Insulation protection methods for slurry, polyimide film, and cold plate for power battery packs, and cold plate for power battery packs with insulating protective film.

Abstract

This invention relates to the field of insulation protection for cold plates in power battery packs, and discloses a slurry, a polyimide film, an insulation protection method for a power battery pack cold plate, and a power battery pack cold plate with an insulating protective film. The slurry comprises an epoxy-acrylic hybrid resin, a photoinitiator, an active monomer, a curing agent, and additives; wherein, based on the total weight of the UV film, the content of the epoxy-acrylic hybrid resin is 60-85 wt%, the content of the photoinitiator is 1-5 wt%, the content of the active monomer is 10-30 wt%, the content of the curing agent is 0.5-5 wt%, and the content of the additives is 1-5 wt%. The slurry is coated onto at least one side of a biaxially oriented polyimide film to obtain a UV film. After UV curing, the polyimide film containing the UV film exhibits good temperature resistance, providing reliable insulation protection for the power battery pack cold plate even at 500°C, and also possesses high adhesive shear strength and adhesive peel strength for the power battery pack cold plate.

Description

Technical Field

[0001] This invention relates to the field of insulation protection for cold plates in power battery packs, specifically to a method for insulation protection of a slurry, a polyimide film, and a cold plate in a power battery pack, and a cold plate in a power battery pack having an insulating protective film. Background Technology

[0002] Traditional cold-pressed steel sheets for power battery packs typically only apply structural adhesive for insulation. However, this adhesive has poor temperature resistance and is prone to thermal decomposition when the battery fails (at temperatures up to 500°C), failing to provide effective insulation and posing a risk of arcing and fire to the battery pack. Furthermore, power battery pack cold-pressed steel sheets are usually large, exceeding 3 square meters. Traditional hot-press bonding processes have the following drawbacks: the required hot-pressing equipment is expensive (around 6 million RMB per set), production efficiency is low, large-area hot-pressing is prone to defects such as air bubbles, and the adhesion to the cold-pressed steel sheet is weak. Therefore, there is an urgent need for a material with good temperature resistance, high adhesive shear strength and adhesive peel strength to the cold-pressed steel sheet, a simple bonding process, and the ability to eliminate air bubble defects, suitable for insulation protection of power battery pack cold-pressed steel sheets. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of poor temperature resistance, weak adhesive shear strength and adhesive peel strength, easy generation of bubbles and other defects in the insulating protective film of the cold plate of the power battery pack, as well as the relatively complex bonding process in the prior art. The invention provides an insulating protection method for the slurry, polyimide film and the cold plate of the power battery pack, and a cold plate of the power battery pack with an insulating protective film.

[0004] To achieve the above objectives, a first aspect of the present invention provides a slurry comprising an epoxy-acrylic hybrid resin, a photoinitiator, an active monomer, a curing agent, and additives; wherein, based on the total weight of the slurry, the content of the epoxy-acrylic hybrid resin is 60-85 wt%, the content of the photoinitiator is 1-5 wt%, the content of the active monomer is 10-30 wt%, the content of the curing agent is 0.5-5 wt%, and the content of the additives is 1-5 wt%.

[0005] A second aspect of the present invention provides a polyimide film comprising a stacked biaxially oriented polyimide film and a UV film; wherein the UV film is obtained by coating at least one side of the biaxially oriented polyimide film with a slurry provided by the present invention.

[0006] A third aspect of the present invention provides an insulation protection method for a power battery pack cold plate, the insulation protection method comprising: irradiating and activating a UV adhesive film contained in a polyimide film with ultraviolet light to obtain a polyimide adhesive film with an activated UV adhesive film; then pasting the polyimide adhesive film with the activated UV adhesive film onto a power battery pack cold plate and allowing the activated UV adhesive film to cure completely to obtain a power battery pack cold plate with an insulating protective film;

[0007] The polyimide film is the polyimide film provided by the present invention.

[0008] A fourth aspect of the present invention provides a power battery pack cold plate with an insulating protective film prepared by the method provided by the present invention, wherein the adhesive shear strength of the insulating protective film to the power battery pack cold plate is greater than or equal to 6 MPa, and the adhesive peel strength is greater than or equal to 1 N / mm, with the total area of ​​the power battery pack cold plate with the insulating protective film being 1 m². 2 It is estimated that the area of ​​the defect in the cold plate of the power battery pack with the insulating protective film is within 0.01m². 2 Within.

[0009] The beneficial effects of the present invention through the above technical solution are:

[0010] The slurry provided by this invention is coated onto a biaxially oriented polyimide (BOPI) film to form a polyimide (PI) film. The PI film is then activated by irradiation with ultraviolet light. The photoinitiator in the UV film absorbs energy, initiating a polymerization reaction of the active monomers, gradually generating heat. This heat causes the epoxy-acrylic hybrid resin to undergo ring-opening and cure with a curing agent, forming a cross-linked system. The UV film exhibits a photothermal synergistic reaction under UV irradiation. After activation, the PI film is adhered to a cold plate of a power battery pack, allowing the activated UV film to gradually cure without further processing.

