Nano-cellulose reinforced optical PET release film and preparation method thereof

Abstract

The invention discloses a nano-cellulose reinforced optical PET release film and a preparation method thereof, and belongs to the technical field of functional polymer composites.The method includes the steps that cerium / zinc double-doped nano-cellulose slurry is prepared through hexafluoroisopropanol assisted ball milling, an MOF structure grows in situ to obtain double-metal MOF composite nano-cellulose, and then the double-metal MOF composite nano-cellulose is prepared; the preparation method comprises the following steps: preparing nano-crystalline cellulose, carrying out copolymerization coating on the nano-crystalline cellulose with aniline and o-aminobenzoic acid to obtain modified nano-crystalline cellulose, carrying out melt blending on the modified nano-crystalline cellulose, PET, a chain extender and the like to obtain a PET base film, coating release layer slurry, and carrying out plasma cleaning, drying, UV curing and curing to obtain the nano-crystalline cellulose reinforced optical PET release film. According to the invention, agglomeration of the nano-cellulose is effectively inhibited through multiple modification, and the compatibility of the nano-cellulose and PET is remarkably improved, so that the PET release film has excellent mechanical properties, optical transparency and micro-area repairing capability, and can meet the strict requirements of the high-end display field on an OCA optical cement protection material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional polymer composite materials, and particularly relates to a nanocellulose-reinforced optical-grade PET release film and a preparation method thereof. BACKGROUND

[0002] The PET release film is a film with polyethylene terephthalate (PET) as a base material and a surface coated with silicone oil or fluorine release agent, which is mainly used for protecting adhesive materials from sticking during transportation, storage and processing. Through low surface energy, the adhesive layer can be easily peeled off after contact without residue. On this basis, the optical-grade PET release film needs to meet higher standards. Such a film is mainly used in high-end display fields and is the core material of the OCA optical adhesive protection process. However, the traditional optical-grade PET release film has the problem of easy tearing in die cutting processing and insufficient mechanical properties under the demand of ultra-thinning.

[0003] Nanocellulose is a one-dimensional nanomaterial extracted from natural cellulose, which has the characteristics of lightweight, high strength, high light transmission and biodegradability, and is often used to enhance the performance of composite materials. The preparation method of a cellulose nanometer paper-based MLCC release film is disclosed in Chinese Patent No. CN116926980B, which confirms the effectiveness of nanocellulose in improving the mechanical support and wettability of the release film.

[0004] However, there are still key problems in the application of nanocellulose in OCA release film: the surface of the molecular chain is rich in hydroxyl groups, which can easily form spontaneous aggregation through hydrogen bonds, leading to uneven dispersion in the PET matrix. Aggregated nanocellulose can strongly scatter light, resulting in a decrease in the light transmittance of the release film and an increase in the haze, which cannot meet the stringent requirements of optical-grade products. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a nanocellulose-reinforced optical-grade PET release film, which effectively inhibits the aggregation of nanocellulose by multiple modifications such as cerium / zinc double doping, MOF structure coating and aniline-o-aminobenzoic acid copolymerization, significantly improves the compatibility of nanocellulose with PET, and makes the PET release film have excellent mechanical properties, optical transparency and micro-region repair ability, which can meet the stringent requirements of OCA optical adhesive protection materials in high-end display fields.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A preparation method of a nanocellulose-reinforced optical-grade PET release film, comprising the following steps:

[0008] Step one: by in-situ synthesis, a cerium / zinc double metal MOF is synthesized on the nanocellulose to obtain double metal MOF composite nanocellulose.

[0009] Step 2: The bimetallic MOF composite nanocellulose is then coated with a copolymer of aniline and o-aminobenzoic acid to obtain modified nanocellulose.

[0010] Step 3: melt-blending the modified nanocellulose, PET sheet and epoxy chain extender, and forming the PET base film layer by extrusion.

[0011] Step 4: Prepare a release layer slurry, apply it on the surface of the pretreated PET base film layer, and sequentially dry, photocuring and ripen to obtain a nanocellulose reinforced optical grade PET release film.

