Pet release film base film having low surface roughness and preparation method therefor

Abstract

Disclosed in the present invention are a PET release film base film having low surface roughness and a preparation method therefor. The release film base film comprises three layers which are stacked: a core layer and two surface layers located on both sides of the core layer. The release film base film is obtained via three-layer co-extrusion by means of taking an auxiliary extrusion resin as a raw material of the two surface layers and a primary extrusion resin as a raw material of the core layer; the auxiliary extrusion resin is obtained by mixing an anti-blocking agent PET masterbatch and a PET base material in a mass ratio of 1:5-1:15; and the primary extrusion resin is a pure PET base material. The release film base film of the present invention has low surface roughness, low haze and excellent overall performance. Since large-particle benzoic acid-modified nano aluminum oxide has the refractive index very close to that of PET base films, the present invention can effectively avoid adverse visual impacts caused by a difference in the refractive index at interfaces between nanoparticles having large particle diameters and resin matrixes, thus effectively reducing the haze.

Description

Low surface roughness PET release film base film and preparation method thereof Technical Field

[0001] The present invention relates to the field of release materials, in particular to a PET release film base film with low surface roughness and a preparation method thereof. Background Art

[0002] [Corrected 10.01.2025 in accordance with Regulation 26] MLCCs (Multilayer Ceramic Capacitors), one of the most widely used basic electronic components, are widely used in consumer electronics. The Chinese MLCC market is growing faster than the global market, reaching a compound annual growth rate of 21% from 2016 to 2020, and the domestic market continues to expand. The MLCC production process consumes a large amount of MLCC release film. The area of ​​release film used to produce a single layer of MLCC is roughly equal to the area of ​​the MLCC itself. The global market for MLCC release film is approximately 20 billion RMB. Release film is primarily used in the casting process of MLCC production. An organic release agent is applied to a PET polyester film to achieve a release effect. MLCCs typically require 300-1000 layers of ceramic dielectric, and each layer requires the same release film. Therefore, the film must possess excellent peelability and smoothness to ensure that it can be peeled without damaging the dielectric layer. MLCC release films typically have certain thickness requirements, requiring a moderate and uniform film thickness to ensure easy peeling after release agent application. Currently, the MLCC release film market is still dominated by Japanese companies and reliant on imports. Japanese companies hold a high overall market share of 56%, while Chinese MLCC manufacturers account for approximately 6% of the global market. With the rapid growth of 5G smart terminals and base stations and the widespread adoption of new energy vehicles, the domestic production of MLCC release films is imperative.

[0003] Polyethylene terephthalate is one of the most important synthetic plastics today. It is widely used in the fields of fiber, packaging, and engineering plastics and has excellent physical and chemical properties. The basic performance and application of PET film can be changed within a certain range by regulating the crystallinity of the polymer. At present, the base film of MLCC release film mainly uses inorganic fillers with smaller particle size as an opening agent to prepare a polyester surface structure with less surface roughness and higher flatness. However, the selection of the opening agent and the method of adding the opening agent have a significant impact on the surface roughness of the MLCC release film base film. Similarly, the processing technology of the PET base film has guiding significance for improving the overall application performance of MLCC release film products.

[0004] The patent "A release film for stacking ceramic green sheets and its manufacturing equipment" (CN 215903925 U) describes a method for preparing a PET release film. The method primarily involves the following steps: Online coating is performed on both sides of the release film base film to form a coating, thereby imparting excellent roughness to both sides of the polyester base film, facilitating the subsequent production of MLCC release film. However, this process requires the configuration of online pre-coating equipment on the PET production line, as well as the coating liquid itself, which carries a certain cost. Furthermore, the coating surface is easily scratched, making it more expensive than polyester base film.

[0005] Patent CN 116120617 A discloses an MLCC release film and its preparation method. The patent mentions a PET film preparation method that primarily involves applying a silicone elastomer coating and a silica sol coating to both sides of a polyester base film to reduce the surface roughness of the MLCC release film. This process also requires either an online or offline coating process, resulting in higher costs compared to polyester-based films.

[0006] Patent CN 113635643 A discloses a polyester film and its preparation method, including a method for preparing an MLCC release film. The method comprises the following steps: A PET film is prepared using an ABC three-layer structure, wherein organic and inorganic functional masterbatches are added to the outer layers A and C to improve the film's surface roughness. Soft particles such as polyethyl acrylate, polymethyl acrylate, polymethyl methacrylate, or nylon are added in this process. When organic polymers are added as fillers to a PET melt, the soft particles generally have poor heat resistance and may carbonize during melting, leading to an increased likelihood of defects. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a PET release film base film with low surface roughness and a preparation method thereof in view of the deficiencies in the above-mentioned prior art.

