A toughened modified PEN polyester film and a method for preparing the same
By introducing a third monomer copolymer and toughening masterbatch into PEN film, the molecular structure and material properties are optimized, solving the problem of insufficient flexibility of PEN film and achieving a combination of high strength and high flexibility at high temperatures. This makes it suitable for high-temperature insulating protective film in the field of battery packaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 四川东方绝缘材料股份有限公司
- Filing Date
- 2026-02-25
- Publication Date
- 2026-06-16
AI Technical Summary
Due to the high rigidity of the molecular chain and limited flexibility, PEN film is prone to problems such as curling and delamination at the folded edges when used as a high-temperature insulating protective film for batteries.
By introducing a third monomer such as propylene glycol, butanediol, neopentyl glycol, or polyethylene glycol into copolymerization, and combining PEN toughening masterbatch and functional masterbatch, the molecular structure and material properties are optimized by using methacrylate-hydroxyethyl methacrylate-epoxypropylene methacrylate copolymer as a bifunctional toughening agent.
The toughened modified PEN film prepared maintains high tensile strength and elongation at break at high temperatures, avoiding the decrease in strength that comes with increased flexibility in traditional modification methods, and meeting the application requirements of high-temperature resistant insulating protective films in the battery packaging field.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials technology, specifically a toughened modified PEN polyester film and its preparation method. Background Technology
[0002] Polyethylene naphthalate (PEN) is a thermoplastic high-performance polyester material with a chemical structure similar to polyethylene terephthalate (PET). However, the naphthalene ring structure in PEN has a greater degree of conjugation than the benzene ring structure in PET, resulting in a more rigid molecular chain. Compared to PET, PEN exhibits superior mechanical properties, insulation, heat resistance, weather resistance, chemical stability, and barrier properties, making it a viable alternative to PET in engineering plastics, fibers, and high-performance films.
[0003] PEN material can be prepared into thin films using a biaxial stretching process. It possesses characteristics such as high strength, heat resistance, dimensional stability, weather resistance, and corrosion resistance, making it widely used in sound diaphragm materials, motor insulation, flexible printed circuit boards, and liquid crystal polarizing protective films, especially in battery packaging. However, BOPEN films suffer from high molecular chain rigidity and limited flexibility. When used as high-temperature insulating protective films for batteries, they are prone to warping and delamination at the folded edges, limiting their application. Summary of the Invention
[0004] The purpose of this invention is to provide a toughened modified PEN polyester film and its preparation method, aiming to solve the problems of peeling and delamination at the folded edges when existing PEN films are used as high-temperature insulating protective films for batteries due to their high molecular chain rigidity and limited flexibility.
[0005] The objective of this invention is achieved through the following technical solution: A toughened modified PEN polyester film, comprising the following components by weight: 57~88.5 parts modified PEN resin, 5~20 parts PEN toughening masterbatch, 1.5~3 parts opening agent, 5~20 parts functional masterbatch; The modified PEN resin is copolymerized from dimethyl 2,6-naphthalenedicarboxylate and a diol; the diol It is a mixture of ethylene glycol and other diols, wherein the other diols are selected from propylene glycol, butanediol, neopentyl glycol, and polyethylene glycol; The PEN toughening masterbatch is formed by blending and modifying PEN resin with bifunctional toughening agent methacrylate-hydroxyethyl methacrylate-glycidyl methacrylate copolymer; The functional masterbatch is composed of modified PEN polyester, nucleating agent, antioxidant and colorant.
[0006] As an embodiment of this application, the molar ratio of ethylene glycol to other diols is 7:3 to 2:8.
[0007] As an embodiment of this application, the opening agent is a modified PEN masterbatch of micron-sized silica.
[0008] As an embodiment of this application, the nucleating agent is selected from sodium benzoate and surlyn.
[0009] As an embodiment of this application, the antioxidant masterbatch is selected from antioxidant 1010 and antioxidant 168.
