Preparation method of modified polyurethane swelling membrane

Abstract

The invention discloses a preparation method of a modified polyurethane swelling membrane, and belongs to the technical field of modified lithium battery materials. The method comprises the following steps: mixing polyurethane resin, MA-SEBS resin and novolac epoxy resin in a solvent in stages, adding an amino curing agent and a modified nano agent, and carrying out gradient stirring, filtering and vacuum defoaming to obtain a glue solution; and the film is formed through slit coating and a multi-section temperature control curing process. Wherein the modified nano agent is prepared from tannic acid, sodium metasilicate and zinc nitrate through glutaraldehyde crosslinking and hydrothermal crystallization, and a three-dimensional network structure is formed. The swelling membrane adopts a double-layer spiral-winch type stirring system and a ten-stage gradient curing procedure, the final membrane thickness is 40 + / -2 microns, and the solvent residual quantity is less than 2.8%. A traditional multi-step polycondensation process is simplified, the cost is reduced by adopting a one-step blending method, the method is suitable for three-dimensional gap filling of a cylindrical lithium battery cell, the anti-vibration performance is improved, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of modified lithium battery materials, and specifically relates to a preparation method of a modified polyurethane swelling film. Background Art

[0002] With the rapid development of the new energy industry, the application of lithium-ion batteries in fields such as electric vehicles and energy storage systems has shown explosive growth. Cylindrical lithium batteries dominate the power tool field due to their high packaging density and good mechanical stability. However, long-term high-frequency vibration easily causes displacement between the battery core and the housing. The swelling performance of traditional polyolefin separators in the electrolyte environment is insufficient, making it difficult to achieve effective void filling, which severely restricts the battery cycle life and safety. This technical bottleneck has given rise to the research and development demand for swelling functional materials. Among them, polyurethane materials have become a research hotspot in this field due to their unique rubbery cross-linked structure and adjustable swelling characteristics.

[0003] In the prior art, the research on polyurethane modification mainly focuses on the following three directions: (1) Chemical structure modification, such as the cyclodextrin / polybutadiene composite system disclosed in CN102743982A, which improves the thermal stability by introducing rigid chain segments, but its swelling rate is limited by the cross-linking density; (2) Physical blending modification, such as the use of ZIF-8 nanoparticles filling in CN109126485B. Although the separation factor is increased by 57%, the particle agglomeration leads to a decrease in mechanical strength; (3) Surface functionalization, the dopamine coating technology reported in the literature (Leng Xiaoyan. Preparation and desulfurization performance study of surface-modified pervaporation membranes [D]. Shandong: China University of Petroleum (East China), 2021.) enhances the polarity of the polyurethane membrane, but it is difficult to control the coating uniformity. While these methods improve specific properties, they often sacrifice other key indicators of the material system.

[0004] In the field of special swelling membranes for lithium batteries, the PVAC / SBS composite system developed in CN113072889A achieves a 40% volume expansion rate through physical blending, but brittle cracking occurs in a high-temperature environment; the phenyl polyether diol-modified TPU membrane designed in CN115028827A remains stable at 85°C, but the preparation process involves multiple stepwise polycondensation reactions, resulting in high industrialization costs. More notably, the prior art generally has the limitation of "two-dimensional swelling" - the material mainly swells in the thickness direction, and the lateral dimension change is less than 5%, making it difficult to meet the three-dimensional void filling requirements of cylindrical batteries.

[0005] In terms of material stability, traditional polyurethane membranes are prone to sol-gel transformation after long-term immersion in electrolytes. Although the dynamically crosslinked polyurethane gel electrolyte reported in the literature (DOI: 10.1039 / D2TA02239G) can achieve self-healing through hydrogen bond recombination, an excessively high crosslinking density reduces the initial swelling rate by 38%. This inverted relationship between "stability and swelling rate" has become the core contradiction restricting the improvement of material performance.

[0006] The complexity of the preparation process is also a pain point in the industry. The literature (DOI: 10.12677 / hjcet.2024.143022) reveals that the modification of waterborne polyurethane requires multiple processes such as prepolymer synthesis, chain extension, and emulsification, and the production cycle is as long as 48 hours. In addition, the problem of solvent residue is prominent. The literature (DOI: 10.3390 / membranes13040422) points out that there is still 2.8% solvent residue in commercial UHMWPE membranes after swelling in xylene, which seriously affects the battery safety.

[0007] From the perspective of material system innovation, recent research has mostly focused on alternative materials such as polyimide and PVDF. Although the PI membrane still maintains dimensional stability at 500 °C, its rigid molecular chain results in a swelling rate of less than 200% (http: / / www.cbea.com / gm / 201808 / 582773.html); after modification with nano-SiO 2 the thermal shrinkage rate of PVDF is reduced to 11.6% (https: / / www.ab-li.com / a / 7271), but the fluorocarbon chain segment has poor affinity with the electrolyte, and 15% PAN blending is required to meet the wetting requirements. While these alternative solutions solve specific problems, they often lead to new technical obstacles.

[0008] The common problems faced by those skilled in the art can be summarized as follows: (1) how to balance the negative correlation between the swelling rate and high-temperature stability; (2) molecular structure design for achieving three-dimensional directionally controllable swelling; (3) developing a preparation method with both simplicity in process and cost advantages; (4) solving the problem of performance attenuation caused by long-term infiltration of electrolytes. The existing technologies have not been able to systematically break through these bottlenecks, restricting the development process of high-reliability lithium batteries. Summary of the Invention

[0009] Problems to be Solved

[0010] The present invention aims to solve the following technical bottlenecks of existing polyurethane swelling membranes in the application of lithium batteries:

[0011] Contradiction between swelling performance and stability: There is an inverted relationship of "high swelling rate leading to low thermal stability" in traditional polyurethane membranes in electrolytes. For example, although the dynamic cross-linking system can improve self-healing properties, too high cross-linking density reduces the swelling rate by 38%. Although physical blending modification achieves a 40% volume expansion rate, it causes cyclic failure due to brittle cracking at high temperatures. Limitations of two-dimensional swelling: Existing materials mainly rely on swelling in the thickness direction (lateral dimension change < 5%), which cannot meet the three-dimensional void filling requirements between the cylindrical battery core and the housing. Complexity and cost of preparation processes: Existing technologies mostly rely on multi-step polycondensation or strict pH control, resulting in high industrialization costs. At the same time, solvent residues affect battery safety. Long-term electrolyte immersion attenuation: Traditional polyurethane membranes are prone to sol-gel transformation after long-term immersion in electrolytes, leading to a decrease in mechanical strength. Performance defects of alternative materials: The swelling rate of polyimide membranes is less than 200%. PVDF needs to be blended with 15% PAN to improve wettability, but the fluorocarbon chain segments have poor compatibility with electrolytes, causing an increase in interfacial impedance. The present invention systematically solves the above problems through material system innovation and process optimization, achieving three-dimensional controllable swelling, improved high-temperature stability, and simplified preparation processes.

[0012] Technical solution

[0013] To solve the above problems, the present invention adopts the following technical solution.

[0014] A preparation method of a modified polyurethane swelling film, comprising the following steps: Step S1, preparation of the modified polyurethane glue solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 5-10 parts by weight of MA-SEBS resin to the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 4-6 h, and then slowly add 15-20 parts by weight of phenolic epoxy resin to the reaction kettle, stir evenly for 10 min, and then slowly add 1.5-1.75 parts by weight of amino curing agent and 10-30 parts by weight of modified nano-agent to the reaction kettle. After stirring evenly for 20 min, filter and evacuate to remove bubbles to obtain the glue solution for use; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:(5-10), and add zinc nitrate 2-4 times the weight of tannic acid for stirring, then dissolve in ultrapure water 80-120 times the weight of tannic acid. Subsequently, an aqueous glutaraldehyde solution is added dropwise to the ultrapure water, and stirred vigorously for 6 h under dark conditions at a temperature of 35 °C, and the pH value is adjusted to 6.0 under vigorous stirring. Then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 10-15 times the weight of the brown product, transfer to a reaction kettle and react at 130-140 °C for 6-8 h. The obtained black product is freeze-dried under vacuum; Step S2, preparation of the modified polyurethane swelling film: The glue solution prepared in Step S1 is evenly coated onto a release film through a slit coater head (such as the MANS-TD-1500 coating die head produced by Shenzhen Mannst Technology Co., Ltd.). After drying and curing in an oven, it is wound up and the release film is peeled off to obtain it. Specifically, the winding tension is 15 N / m, the winding speed is 15 m / min, the contact pressure is 0.4 MPa, and the winding chip material is 6061 aluminum alloy (inner diameter 76 mm, wall thickness 5 mm).

[0015] Preferably, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the aqueous glutaraldehyde solution is 10%.

[0016] Preferably, the rotation speed of the vigorous stirring is 600 rpm.

[0017] Preferably, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; The GTMJ-BLD1-10 type equipment of Ruian Guotai Plastic Machinery Co., Ltd. can be selected.

[0018] The parameters of the upper-layer propeller are as follows: Three-blade propeller (30° inclination angle), 0.4D (D is the tank diameter), 316L stainless steel material, shear rate 50-100 s -1 .

[0019] The parameters of the lower-layer winch-type paddle are as follows: four-blade winch type (radial flow), 0.6D, 2205 duplex stainless steel, shear rate 20 - 50s -1 .

[0020] In step S1, the polyurethane resin is purchased from Lubrizol Corporation of the United States, and its product number is Tecothane TM TT - 1055D, with a molecular weight range of 200000 - 300000 g / mol, specific gravity of 1.23, tensile strength of 35 MPa, and elongation at break of 425%; in step S1, the MA - SEBS resin is purchased from Kraton Corporation of the United States, and its product number is Kraton TM FG1924G, with a molecular weight range of 40000 - 60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0021] Preferably, in step S1, the stirring speed during addition and stirring is 400 - 600 r / min; in step S1, the stirring temperature during addition and stirring is controlled at 30 - 40 °C.

[0022] Preferably, in step S1, the phenolic epoxy resin is purchased from Dow Chemical Company of the United States, and its product number is D.E.R. TM 672U, with an epoxy equivalent of 725 - 825 g / eq, softening point temperature of 110 - 120 °C, and melt viscosity of 4000 - 7000 cP at 150 °C.

[0023] Preferably, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy - 1,3,6 - trioxabicyclooctane, with a CAS number of 3006 - 08 - 4, purchased from Dow Chemical Company of the United States, product number DEH594, and amine value of 90 - 130 mgKOH / g.

[0024] Preferably, the filtration steps in step S1 are as follows: first, filter naturally with a 500 - mesh polyester filter screen, and then filter under pressure through a 1 - um filter element; the vacuum pumping time in step S1 is 20 - 30 min; the rotational viscosity of the glue solution in step S1 is 4000 - 5000 cps. Among them, the filtration efficiency verification is as follows: Equipment: Laser particle size analyzer (PSS AccuSizer FX - Nano, 0.15 - 200 μm), Method: Take glue solution samples before and after filtration, and detect the number of particles ≥0.5 μm (target residue ≤100 pieces / mL). Among them, the integrity test of the filter element is as follows: Bubble point test: The 1 - um filter element needs to be ≥0.35 MPa (ASTM F316 - 03), Diffusion flow test: ≤10 mL / min @ 80% bubble point pressure.

[0025] Preferably, in step S2, the release film is a 50-μm-thick transparent double-sided matte release film, with its substrate being polyethylene terephthalate, manufactured by Kay Premium Marking Films Company in the UK, product number KPMF-K74500, the release surface being the matte surface, and the release force being 70 g / 25 mm; the coating speed in step S2 is 10-15 m / min.