[0008] To solve the above technical problems, the present invention adopts a technical solution: a low surface roughness PET release film base film, the release film base film comprising three stacked layers: a core layer and two surface layers located on both sides of the core layer, the release film base film being obtained by three-layer co-extrusion using a secondary extrusion resin as the raw material for the two surface layers and a primary extrusion resin as the raw material for the core layer;

[0009] The auxiliary extrusion resin is obtained by mixing the opening agent PET masterbatch and the PET base material in a mass ratio of 1:5 to 1:15, and the main extrusion resin is a pure PET base material.

[0010] Preferably, the raw materials for preparing the opener PET masterbatch include the following components by weight: 30-120 parts of ethylene glycol, 19-79 parts of terephthalic acid monomer, 0.1-0.4 parts of antimony trioxide, 0.1-0.4 parts of nano-silicon dioxide, and 0.05-0.2 parts of modified nano-alumina.

[0011] Preferably, the raw materials for preparing the opener PET masterbatch include the following components by weight: 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silicon dioxide, and 0.1 parts of modified nano-alumina.

[0012] Preferably, the particle size of the nano-silicon dioxide is 40 nm to 200 nm, and the particle size of the modified nano-alumina is 500 nm to 2 μm.

[0013] Preferably, the modified nano-alumina is prepared by the following method: reflux alumina nanoparticles and benzoic acid in a mass ratio of 3:1 in a toluene solvent at 90° C. for 12 h, washing with ethanol and drying at 80° C. to obtain the modified nano-alumina.

[0014] Preferably, the PET masterbatch of the opening agent is prepared by the following method:

[0015] 30-120 parts by weight of ethylene glycol, 19-79 parts of terephthalic acid monomer, 0.1-0.4 parts of antimony trioxide, 0.1-0.4 parts of nano-silicon dioxide, and 0.05-0.2 parts of modified nano-alumina are added to a reactor, and an esterification reaction is carried out at 230-260° C. and 150-180 kPa for 1.5-5 hours, followed by a polycondensation reaction at 260-280° C. and 0.4-0.6 kPa for 1.5-6 hours. The obtained polyester resin is cooled in water and then cut. After water droplets are removed by a vibrating screener, the resin is put into a dryer and dried in a nitrogen atmosphere at 120-160° C. for 6-24 hours to obtain the anti-blocking agent PET masterbatch.

[0016] Preferably, the PET masterbatch of the opening agent is prepared by the following method:

[0017] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina are added to a reactor, and an esterification reaction is carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction is carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin is cooled in water and then cut. After removing water droplets with a vibrating screen, it is put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain the opener PET masterbatch.

[0018] Preferably, the auxiliary extrusion resin is obtained by mixing the opening agent PET masterbatch and the PET base material in a mass ratio of 1:10.

[0019] The present invention also provides a method for preparing the PET release film base film with low surface roughness as described above, comprising the following steps:

[0020] S1, using auxiliary extrusion resin as the raw material for the two surface layers and main extrusion resin as the raw material for the core layer, after melting, three-layer co-extrusion is performed, the molten polyester resin is extruded, cooled, and cast to obtain a polyester cast sheet before stretching;

[0021] S2, longitudinally stretching the polyester cast sheet;

[0022] S3, stretching the polyester cast sheet after longitudinal stretching in the transverse direction;

[0023] S4. After completing the transverse stretching, heat setting, cooling and setting, and winding to obtain the PET release film base film with low surface roughness.

[0024] Preferably, the method for preparing the low surface roughness PET release film base film comprises the following steps:

[0025] S1. Using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, three layers are co-extruded after melting at 280°C, and the extrusion mass ratio of the surface layer: core layer: surface layer is controlled to be 1:8:1. The molten polyester resin is cooled after extrusion and cast on a cooling roll at 50°C to obtain a polyester cast sheet before stretching, and the thickness of the cast sheet is controlled to be 120-480 μm;

[0026] S2, preheating the polyester casting sheet at 70° C., and then longitudinally stretching the polyester casting sheet at 400° C. at a speed of 90 m / min, with the longitudinal stretching ratio controlled to be 1-4 times;

