation performance at 25°C, 2000 mg / L sodium chloride as the raw material liquid, and 1.50 MPa operating pressure; then the membranes were taken out, reversely installed, and operated at 3.8 MPa reverse pressure for 2 hours, and then forwardly installed again to test their separation performance. The results are shown in Table 1:

[0037] Table 1 Separation performance of composite membrane samples of different embodiments and comparative examples

[0038] From the results in Table 1, it can be seen that the polyamide composite membrane prepared by the method of the present invention maintains a high level of initial salt rejection and initial flux, and still maintains a high separation performance after back pressure, thereby proving that the polyamide separation layer of the present invention has a high bonding force with the support.

[0039] Those skilled in the art will appreciate that, based on the teachings of this specification, some modifications or adjustments may be made to the present invention, and these modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a polyamide composite membrane containing amino-terminated hyperbranched polyamide, comprising the following steps: (1) dissolving the amino-terminated hyperbranched polyamide and the sulfonated polymer in an organic solvent in a mass ratio of 1:1-3, stirring continuously for 12-48 hours under heating conditions, and then standing to degas to form a support blend casting solution; (2) taking the above-mentioned support body mixed casting liquid, scraping it on a glass plate to form a film, and then phase-converting it in a coagulation bath and drying it to form a support body; (3) immersing the support in a modification solution containing polyacyl chloride to modify the surface of the support, and drying; (4) soaking the surface-modified support in an aqueous solution containing a polyamine, removing the surface liquid and drying in the shade, and then soaking the support in an oil solution containing a polyacyl chloride, taking it out and drying it to obtain a polyamide composite membrane; the sulfonated polymer is one of sulfonated polysulfone or sulfonated polyethersulfone.

2. The method according to claim 1, characterized in that The organic solvent is one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

3. The method according to claim 1, characterized in that The heating temperature in step (1) is 50-80°C.

4. The method according to claim 1, characterized in that The mass concentration of the amino-terminated hyperbranched polyamide and the sulfonated polymer mixture in the support blended casting solution is 7-20wt%.

5. The method according to claim 1, characterized in that The casting solution also includes 0.5-8wt% of a pore-forming agent, which is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, and lithium chloride.

6. The method according to claim 1, characterized in that The coagulation bath is deionized water or ethanol, or a mixture of the two in any proportion.

7. The method according to claim 1, characterized in that The polyacyl chlorides in the modified solution and the oil phase solution are independently selected from one of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride and isophthaloyl chloride, wherein the concentration of the polyacyl chloride in the modified solution is 0.001-0.5wt%, and the concentration of the polyacyl chloride in the oil phase solution is 0.01-5wt%.

8. The method according to claim 1, characterized in that The polyamine is selected from one of piperazine, ethylenediamine, propylenediamine, hexamethylenediamine, triethylamine, diethylenetriamine, diethylenediamine, meta-phenylenediamine and para-phenylenediamine, and its concentration in the aqueous phase solution containing the polyamine is 0.01-10wt%.

9. A polyamide composite membrane containing hyperbranched polyamide prepared according to any one of claims 1 to 8, characterized in that The support of the polyamide composite membrane is prepared by blending amino-terminated hyperbranched polyamide and sulfonated polymer.

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