Hot-pressed insulating film and preparation method thereof

Abstract

The invention discloses a hot-pressed insulating film which comprises a base material layer and an adhesive layer coated on the base material layer, the adhesive layer is obtained by drying an adhesive coating solution, and the coating solution comprises the following components in parts by weight: 100 parts of saturated polyester resin, 3-15 parts of isocyanate, 5-50 parts of epoxy resin and 20-80 parts of a flame retardant. 2-15 parts of other resin is added, so that the adhesive has good affinity with different hot-pressing interfaces, the other resin is one or a mixture of more of rosin resin and a modifier thereof, terpene resin and a modifier thereof, petroleum resin and phenolic resin, and the adhesive further comprises 0.1-1 part of curing accelerator, and the curing accelerator is one or a mixture of more of rosin resin and a modifier thereof, terpene resin and a modifier thereof, petroleum resin and phenolic resin. According to the present invention, the low-temperature hot-pressing adhesion with the metal material and some polar polymer materials can be rapidly achieved, the excellent adhesion strength, the high temperature resistance, the high humidity resistance and the cold and hot impact resistance are provided, the flame retardation function is provided, and the long-term outdoor safety use can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive tapes, and in particular relates to a hot-pressed insulating film and a preparation method thereof. Background Art

[0002] With the development and progress of society, industrial production and people's lives have a greater demand for energy. The emergence of new energy has greatly changed people's excessive dependence on traditional energy. It can solve the global energy supply and demand tension. New energy has the advantages of lower pollution, renewable, clean and efficient use. Nowadays, in addition to timely grid-connected transmission and use of photovoltaic, wind power and hydropower energy, a part of the unused energy is stored in lithium batteries, which will be released when needed, or can be used in peak hours to save a certain amount of electricity costs. In addition, the development of new energy vehicles has been very rapid in recent years. The penetration rate of new cars in China has exceeded 40%, and the global penetration rate of new energy vehicles has exceeded 17%. The application of lithium-ion batteries in new energy vehicles and storage fields occupies a major position, and the technology is becoming more and more mature.

[0003] From the assembly of lithium battery cells to modules, the integrated system for signal (cell voltage and temperature) collection requires the use of insulating film, which has hot pressing structural bonding function, flame retardant properties, and long-term stable outdoor reliability.

[0004] Some traditional hot-pressed insulating films are hot-melt type, and the materials cannot meet the requirements of long-term outdoor use, because the adhesive hydrolyzes in a continuous high temperature and high humidity environment, the bonding strength decays rapidly, and the service life is insufficient. There are also thermosetting insulating films, which have good structural adhesion and long-term aging resistance, but these films usually need to be refrigerated, the hot pressing processing temperature is relatively high, the processing time is long, the processing efficiency is slow, and the production cost is high.

[0005] In order to improve the deficiencies in the prior art, the present invention provides a polyurethane adhesive and a hot-pressed insulating film made of the adhesive. Compared with the traditional thermosetting adhesive film, the hot-pressed insulating film of the present invention can be stored at room temperature, has a lower hot-pressing processing temperature when used, has a faster processing efficiency, and does not require a post-baking process. At the same time, it meets the long-term weather resistance and flame retardant functions. It has strong market competitiveness. Summary of the invention

[0006] The present invention aims to provide a hot-pressed insulating film, which can be stored at room temperature, has a lower hot-pressing processing temperature when used, faster processing efficiency, and no post-baking process. At the same time, it meets the long-term weather resistance and flame retardant functions, and has strong market competitiveness.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a hot-pressed insulating film, which is composed of a substrate layer and an adhesive layer coated on the substrate layer; the adhesive layer is obtained by drying an adhesive coating liquid, and the coating liquid includes the following components in parts by weight:

[0008] Based on 100 parts by weight of the saturated polyester resin, the weight of the isocyanate is 3 to 15 parts, the weight of the epoxy resin is 5 to 50 parts, and the weight of the flame retardant is 20 to 80 parts.

[0009] The technical solution further improved in the above technical solution is as follows:

[0010] 1. In the above scheme, the saturated polyester resin is polymerized by dibasic acid and diol, the diol is an alkylene glycol with more than 3 carbon elements, and the saturated polyester resin contains 5% to 30% by weight of a mixture of one or more of polypropylene glycol, polytetrahydrofuran diol, polycarbonate diol, and polycaprolactone diol. The Tg point (glass transition temperature) of the saturated polyester resin is within 5°C to 30°C; the limiting viscosity IV of the saturated polyester is between 0.3 and 1.0.

