High-gloss low-haze polyester masterbatch, preparation method and application thereof

Abstract

The application relates to the technical field of optical film preparation, in particular to high-gloss low-haze polyester masterbatch and a preparation method and application thereof. The high-gloss low-haze polyester masterbatch comprises PET resin, stearic acid modified spherical or spherical-like micron or sub-micron calcium carbonate, silane coupling agent modified spherical nano gamma-Al2O3, dendritic polymer dispersant with a thermal decomposition temperature of greater than or equal to 300 DEG C, and an antioxidant. The stearic acid modified spherical or spherical-like micron or sub-micron calcium carbonate is compounded with the silane coupling agent modified spherical nano gamma-Al2O3, and the dendritic polymer dispersant with a thermal decomposition temperature of greater than or equal to 300 DEG C is combined, so that the film haze is effectively reduced, the glossiness is improved, and the film surface cleanliness is improved while the good opening performance is ensured.

Description

Technical Field

[0001] This invention relates to the field of optical thin film preparation technology, specifically to a high-gloss, low-haze polyester masterbatch, its preparation method, and its application. Background Technology

[0002] Biaxially oriented polyester film (BOPET) is widely used in optical displays, electronics, packaging and printing due to its excellent strength, transparency, dimensional stability and heat resistance. Especially in high-end optical fields such as liquid crystal displays, polarizer protective films, release films, and brightness enhancement films, extremely high requirements are placed on the optical properties of the film, such as transmittance, haze, and clarity. However, during the production and use of BOPET film, the smooth surface and the interaction of polar groups make it prone to sticking during winding and unwinding. To solve this problem, industrially, an opening agent is usually added to the film surface in the form of a masterbatch, forming microscopic protrusions on the film surface, thereby reducing the coefficient of friction and improving opening performance.

[0003] Currently used opening agents include silica, organic microparticles, and barium sulfate. Among these, silica has a large discrepancy between its refractive index and that of the PET matrix, and its compatibility is insufficient, easily leading to increased film haze and decreased light transmittance. While organic microparticles offer some improvement in refractive index matching, they pose a risk of thermal decomposition under the high-temperature processing environment of BOPET, easily generating precipitates that contaminate the film surface. Barium sulfate, due to its high specific gravity, tends to settle during melt extrusion, resulting in uneven dispersion and consequently causing uneven optical properties and surface defects in the film. Therefore, achieving good opening performance while simultaneously ensuring low haze, high gloss, and film surface cleanliness has become a pressing technical challenge. Summary of the Invention

[0004] This invention provides a high-gloss, low-haze polyester masterbatch, its preparation method, and its application, to solve the problem that existing open-end masterbatches cannot simultaneously achieve good open-end performance, low haze, high gloss, and film surface cleanliness.

[0005] In a first aspect, the present invention provides a high-gloss, low-haze polyester masterbatch, comprising: PET resin, stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified spherical nano-sized γ-Al2O3, a dendritic polymer dispersant with a thermal decomposition temperature ≥300℃, and an antioxidant.

[0006] In one optional embodiment, based on 100 parts by weight of the total mass of the high-gloss, low-haze polyester masterbatch, the PET resin comprises 90-99 parts by weight, the stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate comprises 0.5-5 parts by weight, the silane coupling agent-modified spherical nano-sized γ-Al2O3 comprises 0.1-2 parts by weight, the dendritic polymer dispersant with a thermal decomposition temperature ≥300℃ comprises 0.1-2 parts by weight, and the antioxidant comprises 0.1-2 parts by weight. As an example, the PET resin can be 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 parts by weight, and specific values ​​between the above points; the stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 parts by weight, and specific values ​​between the above points; the silane coupling agent-modified spherical nano-sized γ-Al2O3 can be 0.1, 0.3, 0.5, 0.7, ... The amounts are 0.9, 1, 1.2, 1.5, 1.8, or 2 parts by weight, and specific values ​​between these values; the dendritic polymer dispersant with a thermal decomposition temperature ≥300℃ can be 0.1, 0.3, 0.5, 0.7, 0.9, 1, 1.2, 1.5, 1.8, or 2 parts by weight, and specific values ​​between these values; the antioxidant can be 0.1, 0.3, 0.5, 0.7, 0.9, 1, 1.2, 1.5, 1.8, or 2 parts by weight, and specific values ​​between these values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0007] In one optional embodiment, the central particle size D50 of the spherical or near-spherical micron- to submicron-sized calcium carbonate is 0.5 μm to 1.5 μm; as an example, the central particle size D50 of the spherical or near-spherical micron- to submicron-sized calcium carbonate can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or 1.5 μm, as well as specific values ​​between the above values; for space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0008] And / or, the central particle size D50 of the spherical nanoscale γ-Al2O3 is 10 nm to 100 nm. The central particle size D50 of the spherical nanoscale γ-Al2O3 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, as well as specific values ​​between these ranges. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0009] In one optional embodiment, the mass ratio of stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate to silane coupling agent-modified spherical nano-sized γ-Al₂O₃ is (3~5):1. As an example, the mass ratio can be 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, or 5:1, as well as specific values ​​between these ranges. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0010] In one alternative embodiment, the silane coupling agent comprises an aminosilane coupling agent and / or an epoxysilane coupling agent.

