Method and reaction device for preparing composite membrane by interfacial polymerization

Abstract

The present invention belongs to the field of film production, and specifically relates to a method for preparing a composite membrane by interfacial polymerization reaction. The method comprises first vertically fixing a support body in a reaction vessel having a liquid cavity, wherein the support body divides the cavity of the reaction vessel into two parts. An aqueous phase and an organic phase are added to the two cavities respectively, and the mixture is allowed to stand for a while. After the two phases react and form a polymer film layer on the surface of the support body, the reaction is terminated. The support body with the polymer film layer attached is the composite membrane. The solvents of the aqueous phase and the organic phase are mutually immiscible, and the solutes in the two phases react with each other to form a polymer layer. The present invention also relates to a reaction device for preparing a composite membrane by using the above-mentioned interfacial polymerization reaction method, comprising a container and a clamping mechanism. The clamping mechanism vertically fixes the support body in the container and divides the cavity of the container into left and right parts, each of which is provided with a feed port.

Description

Technical Field

[0001] The invention belongs to the field of film making, and particularly relates to a method for preparing a composite film by interfacial polymerization reaction and a reaction device. Background Art

[0002] Interfacial polymerization is a condensation reaction that occurs at the interface (or on the organic phase side of the interface) between two immiscible solutions containing two different monomers. The resulting polymer is insoluble in the solvent and precipitates at the interface. With the development of composite membrane technology, interfacial polymerization has gradually been applied to the preparation of composite membranes. This involves using a microporous membrane or ultrafiltration membrane as a support layer, and utilizing interfacial polymerization to coat the support layer with a dense, homogeneous membrane as a separation layer. This results in a membrane with exceptional separation properties.

[0003] The article "Interfacial Polymerization" (Tang Beibei et al., Progress in Chemistry, Vol. 19, No. 9, September 2007) describes a method for preparing composite nanofiltration membranes using interfacial polymerization reactions. It uses two highly reactive monomers to undergo a polymerization reaction at the interface of two immiscible solvents, thereby forming a very thin dense layer on a porous support (microfiltration or ultrafiltration membrane). Specifically, the support is first immersed in an aqueous solution containing an active monomer to fully soak it, then the excess solution is drained out, and the membrane is immersed in an organic (oil) phase containing another active monomer. The two active monomers react with each other on the surface of the support to form a dense polymer cortex, which greatly improves the permeability and selectivity of the composite membrane. The key to this method is to select reactive monomers with appropriate distribution coefficients and set an appropriate diffusion rate to obtain the ideal membrane surface density. However, this method of first soaking in the aqueous phase and then soaking in the organic phase requires a high reaction rate of the two monomers. The applicant's actual operation verification shows that not only is the process cumbersome, requiring soaking in the aqueous phase first and then soaking in the organic phase, but the reaction process is extremely difficult to control, and the film can be formed in only about 30 seconds. In particular, the polymer membrane layer is an amorphous, dense polyamide membrane layer without a regular pore structure, which is far from meeting the requirements for the permeability and selectivity of the composite membrane.

[0004] The English literature Can Li, Shuxuan Li, Long Tian, ​​Jinmiao Zhang, Baowei Su, Michael Z. Hu, Covalent organic frameworks (COFs)-incorporated thin film nanocomposite (TFN) membranes for high-flux organic solvent nanofiltration (OSN). J. Membr. Sci 572 (2019) 520-531. describes a method for preparing a COFs membrane layer using interfacial polymerization. The COFs membrane layer is an ordered porous organic covalent polymer membrane layer, which is first hydrothermally synthesized, then ultrasonically exfoliated into nanosheets, and finally vacuum filtered to form a membrane. The prepared membrane layer does achieve an ordered porous structure, and the membrane permeability and selectivity are both improved. However, its preparation method requires high temperature and high pressure to achieve, and the equipment and reaction conditions are relatively difficult to achieve.