[0027] S3, preheating the longitudinally stretched polyester sheet at 120° C., and then transversely stretching it at 160° C., controlling the transverse stretching ratio to be 2-6 times;

[0028] S4. After completing the transverse stretching, heat setting at 240° C., then cooling and setting at 70° C., and winding to obtain the PET release film base film with low surface roughness.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a PET release film base film with low surface roughness and a preparation method thereof. The release film base film of the present invention has low surface roughness, low haze, and excellent comprehensive performance;

[0031] In the present invention, since the large-particle benzoic acid-modified nano-aluminum oxide has a refractive index very close to that of the PET base film, it can effectively avoid the adverse visual effects caused by the difference in refractive index at the interface between the large-particle nanoparticles and the resin matrix, and can effectively reduce the haze.

[0032] In the present invention, benzoic acid is used to modify nano-aluminum oxide, which can improve the dispersibility of the particles. The nano-aluminum oxide is compounded with nano-silicon dioxide particles of different particle sizes to obtain a PET opening agent masterbatch with low surface roughness, excellent friction properties, and excellent winding properties. At the same time, the present invention controls the crystallinity of the film by adjusting different stretch ratios (a larger stretch ratio corresponds to a higher polymer crystallinity), thereby improving the tensile strength of the film and the lamination effect between the film surface and the roller, and reducing the occurrence of scratches. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic structural diagram of a PET release film base film with low surface roughness according to the present invention.

[0034] Explanation of reference numerals: 1—core layer; 2—surface layer. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0036] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Materials and reagents used in the following examples are commercially available unless otherwise specified. In the following examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0038] 1 , the present invention provides a low surface roughness PET release film base film, the release film base film includes three stacked layers: a core layer 1 and two surface layers 2 located on both sides of the core layer 1, the release film base film is obtained by three-layer co-extrusion using a secondary extrusion resin as the raw material for the two surface layers 2 and a primary extrusion resin as the raw material for the core layer 1;

[0039] Among them, the auxiliary extrusion resin is obtained by mixing the opening agent PET masterbatch and the PET base material in a mass ratio of 1:5 to 1:15. The main extrusion resin is a pure PET base material. If the PET masterbatch content is too low, there will be no anti-adhesion performance, and if the PET masterbatch content is too high, the appearance will be poor.

[0040] Among them, the PET base material can be selected from one or more of the following: FG600 base material film-grade polyester chips provided by Sinopec Yizheng Chemical Fiber Co., Ltd., CZ-5011 super bright polyester chips provided by Jiangsu Sanfangxiang Group Co., Ltd., and TN8065S film-grade polyester chips provided by Teijin Limited of Japan.

[0041] In a preferred embodiment, the raw materials for preparing the opener PET masterbatch include the following components by weight: 30-120 parts of ethylene glycol, 19-79 parts of terephthalic acid monomer, 0.1-0.4 parts of antimony trioxide, 0.1-0.4 parts of nano-silicon dioxide, and 0.05-0.2 parts of modified nano-alumina.

[0042] More preferably, the raw materials for preparing the opening agent PET masterbatch include the following components by weight: 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silicon dioxide, and 0.1 parts of modified nano-alumina.

[0043] In a preferred embodiment, the particle size of nano-silicon dioxide is 40 nm to 200 nm, and the particle size of modified nano-alumina is 500 nm to 2 μm.

[0044] In a preferred embodiment, the modified nano-alumina is prepared by the following method: reflux alumina nanoparticles and benzoic acid in a mass ratio of 3:1 in toluene solvent at 90°C for 12 hours, wash with ethanol and dry at 80°C to obtain the modified nano-alumina.

[0045] In a preferred embodiment, the PET masterbatch of the opening agent is prepared by the following method:

[0046] By weight, 30-120 parts of ethylene glycol, 19-79 parts of terephthalic acid monomer, 0.1-0.4 parts of antimony trioxide, 0.1-0.4 parts of nano-silicon dioxide, and 0.05-0.2 parts of modified nano-alumina are added to a reactor, and an esterification reaction is carried out at 230-260° C. and 150-180 kPa for 1.5-5 hours, followed by a polycondensation reaction at 260-280° C. and 0.4-0.6 kPa for 1.5-6 hours. The obtained polyester resin is cooled in water and then cut. After removing water droplets with a vibrating screen, the resin is put into a dryer and dried in a nitrogen atmosphere at 120-160° C. for 6-24 hours to obtain an anti-blocking agent PET masterbatch.