[0011] In one optional embodiment, the end functional groups of the dendritic polymer dispersant with a thermal decomposition temperature ≥300°C include at least one of carboxyl, hydroxyl, and amino groups.

[0012] In one alternative embodiment, the PET resin comprises optical grade PET resin; And / or, the intrinsic viscosity of the PET resin is 0.65 dL / g to 0.70 dL / g. As an example, the intrinsic viscosity can be 0.65 dL / g, 0.66 dL / g, 0.67 dL / g, 0.68 dL / g, 0.69 dL / g, or 0.70 dL / g, as well as specific values ​​between these values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0013] In one alternative embodiment, the antioxidant includes, but is not limited to, pentaerythritol ester antioxidants.

[0014] In a second aspect, the present invention also provides a method for preparing a high-gloss, low-haze polyester masterbatch as described in the first aspect, comprising: adding PET resin and other components separately or in combination to an extruder, and then performing melt extrusion granulation to obtain a high-gloss, low-haze polyester masterbatch; wherein the other components include stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified spherical nano-sized γ-Al2O3, a dendritic polymer dispersant with a thermal decomposition temperature ≥300℃, and an antioxidant.

[0015] In one optional embodiment, the stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified alumina, dendritic polymer dispersant, and antioxidant are premixed at a mixing speed of 800 rpm to 1500 rpm and a mixing time of 5 min to 15 min. As an example, the mixing speed can be 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, or 1500 rpm, or specific values ​​between these values; the mixing time can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min, or specific values ​​between these values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0016] In one optional embodiment, the melt extrusion processing temperature is 250℃~280℃, and the screw speed is 200rpm~400rpm. As an example, the processing temperature can be 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, or 280℃, or specific values ​​between these values; the screw speed can be 200rpm, 220rpm, 240rpm, 260rpm, 280rpm, 300rpm, 320rpm, 340rpm, 360rpm, 380rpm, or 400rpm, or specific values ​​between these values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0017] In one optional embodiment, the PET resin is dried before addition. Optionally, the drying temperature is 150°C to 170°C, and after drying, the moisture content of the polyester resin is ≤1000ppm. As an example, the drying temperature can be 150°C, 155°C, 160°C, 165°C, or 170°C, or specific values ​​between these values; the moisture content can be 1000ppm, 900ppm, 800ppm, 700ppm, 600ppm, 500ppm, or lower, or specific values ​​between these values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0018] Thirdly, the present invention also provides the application of the high-gloss, low-haze polyester masterbatch described in the first aspect or the high-gloss, low-haze polyester masterbatch prepared by the preparation method of the high-gloss, low-haze polyester masterbatch described in the second aspect in the preparation of BOPET film.

