BOPET (Biaxially Oriented Polyethylene Terephthalate) release film with high residual heavy release force and preparation process of BOPET release film

Abstract

The invention relates to the technical field of release films, in particular to a BOPET release film with high residual heavy release force and a preparation process thereof.The BOPET release film comprises a base material and a composite release layer coating at least one surface of the base material, and the composite release layer is formed by high-temperature curing of a composite release agent; wherein the composite release agent is prepared from the following components in parts by weight: 14 to 28 parts of an organic silicon main agent, 6 to 30 parts of a high stripping regulator, 1.2 to 2.9 parts of a cross-linking agent, 0.8 to 3.2 parts of a catalyst, 0.04 to 0.12 part of a coupling agent and 0.3 to 1.2 parts of a flatting agent. The release film with high residual heavy release force and the preparation process thereof aim at solving the problem that the release force and the residual adhesion rate of the release film are difficult to meet the requirements at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of release films, and in particular to a BOPET release film with high residual release force and a preparation process thereof. Background Art

[0002] Release film refers to a film with separation properties due to its low surface energy. The film has no adhesion or slight stickiness after contacting with specific materials under limited conditions. Usually, the film substrate is treated with corona and pre-coating to increase the surface tension of the substrate, and then coated with silicon or fluorine to achieve the release effect.

[0003] Release films can be divided into light release films, medium release films and heavy release films according to the release force. Heavy release films are generally used in the field of die-cutting and transfer gluing, especially in the protection of the molten solid hot melt adhesive surface and the thermosetting adhesive surface, and the heavy release film surface is required to have a weak stickiness to ensure that the release film fits the product perfectly. At the same time, the release film is required to have a high release force, and the silicone oil coating surface is smooth and tidy, and the release force changes steadily over time and temperature. The wide range of use ensures that separation is easy and simple, and the adhesive layer will not be transferred and remain on the surface of the release film.

[0004] In order to improve the release force of the release film, the traditional method is to increase the amount of release force regulator or reduce the coating thickness on the conventional formula. The poor adjustment of the overall formula affects the molecular structure of the silicone oil surface of the release film, reduces the stability of the entire silicone oil surface, makes the silicone oil surface rough and uneven, and reduces the residual adhesion rate, causing the release layer to fall off and affecting customer use. Therefore, the existing technology needs to be improved and developed.

[0005] Therefore, the inventor provides a BOPET release film with high residual release force and a preparation process thereof. Summary of the invention

[0006] (1) Technical issues to be solved

[0007] The embodiment of the present invention provides a BOPET release film with high residual heavy release force and a preparation process thereof, which solves the technical problem that the release force and residual bonding rate of the release film are difficult to meet the requirements at the same time.

[0008] (2) Technical solution

[0009] The present invention provides a BOPET release film with high residual release force, comprising a substrate and a composite release layer coated on at least one surface of the substrate, wherein the composite release layer is formed by high-temperature curing of a composite release agent; wherein the composite release agent comprises, by weight: 14 to 28 parts of an organic silicon main agent, 6 to 30 parts of a high-peeling regulator, 1.2 to 2.9 parts of a cross-linking agent, 0.8 to 3.2 parts of a catalyst, 0.04 to 0.12 parts of a coupling agent, 0.3 to 1.2 parts of a leveling agent, and the rest is an aqueous solution. When the composite release agent is used, an aqueous solution (e.g., an aqueous solution) is added to make up to 100 parts by weight to prepare a solution for coating and use.

[0010] Furthermore, the organic silicon main agent is an emulsion type release agent, and its component is polydimethylvinylsiloxane.

