Continuous cross-linking polymerization composite membrane preparation method and device

Abstract

The invention relates to the technical field of separation membrane materials. The preparation method of the continuous cross-linked polymeric composite membrane comprises the following steps: mixing and reacting two polymer precursors containing different functional groups, a cross-linking agent, at least one polymerization initiator and other additives to form a feed liquid A and a feed liquid B; (2) continuously immersing two bottom liners into the two material liquids respectively; (3) respectively pre-polymerizing the two bottom liners which are respectively infiltrated with the feed liquid A and the feed liquid B, (4) pressing one protective film, the two pre-polymerized bottom liners and the other protective film together, and (5) initiating deep cross-linking polymerization; and (6) stripping the protective film to obtain the functional film. The invention also discloses a device for continuously realizing the method. According to the method and the device, the functional membrane with a complicated structure can be continuously obtained, and a single functional membrane can be obtained by independently operating one bottom lining and one membrane casting solution.

Description

Technical Field

[0001] The invention relates to the technical field of separation membrane materials, and discloses a method and a device for preparing a composite membrane by continuous cross-linking polymerization. Background Art

[0002] Ion exchange membranes can be used to manufacture devices such as electrodialysis, electro-desalting, and diffusion dialysis, and are used in water desalination and seawater desalination, purification and concentration of brine or chemical aqueous solutions, separation of ions of different valence states, and preparation of acids and alkalis by water dissociation. They can also be used in electrolytic hydrogen production, electrolytic alkali production, and various battery devices. The bipolar membrane dissociates water and separates hydrogen ions and hydroxide ions under the action of an electric field, so it can be used to produce acids and alkalis from salt, and has good application prospects.

[0003] In the known technology, most bipolar membrane preparation methods are to prepare the anionic membrane separately and then composite them together. This composite method includes physical bonding with a binder and chemical cross-linking bonding with a binder. However, there is no chemical bond between the anionic membrane layer and the cationic membrane layer in these composite methods, and long-term use will produce a "bubbling" phenomenon, that is, the separation of the two membrane layers. On the other hand, the chemical bond that is used to combine the two membranes by chemical cross-linking in the known technology is usually an ether bond, a lipid bond or an amide bond that is easily hydrolyzed in a strong acid or alkali environment.

[0004] U.S. Patent No. 4,024,043 uses a high-density polyethylene film as a substrate, and impregnates styrene, divinylbenzene and an initiator into the substrate to initiate cross-linking polymerization to obtain a base film, and then sulfonates one side of the base film, and chloromethylates and ammonates the other side to obtain a bipolar membrane. Chinese Patent No. 2010102819974 uses the same method, but replaces the substrate material with a binary blend of polyethylene and ethylene and octene copolymer elastomer or a ternary blend of polyethylene, ethylene and octene copolymer elastomer and butene rubber, thereby improving the performance of the membrane product obtained by this method. In these methods, there is unevenness at the microscopic level during the process of styrene and divinylbenzene being impregnated into the substrate. The reason is that there are high crystalline areas and non-crystalline areas in the substrate structure, and the rate at which the coated liquid enters the non-crystalline area is relatively fast, so the impregnation in this area is high, and the relative strength of the product film here is relatively low. At the same time, the substrate has defects in the film forming process, and the impregnation ratio of the coating liquid at the defective point is higher, and starting from this point, a dendritic high impregnation area is formed. The final result is that this defect is magnified in the finished membrane, greatly reducing the qualified rate of the finished membrane. On the other hand, since a non-porous membrane is used, its swelling and impregnation temperature is high, the time is long, and the consumption of coating liquid is large; the chemical stability of the polyethylene backing is insufficient, and carbonization occurs during the sulfonation process, which affects the strength of the product. Another disadvantage of this method is that it is difficult to produce continuously.

[0005] Chinese patent application CN117323824A discloses a method for preparing hydrogen barrier anion membrane by roller dipping method. The method disclosed in the related implementation lacks proper tension control, the system is difficult to be stably controlled, and is only suitable for preparing functional membranes with a single casting solution, and is not suitable for preparing functional membranes with complex structures. Summary of the invention

[0006] The purpose of the present invention is to disclose a method and device for preparing a composite membrane by continuous cross-linking polymerization, which can be used to prepare functional membranes with complex structures such as bipolar membranes, price-selective membranes, and hydrogen-blocking negative molds.

[0007] In order to achieve the above purpose, the method for preparing a composite membrane by continuous cross-linking polymerization of the present invention is characterized in that it includes (1) mixing and reacting two polymer precursors containing different functional groups, a cross-linking agent, at least one polymerization initiator and other additives to form a slurry A and a slurry B respectively; (2) continuously immersing two substrates in the two slurries respectively; (3) pre-polymerizing the two substrates respectively soaked in the slurry A and the slurry B; (4) pressing a protective film, the two substrates that have been pre-polymerized and another protective film together; (5) initiating deep cross-linking polymerization; and (6) peeling off the protective film to obtain the functional membrane.