[0047] In a preferred embodiment, the method for preparing a low surface roughness PET release film base film comprises the following steps:

[0048] S1. Using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, three layers are co-extruded after melting at 280°C, and the extrusion mass ratio of the surface layer: core layer: surface layer is controlled to be 1:8:1. The molten polyester resin is cooled after extrusion and cast on a cooling roll at 50°C to obtain a polyester cast sheet before stretching, and the thickness of the cast sheet is controlled to be 120-480 μm;

[0049] S2. Preheat the polyester casting sheet at 70°C, and then longitudinally stretch it at 400°C at a speed of 90m / min, controlling the longitudinal stretching ratio to be 1-4 times. Too large a ratio will easily cause the film to break;

[0050] S3, preheating the longitudinally stretched polyester sheet at 120° C., and then transversely stretching it at 160° C., controlling the transverse stretching ratio to 2-6 times to improve the mechanical strength in this direction;

[0051] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0052] In the present invention, benzoic acid-modified nano-alumina and nano-silica with a refractive index close to that of the substrate PET are used as opening agent fillers. The refractive index of the modified nano-alumina is 1.76, which is close to the refractive index of the polyester film, and it has good compatibility and high heat resistance. The large-particle-size nano-alumina used as the opening agent particles is less likely to be visually recognized during light exposure. At the same time, nano-silica has a relatively regular surface and a particle size of only one-fifteenth to one-fifth of the particle size of the modified nano-alumina. The use of small-particle-size nano-silica particles can improve dispersibility. After processing, despite the low surface roughness, it can maintain excellent friction properties, so that the film has excellent winding properties. At the same time, the temperature resistance of the MLCC release film base film can be effectively improved by precisely controlling the stretching process conditions.

[0053] The above is the overall concept of the present invention. Detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0054] The sources of the main raw materials involved in the following examples and comparative examples are as follows:

[0055] The PET base material was FG600-based film-grade polyester chips provided by Sinopec Yizheng Chemical Fiber Co., Ltd. Ethylene glycol was purchased from Shanghai Xiangheyi Chemical Technology Co., Ltd. Terephthalic acid was purchased from Hengli Petrochemical, and antimony trioxide was purchased from Wuxi Zhengmao Chemical Co., Ltd. All other materials whose manufacturers were not specified were commercially available.

[0056] Example 1

[0057] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0058] 1. Preparation of modified nano-alumina:

[0059] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0060] 2. Preparation of PET masterbatch of opening agent:

[0061] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0062] 3. Preparation of release film base film:

[0063] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and melting them at 280° C. to perform three-layer co-extrusion, controlling the extrusion mass ratio of the surface layer: the core layer: the surface layer to be 1:8:1. After precise measurement by a metering pump, the molten polyester resin is extruded from a lip die head, and cast on a cooling roller at 50° C. to obtain a polyester cast sheet before stretching, and controlling the thickness of the cast sheet to be 480 μm;

[0064] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 4 times. The film thickness after longitudinal stretching is about 120 μm.

[0065] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0066] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0067] Example 2

[0068] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0069] 1. Preparation of modified nano-alumina:

[0070] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0071] 2. Preparation of PET masterbatch of opening agent:

[0072] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0073] 3. Preparation of release film base film:

[0074] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and performing three-layer co-extrusion after melting at 280° C., controlling the extrusion mass ratio of the surface layer: core layer: surface layer to be 1:8:1, and after precise measurement by a metering pump, extruding the molten polyester resin from a lip die head, and casting on a cooling roller at 50° C. to obtain a polyester casting sheet before stretching, controlling the thickness of the casting sheet to be 240 μm;

[0075] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 2 times. The film thickness after longitudinal stretching is about 120 μm.

[0076] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0077] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0078] Example 3

[0079] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0080] 1. Preparation of modified nano-alumina:

[0081] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0082] 2. Preparation of PET masterbatch of opening agent:

[0083] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0084] 3. Preparation of release film base film:

[0085] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and performing three-layer co-extrusion after melting at 280° C., controlling the extrusion mass ratio of the surface layer: core layer: surface layer to be 1:8:1, and after precise measurement by a metering pump, extruding the molten polyester resin from a lip die head, and casting on a cooling roller at 50° C. to obtain a polyester casting sheet before stretching, controlling the thickness of the casting sheet to be 360 ​​μm;

[0086] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 3 times. The film thickness after longitudinal stretching is about 120 μm.

