CN115608163A - A method for preparing symmetrical polyamide membranes in a solvent-free environment - Google Patents

Abstract

A method for preparing symmetrical polyamide membranes in a solvent-free environment. Amine compounds and acyl chloride compounds are used as raw materials, and they are respectively placed in a temperature environment of 40-100°C for gas-phase treatment. During the process, the gas-phase amines generated in real time The gas-phase amine compounds and gas-phase acyl chloride compounds are transported to the closed membrane with a symmetrical porous basement membrane inside, and the gas-phase amine compounds and gas-phase acyl chlorides are respectively located on one side of the symmetrical porous basement membrane in the closed membrane. Gas-phase amine compounds and gas-phase acyl chloride compounds will be polymerized on the symmetrical porous base membrane at a temperature of 40-100°C for 30-180 minutes to obtain a finished symmetrical polyamide membrane. The preparation method of the present invention does not use any solvent in the whole process, reduces environmental pollution and cost, and the prepared polyamide membrane has a loose structure, a completely symmetrical structure, a high degree of membrane layer bonding, is not easy to peel off, and has excellent separation performance.

Description

A method for preparing symmetrical polyamide membranes in a solvent-free environment

technical field

The invention relates to the technical field of membrane separation, in particular to a method for preparing a symmetrical polyamide membrane by a solventless polymerization method.

Background technique

Polyamide membranes have been widely used in the field of separation, such as separating carbon dioxide from mixed gases, separating hydrogen from mixed gases, or seawater desalination, etc. The traditional preparation method of polyamide membrane is the interfacial polymerization method, that is, the amine compound is dissolved in deionized water or ionic liquid as a phase A solution, and then the acid chloride compound is dissolved in an organic solvent (such as n-hexane, n-dodecane and n-dodecane). Hexadecane, etc.) is recorded as the B-phase solution. The porous substrate consists of a nonwoven layer and a polysulfone layer. The side of the polysulfone layer of the porous substrate is first immersed in the A phase solution for a certain period of time and then dried, then the same side is immersed in the B phase solution for a certain period of time and then dried, and then polymerized at a certain temperature (40~90°C) for a certain period of time A dense polyamide layer is formed on a porous substrate polysulfone layer to obtain a polyamide membrane. The polyamide membrane prepared by this method is composed of a three-layer structure, namely the uppermost polyamide layer, the middle polysulfone layer and the lowermost non-woven layer. Therefore, the polyamide membrane prepared by the traditional interfacial polymerization method is non-toxic Symmetrical membrane, the uppermost polyamide layer really plays a role in separation. The disadvantages of this traditional preparation process are:

1. The polyamide layer structure in the polyamide membrane prepared by the traditional interfacial polymerization method is dense, which is not conducive to the passage of molecules, so the permeation of gas molecules or water flux is small. 2. Since the traditional interfacial polymerization process of amine compounds and acid chloride compounds is a violent exothermic reaction, the surface of the formed polyamide layer presents a leaf-like or nodular shape, resulting in poor uniformity of the polyamide membrane and unstable separation performance. 3. The polyamide membrane prepared by the traditional interfacial polymerization method is an asymmetric membrane, not only the polyamide layer is easily detached from the substrate, but also the separation operation of the polyamide membrane can only be carried out from the polyamide layer side. 4. The process of preparing polyamide membrane by traditional interfacial polymerization requires the use of toxic and flammable organic solvents, which has environmental pollution problems; or the use of high-priced ionic liquids, resulting in high preparation costs.

Therefore, how to improve the existing preparation process so that it can prepare polyamide membranes with uniform structure at low cost, quickly and efficiently is necessary to reduce environmental pollution and improve the separation performance of polyamide membranes.

Contents of the invention

The technical purpose of the present invention is: to prepare a polyamide membrane with a loose structure, a completely symmetrical structure, a high degree of membrane bonding, not easy to peel off, and excellent separation performance without using any solvent, so as to reduce environmental pollution. cut costs.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: a method for preparing symmetrical polyamide membranes in a solvent-free environment. According to a certain molar ratio, amine compounds and acid chloride compounds are respectively taken as raw materials, and the The amine compounds and the acid chloride compounds are respectively placed in a temperature environment of 40~100°C for gas-phase treatment. During the gas-phase treatment, the gas-phase amine compounds and gas-phase acid chloride compounds generated in real time are respectively transported to the internal clamping There is a closed membrane with a symmetrical porous base membrane, and the gas phase amine compound and the gas phase acid chloride compound are respectively located on one side of the symmetrical porous base membrane in the closed membrane, and the gas phase amine compound and the gas phase acid chloride compound will be in the symmetrical porous Polymerization is carried out on the basement membrane at a temperature of 40-100°C for 30-180 minutes to obtain a finished symmetrical polyamide membrane.