[0011] Furthermore, the high-stripping regulator includes a modified vinyl MQ resin, a long-chain olefin diluent, a mixture inhibitor of acetylene alcohol oligomers and a low-viscosity vinyl polysiloxane; wherein the mass proportion of the vinyl MQ resin is 50-70%, the mass proportion of the long-chain olefin diluent is 3-10%, the mass proportion of the mixture inhibitor of acetylene alcohol oligomers is 5-10%, and the mass proportion of the low-viscosity vinyl polysiloxane is 10-20%; the long-chain olefin diluent is isobutylene, and the mixture inhibitor of acetylene alcohol oligomers includes 20-35% of allyl alcohol by mass, 25-55% of maleic acid by mass, and 10-25% of 2-hydroxypropanesulfonic acid by mass.

[0012] Furthermore, the leveling agent includes modified polydimethylsiloxane, polyether polyester modified organic siloxane, a surfactant, and a diluent; wherein the mass proportion of the polydimethylsiloxane is 30-55%, the mass proportion of the polyether polyester modified organic siloxane is 20-35%, the mass proportion of the surfactant is 10-25%, and the mass proportion of the diluent is 15-30%; the surfactant is acetylene glycol polyether, and the diluent is a mixture of small molecule siloxane, organic fat, aliphatic hydrocarbon and fluorine-containing hydrocarbon in a preset mass ratio.

[0013] Furthermore, the coating thickness of the composite release film is 0.11-0.2 mm.

[0014] Furthermore, the release force of the composite release film is 30 to 200 g / in.

[0015] Furthermore, the residual bonding rate of the composite release film is greater than 98%.

[0016] Furthermore, the content of organic silicon in the composite release film is 0.11 to 0.2 g / m 2 .

[0017] The present invention also provides a process for preparing a BOPET release film with high residual release force, comprising the following steps:

[0018] Extruding the polyester melt produced by the polyester synthesis step into a casting sheet, and longitudinally stretching the casting sheet;

[0019] Applying a composite release agent to the longitudinally stretched cast sheet to form a composite release layer on at least one side of the sheet;

[0020] Then, the film is subjected to transverse stretching, curing and shaping, and traction and winding treatments in sequence to obtain the release film with high residual peeling force.

[0021] Furthermore, the polyester melt produced by the polyester synthesis step is extruded into a casting sheet, and the casting sheet is longitudinally stretched, which specifically includes the following steps:

[0022] The polyester melt produced in the polyester synthesis process is transported to the twin-screw main extruder through a melt pipeline, and the film-grade PET chips, masterbatch and recycled chips are simultaneously fed into the twin-screw auxiliary extruder;

[0023] After being melted and plasticized by an extruder, the PET melt is uniformly extruded onto a casting roll through a die adapter in layers, and cooled on a low-temperature casting roll to form a thick sheet with a crystallinity of less than 3%;

[0024] The thick sheet is fed into a longitudinal stretching unit and longitudinally stretched by the speed ratio difference between the front and rear rollers.

[0025] (3) Beneficial effects

[0026] In summary, the present invention optimizes the components and ratios of the composite release film, so that the release force of the release film has a wide adjustable range, the aging release force is low, and the surface of the composite release layer is smooth and stable. In addition, its residual bonding rate is high and has little effect on the protective layer. At the same time, the biaxial stretching process is combined with the online coating process, which can fully utilize the characteristics of the large space size and high air supply and exhaust power of the transverse stretching oven, and the production speed is fast, so the production efficiency of the online production of heavy release film is much higher than the offline secondary coating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 It is a schematic flow chart of a process for preparing a BOPET release film with high residual release force provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0032] A BOPET release film with high residual weight release force provided by an embodiment of the present invention comprises a substrate and a composite release layer coated on at least one surface of the substrate, wherein the composite release layer is formed by high-temperature curing of a composite release agent; wherein the composite release agent comprises, in parts by weight: 14 to 28 parts of a silicone main agent, 6 to 30 parts of a high-stripping regulator, 1.2 to 2.9 parts of a cross-linking agent, 0.8 to 3.2 parts of a catalyst, 0.04 to 0.12 parts of a coupling agent, 0.3 to 1.2 parts of a leveling agent, and the rest being an aqueous solution.

