Transparent flame-retardant coating, transparent flame-retardant hot-pressing film, and preparation method and application thereof

Abstract

The present invention relates to the technical field of hot-pressing films, in particular to a transparent flame-retardant coating, a transparent flame-retardant hot-pressing film, and their preparation methods and applications. The present application discloses a transparent flame-retardant coating, which, by weight, comprises the following raw materials: tackifying resin: 50-80 parts, bisphenol A epoxy resin: 38-45 parts, phenol-type epoxy resin: 19-25 parts, solvent-type epoxy resin: 0-15 parts, flame retardant: 70-90 parts, 4,4'-diaminodiphenyl sulfone: 4-8 parts, dicyandiamide curing agent: 0.5-0.8 parts, accelerator A: 0.1-0.5 parts, accelerator B: 4-7 parts, silane coupling agent: 1-3 parts, solvent: 480-700 parts. The transparent flame-retardant hot-pressing film prepared by the present application can achieve non-adhesion to the adhered and adhered steel plate or aluminum plate before hot pressing, adhesion to the adhered and adhered steel plate or aluminum plate after hot pressing, and return to the non-adhesive state before hot pressing after curing.

Description

Technical Field

[0001] The present invention relates to the technical field of hot-pressing films, in particular to a transparent flame-retardant coating, a transparent flame-retardant hot-pressing film, and their preparation methods and applications. Background Art

[0002] The main functions of the flame-retardant hot-pressing film are: flame retardancy, insulation, adhesiveness, and shaping. The flame-retardant hot-pressing film is mainly used for: (1) the protection, fixation, insulation, and flame retardancy of electronic components; (2) the lamination of metal parts such as steel sheets and aluminum sheets; (3) the coating of lithium batteries and power batteries, in the photovoltaic field; (4) oral correction.

[0003] Existing flame-retardant hot-pressing films are generally composite materials composed of a PET substrate and a coating containing a flame retardant, which are prepared by a coating process. In order to ensure that the coating can adhere to the PET substrate, general coatings contain adhesives, so it is difficult to make the flame-retardant PET film non-sticky at room temperature, and it is easy to stick together after folding and pasting.

[0004] Further analysis reveals that polyethylene terephthalate (PET) is a commonly used polymer material with good electrical insulation, fatigue resistance, aging resistance, and abrasion resistance, but the flame retardancy of PET is relatively low. The substrates of many functional films are made of PET. Due to the high requirements for the flame retardancy of materials in applications such as electronics and new energy, it is necessary to improve the flame retardancy of PET. Generally, to achieve the flame retardant performance of PET, it is necessary to block the combustion reaction at the reaction mechanism level, so as to form a combustion blocking layer, including core-shell structures such as an oxygen isolation layer and a refractory layer, to block the continuous occurrence of combustion from both physical and chemical aspects; the methods to achieve the flame retardant performance of PET include adding a flame retardant to the PET substrate by the flame retardant method, monomer reaction copolymerization flame retardant method, and high-temperature cross-linking flame retardant modification of PET. In the method of adding a flame retardant to the PET substrate, the flame retardant is generally a coating composed of an adhesive, a filler, a solvent, and an additive, and the flame retardant is attached to the PET substrate by coating to form a composite material. However, this composite material generally has adhesiveness at room temperature and the adhesiveness is weak, and it is easy to automatically bounce off in environments such as high temperature, vibration, and moisture after pasting, causing potential safety hazards. Moreover, although the PET substrate modified with a flame retardant has flame retardancy, due to the instability of polymer materials, it is not easy to meet the VTM-0 standard in the UL94 standard, that is, the sum of the afterflame time t 1 and t 2 is less than 10 s. In addition, the modified PET substrate is generally stored and transported in the form of rolls. When the rolls are rolled to roll and the film is handled, stored, and used, it is very easy to contact each other, resulting in scrapping.

