High modulus and high transparency bopet coated base film and preparation method thereof

Abstract

The application discloses a kind of high modulus high transparency BOPET coating base film, by upper surface layer, lower surface layer and core layer constitute, it is characterized in that, the core layer is support layer, raw material contains 5.0~10.0% high modulus master batch by weight percentage, and the balance is super bright light polyester chip;The upper surface layer and lower surface layer are anti-adhesion layer, and the raw material contains 3.0~5.0% anti-adhesion master batch by weight percentage, and the balance is super bright light polyester chip.The application also discloses the preparation method of the above-mentioned high modulus high transparency BOPET coating base film.The BOPET coating base film prepared by the application has stable performance, flat film surface, high modulus, high transparency, low surface roughness, good coating property, good temperature resistance, and can be used in downstream precision coating field.

Description

Technical Field

[0001] The present invention relates to the technical field of BOPET films, in particular to a high-modulus and high-transparency BOPET coating base film and a preparation method thereof. Background Art

[0002] BOPET film is a packaging film with comprehensive performance. It offers excellent transparency, gloss, airtightness, and aroma retention. BOPET film also boasts excellent mechanical properties, with the strongest toughness of all thermoplastics, and significantly higher tensile and impact strength than conventional films. It also offers excellent strength and dimensional stability, making it suitable for secondary processing such as printing and paper bags. BOPET film also exhibits excellent heat and cold resistance, as well as good chemical and oil resistance.

[0003] In recent years, China's BOPET film industry has experienced rapid growth, particularly in the development and expansion of BOPET coated functional films. These high-value-added products are widely used in electronics, optoelectronics, and other fields. However, the haze of conventional BOPET film is generally above 1.5%, resulting in poor transparency. Furthermore, the film needs to be dried in a high-temperature oven after coating, and its low modulus leads to wrinkling when rolled up after exiting the oven, making it unsuitable for high-end BOPET coating applications. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a high-modulus and high-transparency BOPET coating base film and a preparation method thereof. The prepared film has stable performance, a smooth film surface, high transparency, a high elastic modulus and good temperature resistance.

[0005] The present invention provides a high-modulus, high-transparency BOPET coating base film, which is composed of an upper surface layer, a lower surface layer, and a core layer. The core layer is a support layer, and its raw material contains 5.0-10.0% by weight of a high-modulus masterbatch, with the balance being super-bright polyester chips. The upper and lower surface layers are anti-sticking layers, and their raw material contains 3.0-5.0% by weight of an anti-sticking masterbatch, with the balance being super-bright polyester chips. The raw material components of the upper and lower surface layers can be the same or different.

[0006] The active ingredient of the anti-sticking masterbatch is spherical barium sulfate particles; the average particle size of the spherical barium sulfate particles is 1.5 to 2.0 μm; the refractive index of the spherical barium sulfate particles is 1.56 to 1.58;

[0007] The raw materials of the high modulus masterbatch contain 1.0-2.0% talc powder, 0.5-1.0% potassium carboxylate, 0.5-1.0% liquid crystal polymer, 0.1-0.5% antioxidant, and the balance is super bright polyester chips.

[0008] Preferably, the particle size of the talc powder is 50 to 200 nm.

[0009] Preferably, the carboxylate potassium salt is at least one of potassium cyclopentyl oleate, potassium piperazine-1,4-dithiocarboxylate, and potassium 2,2-dimethyl-1,3-dioxolane-4-carboxylate.

[0010] Preferably, the liquid crystal polymer is DuPont LCP 6130LWT010 from the United States.

[0011] Preferably, the antioxidant is a hindered phenol antioxidant, a phosphite antioxidant or a combination thereof.

[0012] Preferably, the content of spherical barium sulfate particles in the anti-sticking masterbatch is 8000-10000 ppm.

[0013] Preferably, the viscosity of the super bright polyester chips is 0.66 to 0.68 dl / g, the b value is 0.8 to 1.0, and the L value is 80 to 82. The b value and the L value are tested according to the method 5.5.1 of GB / T 14190-2017.

[0014] Preferably, the thickness of the upper and lower surface layers each accounts for 13-15% of the total thickness of the film. The thicknesses of the upper and lower surface layers can be the same or different.

