A method for producing a pet composite current collector base film with enhanced mechanical properties

Abstract

The application discloses a production method of a PET composite current collector base film with enhanced mechanical properties, and the base film comprises a reinforcing layer, an outer layer, an intermediate core layer and an inner layer; the outer layer is composed of 1,4-cyclohexane dimethanol / isosorbide modified PET and polyetherimide; the intermediate core layer is composed of PET, hexamethylene diisocyanate, an antioxidant, mLLDPE and POE-g-GMA; and the inner layer is composed of microwave irradiation modified PET and natural rubber. The PET composite current collector base film prepared by the method has excellent mechanical properties and good thermal stability.

Description

Technical Field

[0001] This invention relates to the field of PET base film technology, specifically a method for producing a PET composite current collector base film with enhanced mechanical properties. Background Technology

[0002] In the field of PET (polyethylene terephthalate) base film technology, PET base film is widely used in various industries such as packaging, electronics, electrical engineering, and construction due to its excellent physical properties, chemical stability, and processing performance. However, with the advancement of technology and the continuous expansion of application areas, the performance requirements for PET base film are becoming increasingly stringent, especially in terms of mechanical properties.

[0003] Traditional PET base films may not meet the mechanical properties required for certain applications, such as as current collector base films. Current collector base films play a crucial role in electronic devices such as batteries and capacitors, needing to withstand significant mechanical stress and deformation while maintaining good electrical performance. Therefore, improving the mechanical properties of PET base films to better suit these high-end applications has become a current research hotspot.

[0004] To enhance the mechanical properties of PET base films, various methods have been explored, such as adding reinforcing agents, surface modification, and employing multilayer composite structures. Among these, multilayer composite structures are an effective reinforcement method, significantly improving the overall performance of the base film through the synergistic effect between different layers. However, existing multilayer composite PET base films still have shortcomings in terms of mechanical properties. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a method for producing a PET composite current collector base film with enhanced mechanical properties.

[0006] To solve the above problems, the technical solution of the present invention is: a method for producing a PET composite current collector base film with enhanced mechanical properties, wherein the base film includes a reinforcing layer, an outer layer, an intermediate core layer and an inner layer; The outer layer is composed of 1,4-cyclohexanediethanol / isosorbitol modified PET and polyetherimide; The intermediate core layer is composed of PET, hexamethylene diisocyanate, antioxidant, mLLDPE, and POE-g-GMA; The inner layer is composed of microwave-modified PET and natural rubber; The production method of the base film includes the following steps: (1) Microwave-irradiated modified PET was prepared by surface grafting modification of PET using microwave irradiation process and silane coupling agent KH550. (2) 1,4-cyclohexanediethanol / isosorbitol modified PET was synthesized using ethylene glycol, isosorbide, 1,4-cyclohexanediethanol and terephthalic acid as raw materials; (3) The outer layer, middle core layer and inner layer raw materials are blended and sent to their respective extruders for mixing and plasticizing; (3) The molten melt is fed into the die head separately. After the melt merges in the die head, it forms a molten sheet through the flat die head opening. (4) The sheet is attached to the cooling roller with an air knife and cooled rapidly to form an unshaped sheet. Then, the sheet is shaped into a cast sheet after being cooled in a water bath. (5) The cast sheet is stretched to form a thin film; (6) Gallic acid containing an orthophenolic hydroxyl structure and aminosilane KH792 containing a primary amino group are co-deposited on the surface of the outer and inner layers of the film through hydrolysis condensation reaction, Michael addition reaction and Schiff base reaction to form a reinforcing layer.

[0007] (7) Wind up the film.

[0008] Further, step (1) specifically involves: placing PET in a container, adding acetone and soaking for 24 hours, washing PET with deionized water and anhydrous ethanol until neutral, drying PET in an 80°C oven to obtain pretreated PET, adding silane coupling agent KH550, anhydrous ethanol, and deionized water to another container, and hydrolyzing at 80°C for 20 minutes in a microwave material chemistry workstation, adding pretreated PET, activating the pretreated PET at 80°C in a microwave material chemistry workstation for 2 hours, washing PET with deionized water and anhydrous ethanol until neutral, and drying to obtain microwave irradiated modified PET.

[0009] Further, step (2) specifically involves preparing 1,4-cyclohexanediethanol / isosorbitol modified PET using a direct esterification-melt polycondensation method: terephthalic acid, ethylene glycol, isosorbitol, 1,4-cyclohexanediethanol, and germanium dioxide are added to a reactor. After nitrogen purging three times, an esterification reaction is carried out. The reaction pressure is controlled at 0.3 MPa, and the esterification temperature is controlled at 240℃. After 2.5 h, the esterification is completed, and a vacuum is drawn to enter the pre-shrinking and final shrinking stages. The temperature is controlled at 275℃, and the pressure is controlled at 100 Pa. When the stirring power reaches the set value, the material is discharged to obtain 1,4-cyclohexanediethanol / isosorbitol modified PET.