[0087] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0088] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0089] Example 4

[0090] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0091] 1. Preparation of modified nano-alumina:

[0092] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0093] 2. Preparation of PET masterbatch of opening agent:

[0094] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0095] 3. Preparation of release film base film:

[0096] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and performing three-layer co-extrusion after melting at 280° C., controlling the extrusion mass ratio of the surface layer: core layer: surface layer to be 1:8:1, and after precise measurement by a metering pump, extruding the molten polyester resin from a lip die head, and casting on a cooling roller at 50° C. to obtain a polyester casting sheet before stretching, controlling the thickness of the casting sheet to be 225 μm;

[0097] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 3 times. The film thickness after longitudinal stretching is about 75 μm.

[0098] S3, preheating the longitudinally stretched polyester sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to be 2.5 times, and the film thickness after transverse stretching to be 30 μm;

[0099] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0100] Example 5

[0101] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0102] 1. Preparation of modified nano-alumina:

[0103] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0104] 2. Preparation of PET masterbatch of opening agent:

[0105] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0106] 3. Preparation of release film base film:

[0107] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and performing three-layer co-extrusion after melting at 280° C., controlling the extrusion mass ratio of the surface layer: core layer: surface layer to be 1:8:1, and after precise measurement by a metering pump, extruding the molten polyester resin from a lip die head, and casting on a cooling roller at 50° C. to obtain a polyester casting sheet before stretching, and controlling the thickness of the casting sheet to be 180 μm;

[0108] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 1.5 times. The film thickness after longitudinal stretching is about 120 μm.

[0109] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0110] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0111] Example 6

[0112] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0113] 1. Preparation of modified nano-alumina:

[0114] Alumina nanoparticles and benzoic acid were refluxed in a toluene solvent at 90°C for 12 hours in a mass ratio of 3:1, and then washed with ethanol and dried at 80°C to obtain modified nano-alumina.

[0115] 2. Preparation of PET masterbatch of opening agent:

[0116] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of modified nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0117] 3. Preparation of release film base film:

[0118] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and performing three-layer co-extrusion after melting at 280° C., controlling the extrusion mass ratio of the surface layer: core layer: surface layer to be 1:8:1, and after precise measurement by a metering pump, extruding the molten polyester resin from a lip die head, and casting on a cooling roller at 50° C. to obtain a polyester casting sheet before stretching, controlling the thickness of the casting sheet to be 120 μm;

[0119] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 1. The film thickness after longitudinal stretching is approximately 120 μm.

[0120] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0121] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0122] Comparative Example 1

[0123] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0124] 1. Preparation of PET masterbatch for opening agent:

[0125] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, and 0.2 parts of nano-silica were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0126] 3. Preparation of release film base film:

[0127] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and melting them at 280° C. to perform three-layer co-extrusion, controlling the extrusion mass ratio of the surface layer: the core layer: the surface layer to be 1:8:1. After precise measurement by a metering pump, the molten polyester resin is extruded from a lip die head, and cast on a cooling roller at 50° C. to obtain a polyester cast sheet before stretching, and controlling the thickness of the cast sheet to be 480 μm;

[0128] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 4 times. The film thickness after longitudinal stretching is about 120 μm.

[0129] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0130] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0131] Comparative Example 2

[0132] A low-surface-roughness PET release film base film, the preparation method of which comprises the following steps:

[0133] 1. Preparation of PET masterbatch for opening agent:

[0134] By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, and 0.1 parts of nano-alumina were added to a reactor, and an esterification reaction was carried out at 255°C and 170kPa for 2.5 hours, and then a polycondensation reaction was carried out at 270°C and 0.567kPa for 3 hours. The obtained polyester resin was cooled in water and cut, and after removing water droplets with a vibrating screen, it was put into a dryer and dried in a nitrogen atmosphere at 140°C for 12 hours to obtain an opener PET masterbatch.

[0135] 3. Preparation of release film base film:

[0136] S1. Mixing the anti-blocking agent PET masterbatch with the PET base material in a mass ratio of 1:10 to obtain an auxiliary extrusion resin, using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, and melting them at 280° C. to perform three-layer co-extrusion, controlling the extrusion mass ratio of the surface layer: the core layer: the surface layer to be 1:8:1. After precise measurement by a metering pump, the molten polyester resin is extruded from a lip die head, and cast on a cooling roller at 50° C. to obtain a polyester cast sheet before stretching, and controlling the thickness of the cast sheet to be 480 μm;

[0137] S2. Preheat the polyester casting sheet at 70°C, then place it in an infrared heating zone at 400°C for longitudinal stretching at a speed of 90 m / min, with the longitudinal stretching ratio controlled at 4 times. The film thickness after longitudinal stretching is about 120 μm.

