Production method of flame-retardant and toughened ultra-thin PET composite current collector base film

Abstract

The application discloses a production method of a flame-retardant and toughened ultrathin PET composite current collector base film, and the base film comprises an outer layer, a middle core layer and an inner layer; the outer layer is composed of PET, titanium white, carbon black, an ultraviolet absorber, a dispersing agent and nano zinc oxide; the middle core layer is composed of PET, PA6 and carbon nanosphere surface grafted aromatic Schiff base; and the inner layer is composed of PET, glass fiber, PBT, POE-g-GMA, an antioxidant, a lubricant and polybutylene succinate ionomer. The base film prepared by the method has multiple excellent performances such as flame retardation and toughness, and meets the high-performance requirement of the related field on the PET base film.

Description

Technical Field

[0001] This invention relates to the field of PET base film technology, specifically a method for producing a flame-retardant and toughened ultrathin PET composite current collector base film. Background Technology

[0002] While existing ultrathin PET (polyethylene terephthalate) film production technologies have led to the widespread use of PET films in packaging, electronics, optics, and other fields due to their excellent physical properties, chemical stability, and processing performance, some shortcomings remain. In particular, traditional PET films often struggle to meet higher requirements in terms of flame retardancy, toughness, and performance in specific application scenarios.

[0003] Firstly, regarding flame retardancy, traditional PET films tend to spread rapidly when burning, and the molten droplets produced during combustion can exacerbate the fire's spread, posing a safety hazard. Therefore, developing PET films with highly efficient flame-retardant properties has become an urgent problem for the industry.

[0004] Secondly, regarding toughness, although PET film possesses a certain strength, its toughness performance still needs improvement in certain applications requiring high toughness and impact resistance. Furthermore, with technological advancements and diversified market demands, higher requirements are being placed on the performance of PET film, necessitating targeted improvements and optimizations. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a method for producing a flame-retardant and toughened ultrathin PET composite current collector film.

[0006] To solve the above problems, the technical solution of the present invention is: a method for producing a flame-retardant and toughened ultrathin PET composite current collector base film, wherein the base film includes an outer layer, a middle core layer and an inner layer; The outer layer is composed of PET, titanium dioxide, carbon black, ultraviolet absorber, dispersant, and nano zinc oxide; The intermediate core layer consists of PET, PA6, and aromatic Schiff bases grafted onto the surface of carbon nanospheres; The inner layer is composed of PET, glass fiber, PBT, POE-g-GMA, antioxidants, lubricants, and polybutylene succinate ionomer; The production method includes the following steps: (1) The outer layer of nano zinc oxide is surface modified with silane coupling agent KH560 and then blended with PET, titanium dioxide, carbon black, ultraviolet absorber and dispersant; the raw materials of the middle core layer are blended; the raw materials of the inner layer are blended. (2) The outer layer, middle core layer and inner layer raw materials are fed into 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) Wind up the film.

[0007] Furthermore, the outer layer of nano-zinc oxide is surface modified by silane coupling agent KH560 as follows: nano-zinc oxide is added to distilled water, ultrasonically dispersed for 30 min, then mechanically stirred at 300 r / min for 25 min, then silane coupling agent KH560 (mass fraction) is added, the pH of the mixed solution is adjusted to 8 with glacial acetic acid and sodium carbonate, mechanically stirred in a 60 ℃ water bath for 1 h, and then centrifuged and dried.

[0008] Furthermore, the preparation method of aromatic Schiff base grafted onto the surface of carbon nanospheres in the intermediate core layer is as follows: carboxylated carbon nanospheres are prepared by acidification. Calcium chloride is added to dichloromethane and shaken at room temperature for 10 hours to remove moisture. Anhydrous dichloromethane is added to a container as a reaction solvent. Carboxylated carbon nanospheres are added under stirring, followed by 4-benzylmethylaminophenol and 4-dimethylaminopyridine. The temperature is raised to 30°C and reacted under stirring for 2 hours. After the reaction is completed, the liquid is removed by filtration. The solid obtained from the reaction is washed successively with ethanol and distilled water, dried at 100°C for 6 hours, and then ground uniformly to obtain aromatic Schiff base grafted onto the surface of carbon nanospheres.