[0005] Therefore, the present application provides a transparent flame-retardant coating, a transparent flame-retardant hot-pressing film, and their preparation methods and applications, which have no adhesiveness when in contact with each other at room temperature, have strong adhesiveness at high temperature, are difficult to automatically bounce off, and have good flame retardancy. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present application provides a transparent flame-retardant coating, a transparent flame-retardant hot-pressing film, and their preparation methods and applications. The prepared transparent flame-retardant hot-pressing film does not adhere to the steel plate or aluminum plate before hot pressing, adheres to the steel plate or aluminum plate after hot pressing, and returns to the non-adhesive state before hot pressing after curing.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0008] The first object of the present invention is to provide a transparent flame-retardant coating, which includes the following raw materials in parts by weight:

[0009] Tackifying resin: 50 - 80 parts

[0010] Bisphenol A epoxy resin: 38 - 45 parts

[0011] Phenolic epoxy resin: 19 - 25 parts

[0012] Solvent-based epoxy resin: 0 - 15 parts

[0013] Flame retardant: 70 - 90 parts

[0014] 4,4'-Diaminodiphenyl sulfone: 4 - 8 parts

[0015] Dicyandiamide curing agent: 0.5 - 0.8 part

[0016] Accelerator A: 0.1 - 0.5 part

[0017] Accelerator B: 4 - 7 parts

[0018] Silane coupling agent: 1 - 3 parts.

[0019] Preferably, the tackifying resin is any one or several of hydrogenated nitrile rubber, solid phenolic resin, polyketone resin, petroleum resin, rosin resin, and terpene resin.

[0020] Preferably, the flame retardant is any one or several of aluminum diethylphosphinate (ADP), antimony trioxide, magnesium hydroxide, aluminum hydroxide, alkyl phosphate esters (tributyl phosphate or tricresyl phosphate), dicyclopentadiene, borates (calcium metaborate or barium metaborate), triazines and their derivatives, and bromotrichloromethane.

[0021] Preferably, the accelerator A is an organic urea accelerator.

[0022] Preferably, the accelerator B is a modified aromatic amine accelerator.

[0023] Preferably, the silane coupling agent is any one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0024] Preferably, it further includes a solvent: 480 - 700 parts, and the solvent is methyl ethyl ketone or DMF.

[0025] The second object of the present invention is to provide a transparent flame-retardant hot-pressed film, which includes a PET substrate and a transparent flame-retardant coating coated on one or both sides of the PET substrate, and the transparent flame-retardant coating is formed after curing the above-mentioned transparent flame-retardant paint.

[0026] Preferably, the thickness of the PET substrate is 40 - 60 μm, and the thickness of the transparent flame-retardant coating is 20 - 30 μm.

[0027] Preferably, the solvent-based epoxy resin is bisphenol A epoxy resin.

[0028] The third object of the present invention is to provide a preparation method of a transparent flame-retardant hot-pressed film, which includes the following steps:

[0029] S1. Preparation of the transparent flame-retardant paint

[0030] Prepare materials according to the respective weight parts of the raw materials for the transparent flame-retardant paint;

[0031] Fully mix the tackifying resin, bisphenol A epoxy resin, phenol-type epoxy resin, solvent-based epoxy resin, and part of the solvent to obtain solution A;

[0032] Mix the flame retardant, coupling agent, and part of the solvent to obtain mixture B;

[0033] Fully mix solution A and mixture B to obtain mixture C;

[0034] Fully mix 4,4'-diaminodiphenyl sulfone, accelerator A, and part of the solvent to obtain solution D;

[0035] Fully mix the dicyandiamide curing agent, accelerator B, and part of the solvent to obtain solution E;

[0036] Fully mix mixture C, solution D, and solution E to obtain the transparent flame-retardant paint;

[0037] S2. Preparation of the wet film and the dry film

[0038] Coat the transparent flame-retardant paint on the PET substrate; after coating, obtain a wet film, stick on a protective film; bake to obtain a dry film;

[0039] S3. Preparation of the hot-pressed film

[0040] The dry film is hot-pressed to obtain a prefabricated flame-retardant film; then it is further subjected to curing treatment to obtain a transparent flame-retardant hot-pressed film.

[0041] The fourth object of the present invention is to provide an application of the transparent flame-retardant hot-pressed film, and the above-mentioned transparent flame-retardant hot-pressed film is used for the bonding of electronic components, the bonding of metal parts, and the coating of lithium batteries and power batteries.

