A hot-pressing insulation film, a flexible flat cable and a preparation method and application thereof

Abstract

The application provides a hot-pressing insulation film, a flexible flat cable and a preparation method and application thereof. The hot-pressing insulation film comprises a base material layer and an adhesive layer which are attached to each other; the preparation raw material of the adhesive layer comprises a modified unsaturated polyester resin, an acrylic rubber, an epoxy resin, an initiator, a curing agent and a flame retardant. The flexible flat cable comprises at least three wires and the hot-pressing insulation film covering both sides of the surface of the wires; the preparation method of the flexible flat cable comprises the following steps: placing a hot-pressing insulation film on the upper surface and the lower surface of the wires respectively, carrying out rolling, and then sequentially carrying out photocuring and heat curing to obtain the flexible flat cable. The hot-pressing insulation film provided by the application has excellent performance, and the flexible flat cable prepared by the application has good flame retardant performance, good high-temperature and high-humidity resistance and good cold and hot impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of insulating film technology, specifically relating to a hot-pressed insulating film, a flexible flat cable, its preparation method, and its application. Background Technology

[0002] FFC (Flexible Cable Tape) is made of PET-based insulating hot melt adhesive tape and extremely thin, fine tin-plated flat copper wire. Currently, it is often manufactured by hot pressing using an automatic roll forming machine. It boasts advantages such as flexibility, easy bending and folding, thinness, small size, simple connection, convenient disassembly, and easy electromagnetic interference (EMI) shielding. FFC is currently widely used for connections between printheads and motherboards in various printers, as well as for signal transmission and board connections in products such as plotters, scanners, copiers, audio equipment, LCD displays, fax machines, and various DVD players. In modern electrical equipment, FFC is virtually ubiquitous. Besides its stable use in the aforementioned 3C devices, the rise of new energy vehicles has driven the development of high-reliability FFC products. Therefore, research on FFC products is becoming increasingly in-depth, and reliability requirements are becoming increasingly stringent.

[0003] CN109536078A discloses a method for preparing a hot melt adhesive film for automotive FFC wires and the hot melt adhesive film thereof. The method includes: A. Preparing a primer: Step A1, according to the mass ratio, 20-40 parts of medium molecular weight saturated polyester and 60-80 parts of methyl ethyl ketone / toluene solvent are added to a reaction vessel and stirred to dissolve. The stirring speed is 500-1000 r / min. Step A2, after the mixture in Step A1 is stirred and dissolved evenly, it is cooled to room temperature. Then, according to the mass ratio, 0.1-5 parts of an anti-blocking agent and 0.5-20 parts of a low-temperature blocked isocyanate curing agent are added and stirred to disperse evenly. In this technical solution, by adding a low-temperature blocked isocyanate curing agent to the primer, the chemical crosslinking of the primer to the PET polyester film and the hot melt adhesive is increased. A blocked latent curing agent is used in the hot melt adhesive to increase the degree of crosslinking and cohesion of the hot melt adhesive, avoiding cracking of the hot melt adhesive or bubbling and delamination between the PET polyester film and the hot melt adhesive. However, the FFC wire prepared by the hot melt adhesive film provided by this technical solution has poor long-term resistance to damp heat and thermal shock.

[0004] CN114774011A discloses a double-sided hot melt adhesive film for FFC cables and its preparation method, comprising a buffer layer, a substrate, a reinforcing layer, and an adhesive layer bonded together sequentially; the buffer layer, the reinforcing layer, and the adhesive layer are all hot melt adhesive layers; at room temperature, the upper surface of the buffer layer is non-adhesive; the raw material of the buffer layer includes a first high-molecular-weight saturated polyester with a glass transition temperature of 20-80℃; the raw material of the reinforcing layer includes a second high-molecular-weight saturated polyester with a glass transition temperature of 20-30℃; the softening point temperature of the adhesive layer is 60-80℃. The inclusion of three hot melt adhesive layers with different glass transition temperatures (buffer layer, reinforcing layer, and adhesive layer) can prevent poor adhesion and delamination between the buffer layer and the insulation film of the FFC cable, and between the adhesive layer and the conductor of the FFC cable, thus eliminating safety hazards. However, the double-sided hot melt adhesive film for FFC cables provided by this technical solution has a complex structure and poor long-term resistance to damp heat and thermal shock.

[0005] In existing technologies, the hot-pressed insulating film for FFC is a hot-melt type. This material cannot meet the requirements for long-term outdoor use, and because the adhesive undergoes hydrolysis in a continuous high-temperature and high-humidity environment, its bonding strength decays rapidly, resulting in insufficient service life. Therefore, how to provide a hot-pressed insulating film for preparing automotive FFC with better flame retardant properties, better resistance to high temperature and humidity, and better thermal shock resistance has become an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a hot-pressed insulating film, a flexible flat cable, its preparation method, and its applications. In this invention, by designing the raw materials for the adhesive layer in the hot-pressed insulating film and further utilizing modified unsaturated polyester resin, the resulting hot-pressed insulating film exhibits good flame retardant properties, good high-temperature and high-humidity resistance, and good thermal shock resistance, making it suitable for manufacturing automotive FFC products.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a hot-pressed insulating film, the hot-pressed insulating film comprising a substrate layer and an adhesive layer bonded together;

[0009] The raw materials for preparing the adhesive layer include the following components in parts by weight: 100 parts modified unsaturated polyester resin, 3-20 parts acrylic rubber, 5-30 parts epoxy resin, 0.1-3 parts initiator, 5-30 parts curing agent, and 30-120 parts flame retardant.

[0010] In this invention, by designing the raw materials for preparing the adhesive layer in the hot-pressed insulating film and further using modified unsaturated polyester resin, the prepared hot-pressed insulating film has a simple structure and good flame retardant properties, good high temperature and humidity resistance, and good thermal shock resistance, which can meet the requirements for long-term outdoor use and is suitable for preparing automotive FFC products.

[0011] In this invention, by using modified unsaturated polyester resin, the hot-pressed insulating film can be pre-cured under UV light during the subsequent preparation of FFC, giving the hot-pressed insulating film a certain degree of thermal stability. Consequently, the expansion and contraction of the FFC product is minimal during the subsequent high-temperature heat curing. The FFC product prepared in this way has excellent heat resistance, high temperature and humidity resistance, thermal shock resistance, and flame retardancy, which can meet the requirements for long-term outdoor applications, such as electric vehicles and energy storage.

