A kind of anti-corrosion polyurethane composite protective film for battery and preparation method thereof

Abstract

The present invention provides an anti-corrosion polyurethane composite protective film for a battery and a preparation method thereof, which belongs to the technical field of battery protection materials, and comprises the following steps: mechanically stirring and mixing fluorosilicone resin, polyurethane emulsion, propylene glycol methyl acetate, and triphenyl phosphite, ultrasonicating, and heating and dehydrating to obtain fluorosilicone / polyurethane emulsion; mixing methylated guar gum powder, hydrophobic nano-clay water suspension, nano-alumina and nano-titanium dioxide ethanol dispersion, ultrasonicating, and mechanically stirring to obtain methylated guar gum-based composite material; preparing fluorosilicone / polyurethane film by electrostatic spinning of fluorosilicone / polyurethane emulsion, adding polytetrahydrofuran diamine to methylated guar gum-based composite material, stirring, coating on fluorosilicone / polyurethane film, and standing and curing to obtain anti-corrosion polyurethane composite protective film. The present invention can protect the battery from corrosion while improving thermal stability and insulation.

Description

Technical Field

[0001] The present invention relates to the technical field of battery protection materials, and particularly relates to an anti-corrosion polyurethane composite protective film for batteries and a preparation method thereof. Background Art

[0002] Common battery outer shells are generally made of metal (such as steel, aluminum) materials. Under the action of ultraviolet rays, oxygen and moisture, the shells will be corroded, reducing the battery life. Therefore, a protective film for the battery outer shell is needed to protect it from water vapor and other substances in the air.

[0003] During the operation of the battery, heat is generated inside the battery. However, in the current prior art, the protective film for batteries often shrinks after being used for a period of time. This is because its thermal stability fails to meet the standard. In a high-temperature environment, due to poor heat resistance, the protective film softens and melts, affecting its performance and life, resulting in the failure of the protective film and increasing the risk of battery thermal runaway. Moreover, there are also certain problems with its surface hydrophobicity and water vapor barrier property.

[0004] Waterborne polyurethane is an environmentally friendly and inexpensive block copolymer that has attracted great attention in recent years. Its structure contains a two-phase domain, a rigid segment and a soft segment. The rigid chain segment ensures the spatial stability of waterborne polyurethane, while the soft chain segment provides good ionic conductivity after dissolving alkali metal salts. Based on its special microstructure, waterborne polyurethane has good mechanical strength, excellent thermal stability and the ability to form films easily. However, during the charge and discharge process of the battery, some corrosive gases such as hydrogen and acidic vapors are released. The chemical resistance of waterborne polyurethane is usually poor and may be eroded by these substances, resulting in the degradation or rupture of the film layer. Also, in order to prevent battery short circuits, improve the battery cycle life and safety issues, the protective film needs to have a certain insulating function. In summary, the protective film for batteries needs to have good thermal stability, corrosion resistance and insulation, and these requirements are often difficult to meet by a single-material protective film.

[0005] Therefore, it is necessary to provide an anti-corrosion polyurethane composite protective film for batteries and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides an anti-corrosion polyurethane composite protective film and a preparation method thereof, which can protect the battery from corrosion while improving thermal stability and insulation.

[0007] To achieve the above object, the present invention provides a preparation method for an anti-corrosion polyurethane composite protective film for batteries, comprising the following steps:

[0008] Step S1: Mechanically stir and mix fluorosilicone resin, polyurethane emulsion, propylene glycol methyl ether acetate, and triphenyl phosphite evenly, perform ultrasonic treatment, and heat for dehydration to obtain a fluorosilicone / polyurethane emulsion;

[0009] Step S2: After mixing methylated guar gum powder, hydrophobic nano-clay aqueous suspension, nano-alumina alcohol dispersion, and nano-titanium dioxide by stirring, perform ultrasonic treatment and mechanical stirring to obtain a methylated guar gum-based composite material;

[0010] Step S3: After preparing a fluorosilicone / polyurethane film by electrospinning the fluorosilicone / polyurethane emulsion, add polytetrahydrofuran diamine to the methylated guar gum-based composite material, stir, coat it on the fluorosilicone / polyurethane film, and then stand for curing to obtain an anti-corrosion polyurethane composite protective film.

[0011] In the present invention, a fluorosilicone / polyurethane emulsion is prepared by mixing fluorosilicone resin and polyurethane emulsion; the Si-O bond with high bond energy in the fluorosilicone resin endows it with excellent thermal stability, the fluorocarbon chain can effectively reduce the surface tension of the material, and the high bond energy of the C-F bond makes it not easy to break at high temperatures. The strong electronegativity of fluorine atoms makes the C-F bond have extremely high hydrophobicity and electrical insulation properties. Fluorine-containing polymers show high inertness in many chemical environments. Therefore, adding fluorosilicone resin to the polyurethane emulsion can effectively improve its overall insulation, thermal stability, and corrosion resistance; however, due to the difference in solubility parameter values, the compatibility between fluorosilicone resin and polyurethane emulsion is poor, and phase separation will occur during blending, forming an unstable mixture. During the preparation of the fluorosilicone / polyurethane emulsion, propylene glycol methyl ether acetate is added as a solvent to improve the dispersion of fluorosilicone resin in the whole system and enhance the compatibility between fluorosilicone resin and polyurethane emulsion. Triphenyl phosphite is used as a heat stabilizer to improve the stability of the polymer under high-temperature conditions and prevent its thermal degradation.