[0010] As an embodiment of this application, the colorant is selected from titanium masterbatch and carbon black masterbatch.
[0011] As an embodiment of this application, the thickness of the toughened modified PEN polyester film is 25-200 micrometers.
[0012] In addition, to achieve the above objectives, this application also provides a method for preparing a toughened modified PEN polyester film, comprising the following steps: S1. Preparation of modified PEN polyester: 1 mol of dimethyl 2,6-naphthalenedicarboxylate, 2.0-2.5 mol of diol, and 0.0002-0.0004 mol of transesterification catalyst were added to a reactor. The reaction temperature was raised to 180-200℃. When the methanol distillation rate reached the theoretical 96-98%, 0.0003-0.0004 mol of polycondensation catalyst and 0.0001-0.0004 mol of heat stabilizer were added. The temperature was raised to 280-290℃, and a vacuum was slowly drawn until the reactor pressure reached 20-40 Pa for polycondensation reaction. The reaction time was 5-7 hours. After purging with nitrogen, the product was discharged to obtain modified PEN resin. Preparation of S2, PEN toughening masterbatch, opening agent, and functional masterbatch: 60-90 parts of PEN resin and 10-40 parts of methacrylate-hydroxyethyl methacrylate-glycidyl methacrylate copolymer were melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain PEN toughening masterbatch. 95-99 parts of PEN resin and 1-5 parts of micron-sized silica are melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain an opening agent. 45-82.5 parts of modified PEN polyester, 2.5-5 parts of nucleating agent, 5-10 parts of antioxidant masterbatch, and 10-40 parts of colorant are melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain functional masterbatch. S3. Preparation of toughened modified PEN polyester film: After the modified PEN polyester, PEN toughening masterbatch, opening agent and functional masterbatch are blended and dried, they are sent from the silo to a single screw extruder, and toughened modified PEN polyester film is obtained through melt extrusion, cooling casting, longitudinal stretching, transverse stretching, heat setting, corona treatment and traction winding.
[0013] As an embodiment of this application, the transesterification catalyst is selected from anhydrous zinc acetate.
[0014] As an embodiment of this application, the polycondensation catalyst is selected from antimony trioxide (Sb2O3).
[0015] As an embodiment of this application, the stabilizer is selected from trimethyl phosphate and triphenyl phosphate.
[0016] As an implementation method of this application, the relevant parameters in step S2 are as follows: drying temperature is 160~165℃, time is 2~3h; extruder melt extrusion temperature is 275~285℃, cooling casting temperature is 20-35℃; longitudinal stretching temperature is 110~130℃, longitudinal stretching ratio is 2.8~3.3; transverse stretching temperature is 135~155℃, stretching ratio is 3.0~3.5; heat setting temperature is 230~250℃, and corona treatment can be single-sided or double-sided.
[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention optimizes PEN performance from both molecular structure and material synergy aspects through a combined modification approach of "third monomer copolymerization + bifunctional toughening masterbatch": a third monomer such as propylene glycol, butanediol, neopentyl glycol, or polyethylene glycol is introduced to participate in copolymerization, introducing flexible segments into the PEN molecular backbone while breaking the regularity of the molecular chain, thus fundamentally alleviating the brittleness problem of PEN; the accompanying PEN toughening masterbatch uses a bifunctional toughening agent, specifically a copolymer of methacrylate-hydroxyethyl methacrylate-glycidyl methacrylate, where the flexible segments can help absorb external forces and improve the material's deformation capacity, while the reactive groups can form a stable bond with the PEN resin, reducing the risk of interfacial separation. Experimental results show that the films prepared using this method maintain high levels of tensile strength (MD direction ≥216MPa, TD direction ≥239MPa) and elongation at break (MD direction ≥96%, TD direction ≥102%). This avoids the situation where "increased flexibility is accompanied by decreased strength" in traditional modification methods, and is fully compatible with the application requirements of high-temperature resistant insulating protective films for edge crack resistance and puncture resistance in the battery packaging field. Detailed Implementation
[0018] Example 1 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: 1 mol of dimethyl 2,6-naphthalenedicarboxylate, 1.6 mol of ethylene glycol, 0.4 mol of propylene glycol, and 0.0004 mol of anhydrous zinc acetate were added to a reactor. The reaction temperature was raised to 200℃. When the methanol distillation reached the theoretical 96%, 0.0003 mol of antimony trioxide and 0.0004 mol of triphenyl phosphate were added. The temperature was raised to 280℃, and a vacuum was slowly drawn until the reactor pressure reached 30 Pa for polycondensation reaction. The reaction time was 6.5 h. After nitrogen gas was introduced, the product was discharged to obtain modified PEN resin.