[0019] The technical solution of this invention has the following advantages: This invention uses PET resin, stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified spherical nano-sized γ-Al2O3, dendritic polymer dispersant with a thermal decomposition temperature ≥300℃, and antioxidants to form a polyester masterbatch. Specifically, the stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, after stearic acid modification, undergoes a surface chemical reaction between the carboxyl group at one end of the stearic acid and the calcium ions in the calcium carbonate surface lattice, forming an in-situ calcium stearate coating layer. The long-chain alkyl group at the other end imparts hydrophobic properties to the particles, improving their compatibility with PET and reducing light scattering caused by interfacial incompatibility. This calcium carbonate forms microscopic protrusions on the film surface to ensure opening performance. Its spherical morphology forms arc-shaped protrusions on the film surface, resulting in the weakest light scattering. Furthermore, its refractive index matches the PET matrix, reducing the increase in haze caused by refractive index deviation. Simultaneously, the spherical structure transforms the sliding friction between the particles and the roller into rolling friction, reducing equipment wear. After modification with silane coupling agent, spherical nano-sized γ-Al2O3 exhibits a Si-O-Al chemical bond formed by the hydrolyzable group at one end of the silane coupling agent and the hydroxyl group on the surface of aluminum oxide through hydrolysis and condensation. The organic functional group at the other end end endows the particle surface with organic reactivity, improving its compatibility with PET. The particle size of this γ-Al2O3 is much smaller than the wavelength of visible light, resulting in almost no scattering of visible light and minimal impact on haze. The oxygen vacancy defects in its γ-lattice generate photoluminescence under ultraviolet light excitation, converting invisible ultraviolet light into blue-violet light and increasing the total emitted light flux. Simultaneously, it acts as a heterogeneous nucleating agent, promoting the formation of fine and uniform crystal structures in PET and suppressing diffuse scattering of light by large spherulites, thereby improving gloss. The dendritic polymer dispersant has a thermal decomposition temperature ≥300℃ and does not decompose under high-temperature processing conditions, avoiding crystal points on the film surface. Its end groups can adsorb onto exposed areas of inorganic particles that are not completely covered by the modifier, forming a secondary coating. Furthermore, it prevents particle agglomeration through steric hindrance, ensuring uniform distribution of the two inorganic powders. Antioxidants prevent thermal oxidative degradation of the masterbatch during high-temperature processing. The synergistic effect of these components ensures good opening performance while also achieving low haze, high gloss, and a clean film surface. Detailed Implementation

[0020] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0021] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] The sources of some of the raw materials used in the following examples and comparative examples are shown in Table 1 below: Table 1

[0023] Preparation of stearic acid modified calcium carbonate: (1) Calcium carbonate powder was dried at 100℃ for 2 hours; (2) The dried calcium carbonate powder was added to a high-speed mixer, heated to 120℃, and stearic acid with a dosage of 1.0 wt% of calcium carbonate was added and stirred for 50 minutes; (3) The mixture was cooled and discharged to obtain stearic acid modified calcium carbonate. The stearic acid was dissolved in anhydrous ethanol before being added.

[0024] Silane coupling agent modified nano-γ-Al2O3: (1) Dissolve the silane coupling agent (KH-550, γ-aminopropyltriethoxysilane) in a mixed solvent of ethanol and water, with an ethanol / water volume ratio of 95:5, and adjust the pH to 3-4 to promote silane hydrolysis. The amount of coupling agent used is about 3 wt% of the nano-γ-Al2O3; (2) Add the γ-Al2O3 powder to the above solution and disperse it fully by high-speed stirring. Heat the system to 70°C and react for 3 hours under reflux stirring; (3) After the reaction is completed, separate the modified powder by centrifugation or filtration, and wash it repeatedly with anhydrous ethanol to remove unreacted coupling agent. Finally, dry the product under vacuum at 100°C and grind it to obtain silane coupling agent modified nano-γ-Al2O3.

[0025] Stearic acid modified barium sulfate: (1) Dry barium sulfate powder at 100℃ for 2 hours; (2) Add the dried barium sulfate powder to a high-speed mixer, heat to 120℃, add stearic acid at a dosage of 1.5wt% of barium sulfate, and stir for 50 minutes; (3) Cool and discharge to obtain stearic acid modified barium sulfate. The stearic acid is dissolved in anhydrous ethanol before being added.

[0026] Example 1 This embodiment provides a method for preparing a high-gloss, low-haze polyester masterbatch, the specific steps of which are as follows: (1) Dry the PET resin at 160℃ for 5 hours until the moisture content is ≤1000ppm, and set aside for later use. The PET resin is optical grade PET resin with an intrinsic viscosity of 0.65~0.70dL / g.

[0027] (2) Weigh the following components in the indicated weight proportions: 98.3 parts PET resin, 0.9 parts stearic acid modified spherical calcium carbonate, 0.3 parts silane coupling agent modified spherical nano-γ-Al2O3, 0.3 parts dendritic polymer dispersant, and 0.2 parts antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). The mass ratio of stearic acid modified spherical calcium carbonate to silane coupling agent modified spherical nano-γ-Al2O3 is 3:1. The central particle size D50 of the stearic acid modified spherical calcium carbonate is 1 μm, and the central particle size D50 of the silane coupling agent modified spherical nano-γ-Al2O3 is 20 nm.

