A process for the production of ultra-low temperature heat-sealable bopp film

Abstract

The application discloses a production method of an ultralow-temperature heat-seal BOPP film, and the ultralow-temperature heat-seal BOPP film comprises a heat-seal layer, a reinforcing layer, a core layer and a functional layer; the heat-seal layer is composed of random copolymerized polypropylene, ethylene-vinyl acetate copolymer, metallocene polyethylene, polybutene-1, hydrogenated styrene-butadiene block copolymer, anti-blocking agent, slip agent, antioxidant and ultraviolet absorber; the reinforcing layer is composed of isotactic polypropylene, glass fiber reinforced polypropylene, polybutylene terephthalate, liquid crystal polymer, maleic anhydride grafted polypropylene, antioxidant and ultraviolet absorber; the core layer is composed of homopolymerized polypropylene, nano calcium carbonate, polyphenylene ether, ethylene-propylene-diene rubber, maleic anhydride grafted polyphenylene ether, silane coupling agent, nucleating agent and lubricant; and the functional layer is composed of polyvinylidene fluoride, polyimide, polyethersulfone, carbon nanotube, polytetrafluoroethylene micro powder, antistatic agent and flame retardant. The BOPP film prepared by the method has good heat-seal performance at ultralow temperature.

Description

Technical Field

[0001] This invention relates to the field of BOPP film technology, specifically a method for producing ultra-low temperature heat-sealed BOPP film. Background Technology

[0002] Traditional BOPP films have certain limitations in heat-sealing performance, especially at ultra-low temperatures, where their heat-sealing effect is often unsatisfactory, limiting their application in specific fields such as frozen food packaging and medical product packaging. To improve the heat-sealing performance of BOPP films, particularly at ultra-low temperatures, researchers have conducted extensive research. Traditional improvement methods include adding heat-sealing agents and changing the polymer ratio, but these methods often affect other film properties, such as mechanical strength and transparency. Therefore, developing a film that maintains the original excellent properties of BOPP films while also exhibiting good heat-sealing performance at ultra-low temperatures has become an urgent need in the industry. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a method for producing ultra-low temperature heat-sealed BOPP film.

[0004] To solve the above problems, the technical solution of the present invention is: a method for producing ultra-low temperature heat-sealing BOPP film, wherein the ultra-low temperature heat-sealing BOPP film includes a heat-sealing layer, a reinforcing layer, a core layer and a functional layer; The heat-sealing layer is composed of random copolymer polypropylene, ethylene-vinyl acetate copolymer, metallocene polyethylene, polybutene-1, hydrogenated styrene-butadiene block copolymer, antiblocking agent, slip agent, antioxidant, and ultraviolet absorber. The reinforcing layer is composed of isotactic polypropylene, glass fiber reinforced polypropylene, polybutylene terephthalate, liquid crystal polymer, maleic anhydride grafted polypropylene, antioxidant, and ultraviolet absorber. The core layer is composed of homopolymer polypropylene, nano-calcium carbonate, polyphenylene ether, EPDM rubber, maleic anhydride-grafted polyphenylene ether, silane coupling agent, nucleating agent, and lubricant. The functional layer is composed of polyvinylidene fluoride, polyimide, polyethersulfone, carbon nanotubes, polytetrafluoroethylene powder, antistatic agent, and flame retardant; The production method includes the following steps: (1) The raw materials for the heat-sealing layer, reinforcing layer, core layer and functional layer are blended separately and then sent to their respective extruders for melt mixing and plasticizing; (2) 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. (3) The sheet is attached to the cooling roller with an air knife and rapidly cooled to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

[0005] Furthermore, the components of the heat-sealing layer are as follows by mass ratio: random copolymer polypropylene 33%, ethylene-vinyl acetate copolymer 22%, metallocene polyethylene 18%, polybutene-1 12%, hydrogenated styrene-butadiene block copolymer 8%, antiblocking agent 3%, slip agent 2%, antioxidant 1%, and ultraviolet absorber 1%.

[0006] Furthermore, the anti-blocking agent is silicon dioxide.

[0007] Furthermore, the components of the reinforcing layer are as follows by mass ratio: isotactic polypropylene 42%, glass fiber reinforced polypropylene 25%, polybutylene terephthalate 15%, liquid crystal polymer 10%, maleic anhydride grafted polypropylene 5%, antioxidant 2%, and ultraviolet absorber 1%.