[0019] Preparation of S2.PEN toughening masterbatch, opening agent, and functional masterbatch: 60 parts of PEN resin and 40 parts of methacrylate-hydroxyethyl methacrylate-epoxypropylene methacrylate copolymer were melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain PEN toughening masterbatch.
[0020] 98 parts of PEN resin and 2 parts of micron-sized silica were melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain an opening agent.
[0021] 55 parts of modified PEN polyester, 5 parts of nucleating agent, 10 parts of antioxidant masterbatch, and 30 parts of colorant were melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain functional masterbatch.
[0022] S3. Preparation of toughened modified PEN polyester film: 62 parts by weight of modified PEN polyester, 15 parts by weight of PEN toughening masterbatch, 3 parts by weight of opening agent, and 20 parts by weight of functional masterbatch were blended and dried at 165°C for 2.5 hours. The mixture was then fed from the silo to a single-screw extruder for melt extrusion at 280°C. After cooling and casting, the film was stretched longitudinally at 120°C with a stretch ratio of 3.0. Then, it was stretched transversely at 145°C with a stretch ratio of 3.2. The film was then heat-set at 240°C, subjected to double-sided corona treatment, and finally drawn and wound to obtain a 50μm toughened modified PEN polyester film.
[0023] Example 2 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Compared with Example 1, "0.4 mol propylene glycol" was replaced with "0.4 mol butanediol".
[0024] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0025] S3. Preparation of toughened modified PEN polyester film: 58 parts by weight of modified PEN polyester, 20 parts by weight of PEN toughening masterbatch, 2 parts by weight of opening agent, and 20 parts by weight of functional masterbatch were dried at 165℃ for 2.5h. The mixture was then fed from the silo to a single-screw extruder for melt extrusion at 280℃. After cooling and casting, the film was dried at 20-35℃. It was then stretched longitudinally at 120℃ with a stretch ratio of 3.0, followed by transverse stretching at 145℃ with a stretch ratio of 3.2. The film was then heat-set at 240℃, subjected to double-sided corona treatment, and finally drawn and wound to obtain a 50μm toughened modified PEN polyester film.
[0026] Example 3 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Compared with Example 1, "0.4 mol propylene glycol" was replaced with "0.4 mol neopentyl glycol".
[0027] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0028] S3. Preparation of toughened modified PEN polyester film: Same as in Example 1.
[0029] Example 4 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Compared with Example 1, "0.4 mol propylene glycol" was replaced with "0.4 mol polyethylene glycol".
[0030] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0031] S3. Preparation of toughened modified PEN polyester film: Same as in Example 1.
[0032] Example 5 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Compared with Example 1, "1.6 mol ethylene glycol and 0.4 mol propylene glycol" is replaced with "1.4 mol ethylene glycol and 0.6 mol polyethylene glycol".
[0033] S2. Preparation of toughened modified PEN polyester film: Same as in Example 1.
[0034] Comparative Example 1 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Compared with Example 1, "1.6 mol ethylene glycol and 0.4 mol propylene glycol" were replaced with "2.0 mol ethylene glycol".