[0011] 2. In the above scheme, the method for preparing the saturated polyester is:

[0012] 1) Synthesis of saturated polyester resin:

[0013] In a stainless steel reactor equipped with a stirrer, a cooling tube, and a thermometer, 1 mol of terephthalic acid, 1 mol of isophthalic acid, 1 mol of sebacic acid, 2.2 mol of 2-methyl-1,3-propanediol, 0.5 mol of neopentyl glycol, and 1.5 mol of 1,6-hexanediol were added, stirring was started, and then 0.04 mol% of the catalyst tetrabutyl titanate relative to the acid component was added. Under nitrogen, the reactor was heated to 160°C to 240°C, and the esterification reaction was carried out for 4 hours. Then 10 parts (relative to the previous esterification) of PCDL were added, stirred for 30 minutes, and gradually vacuumed. The pressure in the reactor was continuously reduced to below 40Pa, and the reactor was continuously heated to 260°C. The reactor was kept warm for 3 hours at 260°C and below 40Pa to complete the polymerization reaction and obtain a saturated polyester resin.

[0014] 2) Determination of the composition of saturated polyester resin:

[0015] 0.1 g of saturated polyester resin was dissolved in 5 ml of deuterated chloroform, and tested and analyzed at 25° C. using a 400 MHZ high-resolution nuclear magnetic resonance device (INOVA400). The composition of the saturated polyester resin was confirmed based on the obtained nuclear magnetic spectrum NMR-H.

[0016] 3) Determination of limiting viscosity of modified saturated polyester resin:

[0017] Phenol and 1,1,2,2-tetrachloroethane were prepared into a mixed solvent in a mass ratio of 60:40. 0.1 g of saturated polyester resin was dissolved in 25 ml of the mixed solvent. The reduced viscosity was tested with an Ubbelohde viscometer at 30°C. Then, the relationship curve between the reduced viscosity and the concentration was measured by the dilution concentration method, and the limiting viscosity when the concentration was 0 was calculated.

[0018] 4) Determination of glass transition temperature Tg point:

[0019] 10 mg of the resin sample was weighed and tested using a DSC differential scanning calorimeter (DSC 200F3, NETZSCH, Germany) with a scanning temperature range of -50 to 100°C and a heating rate of 20 K / min.

[0020] 3. In the above scheme, the isocyanate is one or a mixture of aromatic isocyanate, aliphatic isocyanate, alicyclic isocyanate. The above isocyanate is a mixture of room temperature reactive isocyanate and blocked (high temperature deblocking) isocyanate. Specifically, the room temperature reactive isocyanate can be toluene diisocyanate (TDI) and its dimer, trimer, 2,4-diphenylmethane diisocyanate (MDI) and its dimer, trimer, pentamethylene diisocyanate (PDI) and its dimer, trimer, hexamethylene diisocyanate (HDI) and its dimer, trimer, isophorone diisocyanate (IPDI) and its dimer, trimer, xylylene diisocyanate (XDI) and its dimer, trimer, or adducts of the above isocyanates; the deblocking temperature of the blocked isocyanate is below 130°C, and the blocking agent is preferably methyl ethyl ketone oxime (MEKO) or 3,5-dimethylpyrazole (DMP). The blocked isocyanate synthesized with the above room temperature reactive isocyanate.

[0021] 4. In the above scheme, the method for preparing blocked isocyanate:

[0022] Dissolve 100g of isocyanate HDI trimer (NCO content 15-25%) in butanone solvent with a solid content of 70%, place in a four-necked flask, and stir slowly under nitrogen. Heat the four-necked flask with a water bath, set the temperature at 60°C, and connect a condenser to one end of the four-necked flask. Weigh 53g of 3,5-dimethylpyrazole (DMP) and gradually add it to the flask. After reacting for 3 hours, take a sample to test the infrared spectrum (FT-IR) to observe whether the NCO at 2260cm-1 has disappeared. If it has disappeared, it means that the NCO reaction is complete, and the closed curing agent solution is prepared for use, recorded as BL1.

[0023] 5. In the above scheme, the epoxy resin refers to the product of bisphenol A type, bisphenol F type, bisphenol S type, phenolic epoxy resin modified by isocyanate, or a mixture of one or more thereof; the isocyanate is preferably a diisocyanate monomer such as TDI, MDI, HDI, PDI, XDI, IPDI, or a prepolymer containing two isocyanate functionalities. The modified product is synthesized with a molar equivalent ratio of NCO (isocyanate) to OH (hydroxyl) between 0.05 and 0.5.