[0008] Furthermore, the core layer is composed of the following components by mass ratio: 54% homopolymer polypropylene, 15% nano-calcium carbonate, 15% polyphenylene ether, 8% EPDM rubber, 3% maleic anhydride-grafted polyphenylene ether, 2% silane coupling agent, 2% nucleating agent, and 1% lubricant.

[0009] Furthermore, the components of the functional layer are as follows by mass ratio: 30% polyvinylidene fluoride, 25% polyimide, 20% polyethersulfone, 10% carbon nanotubes, 8% polytetrafluoroethylene micropowder, 4% antistatic agent, and 3% flame retardant.

[0010] Furthermore, the flame retardant is a mixture of melamine polyphosphate and aluminum hydroxide.

[0011] The beneficial effects of this invention are as follows: the various components in the heat-sealing layer work synergistically to achieve ultra-low temperature heat sealing, good surface properties, and resistance to external environmental factors; the high-strength and stable material of the reinforcing layer provides solid support and protection for the entire film, tightly bonding with the heat-sealing layer to ensure the structural integrity and performance stability of the film during the heat-sealing process; the components of the core layer work synergistically to optimize crystallization performance, toughness, and processing performance while ensuring the strength and stability of the main body of the film, playing a key role in connecting and balancing the performance of the inner and outer layers; the functional layer endows the film with specific functions such as chemical corrosion resistance, heat resistance, wear resistance, antistatic properties, and flame retardancy, and together with other layers, it constructs a comprehensive and powerful ultra-low temperature heat-sealing BOPP film. Through the mutual penetration and interfacial bonding of components, the various layers achieve complementary and synergistic performance enhancement, resulting in a high degree of coordination and unity in the heat-sealing performance, mechanical strength, stability, and functionality of the entire film, capable of meeting various complex and demanding application requirements. Detailed Implementation

[0012] 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 an ultra-low temperature heat-sealable BOPP film, wherein the ultra-low temperature heat-sealable BOPP film comprises a heat-sealable layer, a reinforcing layer, a core layer, and a functional layer; The heat-sealing layer is composed of random copolymer polypropylene, ethylene-vinyl acetate copolymer, metallocene polyethylene, polybutene-1, hydrogenated styrene-butadiene block copolymer, antiblocking agent, slip agent, antioxidant, and ultraviolet absorber. The slip agent is erucamide, the antioxidant is antioxidant 168, and the ultraviolet absorber is UV-P. The reinforcing layer is composed of isotactic polypropylene, glass fiber reinforced polypropylene, polybutylene terephthalate, liquid crystal polymer, maleic anhydride grafted polypropylene, antioxidant, and ultraviolet absorber. The antioxidant is antioxidant 1010 and the ultraviolet absorber is UV-327. The core layer is composed of homopolymer polypropylene, nano-calcium carbonate, polyphenylene ether, EPDM rubber, maleic anhydride-grafted polyphenylene ether, silane coupling agent, nucleating agent, and lubricant. The silane coupling agent is silane coupling agent KH-560, the nucleating agent is sorbitol nucleating agent, and the lubricant is calcium stearate. The functional layer is composed of polyvinylidene fluoride, polyimide, polyethersulfone, carbon nanotubes, polytetrafluoroethylene micro powder, antistatic agent, and flame retardant. The antistatic agent is a polyether-type antistatic agent. The production method of ultra-low temperature heat-sealable BOPP film includes the following steps: (1) The raw materials for the heat-sealing layer, reinforcing layer, core layer and functional layer are blended separately and then sent to their respective extruders for melt mixing and plasticizing; (2) 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. (3) The sheet is attached to the cooling roller with an air knife and rapidly cooled to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

[0013] The components of the heat-sealing layer by mass ratio are: random copolymer polypropylene 33%, ethylene-vinyl acetate copolymer 22%, metallocene polyethylene 18%, polybutene-1 12%, hydrogenated styrene-butadiene block copolymer 8%, antiblocking agent 3%, slip agent 2%, antioxidant 1%, and ultraviolet absorber 1%.

[0014] The anti-blocking agent is silicon dioxide. Besides preventing adhesion between films, silicon dioxide also has the following functions: Improving slip properties helps reduce the coefficient of friction on the film surface, making the film easier to slide and handle during processing and use; enhancing dispersion helps other additives to be uniformly dispersed in the polymer matrix; it can adjust the haze and transparency of the film; and to a certain extent, it enhances the abrasion resistance of the film surface, reducing surface wear and scratches.