[0026] Preferably, in step S2, the temperature and time for oven drying and curing are sequentially set as 30°C / 1.5 min (initial film formation and shaping to prevent surface defects caused by rapid solvent evaporation), 50°C / 1.5 min (removing low-boiling solvents and controlling the residual solvent ≤5%), 70°C / 1.5 min (triggering the pre-crosslinking of phenolic epoxy resin to form a primary network structure), 90°C / 2 min (melting of MA-SEBS resin to enhance interfacial compatibility), 110°C / 2 min (activation start of amino curing agent for preliminary crosslinking), 130°C / 2 min (main curing stage I: formation of a dynamic crosslinking network), 150°C / 8 min (main curing stage II: irreversible crosslinking of borate bonds), 150°C / 6 min (eliminating internal stress and balancing the three-dimensional swelling structure), 150°C / 8 min (ensuring the residual solvent ≤2.8%), 110°C / 3 min (gradient cooling to prevent thermal stress cracks).

[0027] The thickness of the modified polyurethane swelling film prepared in step S2 is 40±2 μm, and the solvent residue is 2.5-2.8%.

[0028] Beneficial effects

[0029] The method and process involved in the present invention have the following multiple advantages:

[0030] (1) Excellent swelling performance: By introducing MA-SEBS resin and phenolic epoxy resin, the polyurethane swelling film of the present invention exhibits significant swelling ability in the electrolyte. Compared with traditional materials, the film swells uniformly in three-dimensional directions and can effectively fill the gap between the cylindrical lithium battery cell and the housing. This excellent swelling performance ensures that the cell is not easily displaced under high-frequency vibration environments, thereby improving the overall safety and stability of the battery. (2) High-temperature and high-humidity stability: The modified polyurethane swelling film prepared in the present invention can still maintain good performance under high-temperature and high-humidity conditions. By reasonably designing the molecular structure, the heat resistance and hydrolysis resistance of the material are improved, making it not easily undergo physical or chemical degradation in extreme environments. This characteristic is particularly important for high-frequency usage scenarios such as power tools and can effectively extend the service life of lithium batteries. (3) Simplified preparation process: The present invention adopts a simple and easy-to-operate preparation method, significantly reducing the production cost. Compared with the prior art, the method of the present invention has fewer steps, reduces the dependence on complex equipment and long reaction processes, making large-scale production possible. This advantage enables the modified polyurethane swelling film to be put into the market faster and meet the growing application demands of lithium batteries. (4) Environmentally friendly material: The DMF used in the present invention as a solvent can be effectively controlled and recycled during the preparation process, reducing environmental pollution. At the same time, by reasonably selecting raw materials, the safety of the product during use is ensured, reducing the potential risks to user health. This environmental protection characteristic conforms to the current global pursuit of sustainable development and green materials. (5) Enhancement of battery performance: By modifying the polyurethane material, the present invention not only improves the physical and chemical properties of the film material itself but also enhances its compatibility with the electrolyte. This improvement in compatibility enables the battery to better conduct ions during charge and discharge processes, increasing the energy density and cycle efficiency of lithium batteries, thereby enhancing the performance of the entire battery system. (6) Multifunctional application potential: The modified polyurethane swelling film is not only applicable to lithium batteries but can also be extended to other fields, such as electronic devices, sensors, and other application scenarios that require anti-vibration, isolation, or protection functions. This multifunctional characteristic provides broad application prospects for the future development of materials. (7) Significant economic benefits: Since the method adopted in the present invention has low production costs and high production efficiency, it can bring considerable economic benefits to enterprises. At the same time, due to its excellent performance and extensive application potential, the market demand will continue to grow, creating more business opportunities for related enterprises. In summary, the present invention provides a preparation method for a modified polyurethane swelling film, which not only achieves an innovative breakthrough in technology but also provides a new solution for the development of the lithium battery industry, with significant economic, social, and environmental benefits. Description of the Drawings

[0031] Figure 1It is a schematic diagram demonstrating the principle of the modified nanoagent loading prepared in Example 7 of the present invention.

[0032] Figure 2 It is the transmission electron microscope effect diagram of the modified nanoagent prepared in Example 7 of the present invention.

[0033] Figure 3 It is the X-ray photoelectron spectroscopy diagram of the modified nanoagent prepared in Example 7 of the present invention. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with specific embodiments.

[0035] Unless otherwise defined, the technical and scientific terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. In actual applications, the parts by weight or the ratio of parts by weight involved in the present invention can be set to the unit of kilogram.

[0036] Example 1

[0037] A preparation method of a modified polyurethane swelling film includes the following steps: Step S1, preparation of a modified polyurethane glue solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 5 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 4 h, and then slowly add 15 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, and then slowly add 1.5 parts by weight of amino curing agent and 10 parts by weight of the modified nanoagent into the reaction kettle. After stirring evenly for 20 min, filter and vacuum defoam to obtain a glue solution for standby; wherein the preparation method of the modified nanoagent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:5, and add zinc nitrate twice the weight of tannic acid for stirring, then dissolve in 80 times the weight of ultrapure water of tannic acid. Subsequently, drop the glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, and then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add 10 times the weight of water of the brown product, transfer to a reaction kettle and react at 130 °C for 8 h, and freeze-dry the obtained black product under vacuum.

[0038] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0039] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0040] Among them, the structure of the double-layer stirring paddle in step S1 is a spiral propeller in the upper layer and a winch type in the lower layer; the polyurethane resin in step S1 is purchased from Lubrizol Corporation of the United States, and its product number is Tecothane TM TT-1055D, with a molecular weight range of 200000-300000 g / mol, a specific gravity of 1.23, a tensile strength of 35 MPa, and an elongation at break of 425%; the MA-SEBS resin in step S1 is purchased from Kraton Corporation of the United States, and its product number is Kraton TM FG1924G, with a molecular weight range of 40000-60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0041] Among them, the stirring speed of adding while stirring in step S1 is 400 r / min; the stirring temperature of adding while stirring in step S1 is controlled at 40 °C.

[0042] Among them, the phenolic epoxy resin in step S1 is purchased from Dow Chemical Company of the United States, and its product number is D.E.R. TM 672U, with an epoxy equivalent of 725-825 g / eq, a softening point temperature of 110-120 °C, and a melt viscosity of 4000-7000 cP at 150 °C.

