A polyurea hydrogel membrane and its preparation method

Abstract

This invention discloses a polyurea hydrogel membrane and its preparation method. The method includes the following steps: (1) adding polyisocyanate trimer, blocking agent, solvent and catalyst into a reactor in sequence, starting stirring and heating to obtain a blocked polyisocyanate component; (2) adding the blocked polyisocyanate component to a certain proportion of deionized water, stirring evenly, filtering to remove catalyst impurities; (3) mixing the product obtained in step (2) with polyetheramine in a certain proportion, transferring to a vacuum drying oven, and removing small molecule impurities for 36-48 hours at room temperature and -0.1-0 MPa to obtain a purified blocked polyisocyanate and polyetheramine composition; (4) coating the purified blocked polyisocyanate and polyetheramine composition onto a mold and heating to obtain a polyurea hydrogel membrane. The polyurea hydrogel membrane prepared by this invention has the characteristics of low temperature resistance, transparency and flexibility.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, specifically to a polyurea hydrogel membrane and its preparation method. Background Technology

[0002] Hydrogels are polymeric materials with a three-dimensional network structure that can absorb large amounts of water without dissolving in water while maintaining their structural integrity. This unique property makes hydrogels extremely promising for applications in the biomedical field. The network structure of hydrogels is typically formed through chemical or physical cross-linking, which endows them with excellent flexibility, biocompatibility, and controllability. In the mid-20th century, Wichterle et al. used the free radical polymerization of the monomer 2-hydroxyethyl methacrylate (HEMA) and added a small amount of cross-linking agent (such as ethylene glycol dimethacrylate) to achieve cross-linking, forming a stable three-dimensional network structure. This hydrogel, due to its excellent transparency and softness, has been widely used in the manufacture of contact lenses, pioneering the application of hydrogels in the biomedical field and laying the foundation for the development of subsequent hydrogel materials.

[0003] Existing polyurea hydrogel films suffer from several defects that limit their performance and applications. First, mechanical properties are difficult to balance, resulting in high brittleness, easy cracking, or insufficient strength. This is mainly due to the excessively rapid polymerization rate leading to an uneven cross-linked network, and the imperfect microphase separation structure between soft and hard segments, which fails to effectively dissipate energy. Second, biocompatibility is poor because residual isocyanate monomers have potential toxicity, and the material may produce harmful byproducts after degradation. Third, processing and molding are difficult. The reaction system suffers from insufficient leveling time due to excessively rapid gelation, and often relies on toxic organic solvents, leading to complex film formation processes and poor film uniformity. Fourth, the material has limited functionality and lacks intelligent responsiveness, stemming from molecular design focused on building a basic network without introducing functional components. Fifth, long-term immersion easily leads to swelling and mechanical property degradation, which is related to the hydrolytic sensitivity of urea bonds and the relaxation of physical cross-linking points under the influence of water. Currently, although improvements are being made through molecular structure design, composite modification, and green processes, these problems have not been fundamentally solved. Summary of the Invention

[0004] The purpose of this invention is to provide a polyurea hydrogel film and its preparation method, wherein the polyurea hydrogel film has the characteristics of low temperature resistance, transparency and flexibility.

[0005] In one aspect of the present invention, a method for preparing a polyurea hydrogel membrane is provided. According to an embodiment of the present invention, the method includes the following steps:

[0006] (1) The polyisocyanate trimer, blocking agent, solvent and catalyst were added to the reactor in sequence, the stirring was started and the temperature was raised to prepare the blocked polyisocyanate component.

[0007] (2) Add the blocked polyisocyanate component to a certain proportion of deionized water, stir evenly, filter, and remove catalyst impurities;

[0008] (3) The product obtained in step (2) is mixed with polyetheramine in a certain proportion and transferred to a vacuum drying oven. Small molecule impurities are removed at room temperature and under -0.1-0 MPa conditions for 36-48 hours to obtain a purified blocked polyisocyanate and polyetheramine composition.

[0009] (4) The purified blocked polyisocyanate and polyetheramine composition is coated into a mold and heated to obtain a polyurea hydrogel film.

[0010] In addition, the method for preparing a polyurea hydrogel film according to the above embodiments of the present invention may also have the following additional technical features:

[0011] In some embodiments of the present invention, in step (1):

[0012] The polyisocyanate trimer is one or a mixture of two or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, isophthalimethylene diisocyanate trimer, and hydrogenated diphenylmethane diisocyanate trimer. The purpose of adding the polyisocyanate trimer and blocking it is to construct a high-strength, highly stable cross-linked network framework. Through a "blocking-deblocking" chemical strategy, the uncontrollable rapid reaction is transformed into a controllable processing procedure, thereby systematically improving the shortcomings of traditional polyurea hydrogels in terms of processability, mechanical properties, and biosafety.