[0011] The PI film provided by this invention contains a UV film, which has excellent temperature resistance and can still provide reliable insulation protection for the cold plate of the power battery pack at 500℃; it has excellent adhesive shear strength and adhesive peel strength; and the defects on the surface of the cured PI film, such as bubbles, oil stains, scratches, and wavy lines caused by the hot pressing process, are also greatly reduced.

[0012] Furthermore, the UV adhesive film in the PI film provided by this invention differs from the hot-press adhesive film. It eliminates the need for expensive hot-pressing equipment (6 million RMB per set) and cumbersome pressure-holding processes, requiring only UV irradiation for activation. The PI film provided by this invention only requires LED light source equipment, significantly reducing equipment costs and production energy consumption (hot-pressing processes typically require holding at 150°C for 10 minutes; the LED light source required for UV activation is a cold light source with low energy consumption). It can be produced using a roll-to-plate bonding process, effectively improving production efficiency and offering advantages such as ease of use, economy, and reliability.

[0013] Furthermore, in a preferred embodiment of the present invention, the present invention further improves the adhesive shear strength and adhesive peel strength of the PI film by selecting appropriate raw material types and ratios in the UV film, the thickness of the UV film, and the energy and time of irradiation of the UV film contained in the PI film by the LED light source. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the PI film in a preferred embodiment of the present invention;

[0015] Figure 2 This is a process flow diagram of the preparation process of PI film in a preferred embodiment of the present invention.

[0016] Explanation of reference numerals in the attached figures

[0017] 1. Protective film 2. UV adhesive film 3. BOPI base film Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of the present invention provides a slurry comprising an epoxy-acrylic hybrid resin, a photoinitiator, an active monomer, a curing agent, and additives; wherein, based on the total weight of the slurry, the content of the epoxy-acrylic hybrid resin is 60-85 wt%, the content of the photoinitiator is 1-5 wt%, the content of the active monomer is 10-30 wt%, the content of the curing agent is 0.5-5 wt%, and the content of the additives is 1-5 wt%.

[0020] When the content of each component in the slurry meets the above range, it can ensure that the obtained UV adhesive film has a suitable adhesive film process operation window time, can be pasted onto the object, and has strong adhesive strength. If this range is not met, the adhesive film process operation window time may be shortened, and the UV adhesive film will quickly cure and lose its adhesiveness after being activated by ultraviolet light, resulting in the inability to be pasted onto the object and the adhesive strength not reaching the expected effect.

[0021] Furthermore, based on the total weight of the slurry, the content of the epoxy-acrylic hybrid resin is 65-80 wt%, the content of the photoinitiator is 2-3 wt%, the content of the active monomer is 15-25 wt%, the content of the curing agent is 1-4 wt%, and the content of the additives is 1.5-3 wt%.

[0022] According to the present invention, preferably, the viscosity of the slurry at 25°C is 3000-10000 cps. When the viscosity of the slurry meets the above range, a UV film of uniform thickness can be coated.

[0023] According to the present invention, preferably, the epoxy-acrylic hybrid resin contains an unsaturated double bond to an epoxy group in a molar ratio of 1:(1-5). When the above ratio is met, it can be avoided that excessive cross-linking reaction under UV radiation causes the UV adhesive film to be rapidly activated and cured, losing its adhesiveness before being bonded to the substrate and thus becoming unusable for bonding to the battery cold plate. Further, the epoxy-acrylic hybrid resin contains an unsaturated double bond to an epoxy group in a molar ratio of 1:(3-4).

[0024] According to the present invention, preferably, the weight-average molecular weight of the epoxy-acrylic hybrid resin is 50,000-100,000 g / mol. When the weight-average molecular weight of the epoxy-acrylic hybrid resin meets the above range, it can ensure the mechanical properties of the UV film, giving the UV film strong adhesive strength, while also taking into account the workability, ensuring that the slurry has a suitable viscosity, and enabling the slurry to be uniformly coated to obtain a UV film of uniform thickness.

[0025] Furthermore, the weight-average molecular weight of the epoxy-acrylic hybrid resin is 60,000-80,000 g / mol.

[0026] According to the present invention, the epoxy-acrylic hybrid resin can be prepared by the following method: in the presence of a catalyst and a polymerization inhibitor, epoxy resin and acrylic acid are mixed at a weight ratio of (20-30):1 and subjected to an esterification reaction, preferably (22-28):1.

[0027] The total amount of the catalyst, the polymerization inhibitor, the epoxy resin, and the acrylic acid is 50-95 wt%, preferably 60-90 wt%, based on the total amount of the epoxy resin and the acrylic acid. The epoxy resin is a mixture of bisphenol A type epoxy resin and phenolic epoxy resin.

[0028] The reaction formula for the esterification reaction between bisphenol A epoxy resin and acrylic acid is as follows:

[0029]

[0030] Where R is n represents the degree of aggregation.

[0031] The reaction formula for the esterification reaction of phenolic epoxy resin and acrylic acid is as follows:

[0032]

[0033] Where R' is n represents the degree of aggregation.

[0034] Preferably, the weight ratio of the bisphenol A epoxy resin to the phenolic epoxy resin is (1-5):1, more preferably (2-4):1.

