A polyimide-based uv adhesion-promoting adhesive film, and a preparation method and application thereof

Abstract

The application discloses a polyimide-based UV tackifying adhesive film and a preparation method and application thereof. The polyimide-based UV tackifying adhesive film comprises a polyimide substrate layer and a UV tackifying adhesive layer coated on at least one surface of the polyimide substrate layer. The UV tackifying adhesive layer has an open time window for rework operation after ultraviolet irradiation, and is cured at room temperature to form a three-dimensional network structure with high crosslinking density. The UV tackifying adhesive layer comprises an epoxy-containing acrylate copolymer, an alicyclic epoxy resin, a bisphenol S type epoxy resin, a cationic photoinitiator, a latent retarder, a toughening agent, a flame retardant and a coupling agent. The UV tackifying adhesive film has excellent rework performance, can be cured at room temperature to form a three-dimensional network structure with high crosslinking density, and has good curing bonding performance.

Description

Technical Field

[0001] This application relates to the field of adhesive technology, and in particular to a polyimide-based UV tackifying adhesive film, its preparation method, and its application. Background Technology

[0002] The cell fixing, insulation protection, and structural bonding processes of new energy vehicle power battery packs require adhesive materials to possess initial tack, high strength after curing, high temperature resistance, and flame retardancy. Currently, the main adhesive materials are hot-pressed insulating tapes or UV-cured pressure-sensitive tapes. Hot-pressed insulating tapes require heating and pressure, have poor adaptability to irregularly shaped parts, and are inefficient; ordinary pressure-sensitive tapes have insufficient bonding strength; and while UV-cured pressure-sensitive tapes can cure quickly, they lose reworkability after curing, and most require further heating to achieve their final strength. Summary of the Invention

[0003] This application provides a polyimide-based UV tackifying adhesive film, its preparation method, and its application to solve the technical problem of poor reworkability of adhesive materials.

[0004] In a first aspect, this application provides a polyimide-based UV tackifying film, comprising a polyimide substrate layer and a UV tackifying layer coated on at least one surface of the polyimide substrate layer. The UV tackifying layer, after being irradiated with ultraviolet light, has an open time window suitable for rework and cures at room temperature to form a highly crosslinked network structure. The UV tackifying layer comprises the following raw materials in parts by weight: 15 to 30 parts of epoxy-containing acrylate copolymer; 5 to 20 parts of alicyclic epoxy resin; 2 to 8 parts of bisphenol S type epoxy resin; 0.05 to 0.8 parts of cationic photoinitiator; Latent delay agent: 0.3 to 5 parts; Toughening agent 1 to 8 parts; Flame retardant: 3 to 20 parts; Coupling agent 0.1 to 3 parts; The mass ratio of the cationic photoinitiator to the latent retarder is 1:(3~10).

[0005] In some embodiments, the UV tackifying adhesive layer has an open time window of 2h to 6h after UV irradiation, during which it can be reworked; the 180° peel strength of the UV tackifying adhesive layer during the open time window is ≤0.3N / mm, and the 180° peel strength after curing is >1.5N / mm.

[0006] In some of these embodiments, the latent delay agent includes at least one of a sterically hindered amine light stabilizer and a microencapsulated alkali source; The hindered amine light stabilizers include at least one of the following: bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate, and poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexadiyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]. The microencapsulated alkali source includes microencapsulated organic amine compounds.

[0007] Optionally, the method for preparing the microencapsulated alkali source includes the following steps: Polyisocyanate and polyol are reacted in an organic solvent at 40℃~70℃ for 1h~3h, and organic amine compounds are added as core material. The mixture is stirred evenly to obtain an oil phase containing polyurethane prepolymer and core material. The molar ratio of polyisocyanate to polyol is (1.2~2):1. The oil phase is added to the aqueous phase containing the emulsifier, and sheared and emulsified at 5000 rpm to 20000 rpm for 3 min to 15 min to form an oil-in-water emulsion. Add a polyamine aqueous solution dropwise to the oil-in-water emulsion and stir the mixture at 20°C to 50°C for 2 to 8 hours to allow the polyamine to undergo interfacial polymerization with the unreacted isocyanate groups on the surface of the oil droplets, forming a polyurea outer wall material and obtaining a microcapsule suspension. The microcapsule suspension is centrifuged or filtered, washed 2 to 5 times with deionized water and organic solvent, and vacuum dried at 30°C to 60°C for 6 to 24 hours to obtain the microencapsulated alkali source.