[0012] In this invention, by controlling the contents of epoxy resin, curing agent, and flame retardant within specific ranges, the prepared hot-pressed insulating film exhibits good mechanical properties, good insulation properties, and good flame retardancy. If the amount of epoxy resin is too high, the mechanical properties of the prepared hot-pressed insulating film will be poor; if the amount of epoxy resin is too low, the heat resistance, flame retardancy, and hydrolysis resistance of the prepared hot-pressed insulating film will be adversely affected.

[0013] In this invention, if the amount of curing agent is too large, the prepared hot-pressed insulating film will have insufficient thermal flexibility and insufficient bonding strength; if the amount of curing agent is too small, the prepared hot-pressed insulating film will have poor resistance to high temperature and high humidity.

[0014] In this invention, if the amount of flame retardant is too large, the adhesive strength of the prepared hot-pressed insulating film will be insufficient; if the amount of flame retardant is too small, the prepared hot-pressed insulating film will have poor high temperature and high humidity resistance and poor flame retardancy.

[0015] In this invention, the acrylic rubber in the raw materials for preparing the adhesive layer can be 3 parts, 5 parts, 7 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts by weight, etc.

[0016] The epoxy resin can be in parts by weight of 5, 7, 10, 12, 15, 18, 20, 23, 25, 27, or 30, etc.

[0017] The initiator can be expressed in parts by weight of 0.1, 0.2, 0.5, 0.7, 1, 1.3, 1.5, 1.8, 2, 2.4, 2.8, or 3 parts, etc.

[0018] The curing agent can be present in parts by weight of 5, 7, 10, 12, 15, 18, 20, 23, 25, 27, or 30, etc.

[0019] The flame retardant can be present in parts by weight of 30, 40, 50, 60, 70, 80, 90, 100, 110, or 120.

[0020] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0021] As a preferred technical solution of the present invention, the raw materials for preparing the modified unsaturated polyester resin include: diacid monomers and / or acid anhydrides, diol monomers, oligomeric polyols and modifiers.

[0022] The modifier is a compound containing unsaturated double bonds and isocyanate groups.

[0023] Preferably, the dicarboxylic acid monomer is selected from any one or a combination of at least two of phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid, adipic acid, or azelaic acid.

[0024] Preferably, the anhydride is selected from any one or a combination of at least two of phthalic anhydride, succinic anhydride, adipic anhydride, and azelaic anhydride.

[0025] Preferably, the diol is an alkylene diol with ≥3 carbon atoms, and the number of carbon atoms in the diol can be 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14 or 15, etc.

[0026] Preferably, the diol is selected from any one or a combination of at least two of propylene glycol, polypropylene glycol, 2-methyl-1,3-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, 2-methyl-2-ethyl-1,3-propanediol, or 1,4-cyclohexanediol.

[0027] Preferably, the oligomeric polyol is selected from any one or a combination of at least two of polypropylene glycol, polytetrahydrofuran glycol, polycarbonate glycol, and polycaprolactone glycol.

[0028] Preferably, the number average molecular weight of the oligopolyol is 500 to 3000, for example, it can be 500, 700, 1000, 1200, 1500, 1800, 2000, 2200, 2500, 2700 or 3000.

[0029] Preferably, the modifier is selected from ethyl isocyanate methacrylate (MOI) and / or ethyl isocyanate acrylate (AOI).

[0030] In this invention, the structural formulas of the ethyl isocyanate methacrylate (MOI) and / or ethyl isocyanate acrylate (AOI) are as follows:

[0031] Preferably, the glass transition temperature (Tg) of the modified unsaturated polyester resin is 5 to 40°C (e.g., 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C), and more preferably 5 to 30°C.

[0032] In this invention, the glass transition temperature of the modified unsaturated polyester resin is tested as follows: 10 mg of the modified unsaturated polyester resin is weighed and tested using a DSC differential scanning calorimeter (NETZS200F3, Germany), with a scanning temperature range of -50 to 100°C and a heating rate of 20 K / min.

[0033] As a preferred embodiment of the present invention, the modified unsaturated polyester resin is prepared by the following method, which includes the following steps:

[0034] (1) In a protective atmosphere, a dicarboxylic acid and / or anhydride and a diol are placed in a reaction vessel and subjected to a polycondensation reaction to obtain an esterified product.

[0035] (2) After adding oligomeric polyols to the reaction system of step (1), mix and then polymerize to obtain saturated polyester resin.

[0036] (3) In a protective atmosphere, the saturated polyester resin obtained in step (2) is dissolved in an organic solvent, a modifier is added to it, and a modification reaction is carried out to obtain the modified unsaturated polyester resin.

[0037] In this invention, unsaturated double bonds are introduced into the polyester resin by reacting the isocyanate groups in the modifier with the saturated polyester resin, thereby obtaining a modified unsaturated polyester resin.

[0038] In this invention, the protective atmosphere described in steps (1) and (3) is independently selected from nitrogen and argon.

[0039] Preferably, the ratio of the amount of the diacid and / or anhydride to the amount of the diol is 1:(1.2 to 1.4), for example, it can be 1:1.2, 1:1.22, 1:1.24, 1:1.26, 1:1.28, 1:1.3, 1:1.32, 1:1.34, 1:1.36, 1:1.38 or 1:1.4, etc.

[0040] Preferably, based on the mass percentage of the esterified product being 100%, the mass percentage of the oligomeric polyol is 5% to 30%, for example, it can be 5%, 7%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27%, or 30%, etc.

[0041] In this invention, the use of oligomeric polyols can improve hydrolysis resistance. If the content of oligomeric polyols in the modified unsaturated polyester resin is too low, the hydrolysis resistance will be insufficient; if the content of oligomeric polyols in the modified unsaturated polyester resin is too high, it will be difficult to polymerize and graft, resulting in precipitation incompatibility and affecting the bonding strength.

[0042] Preferably, based on the 100% molar percentage of hydroxyl groups in the saturated polyester resin, the molar percentage of the modifier is 1% to 30% (e.g., 1%, 2%, 5%, 7%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27%, or 30%), and more preferably 2% to 25%.

[0043] In this invention, by controlling the content of the modifier within a specific range, the prepared hot-pressed insulating film exhibits good high-temperature and high-humidity resistance and good thermal shock resistance. If the content of the modifier is too low, there will be too few unsaturated bonds in the unsaturated polyester resin, resulting in poor mechanical properties of the prepared hot-pressed insulating film; if the content of the modifier is too high, there will be too many unsaturated bonds in the unsaturated polyester resin, affecting the long-term heat resistance of the prepared hot-pressed insulating film.