[0035] Preferably, the bisphenol A type epoxy resin is E51 bisphenol A type epoxy resin, and the phenolic epoxy resin is F51 phenolic epoxy resin.

[0036] Preferably, the amount of catalyst used is 0.5-5 wt%, more preferably 1.5-4 wt%, based on the total amount of the catalyst, the polymerization inhibitor, the epoxy resin, and the acrylic acid. If the amount of catalyst is too small, the esterification reaction will be incomplete; if the amount is too large, excessive small molecule residues will occur, which will reduce the thermodynamic properties of the epoxy-acrylic acid hybrid resin.

[0037] Preferably, the catalyst is selected from ethylenediamine and / or quaternary ammonium salts, with ethylenediamine being the most preferred. Using ethylenediamine as a catalyst allows the esterification reaction to proceed more smoothly, resulting in an epoxy-acrylic hybrid resin with a narrower molecular weight distribution.

[0038] Preferably, based on the total amount of the catalyst, the polymerization inhibitor, the epoxy resin, and the acrylic acid, the amount of the polymerization inhibitor is 0.01-2 wt%, more preferably 0.5-1.5 wt%. If the polymerization inhibitor is too small, the polymerization inhibition effect will be poor, leading to localized and violent esterification reactions, resulting in a wide molecular weight distribution and poor thermodynamic properties in the obtained epoxy-acrylic hybrid resin; if the polymerization inhibitor is too large, the esterification reaction will be incomplete.

[0039] Preferably, the polymerization inhibitor is selected from at least one of p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, and hydroquinone, with hydroquinone being the most preferred. Using hydroquinone as the polymerization inhibitor results in a more stable esterification reaction and a narrower molecular weight distribution in the obtained epoxy-acrylic hybrid resin.

[0040] The aforementioned method for preparing epoxy-acrylic hybrid resin is only used to explain that the aforementioned epoxy-acrylic hybrid resin can be obtained by this method, and is not intended to limit the present invention. In specific embodiments of the present invention, the epoxy-acrylic hybrid resins are all commercially available, such as epoxy-acrylic hybrid resins purchased from Jiangsu Sanmu Group with a molar ratio of unsaturated double bonds to epoxy groups of 1:3.5 and a weight-average molecular weight of 65,000 g / mol; epoxy-acrylic hybrid resins purchased from DSM with a molar ratio of unsaturated double bonds to epoxy groups of 1:3 and a weight-average molecular weight of 70,000 g / mol; and epoxy-acrylic hybrid resins purchased from Jiangsu Sanmu Group with a molar ratio of unsaturated double bonds to epoxy groups of 1:4 and a weight-average molecular weight of 77,000 g / mol.

[0041] According to the present invention, preferably, the photoinitiator is selected from at least one of 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazole, 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,1'-diimidazole, 2,5-bis(o-chlorophenyl)-4,4'-dimethylphenyl-1H-imidazole, 9,10-anthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, α-methylbenzoin and α-phenylbenzoin, preferably 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazole. Using 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazole as a photoinitiator, the photopolymerization reaction is stable and the exothermic reaction is uniform. It can gradually initiate the subsequent epoxy ring-opening curing reaction of the epoxy-acrylic hybrid resin, thereby ensuring that the UV film has a sufficiently long film process operation window time, and the subsequent curing reaction can proceed gradually and smoothly, making it easy to stick to the substrate and having strong adhesive strength.

[0042] According to the present invention, preferably, the active monomer is selected from at least one of diethylene glycol diacrylate, isobornyl methacrylate, glycerol triacrylate, ethylene glycol dimethacrylate, pentaerythritol triacrylate, 2-phenoxyethyl acrylate, 2-(p-chlorophenoxyethyl methacrylate), 2-phenoxyethyl methacrylate, tetraethylene glycol dimethacrylate, and bisphenol A dimethacrylate, preferably diethylene glycol diacrylate. Using diethylene glycol diacrylate as the active monomer can balance the reactivity, adhesive strength, and viscosity of the UV film.

[0043] According to the present invention, preferably, the curing agent is selected from at least one of aliphatic polyamines, alicyclic polyamines, polyamides, polythiols, acid anhydrides, imidazole compounds, BF3 complexes, and aromatic polyamines, preferably alicyclic polyamines, and more preferably isophorone diamine. Using isophorone diamine as the curing agent, the heat generated during the photopolymerization of the epoxy-acrylic hybrid resin can reach the temperature required by the curing agent, initiating the subsequent epoxy ring-opening curing reaction. Furthermore, the subsequent reaction is stable, and the cured resin has a narrow molecular weight distribution and good thermodynamic properties.

[0044] According to the present invention, preferably, the additives include at least one of leveling agents, plasticizers, defoamers, wetting agents, dispersants, heat stabilizers, light stabilizers, anti-settling agents, ultraviolet absorbers, and anti-skinning agents, and more preferably include leveling agents, defoamers, and plasticizers.

[0045] According to the present invention, preferably, the leveling agent content is 0.02-1 wt%, more preferably 0.05-0.5 wt%, based on the total weight of the slurry.