[0015] A method for preparing the high modulus and high transparency BOPET coating base film comprises the following steps:

[0016] S1, respectively adding the raw materials of the upper surface layer and the lower surface layer into two different extruders, and melt-extruding to form the upper surface layer melt and the lower surface layer melt; adding the raw materials of the core layer into the extruder, and melt-extruding to form the core layer melt; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in an extruder with a three-layer structure die to obtain a membrane sheet;

[0017] S2, cooling the film through a cold roller to obtain a cast sheet;

[0018] S3, longitudinally stretching the cast sheet; the specific steps of longitudinal stretching include: primary preheating, primary stretching, primary cooling, secondary preheating, secondary stretching, and secondary cooling;

[0019] S4. The longitudinally stretched film is transversely stretched to obtain a high modulus and high transparency BOPET coating base film, wherein the specific steps of transverse stretching sequentially include: preheating, stretching, shaping, and cooling.

[0020] In S1, the extrusion temperatures of the raw materials for the upper surface layer and the lower surface layer may be the same or different.

[0021] Preferably, in S3, the primary and secondary preheating temperatures for longitudinal stretching are 50-85°C, the primary and secondary stretching temperatures are 75-80°C, the primary stretching ratio is 1.5-1.8 times, the secondary stretching ratio is 2.0-2.2 times, the primary stretching gap is 78-80 mm, and the secondary stretching gap is 280-300 mm. The primary and secondary preheating temperatures may be the same or different, and the primary and secondary stretching temperatures may be the same or different.

[0022] Preferably, in S4, the preheating temperature for transverse stretching is 85-95°C, the stretching temperature is 100-115°C, the setting temperature is 190-225°C, and the stretching ratio is 3.8-4.2.

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention proposes a high-modulus, high-transparency BOPET coating base film. The super-bright polyester chips in the upper and lower surface layers have high transparency and excellent optical properties. The active ingredient of the anti-sticking masterbatch is spherical barium sulfate anti-stick particles with a particle size of 1.5 to 2.0 μm. These particles have a high affinity with the polyester chips and are not easily detached from the film surface. Their refractive index is similar to that of the polyester chips (1.57 at 25°C), which does not affect the film's optical properties. While effectively reducing haze, they ensure normal winding and unwinding while also reducing film surface roughness. The high-modulus masterbatch in the core layer and the talc and potassium carboxylate active ingredients complement each other, acting as nucleating agents to improve nucleation density, crystallization rate, grain size, and distribution uniformity. The liquid crystal polymer can form a network structure in the film, increasing its strength and modulus, ultimately effectively raising the film's elastic modulus to above 5500 MPa, preventing wrinkling during film winding after exiting the oven during the coating process. The BOPET coating base film prepared by the present invention has stable performance, a smooth film surface, high transparency, low surface roughness, good coating properties, and a high elastic modulus, and can be used in downstream precision coating fields. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below through specific embodiments.

[0026] Example 1

[0027] A high-modulus, high-transparency BOPET coating base film, comprising an upper surface layer, a lower surface layer, and a core layer. The core layer is a support layer, and its raw material, by weight percentage, contains 5.0% high-modulus masterbatch, and the balance is super-bright polyester chips. The upper and lower surface layers are anti-sticking layers, and their raw materials, by weight percentage, contain 3.0% anti-sticking masterbatch, and the balance is super-bright polyester chips.

[0028] The effective component of the anti-sticking masterbatch is spherical barium sulfate particles, the average particle size of the spherical barium sulfate particles is 1.5 μm, the refractive index is 1.56, and the content of the spherical barium sulfate particles in the anti-sticking masterbatch is 9000 ppm;

[0029] The raw material of the high modulus masterbatch contains 1.0% talc, 0.5% potassium carboxylate, 0.5% liquid crystal polymer, 0.1% antioxidant, and the rest is super bright polyester chip.

[0030] The particle size of the talc is 50 nm, the potassium carboxylate is ring carboxypropyl potassium oleate, the antioxidant is hindered phenol antioxidant, and the liquid crystal polymer is American DuPont LCP 6130LWT010. The viscosity of the super bright polyester chip is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0031] The thickness of the upper surface layer accounts for 15% of the total thickness of the film, and the thickness of the lower surface layer accounts for 15% of the total thickness of the film.