[0012] In the present invention, a methylated guar gum-based composite material is prepared as the outer layer film, using the bio-based material methylated guar gum mixed with nano-clay as the base material. Since the hydrophilic guar gum and the hydrophobic nano-clay have poor compatibility and uneven dispersion, methylated guar gum is used. The presence of hydrophobic methyl groups increases the interaction with the hydrophobic groups in the hydrophobic nano-clay, thereby improving the tensile strength and elongation at break of the prepared nano-composite material, and also making the overall structure more compact and improving the barrier properties to water vapor, oxygen, etc.; in addition, nano-clay itself is an insulating material with a low conductivity, further improving the overall insulation performance. Nano-alumina and nano-titanium dioxide are added as fillers to the composite base material. Among them, nano-alumina has a stable surface and corrosion resistance and is not easily eroded by chemical substances. Titanium dioxide has good antibacterial, antioxidant, and ultraviolet resistance effects, which can reduce the yellowing coefficient of the protective film and further improve the anti-corrosion and antioxidant effects.

[0013] The anti-corrosion polyurethane composite protective film prepared by the present invention adopts a double-layer film composite structure. The inner layer film is prepared by electrospinning technology using the prepared fluorosilicon / polyurethane emulsion to prepare a fluorosilicon / polyurethane protective film with good insulation, thermal stability and certain corrosion resistance. Using electrospinning to prepare the anti-corrosion film replaces the high-temperature hot pressing preparation process, avoiding the risk of water molecules invading the battery surface due to fractures in the film at high temperatures. Using polytetrahydrofuran diamine as a curing agent and mixing it with a methylated guar gum-based composite material and then coating it on the surface of the inner layer film as the outer layer film, which improves the water resistance and further enhances the overall corrosion resistance.

[0014] Optionally, in step S1, a polyester resin is further added before mechanical stirring. The speed of mechanical stirring is 25 rpm, the time is 1 - 2 h, the time of ultrasonic treatment is 10 - 20 min, and the temperature of heating and dehydration is 160°C - 200°C, and the time is 3 - 5 h.

[0015] Optionally, the methylated guar gum powder in step S2 is prepared by mixing a 1% aqueous solution of guar gum, sodium hydroxide, and methyl iodide under a nitrogen inert atmosphere and stirring for 2.5 - 3 h, then adding acetic acid to adjust the pH value of the solution to 7.0, adding acetone, filtering to retain the precipitate, washing 3 times with a 50% acetone solution, and then freeze-drying.

[0016] In the present invention, guar gum is modified by using methyl iodide. During the methylation process, the methyl (-CH 3 ) group replaces some hydroxyl groups in the guar gum molecule through a substitution reaction, introducing hydrophobic methyl groups while reducing the -OH groups. This also reduces the sites where hydrogen bonds can be formed, causing the affinity of the material for water to decrease while reducing the disorder caused by hydrogen bonds and making the intermolecular arrangement tighter, thereby enhancing the overall thermal stability. A small amount of un-methylated guar gum has a certain adhesiveness, which can improve the interlayer adhesion effect of the composite material.

[0017] Optionally, in step S2, hyperbranched graphene oxide is further added before mixing and stirring.

[0018] In the present invention, hyperbranched graphene oxide is added as a filler to the methylated guar gum-based composite matrix. Among them, compared with ordinary graphene, graphene oxide with a high degree of oxidation usually exhibits good electrical insulation. The oxygen-containing functional groups of graphene oxide will destroy the original π-electron conjugate system of graphene, resulting in a significant decrease in electrical conductivity, thereby endowing the material with good insulation performance. Hyperbranched treatment improves graphene oxide, making the graphene oxide sheets combine more tightly with nano-aluminum oxide, nano-titanium dioxide, and the matrix, improving the interfacial force, and further improving the water resistance and insulation of the methylated guar gum-based composite material.

[0019] Optionally, the hyperbranched graphene oxide is prepared by stirring and mixing graphene oxide sheet suspension and γ-glycidoxypropyltrimethoxysilane, adding acetic acid solution with a concentration of 66.7%, reacting at 75 °C for 24 h, and then drying at 24 °C for 40 h; the graphene oxide sheet suspension is prepared by dispersing graphene oxide sheets in anhydrous ethanol solution and ultrasonically treating for 20 min.

[0020] In order to enable the graphene oxide sheets to better combine with the body, the present invention uses γ-glycidoxypropyltrimethoxysilane (KH-560) as the hyperbranched polysiloxane. Its molecular structure contains multiple functional groups, enabling the formation of a highly branched network during the polymerization process. The hyperbranched polysiloxane is grafted onto the graphene oxide sheets through acid hydrolysis to form hyperbranched graphene oxide.

