Composition for insulating film, method for producing the same, and use thereof

Abstract

The application provides an insulating film composition, a preparation method and application thereof, and relates to the technical field of battery insulating films. The preparation method of the insulating film composition comprises the following steps: irradiating polyimide by beta rays to obtain irradiation-modified polyimide; and mixing the irradiation-modified polyimide, polyurethane acrylate, epoxy acrylate, a hydrophobic agent and an initiator. In the application, the insulating film composition is prepared by cooperation of the irradiation-modified polyimide and the hydrophobic agent, so that the adhesion of the insulating film is good, the insulating performance is excellent, and the appearance is good, and there are no problems such as bubbles, wrinkles, peeling, warping and the like.

Description

[0001] This application is a divisional application of the original application, the applicant of the original application is Shanghai Lanjun New Energy Technology Co., Ltd.,

[0002] The original application has a filing date of January 19, 2023, an application number of 202310077555.5, and a title of "A composition for insulating film and its preparation method and application". TECHNICAL FIELD

[0003] The present application belongs to the technical field of battery insulating film, and specifically relates to a composition for insulating film and its preparation method and application. BACKGROUND

[0004] Currently, commercial power batteries mainly adopt the way of coating an external insulating film to insulate and protect the battery body and other components. Taking a square battery as an example, in order to prevent the battery from being scratched and leaking electricity during subsequent transportation and assembly, a layer of insulating film with single-sided adhesion is generally coated on the surface of the battery, which can also play a role in waterproofing and dustproofing, thereby better protecting the battery.

[0005] With the development of power battery technology, the size of the battery cell gradually develops in the direction of large size. This trend requires more stringent external insulation process for the battery cell. The increase in battery size makes it more difficult to control the tension of the external insulating film, which leads to obvious appearance problems such as wrinkles, bubbles, and air holes on the surface of the battery insulating film. For thin side edges, the adhesion area of the insulating film is insufficient, the adhesion is not enough, and the edge is prone to warping, delamination, and other defects. Therefore, researchers hope to develop a new film coating method that not only ensures the insulation of the battery but also solves the process problems of large-size batteries.

[0006] For example, CN114644815A discloses a lithium battery insulating film for new energy vehicles, which is prepared by high-temperature extrusion molding to improve the mechanical properties and thermal conductivity of the battery cell insulating film. This method only changes the composition ratio of the external insulating film, but still uses the film coating method to coat the surface of the battery. It does not address the film area wrinkles, film surface indentation caused by tension rollers, and air bubble problems caused by the closed film area in the traditional film coating method.

[0007] CN111073543A discloses a power lithium battery side plate insulation film, comprising an insulation layer and an adhesive layer formed on the insulation layer, the insulation layer comprises a first polyester film layer, a second polyester film layer and a modified polyester film layer between the first polyester film layer and the second polyester film layer, the raw material of the modified polyester film layer comprises more than 90wt% of the first polyester resin and less than 10wt% of carbon black; the raw material of the adhesive layer comprises 20-70wt% of the second polyester resin, 1-10wt% of isocyanate curing agent and 20-70wt% of flame retardant. The insulation film can make the side plate achieve the performance of flame retardation and cold and hot impact resistance. However, the bonding strength and insulation performance need to be further improved, and the insulation film is directly hot-pressed and attached to the aluminum plate to form a laminated structure, which is easy to cause appearance problems such as wrinkles, indentations, bubbles and the like.

[0008] Therefore, it is a technical problem to be solved in the art to develop an insulation film with excellent insulation performance, good adhesion and good appearance. SUMMARY

[0009] In view of the deficiencies of the prior art, the purpose of the present application is to provide an insulation film composition, its preparation method and application. The modified polyimide irradiated by beta rays is used as raw material, mixed with polyurethane acrylate, epoxy acrylate, hydrophobic agent and initiator to prepare the insulation film composition, so that the adhesion of the insulation film is better, the insulation performance is excellent and the appearance is good, and problems such as bubbles, wrinkles, peeling and warping of the insulation film caused by uneven tension control or traditional film pasting method will not occur.