[0032] A preparation method of the high modulus and high transparency BOPET coated base film comprises the following steps:

[0033] S1, respectively, the raw materials of the upper surface layer and the lower surface layer are added to two different extruders to form upper surface layer melt and lower surface layer melt, the extrusion temperature of the raw materials of the upper surface layer and the lower surface layer is 260-280 ℃; the raw material of the core layer is added to the extruder to form the core layer melt, the extrusion temperature of the raw material of the core layer is 255-275 ℃; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in the extruder of the three-layer structure die to obtain a film piece, and the combined extrusion temperature is 275 ℃;

[0034] S2, the film piece is cooled by a cold roller at a cooling temperature of 30 ℃ to obtain a cast piece;

[0035] S3, the cast piece is longitudinally stretched; the specific steps of longitudinal stretching include, in sequence, first preheating at 85-95 ℃, first stretching at 75 ℃, a stretching ratio of 1.5 times, first cooling, second preheating at 85-95 ℃, second stretching at 75 ℃, a stretching ratio of 2.0 times, and second cooling; the first stretching gap is 78 mm, the second stretching gap is 280 mm, and the first cooling and the second cooling are at a temperature of 25 ℃;

[0036] S4, the film after longitudinal stretching is transversely stretched to obtain the high modulus and high transparency BOPET coated base film, and the specific steps of transverse stretching include, in sequence, preheating, stretching, setting, and cooling, wherein the preheating temperature is 85-95 ℃, the stretching temperature is 100-115 ℃, the setting temperature is 190-225 ℃, the cooling temperature is 25 ℃, and the transverse stretching ratio is 3.8.

[0037] Embodiment 2

[0038] A high modulus and high transparency BOPET coated base film is composed of an upper surface layer, a lower surface layer and a core layer, the core layer is a support layer, the raw material contains 7.0% of high modulus master batch and the rest is super bright polyester chip by weight percentage; the upper surface layer and the lower surface layer are anti-adhesion layers, the raw material contains 4.0% of anti-adhesion master batch and the rest is super bright polyester chip by weight percentage;

[0039] The effective component of the anti-adhesion master batch is spherical barium sulfate particles, the average particle size of the spherical barium sulfate particles is 1.8 μm, the refractive index is 1.57, and the content of the spherical barium sulfate particles in the anti-adhesion master batch is 9000 ppm;

[0040] The raw material of the high modulus master batch contains 1.5% of talc powder, 0.7% of potassium carboxylate, 0.7% of liquid crystal polymer, 0.3% of antioxidant, and the rest is super bright polyester chip by weight percentage.

[0041] The particle size of the talc powder is 100 nm, the potassium carboxylate is piperazine-1,4-bis potassium dithiocarboxylate, the antioxidant is hindered phenolic antioxidant, and the liquid crystal polymer is American DuPont LCP 6130LWT010. The viscosity of the super bright polyester chip is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0042] The thickness of the upper surface layer accounts for 14% of the total thickness of the film, and the thickness of the lower surface layer accounts for 14% of the total thickness of the film.

[0043] A preparation method of the high modulus and high transparency BOPET coated base film, comprising the following steps:

[0044] S1, respectively, the raw materials of the upper surface layer and the lower surface layer are added to two different extruders, and the upper surface layer melt and the lower surface layer melt are prepared by melt extrusion, the extrusion temperature of the raw materials of the upper surface layer and the lower surface layer is 260-280℃; the raw material of the core layer is added to the extruder, and the core layer melt is prepared by melt extrusion, the extrusion temperature of the raw material of the core layer is 255-275℃; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in the extruder of the three-layer structure die to obtain a film piece, and the combined and extruded temperature is 275℃;

[0045] S2, the film piece is cooled by a cold roller, and the cooling temperature is 30℃, to obtain a cast piece;

[0046] S3, longitudinally stretching the cast sheet; the specific steps of longitudinal stretching sequentially include: preheating at 85-95°C, stretching at 78°C with a stretching ratio of 1.6 times, cooling, preheating at 85-95°C for a second time, stretching at 78°C with a stretching ratio of 2.1 times, and cooling; wherein the stretching gap of the first stretching is 79 mm, and the stretching gap of the second stretching is 290 mm; the temperature of the first cooling and the second cooling is 25°C;

[0047] S4. The longitudinally stretched film is transversely stretched to obtain a high modulus and high transparency BOPET coated base film. The specific steps of transverse stretching include: preheating, stretching, shaping, and cooling. The preheating temperature is 85-95°C, the stretching temperature is 100-115°C, the shaping temperature is 190-225°C, the cooling temperature is 25°C, and the stretching ratio is 4.0.