[0028] (3) The weighed stearic acid modified spherical calcium carbonate, silane coupling agent modified spherical nano-γ-Al2O3, dendritic polymer dispersant and antioxidant are added to a high-speed mixer and premixed at 1200 rpm for 10 minutes to obtain a premix.

[0029] (4) The PET resin dried in step (1) is fed into the main feed port of the twin-screw extruder, and the premix obtained in step (3) is fed into the side feed port. The mixture is melt-extruded and granulated under the conditions of processing temperature of 260°C and screw speed of 300 rpm to obtain high-gloss and low-mist polyester masterbatch.

[0030] Example 2 This embodiment provides a method for preparing a high-gloss, low-haze polyester masterbatch, the specific steps of which are as follows: (1) Dry the PET resin at 160℃ for 5 hours until the moisture content is ≤1000ppm, and set aside for later use. The PET resin is optical grade PET resin with an intrinsic viscosity of 0.65~0.70dL / g.

[0031] (2) Weigh the following components according to the following weight proportions: 95.6 parts PET resin, 3 parts stearic acid modified spherical calcium carbonate, 0.6 parts silane coupling agent modified spherical nano-γ-Al2O3, 0.6 parts dendritic polymer dispersant, and 0.2 parts antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). The mass ratio of stearic acid modified spherical calcium carbonate to silane coupling agent modified spherical nano-γ-Al2O3 is 5:1. The central particle size D50 of the stearic acid modified spherical calcium carbonate is 1 μm, and the central particle size D50 of the silane coupling agent modified spherical nano-γ-Al2O3 is 20 nm.

[0032] (3) The weighed stearic acid modified spherical calcium carbonate, silane coupling agent modified spherical nano-γ-Al2O3, dendritic polymer dispersant and antioxidant are added to a high-speed mixer and premixed at 1200 rpm for 10 minutes to obtain a premix.

[0033] (4) The PET resin dried in step (1) is fed into the main feed port of the twin-screw extruder, and the premix obtained in step (3) is fed into the side feed port. The mixture is melt-extruded and granulated under the conditions of processing temperature of 260°C and screw speed of 300 rpm to obtain high-gloss and low-mist polyester masterbatch.

[0034] Example 3 This embodiment provides a method for preparing a high-gloss, low-haze polyester masterbatch, the specific steps of which are as follows: (1) Dry the PET resin at 150℃ for 6 hours until the moisture content is ≤1000ppm, and set aside for later use. The PET resin is optical grade PET resin with an intrinsic viscosity of 0.65~0.70dL / g.

[0035] (2) Weigh the following components according to the following weight proportions: 90 parts PET resin, 5 parts stearic acid modified spherical calcium carbonate, 2 parts silane coupling agent modified spherical nano-γ-Al2O3, 2 parts dendritic polymer dispersant, and 1 part antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). The mass ratio of stearic acid modified spherical calcium carbonate to silane coupling agent modified spherical nano-γ-Al2O3 is 3:1. The central particle size D50 of the stearic acid modified spherical calcium carbonate is 1 μm, and the central particle size D50 of the silane coupling agent modified spherical nano-γ-Al2O3 is 20 nm.

[0036] (3) The weighed stearic acid modified spherical calcium carbonate, silane coupling agent modified spherical nano-γ-Al2O3, dendritic polymer dispersant and antioxidant are added to a high-speed mixer and premixed at 800 rpm for 15 minutes to obtain a premix.

[0037] (4) The PET resin dried in step (1) is fed into the main feed port of the twin-screw extruder, and the premix obtained in step (3) is fed into the side feed port. The mixture is melt-extruded and granulated under the conditions of processing temperature of 250°C and screw speed of 200 rpm to obtain high-gloss and low-mist polyester masterbatch.

[0038] Example 4 This embodiment provides a method for preparing a high-gloss, low-haze polyester masterbatch, the specific steps of which are as follows: (1) Dry the PET resin at 170℃ for 4 hours until the moisture content is ≤1000ppm, and set aside for later use. The PET resin is optical grade PET resin with an intrinsic viscosity of 0.65~0.70dL / g.