[0012] Furthermore, the specific preparation steps of modified nanocellulose are as follows:

[0013] Bimetallic MOF composite nanocellulose, aniline, o-aminobenzoic acid and 1M hydrochloric acid were added to a reactor and stirred to allow uniform adsorption of aniline. Ammonium persulfate was then added to the reactor and reacted at 0°C for 8 hours. Acetone was added to terminate the reaction, and the mixture was acid-washed 3-5 times with a 0.1 mol / L hydrochloric acid solution and then washed with distilled water until neutral to obtain modified nanocellulose.

[0014] Furthermore, the usage ratio of the bimetallic MOF composite nanocellulose, aniline, o-aminobenzoic acid, hydrochloric acid, ammonium persulfate and acetone is 5-7 g: 2.5-3.5 g: 0.12-0.18 g: 40-60 mL: 0.6-0.8 g: 10-40 mL.

[0015] Furthermore, the specific preparation steps of bimetallic MOF composite nanocellulose are as follows:

[0016] The cerium / zinc dual-doped nanocellulose slurry was added to the reactor and ultrasonically dispersed for 20-30 minutes. Then, a mixed solution of 2-methylimidazole, sodium acetate and deionized water was added to the reactor and ultrasonically dispersed for 20-30 minutes. The mixture was allowed to react at 85-90°C for 12-16 hours and vacuum filtered. The precipitate was washed three times with methanol and vacuum dried at 90-100°C under nitrogen protection for 10-12 hours to obtain bimetallic MOF composite nanocellulose.

[0017] Furthermore, the usage ratio of the cerium / zinc dual-doped nanocellulose slurry, 2-methylimidazole, sodium acetate and deionized water is 2.5-4L: 1.5-3g: 0.2-0.5g: 80-120mL.

[0018] Furthermore, the specific preparation steps of the cerium / zinc dual-doped nanocellulose slurry are as follows:

[0019] Cerium nitrate, zinc nitrate, hexafluoroisopropanol and deionized water are stirred at 40-50°C, 300-400 r / min and nitrogen protection for 5-8 minutes, and added into a ball mill together with cellulose for grinding at 1000-1500 r / min for 2-3 hours. The ball-milled product is diluted with water to a solid content of 0.1-0.3wt% to obtain a cerium / zinc dual-doped nanocellulose slurry.

[0020] Furthermore, the usage ratio of cerium nitrate, zinc nitrate, hexafluoroisopropanol, deionized water and cellulose is 0.5-0.8 g: 0.8-1.2 g: 80-100 mL: 400-420 mL: 8-10 g.

[0021] Furthermore, the light curing is UV double-sided curing, and the specific processing steps are:

[0022] At a wavelength of 365nm and an irradiation dose of 400-500mJ / cm 3 Under ultraviolet light, the PET base film coated with the release layer slurry is double-sided cured for 15-25s. Before UV curing, the PET base film coated with the release layer slurry needs to be hot air dried at 80-100℃ for 2-3min, and after UV curing, it needs to be matured at 35-40℃ for 20-24h.

[0023] Beneficial effects of the present invention:

[0024] 1. In the present invention, the agglomeration problem of the modified nanocellulose is solved and its own high light transmittance is retained. At the same time, the uniform coating of MOF and copolymer network does not significantly affect the light transmission path, which helps to maintain the high optical transparency of the release film and meet the transmittance and low haze requirements of optical-grade PET release film.

[0025] 2. In the present invention, cerium-zinc bimetallic MOF-coated nanocellulose is introduced into a PET optical release film. On the one hand, nanocellulose itself has the characteristics of high strength, high modulus and high aspect ratio, and can be used as a high-efficiency mechanical reinforcement unit in the PET matrix, effectively bearing external loads, and greatly improving the tensile strength and puncture resistance of the PET film. On the other hand, the bimetallic MOF coating layer and the nanocellulose form a rigid-flexible composite structure. The rigid framework of the MOF can limit the excessive deformation of the nanocellulose, and the flexible characteristics of the nanocellulose can buffer external impacts. The two work together to further improve the toughness and dimensional stability of the film, and reduce the thermal shrinkage and warping of the PET film during processing and use.