[0048] Example 3

[0049] A high-modulus, high-transparency BOPET coating base film, comprising an upper surface layer, a lower surface layer, and a core layer. The core layer is a support layer, and its raw material, by weight percentage, contains 10.0% high-modulus masterbatch, and the balance is super-bright polyester chips. The upper and lower surface layers are anti-sticking layers, and their raw material, by weight percentage, contains 5.0% anti-sticking masterbatch, and the balance is super-bright polyester chips.

[0050] The active ingredient of the anti-sticking masterbatch is spherical barium sulfate particles, the average particle size of the spherical barium sulfate particles is 2 μm, the refractive index is 1.58, and the content of the spherical barium sulfate particles in the anti-sticking masterbatch is 9000 ppm;

[0051] The raw materials of the high modulus masterbatch contain 2.0% talc powder, 1.0% potassium carboxylate, 1.0% liquid crystal polymer, 0.5% antioxidant, and the balance is super bright polyester chips.

[0052] The talc has a particle size of 200 nm, the potassium carboxylate is potassium 2,2-dimethyl-1,3-dioxolane-4-carboxylate, the antioxidant is a phosphite antioxidant, and the liquid crystal polymer is DuPont LCP 6130LWT010. The viscosity of the super-bright polyester chips is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0053] The thickness of the upper surface layer accounts for 13% of the total thickness of the film, and the thickness of the lower surface layer accounts for 13% of the total thickness of the film.

[0054] A method for preparing the high modulus and high transparency BOPET coating base film comprises the following steps:

[0055] S1. The raw materials of the upper surface layer and the lower surface layer are respectively added to two different extruders, and the upper surface layer melt and the lower surface layer melt are formed by melt extrusion. The temperature of the extrusion of the raw materials of the upper surface layer and the lower surface layer is 260-280°C; the raw materials of the core layer are added to the extruder, and the core layer melt is formed by melt extrusion. The temperature of the extrusion of the raw materials of the core layer is 255-275°C; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in an extruder with a three-layer structure die to obtain a film. The temperature of the combined extrusion is 275°C;

[0056] S2, cooling the film through a cold roller at a temperature of 30° C. to obtain a cast sheet;

[0057] S3, longitudinally stretching the cast sheet; the specific steps of longitudinal stretching sequentially include: preheating at 85-95°C, stretching at 78°C with a stretching ratio of 1.6 times, cooling, preheating at 85-95°C for a second time, stretching at 78°C with a stretching ratio of 2.1 times, and cooling; wherein the stretching gap of the first stretching is 80 mm, and the stretching gap of the second stretching is 300 mm; the temperature of the first cooling and the second cooling is 25°C;

[0058] S4. The longitudinally stretched film is transversely stretched to obtain a high modulus and high transparency BOPET coated base film. The specific steps of transverse stretching include: preheating, stretching, shaping, and cooling. The preheating temperature is 85-95°C, the stretching temperature is 100-115°C, the shaping temperature is 190-225°C, the cooling temperature is 25°C, and the stretching ratio is 4.2.

[0059] Comparative Example 1

[0060] The only difference between Comparative Example 1 and Example 1 is that the components of the high modulus masterbatch are different. The raw materials of the high modulus masterbatch of Comparative Example 1 contain 0.5% potassium carboxylate, 0.5% liquid crystal polymer, 0.1% antioxidant, and the balance is super bright polyester chips.

[0061] The carboxylic acid potassium salt is potassium cyclopentyl oleate, the antioxidant is a hindered phenol antioxidant, and the liquid crystal polymer is DuPont LCP6130LWT010. The viscosity of the super bright polyester chips is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0062] Comparative Example 2

[0063] The only difference between Comparative Example 2 and Example 1 is that the components of the high-modulus masterbatch are different. The raw materials of the high-modulus masterbatch of Comparative Example 2 contain 1.0% talc powder, 0.5% liquid crystal polymer, 0.1% antioxidant, and the remainder is super bright polyester chips, by weight percentage.