[0015] The components of the reinforcing layer by mass ratio are: isotactic polypropylene 42%, glass fiber reinforced polypropylene 25%, polybutylene terephthalate 15%, liquid crystal polymer 10%, maleic anhydride grafted polypropylene 5%, antioxidant 2%, and ultraviolet absorber 1%.

[0016] The core layer is composed of the following components by mass ratio: 54% homopolymer polypropylene, 15% nano-calcium carbonate, 15% polyphenylene ether, 8% EPDM rubber, 3% maleic anhydride-grafted polyphenylene ether, 2% silane coupling agent, 2% nucleating agent, and 1% lubricant.

[0017] The components of the functional layer by mass ratio are: 30% polyvinylidene fluoride, 25% polyimide, 20% polyethersulfone, 10% carbon nanotubes, 8% polytetrafluoroethylene micropowder, 4% antistatic agent, and 3% flame retardant.

[0018] The flame retardant is a mixture of melamine polyphosphate and aluminum hydroxide, with a mass ratio of melamine polyphosphate to aluminum hydroxide of 1:3. Melamine polyphosphate is highly effective at retardancy, achieving good flame retardant effects with relatively low dosage. It also helps reduce material dripping during combustion, improving fire safety. Aluminum hydroxide acts as a smoke suppressant and is relatively inexpensive. The two have a synergistic flame retardant effect, improving flame retardant efficiency and reducing the amount of each required. Their combination better regulates the material's stability under heat, delaying decomposition and combustion. A proper combination can reduce negative impacts on the material's mechanical properties, maintaining its strength and toughness to some extent. Aluminum hydroxide has a certain degree of water resistance, which, when combined with melamine polyphosphate, helps improve the overall flame retardant stability of the system in humid environments.

[0019] The random copolymer polypropylene of the heat-sealing layer exhibits excellent flexibility, adapting to different shapes and pressures during heat sealing. Its random molecular structure results in low crystallinity, facilitating lower heat-sealing temperatures. The ethylene segments of the ethylene-vinyl acetate copolymer provide flexibility, while the vinyl acetate segments increase polarity, enabling good compatibility with other polymers. Furthermore, its low melting point significantly reduces the heat-sealing temperature while improving heat-sealing strength and ensuring the robustness of the heat-sealed area. Metallocene polyethylene possesses excellent low-temperature toughness, maintaining good performance at low temperatures. Its excellent heat-sealing properties allow for effective heat sealing at lower temperatures. Polybutene-1 has a unique semi-crystalline structure with a slow crystallization rate, allowing for better flow and fusion during heat sealing, further enhancing low-temperature heat-sealing performance. Additionally, the flexibility of polybutene-1 allows it to withstand stretching and deformation during heat sealing, improving reliability. Hydrogenated styrene-butadiene block copolymer, as a thermoplastic elastomer, provides certain hardness and strength through its styrene segments, while the hydrogen... The hydrogenated butadiene segment imparts excellent elasticity and low-temperature performance. In the heat-sealing layer, the hydrogenated styrene-butadiene block copolymer increases the elastic recovery ability of the film and works synergistically with polybutene-1 to further improve the film's flexibility and heat-sealing effect at low temperatures, ensuring high-quality heat sealing even in low-temperature environments. The anti-blocking agent silica, with its tiny particles, can form tiny protrusions on the film surface, reducing the contact area between films and effectively preventing adhesion during storage and use, ensuring smooth film unfolding and use. The slip agent erucamide can reduce the coefficient of friction on the film surface, making the film smoother during processing and use, reducing static electricity and heat generated by friction, and improving production efficiency and product quality. The antioxidant 168 can capture free radicals generated during heat sealing, preventing oxidative degradation of the polymer, thereby extending the film's service life and maintaining its performance stability. The ultraviolet absorber UV-P can absorb ultraviolet rays and convert them into heat energy or harmless low-energy radiation, thereby reducing the damage of ultraviolet rays to the film, protecting the performance of the heat-sealing layer from the influence of ultraviolet rays, and improving the stability of the film in outdoor or strong light environments. Polybutene-1 and hydrogenated styrene-butadiene block copolymer have a significant synergistic effect in terms of low-temperature performance. The semi-crystalline structure and slow crystallization rate of polybutene-1 provide a basis for low-temperature heat sealing, while the elasticity and low-temperature performance of hydrogenated styrene-butadiene block copolymer further enhance the flexibility and resilience of the film at low temperatures. The combined effect of the two enables the heat-sealing layer to maintain good heat-sealing performance and physical properties in low-temperature environments.