[0039] (2) Weigh the following components according to the following weight proportions: 98 parts PET resin, 0.5 parts stearic acid modified spherical calcium carbonate, 0.1 parts silane coupling agent modified spherical nano-γ-Al2O3, 0.5 parts dendritic polymer dispersant, and 0.9 parts antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). The mass ratio of stearic acid modified spherical calcium carbonate to silane coupling agent modified spherical nano-γ-Al2O3 is 5:1. The central particle size D50 of the stearic acid modified spherical calcium carbonate is 1 μm, and the central particle size D50 of the silane coupling agent modified spherical nano-γ-Al2O3 is 20 nm.

[0040] (3) The weighed stearic acid modified spherical calcium carbonate, silane coupling agent modified spherical nano-γ-Al2O3, dendritic polymer dispersant and antioxidant are added to a high-speed mixer and premixed at 1500 rpm for 5 minutes to obtain a premix.

[0041] (4) The PET resin dried in step (1) is fed into the main feed port of the twin-screw extruder, and the premix obtained in step (3) is fed into the side feed port. The mixture is melt-extruded and granulated under the conditions of processing temperature of 280°C and screw speed of 400 rpm to obtain high-gloss and low-mist polyester masterbatch.

[0042] Comparative Example 1 This comparative example provides a method for preparing polyester masterbatch, which differs from Example 1 in that silane coupling agent is not added to modify γ-Al2O3, and the amount of stearic acid-modified spherical calcium carbonate is adjusted from 0.9 parts by weight to 1.2 parts by weight so that the total amount of inorganic powder added is the same as in Example 1. Other conditions are the same as in Example 1.

[0043] Comparative Example 2 This comparative example provides a method for preparing polyester masterbatch, which differs from Example 2 in that stearic acid-modified irregular heavy calcium carbonate is used instead of stearic acid-modified spherical calcium carbonate, while other conditions are the same as in Example 2.

[0044] Comparative Example 3 This comparative example provides a method for preparing a polyester masterbatch, which differs from Example 2 in that ethylene bis-stearamide (EBS) is used instead of the dendritic polymer dispersant, while other conditions are the same as in Example 2.

[0045] Comparative Example 4 This comparative example provides a method for preparing polyester masterbatch, which differs from Example 1 in that the spherical calcium carbonate is not modified with stearic acid, while other conditions are the same as in Example 1.

[0046] Comparative Example 5 This comparative example provides a method for preparing polyester masterbatch, which differs from Example 1 in that the spherical nano-sized γ-Al2O3 is not modified with a silane coupling agent, while other conditions are the same as in Example 1.

[0047] Comparative Example 6 This comparative example provides a method for preparing polyester masterbatch, which differs from Example 1 in that stearic acid-modified spherical barium sulfate is used instead of stearic acid-modified near-spherical calcium carbonate, while other conditions are the same as in Example 1.

[0048] Comparative Example 7 This comparative example provides a method for preparing a polyester masterbatch, which differs from Example 1 in that an antioxidant is not added, and the amount of PET resin is adjusted from 98.3 parts by weight to 98.5 parts by weight so that the total amount of additives added to the PET resin remains the same as in Example 1. Other conditions are the same as in Example 1.

[0049] Test Example 1 Masterbatch performance testing: The viscosity and moisture content of the masterbatches prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were tested. The test results are shown in Table 2 below. The specific test methods are as follows: (1) Viscosity: determined according to GB / T 14190-2017; (2) Moisture content: determined in accordance with GB / T 6284-2006; (3) Pressure difference: Measured according to ISO 23900-5:2015 (the larger the value, the worse the filtration performance); (4) b value: Measured using a desktop spectrophotometer (the higher the b value, the yellower the material).

[0050] Table 2 Performance test results of the masterbatches obtained in each embodiment and comparative example

[0051] Test Example 2 Film preparation: The masterbatches obtained in Examples 1-4 and Comparative Examples 1-7 were mixed with optical-grade PET resin at a ratio of 3% of the masterbatch addition. BOPET films were then prepared using a three-layer co-extrusion BOPET production line. The film structure was an A / B / A three-layer structure, with the masterbatch added to the upper and lower surface layers (layer A). Each surface layer was 3 μm thick, accounting for 10% of the total thickness. The stretching process was as follows: longitudinal stretch ratio 3.0, transverse stretch ratio 3.5, and heat setting temperature 215℃.