[0064] The particle size of the talc powder is 50 nm, the antioxidant is a hindered phenol antioxidant, and the liquid crystal polymer is DuPont LCP6130LWT010. The viscosity of the super bright polyester chips is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0065] Comparative Example 3

[0066] The only difference between Comparative Example 3 and Example 1 is that the components of the high modulus masterbatch are different. The raw materials of the high modulus masterbatch of Comparative Example 3 contain 1.0% talc powder, 0.5% potassium carboxylate, 0.1% antioxidant, and the balance is super bright polyester chips.

[0067] The particle size of the talc powder is 50 nm, the potassium carboxylate is potassium cyclopropyl oleate, and the antioxidant is a hindered phenol antioxidant. The viscosity of the super bright polyester chips is 0.66-0.68 dl / g, the b value is 0.8-1.0, and the L value is 80-82.

[0068] Comparative Example 4

[0069] The only difference between Comparative Example 4 and Example 1 is that the components of the anti-sticking masterbatch are different. The effective ingredient of the anti-sticking masterbatch of Comparative Example 4 is irregular silica particles, the average particle size of the irregular silica particles is 3 μm, and the effective content of the irregular silica particles is 9000 ppmm.

[0070] Comparative Example 5

[0071] The only difference between Comparative Example 5 and Example 1 is that in the preparation method of the base film, the longitudinal stretching process of S3 is different. The details are as follows:

[0072] A BOPET coating base film, comprising an upper surface layer, a lower surface layer, and a core layer. The core layer is a support layer, and its raw material, by weight percentage, contains 5.0% high-modulus masterbatch, and the balance is super-bright polyester chips. The upper and lower surface layers are anti-sticking layers, and their raw material, by weight percentage, contains 3.0% anti-sticking masterbatch, and the balance is super-bright polyester chips.

[0073] The active ingredient of the anti-sticking masterbatch is spherical barium sulfate particles, the average particle size of the spherical barium sulfate particles is 1.5 μm, the refractive index is 1.56, and the content of the spherical barium sulfate particles in the anti-sticking masterbatch is 9000 ppm;

[0074] The raw materials of the high modulus masterbatch contain, by weight percentage, 1.0% talc powder, 0.5% potassium carboxylate, 0.5% liquid crystal polymer, 0.1% antioxidant, and the balance is super bright polyester chips.

[0075] The particle size of the talc is 50 nm, the potassium carboxylate salt is potassium cyclohexyl carboxylate, the antioxidant is a hindered phenol antioxidant, and the liquid crystal polymer is DuPont LCP 6130LWT010.

[0076] The thickness of the upper surface layer accounts for 15% of the total thickness of the film, and the thickness of the lower surface layer accounts for 15% of the total thickness of the film.

[0077] A preparation method of the high-modulus and high-transparency BOPET coated base film includes the following steps:

[0078] S1, respectively, the raw materials of the upper surface layer and the lower surface layer are added to two different extruders to form upper surface layer melt and lower surface layer melt through melt extrusion, the extrusion temperature of the raw materials of the upper surface layer and the lower surface layer is 260-280℃; the raw materials of the core layer are added to the extruder to form the core layer melt through melt extrusion, the extrusion temperature of the raw materials of the core layer is 255-275℃; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in the extruder of the three-layer structure die to obtain a film piece, the combined extrusion temperature is 275℃;

[0079] S2, the film piece is cooled by a cold roller, and the cooling temperature is 30℃, to obtain a cast piece;

[0080] S3, the cast piece is longitudinally stretched; the specific steps of longitudinal stretching include, in sequence, preheating at 90℃, stretching at 105℃, the stretching ratio is 3.8 times, and cooling at 25℃; wherein the stretching gap is 300mm;

[0081] S4, the film after longitudinal stretching is transversely stretched to obtain the high-modulus and high-transparency BOPET coated base film, the specific steps of transverse stretching include, in sequence, preheating, stretching, setting, and cooling, wherein the preheating temperature is 85-95℃, the stretching temperature is 100-115℃, the setting temperature is 190-225℃, the cooling temperature is 25℃, and the transverse stretching ratio is 3.8.