[0010] To achieve this purpose, the following technical solutions are adopted in the present application:

[0011] In a first aspect, the present application provides a preparation method of an insulation film composition, the preparation method comprising:

[0012] irradiating polyimide by beta rays to obtain modified polyimide irradiated by beta rays;

[0013] mixing the modified polyimide irradiated by beta rays, polyurethane acrylate, epoxy acrylate, hydrophobic agent and initiator to obtain the insulation film composition.

[0014] In the present application, the polyimide is modified by adopting irradiation technology, mixed with polyurethane acrylate, epoxy acrylate, hydrophobic agent and initiator to prepare an insulating film composition, the hydrophobic agent can reduce the water absorption capacity of the insulating film under high temperature and high humidity conditions, improve the hydrophobicity of the surface of the battery cell, thereby improving the insulation performance of the battery cell and ensuring the safety of the battery cell; the polyimide can enhance the adhesion of the cured film area on the battery shell and improve the brittleness of the film under low humidity and dry environment; through the cooperation of the two and the compounding with other components, the adhesion and insulation performance of the insulating film are excellent, and the appearance is good.

[0015] In an optional embodiment, the polyimide is irradiated by beta rays to obtain an irradiation-modified polyimide, comprising: preparing a suspension of the polyimide, irradiating the suspension by beta rays, and drying to obtain the irradiation-modified polyimide; by modifying the polyimide by adopting irradiation technology, the adhesion of the cured film area on the battery shell can be further improved, and the brittleness of the film under low humidity and dry environment can be improved.

[0016] Preferably, the dose of the irradiation is 75-350 Kgy; for example, it can be 80 Kgy, 90 Kgy, 100 Kgy, 120 Kgy, 140 Kgy, 160 Kgy, 180 Kgy, 200 Kgy, 220 Kgy, 240 Kgy, 260 Kgy, 280 Kgy, 300 Kgy, 320 Kgy, 340 Kgy, etc.

[0017] Preferably, the irradiation time is 30-150 s, for example, it can be 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 110 s, 120 s, 130 s, 140 s, etc.

[0018] In an optional embodiment, the mixing is carried out in the dark;

[0019] Optionally, the mixing is carried out in a solvent.

[0020] In an optional embodiment, the hydrophobic agent comprises at least one of an aqueous acrylic resin, a silicone resin, a hybrid resin, a polyolefin, an olefin-acrylate copolymer or a fluorocarbon compound.

[0021] In an optional embodiment, the mixed materials further comprise at least one of a dispersing agent, a leveling agent or other functional additives;

[0022] Preferably, the mixed materials comprise 4-8 parts by weight of the dispersing agent, for example, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, etc.

[0023] Preferably, the dispersant includes a high molecular dispersant.

[0024] Preferably, the mixed material includes 2 to 5 parts by weight of the leveling agent, such as 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0025] Preferably, the mixed material includes 1 to 3 parts by weight of the other functional additive, such as 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.

[0026] Preferably, the other functional additive includes a colorant.

[0027] Preferably, the mixed material further includes 8 to 12 parts by weight of water, such as 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, etc.

[0028] Preferably, the initiator includes at least one of phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, 4-phenyl benzophenone, 2-hydroxy-2-methyl-l-phenylpropanone, l-hydroxycyclohexyl phenyl ketone, or isopropyl thioxanthone.

[0029] In an alternative embodiment, the mixing of the irradiation-modified polyimide, the polyurethane acrylate, the epoxy acrylate, the hydrophobic agent, and the initiator includes:

[0030] mixing 10 to 20 parts of the irradiation-modified polyimide, 20 to 30 parts of the polyurethane acrylate, 20 to 30 parts of the epoxy acrylate, 5 to 15 parts of the hydrophobic agent, and 1 to 3 parts of the initiator.

[0031] Preferably, the composition includes 10 to 20 parts by weight of the polyimide, such as 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts, etc.