[0042] The beneficial effects of the present invention are:

[0043] The transparent flame-retardant hot-pressed film prepared in this application has the characteristics that it does not adhere to the sticker and the steel plate or aluminum plate before hot pressing, adheres to the sticker and the steel plate or aluminum plate after hot pressing, and returns to the non-adhesive state before hot pressing after curing. The light transmittance is greater than 90%, and the flame retardancy is VTM-0 (the sum of the afterflame time t 1 and t 2 is 2.9 - 5.4 s). It has no stickiness to the sticker before hot pressing, and the 90° peel strength is greater than 8 N / cm after hot pressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the drawings and embodiments.

[0045] Figure 1 is a schematic structural diagram of the transparent flame-retardant hot-pressed film;

[0046] Figure 2 is a process flow chart of the preparation method of the transparent flame-retardant hot-pressed film;

[0047] Figure 3 is a schematic diagram of the change in stickiness of the transparent flame-retardant hot-pressed film before and after hot pressing and after curing;

[0048] Figure 4 is the influence result of different contents of nitrile rubber on the peel strength of the transparent flame-retardant hot-pressed film;

[0049] Figure 5 is the influence result of different contents of ADP flame retardant on the flame retardant performance of the transparent flame-retardant hot-pressed film. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] In this application, each raw material is commercially available, and the sources of some raw materials of the transparent flame-retardant coating are as follows:

[0051] Table 1 Sources of Some Raw Materials

[0052]

[0053] In order to provide a hot-pressed film that has no stickiness in contact with the sticker at room temperature, has strong stickiness at high temperature, is difficult to automatically bounce off, and has good flame retardancy, this application provides a transparent flame-retardant coating, a transparent flame-retardant hot-pressed film, its preparation method and application.

[0054] A transparent flame retardant coating, in parts by weight, comprises the following raw materials:

[0055] Tackifying resin: 50 - 80 parts

[0056] Bisphenol A epoxy resin: 38 - 45 parts

[0057] Phenol epoxy resin: 19 - 25 parts

[0058] Solvent-based epoxy resin: 0 - 15 parts

[0059] Flame retardant: 70 - 90 parts

[0060] 4,4'-Diaminodiphenyl sulfone: 4 - 8 parts

[0061] Dicyandiamide curing agent: 0.5 - 0.8 part

[0062] Accelerator A: 0.1 - 0.5 part

[0063] Accelerator B: 4 - 7 parts

[0064] Silane coupling agent: 1 - 3 parts.

[0065] Wherein: the tackifying resin is any one or several of hydrogenated nitrile rubber, solid phenolic resin, polyketone resin, petroleum resin, rosin resin, terpene resin.

[0066] Wherein: the flame retardant is any one or several of aluminum diethyl phosphinate (ADP), antimony trioxide, magnesium hydroxide, aluminum hydroxide, alkyl phosphate esters (tributyl phosphate or tricresyl phosphate), dicyclopentadiene, borates (calcium metaborate or barium metaborate), triazines and their derivatives, bromotrichloromethane.

[0067] Wherein: the accelerator A is an organic urea accelerator.

[0068] Wherein: the accelerator B is a modified aromatic amine accelerator.

[0069] Wherein: the silane coupling agent is any one or several of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane.

[0070] Wherein: it further comprises a solvent: 480 - 700 parts, and the solvent is methyl ethyl ketone or DMF.

[0071] The preparation method of the transparent flame retardant coating has a process flow as Figure 2 shown, and comprises the following steps:

[0072] S1. Weigh 50% methyl ethyl ketone (accounting for the total amount of added methyl ethyl ketone by mass), nitrile rubber, bisphenol A diglycidyl ether, and DCPD phenol epoxy resin separately, and mix them evenly. The mixing method is mechanical stirring for 10 - 30 min at a rotation speed of 600 r / min to obtain solution A.

[0073] S2. Weigh 40% methyl ethyl ketone, ADP flame retardant, and silane coupling agent by mass and mix them evenly. The mixing method is ultrasonic stirring for 20 - 40 min at a rotation speed of 600 r / min, or mechanical stirring for 30 min at a rotation speed of 900 r / min to obtain mixture B.