[0021] Optionally, in the step S2, the ultrasonic treatment time is 1 - 2 h, the mechanical stirring speed is 20 rpm, and the time is 30 - 60 min; the concentration of the hydrophobic nanoclay aqueous suspension in the step S2 is 5% - 10%, and the type of the nanoclay in the hydrophobic nanoclay aqueous suspension is Cloisite 20A.

[0022] In the present invention, the concentration of the hydrophobic nanoclay aqueous suspension being 5% - 10% has the best effect. An excessively high concentration of the hydrophobic nanoclay aqueous suspension will reduce the overall tensile strength. The hydrophobic clay is used to improve the overall hydrophobicity and reduce the water vapor transmission rate.

[0023] Optionally, in the step S3, the electrospinning time is 2 h, the fluorosilicon / polyurethane film after electrospinning is dried under natural conditions for 12 - 24 h, the stirring time is 15 - 20 min, and the temperature for static curing is 20 - 30 °C and the time is 32 - 48 h.

[0024] Optionally, a corrosion - resistant polyurethane composite protective film for a battery includes the following raw materials in parts by weight: 3 - 5 parts of fluorosilicon / polyurethane emulsion, 0.2 - 0.8 part of polytetrahydrofuran diamine, and 3 - 7 parts of methylated guar gum - based composite material.

[0025] Optionally, the raw materials of the fluorosilicon / polyurethane emulsion include 20 - 50 parts of fluorosilicon resin, 40 - 60 parts of polyurethane emulsion, 40 parts of propylene glycol methyl acetate, and 5 parts of triphenyl phosphite calculated by weight; the raw materials of the methylated guar gum - based composite material include 10 - 20 parts of methylated guar gum powder, 65 - 80 parts of hydrophobic nanoclay aqueous suspension, and 10 - 15 parts of ethanol dispersion of nano - alumina and nano - titania calculated by weight.

[0026] Optionally, the raw materials of the methylated guar gum powder include 250 parts of guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of methyl iodide calculated by weight.

[0027] The above technical solutions of the present invention at least include the following beneficial effects:

[0028] The present invention adds fluorosilicone resin to the polyurethane suspension to improve its overall insulation, thermal stability, and corrosion resistance. Using propylene glycol methyl ether acetate as a solvent can improve the dispersibility of fluorosilicone resin in the whole system, enhance the compatibility between fluorosilicone resin and polyurethane emulsion, and triphenyl phosphite as a heat stabilizer can improve the stability of the polymer under high-temperature conditions and prevent its thermal degradation.

[0029] The present invention prepares a methylated guar gum-based composite material as the outer layer film. Among them, the interaction between the hydrophobic methyl groups in methylated guar gum and the hydrophobic groups in hydrophobic nano-clay increases, making the overall structure more compact, further improving the tensile strength, elongation at break of the prepared nano-composite material, and the barrier properties against water vapor, oxygen, etc. Nano-aluminum oxide and nano-titanium dioxide as fillers can further improve the anti-corrosion and anti-oxidation effects.

[0030] The anti-corrosion polyurethane composite protective film prepared by the present invention adopts a double-layer film composite structure. The inner layer film is a fluorosilicone / polyurethane protective film. Using electrospinning to prepare instead of the high-temperature hot pressing preparation process can avoid the risk of water molecules invading the battery surface due to fractures in the film at high temperatures. Using polytetrahydrofuran diamine as a curing agent to coat and prepare the methylated guar gum-based composite material as the outer layer film can improve the water resistance and further enhance the overall corrosion resistance. Specific Embodiments

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0032] Preparation work: Add 1 part of nano-aluminum oxide and 1 part of nano-silicon dioxide to 10 parts of anhydrous ethanol solution, and ultrasonically treat for 20 min to prepare an ethanol dispersion of nano-aluminum oxide and nano-titanium dioxide.

[0033] Example 1

[0034] 25 parts of fluorosilicone resin, 60 parts of polyurethane suspension, 40 parts of propylene glycol methyl ether acetate, and 5 parts of triphenyl phosphite were mechanically stirred at a speed of 25 rpm for 1.5 h to be mixed evenly. After introducing ultrasonic treatment at a frequency of 20 kHz and a power of 1.5 kW for 10 min, it was heated to 180 °C and dehydrated for 4 h to obtain a fluorosilicone / polyurethane emulsion.

[0035] 1 part of graphene oxide sheets was added to 10 parts of anhydrous ethanol solution and ultrasonically treated for 20 min to obtain a graphene oxide sheet suspension; 8 parts of the graphene oxide sheet suspension and 5 parts of γ-glycidoxypropyltrimethoxysilane (KH-560) were stirred for 15 min to be mixed evenly. A 66.7% acetic acid solution was slowly added dropwise to the solution. After adjusting the pH value to about 5, it was reacted at 75 °C for 24 h and then dried at 24 °C for 40 h to obtain hyperbranched graphene oxide; 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of methyl iodide were mixed and stirred in an inert nitrogen atmosphere for 2.5 h. Then acetic acid was added to adjust the pH value of the solution to 7.0. 250 parts of acetone was added to precipitate the synthesis product. The precipitate was washed 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze-dried to obtain methylated guar gum powder; 15 parts of methylated guar gum powder was dissolved in 45 parts of 7% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A). 8 parts of an ethanol dispersion of nanoaluminum oxide and nanosilicon dioxide and 0.2 part of hyperbranched graphene oxide were added. After ultrasonic treatment for 1 h, it was mechanically stirred at a speed of 20 rpm at room temperature for 30 min to obtain a methylated guar gum-based composite material.