[0013] The blocking agent is one or a mixture of two or more of the following: diethyl malonate, dimethyl malonate, diisopropyl malonate, di-tert-butyl malonate, ethyl acetoacetate, ethyl benzoyl, monoethyl malonate, diethyl methyl malonate, malonamide, and cyanoacetamide. The purpose of adding the blocking agent is to temporarily protect the highly reactive isocyanate groups (-NCO) on the polyisocyanate trimer through a chemical reaction, generating a stable "blocked isocyanate" at room temperature. Its fundamental purpose is to achieve controllability of the reaction, transforming uncontrollable rapid polymerization into a controllable process triggered by external conditions (such as heating), thereby solving processing and molding problems and improving process safety. The reason for selecting the above chemicals as blocking agents is based on their combined advantages of efficient blocking reaction, suitable and controllable deblocking temperature, and generation of harmless volatile byproducts.

[0014] In some embodiments of the present invention, in step (1), the solvent is one or a mixture of two or more of acetone, butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol methyl ether acetate, and diethylene glycol diacetate. Adding a solvent can provide a homogeneous reaction medium for the reactants (polyisocyanate trimer, blocking agent) and catalyst, ensuring sufficient intermolecular contact and efficient mass transfer. Its fundamental purpose is to ensure the smooth progress of the blocking reaction and control the reaction process. The above solvents have strong polarity, excellent solubility for polyisocyanate trimer, blocking agent, and most polymer intermediates, and good compatibility with the system.

[0015] The catalyst is one or a mixture of two or more of sodium methoxide, sodium ethoxide, potassium tert-butoxide, sodium tert-butoxide, potassium methoxide, sodium hydrogen hydride, sodium hydroxide, lithium diisopropylamide, and lithium hexamethylenedisilamide. Adding a catalyst can significantly reduce the activation energy of the reaction and efficiently promote the nucleophilic addition reaction between the active methylene group of the blocking agent and the isocyanate group (-NCO). Its fundamental purpose is to achieve a rapid, complete, and controllable blocking reaction under relatively mild conditions (such as a suitable temperature), thereby ensuring high conversion rate and batch stability of the blocked product, which is a prerequisite for subsequent controllable curing processes. The above catalysts can provide a strongly alkaline environment, efficiently initiating the reaction. All listed substances are strong bases, and their core function is to rapidly remove the proton from the methylene group in the blocking agent, generating a highly reactive carbanion. This carbanion, as a strong nucleophile, can rapidly attack the -NCO group, thereby significantly improving the blocking reaction rate and efficiency.

[0016] In some embodiments of the present invention, in step (1), the mass ratio of polyisocyanate trimer, blocking agent, solvent, and catalyst is (100-120):(100-120):(200-240):1. This ratio range ensures complete and safe reaction by using a slight excess of blocking agent, controls the amount of solvent to provide a homogeneous and controllable reaction environment, and uses a trace amount of catalyst to achieve efficient catalysis. Together, these factors contribute to the preparation of a prepolymer with high blocking efficiency, storage stability, and excellent processing performance, thereby laying the foundation for the synthesis of a final material with controllable curing characteristics and balanced properties.

[0017] In some embodiments of the present invention, in step (1), the temperature of the heating reaction is 70-75°C, and the reaction time is 7-8 hours. Under the action of a strong alkaline catalyst, the active methylene carbanion of the blocking agent undergoes a nucleophilic addition reaction with the isocyanate group (-NCO) in the polyisocyanate trimer to form a thermally reversible blocking structure.

[0018] In some embodiments of the present invention, in step (2), 1-5 parts by mass of deionized water are added to every 100 parts by mass of the blocked polyisocyanate component. The residual strong alkaline catalyst is removed and filtered by hydrolysis, thereby quenching and purifying the reaction system, improving the purity and stability of the intermediate product, and clearing the way for the subsequent synthesis of high-performance, highly biocompatible hydrogel membranes.

[0019] In some embodiments of the present invention, in step (3), the polyetheramine comprises any one or more mixtures satisfying the following conditions:

[0020] (a) Mean functionality ≥ 3.0;

[0021] (b) All-ethylene oxide structure;

[0022] (c) Average molecular weight ≥ 1000.