[0074] S3. Mix solution A and mixture B together and stir ultrasonically for 50 min at a rotation speed of 600 r / min to obtain mixture C.

[0075] S4. Prepare dicyandiamide solution: Weigh a part of dicyandiamide curing agent, organic urea curing accelerator, and N,N - dimethylformamide by mass, seal and stir ultrasonically for 10 min at a rotation speed of 600 r / min to obtain dicyandiamide solution.

[0076] S5. Prepare DDS solution: Weigh 10% methyl ethyl ketone, 4,4'-diaminodiphenyl sulfone, and adhesion promoter by mass and mix them evenly, seal and stir ultrasonically for 10 min at a rotation speed of 600 r / min to obtain DDS solution.

[0077] S6. Mix mixture C, dicyandiamide solution, and DDS solution together, stir with an electric stirrer at a high speed (1500 r / min) for 10 - 30 min, and then filter through a double - layer 300 - mesh filter screen. The above processes are all carried out at room temperature. The slurry obtained after filtration is a transparent flame - retardant coating.

[0078] The transparent flame - retardant hot - press film includes a PET substrate and a transparent flame - retardant coating coated on one or both sides of the PET substrate. The transparent flame - retardant coating is formed after curing the above - mentioned transparent flame - retardant coating.

[0079] As Figure 2 shown, the preparation method of the single - sided transparent flame - retardant hot - press film includes the following steps:

[0080] S1. Coat the transparent flame - retardant coating on the flame - retardant PET substrate on one side. The coating method is one of knife coating, spraying, and roll coating. After coating, stick on a single - sided protective film to obtain a wet film, and bake it at 100 °C for 2 min to obtain a dry film.

[0081] S2. Hot - press the dry film at 170 °C and 0.7 MPa for 15 min to obtain a pre - formed flame - retardant film, and then cure it at 150 °C for 1 h or at 70 °C for 12 h to obtain the single - sided transparent flame - retardant hot - press PET film.

[0082] As Figure 2 shown, the preparation method of the double-sided transparent flame-retardant hot-pressing film includes the following steps:

[0083] S1. Double-sidedly coat the transparent flame-retardant coating on the flame-retardant PET substrate. The coating method is one of dip coating, knife coating, spraying, and roll coating. After coating, stick protective films on both sides to obtain a wet film, and bake it at 100°C for 2 minutes to obtain a dry film;

[0084] S2. Hot-press the dry film at 170°C and 0.7 MPa for 15 minutes to obtain a prefabricated flame-retardant film, and then cure it at 150°C for 1 hour or at 70°C for 12 hours to obtain a transparent flame-retardant PET double-sided hot-pressing film.

[0085] Therefore, the above-mentioned transparent flame-retardant hot-pressing film, as Figure 1 shown, includes a PET substrate and a transparent flame-retardant coating coated on one or both sides of the PET substrate. The transparent flame-retardant coating is formed after curing the above-mentioned transparent flame-retardant coating.

[0086] The reason why the prepared transparent flame-retardant PET hot-pressing film has no adhesion or low adhesion before hot pressing and has adhesion after hot pressing is that it is solid before hot pressing. As the temperature rises, the macromolecular compounds diffuse and combine with the thermal movement, thereby forming a strong bond with the molecules of the adherend by mutual entanglement of the adhesive film.

[0087] Therefore, the prepared transparent flame-retardant PET hot-pressing film has the characteristics of non-adhesion to each other and non-adhesion to steel plates or aluminum plates before hot pressing, adhesion to each other and adhesion to steel plates or aluminum plates after hot pressing, and becoming non-adhesive before hot pressing after curing, and can be applied to the bonding of electronic components, the bonding of metal parts, and the coating of lithium batteries and power batteries.

[0088] Term Explanation:

[0089] Flame retardancy: Evaluate the ability of a material to extinguish after being ignited. The commonly used standard is UL94, which includes a total of 12 fire protection grades: HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VTM-2, HBF, HF1, HF2.

[0090] Adhesive film: Refers to a film with adhesiveness, generally composed of a substrate and glue.

[0091] Hot-pressing film: Refers to a film whose bonding performance is improved by a hot-pressing process. Hot pressing means applying a vertical pressure to a sample at a certain temperature and pressure.