[0008] Optionally, the polyisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate; the polyol includes at least one of ethylene glycol, glycerol, trimethylolpropane, pentaerythritol, polyethylene glycol, and polypropylene glycol; the organic amine compound includes at least one of triethylamine, N,N-dimethylbenzylamine, triethanolamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, and triethylenediamine; the polyamine includes at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine; and the emulsifier includes at least one of polyvinyl alcohol, sodium dodecyl sulfate, and polyoxyethylene sorbitan monooleate.

[0009] In some of these embodiments, the epoxy-containing acrylate copolymer is copolymerized from 60 wt% to 80 wt% hard monomers, 15 wt% to 25 wt% soft monomers, and 5 wt% to 15 wt% epoxy-containing functional monomers. The hard monomer includes at least one of methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, and benzyl methacrylate. The soft monomer includes at least one of ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and isooctyl acrylate; The epoxy-containing functional monomer includes at least one of glycidyl methacrylate, 3,4-epoxycyclohexyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, and allyl glycidyl ether.

[0010] In some of the embodiments, the mass ratio of the alicyclic epoxy resin to the bisphenol S-type epoxy resin is (1~4):1; the epoxy equivalent of the alicyclic epoxy resin is 120 g / eq ~ 250 g / eq, and the epoxy equivalent of the bisphenol S-type epoxy resin is 180 g / eq ~ 400 g / eq. The alicyclic epoxy resin includes at least one of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, 2-(3,4-epoxycyclohexyl)-5,5-spiro(3,4-epoxycyclohexyl)-1,3-dioxane, dicyclopentadiene diepoxide, tetrahydroindene diepoxide, and epoxidized polybutadiene. The bisphenol S type epoxy resin includes at least one of bisphenol S diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, and bisphenol S type phenolic epoxy resin.

[0011] In some embodiments, the cationic photoinitiator includes at least one of arylthionium salts, aryliodonium salts, and arylferrocene salts; preferably, it includes at least one of triarylthionium hexafluorophosphate, triarylthionium hexafluoroantimonate, diaryliodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, 4-isobutylphenyl-4'-methylphenyliodonium hexafluorophosphate, and (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]-iron(II) hexafluorophosphate.

[0012] The toughening agent includes core-shell rubber or silicone elastomer.

[0013] The flame retardant includes at least one of phosphorus-based flame retardants, nitrogen-based flame retardants, phosphorus-nitrogen-based flame retardants, metal hydroxide flame retardants, and metal oxide flame retardants; preferably at least one of ammonium polyphosphate, melamine polyphosphate, melamine cyanurate, organic phosphonates, and phosphaphenanthrene derivatives.

[0014] The coupling agent includes at least one of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0015] Secondly, this application provides a method for preparing the above-mentioned polyimide-based UV tackifying adhesive film, comprising the following steps: An epoxy-containing acrylate copolymer, alicyclic epoxy resin, bisphenol S-type epoxy resin, latent retardant, toughening agent, flame retardant, coupling agent and solvent are mixed and stirred evenly. Then a cationic photoinitiator is added and mixed in the dark to obtain a UV tackifying adhesive. The UV tackifying adhesive is applied to the surface of a polyimide substrate layer, and the solvent is removed by drying to form a UV tackifying adhesive layer.

[0016] Thirdly, this application provides the application of the polyimide-based UV tackifying adhesive film as described in any one of claims 1 to 6 in a battery pack.

[0017] In some embodiments, the method of using the polyimide-based UV tackifying film includes the following steps: The polyimide-based UV tackifying film is adhered to the surface of the object to be bonded; The laminated polyimide-based UV tackifying film was irradiated with ultraviolet light at an energy of 800 mJ / cm² to 1500 mJ / cm². After UV irradiation, the polyimide-based UV tackifying film is reworked within the open time window; Allow the adhesive layer to cure completely at room temperature for 24 to 72 hours.