[0023] In some embodiments of the present invention, in step (3), 20-80 parts by mass of blocked polyisocyanate component are added to every 100 parts by mass of polyetheramine. The reaction principle of step (3) is as follows: during the subsequent heating and curing stage, the blocked isocyanate groups are deblocked by heat, releasing highly active isocyanate groups (-NCO). These isocyanate groups (-NCO) rapidly undergo addition polymerization with the primary amine groups (-NH2) at the end of the polyetheramine molecule to generate urea bonds (-NH-CO-NH-). Since the polyetheramine usually has two or three amine groups (such as ternary polyetheramine), this reaction can not only linearly extend the chain, but also form a three-dimensional cross-linked network, constituting the matrix of the hydrogel. The polyetheramine is the key structural unit for forming the final polyurea hydrogel network. It constructs the network through chemical reaction and directly endows the material with the required flexibility, hydrophilicity and good biocompatibility through its molecular structure. The mixing and purification treatment in this step provides a process guarantee for achieving these properties.

[0024] In some embodiments of the present invention, in step (4), the heating temperature is 80-85°C and the heating time is 5-6 hours.

[0025] In another aspect of the present invention, the present invention provides a method for preparing the polyurea hydrogel membrane described above.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1) The curing temperature is significantly reduced in the preparation method of this invention, thus lowering energy consumption. Traditional processes typically require heating and curing at temperatures ranging from 120°C to 200°C to ensure complete cleavage of the blocking bonds and release of sufficient active isocyanate groups (-NCO) for full reaction with the polyetheramine. Existing technologies struggle to lower the curing temperature primarily due to the inherent contradiction between the high energy barrier required for the deblocking reaction and the room-temperature storage stability requirements, further limited by the chemical structure of traditional blocking agents. In this application, the isocyanate blocked by the active methylene compound crosslinks with the polyetheramine via an ester exchange mechanism. This reaction bypasses the high-temperature "deblocking" step. Crosslinking is achieved through direct nucleophilic attack of the active methylene carbon by the amine group. This pathway has a significantly lower activation energy than traditional deblocking pathways, allowing curing at only 80°C.

[0028] 2) The product prepared by this invention exhibits excellent hydrogel properties. The crosslinking of isocyanate trimers and multifunctional polyetheramines significantly enhances the mechanical strength and toughness of the hydrogel film and facilitates the formation of a stable three-dimensional network structure. This three-dimensional network is constructed by a stepwise addition polymerization reaction between isocyanate trimers and multifunctional polyetheramines: the trimer with three isocyanate groups acts as a rigid crosslinking node, while the long polyetheramine chain with primary amine groups at its ends acts as a flexible connecting unit. The two are covalently linked in space by urea bonds generated during the reaction, forming a uniform and stable crosslinked network. This microphase separation structure of "rigid nodes-flexible segments" provides strength support under stress through rigid regions, while the flexible segments dissipate energy through large deformations, thus synergistically achieving high strength and high toughness.

[0029] 3) The product prepared by this invention exhibits excellent biocompatibility and high safety. This invention eliminates the risk of highly reactive free isocyanate monomers at the source by introducing a chemically sealed reaction during the preparation process. Subsequent aqueous washing, filtration, and deep vacuum devolatilization effectively remove catalysts, small molecule impurities, and volatile components from the reaction system. This multi-stage purification mechanism ensures that the final product is free of toxic monomer residues and that its degradation products are safe and controllable, thereby significantly improving the biocompatibility of the material and meeting the requirements of applications with high biosafety standards.

[0030] 4) The product prepared by this invention has a mild and controllable process and produces high-quality films. The use of a closed-type precursor significantly reduces the activity of the reaction system, prolongs the operating window and leveling time after mixing with polyetheramine, and effectively avoids film defects caused by excessively rapid gelation. The entire process can be carried out in a water-based medium, eliminating the need for toxic organic solvents. This not only simplifies post-processing and avoids solvent toxicity but also facilitates the acquisition of high-quality hydrogel films with uniform thickness and smooth surfaces.

[0031] 5) The product network structure prepared by this invention is tunable and has strong functional extensibility. The preparation method provided by this invention has high component compatibility and designability. Mild and controllable reaction conditions allow for the flexible introduction of various functional components (such as temperature-sensitive or pH-responsive monomers, conductive materials, drug molecules, etc.) before film formation without causing gel runaway or functional inactivation. This provides an effective and universal preparation platform for constructing polyurea hydrogel materials with multifunctional properties such as environmental responsiveness, self-healing, drug loading, or conductivity.