[0026] 3. The present invention provides multiple functions for the PET optical release film through the synergy of metal elements and substrate properties: in terms of UV resistance, the cerium element in the coating structure has excellent UV shielding ability, which can efficiently absorb UV-A / UV-B ultraviolet rays, preventing the molecular chain degradation caused by direct ultraviolet radiation of nanocellulose; in terms of antistatic and antibacterial properties, the zinc element imparts antistatic and antibacterial properties, reducing static electricity accumulation and dust adsorption. In addition, nanocellulose itself has good ionic conductivity, which can cooperate with the cerium and zinc metal sites in MOF to construct a continuous conductive network, further enhancing the antistatic effect.

[0027] 4. The present invention uses aniline and o-aminobenzoic acid to copolymerize to form a three-dimensional network to encapsulate bimetallic MOF composite nanocellulose. The side chain carboxyl group introduced into the copolymer network can react with the hydroxyl group at the end of PET, greatly improving the compatibility of the modified nanocellulose and the PET base layer; the epoxy group at one end of the added epoxy chain extender reacts with the hydroxyl and carboxyl groups at the end of the PET molecular chain, which can extend the molecular chain and improve the melt viscosity and mechanical properties of the PET matrix. The epoxy group at the other end reacts with the carboxyl group of the copolymer network on the surface of the modified nanocellulose, further strengthening the chemical bonding between the two. The two work together to reduce the agglomeration of nanocellulose through multiple interfacial reactions, enhance the interfacial bonding strength of the composite material, and enable the PET base film to maintain high optical transparency while significantly improving the mechanical properties. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1: A nanocellulose-reinforced optical-grade PET release film and its preparation method,

[0030] S1: 0.5 g of cerium nitrate, 0.8 g of zinc nitrate, 80 mL of the cosolvent hexafluoroisopropanol, and 400 mL of deionized water were added to a reactor and stirred at 40°C, 300 rpm, and nitrogen for 5 min until the solution became transparent, yielding a zinc-cerium mixed solution. 8 g of cellulose was ground in a planetary ball mill containing 10 mm diameter agate balls. 50 mL of the zinc-cerium mixed solution and 30 mL of water were added and ball-milled at 1000 rpm for 2 h. The milled product was diluted with water to a solid content of 0.1 wt% to yield a cerium / zinc co-doped nanocellulose slurry.

[0031] Hexafluoroisopropanol can dissolve cerium nitrate and zinc nitrate at the same time to avoid metal ion precipitation; during the ball milling process, Zn 2+With Ce 3+ Together they form Zn-OC and Ce-OC coordination bonds with cellulose hydroxyl groups and bind to the surface of nanocellulose.

[0032] S2: Add 2.5L of cerium / zinc dual-doped nanocellulose slurry into the reactor and ultrasonically disperse it for 20 minutes. Then add a mixed solution of 1.5g of 2-methylimidazole, 0.2g of sodium acetate and 80mL of deionized water into the reactor and ultrasonically disperse it for 20 minutes. Let it stand at 85°C for 12 hours, vacuum filter it, and wash the precipitate with methanol three times. Vacuum dry it at 90°C under nitrogen protection for 10 hours to obtain bimetallic MOF composite nanocellulose.

[0033] The Zn in the cerium / zinc dual-doped nanocellulose pulp has been bound to the nanocellulose surface through coordination bonds. 2+ As the metal center, the nanocellulose was first dispersed evenly by ultrasonic dispersion, and then a mixed solution containing 2-methylimidazole as a ligand and sodium acetate was added to adjust the system to a weak alkaline state to promote coordination and ultrasonication was performed to allow the ligand to bind to Zn 2+ Fully contact, then stand at 85-90℃ to react, let Zn 2+ The MOF structure was formed by in-situ coordination with 2-methylimidazole. After washing with methanol to remove unreacted substances and vacuum drying, a bimetallic MOF composite nanocellulose with MOF coated on the surface was obtained. 3+ It is retained on the surface of nanocellulose through coordination bonds.