[0092] Transparent: Refers to the light transmittance of a material. The greater the light transmittance, the higher the transparency.

[0093] For the convenience of those skilled in the art, the present invention will be further described below in conjunction with embodiments. The content mentioned in the embodiments does not limit the present invention.

[0094] Example 1:

[0095] For the transparent flame retardant coating, the mass parts of the raw material formula are as follows:

[0096] 55 parts of tackifying resin (nitrile rubber), 38 parts of bisphenol A diglycidyl ether, 19 parts of DCPD phenol epoxy resin, 450 parts of methyl ethyl ketone, 71 parts of ADP flame retardant, 0.67 parts of dicyandiamide curing agent, 0.16 parts of organic urea curing accelerator, 4 parts of DMF, 4 parts of 4,4'-diaminodiphenyl sulfone, 4 parts of modified aromatic amine adhesion promoter, 1 part of silane coupling agent (vinyltriethoxysilane).

[0097] The transparent flame retardant hot-pressing film comprises a PET substrate and a transparent flame retardant coating coated on one or both sides of the PET substrate, and the transparent flame retardant coating is formed after curing the above-mentioned transparent flame retardant coating.

[0098] The preparation method of the transparent flame retardant hot-pressing film comprises the following steps:

[0099] Weigh acrylonitrile-butadiene rubber, bisphenol A diglycidyl ether, DCPD phenol epoxy resin, and 225 parts of methyl ethyl ketone according to the mass parts, put them into a container, and mechanically stir for 10 min at a rotation speed of 600 r / min to obtain solution A;

[0100] Weigh 180 parts of methyl ethyl ketone, ADP flame retardant, and silane coupling agent according to the mass parts, add them to the container while stirring, and after all the raw materials are added, stir with an electric stirrer for 30 min at a rotation speed of 900 r / min to obtain mixture B;

[0101] Mix solution A and mixture B together, stir ultrasonically for 50 min at a rotation speed of 600 r / min to obtain mixture C. Prepare dicyandiamide solution and DDS solution according to the experimental steps in the preparation process. Add the dicyandiamide solution and DDS solution to mixture C, stir with an electric stirrer at a high speed (1500 r / min) for 20 min, and then filter with a double-layer 300-mesh filter screen. The above processes are all carried out at room temperature, and the flame retardant slurry is obtained after filtration;

[0102] Coat the flame retardant slurry on the flame retardant PET substrate on one side, and the coating method is one of scraping, spraying, and roll coating. After coating, stick a single-sided protective film to obtain a wet film, and bake it at 100 °C for 2 min to obtain a dry film;

[0103] Hot-press the dry film at 170 °C and 0.7 MPa for 15 min to obtain a prefabricated flame retardant film, and then cure it at 150 °C for 1 h to obtain a transparent flame retardant PET single-sided hot-pressing film.

[0104] Through testing, the properties of the obtained transparent flame-retardant PET single-sided hot-pressed film are as follows: the 90° peel strength is 8.4 N / cm, the flame-retardant property is VTM-0 grade, it does not stick when pasted, the appearance is flat without bubbles, the properties are uniform at different positions, the light transmittance is greater than 92%, the sample before hot pressing can be moved freely on a steel plate or aluminum plate at room temperature and the adhesive layers do not stick to each other when pasted face to face, and after hot pressing, the adhesion to the steel plate or aluminum plate is greater than 8 N / cm and it sticks when pasted face to face. After curing after hot pressing, the adhesion drops to the level before hot pressing, as Figure 3 shown.

[0105] Example 2:

[0106] In the raw materials of the transparent flame-retardant coating, the nitrile rubber is changed to 0 parts, 20 parts, 30 parts, 45 parts, 52 parts, 60 parts, 70 parts, and 85 parts respectively to obtain transparent flame-retardant PET single-sided hot-pressed films with different nitrile rubber contents, and other conditions are the same as those in Example 1. The peel force of the sample is the 90° peel strength tested by the adhesion test of the hot-pressed film to the aluminum plate, and the test results are as Figure 4 shown.