[0010] Further, step (6) specifically involves: dissolving gallic acid in Tris-HCl buffer and stirring magnetically for 30 min; dissolving aminosilane KH792 containing primary amine groups in anhydrous ethanol and stirring magnetically for 30 min; mixing the two solutions and placing the PET film in them, allowing it to stand at room temperature for 10 h, washing with deionized water, and drying in a 65°C oven to form an reinforcing layer on both the outer and inner surfaces.

[0011] Furthermore, the outer layer components are in the following mass ratio: 90% 1,4-cyclohexanediethanol / isosorbitol modified PET and 10% polyetherimide; the mass ratio of 1,4-cyclohexanediethanol and isosorbitol in the 1,4-cyclohexanediethanol / isosorbitol modified PET is 4:1.

[0012] Furthermore, the components of the intermediate core layer are as follows by mass: PET 73.9%, hexamethylene diisocyanate 1.6%, antioxidant 0.5%, mLLDPE 18%, and POE-g-GMA 6%.

[0013] Furthermore, the components of the inner layer are in the following mass ratio: 90% microwave-modified PET and 10% natural rubber.

[0014] The beneficial effects of this invention are: The outer layer of PET is modified with isosorbide and 1,4-cyclohexanediethanol, which gradually increases the glass transition temperature and improves the impact strength, but slightly reduces the tensile strength. The addition of 10% intrinsic flame retardant polyetherimide not only improves the flame retardant properties of the composite material, but also improves the tensile strength of the composite material, thus compensating for the reduction in tensile strength caused by the modification of PET with isosorbide and 1,4-cyclohexanediethanol. The addition of hexamethylene diisocyanate to the intermediate core layer increases the intrinsic viscosity of PET and slightly improves the mechanical properties of the composite material. The intermediate core layer contains mLLDPE, which has the advantages of good impact resistance, high tear strength and puncture resistance. POE-g-GMA can effectively compatibilize PET / mLLDPE and improve the notched impact strength of the composite material. POE-g-GMA inhibits the crystallization of the PET phase and the complex viscosity of the PET / mLLDPE composite material increases. The inner layer is made of microwave-modified PET and natural rubber blend. Under microwave activation, the silane coupling agent KH550 adheres to the surface of PET short fibers, which helps to improve the interfacial adhesion between PET and natural rubber and can improve dynamic mechanical properties. The outer and inner layers are reinforced by surface deposition, forming a polymer micro / nano roughened morphology with high surface energy, which improves the thermal stability and mechanical properties of the material. Detailed Implementation

[0015] To provide a more intuitive and complete understanding of the technical solution of this invention, the following non-limiting features are described: A method for producing a PET composite current collector base film with enhanced mechanical properties, the base film comprising a reinforcing layer, an outer layer, a middle core layer, and an inner layer; The outer layer is composed of 1,4-cyclohexanediethanol / isosorbitol modified PET and polyetherimide; The intermediate core layer is composed of PET, hexamethylene diisocyanate, antioxidant, mLLDPE, and POE-g-GMA; The inner layer is composed of microwave-modified PET and natural rubber; The production method of the base film includes the following steps: (1) Microwave-irradiated modified PET was prepared by surface grafting modification of PET using microwave irradiation process and silane coupling agent KH550. (2) 1,4-cyclohexanediethanol / isosorbitol modified PET was synthesized using ethylene glycol, isosorbide, 1,4-cyclohexanediethanol and terephthalic acid as raw materials; (3) The outer layer, middle core layer and inner layer raw materials are blended and sent to their respective extruders for mixing and plasticizing; (3) The molten melt is fed into the die head separately. After the melt merges in the die head, it forms a molten sheet through the flat die head opening. (4) The sheet is attached to the cooling roller with an air knife and cooled rapidly to form an unshaped sheet. Then, the sheet is shaped into a cast sheet after being cooled in a water bath. (5) The cast sheet is stretched to form a thin film; (6) Gallic acid containing an orthophenolic hydroxyl structure and aminosilane KH792 containing a primary amino group are co-deposited on the surface of the outer and inner layers of the film through hydrolysis condensation reaction, Michael addition reaction and Schiff base reaction to form a reinforcing layer.

[0016] (7) Wind up the film.