[0032] Preferably, the composition includes 20 to 30 parts by weight of the polyurethane acrylate, such as 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, etc.

[0033] Preferably, the composition includes 20 to 30 parts by weight of the epoxy acrylate, such as 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, etc.

[0034] Preferably, the composition comprises 5-20 parts by weight of the hydrophobic agent, for example, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, etc.

[0035] Preferably, the composition comprises 1-3 parts by weight of the initiator, for example, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, etc.

[0036] In a second aspect, the present application provides an insulating film composition prepared by the preparation method of any of the above-mentioned embodiments.

[0037] In a third aspect, the present application provides a composite insulating film for power batteries, comprising the insulating film composition according to the second aspect.

[0038] In a fourth aspect, the present application provides a preparation method of the composite insulating film for power batteries according to the third aspect, comprising:

[0039] coating the insulating film composition according to the second aspect to the surface of a substrate, and curing to obtain the composite insulating film for power batteries.

[0040] Preferably, the coating method comprises spraying.

[0041] Preferably, the curing method comprises ultraviolet light curing.

[0042] In the present application, the insulating film composition adopts a specific formula, and the method of ultraviolet curing and spraying film formation, compared with the method of surface film pasting of the battery cell, not only can effectively avoid the film area wrinkles caused by uneven tension and the pressure marks generated by the tension roller when pasting the film, but also can avoid the bubbles caused by the closed pasting area, while meeting the requirements of the battery cell insulation performance and adhesion performance.

[0043] In a fifth aspect, the present application provides a power battery comprising the insulating film composition according to the first aspect and / or the composite insulating film according to the third aspect.

[0044] In a sixth aspect, the present application provides an electric device comprising the power battery according to the fifth aspect.

[0045] The numerical range in the present application not only includes the point values listed above, but also includes any point values between the above-mentioned numerical ranges which are not listed, and the present application does not list the specific point values included in the range for the sake of brevity and simplicity.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] The composition for insulating film provided by the present application can reduce the water absorption capacity of the insulating film under high temperature and high humidity conditions, improve the hydrophobicity of the surface of the battery cell, thereby improving the insulation performance of the battery cell and ensuring the safety of the battery cell; the irradiation modified polyimide can enhance the adhesion of the cured film area to the battery shell and improve the brittleness of the film under low humidity and dry environment; the combination of the two and the compounding with other components make the adhesion and insulation performance of the insulating film excellent; and the composition for insulating film can be sprayed and formed by ultraviolet curing, avoiding the appearance problems such as bubbles, wrinkles and warping caused by uneven tension control or traditional film pasting method. DETAILED DESCRIPTION

[0048] The technical solutions of the present application will be further described by specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0049] The materials used in all examples and comparative examples of the present application are as follows:

[0050] Irradiation modified polyimide: polyimide (Araldite, powder 100g / bottle; CAS: 62929-02-6) is prepared into a suspension, irradiated by beta rays for 60s under the condition of irradiation dose of 100KGy, dried to obtain the irradiation modified polyimide.

[0051] Polyurethane acrylate: Allnex Zhenxin photocuring resin (UV resin) EBECRYL 284.

[0052] Epoxy acrylate: DSM epoxy acrylate AgiSyn 1010.

[0053] Hydrophobic agent: solvent-free self-drying organic silicon resin SIC6113.

[0054] Photoinitiator: 2-hydroxy-2-methyl-1-phenylpropanone.

[0055] Polymer dispersant: BYK-163.

[0056] Leveling agent: BYK-333.

[0057] Other functional additives: colorant.

[0058] Example 1

[0059] The embodiment provides an insulating film composition, which comprises 16 parts of irradiation modified polyimide, 16 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives and 10 parts of water in terms of weight.

[0060] The embodiment provides a preparation method of the insulating film composition, which comprises uniformly mixing irradiation modified polyimide, hydrophobic agent, polyurethane acrylate, epoxy acrylate, high molecular dispersant, photoinitiator, leveling agent, other functional additives and water under light-proof conditions to obtain the insulating film composition.