[0107] Example 3:

[0108] In the raw materials of the transparent flame-retardant coating, the ADP flame retardant is changed to 0 parts, 20 parts, 40 parts, 60 parts, and 80 parts respectively to obtain transparent flame-retardant PET single-sided hot-pressed films with different ADP flame retardant contents, and other conditions are the same as those in Example 1. The test results are as Figure 5 shown.

[0109] Example 4:

[0110] In the raw materials of the transparent flame-retardant coating, the dicyandiamide solution composed of dicyandiamide curing agent, organic urea curing accelerator, and DMF is not contained, and a transparent flame-retardant PET single-sided hot-pressed film without dicyandiamide is obtained. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0111] Example 5:

[0112] In the raw materials of the transparent flame-retardant coating, the silane coupling agent is not contained, and a transparent flame-retardant PET single-sided hot-pressed film without silane coupling agent is obtained. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0113] Example 6:

[0114] In the raw materials of the transparent flame-retardant coating, 0 parts, 10 parts, and 20 parts of solvent-based bisphenol A epoxy resin are additionally added to obtain transparent flame-retardant PET single-sided hot-pressed films with increased resin content. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0115] Example 7:

[0116] In the preparation method of the transparent flame-retardant hot-pressed film, no curing treatment is performed after hot pressing to obtain a transparent flame-retardant PET single-sided hot-pressed film without curing treatment. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0117] Example 8:

[0118] In the preparation method of the transparent flame-retardant hot-pressed film, the stirring time for stirring solution A and mixture B to obtain mixture C is adjusted to 10 min to obtain a transparent flame-retardant PET single-sided hot-pressed film with different stirring times. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0119] Example 9:

[0120] In the raw materials of the transparent flame-retardant coating, 20 parts of antimony trioxide and 10 parts of metal microfibers are added to obtain a flame-retardant PET single-sided hot-pressed film. Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0121] Example 10:

[0122] The transparent flame-retardant coating, in parts by weight, comprises the following raw materials:

[0123] Tackifying resin: 30 parts of hydrogenated nitrile rubber, 10 parts of solid phenolic resin, 10 parts of polyketone resin;

[0124] Bisphenol A epoxy resin: 38 parts

[0125] Phenol-type epoxy resin: 19 parts

[0126] Flame retardant: 30 parts of antimony trioxide, 30 parts of magnesium hydroxide, 10 parts of aluminum hydroxide;

[0127] 4,4'-Diaminodiphenyl sulfone: 4 parts

[0128] Dicyandiamide curing agent: 0.5 part

[0129] Organic urea accelerator: 0.1 part

[0130] Modified aromatic amine accelerator: 4 parts

[0131] Silane coupling agent: 1 part of vinyltrimethoxysilane;

[0132] Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0133] Example 11:

[0134] The transparent flame-retardant coating, in parts by weight, comprises the following raw materials:

[0135] Tackifying resin: 40 parts of hydrogenated nitrile rubber, 20 parts of petroleum resin, 20 parts of rosin resin;

[0136] Bisphenol A epoxy resin: 45 parts

[0137] Phenolic epoxy resin: 25 parts

[0138] Flame retardant: 40 parts of alkyl phosphate, 30 parts of dicyclopentadiene, 20 parts of borate

[0139] 4,4'-Diaminodiphenyl sulfone: 8 parts

[0140] Dicyandiamide curing agent: 0.8 part

[0141] Organic urea accelerator: 0.5 part

[0142] Modified aromatic amine accelerator: 7 parts

[0143] Silane coupling agent: 1 part of vinyltriethoxysilane, 1 part of vinyltrimethoxysilane, 1 part of vinyltris(β-methoxyethoxy)silane

[0144] Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0145] Example 12:

[0146] Transparent flame-retardant coating, in parts by weight, comprising the following raw materials:

[0147] Tackifying resin: 30 parts of hydrogenated nitrile rubber, 30 parts of terpene resin

[0148] Bisphenol A epoxy resin: 40 parts

[0149] Phenolic epoxy resin: 22 parts

[0150] Flame retardant: 40 parts of triazine and its derivatives, 40 parts of bromotrichloromethane

[0151] 4,4'-Diaminodiphenyl sulfone: 5 parts

[0152] Dicyandiamide curing agent: 0.7 part

[0153] Organic urea accelerator: 0.3 part

[0154] Modified aromatic amine accelerator: 5 parts

[0155] Silane coupling agent: 1 part of vinyltriethoxysilane, 1 part of vinyltrimethoxysilane

[0156] Other conditions are the same as those in Example 1, and the test results are shown in Table 1.