[0044] Preferably, the limiting viscosity IV of the saturated polyester resin is 0.3 to 1.0 dl / g (for example, it can be 0.3 dl / g, 0.4 dl / g, 0.5 dl / g, 0.6 dl / g, 0.7 dl / g, 0.8 dl / g, 0.7 dl / g or 0.9 dl / g, etc.), and more preferably 0.3 to 0.8 dl / g.

[0045] As a preferred technical solution of the present invention, the temperature of the esterification reaction in step (1) is 150-200°C.

[0046] Preferably, the esterification reaction in step (1) takes 2 to 5 hours, for example, 2 hours, 3 hours, 4 hours or 5 hours.

[0047] In this invention, the esterification reaction in step (1) is carried out in a reaction vessel equipped with a stirrer, a cooling pipe and a thermometer.

[0048] Preferably, the mixing time in step (2) is 15 to 30 minutes, for example, it can be 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 27 minutes or 30 minutes.

[0049] Preferably, the temperature of the polycondensation reaction in step (2) is 230–280°C.

[0050] Preferably, the polycondensation reaction in step (2) takes 3 to 4 hours, for example, 3 hours, 3.5 hours or 4 hours.

[0051] Preferably, step (2) further includes a post-processing step after mixing.

[0052] Preferably, the post-processing method is as follows: evacuate the reactor for 0.5 to 2 hours until the pressure inside the reactor drops to 500 to 800 Pa to remove excess diol monomers, then gradually raise the temperature to 230 to 280°C, and further evacuate the reactor to reduce the pressure inside the reactor to 10 to 50 Pa.

[0053] Preferably, the dissolution temperature in step (3) is 50–70°C.

[0054] Preferably, the temperature of the modification reaction in step (3) is 50–70°C.

[0055] Preferably, the modification reaction time in step (3) is 3 to 5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0056] It should be noted that there are no special restrictions on the organic solvent used in step (3) in this invention. Commonly used organic solvents in the art are applicable, including but not limited to ethyl acetate.

[0057] In this invention, the preparation method of the modified unsaturated polyester resin specifically includes the following steps:

[0058] (1) In a protective atmosphere, a diacid and / or anhydride and a diol are placed in a stainless steel reactor equipped with a stirrer, a cooling pipe and a thermometer, and an esterification reaction is carried out at 150-200℃ for 2-5 hours to obtain an esterified product; wherein the molar ratio of the diacid and / or anhydride to the diol is 1:(1.2-1.4).

[0059] (2) After adding oligomeric polyol to the reaction system of step (1), stir for 15-30 min to mix evenly, then evacuate the reactor for 0.5-2 h until the pressure inside the reactor drops to 500-800 Pa to remove excess diol monomer, then gradually raise the temperature to 230-280 °C and further evacuate the reactor to reduce the pressure inside the reactor to 10-50 Pa, and perform polycondensation reaction at 230-280 °C for 3-4 h to obtain saturated polyester resin; wherein, based on the mass percentage of the esterified product being 100%, the mass percentage of the oligomeric polyol is 5%-30%;

[0060] (3) In a protective atmosphere, the saturated polyester resin and ethyl acetate solvent obtained in step (2) are added to a 500 mL three-necked flask with a distillation bridge. The mixture is stirred at 50-70 °C until the resin is completely dissolved. A modifier is then added and the mixture is reacted for 3-5 h to obtain the modified unsaturated polyester resin. The modifier has a molar percentage of 1% to 30%, based on the 100% molar percentage of hydroxyl groups in the saturated polyester resin.

[0061] As a preferred embodiment of the present invention, the acrylic rubber is selected from any one or a combination of at least two of polyethylene-acrylate rubber (AEM), polyacrylate rubber (ACM), or acrylic block copolymer (MAM).

[0062] It should be noted that AEM refers to a polymer obtained by reacting ethylene and methyl acrylate as the main monomers (molar ratio ≥ 50%) with at least one monomer selected from acrylic acid, maleic acid (maleic acid), itaconic acid (methylene succinic acid), glycidyl methacrylate (GMA), and allyl glycidyl ether (AGE) (molar ratio < 50%); ACM refers to a polymer obtained by reacting butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, acrylic acid, maleic acid (maleic acid), itaconic acid (methylene succinic acid), glycidyl methacrylate (GMA), and allyl glycidyl ether (AGE); MAM includes any one or a mixture of at least two of polymethyl methacrylate-polybutyl acrylate copolymer and polymethyl methacrylate-poly(butyl acrylate / 2-ethylhexyl acrylate) copolymer.

[0063] Preferably, the epoxy resin is selected from any one or a combination of at least two of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin or phenolic type epoxy resin.

[0064] Preferably, the initiator is a photoinitiator.

[0065] Preferably, the initiator is selected from carbonyl compounds, peroxides, nitrogen-containing compounds, organosulfur compounds, halides, photoreducing dyes, and quinone photoinitiators.

[0066] Preferably, the photoinitiator includes benzoin ether photoinitiators.

[0067] Preferably, the curing agent is a blocked isocyanate curing agent.

[0068] It should be noted that the blocked isocyanate curing agent described in this invention is commercially available, or it can be obtained through an addition reaction of isocyanate and end-capping agent.

[0069] Preferably, the isocyanate is selected from any one or a combination of at least two of aromatic isocyanates, aliphatic isocyanates, and alicyclic isocyanates.

[0070] Preferably, the aromatic isocyanate is selected from any one or a combination of at least two of toluene diisocyanate (TDI), toluene diisocyanate dimer, toluene diisocyanate trimer, 2,4-diphenylmethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate dimer, 2,4-diphenylmethane diisocyanate trimer, phenylmethylene diisocyanate (XDI), phenylmethylene diisocyanate dimer, or phenylmethylene diisocyanate trimer.

[0071] Preferably, the aliphatic isocyanate is selected from any one or a combination of at least two of hexamethylene diisocyanate (HDI), hexamethylene diisocyanate dimer, or hexamethylene diisocyanate trimer.

[0072] Preferably, the alicyclic isocyanate is selected from any one or a combination of at least two of isophorone diisocyanate (IPDI), isophorone diisocyanate dimer, and isophorone diisocyanate trimer.

[0073] Preferably, the blocking agent is selected from any one or a combination of at least two of phenol, imidazole, polyether diol, ε-caprolactam, 1,2,4-triazole, and methyl ethyl ketone oxime.

[0074] Preferably, the flame retardant is selected from any one or a combination of at least two of bromine (Br) based flame retardants, phosphorus (P) based flame retardants, phosphorus (P)-aluminum (Al) based flame retardants, nitrogen (N) based flame retardants, silicon (Si) based flame retardants, metal hydroxide flame retardants, metal oxide flame retardants, or metal boride flame retardants. More preferably, it is selected from any one or a combination of at least two of phosphorus (P) based flame retardants, phosphorus (P)-aluminum (Al) based flame retardants, or nitrogen (N) based flame retardants.