[0009] Furthermore, the outer layer consists of the following components by mass ratio: 60% PET, 30% titanium dioxide, 0.3% carbon black, 3.5% ultraviolet absorber, 1.2% dispersant, and 5% nano zinc oxide.

[0010] Furthermore, the components of the intermediate core layer are as follows by mass ratio: PET 78%, PA6 20%, and aromatic Schiff base grafted onto the surface of carbon nanospheres 2%.

[0011] Furthermore, the components of the inner layer are as follows by mass ratio: PET 51%, glass fiber 25%, PBT 17%, POE-g-GMA 1%, antioxidant 0.5%, lubricant 0.5%, and polybutylene succinate ionomer 5%.

[0012] The beneficial effects of this invention are: the addition of light-blocking material to the outer layer can improve the light-blocking performance of the composite material, resulting in a good light shielding effect, and also improves the tensile strength and flexural modulus; The addition of nano-zinc oxide to the outer layer enhances the antibacterial properties of the composite material. The intermediate core layer is grafted with aromatic Schiff bases on the surface of carbon nanospheres, which causes high-temperature cross-linking after PET melts, resulting in a significant improvement in the density, continuity and thermal stability of the carbon layer generated by the combustion of the composite material. The introduction of PA6 into the intermediate core layer significantly improves the elongation at break and impact strength of the composite material, and significantly enhances its toughness. This is because the addition of aromatic Schiff base grafted onto the surface of carbon nanospheres reduces the elongation at break of the composite material, so PA6 compensates for this defect. The inner layer incorporates PBT, which improves the processing performance of PET. PBT itself has a certain degree of toughness, and its addition to PET can enhance the impact resistance of the film. The addition of glass fiber to the PET / PBT system can significantly improve the heat resistance and mechanical properties of the composite material. Polybutylene succinate ionomer is a linear polymer containing sulfonic acid groups, which can be uniformly dispersed in the PET matrix and react as an effective nucleating agent, which is beneficial to the crystallization of PET. Detailed Implementation

[0013] 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 flame-retardant and toughened ultrathin PET composite current collector base film, wherein the base film comprises an outer layer, a middle core layer and an inner layer; The outer layer is composed of PET, titanium dioxide, carbon black, ultraviolet absorber, dispersant, and nano zinc oxide; The intermediate core layer consists of PET, PA6, and aromatic Schiff bases grafted onto the surface of carbon nanospheres; The inner layer is composed of PET, glass fiber, PBT, POE-g-GMA, antioxidants, lubricants, and polybutylene succinate ionomer; The production method of the base film includes the following steps: (1) The outer layer of nano zinc oxide is surface modified with silane coupling agent KH560 and then blended with PET, titanium dioxide, carbon black, ultraviolet absorber and dispersant; the raw materials of the middle core layer are blended; the raw materials of the inner layer are blended. (2) The outer layer, middle core layer and inner layer raw materials are fed into 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) Wind up the film.

[0014] Furthermore, the outer layer of nano-zinc oxide is surface modified by silane coupling agent KH560 as follows: nano-zinc oxide is added to distilled water, ultrasonically dispersed for 30 min, then mechanically stirred at 300 r / min for 25 min, then silane coupling agent KH560 (mass fraction) is added, the pH of the mixed solution is adjusted to 8 with glacial acetic acid and sodium carbonate, mechanically stirred in a 60 ℃ water bath for 1 h, and then centrifuged and dried.