[0157] Example 13:

[0158] It is the same as Formulation Example 1. The flame retardant slurry is coated on both sides of the flame retardant PET substrate. The coating method is one of knife coating, roll coating, and dip coating. After coating, a double-sided protective film is pasted to obtain a wet film, which is baked at 100 °C for 2 min to obtain a dry film. The other conditions are the same as those in Example 1 to obtain a transparent flame retardant PET double-sided hot-pressed film. The test results are shown in Table 1.

[0159] The flame retardant PET single-sided or double-sided hot-pressed films prepared in the above Examples 1-13 were subjected to the following performance tests. The test methods (processes) or test standards involved are summarized in Table 1 below:

[0160] 1. 90° peel strength (before curing after hot pressing)

[0161] The 90° peel strength was tested according to the GBT 2792-2014 standard. A constant speed 90° peel strength testing machine was used, and the automatic recorder recorded the value at least once every 1 mm of adhesive tape peeled off. The specific steps were as follows: (1) Cut the sample and clean the stainless steel test plate; (2) Attach the cut sample to the cleaned stainless steel test plate, let it stand for 10 min, and then tear off the release film; (3) Peel off a section of the tape (about 10-20 mm) from one end of the test plate for clamping. The peeled end faces outward, fix the stainless steel plate to the 90° test platform, adjust the initial position of the upper clamp, and zero. Keep the peeled section of the tape at 90° to the plane and fix it with the upper clamp; (4) Set the test parameters, start the testing machine, peel the sample from the surface of the stainless steel test plate, and observe the effective section peeling curve from the computer.

[0162] 2. Flame retardant performance

[0163] The flame retardant performance was tested according to the UL94 standard. The specific method was as follows: (1) Cut a sample with a length and width of 200 mm × 50 mm, make a marking line at a place 125 mm along the length, wind it around a round bar with a diameter of 12.7, and stick the upper end firmly with double-sided adhesive; (2) The test direction was the vertical direction, 10 mm away from the fire source, the flame height was 20 mm, the application time and number of times of the flame were 3 s / time, 2 times; (3) Adjust the flame height to 20 mm, the first application time of the flame was 3 s, anneal and record the flaming combustion time t1, the second application time of the flame was 3 s, anneal and record the flaming combustion time t2 and the non-flaming combustion time t3, and record whether it burned more than the 125 mm marking line and whether there were drips to ignite the absorbent cotton below.

[0164] 3. Laminating performance: The laminating performance is carried out according to the standard of the adhesion test method GB / T2792-2014. The specific steps are as follows: (1) Divide the sample evenly in half along the midline and laminate them together; (2) Roll back and forth three times (each back and forth counts as one time) with 2±0.05 kg, the rolling speed is 300 mm / min, and let it stand for 20 min; (3) Use the peeling equipment to conduct a 180° peeling test at a speed of 300±10 mm / min, and record the reading value.

[0165] 4. Appearance: Observe by both visual and microscope methods to judge whether there are problems such as residual glue, bubbles, pockmarks, defects, wrinkles, small holes, etc.

[0166] 5. Performance uniformity at different positions: Take 5 evenly distributed positions in each sample for various performance tests, and then compare the performance difference ratios of the 5 positions.

[0167] 6 Transmittance: The transmittance is tested by a transmittance / haze tester according to ASTM D1003 standard. Place the sample in front of the test hole, clamp it and conduct the test, and read the specific transmittance value through the tester.

[0168] The test results are shown in Table 2 below.

[0169] Table 2

[0170]

[0171] Note: The flame retardant performance refers to the sum of the flaming combustion times t 1 and t 2 of each specimen.