[0043] Among them, the amino curing agent in step S1 is β,β'-dimethylaminoethoxy-1,3,6-trioxabicyclooctane, its CAS number is 3006-08-4, purchased from Dow Chemical Company of the United States, product number DEH594, and the amine value is 90-130 mgKOH / g.

[0044] Among them, the steps of filtration in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the time for vacuum pumping in step S1 is 20 min; the rotational viscosity of the glue solution in step S1 is 5000 cps.

[0045] Step S2, preparation of the modified polyurethane swelling film: The glue solution prepared in step S1 is evenly coated on the release film through a slot die coater, dried and cured in an oven, and then wound up and peeled off the release film to obtain it.

[0046] Among them, the release film in step S2 is a 50-μm thick transparent double-sided matte release film, its base material is polyethylene terephthalate, the manufacturer is Kay Premium Marking Films Company of the United Kingdom, product number KPMF-K74500, the release surface is on the matte surface, and the release force is 70 g / 25 mm; the coating speed in step S2 is 10 m / min.

[0047] Among them, the temperature and time for oven drying and curing in step S2 are set as 30°C / 1.5 min, 50°C / 1.5 min, 70°C / 1.5 min, 90°C / 2 min, 110°C / 2 min, 130°C / 2 min, 150°C / 8 min, 150°C / 6 min, 150°C / 8 min, 110°C / 3 min in sequence; the solvent residue of the modified polyurethane swelling film prepared in step S2 is 2.8%.

[0048] Example 2

[0049] A preparation method of a modified polyurethane swelling film includes the following steps: Step S1, preparation of a modified polyurethane adhesive solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless-steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 5 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 4 h, then slowly add 15 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, then slowly add 1.5 parts by weight of amino curing agent and 10 parts by weight of modified nano-agent into the reaction kettle, stir evenly for 20 min, and then obtain the adhesive solution after filtration, vacuum pumping, and defoaming for standby; the preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:5, and add zinc nitrate twice the weight of tannic acid for stirring, then dissolve in ultrapure water 80 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions at a temperature of 35°C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 10 times the weight of the brown product, transfer it to the reaction kettle and react at 130°C for 6 h, and freeze-dry the obtained black product under vacuum.

[0050] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0051] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0052] Among them, the structure of the double-layer stirring paddle in step S1 is a propeller on the upper layer and a winch type on the lower layer; the polyurethane resin in step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, with a molecular weight range of 200000 - 300000 g / mol, a specific gravity of 1.23, a tensile strength of 35 MPa, and an elongation at break of 425%; the MA-SEBS resin in step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TMFG1924G, with a molecular weight range of 40,000 - 60,000 g / mol and a grafting rate of maleic anhydride at 1.5%.

[0053] Among them, the stirring speed during the addition and stirring in step S1 is 400 r / min; the stirring temperature during the addition and stirring in step S1 is controlled at 30 °C.

[0054] Among them, the phenolic epoxy resin in step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM 672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0055] Among them, the amino curing agent in step S1 is β,β'-dimethylaminoethoxy-1,3,6-trioxabicyclooctane, with a CAS number of 3006 - 08 - 4, purchased from Dow Chemical Company, USA, product number DEH594, and an amine value of 90 - 130 mgKOH / g.

[0056] Among them, the filtration steps in step S1 are as follows: first, naturally filter with a 500 - mesh polyester filter screen, and then pressurize and filter through a 1 - um filter element; the vacuum pumping time in step S1 is 20 min; the rotational viscosity of the adhesive solution in step S1 is 4000 cps.

[0057] Step S2, preparation of the modified polyurethane swelling film: The adhesive solution obtained in step S1 is evenly coated onto a release film through a slot - die coater, dried and cured in an oven, and then wound up and peeled off the release film to obtain it.

[0058] Among them, the release film in step S2 is a 50 - μm - thick transparent double - sided matte release film, with a substrate of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company, UK, product number KPMF - K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 10 m / min.

[0059] Among them, the temperature and time for drying and curing in the oven in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film obtained in step S2 is 2.8%.

[0060] Example 3

[0061] Preparation method of modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane glue solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 6 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 4.5 h, then slowly add 16 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, then slowly add 1.6 parts by weight of amino curing agent and 15 parts by weight of modified nano-agent into the reaction kettle, stir evenly for 20 min, and then obtain the glue solution after filtration and vacuum defoaming for standby; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:6, and add zinc nitrate 2.5 times the weight of tannic acid for stirring, then dissolve in ultrapure water 90 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 11 times the weight of the brown product, transfer to the reaction kettle and react at 133 °C for 6.5 h, and freeze-dry the obtained black product under vacuum to obtain.

[0062] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0063] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0064] Among them, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; the polyurethane resin in Step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, the molecular weight range is 200000 - 300000 g / mol, the specific gravity is 1.23, the tensile strength is 35 MPa, and the elongation at break is 425%; the MA-SEBS resin in Step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TM FG1924G, the molecular weight range is 40000 - 60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0065] Among them, the stirring speed of stirring while adding in Step S1 is 450 r / min; the stirring temperature of stirring while adding in Step S1 is controlled at 33 °C.

[0066] Among them, the phenolic epoxy resin in Step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0067] Among them, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy-1,3,6-trioxaborocane, with a CAS number of 3006-08-4, purchased from Dow Chemical Company, USA, with a product number of DEH594 and an amine value of 90 - 130 mgKOH / g.

[0068] Among them, the steps of filtration in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the time for vacuum pumping in step S1 is 23 min; the rotational viscosity of the adhesive liquid in step S1 is 4300 cps.

[0069] Step S2, preparation of the modified polyurethane swelling film: The adhesive liquid prepared in step S1 is evenly coated onto a release film through a slot die coater, dried and cured in an oven, and then wound up and peeled off the release film to obtain it.

[0070] Among them, in step S2, the release film is a 50-μm-thick transparent double-sided matte release film, with a base material of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company, UK, with a product number of KPMF-K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 12 m / min.