[0033] In the above embodiment, the inventor found that the high release film coating sold in the market in the past had a low residual bonding rate and poor coating stability due to insufficient cross-linking. In addition, the high release film did not reach the optimal ratio in the past, and there was an incomplete reaction problem, which resulted in unstable peeling performance; the content of excess Si-H in the coating was high and it was not completely consumed during the curing process. When the oven aging pressure test was performed, the tape was in full contact with the release film, and due to the high temperature and high pressure, the internal Si-H would also contact the tape, resulting in a high aging release force. However, the various ratios of the present invention are appropriate, the reaction is complete, the content of excess Si-H in the coating is low, and after exploring the appropriate process conditions, the release film coating consumes most of the surface Si-H during the oven curing process, and only a small amount of Si-H inside the coating remains. The release force of the release film produced by the present invention is stable and does not need to be solved by reducing the excess Si-H through the aging process. Since the aging peeling force of the release film produced by the present invention is low, it can be applied to hot and cold paste processes, while the previous formula can only be applied to cold paste processes. The release force can be improved by adjusting the proportion of the regulator to increase the proportion of hydroxyl functional groups on the coating surface and thus increase the surface tension of the coating. The lower aging release force is achieved by adjusting the appropriate proportion of the formula to reduce the excess Si-H content in the coating.

[0034] Among them, the core layer of the substrate used in the release film is melt-directly melted. This process reduces the probability of contamination during the transportation of raw materials. In addition, the core layer has no secondary melting process, its viscosity decreases less, and the proportion of low-molecular organic matter is small. The heavy release film produced has strong thermal stability and lower cost.

[0035] Among them, the main silicone agent is an emulsion release agent. Specifically, the emulsion release agent of the 3K system can be used in conjunction with its emulsion crosslinking agent and catalyst. The formula can be flexibly adjusted, and the coating amount can be adjusted by directly adding water to dilute. In addition, the product has good shear resistance, curing and flexibility, which matches the film stretching process. Being able to complete release coating and film drawing simultaneously is a "high-yield" operation, which can not only reduce the differences in release film batches, avoid the impact of secondary heating on the flatness of PET film, but also help reduce costs.

[0036] Among them, the high stripping regulator includes a modified vinyl MQ resin, a long-chain olefin diluent, a mixture inhibitor of acetylene oligomers and a low-viscosity vinyl polysiloxane; the mass proportion of the vinyl MQ resin is 50-70%, the mass proportion of the long-chain olefin diluent is 3-10%, the mass proportion of the mixture inhibitor of acetylene oligomers is 5-10%, and the mass proportion of the low-viscosity vinyl polysiloxane is 10-20%; the long-chain olefin diluent is isobutylene, and the mixture inhibitor of acetylene oligomers includes 20-35% of allyl alcohol, 25-55% of maleic acid, and 10-25% of 2-hydroxypropanesulfonic acid. The regulator used contains hydroxyl and vinyl bifunctional groups at the end, and its application in the release agent plays a dual role. The hydroxyl group enhances the firmness of the combination with the substrate. At the same time, due to the introduction of the hydroxyl group, the surface tension of the coating is increased, and the vinyl participates in the silicon-hydrogen strengthening reaction, which enhances the compatibility with the release agent. Therefore, the release film coating obtained by the present invention is stable and has a high release force. Modified vinyl mq resin is used to improve the release force stability of the release agent after adding the heavy release force regulator, and maintain a high residual adhesion rate. As a diluent to dissolve the vinyl mq resin, the long-chain olefin diluent can react with the crosslinking agent (hydrogen polysiloxane) during the curing process of the release agent, and no emissions or pollution will be generated.