[0017] Step (1) is as follows: Place PET in a container, add acetone and soak for 24 hours, wash PET with deionized water and anhydrous ethanol until neutral, dry PET in an 80°C oven to obtain pretreated PET, add silane coupling agent KH550, anhydrous ethanol and deionized water to another container, and hydrolyze at 80°C for 20 minutes in a microwave material chemistry workstation, add pretreated PET, activate pretreated PET at 80°C in a microwave material chemistry workstation for 2 hours, wash PET with deionized water and anhydrous ethanol until neutral, and dry to obtain microwave irradiated modified PET.

[0018] Step (2) specifically involves preparing 1,4-cyclohexanediethanol / isosorbitol modified PET using a direct esterification-melt polycondensation method: terephthalic acid, ethylene glycol, isosorbitol, 1,4-cyclohexanediethanol, and germanium dioxide are added to a reactor. After nitrogen purging three times, an esterification reaction is carried out. The reaction pressure is controlled at 0.3 MPa, and the esterification temperature is controlled at 240℃. Esterification is completed after 2.5 h. Vacuum is then applied to enter the pre-shrinking and final shrinking stages. The temperature is controlled at 275℃, and the pressure is controlled at 100 Pa. When the stirring power reaches the set value, the material is discharged to obtain 1,4-cyclohexanediethanol / isosorbitol modified PET.

[0019] Step (6) specifically involves: dissolving gallic acid in Tris-HCl buffer (pH=8.5) and magnetically stirring for 30 min; dissolving aminosilane KH792 containing primary amine groups in anhydrous ethanol and magnetically stirring for 30 min; mixing the two solutions and placing the PET film in the mixture, allowing it to react at room temperature for 10 h, washing with deionized water, and drying in a 65℃ oven, forming a reinforcing layer on both the outer and inner surfaces. The molar ratio of gallic acid to KH792 is 1:1.

[0020] The components of the outer layer, middle core layer, and inner layer are in the following mass ratio: outer layer 20%, middle core layer 60%, and inner layer 20%.

[0021] The outer layer components are in the following mass ratio: 90% 1,4-cyclohexanediethanol / isosorbitol modified PET and 10% polyetherimide; the mass ratio of 1,4-cyclohexanediethanol and isosorbitol in the 1,4-cyclohexanediethanol / isosorbitol modified PET is 4:1.

[0022] The components of the intermediate core layer, by mass ratio, are: PET 73.9%, hexamethylene diisocyanate 1.6%, antioxidant 0.5%, mLLDPE 18%, and POE-g-GMA 6%. The antioxidant is antioxidant 168.

[0023] The inner layer is composed of the following components by mass ratio: 90% microwave-modified PET and 10% natural rubber.