[0005] Therefore, in order to adapt to the application and development of interfacial polymerization reaction in the preparation of COFs composite membranes, it is imperative to find simple and easy-to-implement methods and equipment for preparing COFs composite membranes by interfacial polymerization reaction. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a composite membrane by interfacial polymerization reaction, which can greatly simplify the reaction operation process and reduce the requirements for reaction conditions.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for preparing a composite membrane by interfacial polymerization reaction, firstly, a support body is vertically fixed in a reaction vessel having a liquid cavity, and the support body divides the cavity of the reaction vessel into two parts, and an aqueous phase and an organic phase are added to the two cavities respectively. After standing, after the two phases react and a polymer film layer is formed on the surface of the support body, the reaction is terminated, and the support body with an attached polymer film layer is a composite membrane; the solvents of the aqueous phase and the organic phase are immiscible with each other and the solutes in the two phases react with each other to form a polymer layer.

[0008] Wherein, the support is a microfiltration membrane or an ultrafiltration membrane.

[0009] The above-mentioned scheme for preparing COFs (Covalent organic frameworks) composite membranes is adopted, and the two-phase solutions are placed on both sides of the support respectively. This can not only ensure that there is sufficient supply of active monomers at the interface between the two phases and the thickness of the formed membrane layer is controllable, but also has no stringent requirements on the reaction conditions, and can be met under normal temperature and pressure. This greatly simplifies the steps of preparing composite membranes by interfacial polymerization reaction, and also reduces the requirements for equipment, with lower investment costs and greater safety. The polymer film layer formed on the support is uniform and continuous, which greatly improves the selectivity of the composite membrane.

[0010] Preferably, the aqueous phase includes water, monomers and catalysts, the monomers are diamine compounds, and the catalysts are monobasic organic acid compounds; the organic phase includes solvents and solutes, the solvent is one or more of n-hexane, heptane, octane, and nonane, and the solute is trimesic acid and / or trialdehyde phloroglucinol. When the two-phase solution undergoes interfacial polymerization, the reaction rate is slow and the degree of reaction is controllable. The time to terminate the reaction can be determined based on the thickness of the polymer film layer. Preferably, the reaction time is 0 to 72 hours, and the polymer film layer thickness is generally about 100 nm. The longer the reaction time, the thickness of the generated polymer film layer will gradually increase, and as the film layer is formed, the amount of monomers in the two phases that pass through the film layer to react will decrease, so the growth rate of the film layer thickness will slow down as the reaction time increases.

[0011] The concentration of the diamine compound in the aqueous phase is 0.005-0.1 mol / L, and the concentration of the monobasic organic acid compound is 0.01-0.5 mol / L; the concentration of the organic phase is 0.0001-0.01 mol / L, the liquid levels of the two phases are the same, and the concentration of the aqueous phase is greater than that of the organic phase.

[0012] The same liquid level can maintain the same pressure in the two chambers. When the concentration of the aqueous phase is slightly higher, the aqueous phase will penetrate the support, and the interface between the two phases will be on the organic phase side of the support. When the aqueous phase and the organic phase are added at the same time, or the aqueous phase is added first and then the organic phase is added quickly, the monomers in the two phases undergo polymerization and the resulting film layer will adhere to the surface of the organic phase side of the support. Of course, the greater the concentration of the two-phase solution, the faster the film layer will form. To ensure the formation of a uniform and continuous interfacial polymer separation layer, the concentration of the two phases should not be too high, that is, the speed of the reaction to form the polymer film layer should not be too fast.

[0013] Another object of the present invention is to provide a reaction device for preparing a composite membrane by adopting the above-mentioned interfacial polymerization reaction, which has a simple structure, is easy to operate, and has low requirements on manufacturing materials.

[0014] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a reaction device for preparing a composite membrane method using the above-mentioned interfacial polymerization reaction, including a container and a clamping mechanism, wherein the clamping mechanism vertically fixes the support body in the container and divides the container cavity into two left and right parts, and the two parts of the cavity are respectively provided with a feeding port.