[0037] Among them, the leveling agent includes modified polydimethylsiloxane, polyether polyester modified organic siloxane, surfactant and diluent; the mass proportion of polydimethylsiloxane is 30-55%, the mass proportion of polyether polyester modified organic siloxane is 20-35%, the mass proportion of surfactant is 10-25%, and the mass proportion of diluent is 15-30%; the surfactant is acetylene glycol polyether, and the diluent is a mixture of small molecule siloxane, organic fat, aliphatic hydrocarbon and fluorine-containing hydrocarbon according to a preset mass ratio. Its main mechanism of action is to reduce the surface tension of the coating liquid, increase the fluidity and wettability of the coating, prevent oxidation and foam formation, improve the transparency and gloss of the coating, reduce defects such as shrinkage holes, and improve the appearance quality and production efficiency of the coating.

[0038] Specifically, the high stripping regulator used in the present invention comprises a mixture of a modified vinyl MQ resin, a long-chain olefin diluent, an acetylenic alcohol oligomer inhibitor and a low-viscosity vinyl polysiloxane, for example, EM97CN.

[0039] The crosslinking agent used in the present invention is a water-based emulsion of methyl hydrogen-containing polysiloxane, for example, CROSSLINKER V72.

[0040] The catalyst used in the present invention is a Pt catalyst, for example, CATALYST EM470.

[0041] The coupling agent used in the present invention is composed of amino-modified siloxane, for example, ADHESION PROMOTER HF86.

[0042] The leveling agent used in the present invention is a mixture of modified polydimethylsiloxane, polyether polyester modified organic siloxane, surfactant and diluent, for example, WT120.

[0043] Since the above-mentioned high-stripping regulator, cross-linking agent, catalyst, coupling agent and leveling agent are all existing finished products purchased from suppliers, their specific components and proportions are not described in detail.

[0044] The components in the composite release agent react completely without unreacted small molecules penetrating out, resulting in the appearance of greasy release surface of the release film. The above-mentioned BOPET heavy release film produced online, the solid content of the organic silicon in the composite release agent is 0.11-0.2 g / m 2 By adjusting the coating thickness and the content of the regulator, the release force can be stably adjusted in the range of 30 to 200 g / in and the residual bonding rate can be greater than 98%.

[0045] Figure 1 Schematic diagram of a process for preparing a BOPET release film with high residual release force provided by an embodiment of the present invention, see Figure 1 , the process may include the following steps:

[0046] S100, extruding the polyester melt produced by the polyester synthesis step into a casting sheet, and longitudinally stretching the casting sheet.

[0047] Specifically, step S100 includes the following steps:

[0048] S101, transporting the polyester melt produced in the polyester synthesis process to the twin-screw main extruder through a melt pipeline, and simultaneously feeding the film-grade PET chips, masterbatch and recycled chips into the twin-screw auxiliary extruder;

[0049] S102, after being melted and plasticized by an extruder, the PET melt is uniformly extruded onto a casting roll through a die adapter in layers, and cooled on a low-temperature casting roll to form a thick sheet with a crystallinity of less than 3%;

[0050] S103, feeding the thick sheet into the longitudinal stretching unit, and performing longitudinal stretching by the speed ratio difference between the front and rear rollers.

[0051] S200, coating the longitudinally stretched cast sheet with a composite release agent to form a composite release layer on at least one side of the sheet.

[0052] Specifically, after longitudinal stretching, the film enters a corona treatment unit to increase the surface energy of the film to more than 52 dynes, and then a composite release agent is coated on the corona-treated substrate by a coating machine.

[0053] S300, then sequentially performing transverse stretching, curing and shaping, and traction and winding processes to obtain a release film with high residual peeling force.

[0054] Specifically, the thick sheet coated with the composite release agent enters the transverse stretching unit for preheating, stretching, and shaping to form a release film with high residual peeling force; the release film with high residual peeling force is cooled, dusted by an online dust removal device, flattened and rolled by a traction system, and then cut and packaged into finished products.

[0055] The test methods involved in the following Examples 1 and 2 are as follows:

[0056] Release force test: Use TESA7475 tape and 31B tape to stick on the heavy release film to be tested in the longitudinal (mechanical) direction, and use a 2kg standard FINAT test roller to roll the sample back and forth twice to ensure that the tape and the sample are flat. The blank standard sample is stuck on the Teflon film in the above steps; cut the sample and the standard sample into 200mm×30mm strips, and each sample needs at least 5 strips; use two standard stainless steel strips to press the tested strips and the standard sample flat, with a load of 20g / cm 2 .