[0015] The preparation method of aromatic Schiff base grafted onto the surface of carbon nanospheres in the intermediate core layer is as follows: Carboxylated carbon nanospheres are prepared by acidification. Calcium chloride is added to dichloromethane and shaken at room temperature for 10 hours to remove moisture. Anhydrous dichloromethane is added to a container as a reaction solvent, and carboxylated carbon nanospheres are added under stirring. Then, 4-benzylmethylaminophenol and 4-dimethylaminopyridine are added, and the temperature is raised to 30°C. The reaction is carried out under stirring for 2 hours. After the reaction is completed, the liquid is removed by filtration. The resulting solid is washed successively with ethanol and distilled water, dried at 100°C for 6 hours, and then ground uniformly to obtain the aromatic Schiff base grafted onto the surface of the carbon nanospheres. The surface of the aromatic Schiff base grafted onto the carbon nanospheres has increased nitrogen element, which originates from the amino group in the 4-benzylmethylaminophenol grafted onto its surface. The 4-benzylmethylaminophenol grafting modification of the carbon nanospheres promotes the crosslinking of PET. This is because the aromatic Schiff base grafted onto the flame retardant surface can form a stable crosslinking network between the melting temperature and decomposition temperature of PET.

[0016] 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%.

[0017] The outer layer consists of the following components by mass ratio: 60% PET, 30% titanium dioxide, 0.3% carbon black, 3.5% UV absorber, 1.2% dispersant, and 5% nano zinc oxide. The dispersant is a fatty acid-based dispersant, and the UV absorber is a UV234 UV absorber.

[0018] The components of the intermediate core layer are as follows by mass ratio: PET 78%, PA6 20%, and aromatic Schiff base grafted onto the surface of carbon nanospheres 2%.

[0019] The inner layer consists of the following components by mass ratio: PET 51%, glass fiber 25%, PBT 17%, POE-g-GMA 1%, antioxidant 0.5%, lubricant 0.5%, and polybutylene succinate ionomer 5%. The lubricant is polyethylene wax, and the antioxidant is antioxidant 168.

[0020] The outer layer of this invention incorporates a light-blocking material, which enhances the light-blocking performance of the composite material, providing excellent light shielding. It also improves tensile strength and flexural modulus. Titanium dioxide, an inorganic material with excellent mechanical properties, can intertwine with PET polymer chains in the composite system, forming numerous physical cross-linking points. Furthermore, the filler and polymer matrix exhibit good interfacial bonding, leading to an increase in the sample's tensile strength. Additionally, titanium dioxide particles are inorganic and possess rigidity; the addition of titanium dioxide enhances the sample's rigidity, thereby increasing the material's flexural modulus. The addition of nano-zinc oxide to the outer layer enhances the antibacterial properties of the composite material. The intermediate core layer incorporates aromatic Schiff bases grafted onto the surface of carbon nanospheres, causing high-temperature cross-linking of the PET after melting. This significantly improves the density, continuity, and thermal stability of the char layer formed during combustion. Grafting of carbon nanospheres with 4-benzylaminophenol further enhances the char-forming effect on PET. Compared to pure PET, the char layer of carbon nanospheres grafted with aromatic Schiff bases / PET exhibits significantly improved density and smaller pores. The density and continuity of the carbon layer are further enhanced, with fewer and smaller surface pores. Additionally, numerous bulging, unbroken bubbles are present. This morphology of the char layer effectively blocks heat transfer during combustion and also effectively prevents PET from entering the combustion chamber. The release of gaseous combustibles generated during combustion and degradation serves as heat insulation and oxygen barrier. The carbon dioxide, ammonia, and nitrogen produced by the thermal decomposition of aromatic Schiff bases grafted onto the surface of carbon nanospheres dilute the concentration of combustible gases in the combustion zone, inhibiting combustion progression. This is a key reason for the improved flame retardancy of carbon nanospheres grafted with aromatic Schiff bases / PET. The aromatic Schiff bases grafted onto the surface of the flame retardant carbon nanospheres enable PET to burn and form a structurally stable char layer. This char layer can withstand high flame temperatures during combustion, thus providing long-lasting and effective protection to the internal matrix. The pyrolysis products of carbon nanospheres grafted with aromatic Schiff bases / PET include polycyclic aromatic hydrocarbons such as phenanthrene, naphthalene, acenaphthene, and fluorene, as well as biphenyl products. The aromatic Schiff bases grafted onto the surface of the carbon nanospheres promote cross-linking during PET degradation. This cross-linking improves dripping phenomena by increasing melt viscosity and enhances the density and thermal stability of the char layer. This is the main reason for the improved flame retardancy and anti-dripping properties of carbon nanospheres grafted with aromatic Schiff bases.