[0034] S3: 5 g of bimetallic MOF composite nanocellulose, 2.5 g of aniline, 0.12 g of o-aminobenzoic acid and 40 mL of 1 M hydrochloric acid were added to the reactor and stirred at 0°C and 300 r / min for 2 h to allow the aniline to be evenly adsorbed. Subsequently, 0.6 g of ammonium persulfate as an initiator was added to the reactor and reacted at 0°C for 8 h. 10 mL of acetone was added to terminate the reaction. The product was pickled three times with a 0.1 mol / L hydrochloric acid solution to remove unreacted aniline, and then washed with distilled water until neutral to remove electrolyte by-products to obtain modified nanocellulose.

[0035] Aniline is adsorbed on the hydrophobic channels of MOF and the surface of nanocellulose through π-π stacking and electrostatic interaction. The benzene ring of anthranilic acid forms π-π conjugation with aniline, laying the foundation for copolymerization. Subsequently, the addition of ammonium persulfate triggers the copolymerization of the two under acidic conditions. Ce 3+ The redox activity of cellulose nanoparticles promotes the directional polymerization of aniline, and the three-dimensional network of nanocellulose restricts the disordered growth of polymer chains, so that the copolymer is tightly coated on its surface through Zn-N coordination bonds and hydrogen bonds.

[0036] S4: 25 g of PET sheet, 5 g of modified nanocellulose, 0.05 g of chain extender 6059, 0.2 g of glyceryl stearate as a lubricant, and 0.07 g of antioxidant 1010 were added to a twin-screw extruder, conveyed by the screw, and the temperature in the conveying zone was controlled at 160°C. After being conveyed to the heating zone, it was melted at 200°C and sheared under the conditions of a screw speed of 150 r / min and a head pressure of 3 MPa. After the melt was extruded through a mold, it was cooled at 15°C to obtain a PET base film layer.

[0037] The heating zone melts the PET. At this time, the epoxy group at one end of the chain extender 6059 reacts with the hydroxyl / carboxyl groups at the end of the PET molecular chain, extending the molecular chain to improve the melt viscosity and mechanical properties. At the same time, the epoxy group at the other end of the chain extender 6059 reacts with the carboxyl groups of the copolymer network on the surface of the modified nanocellulose, significantly improving the compatibility with the PET matrix and preventing agglomeration.

[0038] S5: 48 g of UV-curable methacrylate side-group polymethylsiloxane was put into a reactor, 30 mL of anhydrous ethanol was added, and the mixture was stirred at 300 r / min and 60°C for 10 min. Then, 65 mL of deionized water was added dropwise and the stirring was continued for 10 min. 0.5 g of polythiophene was added, and the mixture was ultrasonicated at 20°C and 200 W for 8 min. The mixture was cooled to 40°C and 1 g of photoinitiator TPO was added. The mixture was stirred in the dark for 10 min, and vacuum defoamed for 30 min. The mixture was allowed to stand to obtain a release layer slurry.

[0039] S6: The release layer slurry was coated on the PET base film, and hot air dried at 80 ° C for 2 minutes to remove the solvent, and then irradiated at a wavelength of 365 nm and a dose of 400 mJ / cm 3 The film was double-sided UV cured for 15 seconds under the conditions of 37°C and matured at 35°C for 20 hours. The thickness of the release layer was controlled to be 5 μm to obtain a nanocellulose reinforced optical grade PET release film.

[0040] Example 2: A nanocellulose-reinforced optical-grade PET release film and its preparation method,

[0041] S1: 0.7 g of cerium nitrate, 1 g of zinc nitrate, 90 mL of cosolvent hexafluoroisopropanol, and 410 mL of deionized water were added to a reactor and stirred at 45°C, 350 rpm, and nitrogen for 7 min until the solution became transparent, yielding a zinc-cerium mixed solution. 9 g of cellulose was ground in a planetary ball mill containing 10 mm diameter agate balls. 60 mL of the zinc-cerium mixed solution and 40 mL of water were added and ball-milled at 1200 rpm for 2.5 h. The milled product was diluted with water to a solid content of 0.2 wt% to yield a cerium / zinc co-doped nanocellulose slurry.