[0057] For the rapid release force test, the specimen is placed at room temperature for 20 minutes. After the specimen is taken out and the load is removed, a peeling force tester can be used to perform a peeling test at an angle of 180° and a speed of 30 cm / min. The unit is g / in.

[0058] For conventional release force test, the specimen is placed at room temperature for 20 hours, then taken out, the load is removed, and placed in a standard environment for 2 hours before the peeling test can be performed under the above conditions;

[0059] For the aging release force test, the specimens were placed in an oven at 70°C for 20 hours, and the remaining steps were the same as those for the conventional peeling force test.

[0060] Residual adhesion test: The sample strips and standard samples prepared in the above steps are pressed flat with a pressing block at the same time, placed in a 70°C oven for 20 hours, taken out, the load is removed, and placed in a standard environment for 2 hours; the 31B tape is peeled off from the sample strips, maintaining a uniform speed, and at the same time, it is attached to the non-corona surface of the blank PET film in the longitudinal direction, and the sample is rolled back and forth twice with a standard FINAT test roller to ensure that the tape and the sample are flat; then the standard sample is peeled off from the Teflon film, and a standard blank standard sample is made according to the above steps; after placing for 2 hours, a peeling force test is performed, and the residual adhesion rate is the ratio of the peeling force of the sample test to the peeling force of the blank standard test.

[0061] Example 1

[0062] A BOPET release film with a stable high residual release force and an online preparation process thereof, the specific steps are as follows:

[0063] Step 1. Prepare coating solution: weigh the silicone emulsion in a mixing barrel, dilute it with water at a mass ratio of 2:1, stir at 400 rpm / min, and add the diluted emulsion in turn. EM 97CN and CROSSLINKER V72, CATALYST EM 470, ADHESION PROMOTER HF86, WT120, then add aqueous solution, adjust the solid content of the coating liquid to 10%, continue stirring for 15 minutes, and let it stand for 15 minutes to obtain a composite release agent coating liquid. In the prepared composite release agent coating liquid, the mass percentage content of the silicone main agent is 15%, the mass percentage content of the high stripping regulator is 8%, the mass percentage content of the crosslinking agent is 1.4%, the mass percentage content of the catalyst is 1.2%, the mass percentage content of the coupling agent is 0.07%, and the mass percentage content of the leveling agent is 0.5%.

[0064] Among them, the solvent water and dilution water used in the liquid preparation process are both treated pure water, and the operating temperature is 15°C.

[0065] Step 2, preparing a stable BOPET release film with high residual weight release force produced online, the overall process flow is: resin melting → extrusion casting → longitudinal stretching → corona treatment → online coating → transverse stretching → online dust removal → traction and winding → slitting and packaging;

[0066] The specific process parameters include: the average thickness of the BOPET base film is 36μm; the temperature of the main / auxiliary extruder is 275℃; the temperature of the casting roll is 25±1℃; the longitudinal stretching temperature is 92℃, and the stretching ratio is 3.2; the corona machine voltage is 15±0.5kV, and the speed ratio is 0±0.1%; the micro-concave coating process is used to apply the above-mentioned coating liquid on the single side surface of the longitudinally stretched product, the coating speed ratio is 25%, the coating machine temperature is 20±1℃, the pressure of the pressure roll is 5±0.2MPa, and the coating wet glue amount is 3.12g / m 2 ; The transverse stretching temperature is 116°C, the setting temperature is 243°C, the stretching ratio is 3.8; the winding speed is 150m / min.