[0046] According to the present invention, preferably, the leveling agent is selected from at least one of organosilicon, polyacrylate and nitrocellulose, and more preferably nitrocellulose.

[0047] According to the present invention, preferably, the content of the defoamer is 0.1-1 wt%, more preferably 0.3-0.5 wt%, based on the total weight of the slurry.

[0048] According to the present invention, preferably, the defoamer is a polyether defoamer.

[0049] Furthermore, the defoamer is at least one of polyoxyethylene polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene pentaerythritol ether, and polyoxyethylene polyoxypropylene alcohol amine ether.

[0050] Furthermore, the defoamer is polyoxyethylene polyoxypropylene glycerol ether.

[0051] According to the present invention, preferably, the content of the plasticizer is 0.5-3 wt%, more preferably 0.8-2 wt%, based on the total weight of the slurry.

[0052] According to the present invention, preferably, the plasticizer is selected from at least one of aliphatic diester plasticizers, polyester plasticizers, fatty acid ester plasticizers, and epoxy plasticizers, preferably a fatty acid ester plasticizer, and more preferably isooctyl palmitate. Using isooctyl palmitate as a plasticizer can effectively improve the toughness and mechanical properties of the resin.

[0053] A second aspect of the present invention provides a polyimide film (PI film), the polyimide film comprising a stacked biaxially oriented polyimide film (BOPI base film) and a UV film; wherein the UV film is obtained by coating at least one side of the biaxially oriented polyimide film with a slurry provided by the present invention.

[0054] According to the present invention, preferably, the thickness of the biaxially oriented polyimide film (BOPI base film) is 50-200 μm, and more preferably 60-180 μm.

[0055] According to the present invention, preferably, the thickness of the UV adhesive film is 10-30 μm. When the thickness of the UV adhesive film meets this range, it can be fully activated by ultraviolet light irradiation and has a high cost-performance ratio; if the thickness is less than this range, the adhesive strength of the UV adhesive film will be insufficient, and if it is greater than this range, the UV adhesive film will not be easily activated.

[0056] Furthermore, the thickness of the UV film is 15-20 μm.

[0057] According to the present invention, preferably, the polyimide film further includes a protective film covering the UV film.

[0058] According to a preferred embodiment of the present invention, the structure of the polyimide film is shown below. Figure 1 The polyimide film comprises a biaxially oriented polyimide film (BOPI base film 3), a UV film 2, and a protective film 1, which are stacked sequentially.

[0059] According to the present invention, preferably, the thickness of the protective film is 10-40 μm, more preferably 15-35 μm.

[0060] According to the present invention, preferably, the protective film is selected from at least one of polyethylene terephthalate film (PET), polypropylene film (PP), polyethylene film (PE), polyolefin film, polystyrene film (PS), polyvinyl chloride film (PVC) and biaxially oriented polypropylene film (BOPP), and preferably polyethylene terephthalate film (PET).

[0061] According to a preferred embodiment of the present invention, the method for preparing the polyimide film includes: mixing an epoxy-acrylic hybrid resin, a photoinitiator, an active monomer, a curing agent, and additives to form a slurry for UV film preparation; then coating the slurry onto a biaxially oriented polyimide film (BOPI base film); forming a UV film on the biaxially oriented polyimide film (BOPI base film); and finally covering the UV film with a protective film. The process flow for preparing the polyimide film is described below. Figure 2 .

[0062] A third aspect of the present invention provides an insulation protection method for a power battery pack cold plate, the insulation protection method comprising: irradiating and activating a UV film contained in a polyimide film with ultraviolet light to obtain a polyimide film with an activated UV film; then pasting the polyimide film with the activated UV film onto the power battery pack cold plate and allowing the activated UV film to cure completely to obtain a power battery pack cold plate with an insulating protective film;

[0063] The polyimide film is the polyimide film provided by the present invention.

[0064] Because biaxially oriented polyimide (BOPI) films are typically brown (transparent BOPI films are also available, but they are expensive and their temperature resistance and insulation properties are inferior to conventional brown BOPI films), they strongly absorb and block UV light sources, preventing direct irradiation of the UV adhesive film for activation. Therefore, UV light is first used to activate the UV adhesive film on one side of the film coating, without needing to penetrate the BOPI film. The activated UV adhesive film is then adhered to the cold plate of the battery pack for curing. During the curing process, rolling or other pressing methods can be used to increase the adhesion strength between the battery pack cold plate and the protective insulating film.

[0065] The PI film is activated by irradiating it with ultraviolet light. The photoinitiator in the UV film absorbs energy, thereby initiating a polymerization reaction of the active monomers, gradually generating heat, which in turn activates the curing agent. This causes the epoxy-acrylic hybrid resin to undergo ring-opening and cure with the curing agent, forming a cross-linked system. The UV film undergoes a photothermal synergistic reaction under UV irradiation. After activation, the PI film is adhered to the cold plate of the power battery pack, allowing the activated UV film to gradually cure without further processing.

[0066] In this invention, the base material of the power battery pack cold plate is an aluminum plate.