[0042] S2: 3L of cerium / zinc dual-doped nanocellulose slurry was added to the reactor and ultrasonically dispersed for 25 minutes. Then, a mixed solution of 2g of 2-methylimidazole, 0.4g of sodium acetate and 100mL of deionized water was added to the reactor and ultrasonically dispersed for 25 minutes. The mixture was allowed to react at 88°C for 14 hours, vacuum filtered, and the precipitate was washed three times with methanol. It was vacuum dried at 95°C under nitrogen protection for 11 hours to obtain bimetallic MOF composite nanocellulose.

[0043] S3: 6 g of bimetallic MOF composite nanocellulose, 3 g of aniline, 0.15 g of o-aminobenzoic acid and 50 mL of 1 M hydrochloric acid were added to the reactor and stirred at 0°C and 400 r / min for 2.5 h to allow the aniline to be evenly adsorbed. Subsequently, 0.7 g of ammonium persulfate as an initiator was added to the reactor and reacted at 0°C for 10 h. 25 mL of acetone was added to terminate the reaction. The product was pickled four times with a 0.1 mol / L hydrochloric acid solution to remove unreacted aniline, and then washed with distilled water until neutral to remove electrolyte by-products to obtain modified nanocellulose.

[0044] S4: 40 g of PET sheet, 8 g of modified nanocellulose, 0.25 g of chain extender 6059, 0.35 g of glyceryl stearate as a lubricant, and 0.11 g of antioxidant 1010 were added to a twin-screw extruder, conveyed by a screw, and the temperature in the conveying zone was controlled at 170°C. After being conveyed to the heating zone, it was melted at 210°C and sheared under the conditions of a screw speed of 170 r / min and a head pressure of 3 MPa. After the melt was extruded through a die, it was cooled at 15°C to obtain a PET base film layer.

[0045] S5: 49 g of UV-curable methacrylate side-group polymethylsiloxane was put into a reactor, 32 mL of anhydrous ethanol was added, and the mixture was stirred at 400 r / min and 62 °C for 12 min. Then, 68 mL of deionized water was added dropwise and the stirring was continued for 10 min. 0.65 g of polythiophene was added, and the mixture was ultrasonicated at 23 °C and 250 W for 9 min. After cooling to 42 °C, 1.2 g of photoinitiator TPO was added. The mixture was stirred in the dark for 13 min, and vacuum defoamed for 35 min. The mixture was allowed to stand to obtain a release layer slurry.

[0046] S6: The release layer slurry was coated on the PET base film, and hot air dried at 90 ° C for 2.5 minutes to remove the solvent, and then irradiated at a wavelength of 365 nm and a dose of 450 mJ / cm 3 The film was double-sided UV cured for 20 seconds under the conditions of 37°C and matured at 35°C for 22 hours. The thickness of the release layer was controlled to be 6 μm to obtain a nanocellulose reinforced optical grade PET release film.

[0047] Example 3: A nanocellulose-reinforced optical-grade PET release film and its preparation method,

[0048] S1: 0.8 g of cerium nitrate, 1.2 g of zinc nitrate, 100 mL of the cosolvent hexafluoroisopropanol, and 420 mL of deionized water were added to a reactor and stirred at 50°C, 400 rpm, and nitrogen for 8 min until the solution became transparent, yielding a zinc-cerium mixed solution. 10 g of cellulose was ground in a planetary ball mill containing 10 mm diameter agate balls. 70 mL of the zinc-cerium mixed solution and 50 mL of water were added and ball-milled at 1500 rpm for 3 h. The milled product was diluted with water to a solid content of 0.3 wt% to yield a cerium / zinc co-doped nanocellulose slurry.