[0075] As a preferred embodiment of the present invention, the raw materials for preparing the adhesive layer further include 0.1 to 1 part of a curing accelerator, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, or 1 part, etc.

[0076] Preferably, the curing accelerator is selected from organic amine curing accelerators and / or metal salt curing accelerators.

[0077] Preferably, the raw materials for preparing the adhesive layer further include 0.5 to 2 parts of antioxidant, for example, 0.5 parts, 0.7 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, or 2 parts, etc.

[0078] Preferably, the antioxidant is selected from any one or a combination of at least two of aromatic amine antioxidants, hindered phenolic antioxidants, phosphite antioxidants or thioester antioxidants, and more preferably a combination of at least two of aromatic amine antioxidants, hindered phenolic antioxidants, phosphite antioxidants or thioester antioxidants.

[0079] Preferably, the raw materials for preparing the adhesive layer further include 0.1 to 2 parts of a dispersing agent, such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, or 2 parts.

[0080] Preferably, the dispersing agent is selected from any one or a combination of at least two of titanate coupling agents, aluminate coupling agents, organosilane coupling agents, organochromium complex coupling agents, or borate coupling agents.

[0081] In a second aspect, the present invention provides a method for preparing a hot-pressed insulating film as described in the first aspect, the method comprising the following steps:

[0082] The raw materials for preparing the adhesive layer are mixed with a solvent to obtain a mixed solution, which is then coated onto one side of the substrate surface and dried to obtain the hot-pressed insulating film.

[0083] Preferably, the substrate is a corona-treated PET film (polyethylene terephthalate film).

[0084] It should be noted that the above-obtained mixed solution is coated on the side of the substrate that has undergone corona treatment.

[0085] Preferably, the thickness of the substrate is 15 to 75 μm, for example, it can be 15 μm, 19 μm, 25 μm, 36 μm, 50 μm or 75 μm.

[0086] Preferably, the specific drying method includes: drying at 70-90°C for 2-5 minutes (e.g., 2 minutes, 3 minutes, 4 minutes, or 5 minutes), then raising the temperature to 110-130°C (e.g., 110°C, 112°C, 115°C, 117°C, 120°C, 121°C, 124°C, 128°C, or 130°C) and drying for another 2-5 minutes (e.g., 2 minutes, 3 minutes, 4 minutes, or 5 minutes).

[0087] Preferably, the thickness of the adhesive layer in the hot-pressed insulating film is 15-100 μm (e.g., it can be 15 μm, 17 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc.), and more preferably 17-80 μm.

[0088] Thirdly, the present invention provides a flexible flat cable, the flexible flat cable comprising at least three conductors and a heat-pressed insulating film as described in the first aspect covering both sides of the conductor surface.

[0089] Preferably, the conductor is a pure copper conductor, a tin-plated copper conductor, or a nickel-plated copper conductor.

[0090] Preferably, the spacing between any two adjacent conductors is 1 to 2 mm, for example, it can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2 mm.

[0091] It should be noted that this invention does not impose any special restrictions on the number of conductors in the flexible flat cable, and those skilled in the art can design it according to actual usage requirements. Furthermore, this invention does not impose any special restrictions on the length and height of the conductor cross-section, and can be designed according to actual usage requirements. Examples include, but are not limited to, conductor cross-sections with a length of 1 mm and a height of 0.07 mm.

[0092] Fourthly, the present invention provides a method for preparing a flexible flat cable as described in the third aspect of the process, the method comprising the following steps:

[0093] A heat-pressed insulating film as described in the first aspect is placed on the upper and lower surfaces of the conductor, respectively. After rolling, it is then subjected to photocuring and heat curing in sequence to obtain the flexible flat cable.

[0094] Preferably, the temperature of the roller pressing is 160 to 200°C, for example, it can be 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or 200°C.

[0095] Preferably, the pressure of the roller is 0.3 to 0.6 MPa, for example, it can be 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa or 0.6 MPa, etc.

[0096] Preferably, the rolling time is 2 to 3 seconds, for example, 2 seconds or 3 seconds.

[0097] Preferably, the photocuring time is 2 to 3 seconds, for example, 2 seconds or 3 seconds.

[0098] Preferably, the light intensity of the photocuring process is 800–4000 mJ / cm². 2 For example, it could be 800mJ / cm 2 1000mJ / cm 21500mJ / cm 2 2000mJ / cm 2 2500mJ / cm 2 3000mJ / cm 2 3500mJ / cm 2 Or 4000mJ / cm 2 wait.

[0099] Preferably, the thermosetting temperature is 90 to 130°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C.

[0100] Preferably, the heat curing time is 1 to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0101] The method for preparing the flexible flat cable described in this invention specifically includes the following steps:

[0102] A heat-pressed insulating film as described in the first aspect is placed on the upper and lower surfaces of the conductor, respectively. After rolling for 2–3 seconds at a temperature of 160–200°C and a pressure of 0.3–0.6 MPa, the film is then subjected to light intensity of 800–4000 mJ / cm². 2 Under the given conditions, light curing is performed for 2–3 seconds, followed by baking at 90–130°C for 1–3 hours to complete thermal curing, thereby obtaining the flexible flat cable.

[0103] Fifthly, the present invention provides an application of the flexible flat cable as described in the third aspect in the field of new energy vehicles.

[0104] Compared with the prior art, the present invention has the following beneficial effects:

[0105] (1) In this invention, by designing the raw materials for preparing the adhesive layer in the hot-pressed insulating film, and further by using modified unsaturated polyester resin, the hot-pressed insulating film prepared has a simple structure and good flame retardant properties, good high temperature and humidity resistance and good thermal shock resistance, which can meet the requirements for long-term outdoor use and is suitable for preparing automotive FFC products.

[0106] (2) The flexible flat cable prepared by the hot-pressed insulating film provided by the present invention has excellent comprehensive performance. The flexible flat cable prepared by the present invention has no blistering around the conductor and no glue overflow at the conductor terminal. The initial peel strength is 104-135gf. After high temperature and high humidity test, the flexible flat cable has no blistering around the conductor and no glue delamination at the conductor edge. The peel strength is 82-108gf and the resistance value is >500Ω. After thermal shock test, the flexible flat cable has no blistering around the conductor and no glue overflow at the conductor terminal. The peel strength is 96-125gf. After flame retardancy test, its flame retardant effect reaches VTM-0. Detailed Implementation

[0107] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0108] The sources of some components in the following preparation examples are as follows:

[0109] Polycarbonate diol: Number average molecular weight 2000, Asahi Kasei T5652 (Japan);

[0110] Polytetrahydrofuran glycol: Number average molecular weight 2000, BASF, Germany 2000;

[0111] Polycaprolactone diol: number average molecular weight of 1000, from Perstork, Sweden, Capa2101A.