[0024] 6. In the above scheme, the preparation method of the modified epoxy resin is:

[0025] Dissolve 100g of epoxy resin in 100g of butanone solvent with a solid content of 50%, place in a four-necked flask, and stir slowly under nitrogen. Heat the four-necked flask with a water bath, set the temperature at 60°C, and connect a condenser to one end of the four-necked flask. Weigh 5g of MDI (diphenylmethane diisocyanate) and gradually add it dropwise to the epoxy resin solution. The addition is completed in 30 minutes. After reacting for 3 hours, take a sample to test the infrared spectrum (FT-IR) to observe whether the NCO at 2260cm-1 has disappeared. If it has disappeared, it means that the NCO reaction is complete. The modified epoxy resin solution is prepared for use and is recorded as EM1.

[0026] Among them, the molar equivalent ratio of NCO (isocyanate) to OH (hydroxyl) is between 0.05 and 0.5. If NCO / OH is less than 0.05, the adhesive has insufficient hydrolysis resistance and heat resistance; if NCO / OH is greater than 0.5, gelation will occur during the synthesis process, making it unusable.

[0027] 7. In the above scheme, the flame retardant is one or a mixture of phosphorus (P) flame retardant, nitrogen (N) flame retardant, silicon (Si) flame retardant, metal hydroxide flame retardant, metal oxide flame retardant, metal boride flame retardant, etc.

[0028] 8. The above scheme also includes adding 2 to 15 parts of other resins so that the adhesive has good affinity with different hot pressing interfaces. The other resins are a mixture of one or more of rosin resin and its modified products, terpene resin and its modified products, petroleum resin, and phenolic resin.

[0029] 9. In the above scheme, 0.1 to 1 part of curing accelerator is also included, so that the activation reaction temperature of the above formula is reduced, the thermal curing temperature is reduced, the time is shortened, and the efficiency is improved. The curing accelerator is a mixture of one or two of tertiary amines and organic metal salts.

[0030] 10. In the above scheme, 0.1 to 2 parts of coupling agent are also included, which is beneficial to the dispersion of flame retardant filler in resin and the bonding of adhesive to metal interface. The coupling agent refers to one or a combination of titanate coupling agent, aluminate coupling agent, organosilane coupling agent, organochromium coupling agent, borate coupling agent.

[0031] 11. In the above solution, the substrate is selected from one of polyethylene terephthalate (PET), polyimide (PI), and polyethylene naphthalate (PEN). The preferred film thickness is 10 μm to 200 μm, and the further preferred thickness is 25 μm to 125 μm.

[0032] To achieve the above-mentioned purpose, another technical solution adopted by the present invention is: a method for preparing a hot-pressed insulating film, comprising the following steps: pre-corona treatment of a PET / 75μm film, coating an adhesive solution on the corona surface of the PET film, drying the solvent at 80℃ / 3mins+120℃ / 3mins, and obtaining an adhesive layer with a thickness (dry) of 25μm to form a hot-pressed insulating film.

[0033] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0034] 1. The hot-pressed insulating film of the present invention can quickly achieve low-temperature hot-pressing bonding with metal materials and some polar polymer materials, has excellent bonding strength and resistance to high temperature and humidity, resistance to cold and heat shock, and has flame retardant function, which can meet the requirements of long-term outdoor safe use.

[0035] 2. The hot-pressed insulating film of the present invention can be stored at room temperature, has a lower hot-pressing processing temperature when in use, faster processing efficiency, and no need for a post-baking process. It also meets the requirements of long-term weather resistance and flame retardancy. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with embodiments:

[0037] The raw materials for preparing the saturated polyester resin and the properties of the finally prepared epoxy-modified saturated polyester resin are shown in Table 1. The added amounts of the raw materials in Table 1 are all measured in molar amounts.