[0061] Embodiment 2

[0062] The embodiment provides an insulating film composition, which comprises 18 parts of irradiation modified polyimide, 14 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives and 10 parts of water in terms of weight.

[0063] The embodiment provides a preparation method of the insulating film composition, which is the same as that in embodiment 1.

[0064] Embodiment 3

[0065] The embodiment provides an insulating film composition, which comprises 20 parts of irradiation modified polyimide, 12 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives and 10 parts of water in terms of weight.

[0066] The embodiment provides a preparation method of the insulating film composition, which is the same as that in embodiment 1.

[0067] Embodiment 4

[0068] The embodiment provides an insulating film composition, which comprises 10 parts of irradiation modified polyimide, 10 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives and 10 parts of water in terms of weight.

[0069] The embodiment provides a preparation method of the insulating film composition, which is the same as that in embodiment 1.

[0070] Embodiment 5

[0071] The present embodiment provides an insulating film composition, which comprises 12 parts of irradiation-modified polyimide, 8 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high-molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives, and 10 parts of water by weight.

[0072] The present embodiment provides a preparation method of the insulating film composition, which is the same as that of Embodiment 1.

[0073] Embodiment 6

[0074] The present embodiment provides an insulating film composition, which comprises 14 parts of irradiation-modified polyimide, 6 parts of hydrophobic agent, 20 parts of polyurethane acrylate, 30 parts of epoxy acrylate, 6 parts of high-molecular dispersant, 3 parts of photoinitiator, 3 parts of leveling agent, 2 parts of other functional additives, and 10 parts of water by weight.

[0075] The present embodiment provides a preparation method of the insulating film composition, which is the same as that of Embodiment 1.

[0076] Embodiment 7

[0077] The present embodiment provides an insulating film composition, which is different from Embodiment 1 only in that the polyimide is not irradiation-modified, and other components, amounts, and preparation methods are the same as those of Embodiment 1.

[0078] Comparative Example 1

[0079] The present comparative example provides an insulating film composition, which is different from Embodiment 1 only in that the amount of irradiation-modified polyimide is 25 parts, and other components, amounts, and preparation methods are the same as those of Embodiment 1.

[0080] Comparative Example 2

[0081] The present comparative example provides an insulating film composition, which is different from Embodiment 1 only in that the amount of irradiation-modified polyimide is 5 parts, and other components, amounts, and preparation methods are the same as those of Embodiment 1.

[0082] Comparative Example 3

[0083] The present comparative example provides an insulating film composition, which is different from Embodiment 1 only in that there is no irradiation-modified polyimide in the insulating film composition, and other components, amounts, and preparation methods are the same as those of Embodiment 1.

[0084] Comparative Example 4

[0085] The comparative example provides a composition for an insulating film, which is different from Example 1 only in that no hydrophobic agent is contained in the composition for an insulating film, and other components, amounts, and preparation methods are the same as in Example 1.

[0086] Test Example

[0087] A composite insulating film for a power battery includes the composition for an insulating film provided in Examples 1 to 7 and Comparative Examples 1 to 4; the composite insulating film for a power battery has a thickness of 110 μm; and the composite insulating film for a power battery is prepared by spraying the composition for an insulating film provided in Examples 1 to 7 and Comparative Examples 1 to 4 onto a surface of a substrate, and UV curing.

[0088] A PET insulating film (Kanehara) commercially available in the prior art is used as a control.

[0089] Performance Test

[0090] (1) Insulating performance: an insulating resistance meter is used to test the voltage resistance of a positive pole and a film surface at a fixed voltage, and a final value is obtained after a fixed time;

[0091] (2) Surface energy: a da Vinci pen having different da Vinci values is used to draw lines on the film surface, and it is observed whether the drawn lines shrink within a target time, and if not, it is passed; and the da Vinci value at which the film does not shrink is recorded, and the greater the value, the better the effect;

[0092] (3) Adhesion performance: a tensile testing machine is used to test the peeling of the film surface at a fixed angle and a fixed moving speed;

[0093] (4) Appearance: after the film is formed on the surface of a battery, it is observed whether there are problems such as bubbles, wrinkles, indentations, peeling, and warping on the film surface; 10 samples are taken as one group, and the number of samples having bubbles, wrinkles, indentations, peeling, and warping on the film surface is recorded; among them, 0 to 2 samples, excellent appearance; 3 to 4 samples, qualified appearance; and more than 4 samples, unqualified appearance.