[0036] 3.5 parts of the fluorosilicone / polyurethane emulsion was injected into a 10 ml syringe and installed on an injection pump. A catheter was connected through a female Luer connector, and a spinning nozzle was connected through a male Luer connector. At the same time, the spinning nozzle was clamped on a high-voltage power supply and adjusted to a suitable position. Subsequently, the spinning substrate aluminum foil was wrapped around the drum of the spinning receiving device. The spinning parameters were set as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, drum-type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and stable spinning for 2 h; the electrospun film was dried under natural conditions for 24 h to allow the solvent in the film to completely volatilize, obtaining a fluorosilicone / polyurethane film.

[0037] 0.4 part of polytetrahydrofuran diamine was added to 4 parts of the methylated guar gum-based composite material. Then it was gently stirred at room temperature for 20 min, and then brushed at 180 g / m 2After being coated on the fluorosilicon / polyurethane film at a coating rate of, it was left to cure at 30 °C for 48 h to obtain a corrosion - resistant polyurethane composite protective film.

[0038] Example 2

[0039] 50 parts of fluorosilicon resin, 60 parts of polyurethane suspension, 40 parts of propylene glycol methyl ether acetate, and 5 parts of triphenyl phosphite were mechanically stirred at a speed of 25 rpm for 2 h to be mixed evenly. After being treated with ultrasonic waves at a frequency of 20 kHz and a power of 1.5 kW for 20 min, it was heated to 200 °C for 5 h for dehydration treatment to obtain a fluorosilicon / polyurethane emulsion.

[0040] 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of iodomethane were mixed and stirred in an inert nitrogen atmosphere for 3 h. Then acetic acid was added to adjust the pH value of the solution to 7.0. After adding 250 parts of acetone to precipitate the synthesis product, the precipitate was washed 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze - dried to obtain methylated guar gum powder; 20 parts of methylated guar gum powder was dissolved in 80 parts of a 20% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A). 10 parts of an ethanol dispersion of nano - alumina and nano - titanium dioxide was added. After ultrasonic treatment for 2 h, it was mechanically stirred at a speed of 20 rpm at room temperature for 60 min to obtain a methylated guar gum - based composite material.

[0041] 5 parts of fluorosilicon / polyurethane emulsion was injected into a 10 - ml syringe and installed on an injection pump. The catheter was connected through a female Luer connector, and then the spinning nozzle was connected through a male Luer connector. At the same time, the spinning nozzle was clamped on the high - voltage power supply and adjusted to a suitable position. Subsequently, the spinning substrate aluminum foil was wrapped around the drum of the spinning receiving device. The spinning parameters were set as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, drum - type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and stable spinning for 2 h; The electrospun film was dried under natural conditions for 24 h to completely volatilize the solvent in the film to obtain a fluorosilicon / polyurethane film.

[0042] 0.5 part of polytetrahydrofuran diamine was added to 5 parts of methylated guar gum - based composite material, and then gently stirred at room temperature for 20 min. Then, it was brushed at a coating rate of 180 g / m 2 After being coated on the fluorosilicon / polyurethane film at a coating rate of, it was left to cure at 30 °C for 48 h to obtain a corrosion - resistant polyurethane composite protective film.

[0043] Example 3

[0044] Mix 40 parts of fluorosilicone resin, 20 parts of polyester resin, 30 parts of polyurethane suspension, 40 parts of propylene glycol methyl ether acetate, and 5 parts of triphenyl phosphite evenly by mechanical stirring at a speed of 25 rpm for 1.5 h. After introducing ultrasonic treatment at a frequency of 20 kHz and a power of 1.5 kW for 15 min, heat it to 180 °C and perform dehydration treatment for 4 h to obtain a fluorosilicone / polyurethane emulsion.

[0045] Mix 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of methyl iodide under a nitrogen inert atmosphere and stir for 2.5 h. Then, adjust the pH value of the solution to 7.0 by adding acetic acid. After adding 250 parts of acetone to precipitate the synthesis product, wash the precipitate 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze-dry to obtain methylated guar gum powder; dissolve 10 parts of methylated guar gum powder in 25 parts of a 10% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A), add 10 parts of an ethanol dispersion of nanoaluminum oxide and nanosilicon dioxide, perform ultrasonic treatment for 1.2 h, and then mechanically stir at a speed of 20 rpm at room temperature for 30 min to obtain a methylated guar gum-based composite material.

[0046] Inject 4 parts of the fluorosilicone / polyurethane emulsion into a 10 ml syringe, install it on an injection pump, connect a catheter through a female Luer connector, and then connect a spinning nozzle through a male Luer connector. At the same time, clamp the spinning nozzle on a high-voltage power supply and adjust the nozzle to a suitable position. Subsequently, wrap the spinning substrate aluminum foil around the drum of the spinning receiving device. Set the spinning parameters as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, drum-type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and spin stably for 2 h; place the electrospun film in natural conditions and dry it for 16 h to completely volatilize the solvent in the film to obtain a fluorosilicone / polyurethane film.