[0138] S3, preheating the longitudinally stretched polyester cast sheet at 120°C, and then transversely stretching it at 160°C, controlling the transverse stretching ratio to 4 times, and the film thickness after transverse stretching to 30 μm;

[0139] S4. After completing the transverse stretching, heat setting at 240°C, then cooling and setting at 70°C, and winding to obtain a PET release film base film with low surface roughness.

[0140] The release film base films prepared in Examples 1-6 and Comparative Examples 1-2 were subjected to relevant performance tests, and the test results are shown in Table 1 below:

[0141] Table 1

[0142] In the table:

[0143] 1. Surface roughness is measured using the international standard ISO468-1982 using the VR-6000 3D profilometer.

[0144] 2. Crystallinity was tested using the STAR thermal analysis system from Mettler Toledo.

[0145] 3. Transmittance and haze were tested using a Sannha haze transmittance meter, model: YS6002-M desktop transmittance and haze meter, according to the ASTM D1003 method.

[0146] 4. Elongation at break is tested using a SYSTESTER breaking strength / elongation tester.

[0147] 5. Processing stability evaluation: The film surfaces prepared in Examples and Comparative Examples were tested (hard coating and winding), collected in A4 size, and the number of air pockets in the A4 was counted using a fluorescent reflective light source. In this case, the evaluation criteria are as follows.

[0148] ◎: Very good 0 or less / A4

[0149] △: Normally 1 to 5 pieces / A4

[0150] ×: 6 or more missing / A4

[0151] 6. Appearance: Cut a finished polyester film, 1 meter wide and 1 meter long, and observe its appearance using a strong flashlight. If no scratches or scratches are visible, mark it as "◎"; if one very light scratch or scratch is faintly visible, but not definitive, mark it as "○"; if obvious scratches or scratches are visible, n (number) ≤ 5, mark it as "△"; if obvious scratches or scratches are visible across the entire surface, mark it as "×".

[0152] According to the test results in Table 1, the release film base films prepared in Examples 1-6 have low surface roughness and low haze, and excellent overall performance;

[0153] Different from Example 1, modified nano-alumina is not added to the opening agent PET masterbatch of Comparative Example 1, and unmodified nano-alumina is used in the opening agent PET masterbatch of Comparative Example 2. According to the test results of Comparative Example 1, Comparative Example 2 and Example 1, the release film base film prepared in Example 1 has significant advantages in transmittance and haze performance compared with the comparative example. In Example 1, since the modified nano-alumina particles with relatively large particle size are closer to the refractive index of the PET substrate, it is less likely to have a visual effect of different refractive index interfaces from the perspective of appearance. Since benzoic acid is used to modify the nano-alumina in the embodiment, the dispersibility of the particles can be improved, and by compounding with nano-silica particles with different particle sizes, a PET opening agent masterbatch with low surface roughness, excellent friction properties and excellent winding properties can be obtained. At the same time, the present invention controls the crystallinity of the film by adjusting different stretch ratios (a larger stretch ratio corresponds to a higher polymer crystallinity), which can improve the tensile strength of the film and the bonding effect between the film surface and the roller, and reduce the occurrence of scratches.

[0154] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A PET release film base film with low surface roughness, characterized in that, The release film base film comprises three layers arranged in a laminated manner: a core layer and two surface layers located on both sides of the core layer. The release film base film is obtained by three-layer co-extrusion with auxiliary extrusion resin as the raw material for the two surface layers and main extrusion resin as the raw material for the core layer; The auxiliary extrusion resin is obtained by mixing an anti-blocking agent PET masterbatch and a PET base material in a mass ratio of 1:5 to 1:15, and the main extrusion resin is a pure PET base material.

2. The low surface roughness PET release film base film according to claim 1, characterized in that, The preparation raw materials of the anti-blocking agent PET masterbatch include the following components by weight: 30 - 120 parts of ethylene glycol, 19 - 79 parts of terephthalic acid monomer, 0.1 - 0.4 parts of antimony trioxide, 0.1 - 0.4 parts of nano-silica, 0.05 - 0.2 parts of modified nano-aluminum oxide.