[0049] S2: 4L of cerium / zinc dual-doped nanocellulose slurry was added to the reactor and ultrasonically dispersed for 30 minutes. Then, a mixed solution of 3g of 2-methylimidazole, 0.5g of sodium acetate and 120mL of deionized water was added to the reactor and ultrasonically dispersed for 30 minutes. The mixture was allowed to react at 90°C for 16 hours, vacuum filtered, and the precipitate was washed three times with methanol. It was vacuum dried at 100°C under nitrogen protection for 12 hours to obtain bimetallic MOF composite nanocellulose.

[0050] S3: 7g of bimetallic MOF composite nanocellulose, 3.5g of aniline, 0.18g of o-aminobenzoic acid and 60mL of 1M hydrochloric acid were added to the reactor and stirred at 0℃ and 500r / min for 3h to uniformly adsorb the aniline. Subsequently, 0.8g of ammonium persulfate as an initiator was added to the reactor and reacted at 0℃ for 12h. 40mL of acetone was added to terminate the reaction. The product was pickled five times with a 0.1mol / L hydrochloric acid solution to remove unreacted aniline. The product was then washed with distilled water until neutral to remove electrolyte by-products to obtain modified nanocellulose.

[0051] S4: 55 g of PET sheet, 5-10 g of modified nanocellulose, 0.55 g of chain extender 6059, 0.5 g of glyceryl stearate as a lubricant, and 0.15 g of antioxidant 1010 were added to a twin-screw extruder, conveyed by the screw, and the temperature in the conveying zone was controlled at 180°C. After being conveyed to the heating zone, it was melted at 220°C and sheared under the conditions of a screw speed of 200 r / min and a head pressure of 3 MPa. After being extruded through a die, the melt was cooled at 15°C to form a PET base film layer.

[0052] S5: Add 50g of UV-curable methacrylate side-group polymethylsiloxane into a reactor, add 35mL of anhydrous ethanol, stir at 500r / min and 65℃ for 15min, then dropwise add 70mL of deionized water and continue stirring for 10min, add 0.8g of polythiophene, ultrasonicate at 25℃ and 300W for 10min, cool to 45℃, add 1.5g of photoinitiator TPO, stir in the dark for 15min, defoam in vacuum for 40min, and let stand to obtain a release layer slurry.

[0053] S6: The release layer slurry was coated on the PET base film, and hot air dried at 100 ° C for 3 minutes to remove the solvent, and then irradiated at a wavelength of 365 nm and a dose of 500 mJ / cm 3 UV double-sided curing was performed for 25 seconds under the conditions of 40°C and aging was performed for 24 hours at 40°C. The thickness of the release layer was controlled to be 8 μm to obtain a nanocellulose reinforced optical grade PET release film.

[0054] In the present invention, polyethylene terephthalate (PET) was purchased from Dongguan Minghui Plastic Co., Ltd. with a specification of CZ-302; the cellulose raw material was corn cob cellulose, which was purchased from Jinan Shengquan Group Co., Ltd.; hexafluoroisopropanol, cerium nitrate, zinc nitrate and 2-methylimidazole were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; aniline, o-aminobenzoic acid and photoinitiator TPO were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; o-aminobenzoic acid was purchased from; chain extender 6059 was purchased from Jining Tangyi Chemical Co., Ltd.; and the planetary ball mill was from Tianjin Dongfang Tianjing Technology Co., Ltd. with a model of TJX-4100.

[0055] Comparative Example 1: Based on Example 3, without going through steps S1 to S3, the modified nanocellulose in step S4 is replaced with unmodified nanocellulose, and the other steps remain unchanged to obtain a nanocellulose-reinforced optical-grade PET release film.

[0056] Comparative Example 2: Based on Example 3, without going through the step of in situ growth of MOF in step S2, the cerium / zinc dual-doped nanocellulose was directly coated with aniline-o-aminobenzoic acid copolymer, and then melt-blended with PET, a chain extender, etc. to form a film. The other steps remained unchanged to obtain a nanocellulose-reinforced optical-grade PET release film.

[0057] Comparative Example 3: Based on Example 3, the copolymerization coating treatment of aniline and anthranilic acid in step S3 was omitted, and the other steps remained unchanged to obtain a nanocellulose reinforced optical grade PET release film.