[0047] Add 0.2 part of polytetrahydrofuran diamine to 3 parts of the methylated guar gum-based composite material, then gently stir at room temperature for 17 min, and then coat it on the fluorosilicone / polyurethane film with a coating rate of 180 g / m 2 and cure it at 25 °C for 40 h to obtain an anti-corrosion polyurethane composite protective film.

[0048] Example 4

[0049] 35 parts of fluorosilicone resin, 50 parts of polyurethane suspension, 40 parts of propylene glycol methyl ether acetate, and 5 parts of triphenyl phosphite were mechanically stirred at a speed of 25 rpm for 1.5 h to be uniformly mixed. After introducing ultrasonic treatment at a frequency of 20 kHz and a power of 1.5 kW for 18 min, it was heated to 170 °C and dehydrated for 4.5 h to obtain a fluorosilicone / polyurethane emulsion.

[0050] 1 part of graphene oxide sheets was added to 10 parts of anhydrous ethanol solution, and ultrasonic treatment was carried out for 20 min to obtain a graphene oxide sheet suspension; 8 parts of the graphene oxide sheet suspension and 5 parts of γ-glycidoxypropyltrimethoxysilane (KH-560) were stirred for 15 min to be mixed evenly. A 66.7% acetic acid solution was slowly added dropwise to the solution. After adjusting the pH value to about 5, the reaction was carried out at 75 °C for 24 h, and then dried at 24 °C for 40 h to obtain hyperbranched graphene oxide; 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of methyl iodide were mixed and stirred in a nitrogen inert atmosphere for 3 h, then acetic acid was added to adjust the pH value of the solution to 7.0. 250 parts of acetone was added to precipitate the synthesis product, and the precipitate was washed 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze-dried to obtain methylated guar gum powder; 13 parts of methylated guar gum powder was dissolved in 40 parts of an 8% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A), 8 parts of an ethanol dispersion of nanoaluminum oxide and nanotitanium dioxide and 0.2 part of hyperbranched graphene oxide were added. After ultrasonic treatment for 1.5 h, it was mechanically stirred at a speed of 20 rpm at room temperature for 55 min to obtain a methylated guar gum-based composite material.

[0051] 3.5 parts of the fluorosilicone / polyurethane emulsion was injected into a 10 ml syringe and installed on an injection pump. The catheter was connected through a female Luer connector, and then the spinning nozzle was connected through a male Luer connector. At the same time, the spinning nozzle was clamped on the high-voltage power supply, and the nozzle was adjusted to a suitable position. Subsequently, the spinning substrate aluminum foil was wrapped around the drum of the spinning receiving device. The spinning parameters were set as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, drum-type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and stable spinning for 2 h; the electrospun film was dried under natural conditions for 20 h to completely volatilize the solvent in the film, and a fluorosilicone / polyurethane film was obtained.

[0052] 0.6 part of polytetrahydrofuran diamine was added to 4 parts of the methylated guar gum-based composite material, and then gently stirred at room temperature for 18 min. Then, it was brushed at 180 g / m 2After coating on the fluorosilicon / polyurethane film at a coating rate of, it was left to cure at 25 °C for 36 h to obtain a corrosion - resistant polyurethane composite protective film.

[0053] Example 5

[0054] 30 parts of fluorosilicon resin, 60 parts of polyurethane suspension, 40 parts of propylene glycol methyl acetate, and 5 parts of triphenyl phosphite were mechanically stirred at a speed of 25 rpm for 2 h to mix evenly. After introducing ultrasonic treatment at a frequency of 20 kHz and a power of 1.5 kW for 16 min, it was heated to 170 °C and dehydrated for 4.5 h to obtain a fluorosilicon / polyurethane emulsion.

[0055] 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of iodomethane were mixed and stirred in a nitrogen inert atmosphere for 3 h. Then, acetic acid was added to adjust the pH value of the solution to 7.0. After adding 250 parts of acetone to precipitate the synthetic product, the precipitate was washed 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze - dried to obtain methylated guar gum powder; 16 parts of methylated guar gum powder was dissolved in 40 parts of a 7% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A). 12 parts of an ethanol dispersion of nano - alumina and nano - titanium dioxide was added. After ultrasonic treatment for 1.3 h, it was mechanically stirred at a speed of 20 rpm at room temperature for 45 min to obtain a methylated guar gum - based composite material.

[0056] 4.5 parts of fluorosilicon / polyurethane emulsion was injected into a 10 - ml syringe and installed on an injection pump. The catheter was connected through a female Luer connector, and then the spinning nozzle was connected through a male Luer connector. At the same time, the spinning nozzle was clamped on the high - voltage power supply and adjusted to a suitable position. Subsequently, the spinning substrate aluminum foil was wrapped around the roller of the spinning receiving device. The spinning parameters were set as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, roller - type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and stable spinning for 2 h; the electrospun film was dried under natural conditions for 24 h to completely volatilize the solvent in the film to obtain a fluorosilicon / polyurethane film.