[0071] Among them, the temperature and time for oven drying and curing in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film prepared in step S2 is 2.7%.

[0072] Example 4

[0073] Preparation method of modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane glue solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 10 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 6 h, then slowly add 20 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, then slowly add 1.75 parts by weight of amino curing agent and 10 parts by weight of modified nano-agent into the reaction kettle, stir evenly for 20 min, and then obtain the glue solution after filtration and vacuum defoaming for standby; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:10, and add zinc nitrate 4 times the weight of tannic acid for stirring, then dissolve in ultrapure water 120 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 15 times the weight of the brown product, transfer to a reaction kettle and react at 140 °C for 6 h, and freeze-dry the obtained black product under vacuum to obtain it.

[0074] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0075] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0076] Among them, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; the polyurethane resin in Step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, the molecular weight range is 200000 - 300000 g / mol, the specific gravity is 1.23, the tensile strength is 35 MPa, and the elongation at break is 425%; the MA-SEBS resin in Step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TM FG1924G, the molecular weight range is 40000 - 60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0077] Among them, the stirring speed of stirring while adding in Step S1 is 600 r / min; the stirring temperature of stirring while adding in Step S1 is controlled at 30 °C.

[0078] Among them, the phenolic epoxy resin in Step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0079] Among them, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy-1,3,6-trioxabicyclooctane, with a CAS number of 3006-08-4, purchased from Dow Chemical Company in the United States, with a product number of DEH594 and an amine value of 90 - 130 mgKOH / g.

[0080] Among them, the filtration steps in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the vacuum pumping time in step S1 is 30 min; the rotational viscosity of the glue solution in step S1 is 4000 cps.

[0081] Step S2, preparation of the modified polyurethane swelling film: The glue solution prepared in step S1 is evenly coated onto a release film through a slot die coater, dried and cured in an oven, and then wound up and peeled off the release film to obtain it.

[0082] Among them, in step S2, the release film is a 50-μm-thick transparent double-sided matte release film, with a base material of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company in the UK, with a product number of KPMF-K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 15 m / min.

[0083] Among them, the temperature and time for oven drying and curing in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film prepared in step S2 is 2.8%.

[0084] Example 5

[0085] Preparation method of modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane glue solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 10 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir evenly for 6 h, then slowly add 20 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, then slowly add 1.75 parts by weight of amino curing agent and 30 parts by weight of modified nano-agent into the reaction kettle, stir evenly for 20 min, and then obtain the glue solution after filtration and vacuum defoaming for standby; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:10, and add zinc nitrate 4 times the weight of tannic acid for stirring, then dissolve in ultrapure water 120 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 15 times the weight of the brown product, transfer to a reaction kettle and react at 140 °C for 8 h, and freeze-dry the obtained black product under vacuum to obtain it.

[0086] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0087] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0088] Among them, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; the polyurethane resin in Step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, the molecular weight range is 200000-300000 g / mol, the specific gravity is 1.23, the tensile strength is 35 MPa, and the elongation at break is 425%; the MA-SEBS resin in Step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TM FG1924G, the molecular weight range is 40000-60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0089] Among them, the stirring speed of stirring while adding in Step S1 is 600 r / min; the stirring temperature of stirring while adding in Step S1 is controlled at 40 °C.

[0090] Among them, the phenolic epoxy resin in Step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0091] Among them, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy-1,3,6-trioxaborocane, with a CAS number of 3006 - 08 - 4, purchased from Dow Chemical Company, USA, with a product number of DEH594 and an amine value of 90 - 130 mgKOH / g.

[0092] Among them, the steps of filtration in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the time for vacuum pumping in step S1 is 30 min; the rotational viscosity of the adhesive solution in step S1 is 5000 cps.

[0093] Step S2, preparation of the modified polyurethane swelling film: The adhesive solution obtained in step S1 is evenly coated onto a release film through a slot die coater, dried and cured in an oven, and then wound and peeled off the release film to obtain it.

[0094] Among them, in step S2, the release film is a 50-μm-thick transparent double-sided matte release film, with a base material of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company, UK, with a product number of KPMF-K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 14 m / min.

[0095] Among them, the temperature and time for oven drying and curing in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film obtained in step S2 is 2.8%.

[0096] Example 6

[0097] Preparation method of modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane glue solution: Weigh accurately 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 9 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition is completed, stir uniformly for 5.5 h, then slowly add 19 parts by weight of phenolic epoxy resin into the reaction kettle, stir uniformly for 10 min, then slowly add 1.7 parts by weight of amino curing agent and 25 parts by weight of modified nano-agent into the reaction kettle, stir uniformly for 20 min, and then obtain the glue solution after filtration and vacuum defoaming for standby; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:9, and add zinc nitrate 3.5 times the weight of tannic acid for stirring, then dissolve in ultrapure water 110 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 14 times the weight of the brown product, transfer to the reaction kettle and react at 138 °C for 7.5 h, and freeze-dry the obtained black product under vacuum to obtain it.

[0098] Among them, the concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0099] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0100] Among them, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; the polyurethane resin in Step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, the molecular weight range is 200000 - 300000 g / mol, the specific gravity is 1.23, the tensile strength is 35 MPa, and the elongation at break is 425%; the MA-SEBS resin in Step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TM FG1924G, the molecular weight range is 40000 - 60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0101] Among them, the stirring speed of stirring while adding in Step S1 is 550 r / min; the stirring temperature of stirring while adding in Step S1 is controlled at 38 °C.

[0102] Among them, the phenolic epoxy resin in Step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0103] Among them, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy-1,3,6-trioxaborocane, with a CAS number of 3006 - 08 - 4, purchased from Dow Chemical Company in the United States, with a product number of DEH594 and an amine value of 90 - 130 mgKOH / g.

[0104] Among them, the filtration steps in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the vacuum pumping time in step S1 is 28 min; the rotational viscosity of the glue solution in step S1 is 4800 cps.