[0008] The two substrates may be of the same kind or of different kinds.

[0009] The composite film preparation device of the continuous cross-linking polymerization of the present invention is characterized by comprising a backing A discharge roller, a backing A discharge tension roller, a liquid A tank, at least one liquid B tank guide roller, a liquid A material distribution roller pair, a liquid A prepolymerization reactor, a backing B discharge roller, a backing B discharge tension roller, a liquid B tank, at least one liquid B tank guide roller, a liquid B material distribution roller pair, a liquid B prepolymerization reactor, a protective film X discharge roller, a protective film X discharge tension roller, a protective film Y discharge roller, a protective film Y discharge tension roller, a protective film composite roller pair, at least one secondary reactor, at least one laminating guide roller, a protective film stripping roller pair, a protective film X receiving tension roller, a protective film X receiving roller, a protective film Y receiving tension roller, a protective film Y receiving roller, a product film receiving tension roller, and a product film receiving roller;

[0010] The resistance and rotation speed of the backing A unloading roller, the backing B unloading roller, the protective film X unloading roller and the protective film Y unloading roller are respectively controlled by the backing A tension roller, the backing B unloading tension roller, the protective film X unloading tension roller and the protective film Y unloading tension roller; the rotation speeds of the protective film X receiving roller, the product film receiving roller and the protective film Y receiving roller are respectively controlled by the protective film receiving tension roller, the product film receiving tension roller and the protective film receiving tension roller C.

[0011] The feed liquid A prepolymerization reactor, the feed liquid B prepolymerization reactor and the secondary reactor are one or more combinations of reactors for initiating polymerization, including but not limited to ultraviolet light-initiated polymerization reactors and thermally-initiated polymerization reactors.

[0012] The liquid tank A and the liquid tank B are provided with a constant temperature device.

[0013] The liquid tank A and the liquid tank B are provided with ultrasonic oscillation devices.

[0014] The beneficial effects of the composite membrane preparation method and device of the present invention by continuous cross-linking polymerization are: a functional membrane with complex structure can be obtained continuously, and a single functional membrane can also be obtained by operating a substrate and a liquid separately. After the prepolymerization, the viscosity of the two casting liquids is greatly improved, so when the two substrates are pressed together, the two casting liquids are restricted from combining with each other; at the same time, since the polymerization is not completed, the two liquids are cross-linked and polymerized into a single molecule, thereby obtaining a complex structure functional membrane with stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the composite membrane preparation device of the present invention by continuous cross-linking polymerization.

[0016] In the figure: 11. Feed roller of backing A, 12. Feed tension roller of backing A, 13. A feed liquid A tank, 14. Guide roller of feed liquid B tank, 15. Feed liquid A equalizing roller pair, 16. Feed liquid A prepolymerization reactor, 21. Feed roller of backing B, 22. Feed tension roller of backing B, 23. Feed liquid B tank, 24. Guide roller of feed liquid B tank, 25. Feed liquid B equalizing roller pair, 26. Feed liquid B prepolymerization reactor, 35. Feed roller of protective film X, 36. 6. Protective film X unloading tension roller, 45. Protective film Y unloading roller, 46. Protective film Y unloading tension roller, 57. Protective film composite roller pair, 60. Secondary reactor, 61 laminating guide roller, 70. Protective film peeling roller pair, 88. Protective film X receiving tension roller, 89. Protective film X receiving roller, 98. Protective film Y receiving tension roller, 99. Protective film Y receiving roller, 108. Product film receiving tension roller, 109. Product film receiving roller DETAILED DESCRIPTION

[0017] The substrate A and substrate B enter the liquid tank A (13) containing liquid A and the liquid tank B (23) containing liquid B from the substrate A discharge roller (11) and the substrate B discharge roller (21) respectively through the substrate A discharge tension roller (12) and the substrate B discharge tension roller (22), and are immersed in the casting liquid A and the casting liquid B with the assistance of at least one liquid tank A guide roller (14) and at least one liquid tank B guide roller (24), and enter the liquid A prepolymerization reactor (16) and the liquid B prepolymerization reactor (26) respectively through the liquid A equalizing roller pair and the liquid B equalizing roller pair, and in the The protective film composite roller pair (57) is compacted into a protective composite film; the protective composite film enters a secondary reactor (60) containing at least one laminating guide roller (61) to react, and then the protective composite film is separated into a protective film X, a product film and a protective film Y by a protective film stripping roller pair (70); the protective film X is wound up by a protective film X winding tension roller (88) and a protective film X winding roller (89); the product film and the protective film Y are wound up by a protective film Y winding tension roller (98) and a protective film Y winding roller (99); and the product film is wound up by a product film winding tension roller (108) and a product film winding roller (109). Example 1

[0018] A bipolar ion exchange membrane is prepared by a membrane preparation method and a membrane preparation device using continuous cross-linking polymerization.

[0019] 1. Prepare liquid A. Mix propylene sulfonic acid (41.5% by weight), divinylbenzene (14.0%), azobisisobutyronitrile (1.5%), diethylene glycol (42.0%), and Tween 10 (1.0%) evenly.