[0015] Wherein, the support is a microfiltration membrane or an ultrafiltration membrane.

[0016] By using the above-mentioned interfacial polymerization reaction device, the support body divides the container cavity into two parts, and the aqueous phase and the organic phase are added to the two parts of the cavity respectively. This ensures that the solutions on both sides of the support body can supply active monomers for polymerization reaction at any time, and the support body is fixed at the interface between the two phases. The formed film layer and the support body are highly reliable, and the reaction device has a simple structure and low cost investment.

[0017] As a preferred embodiment, the container 10 is composed of two halves 11 and 12 of identical radial dimensions, which are clamped and connected by a clamping mechanism 20. The support body A is sandwiched between the two halves 11 and 12. This two-half design facilitates loading and unloading of the support body, and the identical radial dimensions of the two halves ensure hydraulic stability on both sides of the support body A.

[0018] The two halves 11, 12 are provided with outer flanges 40 where they abut against the container wall of the support body A. The clamping mechanism 20 is clamped onto the outer flanges 40 of the two halves 11, 12. The outer flanges 40 of the two halves can firmly clamp the outer edge of the support body A between them, and the clamping mechanism 20 clamps onto the outer flanges to ensure a sealing effect at the edge of the support body.

[0019] The two halves 11 and 12 are barrel-shaped, with their openings facing each other. A feed port 30 is provided on the barrel wall. Naturally, the two barrel halves have the same barrel diameter and the same radial dimensions of their outer flanges. During use, the outer flanges of the two halves are aligned, and a support is clamped between the openings. The aqueous phase and the organic phase can then be added to each of the halves for interfacial polymerization.

[0020] The container 10 is made of a corrosion-resistant transparent material, such as quartz, so that it is easy to observe the film formation on the support and to terminate the reaction at any time as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the interfacial polymerization reaction device of the present invention.

[0022] In the figure: 10 - container, 11, 12 - container halves, 20 - clamping mechanism, 30 - feeding port, 40 - outer flange, A - support DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1

[0025] The interfacial polymerization reaction device of the present invention is used to prepare a composite membrane. The support A is a polyacrylonitrile ultrafiltration membrane. The support A is cut into a shape with the same size as the outer flanges of the two halves of the reaction device. The reaction device is assembled and used for standby use.

[0026] Prepare the solution: the aqueous phase is an aqueous solution with a concentration of 0.0225 mol / L of p-phenylenediamine and a concentration of 0.0675 mol / L of p-toluenesulfonic acid, and the organic phase is an n-hexane solution with a concentration of 0.0075 mol / L of trialdehyde phloroglucinol.

[0027] The two-phase solution was added to the cavities on both sides of the support A as simultaneously as possible, and the liquid levels on both sides were kept consistent. A polymer film layer was gradually formed on the organic phase solution side of the support A. After 24 hours of reaction, the reaction was terminated, and the solutions on both sides were poured out at the same time. The support A was removed to obtain the prepared composite membrane, one side of which was attached with a polymer film layer with a thickness of 70 nm. The composite membrane was used to filter a Congo red-ethanol solution with a concentration of 0.01 mol / L, and the volume of the solution passing through within a certain period of time was measured. The concentration of the Congo red-ethanol solution before and after filtration was measured using an ultraviolet spectrophotometer. The permeability and retention rate of the composite membrane for Congo red were calculated and recorded in Table 1.

[0028] Example 2

[0029] The composite membrane was prepared by the same method as in Example 1, wherein the aqueous phase was an aqueous solution with a concentration of 0.05 mol / L of diphenyl diamine and a concentration of 0.15 mol / L of p-toluenesulfonic acid, the organic phase was an n-hexane solution with a concentration of 0.016 mol / L of trialdehyde phloroglucinol, the reaction time was 6 hours, and the thickness of the obtained composite membrane polymer layer was 50 nm.