[0105] Step S2, preparation of the modified polyurethane swelling film: The glue solution obtained in step S1 is evenly coated onto a release film through a slot die coater, dried and cured in an oven, and then wound and peeled off the release film to obtain it.

[0106] Among them, in step S2, the release film is a 50-μm-thick transparent double-sided matte release film, with a base material of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company in the UK, with a product number of KPMF-K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 14 m / min.

[0107] Among them, the temperature and time for drying and curing in the oven in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film obtained in step S2 is 2.6%.

[0108] Example 7

[0109] Preparation method of modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane adhesive solution: Accurately weigh 400 parts by weight of N,N-dimethylformamide into a stainless steel reaction kettle with circulating cooling water, start the double-layer stirring paddle, and then slowly add 100 parts by weight of polyurethane resin and 8 parts by weight of MA-SEBS resin into the reaction kettle, stirring while adding. After the addition, stir evenly for 5 h, then slowly add 18 parts by weight of phenolic epoxy resin into the reaction kettle, stir evenly for 10 min, then slowly add 1.65 parts by weight of amino curing agent and 20 parts by weight of modified nano-agent into the reaction kettle, stir evenly for 20 min, and then obtain the adhesive solution after filtration and vacuum defoaming for standby; The preparation method of the modified nano-agent is as follows: Tannic acid and sodium metasilicate with a weight ratio of 1:8, and add zinc nitrate 3 times the weight of tannic acid for stirring, then dissolve in ultrapure water 100 times the weight of tannic acid, and then drop glutaraldehyde aqueous solution into the ultrapure water, stir vigorously for 6 h under dark conditions, the temperature is 35 °C, and adjust the pH value to 6.0 under vigorous stirring, then centrifuge at 6000 rpm for 20 min, collect the obtained brown product, add water 13 times the weight of the brown product, transfer to the reaction kettle and react at 135 °C for 7 h, and freeze-dry the obtained black product under vacuum to obtain it.

[0110] Among them, the concentration of the tannic acid is 0.3 g / mL; The final weight percentage of the glutaraldehyde aqueous solution is 10%.

[0111] Among them, the rotation speed of the vigorous stirring is 600 rpm.

[0112] Among them, the structure of the double-layer stirring paddle in Step S1 is a propeller on the upper layer and a winch type on the lower layer; The polyurethane resin in Step S1 is purchased from Lubrizol Corporation, USA, and its product number is Tecothane TM TT-1055D, the molecular weight range is 200000 - 300000 g / mol, the specific gravity is 1.23, the tensile strength is 35 MPa, and the elongation at break is 425%; The MA-SEBS resin in Step S1 is purchased from Kraton Corporation, USA, and its product number is Kraton TM FG1924G, the molecular weight range is 40000 - 60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

[0113] Among them, the stirring speed of stirring while adding in Step S1 is 500 r / min; The stirring temperature of stirring while adding in Step S1 is controlled at 35 °C.

[0114] Among them, the phenolic epoxy resin in Step S1 is purchased from Dow Chemical Company, USA, and its product number is D.E.R. TM672U, with an epoxy equivalent of 725 - 825 g / eq, a softening point temperature of 110 - 120 °C, and a melt viscosity of 4000 - 7000 cP at 150 °C.

[0115] Among them, in step S1, the amino curing agent is β,β'-dimethylaminoethoxy-1,3,6-trioxabicyclooctane, with a CAS number of 3006-08-4, purchased from Dow Chemical Company in the United States, product number DEH594, and an amine value of 90 - 130 mgKOH / g.

[0116] Among them, the steps of filtration in step S1 are as follows: first, naturally filter with a 500-mesh polyester filter screen, and then pressurize and filter through a 1-μm filter element; the vacuum pumping time in step S1 is 25 min; the rotational viscosity of the glue solution in step S1 is 4500 cps.

[0117] Step S2, preparation of the modified polyurethane swelling film: The glue solution obtained in step S1 is evenly coated onto a release film through a slot die coater, dried and cured in an oven, and then wound up and peeled off the release film to obtain it.

[0118] Among them, in step S2, the release film is a 50-μm thick transparent double-sided matte release film, with a base material of polyethylene terephthalate, manufactured by Kay Premium Marking Films Company in the UK, product number KPMF-K74500, the release surface is on the matte side, and the release force is 70 g / 25 mm; the coating speed in step S2 is 13 m / min.

[0119] Among them, the temperature and time for oven drying and curing in step S2 are set in sequence as 30 °C / 1.5 min, 50 °C / 1.5 min, 70 °C / 1.5 min, 90 °C / 2 min, 110 °C / 2 min, 130 °C / 2 min, 150 °C / 8 min, 150 °C / 6 min, 150 °C / 8 min, 110 °C / 3 min; the solvent residue of the modified polyurethane swelling film obtained in step S2 is 2.5%.

[0120] Comparative Example 1

[0121] Basically the same as Example 7, the difference is that: MA-SEBS resin is not used.

[0122] Comparative Example 2

[0123] Basically the same as Example 7, the difference is that: phenolic epoxy resin is not used.

[0124] Comparative Example 3

[0125] Basically the same as Example 7, the difference is that: zinc nitrate is not used in the modified nano-agent.

[0126] Comparative Example 4

[0127] Basically the same as Example 7, except that: sodium metasilicate is not used in the modified nano-agent.

[0128] Comparative Example 5

[0129] Basically the same as Example 7, except that: the modified nano-agent is not used.

[0130] Test Scheme

[0131] The thickness and electrolyte swelling rate of the modified polyurethane swelling films prepared in the above examples were detected.

[0132] Among them, the thickness test method is carried out in accordance with the standard of GB / T 7125-2014.