[0112] In the saturated polyester resins provided in the following preparation examples, the hydroxyl value is the number of milligrams of potassium hydroxide equivalent to the hydroxyl content in one gram of sample, in mg KOH / g, and the test method refers to DIN 53 240-02; the acid value is the number of milligrams of potassium hydroxide required to neutralize the acidic substances in 1 gram of sample, in mg KOH / g, and the test method refers to DIN EN ISO 2114.

[0113] Preparation Example 1

[0114] This preparation example provides a modified unsaturated polyester resin and its preparation method, the preparation method being as follows:

[0115] (1) Under nitrogen protection, terephthalic acid (5 mol), isophthalic acid (2 mol), sebacic acid (3 mol), neopentyl glycol (6 mol), and 1,6-hexanediol (6 mol) were placed in a stainless steel reactor equipped with a stirrer, cooling pipe and thermometer. The temperature was gradually increased from 150℃ to 200℃ and the esterification reaction was carried out for 5 h to obtain the esterified product.

[0116] (2) After adding polycarbonate diol to the reaction system of step (1), stir for 20 min to mix evenly, then evacuate the reactor for 1 h to reduce the pressure inside the reactor to 500-650 Pa, raise the temperature to 250 °C, continue evacuating the reactor to reduce the pressure inside the reactor to 10-40 Pa, and react at 250 °C for 3 h to obtain a saturated polyester resin with a hydroxyl value of 30 mg KOH / g and an acid value of 0.8 mg KOH / g; wherein, based on the mass percentage of the esterified product being 100%, the mass percentage of the polycarbonate diol is 10%;

[0117] (3) Under nitrogen protection, the saturated polyester resin (150g) and butyl acetate (150g) obtained in step (2) were added to a 500mL three-necked flask with a distillation bridge. After mixing evenly at 80°C, ethyl isocyanate methacrylate (2.8g) was added and reacted for 4h to obtain the modified unsaturated polyester resin.

[0118] Preparation Example 2

[0119] This preparation example provides a modified unsaturated polyester resin and its preparation method, the preparation method being as follows:

[0120] (1) Under nitrogen protection, terephthalic acid (5 mol), succinic acid (2 mol), adipic acid (3 mol), 1,4-butanediol (7 mol), and 1,6-hexanediol (6 mol) were placed in a stainless steel reactor equipped with a stirrer, cooling pipe and thermometer. The temperature was gradually increased from 150℃ to 200℃ and the esterification reaction was carried out for 5 h to obtain the esterified product.

[0121] (2) After adding polytetrahydrofuran diol to the reaction system of step (1), stir for 20 min to mix evenly, then evacuate the reactor for 0.5 h to reduce the pressure inside the reactor to 500-800 Pa, raise the temperature to 250 °C, continue evacuating the reactor to reduce the pressure inside the reactor to 10-50 Pa, and react at 250 °C for 4 h to obtain a saturated polyester resin with a hydroxyl value of 35 mg KOH / g and an acid value of 0.6 mg KOH / g; wherein, based on the mass percentage of the esterified product as 100%, the mass percentage of the polytetrahydrofuran diol is 5%;

[0122] (3) Under nitrogen protection, the saturated polyester resin (150g) and butyl acetate (150g) obtained in step (2) were added to a 500mL three-necked flask with a distillation bridge. After mixing evenly at 70°C, ethyl isocyanate acrylate (2.8g) was added and reacted for 5h to obtain the modified unsaturated polyester resin.

[0123] Preparation Example 3

[0124] This preparation example provides a modified unsaturated polyester resin and its preparation method, the preparation method being as follows:

[0125] (1) Under nitrogen protection, phthalic acid (5 mol), azelaic acid (2 mol), terephthalic acid (3 mol), 1,5-pentanediol (7 mol), and 1,3-propanediol (7 mol) were placed in a stainless steel reactor equipped with a stirrer, cooling pipe and thermometer. The temperature was gradually increased from 150℃ to 200℃ and the esterification reaction was carried out for 5 h to obtain the esterified product.

[0126] (2) After adding polycaprolactone diol to the reaction system of step (1), stir for 20 min to mix evenly, then evacuate the reactor for 1 h to reduce the pressure inside the reactor to 500-650 Pa, raise the temperature to 260 °C, continue evacuating the reactor to reduce the pressure inside the reactor to 10-50 Pa, and react at 260 °C for 3 h to obtain a saturated polyester resin with a hydroxyl value of 28 mg KOH / g and an acid value of 0.4 mg KOH / g; wherein, based on the mass percentage of the esterified product being 100%, the mass percentage of the polycaprolactone diol is 30%;

[0127] (3) Under nitrogen protection, the saturated polyester resin (150g) and butyl acetate (150g) obtained in step (2) were added to a 500mL three-necked flask with a distillation bridge. After mixing evenly at 90°C, ethyl isocyanate acrylate (2.8g) was added and reacted for 3h to obtain the modified unsaturated polyester resin.

[0128] Preparation Example 4

[0129] This preparation example provides a modified unsaturated polyester resin and its preparation method. The only difference from preparation example 1 is that in step (2), the mass percentage of the esterified product is 100%, and the mass percentage of the polycarbonate diol is 5%. The rest is the same as preparation example 1.

[0130] Preparation Example 5

[0131] This preparation example provides a modified unsaturated polyester resin and its preparation method. The only difference from Example 1 is that in step (3), the amount of isocyanate ethyl methacrylate is 0.65g, and the rest is the same as in Preparation Example 1.

[0132] Preparation Example 6

[0133] This preparation example provides a modified unsaturated polyester resin and its preparation method. The only difference from Example 1 is that in step (3), the amount of isocyanate ethyl methacrylate is 5g, and the rest is the same as in Preparation Example 1.