[0038] Table 1 shows the raw materials for preparing saturated polyester resin and the characterization of their properties

[0039] Table 1

[0040]

[0041] In Table 1, the acid components are:

[0042] TPA: terephthalic acid, IPA: isophthalic acid, OPA: phthalic acid, AA: adipic acid, SA: sebacic acid, CHDA: 1,4-cyclohexanedicarboxylic acid, TMA: trimellitic anhydride;

[0043] Alcohol content:

[0044] EG: ethylene glycol, 2-MPD: 2-methyl-1,3-propanediol, 1,3-PD: 1,3-propanediol, 1,4-BD: 1,4-butanediol, 1,5-PD: 1,5-pentanediol, 1,6-HD: 1,6-hexanediol, NPG: neopentyl glycol, DHM: 2-methyl-2-ethyl-1,3-propanediol, 1,4-CHDM: 1,4-cyclohexanedimethanol.

[0045] Oligomeric polyols: PTMG: polytetramethylene glycol, PPG: polypropylene glycol, PTMG-Co-PPG: copolymer of tetramethylene glycol and propylene oxide, PCDL: polycarbonate diol, PHA: polyhexane adipate diol, PBA: polybutylene adipate diol, PCL: polycaprolactone diol;

[0046] The molecular weight Mn of the oligomer polyol is in the range of ≤5000. If the molecular weight is too large, it is not conducive to the polymerization reaction, and the reactive functional groups per unit weight are insufficient;

[0047] The PCDL is a copolymer of carbonic acid and one or more of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol;

[0048] Production method of hot-pressed insulating film:

[0049] The PET / 75μm film was corona treated in advance, and the adhesive solution was coated on the corona surface of the PET film. The solvent was dried at 80℃ / 3mins+120℃ / 3mins. The thickness (dry) of the adhesive layer was 25μm, and a hot pressed insulating film was made.

[0050] Example

[0051] Example 1

[0052] Saturated polyester resin R1 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0053] Example 2

[0054] Saturated polyester resin R2 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 20 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0055] Example 3

[0056] Saturated polyester resin R3 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0057] Example 4

[0058] Saturated polyester resin R4 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0059] Example 5

[0060] Saturated polyester resin R5 / 100 parts, EM1 / 15 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 20 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0061] Example 6

[0062] Saturated polyester resin R5 / 100 parts, EM1 / 15 parts, rosin resin GB-100 / 3 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 20 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0063] Comparative Example 1

[0064] Saturated polyester resin R6 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 15 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0065] Comparative Example 2

[0066] Saturated polyester resin R7 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0067] Comparative Example 3

[0068] Saturated polyester resin R3 / 100 parts, EM1 / 3 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 10 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0069] Comparative Example 4

[0070] Saturated polyester resin R2 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 50 parts, flame retardant MC6000 / 30 parts, BL1 / 1 part, DBTDL / 0.1 parts, KBM403 / 1 part, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0071] Comparative Example 5

[0072] Saturated polyester resin R2 / 100 parts, EM1 / 10 parts, flame retardant OP935 / 18 parts, BL1 / 15 parts, DBTDL / 0.1 parts, KBM403 / 1 parts, use methyl ethyl ketone solvent / 100 parts to dissolve the above resins, and then disperse them with the flame retardant to make slurry, and then add curing agent, accelerator and hydrolysis resistance additive to make adhesive, and make PET hot pressing insulation film according to the above method;

[0073] Saturated polyester resin: as described in the examples.

[0074] MC-6000, melamine phosphate, Nissan Chemical;

[0075] OP935, phosphite flame retardant, Clariant Chemicals;

[0076] GB-100, rosin modified resin, Arakawa Chemical Co., Ltd.

[0077] KBM403, organic silane coupling agent, Shin-Etsu Chemical, Japan;

[0078] DBTDL, dibutyltin dilaurate, Aladdin Chemical, China;

[0079]

[0080]

[0081] Comprehensive evaluation

[0082] “○” represents qualified performance, “◎” represents excellent performance, “△” represents average performance, and “×” represents poor performance.

[0083] Evaluation method:

[0084] Initial peel strength (N / mm): hot press the insulating film and aluminum plate (1 series aluminum, H24 model) at 130℃ / 1.0Mpa / 180s. Take it out, cool it to room temperature and let it stand for 24 hours; test the peel strength at 180° peeling angle and 100mm / min speed;

[0085] High temperature and high humidity aging test (85℃×85RH / 1000H): same sample preparation method as 1, put the sample into the high temperature and high humidity environment box for 1000H, take it out, cool it to room temperature and let it stand for 24H, and test the peel strength in the same way as above;

[0086] Thermal shock aging test (-40℃~125℃ / 1000 cycles): same sample preparation method as 1, put the sample into the thermal shock environment box for 1500H, -40℃ / 0.5H, 125℃ / 0.5H, the hot and cold switching time is within 2mins, after 1000 cycles, take out and cool to room temperature and stand for 24H, test the peel strength, the method is the same as above;

[0087] Flame retardant test of hot pressed film: The hot pressed film is made into a 50mm*200mm specimen. According to the UL-94 classification of film flame retardant grades, the highest flame retardant grade is VTM-0, followed by VTM-1, VTM-2, HB, etc.