[0067] According to the present invention, when the UV film is covered with a protective film, the protective film is first removed, and then the UV film contained in the PI film is activated by irradiation with ultraviolet light.

[0068] According to the present invention, the adhesive can be applied by roller pressing or by hand.

[0069] According to the present invention, preferably, the wavelength of the ultraviolet light is 300-400 nm and the energy is 1000-4000 mJ / cm². 2 When the wavelength and energy of ultraviolet light meet the above range, it can ensure that the obtained UV film has a suitable film processing window time, can be pasted onto the object, and has strong adhesive strength, while also giving the UV film good thermodynamic properties.

[0070] According to the present invention, preferably, the irradiation activation time is within 1 minute. When the irradiation activation time meets this range, it can be ensured that the obtained UV film has a suitable film processing window time, can be pasted onto the object, and has strong adhesive strength, while also giving the UV film good thermodynamic properties.

[0071] According to the present invention, preferably, the polyimide film with the activated UV film is adhered to the cold plate of the power battery pack within 15 minutes after the irradiation activation.

[0072] According to the present invention, preferably, the curing time is 0.5-1 hour.

[0073] A fourth aspect of the present invention provides a power battery pack cold plate with an insulating protective film prepared by the method provided by the present invention, wherein the adhesive shear strength of the insulating protective film to the power battery pack cold plate is greater than or equal to 6 MPa, and the adhesive peel strength is greater than or equal to 1 N / mm, with the total area of ​​the power battery pack cold plate with the insulating protective film being 1 m². 2 It is estimated that the area of ​​the defect in the cold plate of the power battery pack with the insulating protective film is within 0.01m². 2 Within.

[0074] According to the present invention, preferably, the adhesive shear strength of the insulating protective film to the cold plate of the power battery pack is 6-8 MPa, and the adhesive peel strength is 1-2 N / mm.

[0075] In this invention, the defects can be oil stains, wrinkles, bubbles, scratches, wavy lines, foreign objects, damage, excessively deep indentations, gaps and tears, and rough edges. The area of ​​the defects can be measured by a CCD vision inspection system.

[0076] The present invention will be described in detail below through examples. Unless otherwise specified, all examples and comparative examples below use conventional methods; the reagents and materials used are commercially available unless otherwise specified. The specific testing methods involved in the present invention are as follows:

[0077] Temperature resistance test: After baking the insulating protective film in a muffle furnace at 500±2℃ for 0.5h, the insulating protective film is taken out and a voltage of 1000V is applied to both surfaces of the insulating protective film for 60s. Check whether the insulating film is broken down.

[0078] Adhesion peel strength test: GB / T 2792-2014;

[0079] Bond shear strength test: GB / T 7124-2008;

[0080] Defect Area Monitoring: A CCD vision inspection system is used to monitor the total area of ​​defects, and then the total area of ​​the cold plate of the power battery pack with insulating protective film is calculated as 1m². 2 The area of ​​defects in the cold plate of the power battery pack with insulating protective film is calculated.

[0081] Example 1

[0082] Preparation of PI film

[0083] Epoxy-acrylic hybrid resin (purchased from Jiangsu Sanmu Group, with a molar ratio of unsaturated double bonds to epoxy groups of 1:3.5 and a weight-average molecular weight of 65,000 g / mol), photoinitiator (2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazolium), active monomer (diethylene glycol diacrylate), curing agent (isophorone diamine), and additives (nitrocellulose, polyoxyethylene polyoxypropylene glycerol ether, and isooctyl palmitate) were mixed in proportion to obtain a slurry for UV film (viscosity of 4000 cps at 25°C). This slurry was then uniformly coated onto a BOPI base film (100 μm thick) to a thickness of 18 μm, thus forming a UV film on the BOPI base film. A protective film (black PET film, 25 μm thick) was then covered on top of the UV film to obtain the PI film.

[0084] Based on the total weight of the slurry, the amount of epoxy-acrylic hybrid resin is 74 wt%, the amount of photoinitiator is 2.5 wt%, the amount of active monomer is 20 wt%, the amount of curing agent is 1.5 wt%, and the amount of additives is 2 wt% (nitrocellulose is 0.3 wt%, polyoxyethylene polyoxypropylene glycerol ether is 0.4 wt%, and isooctyl palmitate is 1.3 wt%).

[0085] Preparation of cold plate for power battery pack with insulating protective film

[0086] Peel off the protective film of the PI film, and use an LED light source with a wavelength of 365nm and a power of 3000mJ / cm². 2 Energy was applied to activate the UV adhesive film contained in the PI film for 0.5 minutes. Then, the PI film with the activated UV adhesive film was adhered to the cold plate of the power battery pack using a roll-pressing method and cured for 0.5 hours. This resulted in a cold plate of the power battery pack with an insulating protective film.