[0032] 6) The product prepared by this invention exhibits excellent anti-swelling properties. The high-density chemically cross-linked network constructed with polyisocyanate trimer as the core provides a robust skeletal support for the material. Combined with a thorough purification process, swelling weaknesses within the network are reduced, resulting in a dense network structure dominated by stable chemical cross-links and supplemented by dynamic hydrogen bonds. This structure effectively inhibits excessive swelling of the material in an aqueous environment and the potential hydrolysis of urea bonds, enabling the material to maintain good dimensional stability and mechanical properties even under high humidity conditions. Attached Figure Description

[0033] Figure 1 This is the infrared spectrum of the polyurea hydrogel membrane in Embodiment 1 of the present invention;

[0034] Figure 2 This is the infrared spectrum of the polyurea hydrogel film in Embodiment 6 of the present invention;

[0035] Figure 3 These are the stress-strain curves of the polyurea hydrogel membranes in Examples 1-5 of this invention;

[0036] Figure 4 This is the stress-strain curve of the polyurea hydrogel membrane in Example 6 of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] A method for preparing a polyurea hydrogel film includes the following steps:

[0040] (1) In a four-necked flask, add 60g of hexamethylene diisocyanate trimer, 60g of diethyl malonate, 120g of ethyl acetate and 0.5g of sodium methoxide in sequence. Stir well at room temperature, then heat to 70℃ and react until the endpoint is reached to obtain the blocked polyisocyanate component, such as... Figure 1As shown, infrared spectroscopy detection at 2270 cm⁻¹ -1 The absorption peak of the isocyanate group (-NCO) completely disappeared;

[0041] (2) Add 5g of deionized water to the blocked polyisocyanate component prepared in step (1), stir evenly, let stand for 24h and then filter to obtain a blocked isocyanate mixed solution.

[0042] (3) Take 100g of polyetheramine (average molecular weight 5000, average functionality 3, primary amino end capped, all ethylene oxide segments, structural formula C2H5-[O-(C2H5O)). n [-CH2CH2-NH2]3, n value between 105-120) added 50g of the above-mentioned end-capped isocyanate mixed solution and stirred evenly. The mixture was placed in a vacuum drying oven and allowed to stand for 48h at room temperature and -0.1MPa to obtain a viscous blocked polyisocyanate and polyetheramine composition. The molar ratio of the blocked isocyanate group (-NCO) and the primary amino group (-NH2) of the polyetheramine in the blocked polyisocyanate and polyetheramine composition was 1:1.

[0043] (4) The above composition is uniformly coated in a polytetrafluoroethylene mold and placed in an oven at 80°C for 5 hours to obtain a polyurea hydrogel film.

[0044] Example 2

[0045] A method for preparing a polyurea hydrogel membrane differs from Example 1 only in that: in step (3), 100g of polyetheramine and 60g of capped isocyanate mixed solution are stirred evenly, while the other parameters and steps are the same. In this example, the molar ratio of the blocked isocyanate group (-NCO) and the polyetheramine primary amino group (-NH2) in the blocked polyisocyanate and polyetheramine composition is 1.2:1.

[0046] Example 3

[0047] A method for preparing a polyurea hydrogel membrane differs from Example 1 only in that: in step (3), 100g of polyetheramine and 40g of capped isocyanate solution are stirred evenly, while the other parameters and steps are the same. In this example, the molar ratio of the blocked isocyanate group (-NCO) and the primary amino group (-NH2) of the polyetheramine in the blocked polyisocyanate and polyetheramine composition is 0.8:1.

[0048] Example 4

[0049] A method for preparing a polyurea hydrogel membrane differs from Example 1 only in that: in step (3), 100g of polyetheramine and 65g of capped isocyanate solution are stirred evenly, while the other parameters and steps are the same. In this example, the molar ratio of the blocked isocyanate group (-NCO) and the polyetheramine primary amino group (-NH2) in the blocked polyisocyanate and polyetheramine composition is 1.2:1.

[0050] Example 5

[0051] A method for preparing a polyurea hydrogel membrane differs from Example 1 only in that: in step (3), 100g of polyetheramine and 45g of capped isocyanate solution are stirred evenly, while the other parameters and steps are the same. In this example, the molar ratio of the blocked isocyanate group (-NCO) and the primary amino group (-NH2) of the polyetheramine in the blocked polyisocyanate and polyetheramine composition is 0.8:1.