[0020] 2. Prepare liquid B. Mix chloromethylstyrene (35.0%), divinylbenzene (14.5%), dimethylethanolamine (20.4%), azobisisobutyronitrile (1.5%), diethylene glycol (27.6%), and Tween 10 (1.0%).

[0021] 3. The feed liquid A prepolymerization reactor (16) and the feed liquid B prepolymerization reactor (26) are thermal polymerization reactors, which are preheated to a set temperature of 65 degrees Celsius. The secondary reactor (60) is a thermal polymerization reactor, which is preheated to a set temperature of 90 degrees Celsius.

[0022] 4. Select a microporous membrane with a thickness of 70 microns as the backing A, and select a microporous membrane with a thickness of 40 microns as the backing B. Install the backing A roll, the backing B roll and the two rolls of polyester protective film on the corresponding unwinding rollers (11, 21, 35, 45), and place the backing A, backing B and protective film as shown in the figure. Figure 1 As shown, it leads to the product film receiving roller (109), the protective film X receiving roller (89) and the protective film Y receiving roller (109).

[0023] 5. Automatically start the protective film X receiving roller (89), the protective film Y receiving roller (99) and the product film receiving roller (109); respectively control the rotation speeds of the protective film X receiving roller (89), the protective film Y receiving roller (99) and the product film receiving roller (109) through the protective film X receiving tension roller (89), the protective film Y receiving roller (99) and the product film tension roller (109); respectively control the discharge resistance of the backing A discharge roller (11), the backing B discharge roller (21), the protective film X discharge roller (35) and the protective film Y discharge roller (45) through the backing A discharge tension roller (12), the backing B discharge tension roller (22), the protective film X discharge tension roller (36) and the protective film Y discharge tension roller (46).

[0024] 6. Add liquid A and liquid B into liquid A tank and liquid B tank respectively.

[0025] 7. Adjust the feeding speed, the temperature of the prepolymerization reactor and the temperature of the secondary reactor so that the liquid A and the liquid B lose fluidity after the prepolymerization, but still have adhesion, and the secondary reactor makes the liquid A and the liquid B completely cross-linked and polymerized.

Claims

1. A method for preparing a composite membrane by continuous cross-linking polymerization, characterized in that The method comprises: (1) mixing and reacting two polymer precursors containing different functional groups, a crosslinking agent, at least one polymerization initiator and other additives to form liquid A and liquid B; (2) continuously immersing two substrates in the two liquids; (3) prepolymerizing the two substrates respectively soaked in liquid A and liquid B; (4) pressing a protective film, the two prepolymerized substrates and another protective film together; (5) initiating deep crosslinking polymerization; and (6) peeling off the protective film to obtain the functional film.

2. The method for preparing a composite membrane by continuous cross-linking polymerization according to claim 1, characterized in that The two substrates may be of the same kind or of different kinds.

3. A composite membrane preparation device for continuous cross-linking polymerization, characterized in that It includes a backing A discharge roller, a backing A discharge tension roller, a liquid A tank, at least one liquid B tank guide roller, a liquid A material distribution roller pair, a liquid A prepolymerization reactor, a backing B discharge roller, a backing B discharge tension roller, a liquid B tank, at least one liquid B tank guide roller, a liquid B material distribution roller pair, a liquid B prepolymerization reactor, a protective film X discharge roller, a protective film X discharge tension roller, a protective film Y discharge roller, a protective film Y discharge tension roller, a protective film composite roller pair, at least one secondary reactor, at least one laminating guide roller, a protective film peeling roller pair, a protective film X receiving tension roller, a protective film X receiving roller, a protective film Y receiving tension roller, a protective film Y receiving roller, a product film receiving tension roller, and a product film receiving roller; The resistance and rotation speed of the backing A unloading roller, the backing B unloading roller, the protective film X unloading roller and the protective film Y unloading roller are respectively controlled by the backing A tension roller, the backing B unloading tension roller, the protective film X unloading tension roller and the protective film Y unloading tension roller; the rotation speeds of the protective film X receiving roller, the product film receiving roller and the protective film Y receiving roller are respectively controlled by the protective film receiving tension roller, the product film receiving tension roller and the protective film receiving tension roller.

4. The composite membrane preparation device of continuous cross-linking polymerization according to claim 3, characterized in that The feed liquid A prepolymerization reactor, the feed liquid B prepolymerization reactor and the secondary reactor are one or more combinations of reactors for initiating polymerization, including but not limited to ultraviolet light-initiated polymerization reactors and thermally-initiated polymerization reactors.

5. The composite membrane preparation device of continuous cross-linking polymerization according to claim 3, characterized in that The liquid tank A and the liquid tank B are provided with a constant temperature device.

6. The composite membrane preparation device of continuous cross-linking polymerization according to claim 3, characterized in that The liquid tank A and the liquid tank B are provided with ultrasonic oscillation devices.

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