[0087] Example 2

[0088] PI films were prepared according to the method in Example 1, except that an epoxy-acrylic acid hybrid resin (purchased from DSM) with a molar ratio of unsaturated double bonds to epoxy groups of 1:3 and a weight-average molecular weight of 70,000 g / mol was used; the thickness of the BOPI base film was 62 μm; based on the total weight of the slurry, the amount of epoxy-acrylic acid hybrid resin was 66.9 wt%, the amount of photoinitiator was 2.2 wt%, the amount of active monomer was 24.5 wt%, the amount of curing agent was 3.6 wt%, and the amount of additives was 2.8 wt% (0.4 wt% nitrocellulose, 0.45 wt% polyoxyethylene polyoxypropylene glycerol ether, and 1.95 wt% isooctyl palmitate); the viscosity of the slurry at 25°C was 6700 cps. A PI film was obtained.

[0089] A power battery pack cold plate with an insulating protective film was prepared according to the method in Example 1, except that a 1500 mJ / cm² thermal paste was used. 2 Energy is used to irradiate and activate the UV film contained in the PI film for 0.8 minutes to obtain a power battery pack cold plate with an insulating protective film.

[0090] Example 3

[0091] PI films were prepared according to the method in Example 1, except that an epoxy-acrylic acid hybrid resin (purchased from Jiangsu Sanmu Group) with a molar ratio of unsaturated double bonds to epoxy groups of 1:4 and a weight-average molecular weight of 77,000 g / mol was selected; the thickness of the BOPI base film was 175 μm; based on the total weight of the slurry, the amount of epoxy-acrylic acid hybrid resin was 79 wt%, the amount of photoinitiator was 2.9 wt%, the amount of active monomer was 15.4 wt%, the amount of curing agent was 1.1 wt%, and the amount of additives was 1.6 wt% (0.2 wt% nitrocellulose, 0.35 wt% polyoxyethylene polyoxypropylene glycerol ether, and 1.05 wt% isooctyl palmitate); the viscosity of the slurry at 25°C was 7000 cps. PI films were obtained.

[0092] A power battery pack cold plate with an insulating protective film was prepared according to the method in Example 1, except that a 2500 mJ / cm² temperature was used. 2 Energy is used to irradiate and activate the UV film contained in the PI film for 0.6 minutes, resulting in a power battery pack cold plate with an insulating protective film.

[0093] Example 4

[0094] The PI film and the power battery pack cold plate with an insulating protective film were prepared according to the method of Example 1, except that an epoxy-acrylic acid hybrid resin (purchased from Double Bond Chemicals) with a molar ratio of unsaturated double bonds and epoxy groups of 1:1 and a weight-average molecular weight of 60,000 g / mol was selected. The PI film was obtained, and subsequently, the power battery pack cold plate with an insulating protective film was obtained.

[0095] Example 5

[0096] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method in Example 1, except that an equal amount of glycerol triacrylate was used instead of diethylene glycol diacrylate as the active monomer. The PI film was obtained, and subsequently, the power battery pack cold plate with an insulating protective film was obtained.

[0097] Example 6

[0098] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method in Example 1, except that an equal amount of o-diaminocyclohexane was used as the curing agent instead of isophorone diamine. The PI film was obtained, and subsequently, the power battery pack cold plate with an insulating protective film was obtained.

[0099] Example 7

[0100] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method in Example 1, except that the proportions of nitrocellulose, polyether defoamer, and isooctyl palmitate were different. Specifically, the amount of nitrocellulose was 0.55 wt%, the amount of polyoxyethylene polyoxypropylene glycerol ether was 0.57 wt%, and the amount of isooctyl palmitate was 0.88 wt%. A PI film was obtained, which in turn yielded a power battery pack cold plate with an insulating protective film.

[0101] Example 8

[0102] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method in Example 1, except that an equal amount of organosilicon was used instead of nitrocellulose, and an equal amount of phthalate was used instead of isooctyl palmitate. The PI film was obtained, and subsequently, the power battery pack cold plate with an insulating protective film was obtained.

[0103] Example 9

[0104] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method in Example 1, except that the coating thickness of the UV film was 30 μm. The PI film was obtained, and subsequently, the power battery pack cold plate with an insulating protective film was obtained.

[0105] Example 10

[0106] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method of Example 1, except that the proportions of epoxy-acrylic hybrid resin, photoinitiator, active monomer, curing agent, and additives were different. Specifically, based on the total weight of the slurry, the amount of epoxy-acrylic hybrid resin was 83.4 wt%, the amount of photoinitiator was 1.1 wt%, the amount of active monomer was 10 wt%, the amount of curing agent was 0.6 wt%, and the amount of additives was 4.9 wt% (0.735 wt% nitrocellulose, 0.98 wt% polyoxyethylene polyoxypropylene glycerol ether, and 3.185 wt% isooctyl palmitate). A PI film was obtained, and thus a power battery pack cold plate with an insulating protective film was obtained.

[0107] Example 11

[0108] The PI film and the power battery pack cold plate with an insulating protective film were prepared according to the method of Example 1, except that the energy used to activate the UV film contained in the PI film was different. Specifically, 800 mJ / cm 2 Energy is used to irradiate and activate the UV film contained in the PI film, resulting in a power battery pack cold plate with an insulating protective film.