[0133] Among them, the volume swelling rate test method is as follows: first, cut the prepared modified polyurethane swelling films into 5 samples with a width of 50×50 mm. Use a film ruler to measure the length a1 and width b1 of the sample before swelling. Measure the thickness h1 of the sample after swelling in accordance with the standard of GB / T 7125-2014. Then immerse the sample in the electrolyte and bake it in an environment of 45°C, 50°C, 60°C, and 85°C for 4 h. Take out the sample and use a film ruler to measure the length a2 and width b2 of the sample after swelling. Measure the thickness h2 of the sample after swelling in accordance with the standard of GB / T 7125-2014. The volume swelling rate = (a2×b2×h2)÷(a1×b1×h1)×100%.

[0134] Among them, the mass swelling rate test method is as follows: first, cut the prepared modified polyurethane swelling films into 5 samples with a width of 25×50 mm. Use an analytical balance to accurately weigh the weight w1 of the sample before swelling. Then immerse the sample in the electrolyte and bake it in an environment of 45°C, 50°C, 60°C, and 85°C for 4 h. Take out the sample and use an analytical balance to accurately weigh the weight w2 of the sample after swelling. The mass swelling rate = w2÷w1×100%.

[0135] The modified polyurethane swelling films prepared in Examples 1-7 and Comparative Examples 1-5 were tested according to the above method, and the test results are shown in Table 1.

[0136] Table 1 Test Results

[0137]

[0138] Table 1 shows the thickness, volume swelling rate, and mass swelling rate of different example and comparative example samples at different temperatures. Generally speaking, the swelling performance of the examples is significantly better than that of the comparative example samples, especially under high temperature (85 °C) conditions. Thickness and swelling rate: The thickness of all examples is between 39.5 μm and 41.9 μm, indicating the consistency during the preparation process. Volume swelling rate: At 45 °C, 50 °C, 60 °C, and 85 °C, as the temperature increases, the swelling rate generally increases, which indicates that temperature has a positive effect on the swelling performance of the polyurethane film. The mass swelling rate also increases with the increase in temperature. Especially at 85 °C, the mass swelling rates of the examples all exceed 375%, showing good liquid absorption capacity. Example 7 has the most prominent swelling performance at all temperatures. Especially at 85 °C, its mass swelling rate reaches 725.4%, showing its excellent material properties.

[0139] The analysis of the comparative examples is as follows: At all test temperatures, the volume and mass swelling rates of Comparative Example 1 are significantly lower than those of the examples. Especially at 85 °C, its volume swelling rate is only 255.8%, and the mass swelling rate is 523.0%. This indicates that the lack of MA-SEB S resin results in insufficient liquid absorption capacity and inability to effectively fill the gap between the battery cell core and the housing. Comparative Example 2 shows dissolution at all temperatures, indicating that the material has extremely poor stability in the electrolyte and cannot maintain its shape. This further verifies the importance of MA-SEBS resin, and its absence directly leads to a serious decline in material performance. The volume and mass swelling rates of Comparative Examples 3-5 are significantly inferior to those of the examples. Especially for Comparative Examples 4 and 5, although the performance has improved, it still cannot be compared with the examples. These data indicate that it is difficult to meet the high-performance requirements in lithium battery applications relying solely on traditional polyurethane materials.

[0140] In summary, this study shows that by reasonably designing the polyurethane material system and optimizing process parameters, the performance of polyurethane films for lithium batteries can be significantly improved, thus meeting the stringent requirements of high-energy-density batteries for separator materials.

[0141] The preparation process of the modified nano-agent involves multiple chemical reactions and physical regulations, and its core mechanism is as follows:

[0142] Tannic Acid: Rich in catechol and pyrogallol structures, providing chelating sites to form stable complexes with metal ions (Zn 2+ ). Sodium metasilicate (Na 2 SiO 3 ): Hydrolyzes to generate silicic acid (H 4 SiO 4 ), and forms a silicon-oxygen network (Si-O-Si) through polycondensation reaction, providing an inorganic framework for nanoparticles. Zinc nitrate (Zn(NO 3 ))2 ): Zinc ions (Zn 2+ ) chelate with the phenolic hydroxyl groups of tannic acid to form a metal-organic framework (MOF) precursor. Glutaraldehyde: As a crosslinking agent, it reacts with the hydroxyl and amino groups of tannic acid to construct a covalent crosslinking network. For the steps of chelation and nucleation, tannic acid and Zn 2+ form a five-membered ring chelate under acidic conditions (pH ~ 6.0), reducing the oxidation potential of Zn 2+ and inhibiting hydrolysis. The silicic acid formed by the hydrolysis of sodium metasilicate polycondenses into SiO 2 nanoparticles (size ~ 20 nm), which adsorb on the surface of the tannic acid-Zn complex. For the steps of crosslinking and assembly, the aldehyde group of glutaraldehyde reacts with the phenolic hydroxyl group of tannic acid to form a Schiff base (-C=N- bond formation), and at the same time condenses with the surface hydroxyl group of silicic acid (Si-O-C bond) to form an organic-inorganic hybrid network. Vigorous stirring (600 rpm) promotes the homogeneous nucleation of nanoparticles and avoids agglomeration. For the step of hydrothermal crystallization, under high-pressure hydrothermal conditions of 130 - 140 °C, silicic acid further condenses into mesoporous SiO 2 (pore size ~ 5 nm), and the tannic acid-Zn chelate is embedded in the pore channels to form a hierarchical porous structure. Part of the zinc ions is reduced to ZnO nanocrystals, enhancing the photocatalytic performance of the material. The covalent bond (C-N) and hydrogen bond formed by tannic acid and glutaraldehyde constitute a reversible network, and bond recombination occurs in the electrolyte to achieve three-dimensional self-adaptive expansion.

[0143] In addition, taking the modified nanoagent in the preparation process of Example 7 as an example, as Figure 1 shown, the principle demonstration diagram of the successfully loaded modified nanoagent onto the modified polyurethane swelling membrane. At the same time, as Figure 2 shown, it shows the transmission electron microscope effect diagram of the modified nanoagent. In addition, as Figure 3 shown, X-ray photoelectron spectroscopy indicates the successful doping of Zn element.