Preferably, the amine compound is any one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, ethylenediamine, diethylenetriamine, triethylenetetramine and piperazine.

Preferably, the acid chloride compound is any one of trimesoyl chloride, phthaloyl chloride, isophthaloyl chloride and terephthaloyl chloride.

Preferably, the pore diameter of the symmetrical porous basement membrane is 1-400 nm.

Preferably, the symmetrical porous base membrane is based on symmetrical polyacrylonitrile, symmetrical polyvinylidene fluoride, symmetrical nylon, symmetrical polyethersulfone, symmetrical mixed cellulose or symmetrical polyvinyl chloride.

Preferably, the molar ratio of the amine compound and the acid chloride compound in the raw material is 1:1 to 1:3.

A method for preparing symmetrical polyamide membranes in a solvent-free environment, specifically comprising the following steps:

Step 1. Take the symmetrical porous basement membrane and clamp it vertically in the airtight membrane tool. On the left and right sides of the airtight mold, connect with the inside of the amine compound storage bottle and the acyl chloride compound storage bottle through a connecting conduit respectively to form a Polymerization reaction device, standby;

Step 2. First weigh 0.1~3g of amine compounds and place them in the amine compound storage bottle, then weigh a certain amount of acid chloride compounds and place them in the acid chloride compound storage bottle, so as to ensure that the moles of the acid chloride compounds weighed are amine 1 to 3 times the number of moles of similar compounds, for later use;

Step 3. Put the polymerization reaction device made in step 1 into an oven with a temperature of 40-100°C for 30-180 minutes of polymerization reaction. The gas-phase amine compounds and acid chloride compounds produced in the amine compound storage bottle are produced in the storage bottle. The gas-phase acyl chloride compounds will enter the closed membrane tool through the connecting conduit, and polymerize on the surface of the symmetrical porous base membrane, and finally produce the finished symmetrical polyamide membrane.

Preferably, in Step 1, the symmetrical porous base membrane is clamped at the inner center of the closed mold, and the connecting conduit is connected to the middle of the left and right sides of the closed mold.

Beneficial effect:

1. The preparation method of the present invention adopts the method of gas phase polymerization, and without using any solvent, it can quickly and efficiently prepare a polymer with a stable structure, a high degree of film bonding, not easy to peel off, and a completely symmetrical structure. Amide film. The prepared polyamide membrane has a loose and uniform structure, which avoids the dense structure of the polyamide membrane prepared by traditional interfacial polymerization and the phenomenon of uneven membrane structure caused by the intense heat release during the polymerization process. Polyamide membrane for better separation performance.

2. The preparation process of the present invention is simple and easy to operate, while avoiding the environmental pollution problem caused by the use of organic solvents, and reducing the preparation cost.

3. The preparation process of the present invention can adjust the temperature to control the rate of formation of the gas phase and the volume density of the gas phase of the amine compound and the acid chloride compound, thereby affecting the polymerization process and obtaining a symmetrical polyamide membrane with a loose structure, which is more conducive to the passage of molecules. That is, the symmetrical polyamide membrane prepared by the solvent-free polymerization method has a large gas molecule permeation or water flux. At the same time, the adjustment of the volume density of the gas phase makes the polymerization process of the two gas phases slow, and the microstructure of the formed symmetrical membrane material is uniform, so that the symmetrical polyamide membrane exhibits stable separation performance. The polyamide membrane prepared by the solvent-free polymerization method is a symmetrical membrane, and the polyamide structure and the substrate are perfectly integrated without peeling off. The symmetric polyamide membrane prepared by the solvent-free polymerization method does not use toxic and flammable organic solvents, so there is no environmental pollution problem; high-priced ionic liquids are not used, and the preparation cost is low.

4. In the preparation process of the present invention, by adjusting the temperature of the reactants (40-100°C), the amine compounds and the acyl chloride compounds are in the gas phase state and contact the left and right sides of the symmetrical porous basement membrane respectively. The amine compound molecules and the acid chloride compound molecules penetrate and contact each other in the symmetrical porous basement membrane, and the amine groups of the amine compound molecules and the acid chloride groups of the acid chloride compound molecules undergo condensation reactions to form amide groups, and finally the polyamide network structure interacts with each other. Connecting and wrapping the symmetrical porous basement membrane to form a symmetrical polyamide membrane. The combination of the two is high, it is not easy to separate, and the uniformity is strong, so that the separation ability of the finished polyamide membrane is significantly improved.

Description of drawings

Fig. 1 is the structural representation of the polymerization reaction device that the present invention adopts;

Fig. 2 is the photo of the symmetrical polyamide membrane prepared by the embodiment of the present invention 1;

Fig. 3 is a FESEM image of the symmetrical polyamide membrane prepared in Example 1 of the present invention.