[0057] 0.9 part of polytetrahydrofuran diamine was added to 7 parts of methylated guar gum - based composite material. Then, it was gently stirred at room temperature for 16 min, and then brushed at a coating rate of 180 g / m 2 After coating on the fluorosilicon / polyurethane film, it was left to cure at 30 °C for 45 h to obtain a corrosion - resistant polyurethane composite protective film.

[0058] Example 6

[0059] 20 parts of fluorosilicone resin, 40 parts of polyurethane suspension, 40 parts of propylene glycol methyl ether acetate, and 5 parts of triphenyl phosphite were mechanically stirred at a speed of 25 rpm for 1 h to be uniformly mixed. After being introduced with ultrasonic wave at a frequency of 20 kHz and a power of 1.5 kW for 10 min, it was heated to 160 °C and dehydrated for 3 h to obtain a fluorosilicone / polyurethane emulsion.

[0060] 1 part of graphene oxide sheets was added to 10 parts of anhydrous ethanol solution and ultrasonically treated for 20 min to obtain a graphene oxide sheet suspension; 8 parts of the graphene oxide sheet suspension and 5 parts of γ-glycidoxypropyltrimethoxysilane (KH-560) were stirred for 15 min to be uniformly mixed. A 66.7% acetic acid solution was slowly dropped into the solution. After adjusting the pH value to about 5, it was reacted at 75 °C for 24 h and then dried at 24 °C for 40 h to obtain hyperbranched graphene oxide; 250 parts of 1% guar gum aqueous solution, 6.25 parts of sodium hydroxide, and 2 parts of methyl iodide were mixed and stirred in an inert nitrogen atmosphere for 3 h. Then acetic acid was added to adjust the pH value of the solution to 7.0. 250 parts of acetone was added to precipitate the synthesis product, and the precipitate was washed 3 times with 200 parts of 50% acetone solution to remove any unreacted chemicals and salts formed during the neutralization process, and freeze-dried to obtain methylated guar gum powder; 12 parts of methylated guar gum powder was dissolved in 65 parts of a 6% hydrophobic nanoclay aqueous suspension (nanoclay model: Cloisite 20A), 10 parts of an ethanol dispersion of nanoaluminum oxide and nanosilicon dioxide and 0.5 part of hyperbranched graphene oxide were added. After ultrasonically treating for 1.2 h, it was mechanically stirred at a speed of 20 rpm at room temperature for 50 min to obtain a methylated guar gum-based composite material.

[0061] 3 parts of the fluorosilicone / polyurethane emulsion was injected into a 10 ml syringe and installed on an injection pump. A catheter was connected through a female Luer connector, and a spinning nozzle was connected through a male Luer connector. At the same time, the spinning nozzle was clamped on a high-voltage power supply and adjusted to a suitable position. Subsequently, the spinning substrate aluminum foil was wrapped around the roller of the spinning receiving device. The spinning parameters were set as follows: solution pushing speed 2.0 ml / h, spinning nozzle moving speed 2.3 mm / s, substrate spacing 14 cm, roller-type aluminum foil receiving substrate, rotation speed 235 r / min, spinning DC voltage 12.1 kV, and stable spinning for 2 h; the electrospun film was dried under natural conditions for 12 h to completely volatilize the solvent in the film to obtain a fluorosilicone / polyurethane film.

[0062] 0.8 part of polytetrahydrofuran diamine was added to 6 parts of the methylated guar gum-based composite material, and then gently stirred at room temperature for 15 min. Then it was coated on the fluorosilicone / polyurethane film with a coating rate of 180 g / m 2 and cured by standing at 20 °C for 32 h to obtain an anti-corrosion polyurethane composite protective film.

[0063] The present invention also carried out comparative examples and related tests.

[0064] Comparative Example 1

[0065] Compared with Example 1, the difference is only that the methylated guar gum-based composite material was not prepared as the outer layer film coated on the fluorosilicon / polyurethane film, but directly prepared by electrospinning from the fluorosilicon / polyurethane emulsion. The other components and preparation steps are exactly the same, and a corrosion-resistant polyurethane composite protective film was obtained.

[0066] Comparative Example 2

[0067] Compared with Example 2, the difference is only that the mixture of methylated guar gum powder and hydrophobic nanoclay aqueous suspension was directly used as the raw material for the outer layer film of the corrosion-resistant polyurethane composite protective film, and the ethanol dispersion of nano-alumina and nano-titanium dioxide was not added as a filler. The other components and preparation steps are exactly the same, and a corrosion-resistant polyurethane composite protective film was obtained.

[0068] Comparative Example 3

[0069] Compared with Example 1, the difference is only that the fluorosilicon / polyurethane emulsion was not prepared, and the inner layer film was directly prepared by electrospinning using the polyurethane emulsion. The other components and preparation steps are exactly the same, and finally a corrosion-resistant polyurethane composite protective film was obtained.

[0070] Comparative Example 4

[0071] Compared with Example 2, the difference is only that the methylated guar gum powder was not prepared, and the guar gum powder was directly used. The other components and preparation steps are exactly the same, and finally a corrosion-resistant polyurethane composite protective film was obtained.