[0094] Specific test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] From the above table, the composition for insulating film provided by the present application uses polyimide and hydrophobic agent in combination, and both are in a specific content range, so that the adhesion of the insulating film is good, the insulation performance is excellent and the appearance is good, without problems such as bubbles, wrinkles, peeling, warping, etc. As can be seen from Examples 1-6, the edge resistance of the insulating film is 1288-1474 MΩ, the surface energy is 28-36 dyn / cm, the adhesive peel strength is 5.89-7.32 N / cm, and the appearance is qualified.

[0099] As can be seen from the comparison of Example 1 and Example 7, when the polyimide is not irradiation modified, the performance of the insulating film is poor.

[0100] As can be seen from the comparison of Example 1 and Comparative Examples 1-4, when the polyimide is not in a specific content range or there is no polyimide or hydrophobic agent, the adhesion performance of the insulating film is poor, or the insulation performance is poor.

[0101] In summary, the composition for insulating film provided by the present application uses irradiation modified polyimide and hydrophobic agent in a specific content to reduce the water absorption capacity of the insulating film under high temperature and high humidity conditions, and improve the hydrophobicity of the surface of the electric core, thereby improving the insulation performance of the electric core and ensuring the safety of the electric core. At the same time, it can enhance the adhesion of the cured film area on the battery shell, improve the brittleness of the film in a low humidity and dry environment, and the composition for insulating film can be sprayed and formed by ultraviolet curing, avoiding the appearance problems such as bubbles, wrinkles, warping, etc. caused by traditional film pasting method.

[0102] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a composition for insulating films, characterized in that, The preparation method includes: Polyimide was irradiated with beta rays to obtain irradiated modified polyimide; Mix 10-20 parts of the irradiated modified polyimide, 20-30 parts of polyurethane acrylate, 20-30 parts of epoxy acrylate, 5-15 parts of hydrophobic agent and 1-3 parts of initiator to obtain the composition for insulating film. The hydrophobic agent is solvent-free, self-drying silicone resin SIC6113.

2. The preparation method according to claim 1, characterized in that, The process of irradiating polyimide with beta rays to obtain irradiated modified polyimide includes: The polyimide was prepared into a suspension, irradiated with beta rays, and dried to obtain the irradiated modified polyimide.

3. The preparation method according to claim 2, characterized in that, The irradiation dose is 75~350 Kgy.

4. The preparation method according to claim 2, characterized in that, The irradiation time is 30~150 s.

5. The preparation method according to claim 1 or 2, characterized in that, The mixing was carried out under light-protected conditions.

6. The preparation method according to claim 1 or 2, characterized in that, The mixing is carried out in a solvent.

7. The preparation method according to claim 1 or 2, characterized in that, The mixed material also includes at least one of a dispersant, a leveling agent, or other functional additives.

8. The preparation method according to claim 7, characterized in that, The mixed material comprises 4 to 8 parts by weight of dispersant.

9. The preparation method according to claim 8, characterized in that, The dispersant includes a polymeric dispersant.

10. The preparation method according to claim 7, characterized in that, The mixed material comprises 2 to 5 parts by weight of leveling agent.

11. The preparation method according to claim 7, characterized in that, The mixed material includes 1 to 3 parts by weight of other functional additives.

12. The preparation method according to claim 11, characterized in that, The other functional additives include colorants.

13. The preparation method according to claim 7, characterized in that, The mixture also includes 8 to 12 parts water by weight.

14. The preparation method according to claim 1, characterized in that, The initiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 4-phenylbenzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, or isopropylthioxanthrone.

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