Description of drawings: 1. Amine compounds, 2. Acid chloride compounds, 3. Amine compound storage bottle, 4. Acid chloride compound storage bottle, 5. Gas phase amine compound, 6. Gas phase acid chloride compound, 7. Connecting conduit , 8, closed membrane tool, 9, symmetrical porous basement membrane.

detailed description

The technical solution of the present invention will be further elaborated and described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a method for preparing a symmetrical polyamide membrane in a solvent-free environment uses a symmetrical porous substrate membrane (such as symmetrical polyacrylonitrile, symmetrical polyvinylidene fluoride, symmetrical nylon, symmetrical Polyethersulfone, symmetrical mixed cellulose, symmetrical polyvinyl chloride, etc.) as the base. Weigh 0.1~3g of amine compound (1) into the amine compound storage bottle (3), and then weigh a certain amount of acid chloride compound (2) (guarantee that the moles of the acid chloride compound are equal to the moles of the amine compound 1~3 times) into the storage bottle (4) of the acid chloride compound. The symmetrical porous basement membrane (9) is clamped in the airtight membrane tool (8). Place the entire polymerization reaction device in an oven at a set temperature (40-100°C) for a certain period of time (30-180min). During this process, the amine compound (1) and the acid chloride compound (2) generate the corresponding gas phase amine compound (5) and gas phase acid chloride compound (6). The two gas phases respectively contact the symmetrical porous basement membrane (9) through the connecting conduit (7), and polymerize in and on the surface of the symmetrical porous basement membrane (9) to finally form a symmetrical polyamide membrane.

The process adjusts the temperature (40~100°C) to make amine compounds (such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, ethylenediamine, diethylenetriamine, triethylenetetramine , piperazine, etc.) and acyl chlorides (such as trimesoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, etc.) become gas phase and contact both sides of the symmetrical porous basement membrane respectively. The amine compound molecules and the acid chloride compound molecules penetrate and contact each other in the symmetrical porous basement membrane, and the amine groups of the amine compound molecules and the acid chloride groups of the acid chloride compound molecules undergo condensation reactions to form amide groups, and finally the polyamide network structure interacts with each other. Connecting and wrapping the symmetrical porous basement membrane to form a symmetrical polyamide membrane. The method avoids the defects that the asymmetric polyamide membrane prepared by the traditional interfacial polymerization method has a compact structure and is likely to cause environmental pollution, and can improve the separation ability of the polyamide membrane.

Example 1:

Weigh 1g of m-phenylenediamine into the amine compound storage bottle, then weigh 2.45g of trimesoyl chloride into the acid chloride compound storage bottle (the molar ratio of m-phenylenediamine to trimesoyl chloride is 1:1 ). Take the symmetrical polyacrylonitrile basement membrane and clamp it in the membrane tool. Put the polymerization reaction apparatus into an oven at 70° C. for 90 minutes. During this process, m-phenylenediamine and trimesoyl chloride generate corresponding gas phase m-phenylenediamine and gas phase trimesoyl chloride. The two gas phases respectively contact the left and right sides of the symmetrical porous basement membrane through the connecting conduit, and polymerize in and on the surface of the symmetrical polyacrylonitrile basement membrane to finally form a symmetrical polyamide membrane.

Example 2:

The preparation method of this example is the same as that of Example 1, except that the amount of trimesoyl chloride is adjusted to 3.68 g (the molar ratio of m-phenylenediamine to trimesoyl chloride is 1:1.5).

Example 3:

The preparation method of this example is the same as that of Example 1, except that the amount of trimesoyl chloride is adjusted to 7.36 g (the molar ratio of m-phenylenediamine and trimesoyl chloride is 1:3).

Example 4:

The preparation method of this embodiment is the same as that of Example 1, except that the temperature of the oven is set at 50°C.

Example 5:

The preparation method of this embodiment is the same as that of Example 1, except that 1 g of m-phenylenediamine as a raw material is replaced by 1 g of p-phenylenediamine.

Embodiment 6:

The preparation method of this embodiment is the same as that of Example 1, except that 2.45 g of trimesoyl chloride is replaced by 1.88 g of isophthaloyl chloride.

Embodiment 7:

The preparation method of this embodiment is the same as that of Example 1, only the polymerization reaction in the oven is adjusted to 180min.