[0021] The introduction of PA6 into the core layer significantly improves the elongation at break and impact strength of the composite material, and significantly enhances its toughness. This is because the addition of aromatic Schiff base grafted onto the surface of carbon nanospheres reduces the elongation at break of the composite material, so PA6 compensates for this deficiency. As a toughening agent, the introduction of nylon elastomer by PA6 significantly improves the toughness of PET sheets, allowing the material to undergo greater plastic deformation without breaking under external force. The inner layer incorporates PBT, which improves the processing performance of PET. PBT itself has a certain degree of toughness, and its addition to PET enhances the impact resistance of the film. The addition of glass fiber to the PET / PBT system can significantly improve the heat resistance and mechanical properties of the composite material. Polybutylene succinate ionomer is a linear polymer containing sulfonic acid groups, which can be uniformly dispersed in the PET matrix and react as an effective nucleating agent, which is beneficial to the crystallization of PET. There is an ionic dipole interaction between the ionic groups of polybutylene succinate ionomer and the ester groups of PET. The PET molecular chains can fold and crystallize around the ionic groups. When ionic clusters are formed, the electrostatic interaction between anions and cations overcomes the steric hindrance effect, bringing the chain segments to the narrow space of the ionic clusters for close packing. The free volume between chains is drastically reduced, inducing crystal nucleation. Multiple chain segments can be fully accommodated around the ionic clusters, and through self-adjustment to a crystalline and compact organizational form, an ordered structure similar to micelles is formed.

[0022] The outer layer of titanium dioxide intertwines with the PET polymer chains to form physical cross-linking points, and exhibits good interfacial bonding with the polymer matrix, thus enhancing tensile strength. Its rigidity also increases the flexural modulus, providing a certain rigidity foundation for the base film. This gives the base film better overall tensile and flexural strength, helping to maintain its shape stability and providing a relatively stable external structure for the core and inner layers.

[0023] The introduction of PA6 as a toughening agent in the core layer significantly improves the elongation at break and impact strength of the composite material, enhancing its toughness. Although grafting aromatic Schiff bases onto the carbon nanospheres reduces the elongation at break, PA6 compensates for this deficiency. This improved toughness, combined with the rigidity provided by the outer layer, allows the base film to withstand a certain degree of deformation without breaking while maintaining sufficient strength, balancing the overall mechanical properties of the base film and providing buffer protection for the performance of the inner layer material.

[0024] The addition of PBT to the inner layer enhances the film's impact resistance, while the inclusion of glass fiber significantly improves its heat resistance and mechanical properties. The improved overall mechanical properties of the inner layer, enhanced by these components, combined with the rigidity of the outer layer and the toughness of the core layer, further perfect the mechanical property system of the base film. For example, under complex external forces, the outer layer resists tension and bending, the core layer absorbs impact energy, and the inner layer, through its enhanced properties, works in concert to cope with these forces, enabling the base film as a whole to better withstand various stresses.

[0025] The aromatic Schiff base grafted onto the surface of the carbon nanospheres in the intermediate core layer is the main flame-retardant component. It causes high-temperature cross-linking of the PET after melting, generating a dense, continuous, and thermally stable char layer that blocks heat and combustible gases, while simultaneously decomposing to produce flame-retardant gases that inhibit combustion. Although the outer layer does not directly participate in the main flame-retardant chemical reactions, its light-blocking material enhances the light-shielding effect, reducing the aging of the base film and potential combustion risks caused by light exposure, thus assisting the flame-retardant effect of the intermediate core layer. While the inner layer does not have direct flame-retardant function, its good processing and crystallization properties help maintain the stability of the base film structure, preventing changes in the internal structure from affecting the flame-retardant performance of the intermediate core layer, thereby indirectly synergistically contributing to the overall flame-retardant performance of the base film with the intermediate core layer.

[0026] The addition of nano-zinc oxide to the outer layer endows the composite material with antibacterial properties. This not only ensures a hygienic environment on the outer surface of the base film but also prevents performance degradation due to microbial erosion, thus guaranteeing the overall performance stability of the base film. Although the middle core layer and inner layer do not have antibacterial functions, their excellent mechanical and processing properties help maintain the integrity of the base film, allowing the antibacterial properties of the outer layer to be better exerted. The three layers work together to ensure the performance and service life of the base film under various environments from different perspectives.