[0035] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0036] S3. Preparation of toughened modified PEN polyester film: Same as in Example 1.
[0037] Comparative Example 2 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Preparation of modified PEN polyester: Same as in Example 1.
[0038] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0039] S3. Preparation of toughened modified PEN polyester film: 77 parts by weight of modified PEN polyester, 3 parts by weight of opening agent, and 20 parts by weight of functional masterbatch were blended and dried at 165°C for 2.5 hours. The mixture was then fed from the silo to a single-screw extruder and melt-extruded at 280°C. The film was then cooled and cast at 20-35°C. It was then stretched longitudinally at 120°C with a stretch ratio of 3.0, followed by transverse stretching at 145°C with a stretch ratio of 3.2. The film was then heat-set at 240°C, subjected to double-sided corona treatment, and finally drawn and wound to obtain a 50μm toughened modified PEN polyester film.
[0040] Comparative Example 3 A method for preparing a toughened modified PEN polyester film includes the following steps: S1. Same as Comparative Example 1.
[0041] S2. Preparation of PEN toughening masterbatch, opening agent, and functional masterbatch: Same as in Example 1.
[0042] S3. Preparation of toughened modified PEN polyester film: Same as comparative example 2.
[0043] The following performance tests were performed on Examples 1-5 and Comparative Examples 1-3 respectively. Mechanical property testing: Refer to the test methods specified in GB / T13542.4-2009; Heat shrinkage performance test: Refer to the test method specified in GB / T11026.3-2006.
[0044] The specific test data is shown in Table 1.
[0045] Table 1: Performance Index of Biaxially Stretched Films from Examples 1-5 and Comparative Examples 1-3 As can be seen from Table 1: Examples 1-5 were prepared strictly according to the process of this invention, resulting in toughened modified PEN polyester films with excellent comprehensive properties: In terms of mechanical properties, the tensile strength in the MD direction of the film is ≥216MPa, and the tensile strength in the TD direction is ≥239MPa, maintaining a high overall tensile strength and ensuring good puncture and tear resistance; simultaneously, the elongation at break in the MD direction is ≥96%, and the elongation at break in the TD direction is ≥102%, which is superior to traditional unmodified PEN films. In terms of thermal stability, the thermal shrinkage rate in the MD direction is ≤0.9%, and the thermal shrinkage rate in the TD direction is ≤0.3%. The low thermal shrinkage characteristics ensure that the film is not prone to dimensional deformation during battery packaging processes (such as high-temperature baking) and long-term use, and can stably adhere to the battery structure.
[0046] In summary, the films prepared in Examples 1-5 possess high flexibility, high mechanical strength, and excellent dimensional stability, perfectly meeting the application requirements of the battery packaging field for high-temperature resistant insulating protective films that are "resistant to edge cracking, puncture-resistant, and dimensionally stable."
[0047] Comparative Example 1 did not use the third monomer copolymerization process of the present invention, but only prepared PEN resin by polymerization of pure ethylene glycol and dimethyl 2,6-naphthalenedicarboxylate. Although the tensile strength of the film prepared by it was maintained at a high level and the flexibility was improved to some extent compared with the unmodified PEN film, it still could not reach the flexibility level of the film in Examples 1-5, and it was difficult to meet the high flexibility requirements of the film when the battery packaging is folded.
[0048] Although Comparative Example 2 used the same third monomer (propylene glycol) copolymerization process as Example 1, it did not add PEN toughening masterbatch. Although the film prepared by it had a certain improvement in flexibility compared to Comparative Example 1, it had a problem of decreased mechanical strength and could not meet the requirements of flexibility and puncture resistance for battery packaging.
[0049] Comparative Example 3 did not use the third monomer copolymerization process of the present invention, nor did it add the PEN toughening masterbatch specified in the present invention. It only prepared conventional PEN resin by polymerizing pure ethylene glycol and dimethyl 2,6-naphthalenedicarboxylate. Although the tensile strength and heat shrinkage properties of the film prepared by it remained at the conventional level, the flexibility was significantly insufficient.