[0018] Compared with the prior art, this application has the following beneficial effects: Under ultraviolet light irradiation, the cationic photoinitiator absorbs light energy and decomposes to produce protic acid. However, the activity of this acid is temporarily inhibited by a latent retarder, thus slowing down the ring-opening polymerization rate of the epoxy groups and creating an open time window for reworkable operations. During this period, the film maintains moderate initial tack, allowing for assembly position adjustments or rework. As the retarder slowly dissociates, the protic acid is gradually released, catalyzing the ring-opening polymerization of the epoxy groups in the alicyclic epoxy resin and bisphenol S-type epoxy resin with the acrylate copolymer, forming a highly crosslinked three-dimensional network structure at room temperature without heating. Bisphenol S-type epoxy imparts excellent heat resistance to the film, alicyclic epoxy reduces curing shrinkage, toughening agents improve toughness, and flame retardants provide safety performance. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0021] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise specified, the raw materials used in the following examples and comparative examples are commercially available industrial products, and all conditions not otherwise specified are conventional.

[0023] 1. Preparation of epoxy-containing acrylate copolymers: 70g of methyl methacrylate, 20g of ethyl acrylate, 10g of glycidyl methacrylate, 150g of ethyl acetate, 50g of toluene, and 0.5g of azobisisobutyronitrile were added to a reaction vessel. The reaction was carried out at 70°C for 10 hours under nitrogen protection. Then, 0.2g of azobisisobutyronitrile was added and the reaction was continued for another 4 hours to obtain a solution of epoxy-containing acrylate copolymer with a solid content of 35%.

[0024] 2. Preparation of microencapsulated alkali source: Toluene diisocyanate and polyethylene glycol in a molar ratio of 2:1 were reacted in an organic solvent at 40℃~70℃ for 1h~3h. Triethylenediamine was added as the core material and stirred evenly to obtain an oil phase containing polyurethane prepolymer and core material. The oil phase was added to an aqueous phase containing sodium dodecyl sulfate and sheared and emulsified at 12,000 rpm for 10 min to form an oil-in-water emulsion. An aqueous solution of ethylenediamine was added dropwise to the oil-in-water emulsion, and the mixture was stirred at 35°C for 5 hours to allow the ethylenediamine to undergo interfacial polymerization with the unreacted isocyanate groups on the surface of the oil droplets, forming a polyurea outer wall material, thus obtaining a microcapsule suspension. The microcapsule suspension was centrifuged or filtered, washed three times with deionized water and organic solvent, and vacuum dried at 45°C for 15 hours to obtain microencapsulated alkali source powder.

[0025] 3. Prepare UV tackifying adhesive: The above copolymer solution (dry weight), alicyclic epoxy resin, bisphenol S-type epoxy resin, toughening agent, flame retardant, coupling agent, and latent retardant are mixed. Ethyl acetate is added to adjust the solid content to 45%. Finally, a cationic photoinitiator is added, and the mixture is stirred in the dark for 30 minutes and allowed to stand to remove bubbles.

[0026] Table 1. Component dosage of UV tackifying adhesive in Examples 1 to 4 (by parts by mass)

[0027] 4. Preparation of polyimide-based UV tackifying adhesive film: A UV tackifying adhesive was coated on both sides of a 50 μm PI film, dried at 100 °C for 5 min, and then covered with a release film to obtain a polyimide-based UV tackifying adhesive film.

[0028] Comparative Example 1: Compared with Example 1, Comparative Example 1 did not add a latent delay agent, and was otherwise the same as Example 1.

[0029] Comparative Example 2: Compared with Example 1, Comparative Example 2 contained 0.05 parts of cationic photoinitiator, 0.04 parts of latent retardant, and the rest were the same as in Example 1.

[0030] Comparative Example 3: Compared with Example 1, Comparative Example 3 contained 0.05 parts of cationic photoinitiator, 1 part of latent delay agent, and the rest were the same as in Example 1.