[0082] Test example

[0083] The base film samples prepared in Examples 1-3 and Comparative Examples 1-5 are subjected to comparative tests, and the test results are shown in Tables 1 and 2:

[0084] Table 1 Main physical property indexes of Examples 1-3

[0085]

[0086] Table 2 Main physical property indexes of Comparative Examples 1-5

[0087]

[0088]

[0089] From the comparison of the data in Table 1 and Table 2, it can be seen that the present invention uses an anti-sticking masterbatch whose active ingredient is spherical barium sulfate anti-sticking particles, which improves the optical properties of the film and reduces the surface roughness. In addition, the addition of a high-modulus masterbatch to the core layer, combined with the adjustment of the longitudinal stretching process, effectively improves the elastic modulus of the film, improves the temperature resistance of the film and the downstream coating processability, etc.

[0090] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A high modulus and high transparency BOPET coating base film, consisting of an upper surface layer, a lower surface layer and a core layer, characterized in that: The core layer is a support layer, and its raw material, by weight percentage, contains 5.0-10.0% of high-modulus masterbatch, and the balance is super-bright polyester chips; the upper surface layer and the lower surface layer are anti-sticking layers, and their raw material, by weight percentage, contains 3.0-5.0% of anti-sticking masterbatch, and the balance is super-bright polyester chips; The active ingredient of the anti-sticking masterbatch is spherical barium sulfate particles; the average particle size of the spherical barium sulfate particles is 1.5 to 2.0 μm; the refractive index of the spherical barium sulfate particles is 1.56 to 1.58; The raw materials of the high modulus masterbatch contain, by weight percentage, 1.0-2.0% talc, 0.5-1.0% potassium carboxylate, 0.5-1.0% liquid crystal polymer, 0.1-0.5% antioxidant, and the balance is super bright polyester chips; The method for preparing the high modulus and high transparency BOPET coating base film comprises the following steps: S1, respectively adding the raw materials of the upper surface layer and the lower surface layer into two different extruders, and melt-extruding to form the upper surface layer melt and the lower surface layer melt; adding the raw materials of the core layer into the extruder, and melt-extruding to form the core layer melt; the upper surface layer melt, the core layer melt and the lower surface layer melt are combined and extruded in an extruder with a three-layer structure die to obtain a membrane sheet; S2, cooling the film through a cold roller to obtain a cast sheet; S3, longitudinally stretching the cast sheet; the specific steps of the longitudinal stretching sequentially include: primary preheating, primary stretching, primary cooling, secondary preheating, secondary stretching, and secondary cooling; the temperature of the primary preheating and secondary preheating of the longitudinal stretching is 50-85°C, the temperature of the primary stretching and secondary stretching is 75-80°C, the ratio of the primary stretching is 1.5-1.8 times, the ratio of the secondary stretching is 2.0-2.2 times, the stretching gap of the primary stretching is 78-80 mm, and the stretching gap of the secondary stretching is 280-300 mm; S4. The longitudinally stretched film is subjected to transverse stretching to obtain a high modulus and high transparency BOPET coating base film, wherein the specific steps of the transverse stretching sequentially include: preheating, stretching, shaping, and cooling.

2. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The particle size of the talc powder is 50 to 200 nm.

3. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The carboxylate potassium salt is at least one of potassium cyclocarboxypropyl oleate, potassium piperazine-1,4-dithiocarboxylate, and potassium 2,2-dimethyl-1,3-dioxolane-4-carboxylate.

4. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The liquid crystal polymer is American DuPont LCP 6130LWT010.

5. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The content of the spherical barium sulfate particles in the anti-sticking masterbatch is 8000-10000 ppm.

6. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The ultra-bright polyester chips have a viscosity of 0.66-0.68 dl / g, a B value of 0.8-1.0, and an L value of 80-82.

7. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: The thickness of the upper and lower surface layers each accounts for 13-15% of the total thickness of the film.

8. The high modulus and high transparency BOPET coating base film according to claim 1, characterized in that: In S4, the preheating temperature for transverse stretching is 85-95°C, the stretching temperature is 100-115°C, the setting temperature is 190-225°C, and the stretching ratio is 3.8-4.2.

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