[0134] Example 1

[0135] For details regarding the components used in the following examples and comparative examples, and their sources, please refer to Table 1 below:

[0136] Table 1

[0137] Code or brand Detailed Explanation R1~R6 R1 to R6 are the modified unsaturated polyester resins provided in Preparation Examples 1 to 6, respectively. LA2250 Acrylic block copolymer, purchased from Kuraray, Japan NPES904 Bisphenol A type epoxy resin, purchased from Nan Ya Plastics Factory in Taiwan, China. Photoinitiator 651 Benzoyl dimethyl ether Flame retardant OP935 Phosphonate flame retardant, purchased from Clariant Chemicals MF-B60X Blocked isocyanate resin, purchased from Asahi Kasei, Japan. Curing accelerator Stannous octoate KBM403 Organosilane coupling agent, purchased from Shin-Etsu Chemical, Japan. solvent Butanone Substrate The corona-treated PET film, 38 μm thick, was purchased from Yihua Toray Industries.

[0138] Examples 1-6

[0139] Examples 1-6 provide a hot-pressed insulating film and a method for preparing the same, wherein the hot-pressed insulating film comprises a substrate layer and an adhesive layer that are bonded together;

[0140] The raw materials for preparing the adhesive layer are shown in Table 2, where the content of each component in Table 2 is by weight.

[0141] The adhesive layer is prepared as follows:

[0142] The raw material components of the adhesive layer are mixed evenly to obtain a mixed solution, which is then coated onto the corona-treated side of the PET film. After drying at 80°C for 3 minutes, the temperature is raised to 120°C and dried for 3 minutes to obtain a hot-pressed insulating film with a thickness of 35 μm.

[0143] Table 2

[0144]

[0145] Examples 7-9

[0146] Examples 7-9 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that R1 provided in Example 1 of the adhesive layer preparation raw material preparation is replaced with R4 provided in Example 4 (Example 7), R5 provided in Example 5 (Example 8), and R6 provided in Example 6 (Example 9) in turn.

[0147] Other conditions are the same as in Example 1.

[0148] Examples 10-11

[0149] Examples 10-11 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 15 parts by weight of NPES904 in the raw materials for preparing the adhesive layer in Example 1 are replaced with 5 parts by weight of NPES904 (Example 10) and 30 parts by weight of NPES904 (Example 11).

[0150] Other conditions are the same as in Example 1.

[0151] Examples 12-13

[0152] Examples 12-13 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 15 parts by weight of MF-B60X in the adhesive layer preparation raw materials in Example 1 are replaced with 5 parts by weight of MF-B60X (Example 12) and 20 parts by weight of MF-B60X (Example 13).

[0153] Other conditions are the same as in Example 1.

[0154] Examples 14-15

[0155] Examples 14-15 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 60 parts by weight of flame retardant OP935 in the raw materials for preparing the adhesive layer in Example 1 are replaced with 30 parts by weight of flame retardant OP935 (Example 14) and 120 parts by weight of flame retardant OP935 (Example 15).

[0156] Other conditions are the same as in Example 1.

[0157] Comparative Examples 1-2

[0158] Comparative Examples 1 and 2 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 15 parts by weight of NPES904 in the adhesive layer preparation raw materials in Example 1 are replaced with 3 parts by weight of NPES904 (Comparative Example 1) and 35 parts by weight of NPES904 (Comparative Example 2).

[0159] Other conditions are the same as in Example 1.

[0160] Comparative Examples 3-4

[0161] Comparative Examples 3-4 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 15 parts by weight of MF-B60X in the adhesive layer preparation raw materials in Example 1 are replaced with 1 part by weight of MF-B60X (Comparative Example 3) and 25 parts by weight of MF-B60X (Example 20).

[0162] Other conditions are the same as in Example 1.

[0163] Comparative Examples 5-6

[0164] Comparative Examples 5 and 6 provide a hot-pressed insulating film and its preparation method, respectively. The difference from Example 1 is that 60 parts by weight of flame retardant OP935 in the raw materials for preparing the adhesive layer in Example 1 are replaced with 20 parts by weight of flame retardant OP935 (Comparative Example 5) and 130 parts by weight of flame retardant OP935 (Comparative Example 6).

[0165] Other conditions are the same as in Example 1.

[0166] Application Example 1

[0167] This application example provides a flexible flat cable and a method for its fabrication. The fabrication method is as follows:

[0168] A hot-pressed insulating film provided in Example 1 was placed on the upper and lower surfaces of eight pure copper wires with an online spacing of 1.5 mm. After rolling for 3 seconds at a temperature of 180°C and a pressure of 0.5 MPa, the film was then subjected to light intensity of 2000 mJ / cm². 2 Under the given conditions, light curing is performed for 3 seconds, followed by baking at 120°C for 3 hours to complete the thermal curing, thus obtaining the flexible flat cable.

[0169] Application Example 2-15

[0170] Application Examples 2-15 provide a flexible flat cable and its preparation method, respectively. The difference from Application Example 1 is that the hot-pressed insulating film provided in Example 1 is replaced with the hot-pressed insulating film provided in Examples 2-15 in turn, while other conditions are the same as in Application Example 1.

[0171] Application Comparative Examples 1-6

[0172] Comparative Examples 1-6 provide a flexible flat cable and its preparation method, respectively. The difference from Application Example 1 is that the hot-pressed insulating film provided in Example 1 is replaced with the hot-pressed insulating film provided in Comparative Examples 1-6 in turn, while other conditions are the same as in Application Example 1.

[0173] The performance of the heat-pressed insulating film provided in the above embodiments and comparative examples, as well as the flexible flat cables provided in the application examples and application comparative examples, were tested. The specific test methods are as follows:

[0174] Initial appearance and peel strength: Observe whether there are bubbles around the conductors of the flexible flat cables provided in the above application examples and application comparison examples, and whether there is excess glue at the conductor terminals (top). If the excess glue is >0.3mm, it is NG; if the excess glue is ≤0.3mm, it is OK. Test the peel strength of the flexible flat cables provided in the above application examples and application comparison examples. The test conditions are: 180°, 100mm / min.

[0175] Appearance and peel strength after high temperature and high humidity aging test: The flexible flat cables provided in the above application examples and application comparison examples are placed in a high temperature and high humidity environment chamber for 1500 hours, taken out and cooled to room temperature. Observe whether there are bubbles around the conductor and whether the conductor edge is delaminated. If there are, it is NG, otherwise it is OK. The peel strength of the flexible flat cables provided in the corresponding application examples and application comparison examples is tested. The test conditions are: 180°, 100mm / min.

[0176] Line insulation resistance test: Apply a DC voltage of 500V between two adjacent conductors of the flexible flat cable after the above high temperature and high humidity aging test for 60s, and test its resistance value.