[0027] The inner PBT layer improves the processing performance of PET, and the polybutylene succinate ionomer acts as a nucleating agent, which is beneficial to PET crystallization. These properties make the inner layer material easier to shape during processing. The good processing performance of the inner layer, together with the outer layer and the middle core layer during the mixing and plasticizing process, ensures the smooth shaping of the entire base film during production. For example, after mixing and plasticizing, the components of the outer layer and the middle core layer merge with the inner layer melt in the die head to form a uniform and stable molten sheet, which is ultimately formed into a high-performance base film through subsequent processes.

Claims

1. A method for producing a flame-retardant and toughened ultrathin PET composite current collector base film, the base film comprising an outer layer, a middle core layer, and an inner layer, characterized in that: The outer layer is composed of PET, titanium dioxide, carbon black, ultraviolet absorber, dispersant, and nano zinc oxide; The intermediate core layer consists of PET, PA6, and aromatic Schiff bases grafted onto the surface of carbon nanospheres; The inner layer is composed of PET, glass fiber, PBT, POE-g-GMA, antioxidants, lubricants, and polybutylene succinate ionomer; The production method includes the following steps: (1) The outer layer of nano zinc oxide is surface modified with silane coupling agent KH560 and then blended with PET, titanium dioxide, carbon black, ultraviolet absorber and dispersant; the raw materials of the middle core layer are blended; the raw materials of the inner layer are blended. (2) The outer layer, middle core layer and inner layer raw materials are fed into 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) Wind up the film.

2. The method for producing a flame-retardant and toughened ultrathin PET composite current collector film according to claim 1, characterized in that: The outer layer of nano zinc oxide is surface modified by silane coupling agent KH560 as follows: nano zinc oxide is added to distilled water, ultrasonically dispersed for 30 min, then mechanically stirred at 300 r / min for 25 min, then silane coupling agent KH560 (mass fraction) is added, the pH of the mixed solution is adjusted to 8 with glacial acetic acid and sodium carbonate, mechanically stirred in a 60 ℃ water bath for 1 h, and then centrifuged and dried.

3. The method for producing a flame-retardant and toughened ultrathin PET composite current collector film according to claim 1, characterized in that: The preparation method of aromatic Schiff base grafted on the surface of carbon nanospheres in the middle core layer is as follows: carboxylated carbon nanospheres are prepared by acidification. Calcium chloride is added to dichloromethane and shaken at room temperature for 10 hours to remove moisture. Anhydrous dichloromethane is added to a container as a reaction solvent. Carboxylated carbon nanospheres are added under stirring, followed by 4-benzylmethylaminophenol and 4-dimethylaminopyridine. The temperature is raised to 30°C and the reaction is carried out under stirring for 2 hours. After the reaction is completed, the liquid is removed by filtration. The solid obtained from the reaction is washed successively with ethanol and distilled water, dried at 100°C for 6 hours, and then ground uniformly to obtain aromatic Schiff base grafted on the surface of carbon nanospheres.

4. The method for producing a flame-retardant and toughened ultrathin PET composite current collector film according to claim 1, characterized in that: The outer layer consists of the following components by mass ratio: 60% PET, 30% titanium dioxide, 0.3% carbon black, 3.5% UV absorber, 1.2% dispersant, and 5% nano zinc oxide.

5. A method for producing a flame-retardant and toughened ultrathin PET composite current collector film according to claim 1, characterized in that: The components of the intermediate core layer are as follows by mass ratio: PET 78%, PA6 20%, and aromatic Schiff base grafted onto the surface of carbon nanospheres 2%.

6. A method for producing a flame-retardant and toughened ultrathin PET composite current collector film according to claim 1, characterized in that: The inner layer is composed of the following components by mass ratio: PET 51%, glass fiber 25%, PBT 17%, POE-g-GMA 1%, antioxidant 0.5%, lubricant 0.5%, and polybutylene succinate ionomer 5%.