[0031] Comparative Example 4: Compared with Example 1, Comparative Example 4 uses an equal amount of UV absorber (Tinuvin P) instead of the latent delay agent, and the rest is the same as Example 1.

[0032] Comparative Example 5: Compared with Example 1, Comparative Example 5 uses an equal amount of organic amine compound (triethylenediamine) instead of the latent delay agent, and the rest is the same as Example 1.

[0033] Comparative Example 6: Compared with Example 1, Comparative Example 6 removed the coupling agent, and the rest was the same as Example 1.

[0034] Performance testing: The polyimide-based UV tackifying film was laminated onto the surface of an aluminum plate; the laminated polyimide-based UV tackifying film was irradiated with ultraviolet light at an energy of 1200 mJ / cm²; after ultraviolet irradiation, the position of the polyimide-based UV tackifying film was adjusted three times; and the film was left at room temperature for 72 hours to allow the adhesive layer to fully cure.

[0035] 1. Referring to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes", a 24mm×200mm polyimide-based UV tackifying film was applied to the surface of the substrate and irradiated with 1000mJ / cm² UV light. After UV irradiation, a group of samples was taken every 0.5h to test the 180° peel force (tensile speed 300mm / min), and the time during which the 180° peel force was ≤0.3 N / mm was recorded (open time window). After curing at room temperature (23℃ ± 2℃) for 72h, the 180° peel force was tested again.

[0036] 2. Referring to GB / T 33332-2016 "Test Method for Dynamic Shear Strength of Adhesive Tape", a 24mm×200mm polyimide-based UV tackifying adhesive film was bonded to the surface of an aluminum plate, irradiated with 1000mJ / cm² ultraviolet light, and then cured at room temperature for 72 hours before testing the shear strength.

[0037] 3. Referring to GB / T 7124-2008, after UV irradiation and curing at room temperature for 72 hours, the sample was aged in an oven at 130℃ ± 2℃ for 7 days, then placed in an environment at 23℃ ± 2℃ for 4 hours to equilibrate, and the 180° peel force was tested. The peel force retention rate after aging was calculated.

[0038] Table 2 Performance data of Examples 1 to 4 and Comparative Examples 1 to 6 Example 1 4.5 1.62 10.5 83.3 Example 2 3.5 1.75 11.8 86.3 Example 3 2.5 1.83 12.5 88.5 Example 4 5.5 1.68 11.2 83.9 Comparative Example 1 ＜0.5 1.58 9.8 79.7 Comparative Example 2 ＜1 1.6 10.2 81.3 Comparative Example 3 ＞8h 0.95 5.8 64.2 Comparative Example 4 ＜0.5 1.55 9.5 77.4 Comparative Example 5 0 0.42 2.1 42.9 Comparative Example 6 ＜3.5 1.61 10.3 55.6 Table 2 shows that the open times of Examples 1 to 4 are between 2.5 and 5.5 days, and the 180° peel strength after curing is >1.5 N / mm, indicating good reworkability. The shear strength of Examples 1 to 4 is >10.5 MPa, indicating high crosslinking density and good adhesion. The peel strength retention rate after aging of Examples 1 to 4 is >83%, indicating good durability. Compared with Example 1, the overall performance of Comparative Examples 1 to 6 is reduced, indicating that the pre-set ratio of the latent retardant, cationic photoinitiator, and latent retardant, as well as the coupling agent, are key to improving the overall performance of the UV tackifying film.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.

Claims

1. A polyimide-based UV tackifying adhesive film, characterized in that, The device includes a polyimide substrate layer and a UV tackifying layer coated on at least one surface of the polyimide substrate layer. The UV tackifying layer has a reworkable open time window after UV irradiation and cures at room temperature to form a highly cross-linked network structure. The UV tackifying layer comprises the following raw materials in parts by weight: 15 to 30 parts of epoxy-containing acrylate copolymer; 5 to 20 parts of alicyclic epoxy resin; 2 to 8 parts of bisphenol S type epoxy resin; 0.05 to 0.8 parts of cationic photoinitiator; Latent delay agent: 0.3 to 5 parts; Toughening agent 1 to 8 parts; Flame retardant: 3 to 20 parts; Coupling agent 0.1 to 3 parts; The mass ratio of the cationic photoinitiator to the latent retarder is 1:(3~10).