[0109] Comparative Example 1

[0110] A PI film and a power battery pack cold plate with an insulating protective film were prepared according to the method of Example 1, except that the proportions of epoxy-acrylic hybrid resin, photoinitiator, active monomer, curing agent, and additives were different. Specifically, based on the total weight of the slurry, the amount of epoxy-acrylic hybrid resin was 40 wt%, the amount of photoinitiator was 8 wt%, the amount of active monomer was 40 wt%, the amount of curing agent was 6 wt%, and the amount of additives was 6 wt% (0.9 wt% nitrocellulose, 1.2 wt% polyoxyethylene polyoxypropylene glycerol ether, and 3.9 wt% isooctyl palmitate). A PI film was obtained, and thus a power battery pack cold plate with an insulating protective film was obtained.

[0111] Comparative Example 2

[0112] Structural adhesive (purchased from Huitian New Materials, model 8652, weight-average molecular weight 0.5 million g / mol) was coated onto the cold plate of the power battery pack to a thickness of 300 μm, resulting in a power battery pack cold plate with structural adhesive bonding. At 220℃, the structural adhesive decomposed and failed, completely losing its insulating properties.

[0113] Comparative Example 3

[0114] Commercially available hot-pressing PI film (purchased from Jiangsu Saiwu) was used to hot-press a power battery pack cold plate. The hot-pressing conditions were: temperature 150℃, pressure 5MPa, held for 10 minutes, resulting in a power battery pack cold plate with an insulating protective film. The power battery pack cold plate showed significant deformation under pressure, with visible deformation in the flow channels and numerous defects such as bubbles.

[0115] Test case

[0116] In the cold plates of the power battery packs with insulating protective films in each embodiment and comparative example, the adhesive shear strength and adhesive peel strength of the insulating protective film to the cold plate, the temperature resistance of the insulating protective film, and the total area of ​​the cold plates of the power battery packs with insulating protective films were measured as 1m². 2 The area of ​​defects in the cold plate of the power battery pack with insulating protective film was calculated. The results are shown in Table 1.

[0117] Table 1

[0118]

[0119] As shown in Table 1, compared with Comparative Example 1, the PI film prepared using the slurry provided by this invention provides significantly higher adhesive shear strength and adhesive peel strength for insulating the cold plate of the power battery pack. Comparative Example 2 uses structural adhesive as the insulating film for the cold plate of the power battery pack, which decomposes and fails at 220℃. However, the PI film provided by this invention does not break down at 500℃, indicating that the PI film provided by this invention has excellent temperature resistance. Comparative Example 3 uses a hot-pressing process, which reduces the adhesive shear strength and adhesive peel strength of the insulating film for the cold plate of the power battery pack to some extent. Furthermore, considering that the total area of ​​the cold plate of the power battery pack with the insulating film is 1m², the results show that the PI film is less effective. 2 It is estimated that the defect area of ​​the cold plate of the power battery pack with insulating protective film exceeds 0.05m². 2 This demonstrates that the PI film provided by the present invention can effectively reduce surface defects in the cold plate of a power battery pack with an insulating protective film.

[0120] Furthermore, compared to Example 1, Example 4 changed the molar ratio of unsaturated double bonds and epoxy groups in the epoxy-acrylic hybrid resin; Example 5 changed the type of active monomer; Example 6 changed the type of curing agent; Example 7 changed the proportion of each component in the additives; Example 8 changed the types of leveling agents and plasticizers in the additives; Example 9 changed the coating thickness of the UV film; Example 10 changed the proportion of each component in the slurry; and Example 11 changed the irradiation activation energy. All of these changes resulted in a certain degree of reduction in the adhesive shear strength and adhesive peel strength of the insulating protective film on the cold plate of the power battery pack. This indicates that the molar ratio of unsaturated double bonds and epoxy groups in the epoxy-acrylic hybrid resin, the type and proportion of raw materials in the UV film, the thickness of the UV film, and the conditions under which the LED light source irradiates the UV film contained in the PI film all jointly affect the adhesive shear strength and adhesive peel strength of the PI film on the cold plate of the power battery pack.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polyimide film, characterized in that, The polyimide film comprises a stacked biaxially oriented polyimide film and a UV film; wherein the UV film is obtained by coating at least one side of the biaxially oriented polyimide film with a slurry; the slurry comprises an epoxy-acrylic hybrid resin, a photoinitiator, an active monomer, a curing agent, and additives; wherein, based on the total weight of the slurry, the content of the epoxy-acrylic hybrid resin is 60-85 wt%, the content of the photoinitiator is 1-5 wt%, the content of the active monomer is 10-30 wt%, the content of the curing agent is 0.5-5 wt%, and the content of the additives is 1-5 wt%. The weight-average molecular weight of the epoxy-acrylic acid hybrid resin is 50,000-100,000 g / mol. The epoxy-acrylic hybrid resin contains an unsaturated double bond and an epoxy group in a molar ratio of 1:(1-5).

2. The polyimide film according to claim 1, characterized in that, The epoxy-acrylic hybrid resin contains an unsaturated double bond and an epoxy group in a molar ratio of 1:(3-4).