[0088] Determination of glass transition temperature Tg point: 10 mg of resin sample was weighed and tested using a DSC differential scanning calorimeter (DSC 200F3, NETZSCH, Germany) with a scanning temperature range of -50 to 100°C and a heating rate of 20 K / min.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A hot pressed insulating film, characterized in that: It consists of a substrate layer and an adhesive layer coated on the substrate layer; The adhesive layer is obtained by drying an adhesive coating liquid, wherein the coating liquid comprises the following components in parts by weight: Based on 100 parts by weight of the saturated polyester resin, the weight of the isocyanate is 3 to 15 parts, the weight of the epoxy resin is 5 to 50 parts, and the weight of the flame retardant is 20 to 80 parts.

2. The heat-pressed insulating film according to claim 1, characterized in that: The invention also includes adding 2 to 15 parts of other resins, wherein the other resins are a mixture of one or more of rosin resin and its modified products, terpene resin and its modified products, petroleum resin and phenolic resin.

3. The heat-pressed insulating film according to claim 1, characterized in that: It also includes 0.1 to 1 part of a curing accelerator, wherein the curing accelerator is a tertiary amine, an organic metal salt, or a mixture of two thereof.

4. The heat-pressed insulating film according to claim 1, characterized in that: The invention also comprises 0.1 to 2 parts of a coupling agent, wherein the coupling agent is one or a combination of a titanate coupling agent, an aluminate coupling agent, an organic silane coupling agent, an organic chromium compound coupling agent and a borate coupling agent.

5. The heat-pressed insulating film according to claim 1, characterized in that: The saturated polyester resin is polymerized from a dibasic acid and a diol, wherein the diols are all alkylene glycols with more than 3 carbon elements. The saturated polyester resin contains a mixture of 5% to 30% by weight of one or more of polypropylene glycol, polytetramethylene glycol, polycarbonate glycol, and polycaprolactone glycol to participate in the polymerization.

6. The heat-pressed insulating film according to claim 2, characterized in that: The isocyanate is a mixture of one or more of aromatic isocyanate, aliphatic isocyanate, and alicyclic isocyanate. The isocyanate is a mixture of room temperature reactive isocyanate and blocked (high temperature unblocking) isocyanate. Specifically, the room temperature reactive isocyanate can be toluene diisocyanate (TDI) and its dimer and trimer, 2,4-diphenylmethane diisocyanate (MDI) and its dimer and trimer, pentamethylene diisocyanate (PDI) and its dimer and trimer, hexamethylene diisocyanate (HDI) and its dimer and trimer, isophorone diisocyanate (IPDI) and its dimer and trimer, xylylene diisocyanate (XDI) and its dimer and trimer, or an adduct of the above isocyanates; the unblocking temperature of the blocked isocyanate is below 130° C., and the blocking agent is preferably methyl ethyl ketone oxime (MEKO) or 3,5-dimethylpyrazole (DMP).

7. The heat-pressed insulating film according to claim 2, characterized in that: The epoxy resin refers to bisphenol A type, bisphenol F type, bisphenol S type, a product of phenolic epoxy resin modified by isocyanate, or a mixture of one or more thereof.

8. The heat-pressed insulating film according to claim 1, characterized in that: The flame retardant is one or a mixture of phosphorus (P) flame retardant, nitrogen (N) flame retardant, silicon (Si) flame retardant, metal hydroxide flame retardant, metal oxide flame retardant, metal boride flame retardant and the like.

9. The heat-pressed insulating film according to claim 1, characterized in that: The substrate is selected from one of polyethylene terephthalate (PET), polyimide (PI), and polyethylene naphthalate (PEN). The preferred film thickness is 10 μm to 200 μm.

10. A method for preparing a hot-pressed insulating film according to claim 1, characterized in that: The following steps are involved: The PET / 75 μm film was pre-corona treated, and the adhesive solution was coated on the corona surface of the PET film. The solvent was dried at 80°C / 3mins+120°C / 3mins. The thickness of the adhesive layer was 25 μm, and a hot pressed insulating film was prepared.

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