[0024] The outer layer of this invention is modified PET with isosorbide and 1,4-cyclohexanediethanol, which gradually increases the glass transition temperature and improves the impact strength, but slightly reduces the tensile strength. The addition of 10% intrinsic flame retardant polyetherimide not only improves the flame retardant performance of the composite material, but also improves the tensile strength of the composite material, thus compensating for the reduction in tensile strength caused by the modification of PET with isosorbide and 1,4-cyclohexanediethanol. Polyetherimide is a high-performance engineering plastic with a chemical structure similar to aromatic polymers and excellent thermal stability. It can be used at high temperatures for a long time without decomposition or degradation. At the same time, polyetherimide has good mechanical properties, with excellent strength, stiffness, wear resistance and impact resistance. It is also an intrinsically flame-retardant material. When the mass fraction of polyetherimide is 10%, the tensile strength of the PET / polyetherimide composite material is the highest because the compatibility between PET and polyetherimide is relatively good at this point. The addition of hexamethylene diisocyanate to the intermediate core layer increases the intrinsic viscosity of PET and slightly improves the mechanical properties of the composite material. As a chain extender, hexamethylene diisocyanate's chain extension and thickening mechanism involves a chemical reaction between the terminal hydroxyl groups of PET and the isocyanate groups of the chain extender. The two are linked by chemical bonds, which extends the molecular chain and increases the molecular weight. The longer the molecular chain, the easier it is for them to entangle and form a topological entanglement network. The relative movement of the molecular chains is hindered, which increases the macroscopic viscosity of the system. The intermediate core layer incorporates mLLDPE, which possesses advantages such as good impact resistance, high tear strength, and puncture resistance. POE-g-GMA effectively compatibilizes PET / mLLDPE, improving the notched impact strength of the composite material. POE-g-GMA inhibits the crystallization of the PET phase, resulting in an increase in the complex viscosity of the PET / mLLDPE composite material. The addition of POE-g-GMA reduces the interfacial tension between PET and mLLDPE, enhancing the bonding between the two phases and thus improving the impact resistance of the composite material. POE-g-GMA reacts with the terminal hydroxyl groups in PET to form a graft copolymer, enhancing the entanglement between molecular chains. The inner layer is a blend of microwave-modified PET and natural rubber. Under microwave activation, the silane coupling agent KH550 adheres to the surface of the PET short fibers, which improves the interfacial adhesion between PET and natural rubber and enhances dynamic mechanical properties. After microwave-activated KH550 graft modification, the modified PET surface is covered with a layer of uniformly dispersed particles. This is because, under microwave activation, KH550 adheres to the PET surface, increasing the relative specific surface area of ​​PET and further improving the interfacial adhesion between PET and natural rubber. Under microwave irradiation, the abundant Si-OH groups in the KH550 molecules undergo a dehydration reaction with the -OH groups in PET, resulting in surface graft modification of the modified PET and improved hydrophobicity, which facilitates the dispersion of the modified PET in the rubber and improves the adhesion between it and natural rubber. The tensile stress of the microwave-modified PET / natural rubber composite material is significantly increased due to the stronger interfacial interaction between the microwave-modified PET and natural rubber. During deformation, there is a large interfacial adhesion and internal friction energy. Microwave irradiation modified PET serves as a crosslinking point, increasing the crosslinking density and restricting the slippage between rubber molecular chains. This increases the tear strength of the composite material and improves its dynamic mechanical properties. The outer and inner surface deposition reinforcement layers form a polymer micro-nano roughened morphology with high surface energy, improving the thermal stability and mechanical properties of the material. The modification effect of gallic acid enables the self-polymerization of a relatively dense film on the PET surface, delaying the thermal decomposition process of PET. The introduction of gallic acid / KH792 coating can, on the one hand, repair the surface defects of PET to a certain extent, so that the internal stress of PET can be uniformly transmitted when subjected to external force. At the same time, the three-phase mixed polymerization based on phenolic hydroxyl, silanol, and amino groups makes the coating structure compact and complex, with high molecular bond energy and strong molecular chain entanglement, which improves the adhesion strength between the coating and PET and exhibits strong tensile strength under external load.

[0025] The outer layer utilizes isosorbide and 1,4-cyclohexanediethanol to modify PET, improving its glass transition temperature and impact strength. Polyetherimide compensates for the reduced tensile strength and imparts flame retardant properties. The reinforcing layer further enhances thermal stability and mechanical properties. A dense film formed by gallic acid slows thermal decomposition, and polymerization based on phenolic hydroxyl groups strengthens the bond strength between the coating and the outer layer. This allows the outer layer to retain its inherent performance advantages while also improving thermal stability and tensile strength. The reinforcing layer forms a high-surface-energy polymer micro / nano-roughening morphology on the optimized outer layer surface, repairing surface defects and enabling more uniform stress distribution under external forces, further improving overall mechanical properties.

[0026] The intermediate core layer utilizes hexamethylene diisocyanate as a chain extender to increase molecular chain length and viscosity, mLLDPE to enhance impact resistance, and POE-g-GMA to improve notched impact strength. These improvements provide a more robust mechanical support foundation for the outer layer, synergistically enhancing the overall mechanical properties of the base film with the improved mechanical properties of the outer layer itself. The enhanced mechanical properties of the intermediate core layer allow the reinforcing layer to better exert its strengthening effect within the overall structure of the base film. Because the internal structure of the base film is stable, the surface strengthening effect of the reinforcing layer can be more effectively transferred to the entire base film, thereby improving the overall performance of the base film.

[0027] The inner layer is a blend of microwave-modified PET and natural rubber, with the silane coupling agent KH550 used to improve interfacial adhesion and enhance dynamic mechanical properties. The reinforcing layer further strengthens the optimized inner layer surface, not only repairing surface defects but also enhancing adhesion through a polymer structure. This results in improved thermal stability and tensile strength in the inner layer, while maintaining good dynamic mechanical properties. The strong bond between the inner and reinforcing layers contributes to improved overall stability of the base film. The synergistic effect of the excellent mechanical properties of the inner layer and the strengthening effect of the reinforcing layer allows the base film to better maintain structural integrity and reduce deformation and damage when subjected to external forces and heat.