3. The polyimide film according to claim 1 or 2, characterized in that, The photoinitiator is selected from at least one of 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazolium, 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,1'-diimidazole, 2,5-bis(o-chlorophenyl)-4,4'-dimethylphenyl-1H-imidazolium, 9,10-anthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, α-methylbenzoin and α-phenylbenzoin; And / or, the active monomer is selected from at least one of diethylene glycol diacrylate, isobornyl methacrylate, glycerol triacrylate, ethylene glycol dimethacrylate, pentaerythritol triacrylate, 2-phenoxyethyl acrylate, 2-(p-chlorophenoxyethyl methacrylate), 2-phenoxyethyl methacrylate, tetraethylene glycol dimethacrylate, and bisphenol A dimethacrylate. And / or, the curing agent is selected from at least one of aliphatic polyamines, alicyclic polyamines, polyamides, polythiols, acid anhydrides, imidazole compounds, BF3 complexes, and aromatic polyamines; And / or, the additives include at least one of leveling agents, plasticizers, defoamers, wetting agents, dispersants, heat stabilizers, light stabilizers, anti-settling agents, ultraviolet absorbers, and anti-skinning agents.

4. The polyimide film according to claim 3, characterized in that, The photoinitiator is 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl)imidazole; And / or, the active monomer is diethylene glycol diacrylate; And / or, the curing agent is an alicyclic polyamine; And / or, the additives include leveling agents, defoamers, and plasticizers.

5. The polyimide film according to claim 4, characterized in that, The curing agent is isophorone diamine.

6. The polyimide film according to claim 3, characterized in that, Based on the total weight of the slurry, the leveling agent content is 0.02-1 wt%; And / or, the leveling agent is selected from at least one of silicone, polyacrylate and nitrocellulose; And / or, based on the total weight of the slurry, the content of the defoamer is 0.1-1 wt%; And / or, the defoamer is a polyether defoamer; And / or, based on the total weight of the slurry, the content of the plasticizer is 0.5-3 wt%; And / or, the plasticizer is selected from at least one of aliphatic diester plasticizers, polyester plasticizers, fatty acid ester plasticizers and epoxy plasticizers.

7. The polyimide film according to claim 6, characterized in that, Based on the total weight of the slurry, the leveling agent content is 0.05-0.5 wt%; And / or, the leveling agent is nitrocellulose; And / or, based on the total weight of the slurry, the content of the defoamer is 0.3-0.5 wt%; And / or, based on the total weight of the slurry, the content of the plasticizer is 0.8-2 wt%; And / or, the plasticizer is a fatty acid ester plasticizer.

8. The polyimide film according to claim 7, characterized in that, The plasticizer is isooctyl palmitate.

9. The polyimide film according to claim 1, characterized in that, The thickness of the biaxially oriented polyimide film is 50-200 μm; And / or, the thickness of the UV film is 10-30 μm.

10. The polyimide film according to claim 9, characterized in that, The thickness of the biaxially oriented polyimide film is 60-180 μm; And / or, the thickness of the UV film is 15-20 μm.

11. The polyimide film according to claim 1, characterized in that, The polyimide film also includes a protective film covering the UV film.

12. The polyimide film according to claim 11, characterized in that, The thickness of the protective film is 10-40 μm; And / or, the protective film is selected from at least one of polyethylene terephthalate film, polyolefin film and polyvinyl chloride film.

13. The polyimide film according to claim 12, characterized in that, The thickness of the protective film is 15-35 μm; And / or, the protective film is a polyethylene terephthalate film.

14. The polyimide film according to claim 12, characterized in that, The polyolefin film is at least one of polystyrene film, polypropylene film, and polyethylene film.

15. The polyimide film according to claim 14, characterized in that, The polypropylene film is a biaxially oriented polypropylene film.

16. A method for insulating and protecting the cold plate of a power battery pack, characterized in that, The insulation protection method includes: irradiating and activating the UV film contained in the polyimide film with ultraviolet light to obtain a polyimide film with activated UV film; then pasting the polyimide film with activated UV film onto the power battery pack cold plate and allowing the activated UV film to cure to obtain a power battery pack cold plate with an insulating protective film. Wherein, the polyimide film is the polyimide film according to any one of claims 1-15.

17. The insulation protection method according to claim 16, characterized in that, The ultraviolet light has a wavelength of 300-400 nm and an energy of 1000-4000 mJ / cm². 2 ; And / or, the irradiation activation time is within 1 minute; And / or, within 15 minutes after the irradiation activation, the polyimide film with the activated UV film is adhered to the cold plate of the power battery pack. And / or, the curing time is 0.5-1h.

18. A power battery pack cold plate with an insulating protective film prepared by the method of claim 16 or 17, characterized in that, The insulating protective film has an adhesive shear strength greater than or equal to 6 MPa and an adhesive peel strength greater than or equal to 1 N / mm to the cold plate of the power battery pack. The total area of ​​the cold plate of the power battery pack with the insulating protective film is 1 m². 2 It is estimated that the area of ​​the defect in the cold plate of the power battery pack with the insulating protective film is within 0.01m². 2 Within.

19. The power battery pack cold plate according to claim 18, characterized in that, The adhesive shear strength of the insulating protective film to the cold plate of the power battery pack is 6-8 MPa, and the adhesive peel strength is 1-2 N / mm.

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