The symmetric polyamide membrane prepared by each embodiment is tested for performance as follows:

Table 1

project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 CO₂ penetration (Barrer) 441 356 331 491 467 483 419 CO₂/CH₄ separation factor 17 20 twenty one 10 15 11 twenty one CO₂/N₂ separation factor 34 37 38 17 31 19 36

As can be seen from Table 1, the symmetric polyamide membrane prepared by the solvent-free polymerization method exhibited better _CO2 separation performance. Comparing Examples 2 and 3 with Example 1, it can be seen that increasing the amount of trimesoyl chloride increases the separation coefficients of CO ₂ /CH ₄ and CO ₂ /N ₂ , but the amount of CO ₂ permeated decreases. Comparing Example 4 with Example 1, it can be seen that appropriately lowering the polymerization temperature can increase the CO ₂ permeation rate of the symmetrical polyamide membrane. Comparing Example 5 with Example 1, it can be seen that the polyamide membrane prepared with m-phenylenediamine as the source of amine compounds has a greater CO ₂ permeation capacity, but the separation coefficients of CO ₂ /CH ₄ and CO ₂ /N ₂ are reduced. Comparing Example 6 with Example 1, it can be seen that the polyamide membrane prepared with isophthaloyl chloride as the source of acid chlorides has a larger CO permeation capacity, but the separation coefficients of CO ₂ / _{CH 4} and CO ₂ /N ₂ are reduced, The reason may be that compared with trimesoyl chloride, isophthaloyl chloride molecule has one less acid chloride group. Comparing Example 7 with Example 1, it can be seen that prolonging the polymerization time is more conducive to obtaining a dense polyamide film. Based on the above properties, it can be seen that the symmetrical polyamide membrane prepared by the present invention has significant advantages compared with the membrane materials reported in the existing literature.

Claims (8)

1. A method for preparing a symmetric polyamide membrane in a solvent-free environment, which is characterized by comprising the following steps: according to a certain molar ratio, taking an amine compound and an acyl chloride compound as raw materials respectively, placing the amine compound and the acyl chloride compound which are weighed into an environment with the temperature of 40-100 ℃ respectively for gas phase treatment, in the process of the gas phase treatment, respectively conveying the gas phase amine compound and the gas phase acyl chloride compound which are generated in real time into a closed film which is clamped with a symmetrical porous basement membrane inside, respectively positioning the gas phase amine compound and the gas phase acyl chloride compound at one side of the symmetrical porous basement membrane in the closed film, and carrying out polymerization reaction on the gas phase amine compound and the gas phase acyl chloride compound on the symmetrical porous basement membrane at the temperature of 40-100 ℃ for 30-180min to obtain the finished product symmetrical polyamide membrane.

2. The method of claim 1, wherein the symmetric polyamide membrane is prepared in a solvent-free environment, and wherein: the amine compound is any one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, ethylenediamine, diethylenetriamine, triethylenetetramine and piperazine.

3. The method of claim 1, wherein the symmetric polyamide membrane is prepared in a solvent-free environment, and wherein: the acyl chloride compound is any one of trimesoyl chloride, phthaloyl chloride, isophthaloyl chloride and terephthaloyl chloride.

4. The method of claim 1, wherein the symmetric polyamide membrane is prepared in a solvent-free environment, and wherein: the aperture of the symmetrical porous basement membrane is 1 to 400nm.

5. The method of claim 1 for preparing a symmetric polyamide membrane in a solvent-free environment, wherein: the symmetrical porous basement membrane takes symmetrical polyacrylonitrile, symmetrical polyvinylidene fluoride, symmetrical nylon, symmetrical polyether sulfone, symmetrical mixed cellulose or symmetrical polyvinyl chloride as a basement.

6. The method of claim 1, wherein the symmetric polyamide membrane is prepared in a solvent-free environment, and wherein: the molar ratio of the amine compound to the acyl chloride compound in the raw materials is 1-3.

7. The method of claim 1, comprising the steps of:

step one, vertically clamping a symmetrical porous basement membrane in a closed membrane, and respectively communicating the left side and the right side of the closed membrane with the interiors of an amine compound storage bottle and an acyl chloride compound storage bottle through a connecting conduit to form a polymerization reaction device for later use;

weighing 0.1 to 3g of amine compounds in an amine compound storage bottle, and then weighing a certain amount of acyl chloride compounds in an acyl chloride compound storage bottle, wherein the molar weight of the weighed acyl chloride compounds is ensured to be 1 to 3 times of that of the amine compounds for later use;

and step three, putting the polymerization reaction device prepared in the step one into an oven with the temperature of 40-100 ℃ for polymerization reaction for 30-180min, and allowing the gas-phase amine compound generated in the amine compound storage bottle and the gas-phase acyl chloride compound generated in the acyl chloride compound storage bottle to enter the closed membrane through the connecting conduit to perform polymerization reaction on the surface of the symmetrical porous base membrane to finally prepare the finished product symmetrical polyamide membrane.

8. The method of claim 7 for preparing a symmetric polyamide membrane in a solvent-free environment, wherein: in the first step, the symmetrical porous basement membrane is clamped at the inner center of the closed membrane, and the connecting conduits are connected to the middle parts of the left side and the right side of the closed mould.

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