[0052] Performance testing: The BOPET film was tested for haze, gloss, adhesion, roughness, and crystal point number. The test results are shown in Table 3 below. The specific test methods are as follows: (1) Haze: The haze was measured according to standard GB / T 2410-2008 (the lower the haze value, the better); (2) Gloss: The gloss of the specimen (45°) is tested according to the standard ASTM D-2457-21 (the higher the gloss value, the better); (3) Adhesion: Measured according to standard ASTM D 3354-2015 (the lower the adhesion, the easier the film is to open). (4) Roughness: Measured according to standard JIS B0601-1994 (too low roughness affects the opening, too high roughness affects the gloss and haze). (5) Number of crystal points: Count the number of crystal points per square meter of film surface (the fewer the number of crystal points, the better the cleanliness).

[0053] Table 3 Performance test results of BOPET films prepared from the masterbatches obtained in each embodiment and comparative example

[0054] Based on the above test results, the high-gloss, low-haze polyester masterbatches prepared in Examples 1 to 4 of this invention all exhibit excellent comprehensive performance. Their intrinsic viscosity remains at a relatively high level of 0.5777 dL / g to 0.6079 dL / g, their moisture content is controlled below 1100 ppm, their pressure difference is not higher than 4.33 bar, and their b-value is not higher than 4.1. When these masterbatches are made into BOPET films, the haze does not exceed 0.80%, the gloss reaches above 136 Gu, and the adhesion is not higher than 9.7 g / cm³. 2 (Indicating good film opening properties), the roughness Ra is controlled within a suitable range of 8.6~9.3 nm, and the number of crystal points does not exceed 4 / m. 2 (Indicating high membrane surface cleanliness). The above results demonstrate that Examples 1-4 of this invention, by compounding stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate with silane coupling agents to PET resin to modify spherical nano-sized γ-Al₂O₃, and adding dendritic polymer dispersants with a thermal decomposition temperature ≥300℃ and antioxidants, achieves good opening performance (adhesive strength ≤9.7 g / cm). 2 At the same time, it achieves low haze (≤0.80%), high gloss (≥136Gu) and high film surface cleanliness (crystal point count ≤4 / m). 2 This effectively solves the technical problem that existing open-end masterbatches cannot simultaneously achieve good open-end performance, low haze, high gloss, and film surface cleanliness.

[0055] Among them, Example 1 exhibited the best overall performance, maintaining low haze (0.75%) and high gloss (136 Gu) while having the lowest pressure drop (3.21 bar) and lowest b-value (3.8), indicating its optimal dispersibility and heat resistance. Example 2, due to the highest total amount of inorganic powder added (3.6 parts), showed a slight increase in haze (0.80%), but its gloss improved to 139 Gu, while its adhesion decreased to the lowest (6.5 g / cm). 2 The opening is optimal; Examples 3 and 4 also maintain good overall performance.

[0056] In contrast, Comparative Examples 1 through 7 failed to simultaneously achieve low haze, high gloss, good opening performance, and excellent membrane surface cleanliness. Specifically, Comparative Example 1, without the addition of a silane coupling agent to modify nano-γ-Al₂O₃, still exhibited a low haze (0.72%), but the pressure differential increased to 4.12 bar, and the b-value rose to 4.3. This indicates that relying solely on inorganic particles and dispersants is insufficient to achieve good dispersion, resulting in decreased filtration performance and reduced heat resistance.

[0057] Comparative Example 2 used stearic acid-modified random heavy calcium carbonate to replace spherical calcium carbonate. The pressure difference increased sharply to 40.3 bar, the haze soared to 1.63%, the roughness increased to 16.3 nm, and the number of crystal points increased to 10 / m. 2 The adhesion strength is 8.7 g / cm. 2 (The opening properties are acceptable), but it indicates that irregularly shaped particles cause significant wear to the equipment, have poor dispersion, and severely degrade the optical and processing properties of the thin film.

[0058] Comparative Example 3, which used EBS to replace the dendritic polymer dispersant, achieved a pressure differential of up to 15.7 bar, a b-value of 13.2, a haze of 1.33%, and a crystal point count of 13 / m³. 2 This indicates that the dispersion effect of EBS is far inferior to that of dendritic polymers, and the cleanliness of the membrane surface is severely degraded.

[0059] Comparative Example 4, without stearic acid modification of calcium carbonate, exhibited a pressure differential of 38.9 bar, a haze of 1.0%, a roughness of 15.4 nm, a b-value of 8.8, and an adhesion strength of 10.7 g / cm. 2 (Poor opening performance) indicates that unmodified calcium carbonate has poor compatibility with PET resin, resulting in severe agglomeration and an inability to balance opening performance and optical performance.