[0020] The isotactic polypropylene of the reinforcing layer has high crystallinity and strength, providing good basic support for the reinforcing layer. Glass fiber reinforced polypropylene greatly improves the tensile strength and rigidity of polypropylene, enhancing the overall strength and deformation resistance of the film. Polybutylene terephthalate has good heat resistance, chemical corrosion resistance and mechanical strength, which can improve the heat resistance and mechanical properties of the reinforcing layer. Liquid crystal polymer has extremely high heat resistance, excellent dimensional stability and mechanical strength, which can significantly improve the dimensional stability and heat resistance of the reinforcing layer. Maleic anhydride grafted polypropylene is used to improve the compatibility between the polymers, promote uniform dispersion and bonding, and improve the integrity and performance stability of the reinforcing layer. Antioxidant 1010 is used to extend the service life of the film and maintain performance stability. UV absorber UV-327 prevents UV degradation and damage to the polymer, improving the durability of the film in outdoor or strong UV radiation environments. Polybutylene terephthalate (PET) and liquid crystal polymers have a synergistic reinforcing effect on heat resistance and dimensional stability. The rapid crystallization characteristics and good heat resistance of PET provide initial protection for the reinforcing layer, while the extremely high heat resistance and excellent dimensional stability of liquid crystal polymers further enhance this performance. Under high temperature and complex environment, the synergistic effect of the two enables the reinforcing layer to maintain excellent dimensional stability and mechanical properties, ensuring that the film can still be used normally under harsh conditions.

[0021] The homopolymer polypropylene in the core layer has high crystallinity and strength, providing the main structural support and mechanical properties, ensuring sufficient rigidity and stiffness of the film. Nano-calcium carbonate can be uniformly dispersed in the polymer matrix, playing a reinforcing and filling role, significantly improving the rigidity, heat resistance, and dimensional stability of the core layer. Polyphenylene ether has excellent chemical corrosion resistance, dimensional stability, and electrical properties. In the core layer, polyphenylene ether can cooperate with homopolymer polypropylene to further improve the overall performance of the core layer, especially in terms of chemical corrosion resistance and dimensional stability. EPDM rubber, as an elastomer toughening agent, can significantly improve the toughness and impact resistance of the core layer without significantly reducing its strength. Maleic anhydride-grafted polyphenylene ether, through the active groups of maleic anhydride, can improve the compatibility of polyphenylene ether and homopolymer polypropylene, promoting uniform mixing and interfacial bonding, improving the integrity and performance stability of the core layer. Lubricant can reduce friction between polymer molecules, improve the processing fluidity of the core layer, and reduce processing temperature and energy consumption. Ethylene propylene diene monomer (EPDM) rubber and nucleating agents have a synergistic effect in improving the performance of the core layer. The nucleating agent improves the strength and toughness of the core layer by promoting the crystallization of homopolymer polypropylene, while EPDM rubber further increases the toughness and impact resistance of the core layer on this basis. The two work together to enable the core layer to maintain high strength while having good toughness and impact resistance.

[0022] The functional layer, composed of polyvinylidene fluoride (PVDF), exhibits excellent chemical resistance, weather resistance, and piezoelectric properties. Its superior chemical resistance allows the functional layer to withstand the erosion of various chemicals, while its weather resistance ensures that the film's performance does not degrade during long-term outdoor use. Polyimide (PI) possesses extremely high heat resistance, mechanical strength, and insulation properties. Within the functional layer, PI provides excellent heat protection, ensuring the film maintains stable performance even at high temperatures. Polyethersulfone (PES) offers excellent water resistance, dimensional stability, and mechanical properties, enhancing the film's water resistance and dimensional stability, allowing it to maintain good performance in humid environments. Carbon nanotubes possess extremely high mechanical strength, significantly improving the film's mechanical properties, while their nanoscale size effect also improves the barrier properties of the functional layer. Polytetrafluoroethylene (PTFE) micropowder has an extremely low coefficient of friction and excellent wear resistance. PTFE micropowder reduces the coefficient of friction on the film surface, improving wear resistance, while its good chemical stability enhances the functional layer's corrosion resistance.