[0072] Comparative Example 5

[0073] Compared with Example 2, the difference is only that the hydrophobic nanoclay aqueous suspension was not added. The other components and preparation steps are exactly the same, and finally a corrosion-resistant polyurethane composite protective film was obtained.

[0074] Comparative Example 6

[0075] Compared with Example 2, the difference is only that the fluorosilicon / polyurethane film was not prepared by electrospinning, but directly prepared by hot pressing at high temperature. The other components and preparation steps are exactly the same, and a corrosion-resistant polyurethane composite protective film was obtained.

[0076] The basic performance tests were carried out on the anti-corrosion polyurethane composite protective films for batteries prepared in Examples 1 to 6 and Comparative Examples 1 to 6. The total thickness, elongation at break, tensile strength, and density were tested according to the national standard of HG / T 5070-2016 Thermoplastic Polyurethane (TPU) Films. The requirements were elongation at break (%) ≥ 350 and tensile strength MPa ≥ 30.0; the yellowness index was tested according to the national standard of GB / T 36289.1-2018 Insulating Films for Crystalline Silicon Solar Cell Modules - Part 1: Polyester Films. The requirement was yellowness index (YI) ≤ 3.0. The results of the basic performance tests are shown in Table 1.

[0077] Table 1

[0078]

[0079] As can be seen from Table 1, Examples 1 to 6 all meet the national standards of HG / T 5070-2016 Thermoplastic Polyurethane (TPU) Films and GB / T 36289.1-2018 Insulating Films for Crystalline Silicon Solar Cell Modules - Part 1: Polyester Films. Combining the data in Table 1, it can be known that the yellowness coefficient of the anti-corrosion polyurethane composite protective film prepared in Comparative Example 1 due to the failure to prepare the methylated guar gum-based composite material as the outer layer film and Comparative Example 2 due to the failure to add the ethanol dispersion of nano-aluminum oxide and nano-titanium dioxide as the filler of the outer layer film has obvious defects; the basic performance of the anti-corrosion polyurethane composite protective film prepared by adding hyperbranched graphene oxide to the methylated guar gum-based composite material in Examples 1, 4, and 6 has also been improved.

[0080] The relevant performance tests were carried out on the anti-corrosion polyurethane composite protective films prepared in Examples 1 to 6 and Comparative Examples 1 to 6. The shrinkage rate, volume resistivity, and water vapor transmission rate were detected according to the national standard of GB / T 36289.1-2018 Insulating Films for Crystalline Silicon Solar Cell Modules - Part 1: Polyester Films. The oxygen transmission rate and ultraviolet light transmission rate were detected for relevant performance according to the national standard of GB / T 36289.2-2018 Insulating Films for Crystalline Silicon Solar Cell Modules - Part 2: Fluoroplastic Films. The water vapor transmission rate was detected with reference to the standard of HG / T 5877-2021 Thermoplastic Polyurethane (TPU) Pellets for Waterproof and Moisture Permeable Films. The oxygen transmission rate was tested according to the standard method of GB / T 19789-2021 Coulometer Detection Method for Oxygen Permeability Test of Packaging Materials - Plastic Films and Sheets. The results of the relevant performance tests are shown in Table 2.

[0081] Table 2

[0082]

[0083] As can be seen from Table 2, the heat resistance and insulation performance of the anti-corrosion polyurethane composite protective films prepared in Examples 1 to 6 are significantly higher than those of the anti-corrosion polyurethane composite protective films prepared in Comparative Examples 1 to 6; the transmittances of oxygen, water vapor and ultraviolet light are significantly lower than those in Comparative Examples 1 to 6.

[0084] Combined with the data in Table 2, by comparing Example 1 with Comparative Example 1, it can be seen that the anti-corrosion polyurethane composite protective film prepared in Comparative Example 1 without using the methylated guar gum-based composite material as the outer layer film has significantly higher transmittances of oxygen, water vapor and ultraviolet light than those in Example 1; by comparing Example 2 with Comparative Example 2, it can be seen that the anti-corrosion polyurethane composite protective film prepared due to the presence of nano-aluminum oxide and nano-titanium dioxide has a significantly increased volume resistivity and significantly reduced ultraviolet light transmittance; by comparing Example 1 with Comparative Example 3, it can be seen that using fluorosilicon / polyurethane as the inner layer film significantly improves the thermal stability, water resistance and insulation, and further improves the shrinkage rate, volume resistivity, and transmittances of oxygen, water vapor and ultraviolet light; by comparing Example 2 with Comparative Example 4, it can be seen that using unmethylated guar gum as the raw material for the outer layer film significantly increases the water vapor transmittance; by comparing Example 2 with Comparative Example 5, it can be seen that the resistivity of the outer layer film without adding nano-clay decreases significantly; by comparing Example 2 with Comparative Example 6, it can be seen that the volume resistivity, oxygen transmittance, ultraviolet light transmittance and water vapor transmittance performance of the anti-corrosion composite protective film prepared by electrospinning are significantly improved.