[0177] Appearance and peel strength after thermal shock aging test: The flexible flat cables provided in the above application examples and application comparison examples are placed in a thermal shock environment chamber for 1000 hours, -40℃ / (0.5h), 125℃ / (0.5h), with a thermal switching time of less than 2 minutes. After 1000 cycles, they are taken out and cooled to room temperature. Observe whether there are bubbles around the conductor and whether there is excess glue at the conductor terminal (top). If there are, it is NG, otherwise it is OK. The peel strength of the flexible flat cables provided in the corresponding application examples and application comparison examples is tested under the following conditions: 180°, 100mm / min.

[0178] Flame retardancy: The hot-pressed films provided in the above embodiments and comparative examples were made into 50mm×200mm samples. According to the UL-94 classification of flame retardancy levels for films, the highest flame retardancy level is VTM-0, followed by VTM-1, VTM-2, HB, etc.

[0179] Comprehensive evaluation: The evaluation is based on the data of initial appearance and peel strength, appearance and peel strength after high temperature and high humidity aging test, line insulation resistance test, appearance and peel strength after thermal shock aging test, and flame retardancy.

[0180] "◎" indicates excellent performance: initial appearance OK, initial peel force ≥120gf / mm, high temperature and high humidity appearance OK, peel force ≥100gf / mm, thermal shock appearance OK, peel force ≥100gf / mm, flame retardant VTM-0 rating.

[0181] “○” indicates that the performance is qualified: the initial appearance is OK, the initial peel force is >110gf / mm, the appearance under high temperature and high humidity is OK, the peel force is ≥90gf / mm, the appearance under thermal shock is OK, the peel force is ≥100gf / mm, and the flame retardant VTM-1 level and above.

[0182] "△" indicates that the performance is average: the initial appearance is OK, the initial peel force is >110gf / mm, the appearance is OK under high temperature and high humidity, the peel force is ≥80gf / mm, the appearance is OK under thermal shock, the peel force is ≥90gf / mm, and the flame retardant VTM-2 level and above.

[0183] "×" indicates poor performance: initial appearance NG, or initial peel force <100gf / mm, or high temperature and high humidity appearance NG, or peel force <80gf / mm, thermal shock appearance NG, or peel force <90gf / mm, or flame retardant VTM-2 grade, or insulation resistance <500MΩ.

[0184] The performance test data of the hot-pressed insulating film provided in the above embodiments and comparative examples, as well as the flexible flat cables provided in the application examples and application comparative examples, are shown in Table 3 below:

[0185] Table 3

[0186]

[0187]

[0188] As shown in Table 3, in this invention, by designing the raw materials for preparing the adhesive layer in the hot-pressed insulating film and further using modified unsaturated polyester resin, the prepared hot-pressed insulating film has a simple structure and good flame retardant properties, good high-temperature and high-humidity resistance, and good thermal shock resistance. The flexible flat cable prepared using the hot-pressed insulating film provided by this invention exhibits excellent comprehensive performance. The prepared flexible flat cable has no blistering around the conductors, no adhesive overflow at the conductor terminals, and an initial peel strength of 104–135 gf. After high-temperature and high-humidity testing, the flexible flat cable still has no blistering around the conductors, no adhesive delamination at the conductor edges, a peel strength of 82–108 gf, and a resistance value >500 Ω. After thermal shock testing, the flexible flat cable still has no blistering around the conductors, no adhesive overflow at the conductor terminals, and a peel strength of 96–125 gf. After flame retardancy testing, its flame retardant effect reaches VTM-0.

[0189] Compared with Application Example 1, if the content of modifier in the unsaturated polyester resin used to prepare the adhesive layer of the hot-pressed insulating film in FFC is too high (Application Example 9), the overall performance of the prepared hot-pressed insulating film is poor, and the FFC prepared as a result has poor high temperature and high humidity resistance and thermal shock resistance.

[0190] Compared with Application Example 1, if the epoxy resin content in the hot-pressed insulating film for preparing FFC is too low (Comparative Example 1) or too high (Comparative Example 2), the curing agent content in the hot-pressed insulating film for preparing FFC is too low (Comparative Example 3) or too high (Comparative Example 4), or the flame retardant content in the hot-pressed insulating film for preparing FFC is too low (Comparative Example 5) or too high (Comparative Example 6), the overall performance of the prepared hot-pressed insulating film is poor. Consequently, the FFC prepared has poor high-temperature and high-humidity resistance, thermal shock resistance, and flame retardancy.

[0191] In summary, this invention, through the design of the raw materials for the adhesive layer in the hot-pressed insulating film and the further use of modified unsaturated polyester resin, produces a hot-pressed insulating film with a simple structure and good flame retardant properties, good high-temperature and high-humidity resistance, and good thermal shock resistance. The flexible flat cable prepared using the hot-pressed insulating film provided by this invention exhibits excellent overall performance.

[0192] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A hot-pressed insulating film, characterized in that, The hot-pressed insulating film includes a substrate layer and an adhesive layer that are bonded together; The raw materials for preparing the adhesive layer include the following components in parts by weight: 100 parts modified unsaturated polyester resin, 3-20 parts acrylic rubber, 5-30 parts epoxy resin, 0.1-3 parts initiator, 5-30 parts curing agent, and 30-120 parts flame retardant. The raw materials for preparing the modified unsaturated polyester resin include: diacid monomers and / or acid anhydrides, diol monomers, oligomeric polyols, and modifiers. The modifier is a compound containing unsaturated double bonds and isocyanate groups; The modified unsaturated polyester resin is prepared by the following method, which includes the following steps: (1) In a protective atmosphere, place the diacid monomer and / or acid anhydride and diol monomer in a reaction vessel and carry out an esterification reaction to obtain the esterified product; (2) After adding oligomeric polyols to the reaction system of step (1), the mixture is stirred and subjected to polycondensation reaction to obtain saturated polyester resin; (3) In a protective atmosphere, the saturated polyester resin obtained in step (2) is dissolved in an organic solvent, a modifier is added to it, and a modification reaction is carried out to obtain the modified unsaturated polyester resin. Based on the mass percentage of the esterified compound being 100%, the mass percentage of the oligomeric polyol is 5% to 30%. With the saturated polyester resin having a hydroxyl molar percentage of 100%, the modifier has a molar percentage of 1% to 30%.

2. The hot-pressed insulating film according to claim 1, characterized in that, The dicarboxylic acid monomer is selected from any one or a combination of at least two of phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid, adipic acid, or azelaic acid.

3. The hot-pressed insulating film according to claim 1, characterized in that, The acid anhydride is selected from any one or a combination of at least two of phthalic anhydride, succinic anhydride, adipic anhydride, and azelaic anhydride.

4. The hot-pressed insulating film according to claim 1, characterized in that, The diol monomer is an alkylene diol with ≥3 carbon atoms.