2. The polyimide-based UV tackifying adhesive film as described in claim 1, characterized in that, The UV tackifying adhesive layer has an open time window of 2h to 6h after being irradiated with ultraviolet light, during which it can be reworked. The 180° peel force of the UV tackifying adhesive layer during the open time window is ≤0.3N / mm, and the 180° peel force after curing is >1.5N / mm.

3. The polyimide-based UV tackifying film as described in claim 1, characterized in that, The latent delay agent includes at least one of a sterically hindered amine light stabilizer and a microencapsulated alkali source.

4. The polyimide-based UV tackifying film as described in claim 3, characterized in that, The hindered amine light stabilizers include at least one of the following: bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate, and poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidinyl)imino]-hexamethylenediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]. The microencapsulated alkali source is an organic amine compound encapsulated with polyurethane and / or polyurea as the wall material.

5. The polyimide-based UV tackifying film as described in claim 4, characterized in that, The preparation method of the microencapsulated alkali source includes the following steps: Polyisocyanate and polyol were reacted in an organic solvent at 40℃~70℃ for 1h~3h, and organic amine compounds were added as core material. The mixture was stirred evenly to obtain an oil phase containing polyurethane prepolymer and core material. The oil phase is added to the aqueous phase containing the emulsifier, and sheared and emulsified at 5000 rpm to 20000 rpm for 3 min to 15 min to form an oil-in-water emulsion. Add a polyamine aqueous solution dropwise to the oil-in-water emulsion and stir the mixture at 20°C to 50°C for 2 to 8 hours to allow the polyamine to undergo interfacial polymerization with the unreacted isocyanate groups on the surface of the oil droplets, forming a polyurea outer wall material and obtaining a microcapsule suspension. The microcapsule suspension is centrifuged or filtered, washed 2 to 5 times with deionized water and organic solvent, and vacuum dried at 30°C to 60°C for 6 to 24 hours to obtain the microencapsulated alkali source.

6. The polyimide-based UV tackifying film as described in claim 1, characterized in that, The mass ratio of the alicyclic epoxy resin to the bisphenol S-type epoxy resin is (1~4):

1.

7. The polyimide-based UV tackifying adhesive film as described in claim 1, characterized in that, The cationic photoinitiator includes at least one of arylthionium salt, aryliodoonium salt, and arylferrocene salt; The toughening agent includes core-shell rubber or silicone elastomer; The flame retardant includes at least one of phosphorus-based flame retardants, nitrogen-based flame retardants, phosphorus-nitrogen-based flame retardants, metal hydroxide flame retardants, and metal oxide flame retardants. The coupling agent includes at least one of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

8. A method for preparing a polyimide-based UV tackifying film as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The epoxy acrylate copolymer, alicyclic epoxy resin, bisphenol S-type epoxy resin, latent retardant, toughening agent, flame retardant, coupling agent and solvent are mixed and stirred evenly. Then, a cationic photoinitiator is added and mixed in the dark to obtain a UV tackifying adhesive. The UV tackifying adhesive is applied to the surface of a polyimide substrate layer, and the solvent is removed by drying to form a UV tackifying adhesive layer.

9. The application of a polyimide-based UV tackifying film as described in any one of claims 1 to 7 in a battery pack.

10. The application as described in claim 9, characterized in that, The method of using the polyimide-based UV tackifying film includes the following steps: The polyimide-based UV tackifying film is adhered to the surface of the object to be bonded; The laminated polyimide-based UV tackifying film was irradiated with ultraviolet light at an energy of 800 mJ / cm² to 1500 mJ / cm². After UV irradiation, the polyimide-based UV tackifying film is reworked within the open time window; Allow the adhesive layer to cure completely at room temperature for 24 to 72 hours.

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