[0172] The above embodiments are the preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. Transparent flame-retardant coating, characterized in that, by weight, it comprises the following raw materials: Tackifying resin: 50 - 80 parts Bisphenol A diglycidyl ether epoxy resin: 38 - 45 parts DCPD phenol epoxy resin: 19 - 25 parts Bisphenol A type epoxy resin: 0 - 15 parts Flame retardant: 70 - 90 parts 4,4'-Diaminodiphenyl sulfone: 4 - 8 parts Dicyandiamide curing agent: 0.5 - 0.8 part Accelerator A: 0.1 - 0.5 part Accelerator B: 4 - 7 parts Silane coupling agent: 1 - 3 parts Solvent: 480 - 700 parts.

2. The transparent flame-retardant coating according to claim 1, characterized in that, the tackifying resin is any one or more of hydrogenated nitrile rubber, solid phenolic resin, polyketone resin, petroleum resin, rosin resin, terpene resin.

3. The transparent flame-retardant coating according to claim 1, characterized in that, the flame retardant is any one or more of aluminum diethylphosphinate, antimony trioxide, magnesium hydroxide, aluminum hydroxide, alkyl phosphate esters, dicyclopentadiene, borate, triazine and its derivatives, bromotrichloromethane.

4. The transparent flame-retardant coating according to claim 1, characterized in that, the accelerator A is an organic urea accelerator, and the accelerator B is a modified aromatic amine accelerator.

5. The transparent flame-retardant coating according to claim 1, characterized in that, the silane coupling agent is any one or more of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane.

6. The transparent flame-retardant coating according to claim 1, characterized in that, the solvent is methyl ethyl ketone or N,N-dimethylformamide (DMF).

7. Transparent flame-retardant hot-pressing film, characterized in that, it comprises a PET substrate and a transparent flame-retardant coating coated on one or both sides of the PET substrate, and the transparent flame-retardant coating is formed after curing of the transparent flame-retardant coating according to any one of claims 1 - 6.

8. The transparent flame-retardant hot-pressing film according to claim 7, characterized in that, the thickness of the PET substrate is 40 - 60 μm, and the thickness of the transparent flame-retardant coating is 20 - 30 μm.

9. Preparation method of the transparent flame-retardant hot-pressing film, characterized in that, it comprises the following steps: S1. Preparation of the transparent flame-retardant coating Prepare materials according to the weight parts of the raw materials for the transparent flame-retardant coating, and the raw materials are as follows: Tackifying resin: 50 - 80 parts, bisphenol A diglycidyl ether epoxy resin: 38 - 45 parts, DCPD phenol epoxy resin: 19 - 25 parts, bisphenol A type epoxy resin: 0 - 15 parts, flame retardant: 70 - 90 parts, 4,4'-diaminodiphenyl sulfone: 4 - 8 parts, dicyandiamide curing agent: 0.5 - 0.8 part, accelerator A: 0.1 - 0.5 part, accelerator B: 4 - 7 parts, silane coupling agent: 1 - 3 parts, solvent: 480 - 700 parts; Fully mix the tackifying resin, bisphenol A diglycidyl ether epoxy resin, DCPD phenol epoxy resin, bisphenol A type epoxy resin and part of the solvent to obtain solution A; Mix the flame retardant, silane coupling agent and part of the solvent to obtain mixture B; Fully mix solution A and mixture B to obtain mixture C; Fully mix 4,4'-diaminodiphenyl sulfone, accelerator A and part of the solvent to obtain solution D; Fully mix dicyandiamide curing agent, accelerator B and part of the solvent to obtain solution E; Fully mix mixture C, solution D and solution E to obtain a transparent flame retardant coating; S2. Prepare wet film and dry film Apply the transparent flame retardant coating onto the PET substrate; After the coating is completed, a wet film is obtained, and a protective film is attached; then bake to obtain a dry film; S3. Prepare hot-pressed film Hot-press the dry film to obtain a prefabricated flame retardant film; then carry out aging treatment to obtain a transparent flame retardant hot-pressed film.

10. Application of the transparent flame retardant hot-pressed film, which is characterized in that The transparent flame retardant hot-pressed film described in any one of claims 7-8 or the transparent flame retardant hot-pressed film prepared by the preparation method described in claim 9 is used for the lamination of electronic components, the lamination of metal parts, and the coating of lithium batteries and power batteries.

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