[0058] Comparative Example 4: Based on Example 3, the chain extender 6059 was not added in step S4, and the other steps remained unchanged to obtain a nanocellulose reinforced optical grade PET release film.

[0059] Performance tests were conducted on the optical-grade PET release films prepared in Examples 1-3 and Comparative Examples 1-4. The tensile strength and elongation at break were measured according to the test methods specified in GB / T1040.3-2006. Higher tensile strength and elongation at break indicate better mechanical properties. Light transmittance and haze were measured according to the test methods specified in GB / T2410-2008. Peel force was measured according to GB / T2792-2014, using a peel tester to test the 180° peel force between the release film and the OCA optical adhesive. Surface resistivity was measured according to GB / T1410-2006. Lower surface resistivity indicates faster charge dissipation and stronger antistatic properties. The test results are shown in Table 1.

[0060] Table 1 Performance test results of optical grade PET release film

[0061]

[0062] As can be seen from Table 1, Examples 1 to 3 achieve gradually improved comprehensive performance of optical-grade PET release films due to multiple modifications of nanocellulose and the addition of chain extenders. With the increase in the amount of cerium nitrate and zinc nitrate, the extension of the ball milling time, and the increase in MOF reaction temperature and time, the modified nanocellulose is more evenly dispersed in the PET matrix, the interfacial bonding force is significantly enhanced, and the tensile strength and elongation at break are both improved; at the same time, the MOF coating density and the copolymerization network uniformity are improved with parameter optimization, without hindering the light transmission path, and the metal ions and MOF synergistically inhibit the agglomeration of nanocellulose, and the transmittance and haze meet the optical-grade requirements; the increase in zinc content and the improvement of the MOF conductive network reduce the surface resistance, effectively reduce the adsorption of electrostatic dust, and ensure the cleanliness of the OCA optical adhesive.

[0063] In Comparative Example 1, since the nanocellulose has not undergone a series of key modification steps such as cerium / zinc doping, MOF coating, and copolymerization of aniline and o-aminobenzoic acid, the nanocellulose is severely aggregated in the PET matrix. The agglomerated nanocellulose will strongly scatter light, resulting in a decrease in light transmittance and an increase in haze. At the same time, there is a lack of effective chemical bonding between the unmodified nanocellulose and the PET matrix, and the interface compatibility is poor, which significantly reduces the overall mechanical strength and durability of the material. In addition, the peel force is also increased due to the increase in interface defects, and the lack of an antistatic mechanism leads to an increase in surface resistance and severe static electricity accumulation.

[0064] In Comparative Example 2, due to the lack of in-situ growth of MOF, the rigid framework of MOF is missing, and it is impossible to form a rigid-flexible composite structure with nanocellulose, resulting in a decrease in load transfer efficiency, a decrease in tensile strength and elongation at break, and a weakening of the membrane's deformation resistance. At the same time, due to the disappearance of the hydrophobic isolation effect of MOF, some nanocelluloses undergo weak aggregation through surface hydroxyl groups, increasing light scattering, resulting in increased haze, decreased transmittance, and impaired optical transparency. In addition, due to the lack of MOF porous structure, it is impossible to anchor Zn 2 +It causes uneven dispersion in the system, incomplete conductive network, and significantly weakened antistatic effect.

[0065] In Comparative Example 3, the cellulose nanofiber was not subjected to copolymerization and coating treatment with aniline and o-aminobenzoic acid, but only to cerium / zinc doping and MOF coating. Therefore, carboxyl side chains could not be introduced on the surface of the nanocellulose, resulting in insufficient interfacial bonding with PET, causing the tensile strength and elongation at break of the release film to be lower than those in the embodiment. The haze also increased due to the loose interfacial bonding, which would increase the scattering of light at the interface between the two phases, and the optical performance deviated from the optical grade standard. In addition, due to defects in the interface, the coating flatness of the release layer on the surface of the PET base film decreased, and the release stability was insufficient.