3. The low surface roughness PET release film base film according to claim 2, characterized in that, The preparation raw materials of the anti-blocking agent PET masterbatch include the following components by weight: 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, 0.1 parts of modified nano-aluminum oxide.

4. The low surface roughness PET release film base film according to claim 2, wherein, The particle size of the nano-silica is 40nm - 200nm, and the particle size of the modified nano-aluminum oxide is 500nm - 2μm.

5. The low surface roughness PET release film base film according to claim 2, characterized in that, The modified nano-aluminum oxide is prepared by the following method: Alumina nanoparticles and benzoic acid are refluxed in a toluene solvent at 90°C for 12h in a mass ratio of 3:1, and after being washed with ethanol and dried at 80°C, the modified nano-aluminum oxide is obtained.

6. The low surface roughness PET release film base film according to claim 2, characterized in that, The anti-blocking agent PET masterbatch is prepared by the following method: By weight, 30 - 120 parts of ethylene glycol, 19 - 79 parts of terephthalic acid monomer, 0.1 - 0.4 parts of antimony trioxide, 0.1 - 0.4 parts of nano-silica, 0.05 - 0.2 parts of modified nano-aluminum oxide are added to a reaction kettle, and an esterification reaction is carried out at 230 - 260°C and 150 - 180kPa for 1.5 - 5h, and then a polycondensation reaction is carried out at 260 - 280°C and 0.4 - 0.6kPa for 1.5 - 6h. The obtained polyester resin is cooled in water and then cut. After removing water droplets by a vibrating sieve, it is put into a dryer and dried in a nitrogen atmosphere at 120 - 160°C for 6 - 24h to obtain the anti-blocking agent PET masterbatch.

7. The low surface roughness PET release film base film according to claim 6, characterized in that The anti-blocking agent PET masterbatch is prepared by the following method: By weight, 60 parts of ethylene glycol, 39.5 parts of terephthalic acid monomer, 0.2 parts of antimony trioxide catalyst, 0.2 parts of nano-silica, 0.1 parts of modified nano-aluminum oxide are added to a reaction kettle, and an esterification reaction is carried out at 255°C and 170kPa for 2.5h, and then a polycondensation reaction is carried out at 270°C and 0.567kPa for 3h. The obtained polyester resin is cooled in water and then cut. After removing water droplets by a vibrating sieve, it is put into a dryer and dried in a nitrogen atmosphere at 140°C for 12h to obtain the anti-blocking agent PET masterbatch.

8. The low surface roughness PET release film base film according to claim 1, wherein The auxiliary extrusion resin is obtained by mixing an anti-blocking agent PET masterbatch and a PET base material in a mass ratio of 1:

10.

9. A method for preparing a low surface roughness PET release film base film according to any one of claims 1-8, characterized in that, Including the following steps: S1. Using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, after melting, perform three-layer co-extrusion. After the molten polyester resin is extruded, it is cooled and cast into a sheet to obtain the polyester sheet before stretching; S2. Perform longitudinal stretching on the polyester sheet; S3. Perform transverse stretching on the longitudinally stretched polyester sheet; S4. After completing the transverse stretching, perform heat setting, then cooling and setting, and winding to obtain the base film of the low surface roughness PET release film.

10. The preparation method of the low surface roughness PET release film base film according to claim 1, characterized in that, The method includes the following steps: S1. Using the auxiliary extrusion resin as the raw material for the two surface layers and the main extrusion resin as the raw material for the core layer, after melting at 280 °C, perform three-layer co-extrusion, and control the mass ratio of the extrusion amount of the surface layer: core layer: surface layer to be 1:8:

1. After the molten polyester resin is extruded, it is cooled and cast into a sheet on a cooling roller at 50 °C to obtain the polyester sheet before stretching, and control the thickness of the sheet to be 120 - 480 μm; S2. Preheat the polyester sheet at 70 °C, and then perform longitudinal stretching at 400 °C at a speed of 90 m / min, and control the longitudinal stretching ratio to be 1 - 4 times; S3. Preheat the longitudinally stretched polyester sheet at 120 °C, and then perform transverse stretching at 160 °C, and control the transverse stretching ratio to be 2 - 6 times; S4. After completing the transverse stretching, perform heat setting at 240 °C, then perform cooling and setting at 70 °C, and wind to obtain the base film of the low surface roughness PET release film.

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