[0067] The stable high residual heavy release force release film finally produced online in this Example 1 consists of a BOPET base film and a silicone release coating located on a single side surface thereof; the average thickness of the BOPET base film is 36 μm, and the thickness limit deviation is 0.1 μm; the average thickness of the silicone release coating is 0.15 μm, and the thickness limit deviation is 0.02 μm; the stable high residual heavy release force release film produced online has a 20-min quick release force of 27.82 g / in, a 20-h conventional release force of 38.94 g / in, a 20-h aging release force of 51.75 g / in, and a residual adhesion rate of 99.17%.

[0068] Example 2

[0069] A BOPET release film with a stable high residual release force and an online preparation process thereof, the specific steps are as follows:

[0070] Step 1, prepare the coating liquid: weigh the silicone main agent emulsion in the mixing barrel, the composition of which is polydimethylvinylsiloxane, add water at a mass ratio of 2:1, start stirring at 400rpm / min, and add the diluted EM 97CN and CROSSLINKER V72, CATALYST EM 470, ADHESION PROMOTER HF86, WT120, then add aqueous solution, adjust the solid content of the coating liquid to 10%, continue stirring for 15 minutes, and let it stand for 15 minutes to obtain a composite release agent coating liquid. In the prepared composite release agent coating liquid, the mass percentage content of the silicone main agent is 15%, the mass percentage content of the high stripping regulator is 12%, the mass percentage content of the crosslinking agent is 1.7%, the mass percentage content of the catalyst is 1.5%, the mass percentage content of the coupling agent is 0.075%, and the mass percentage content of the leveling agent is 0.72%.

[0071] Among them, the solvent water and dilution water used in the liquid preparation process are both treated pure water, and the operating temperature is 15°C.

[0072] Step 2, preparing a stable BOPET release film with high residual weight release force produced online, the overall process flow is: resin melting → extrusion casting → longitudinal stretching → corona treatment → online coating → transverse stretching → online dust removal → traction and winding → slitting and packaging;

[0073] The specific process parameters include: the average thickness of the BOPET base film is 25μm; the temperature of the main / auxiliary extruder is 278℃; the temperature of the casting roll is 26±1℃; the longitudinal stretching temperature is 92.8℃, and the stretching ratio is 3.3; the corona machine voltage is 16±0.5kV, and the speed ratio is 0±0.1%; the micro-concave coating process is used to apply the above-mentioned coating liquid on the single side surface of the longitudinally stretched product, the coating speed ratio is 20%, the coating machine temperature is 20±1℃, the pressure of the pressure roll is 5±0.2MPa, and the coating wet glue amount is 2.9g / m 2 ; The transverse stretching temperature is 117°C, the setting temperature is 245°C, the stretching ratio is 3.82; the winding speed is 190m / min.

[0074] The stable high residual heavy release force release film finally produced online in this Example 2 is composed of a BOPET base film and a silicone release coating located on a single side surface thereof; the average thickness of the BOPET base film is 25 μm, and the thickness limit deviation is 0.12 μm; the average thickness of the silicone release coating is 0.15 μm, and the thickness limit deviation is 0.02 μm; the stable high residual heavy release force release film produced online has a 20-min quick release force of 35.4 g / in, a 20-h conventional release force of 60.9 g / in, a 20-h aging release force of 81.21 g / in, and a residual adhesion rate of 99.32%.

[0075] The following is a comparison of data of Examples 1 and 2 of the present invention with common products on the market (with specific formulas attached). See the table below for details.

[0076] Table 1 Performance comparison of various release films

[0077]

[0078] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known methods and technologies is omitted here.

[0079] The above are only embodiments of the present application and are not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A BOPET release film with high residual release force, characterized in that: It includes a substrate and a composite release layer coated on at least one surface of the substrate, wherein the composite release layer is formed by high-temperature curing of a composite release agent; wherein the composite release agent comprises, in parts by weight: 14 to 28 parts of a silicone main agent, 6 to 30 parts of a high-stripping regulator, 1.2 to 2.9 parts of a cross-linking agent, 0.8 to 3.2 parts of a catalyst, 0.04 to 0.12 parts of a coupling agent, and 0.3 to 1.2 parts of a leveling agent.