[0066] In Comparative Example 4, since no chain extender 6059 was added, it could neither react with the hydroxyl / carboxyl groups at the ends of the PET molecular chains to extend the molecular chains and improve the melt viscosity and mechanical properties of the PET matrix itself, nor could it react with the carboxyl groups of the modified nanocellulose surface copolymer network through the epoxy groups at the other end to strengthen the chemical bonding between the two. Therefore, the molecular weight of the PET matrix was not effectively improved, and the interfacial bonding force between the modified nanocellulose and the PET matrix was also weakened, resulting in the mechanical strength of the release film being lower than that of the examples. However, since the agglomeration problem of the nanocellulose had been solved through the early modification, its transmittance and haze were less affected and were not much different from those of the examples.

[0067] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0068] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a nanocellulose-reinforced optical-grade PET release film, the method comprising: A release layer slurry is coated on one side of a PET base film, and then a light curing treatment is performed. The PET base film is prepared by the following steps: Step 1: Synthesize cerium / zinc bimetallic MOF on nanocellulose by in situ synthesis to obtain bimetallic MOF composite nanocellulose; Step 2: The bimetallic MOF composite nanocellulose is then coated with a copolymer of aniline and anthranilic acid to obtain modified nanocellulose; Step 3: melt-blending the modified nanocellulose, PET sheet and epoxy chain extender, and forming the PET base film layer by extrusion.

2. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 1, wherein: The specific preparation steps of the modified nanocellulose are as follows: Bimetallic MOF composite nanocellulose, aniline, o-aminobenzoic acid and 1M hydrochloric acid were added to a reactor and stirred to allow uniform adsorption of aniline. Ammonium persulfate was then added to the reactor and reacted at 0°C for 8 hours. Acetone was added to terminate the reaction, and the mixture was acid-washed 3-5 times with a 0.1 mol / L hydrochloric acid solution and then washed with distilled water until neutral to obtain modified nanocellulose.

3. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 2, wherein: The usage ratio of the bimetallic MOF composite nanocellulose, aniline, o-aminobenzoic acid, hydrochloric acid, ammonium persulfate and acetone is 5-7 g: 2.5-3.5 g: 0.12-0.18 g: 40-60 mL: 0.6-0.8 g: 10-40 mL.

4. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 2, wherein: The specific preparation steps of the bimetallic MOF composite nanocellulose are as follows: The cerium / zinc dual-doped nanocellulose slurry was added to the reactor and ultrasonically dispersed for 20-30 minutes. Then, a mixed solution of 2-methylimidazole, sodium acetate and deionized water was added to the reactor and ultrasonically dispersed for 20-30 minutes. The mixture was allowed to react at 85-90°C for 12-16 hours, vacuum filtered, and the precipitate was washed with methanol three times. The mixture was vacuum dried at 90-100°C under nitrogen protection for 10-12 hours to obtain bimetallic MOF composite nanocellulose.

5. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 4, wherein: The usage ratio of the cerium / zinc dual-doped nanocellulose slurry, 2-methylimidazole, sodium acetate and deionized water is 2.5-4L:1.5-3g:0.2-0.5g:80-120mL.

6. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 4, wherein: The specific preparation steps of the cerium / zinc dual-doped nanocellulose slurry are as follows: Cerium nitrate, zinc nitrate, hexafluoroisopropanol and deionized water were stirred and mixed under nitrogen protection, and then added into a ball mill together with cellulose, and ball-milled at 1000-1500 r / min for 2-3 hours. The ball-milled product was diluted with water to a solid content of 0.1-0.3wt% to obtain a cerium / zinc dual-doped nanocellulose slurry.

7. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 6, wherein: The usage ratio of the cerium nitrate, zinc nitrate, hexafluoroisopropanol, deionized water and cellulose is 0.5-0.8 g: 0.8-1.2 g: 80-100 mL: 400-420 mL: 8-10 g.

8. The method for preparing a nanocellulose-enhanced optical-grade PET release film according to claim 1, wherein: The steps of the light curing process are as follows: The wavelength is 365nm and the irradiation dose is 400-500mJ / cm 3 Under ultraviolet light, the PET base film coated with the release layer slurry is double-sided cured for 15-25 seconds.

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