[0085] The anti-corrosion polyurethane composite protective films prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were tested for their resistance to acid, alkali and salt corrosion. The salt spray resistance was detected according to the test method of Ka: salt spray in Part 2: Test methods of environmental testing for electric and electronic products: GB / T 2423.17, the acid resistance was detected with reference to the detection method of GB / T 9274-1988, and the alkali resistance was detected according to the detection method of GB / T 9265-2009. The test results of related performances are shown in Table 3.

[0086] Table 3

[0087]

[0088] As can be seen from Table 3, the anti-corrosion polyurethane composite protective films prepared in Examples 1 to 6 have significantly higher resistance to acid, alkali and salt corrosion than those prepared in Comparative Examples 1 to 6.

[0089] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an anti-corrosion polyurethane composite protective film for a battery, characterized in that: The following steps are involved: Step S1, mixing fluorosilicone resin, polyurethane emulsion, propylene glycol methyl acetate, and triphenyl phosphite by mechanical stirring, ultrasonic treatment, heating and dehydration, to obtain fluorosilicone / polyurethane emulsion; Step S2, mixing and stirring the methylated guar gum powder, the hydrophobic nano-clay aqueous suspension, and the ethanol dispersion of nano-alumina and nano-titanium dioxide, ultrasonically treating, and mechanically stirring to obtain a methylated guar gum-based composite material; Step S3, after preparing a fluorosilicone / polyurethane film by electrostatic spinning of a fluorosilicone / polyurethane emulsion, adding polytetrahydrofuran diamine to the methylated guar gum-based composite material, stirring, coating the fluorosilicone / polyurethane film, and standing to cure to obtain an anti-corrosion polyurethane composite protective film.

2. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 1, characterized in that: In the step S1, polyester resin is added before mechanical stirring, the speed of mechanical stirring is 25 rpm, the time is 1-2 hours, the time of ultrasonic treatment is 10-20 minutes, the temperature of heating dehydration is 160° C.-200° C., and the time is 3-5 hours.

3. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 1, characterized in that: The methylated guar gum powder in step S2 is prepared by mixing and stirring a 1% guar gum aqueous solution, sodium hydroxide and methyl iodide under a nitrogen inert atmosphere for 2.5 to 3 hours, adding acetic acid to adjust the pH value of the solution to 7.0, adding acetone, filtering and retaining the precipitate, adding a 50% acetone solution to wash three times, and then freeze-drying.

4. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 1, characterized in that: In the step S2, hyperbranched graphene oxide is also added before mixing and stirring.

5. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 4, characterized in that: The hyperbranched graphene oxide is prepared by stirring and mixing a graphene oxide sheet suspension and γ-glycidyloxypropyltrimethoxysilane, adding an acetic acid solution with a concentration of 66.7%, reacting at 75°C for 24 hours, and drying at 24°C for 40 hours; the graphene oxide sheet suspension is prepared by dispersing graphene oxide sheets in an anhydrous ethanol solution and ultrasonically treating them for 20 minutes.

6. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 1, characterized in that: In the step S2, the ultrasonic treatment time is 1-2 hours, the mechanical stirring speed is 20 rpm, and the time is 30-60 minutes; the concentration of the hydrophobic nanoclay water suspension in the step S2 is 5%-10%, and the model of the nanoclay in the hydrophobic nanoclay water suspension is Cloisite 20A.

7. The method for preparing a corrosion-resistant polyurethane composite protective film for batteries according to claim 1, characterized in that: In step S3, the electrospinning time is 2 hours, the fluorosilicone / polyurethane film after electrospinning is placed under natural conditions to dry for 12 to 24 hours, the stirring time is 15 to 20 minutes, and the static curing temperature is 20 to 30° C. and the time is 32 to 48 hours.

8. An anti-corrosion polyurethane composite protective film for batteries, characterized in that: The anti-corrosion polyurethane composite protective film for batteries is prepared by the method for preparing the anti-corrosion polyurethane composite protective film for batteries according to any one of claims 1 to 7, characterized in that the anti-corrosion polyurethane composite protective film comprises the following raw materials in parts by weight: 3 to 5 parts of fluorosilicone / polyurethane emulsion, 0.2 to 0.8 parts of polytetrahydrofuran diamine, and 3 to 7 parts of methylated guar gum-based composite material.

9. The anti-corrosion polyurethane composite protective film for batteries according to claim 8, characterized in that: The raw materials of the fluorosilicone / polyurethane emulsion include 20-50 parts of fluorosilicone resin, 40-60 parts of polyurethane emulsion, 40 parts of propylene glycol methyl acetate, and 5 parts of triphenyl phosphite in parts by weight; the raw materials of the methylated guar gum-based composite material include 10-20 parts of methylated guar gum powder, 65-80 parts of hydrophobic nanoclay water suspension, and 10-15 parts of ethanol dispersion of nano-alumina and nano-titanium dioxide in parts by weight.

10. The anti-corrosion polyurethane composite protective film for batteries according to claim 9, characterized in that: The raw materials of the methylated guar gum powder include 250 parts of guar gum aqueous solution, 6.25 parts of sodium hydroxide and 2 parts of methyl iodide calculated by weight.

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