[0052] Example 6

[0053] A method for preparing a polyurea hydrogel film includes the following steps:

[0054] (1) In a four-necked flask, add 80g of isophorone diisocyanate trimer, 60g of diethyl malonate, 120g of ethyl acetate, and 0.5g of sodium methoxide in sequence. Stir well at room temperature, then heat to 70℃ and react until the endpoint is reached. Figure 2 As shown, infrared spectroscopy detection at 2270 cm⁻¹ -1 The absorption peak of the isocyanate group (-NCO) completely disappeared;

[0055] (2) Add 5g of deionized water to the product of step (1), stir evenly, let stand for 24h and then filter to obtain a capped isocyanate mixed solution;

[0056] (3) Take 100g of polyetheramine (average molecular weight 5000, average functionality 3, primary amino end capping, all ethylene oxide segments), add 55g of the above end capped isocyanate solution and stir evenly, place in a vacuum drying oven, and let stand for 48h at room temperature and -0.1MPa to obtain a viscous block polyisocyanate and polyetheramine composition; the molar ratio of the block isocyanate group (-NCO) and the primary amino group (-NH2) of the polyetheramine in the block polyisocyanate and polyetheramine composition is 1:1;

[0057] (4) The above composition is uniformly coated in a polytetrafluoroethylene mold and placed in an oven at 80°C for 5 hours to obtain a polyurea hydrogel film.

[0058] The performance of the polyurea hydrogel membranes prepared in Examples 1-6 was tested:

[0059] (1) Water absorption test

[0060] The prepared hydrogel membrane was soaked in deionized water for 24 hours, with the water changed every 4 hours to remove unreacted monomers and porogens. The washed sample was then placed in a vacuum drying oven (25℃, -0.1 MPa) and vacuum dried for at least 36 hours until constant weight was achieved. Samples with an area of ​​2 cm × 2 cm and a thickness of 1 mm were cut from the dried hydrogel membrane, and the dry weight (W) of each sample was recorded. d ); the known dry weight (W) d Immerse the sample in a container filled with sufficient test medium (physiological saline) until its weight no longer increases; after removal, gently blot off excess surface moisture with filter paper and weigh immediately (W). t Water absorption rate (SR): .

[0061] The results of the water absorption test are shown in Table 1:

[0062] Table 1. Results of water absorption tests for Examples 1-6

[0063] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Water absorption rate 10.0% 8.1% 11.2% 7.6% 10.7% 3.33%

[0064] Water absorption tests show that, by regulating the isocyanate trimer structure, the thermosetting polyurea hydrogel film prepared in this invention achieves precise control over swelling behavior. Specifically, Examples 1-5 use aliphatic linear hexamethylene diisocyanate trimers for crosslinking. The resulting regular and dense network structure effectively restricts the penetration of water molecules, keeping the water absorption rate stable in the low range of 7.6% to 11.2%, exhibiting good dimensional stability and anti-swelling properties. Example 6 uses isophorone diisocyanate trimers with a rigid alicyclic structure for crosslinking. The hydrophobicity of the isophorone ring and its induced close-packing effect further reduce the network free volume, thereby reducing the water absorption rate to 3.33%, achieving ultra-low swelling while maintaining excellent mechanical properties. This method overcomes the problem that traditional highly absorbent materials are prone to excessive swelling in a wet state, leading to dimensional or functional failure. The prepared material has potential application value in medical dressings, flexible electronic packaging, and other dynamic application environments requiring dimensional stability.

[0065] (2) Mechanical property testing

[0066] Test Method: Tensile properties were tested according to the test conditions specified in national standard GB / T 1040.3. Type 5 dumbbell specimens were cut using a standard punch, with a parallel section width of 4 mm and a gauge length of 25 mm. At least five valid specimens were prepared for each group, cut along both the longitudinal and transverse directions. Before testing, the specimens were conditioned at 23±2℃ and 50±5%RH for at least 4 hours. A Class 1 universal testing machine conforming to GB / T16825.1, equipped with rubber-lined clamps, was used. The specimens were centered and clamped, with the long axis aligned with the direction of the tensile force, and stretched at a speed of 5 mm / min until fracture. The maximum force and gauge length elongation were recorded, and the tensile strength and elongation at break were calculated. The arithmetic mean of the results was taken.