[0030] The obtained composite film was tested using the same method as in Example 1, and the test results are recorded in Table 1.

[0031] Example 3

[0032] The composite membrane was prepared by the same method as in Example 1. The aqueous phase was an aqueous solution with a benzyl diamine concentration of 0.04 mol / L and a p-toluenesulfonic acid concentration of 0.12 mol / L, and the organic phase was an n-hexane solution with a trialdehyde phloroglucinol concentration of 0.011 mol / L. The reaction time was 4 hours, and the thickness of the resulting composite membrane polymer layer was 30 nm.

[0033] The obtained composite film was tested using the same method as in Example 1, and the test results are recorded in Table 1.

[0034] Table 1 Test results of composite films obtained in Examples 1-3

[0035] <![CDATA[Coefficient of permeability (L / m 2 ·h·bar)]]> Retention rate (%) Example 1 75.8 99.5 Example 2 88.4 99.6 Example 3 95.6 99.5

[0036] It can be seen from the data in Table 1 that the COFs composite membrane prepared by the solution of the present invention has a greatly improved rejection rate of the filtrate.

Claims

1. A method for preparing a composite membrane by interfacial polymerization, characterized in that: First, the support body is vertically fixed in a reaction container with a liquid cavity, and the support body divides the cavity of the reaction container into two parts. The aqueous phase and the organic phase are added to the two cavities respectively, and the mixture is allowed to stand. After the two phases react and a polymer film layer is formed on the surface of the support body, the reaction is terminated. The support body with an attached polymer film layer is a composite membrane; the solvents of the aqueous phase and the organic phase are immiscible with each other, and the solutes in the two phases react with each other to form a polymer layer.

2. The method for preparing a composite membrane by interfacial polymerization according to claim 1, wherein: The aqueous phase includes water, monomers and catalysts, wherein the monomers are diamine compounds and the catalysts are monobasic organic acid compounds; the organic phase includes solvents and solutes, wherein the solvents are one or more of n-hexane, heptane, octane and nonane, and the solutes are trimesaldehyde and / or trialdehyde phloroglucinol.

3. The method for preparing a composite membrane according to claim 2, wherein: The concentration of the diamine compound in the aqueous phase is 0.005-0.1 mol / L, and the concentration of the monobasic organic acid compound is 0.01-0.5 mol / L; the concentration of the organic phase is 0.0001-0.01 mol / L, and the concentration of the aqueous phase is greater than that of the organic phase.

4. The method for preparing a composite membrane according to claim 1, wherein: The aqueous phase and the organic phase are added at the same time, or the aqueous phase is added first and then the organic phase is added quickly.

5. The method for preparing a composite membrane according to claim 1, wherein: The reaction time is 0 to 72 hours.

6. The method for preparing a composite membrane according to any one of claims 1 to 5, characterized in that: The process of preparing a composite membrane utilizes the following interfacial polymerization reaction device: comprising a container (10), wherein the container (10) is provided with a clamping mechanism (20) for vertically fixing a support body (A) in a cavity, wherein the vertical support body (A) divides the cavity of the container (10) into two parts, a left part and a right part, and both parts of the cavity are provided with a feeding port (30).

7. The method for preparing a composite membrane according to claim 6, wherein: The container (10) is composed of two halves (11, 12) having the same radial dimensions, which are clamped and connected by a clamping mechanism (20), and the support body (A) is clamped between the two halves (11, 12).

8. The method for preparing a composite membrane according to claim 7, wherein: The two halves (11, 12) are provided with outer flanges (40) at the container wall close to the support body (A), and the clamping mechanism (20) is clamped on the outer flanges (40) of the two halves (11, 12).

9. The method for preparing a composite membrane according to claim 7, wherein: The two halves (11, 12) are barrel-shaped, with barrel openings arranged opposite to each other, and a feed port (30) is provided on the barrel wall.

10. The method for preparing a composite membrane according to claim 6, wherein: The container (10) is made of a corrosion-resistant transparent material.

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