[0144] This material can be widely applied to cylindrical batteries such as 18650 and 21700, and is particularly suitable for: High energy density batteries (>300Wh / kg): Reduce the risk of micro-short circuit of the battery cell through three-dimensional fixation, and the cycle life is increased to 2000 times (1C charge and discharge). Extreme working condition scenarios: Maintain the stability of expansion stress (fluctuation <10%) within a wide temperature range of -40°C to 85°C, and adapt to the high-frequency vibration requirements of outdoor energy storage and power tools. Intelligent manufacturing upgrade: Link the on-line thickness monitoring (±0.5μm) with the intelligent oven, and the yield is increased to 99.3% (97.5% for traditional processes). The modified polyurethane swelling film of the present invention systematically solves the "swelling-stability" contradiction in the fixation of lithium battery cells through molecular structure innovation and process innovation, provides key material support for high-safety and long-life cylindrical batteries, and at the same time has significant economic efficiency and environmental friendliness, and is expected to generate important industrial value in the fields of power batteries, energy storage systems, etc.

[0145] The above content further elaborates on the present invention in combination with specific implementation manners. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field of energy-saving and environmental protection building materials to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope determined by the claims submitted for the present invention.

Claims

1. A method for preparing a modified polyurethane swelling film, comprising the following steps: Step S1, preparation of modified polyurethane glue: accurately weigh 400 parts by weight of N,N-dimethylformamide in a stainless steel reactor with circulating cooling water, start a double-layer stirring paddle, then slowly add 100 parts by weight of polyurethane resin and 5-10 parts by weight of MA-SEBS resin to the reactor, stir while adding, and stir at a uniform speed for 4-6 hours after the addition is completed, then slowly add 15-20 parts by weight of phenolic epoxy resin to the reactor, stir at a uniform speed for 10 minutes, then slowly add 1.5-1.75 parts by weight of amino curing agent and 10-30 parts by weight of modified nano agent to the reactor, stir at a uniform speed for 20 minutes, filter, vacuumize and defoam to obtain glue, and set aside; wherein the preparation method of the modified nano agent is as follows: the weight ratio is 1: (5-10) Tannic acid and sodium metasilicate, and zinc nitrate 2-4 times the weight of tannic acid is added and stirred, then dissolved in ultrapure water 80-120 times the weight of tannic acid, then glutaraldehyde aqueous solution is added dropwise to the ultrapure water, vigorously stirred for 6 hours under dark conditions, the temperature is 35°C, and the pH value is adjusted to 6.0 under vigorous stirring, and then centrifuged at 6000rpm for 20min, the brown product is collected, 10-15 times the weight of the brown product is added with water, transferred to a reactor at 130-140°C for reaction for 6-8h, and the obtained black product is freeze-dried under vacuum; step S2, preparation of modified polyurethane swollen film: the glue prepared in step S1 is evenly coated on the release film through a slit coating head, and after being dried and cured in an oven, the release film is rolled up and peeled off to obtain the obtained product.

2. The method for preparing a modified polyurethane swellable film according to claim 1, characterized in that: The concentration of the tannic acid is 0.3 g / mL; the final weight percentage of the glutaraldehyde aqueous solution is 10%.

3. The method for preparing a modified polyurethane swellable film according to claim 2, characterized in that: The rotation speed of the vigorous stirring is 600 rpm.

4. The method for preparing a modified polyurethane swellable film according to claim 1, characterized in that: The double-layer stirring paddle in step S1 has an upper propeller and a lower capstan; the polyurethane resin in step S1 is purchased from Lubrizol Corporation of the United States, and its product number is Tecothane TM TT-1055D, molecular weight range is 200000-300000 g / mol, specific gravity is 1.23, tensile strength is 35 MPa, elongation at break is 425%; MA-SEBS resin in step S1 is purchased from Kraton, USA, and its product number is Kraton TM FG1924G, molecular weight range is 40000-60000 g / mol, and the grafting rate of maleic anhydride is 1.5%.

5. The method for preparing a modified polyurethane swellable film according to claim 4, characterized in that: The stirring speed of adding and stirring in step S1 is 400-600 r / min; the stirring temperature of adding and stirring in step S1 is controlled at 30-40°C.

6. The method for preparing a modified polyurethane swellable film according to claim 5, characterized in that: The phenolic epoxy resin in step S1 was purchased from Dow Chemical Company, USA, and its product number is DER TM 672U, epoxy equivalent is 725-825g / eq, softening point temperature is 110-120℃, melt viscosity at 150℃ is 4000-7000cP.

7. The method for preparing a modified polyurethane swellable film according to claim 6, characterized in that: The amino curing agent in step S1 is β,β'-dimethylaminoethoxy-1,3,6-trioxaboroctane, with a CAS number of 3006-08-4, purchased from Dow Chemical Company, USA, with a product number of DEH594 and an amine value of 90-130 mgKOH / g.

8. The method for preparing a modified polyurethane swellable film according to claim 7, characterized in that: The filtering steps in step S1 are as follows: first filter naturally with a 500-mesh polyester filter, and then filter under pressure through a 1um filter element; the vacuuming time in step S1 is 20-30 minutes; the rotational viscosity of the glue in step S1 is 4000-5000cps.

9. The method for preparing a modified polyurethane swellable film according to claim 1, characterized in that: The release film in step S2 is a 50 μm thick transparent double-sided matte release film, whose substrate is polyethylene terephthalate, the manufacturer is British Kay Premium Marking Films Company, the product number is KPMF-K74500, the release surface is the matte surface, and the release force is 70g / 25mm; the coating speed in step S2 is 10-15m / min.

10. The method for preparing a modified polyurethane swellable film according to claim 9, characterized in that: The temperature and time of oven drying and curing in step S2 are set to 30℃ / 1.5min, 50℃ / 1.5min, 70℃ / 1.5min, 90℃ / 2min, 110℃ / 2min, 130℃ / 2min, 150℃ / 8min, 150℃ / 6min, 150℃ / 8min, and 110℃ / 3min respectively; the thickness of the modified polyurethane swollen film obtained in step S2 is 40±2μm, and the residual solvent content is 2.5-2.8%.

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