Claims
1. A toughened modified PEN polyester film, characterized in that, Includes the following components by weight: 57~88.5 parts modified PEN resin, 5~20 parts PEN toughening masterbatch, 1.5~3 parts opening agent, 5~20 parts functional masterbatch; The modified PEN resin is copolymerized from dimethyl 2,6-naphthalenedicarboxylate and a diol; the diol It is a mixture of ethylene glycol and other diols, wherein the other diols are selected from propylene glycol, butanediol, neopentyl glycol, and polyethylene glycol; The PEN toughening masterbatch is formed by blending and modifying PEN resin with bifunctional toughening agent methacrylate-hydroxyethyl methacrylate-glycidyl methacrylate copolymer; The functional masterbatch is composed of modified PEN polyester, nucleating agent, antioxidant and colorant.
2. The toughened modified PEN polyester film according to claim 1, characterized in that, The molar ratio of ethylene glycol to other diols is 7:3 to 2:
8.
3. The toughened modified PEN polyester film according to claim 1, characterized in that, The opening agent is a modified PEN masterbatch of micron-sized silica.
4. The toughened modified PEN polyester film according to claim 1, characterized in that, The nucleating agent is selected from sodium benzoate and surlyn.
5. The toughened modified PEN polyester film according to claim 1, characterized in that, The antioxidant masterbatch is selected from antioxidant 1010 and antioxidant 168.
6. The toughened modified PEN polyester film according to claim 1, characterized in that, The colorant is selected from titanium masterbatch and carbon black masterbatch.
7. The method for preparing toughened modified PEN polyester film according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of modified PEN polyester: 1 mol of dimethyl 2,6-naphthalenedicarboxylate, 2.0-2.5 mol of diol, and 0.0002-0.0004 mol of transesterification catalyst were added to a reactor. The reaction temperature was raised to 180-200℃. When the methanol distillation rate reached the theoretical 96-98%, 0.0003-0.0004 mol of polycondensation catalyst and 0.0001-0.0004 mol of heat stabilizer were added. The temperature was raised to 280-290℃, and a vacuum was slowly drawn until the reactor pressure reached 20-40 Pa for polycondensation reaction. The reaction time was 5-7 hours. After purging with nitrogen, the product was discharged to obtain modified PEN resin. Preparation of S2, PEN toughening masterbatch, opening agent, and functional masterbatch: 60-90 parts of PEN resin and 10-40 parts of methacrylate-hydroxyethyl methacrylate-glycidyl methacrylate copolymer were melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain PEN toughening masterbatch. 95-99 parts of PEN resin and 1-5 parts of micron-sized silica are melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain an opening agent. 45-82.5 parts of modified PEN polyester, 2.5-5 parts of nucleating agent, 5-10 parts of antioxidant masterbatch, and 10-40 parts of colorant are melt-extruded and granulated using a twin-screw extruder, and then cooled and pelletized to obtain functional masterbatch. S3. Preparation of toughened modified PEN polyester film: After the modified PEN polyester, PEN toughening masterbatch, opening agent and functional masterbatch are blended and dried, they are sent from the silo to a single screw extruder, and toughened modified PEN polyester film is obtained through melt extrusion, cooling casting, longitudinal stretching, transverse stretching, heat setting, corona treatment and traction winding.
8. The method for preparing the toughened modified PEN polyester film according to claim 7, characterized in that, The transesterification catalyst is selected from anhydrous zinc acetate.
9. The method for preparing the toughened modified PEN polyester film according to claim 7, characterized in that, The polycondensation catalyst is selected from antimony trioxide.
10. The method for preparing the toughened modified PEN polyester film according to claim 7, characterized in that, The stabilizer is selected from trimethyl phosphate and triphenyl phosphate.