5. The hot-pressed insulating film according to claim 4, characterized in that, The diol monomer is selected from any one or a combination of at least two of the following: propylene glycol, polypropylene glycol, 2-methyl-1,3-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentanediol, 2-methyl-2-ethyl-1,3-propanediol, or 1,4-cyclohexanediol.

6. The hot-pressed insulating film according to claim 1, characterized in that, The oligomeric polyol is selected from any one or a combination of at least two of polypropylene glycol, polytetrahydrofuran glycol, polycarbonate glycol, and polycaprolactone glycol.

7. The hot-pressed insulating film according to claim 1, characterized in that, The number average molecular weight of the oligomeric polyol is 500~3000.

8. The hot-pressed insulating film according to claim 1, characterized in that, The modifier is selected from ethyl isocyanate methacrylate and / or ethyl isocyanate acrylate.

9. The hot-pressed insulating film according to claim 1, characterized in that, The glass transition temperature of the modified unsaturated polyester resin is 5~40℃.

10. The hot-pressed insulating film according to claim 9, characterized in that, The glass transition temperature of the modified unsaturated polyester resin is 5~30℃.

11. The hot-pressed insulating film according to claim 1, characterized in that, The ratio of the amount of the dicarboxylic acid monomer and / or anhydride to the amount of the diol monomer is 1:(1.2~1.4).

12. The hot-pressed insulating film according to claim 1, characterized in that, With the saturated polyester resin having a hydroxyl molar percentage of 100%, the modifier has a molar percentage of 2% to 25%.

13. The hot-pressed insulating film according to claim 1, characterized in that, The limiting viscosity IV of the saturated polyester resin is 0.3~1.0 dl / g.

14. The hot-pressed insulating film according to claim 13, characterized in that, The limiting viscosity IV of the saturated polyester resin is 0.3~0.8 dl / g.

15. The hot-pressed insulating film according to claim 1, characterized in that, The temperature of the modification reaction in step (3) is 70~90℃.

16. The hot-pressed insulating film according to claim 1, characterized in that, The modification reaction in step (3) takes 3 to 5 hours.

17. The hot-pressed insulating film according to claim 1, characterized in that, The acrylic rubber is selected from any one or a combination of at least two of polyethylene-acrylate rubber, polyacrylate rubber, or acrylic block copolymers.

18. The hot-pressed insulating film according to claim 1, characterized in that, The epoxy resin is selected from any one or a combination of at least two of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, or phenolic type epoxy resin.

19. The hot-pressed insulating film according to claim 1, characterized in that, The initiator is a photoinitiator.

20. The hot-pressed insulating film according to claim 1, characterized in that, The curing agent is a blocked isocyanate curing agent.

21. The hot-pressed insulating film according to claim 1, characterized in that, The flame retardant is selected from any one or a combination of at least two of the following: brominated flame retardants, phosphorus-based flame retardants, phosphorus-aluminum flame retardants, nitrogen-based flame retardants, silicon-based flame retardants, metal hydroxide flame retardants, metal oxide flame retardants, or metal boride flame retardants.

22. The hot-pressed insulating film according to claim 21, characterized in that, The flame retardant is any one or a combination of at least two of the following: phosphorus-based flame retardants, phosphorus-aluminum-based flame retardants, and nitrogen-based flame retardants.

23. The hot-pressed insulating film according to claim 1, characterized in that, The raw materials for preparing the adhesive layer also include 0.1 to 1 part of a curing accelerator.

24. The hot-pressed insulating film according to claim 23, characterized in that, The curing accelerator is selected from organic amine curing accelerators and / or metal salt curing accelerators.

25. The hot-pressed insulating film according to claim 1, characterized in that, The raw materials for preparing the adhesive layer also include 0.5 to 2 parts of antioxidant.

26. The hot-pressed insulating film according to claim 1, characterized in that, The raw materials for preparing the adhesive layer also include 0.1 to 2 parts of dispersing agent.

27. The hot-pressed insulating film according to claim 26, characterized in that, The dispersing agent is selected from any one or a combination of at least two of the following: titanate coupling agents, aluminate coupling agents, organosilane coupling agents, organochromium complex coupling agents, or borate coupling agents.

28. A method for preparing a hot-pressed insulating film as described in any one of claims 1-27, characterized in that, The preparation method includes the following steps: The raw materials for preparing the adhesive layer are mixed with a solvent to obtain a mixed solution, which is then coated onto one side of the substrate and dried to obtain the hot-pressed insulating film.

29. The preparation method according to claim 28, characterized in that, The substrate is a corona-treated PET film.

30. The preparation method according to claim 28, characterized in that, The specific drying method includes: drying at 70~90℃ for 2~5 min, then raising the temperature to 110~130℃ and drying for 2~5 min.

31. The preparation method according to claim 28, characterized in that, The thickness of the adhesive layer in the hot-pressed insulating film is 15~100 μm.

32. The preparation method according to claim 31, characterized in that, The thickness of the adhesive layer in the hot-pressed insulating film is 17~80 μm.

33. A flexible flat cable, characterized in that, The flexible flat cable includes at least three conductors and a heat-pressed insulating film as described in any one of claims 1-27 covering both sides of the conductor surface.

34. The flexible flat cable according to claim 33, characterized in that, The conductor is a pure copper conductor, a tin-plated copper conductor, or a nickel-plated copper conductor.

35. The flexible flat cable according to claim 33, characterized in that, The spacing between any two adjacent conductors is 1 to 2 mm.

36. A method for preparing a flexible flat cable as described in any one of claims 33-35, characterized in that, The preparation method includes the following steps: A thermo-pressed insulating film as described in any one of claims 1-27 is placed on the upper and lower surfaces of the conductor, and after roll pressing, it is sequentially photocured and thermo-cured to obtain the flexible flat cable.

37. The preparation method according to claim 36, characterized in that, The rolling temperature is 160~200℃.

38. The preparation method according to claim 36, characterized in that, The pressure of the roller is 0.3~0.6 MPa.

39. The preparation method according to claim 36, characterized in that, The rolling time is 2~3 seconds.

40. The preparation method according to claim 36, characterized in that, The photocuring time is 2-3 seconds.

41. The preparation method according to claim 36, characterized in that, The light intensity of the photocuring process is 800~4000 mJ / cm². 2 .

42. The preparation method according to claim 36, characterized in that, The thermosetting temperature is 90~130℃.

43. The preparation method according to claim 36, characterized in that, The thermosetting time is 1~3 hours.

44. An application of the flexible flat cable as described in any one of claims 33-35 in the field of new energy vehicles.

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