[0060] Comparative Example 5, without silane coupling agent modification of nano-γ-Al₂O₃, exhibited a pressure differential of 23.1 bar, a haze of 0.88%, a b-value of 7.2, and an adhesion strength of 10.5 g / cm³. 2 (Poor opening properties) indicates that unmodified nano-alumina has poor compatibility with PET resin, resulting in severe agglomeration and deteriorated processing performance.

[0061] Comparative Example 6, using stearic acid-modified spherical barium sulfate instead of spherical calcium carbonate, achieved a pressure differential of 33.3 bar and an adhesion strength as high as 15.6 g / cm³. 2 (Severe deterioration of opening properties), haze 0.76%, b value 7.9, indicating that although barium sulfate has good optical effects, its high specific gravity makes it easy to settle, resulting in uneven dispersion and excessive pressure difference; there are fewer particles per unit area, and the adhesion increases.

[0062] Comparative Example 7, without added antioxidants, showed acceptable pressure differential (3.45 bar) and haze (0.81%), but its b-value increased to 8.9 and the number of crystal points increased to 9 per m³. 2 The adhesive strength is 9.3 g / cm. 2 (The opening is acceptable), indicating that the PET underwent thermal oxidative degradation during processing, which seriously affected the product's appearance and cleanliness.

[0063] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-gloss, low-haze polyester masterbatch, characterized in that, include: PET resin, stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified spherical nano-sized γ-Al2O3, dendritic polymer dispersants with a thermal decomposition temperature ≥300℃, and antioxidants.

2. The high-gloss, low-haze polyester masterbatch according to claim 1, characterized in that, Based on 100 parts by weight of the total mass of the high-gloss, low-haze polyester masterbatch, the PET resin comprises 90-99 parts by weight, the stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate comprises 0.5-5 parts by weight, the silane coupling agent-modified spherical nano-sized γ-Al2O3 comprises 0.1-2 parts by weight, the dendritic polymer dispersant with a thermal decomposition temperature ≥300℃ comprises 0.1-2 parts by weight, and the antioxidant comprises 0.1-2 parts by weight.

3. The high-gloss, low-haze polyester masterbatch according to claim 1 or 2, characterized in that, The central particle size D50 of the spherical or near-spherical micron- to submicron-sized calcium carbonate is 0.5 μm to 1.5 μm; And / or, the central particle size D50 of the spherical nanoscale γ-Al2O3 is 10nm~100nm.

4. The high-gloss, low-haze polyester masterbatch according to claim 1 or 2, characterized in that, The mass ratio of stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate to silane coupling agent-modified spherical nano-sized γ-Al2O3 is (3~5):

1.

5. The high-gloss, low-haze polyester masterbatch according to claim 1 or 2, characterized in that, The silane coupling agent includes aminosilane coupling agents and / or epoxysilane coupling agents.

6. The high-gloss, low-haze polyester masterbatch according to claim 1 or 2, characterized in that, The end functional groups of the dendritic polymer dispersant with a thermal decomposition temperature ≥300℃ include at least one of carboxyl, hydroxyl, and amino groups.

7. The high-gloss, low-haze polyester masterbatch according to claim 1 or 2, characterized in that, The PET resin includes optical grade PET resin; And / or, the intrinsic viscosity of the PET resin is 0.65 dL / g to 0.70 dL / g.

8. A method for preparing a high-gloss, low-haze polyester masterbatch as described in any one of claims 1 to 7, characterized in that, include: PET resin and the remaining components are added to an extruder separately or in combination, and then melt-extruded and granulated to obtain a high-gloss, low-mist polyester masterbatch. The remaining components include stearic acid-modified spherical or near-spherical micron- to submicron-sized calcium carbonate, silane coupling agent-modified spherical nano-sized γ-Al2O3, dendritic polymer dispersant with a thermal decomposition temperature ≥300℃, and antioxidant.

9. The method for preparing high-gloss, low-haze polyester masterbatch according to claim 8, characterized in that, The PET resin is dried before being added.

10. The application of the high-gloss, low-haze polyester masterbatch according to any one of claims 1 to 7, or the high-gloss, low-haze polyester masterbatch prepared by the preparation method of the high-gloss, low-haze polyester masterbatch according to claim 8 or 9, in the preparation of BOPET film.

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