[0028] The inner layer, a blend of microwave-modified PET and natural rubber, enhances dynamic mechanical properties such as tear strength. This complements the overall mechanical properties improved by the intermediate core layer and the glass transition temperature, impact strength, and tensile strength increased by the outer layer. Each layer leverages its own advantages to collectively improve the mechanical properties of the base film from different perspectives, adapting to diverse application requirements. The inner layer, intermediate core layer, and outer layer are tightly bonded together, maintaining the structural stability of the base film. The stable structure of the inner layer provides support for the intermediate core layer and outer layer, while the intermediate core layer and outer layer protect and reinforce the inner layer, enabling the base film to withstand greater mechanical stress and deformation as a whole.

Claims

1. A method of producing a mechanically enhanced PET composite current collector base film, characterized by: The base film consists of a reinforcing layer, an outer layer, a core layer, and an inner layer; The outer layer is composed of 1,4-cyclohexanediethanol / isosorbitol modified PET and polyetherimide; The intermediate core layer is composed of PET, hexamethylene diisocyanate, antioxidant, mLLDPE, and POE-g-GMA; The inner layer is composed of microwave-modified PET and natural rubber; The production method includes the following steps: (1) Microwave-irradiated modified PET was prepared by surface grafting modification of PET using microwave irradiation process and silane coupling agent KH550. (2) 1,4-cyclohexanediethanol / isosorbitol modified PET was synthesized using ethylene glycol, isosorbide, 1,4-cyclohexanediethanol and terephthalic acid as raw materials; (3) The outer layer, middle core layer and inner layer raw materials are blended and sent to their respective extruders for mixing and plasticizing; (3) The molten melt is fed into the die head separately. After the melt merges in the die head, it forms a molten sheet through the flat die head opening. (4) The sheet is attached to the cooling roller with an air knife and cooled rapidly to form an unshaped sheet. Then, the sheet is shaped into a cast sheet after being cooled in a water bath. (5) The cast sheet is stretched to form a thin film; (6) Gallic acid containing an orthophenolic hydroxyl structure and aminosilane KH792 containing a primary amine group are co-deposited on the surface of the outer and inner layers of the film through hydrolysis condensation reaction, Michael addition reaction and Schiff base reaction to form a reinforcing layer; (7) Wind up the film.

2. The method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: Step (1) is as follows: Place PET in a container, add acetone and soak for 24 hours, wash PET with deionized water and anhydrous ethanol until neutral, dry PET in an 80°C oven to obtain pretreated PET, add silane coupling agent KH550, anhydrous ethanol and deionized water to another container, and hydrolyze at 80°C for 20 minutes in a microwave material chemistry workstation, add pretreated PET, activate pretreated PET at 80°C in a microwave material chemistry workstation for 2 hours, wash PET with deionized water and anhydrous ethanol until neutral, and dry to obtain microwave irradiated modified PET.

3. The method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: Step (2) specifically involves preparing 1,4-cyclohexanediethanol / isosorbitol modified PET using a direct esterification-melt polycondensation method: terephthalic acid, ethylene glycol, isosorbitol, 1,4-cyclohexanediethanol, and germanium dioxide are added to a reactor. After nitrogen purging three times, an esterification reaction is carried out. The reaction pressure is controlled at 0.3 MPa, and the esterification temperature is controlled at 240℃. Esterification is completed after 2.5 h. Vacuum is then applied to enter the pre-shrinking and final shrinking stages. The temperature is controlled at 275℃, and the pressure is controlled at 100 Pa. When the stirring power reaches the set value, the material is discharged to obtain 1,4-cyclohexanediethanol / isosorbitol modified PET.

4. A method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: Step (6) is as follows: Gallic acid is dissolved in Tris-HCl buffer and magnetically stirred for 30 min; aminosilane KH792 containing primary amine group is dissolved in anhydrous ethanol and magnetically stirred for 30 min; the two solutions are mixed and the PET film is placed in them, and the reaction is allowed to stand at room temperature for 10 h. After washing with deionized water, the film is dried in an oven at 65 ℃, and a reinforcing layer is formed on both the outer and inner surfaces.

5. A method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: The outer layer components are in the following mass ratio: 90% 1,4-cyclohexanediethanol / isosorbitol modified PET and 10% polyetherimide; the mass ratio of 1,4-cyclohexanediethanol and isosorbitol in the 1,4-cyclohexanediethanol / isosorbitol modified PET is 4:

1.

6. A method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: The components of the intermediate core layer by mass ratio are: PET 73.9%, hexamethylene diisocyanate 1.6%, antioxidant 0.5%, mLLDPE 18%, and POE-g-GMA 6%.

7. A method for producing a mechanically enhanced PET composite current collector film according to claim 1, characterized in that: The inner layer is composed of the following components by mass ratio: 90% microwave-modified PET and 10% natural rubber.