[0067] The mechanical property test results are shown in Table 2:

[0068] Table 2. Mechanical property test results of Examples 1-6

[0069] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Tensile strength 0.51 MPa 0.25Mpa 0.22 MPa 0.26Mpa 0.30Mpa 0.55Mpa Elongation at break 109.23% 117.82% 135.64% 125.32% 140.71% 531.97%

[0070] As shown in Table 2, Figure 3-4 The mechanical property test results show that the thermosetting polyurea hydrogel films prepared in Examples 1-5 have good structural load-bearing capacity and moderate deformation buffering capacity, while effectively limiting excessive stretching.

[0071] Mechanical property test results show that the thermosetting polyurea hydrogel film prepared by this invention achieves precise performance customization by controlling the isocyanate trimer structure: Examples 1-5 use hexamethylene diisocyanate trimer crosslinking, which, thanks to the flexibility of aliphatic linear chains and the regular network structure, exhibits tensile strength of 0.22~0.51 MPa and elongation at break of 109%~141%, demonstrating excellent dimensional stability and wide-range adjustability, thus helping to solve the application problems of scenarios with requirements for cost and shape retention; while Example 6 uses isophorone diisocyanate trimer crosslinking with an alicyclic structure to construct a unique "rigid-flexible" dual network. By utilizing rigid rings to reinforce the skeleton support and combining the "sacrificial bond" energy dissipation mechanism of dynamic hydrogen bonds between polyurea segments, the bottleneck of strength-toughness trade-off is successfully overcome, achieving a tensile strength of 0.22~0.51 MPa and elongation at break of 109%~141%. With a high tensile strength of MPa and an extraordinary elongation at break of 531.97%, this material effectively solves the technical problem of traditional hydrogels being prone to brittle fracture under large deformation. It exhibits good adaptability and application potential in dynamically changing physiological environments and flexible electronic devices that require large deformation.

[0072] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyurea hydrogel membrane, characterized in that, Includes the following steps: (1) The polyisocyanate trimer, blocking agent, solvent and catalyst were added to the reactor in sequence, the stirring was started and the temperature was raised to prepare the blocked polyisocyanate component. (2) Add the blocked polyisocyanate component to a certain proportion of deionized water, stir evenly, filter, and remove catalyst impurities; (3) The product obtained in step (2) is mixed with polyetheramine in a certain proportion and transferred to a vacuum drying oven. Small molecule impurities are removed at room temperature and under -0.1-0 MPa conditions for 36-48 hours to obtain a purified blocked polyisocyanate and polyetheramine composition. (4) The purified blocked polyisocyanate and polyetheramine composition is coated into a mold and heated to obtain a polyurea hydrogel film.

2. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that, In step (1): The polyisocyanate trimer is one or a mixture of two or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, isophthalimethylene diisocyanate trimer, and hydrogenated diphenylmethane diisocyanate trimer. The sealing agent is one or a mixture of two or more of the following: diethyl malonate, dimethyl malonate, diisopropyl malonate, di-tert-butyl malonate, ethyl acetoacetate, ethyl benzoyl, monoethyl malonate, diethyl methyl malonate, malonamide, and cyanoacetamide.

3. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that, In step (1): The solvent is one or a mixture of two or more of the following: acetone, butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol methyl ether acetate, and diethylene glycol diacetate. The catalyst is one or a mixture of two or more of the following: sodium methoxide, sodium ethoxide, potassium tert-butoxide, sodium tert-butoxide, potassium methoxide, sodium hydrogen, sodium hydroxide, lithium diisopropylamino, and lithium hexamethylenedisilamide.

4. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that: In step (1), the mass ratio of the polyisocyanate trimer, blocking agent, solvent and catalyst is (100-120): (100-120): (200-240):

1.

5. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that: In step (1), the temperature of the heating reaction is 70-75℃ and the reaction time is 7-8h.

6. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that: In step (2), 1-5 parts by weight of deionized water are added to every 100 parts by weight of the blocked polyisocyanate component.

7. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that, In step (3), the polyetheramine comprises any one or more mixtures that satisfy the following conditions: (a) Mean functionality ≥ 3.0; (b) All-ethylene oxide structure; (c) Average molecular weight ≥ 1000.

8. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that: In step (3), 20-80 parts by weight of blocked polyisocyanate component are added to every 100 parts by weight of polyetheramine.

9. The method for preparing a polyurea hydrogel membrane according to claim 1, characterized in that: In step (4), the heating temperature is 80-85℃ and the heating time is 5-6h.

10. A polyurea hydrogel membrane prepared by the method of any one of claims 1-9.

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