2. The BOPET release film with high residual release force according to claim 1, characterized in that: The organic silicon main agent is an emulsion type release agent, and its component is polydimethylvinylsiloxane.

3. The BOPET release film with high residual release force according to claim 1, characterized in that: The high-stripping regulator includes a modified vinyl MQ resin, a long-chain olefin diluent, a mixture inhibitor of acetylene alcohol oligomers and a low-viscosity vinyl polysiloxane; wherein the mass proportion of the vinyl MQ resin is 50-70%, the mass proportion of the long-chain olefin diluent is 3-10%, the mass proportion of the mixture inhibitor of acetylene alcohol oligomers is 5-10%, and the mass proportion of the low-viscosity vinyl polysiloxane is 10-20%; the long-chain olefin diluent is isobutylene, and the mixture inhibitor of acetylene alcohol oligomers includes 20-35% of allyl alcohol by mass, 25-55% of maleic acid by mass, and 10-25% of 2-hydroxypropanesulfonic acid by mass.

4. The BOPET release film with high residual release force according to claim 1, characterized in that: The leveling agent includes modified polydimethylsiloxane, polyether polyester modified organic siloxane, a surfactant, and a diluent; wherein the mass proportion of the polydimethylsiloxane is 30-55%, the mass proportion of the polyether polyester modified organic siloxane is 20-35%, the mass proportion of the surfactant is 10-25%, and the mass proportion of the diluent is 15-30%; the surfactant is acetylene glycol polyether, and the diluent is a mixture of small molecule siloxane, organic fat, aliphatic hydrocarbon and fluorine-containing hydrocarbon in a preset mass ratio.

5. The BOPET release film with high residual release force according to claim 1, characterized in that: The coating thickness of the composite release film is 0.11-0.2 mm.

6. The BOPET release film with high residual release force according to claim 1, characterized in that: The release force of the composite release film is 30 to 200 g / in.

7. The BOPET release film with high residual release force according to claim 1, characterized in that: The residual bonding rate of the composite release film is greater than 98%.

8. The BOPET release film with high residual release force according to claim 1, characterized in that: The content of organic silicon in the composite release film is 0.11-0.2 g / m 2 .

9. The process for preparing a BOPET release film with high residual release force according to any one of claims 1 to 8, characterized in that: The process includes the following steps: The polyester melt produced by the polyester synthesis process is extruded into a casting sheet, and the casting sheet is longitudinally stretched; wherein the longitudinal stretching temperature is 80 to 100° C., and the stretching ratio is 3.2 to 4.0; The composite release agent is applied to the longitudinally stretched cast sheet to form a composite release layer on at least one side of the sheet; wherein the amount of the coating liquid is 2 to 4 g / m 2 , the coating temperature is 20±1℃. Then, the film is subjected to transverse stretching, curing and shaping, and traction and winding treatments in sequence to obtain the release film with high residual peeling force; wherein, the transverse stretching temperature is 100 to 130° C., and the stretching ratio is 3.8 to 4.

5.

10. The method for preparing a BOPET release film with high residual release force according to claim 9, characterized in that: The method of extruding the polyester melt produced by the polyester synthesis step into a casting sheet and longitudinally stretching the casting sheet specifically comprises the following steps: The polyester melt produced in the polyester synthesis process is transported to the twin-screw main extruder through a melt pipeline, and the film-grade PET chips, masterbatch and recycled chips are simultaneously fed into the twin-screw auxiliary extruder; wherein the temperature of the twin-screw main extruder and the twin-screw main extruder is 260-280°C; After being melted and plasticized by an extruder, the PET melt is uniformly extruded onto a casting roll through a die adapter in layers, and cooled on a low-temperature casting roll to form a thick sheet with a crystallinity of less than 3%; The thick sheet is fed into a longitudinal stretching unit and longitudinally stretched by the speed ratio difference between the front and rear rollers.

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