[0023] In summary, the synergistic effect of various components in the heat-sealing layer achieves ultra-low temperature heat sealing, excellent surface properties, and resistance to external environmental factors. The high-strength and stable materials in the reinforcing layer provide solid support and protection for the entire film, tightly bonding with the heat-sealing layer to ensure the structural integrity and performance stability of the film during the heat-sealing process. The synergistic effect of the components in the core layer, while ensuring the strength and stability of the main body of the film, optimizes crystallinity, toughness, and processing performance, playing a key role in connecting and balancing the performance of the inner and outer layers. The functional layer endows the film with specific functions such as chemical corrosion resistance, heat resistance, abrasion resistance, antistatic properties, and flame retardancy, and together with other layers, constructs a comprehensive and powerful ultra-low temperature heat-sealing BOPP film. Through the interpenetration and interfacial bonding of components, the various layers achieve complementary and synergistic performance enhancement, resulting in a high degree of coordination and unity in terms of heat-sealing performance, mechanical strength, stability, and functionality, capable of meeting various complex and demanding application requirements.

Claims

1. A method for producing ultra-low temperature heat-sealable BOPP film, characterized in that: Ultra-low temperature heat-sealable BOPP film includes a heat-sealing layer, a reinforcing layer, a core layer, and a functional layer; The heat-sealing layer is composed of random copolymer polypropylene, ethylene-vinyl acetate copolymer, metallocene polyethylene, polybutene-1, hydrogenated styrene-butadiene block copolymer, antiblocking agent, slip agent, antioxidant, and ultraviolet absorber. The reinforcing layer is composed of isotactic polypropylene, glass fiber reinforced polypropylene, polybutylene terephthalate, liquid crystal polymer, maleic anhydride grafted polypropylene, antioxidant, and ultraviolet absorber. The core layer is composed of homopolymer polypropylene, nano-calcium carbonate, polyphenylene ether, EPDM rubber, maleic anhydride-grafted polyphenylene ether, silane coupling agent, nucleating agent, and lubricant. The functional layer is composed of polyvinylidene fluoride, polyimide, polyethersulfone, carbon nanotubes, polytetrafluoroethylene powder, antistatic agent, and flame retardant; The production method includes the following steps: (1) The raw materials for the heat-sealing layer, reinforcing layer, core layer and functional layer are blended separately and then sent to their respective extruders for melt mixing and plasticizing; (2) 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. (3) The sheet is attached to the cooling roller with an air knife and rapidly cooled to form an unshaped sheet. Then, after cooling in a water bath, the sheet is shaped to form a cast sheet. (4) The cast sheet is stretched to form a thin film; (5) The thickness of the film is detected by infrared light and the corresponding thickness deviation is fed back to the die head. The thickness deviation of the film is corrected by micro-adjusting the heating power of the bolts at the corresponding positions. (6) The product is wound up.

2. The method for producing an ultra-low temperature heat-sealed BOPP film according to claim 1, characterized in that: The components of the heat-sealing layer by mass ratio are: random copolymer polypropylene 33%, ethylene-vinyl acetate copolymer 22%, metallocene polyethylene 18%, polybutene-1 12%, hydrogenated styrene-butadiene block copolymer 8%, antiblocking agent 3%, slip agent 2%, antioxidant 1%, and ultraviolet absorber 1%.

3. The method for producing an ultra-low temperature heat-sealable BOPP film according to claim 2, characterized in that: The anti-blocking agent is silicon dioxide.

4. The method for producing an ultra-low temperature heat-sealable BOPP film according to claim 1, characterized in that: The components of the reinforcing layer by mass ratio are: isotactic polypropylene 42%, glass fiber reinforced polypropylene 25%, polybutylene terephthalate 15%, liquid crystal polymer 10%, maleic anhydride grafted polypropylene 5%, antioxidant 2%, and ultraviolet absorber 1%.

5. The method for producing an ultra-low temperature heat-sealable BOPP film according to claim 1, characterized in that: The core layer is composed of the following components by mass ratio: 54% homopolymer polypropylene, 15% nano-calcium carbonate, 15% polyphenylene ether, 8% EPDM rubber, 3% maleic anhydride-grafted polyphenylene ether, 2% silane coupling agent, 2% nucleating agent, and 1% lubricant.

6. The method for producing an ultra-low temperature heat-sealable BOPP film according to claim 1, characterized in that: The components of the functional layer by mass ratio are: 30% polyvinylidene fluoride, 25% polyimide, 20% polyethersulfone, 10% carbon nanotubes, 8% polytetrafluoroethylene micropowder, 4% antistatic agent, and 3% flame retardant.

7. The method for producing an ultra-low temperature heat-sealable BOPP film according to claim 6, characterized in that: The flame retardant is a mixture of melamine polyphosphate and aluminum hydroxide.