A high-transparency, low-haze BOPET film

Abstract

This invention discloses a high-transparency, low-haze BOPET film, belonging to the field of polyester film technology. It comprises a substrate layer and a functional surface layer. The substrate layer accounts for 80-90% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 73-85 parts polyethylene terephthalate resin, 0.5-0.9 parts nucleating agent, 1-2 parts anti-blocking agent, and 1.2-2.8 parts antioxidant. The functional surface layer accounts for 10-20% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 67-79 parts polyethylene terephthalate resin and 3-9 parts antibacterial agent. The nucleating agent reduces haze. The antibacterial agent consists of nano-zinc oxide and chloramine antibacterial agent, which improves the film's antibacterial properties and flexibility, and has a long antibacterial effect. Therefore, this invention solves the problem that traditional BOPET films cannot simultaneously achieve transparency, antibacterial properties, and flexibility, and has significant application value in the field of polyester film technology.

Description

Technical Field

[0001] This invention belongs to the field of polyester film technology, specifically, it relates to a high-transparency, low-haze BOPET film. Background Technology

[0002] Biaxially oriented polyester film (BOPET), as a high-performance polymer film material, plays a crucial role in many fields. It is made primarily from polyethylene terephthalate (PET) through a series of processes including crystallization drying, extrusion melting, casting, and biaxial stretching and orientation. BOPET film possesses numerous advantages such as high mechanical strength, good temperature resistance, excellent electrical insulation properties, and resistance to chemical corrosion, leading to its widespread application in packaging, electronics, and optics industries. For example, in the electronics field, ultra-thin BOPET film can serve as a substrate for flexible printed circuit boards (FPCs), meeting the trend towards thinner and smaller electronic devices, while its excellent insulation properties ensure the stable operation of electronic components. In the optics field, the high light transmittance and high gloss of some BOPET films make them ideal choices for polarizer protective films and release films for MLCCs (multilayer ceramic capacitors), strongly supporting the high-precision manufacturing of electronic components.

[0003] However, existing BOPET films still face several unresolved issues in practical applications. Regarding transparency, with continuous technological advancements and increasingly stringent requirements for product visual effects, existing BOPET films are insufficient for some high-end applications. For example, in high-end optical displays, extremely stringent requirements exist for film transparency and low haze. Ordinary BOPET films, due to their high haze, lead to decreased image clarity and color reproduction, impacting the visual experience. Furthermore, the rise of flexible electronics technology, such as the research and development of flexible displays and wearable electronic devices, places stringent demands on the tensile properties of BOPET films as flexible substrate materials. Existing BOPET films are prone to molecular chain breakage, thinning, and even rupture under certain stretching conditions, failing to guarantee the stability and reliability of flexible electronic devices during bending and folding, thus limiting their application. Finally, BOPET films lack antibacterial properties, allowing bacteria to easily proliferate on their surface, posing a health risk upon frequent contact with the human body. Current technologies often only address some of these issues, failing to address all simultaneously; typically, solving one problem exacerbates another. In conclusion, there is an urgent need to invent a BOPET film that can simultaneously solve the above problems in order to meet people's growing demand for high-quality products. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-transmittance, low-haze BOPET film.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A high-transparency, low-haze BOPET film includes a substrate layer and a functional surface layer;

[0007] The substrate layer accounts for 80-90% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 73-85 parts polyethylene terephthalate resin, 0.5-0.9 parts nucleating agent, 1-2 parts antiblocking agent, and 1.2-2.8 parts antioxidant.

[0008] The functional surface layer accounts for 10-20% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 67-79 parts polyethylene terephthalate resin and 3-9 parts antibacterial agent.

[0009] As a further technical solution, the nucleating agent is one of sodium benzoate, aluminum p-tert-butylbenzoate, and sorbitol derivatives.

[0010] As a further technical solution, the antioxidant is one of triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, pentaerythritol diphosphite (2,4-di-tert-butylphenyl) phosphite, and tris(nonylphenyl) phosphite.

[0011] As a further technical solution, the anti-blocking agent is one of erucamide, oleamide and stearamide.

[0012] As a further technical solution, the antibacterial agent is obtained by compounding nano-zinc oxide and chloramine antibacterial agent in a mass ratio of 1:2; wherein, the chloramine antibacterial agent is prepared through the following steps:

[0013] Step 1: In a three-necked round-bottom flask, add hydrochloric acid (37% by mass), p-hydroxybenzaldehyde and biuret in sequence. Stir mechanically at room temperature for 8-12 hours. After the reaction is complete, add ice water, wash with distilled water until pH≈5, filter, dry and recrystallize to obtain product A.

[0014] Step 2: In a three-necked round-bottom flask, add tetrahydrofuran, product A and stearoyl chloride in sequence, stir and mix, then add triethylamine and 4-dimethylaminopyridine as catalysts, stir evenly, heat to 40-60℃, keep the reaction at this temperature for 6-8 hours, after the reaction is complete, remove the solvent by rotary evaporation, and recrystallize with dichloromethane to obtain product B;

[0015] Step 3: In a three-necked round-bottom flask, add sodium hypochlorite solution (12% by mass) and product B in sequence. Stir mechanically at room temperature for 2-4 hours. Since the reaction is exothermic, no heating is required. After the reaction is complete, remove the solvent by rotary evaporation, purify by column chromatography, and finally dry under vacuum at 60℃-70℃ to obtain chloramine antibacterial agent.

[0016] As a further technical solution, the ratio of hydrochloric acid, p-hydroxybenzaldehyde, and biuret in step 1 is 95.1g:12.2g:10.3g.

[0017] As a further technical solution, in step 2, the ratio of tetrahydrofuran, product A, stearoyl chloride, triethylamine, and 4-dimethylaminopyridine is 150mL:20.7g:30.2g:10.2g:0.6g.

[0018] As a further technical solution, the ratio of sodium hypochlorite solution to product B in step 3 is 90 mL: 47.3 g.

[0019] From the preparation process: In step 1 of this invention, p-hydroxybenzaldehyde reacts with biuret to obtain product A. The hydroxyl group at one end of product A can react with stearoyl chloride to obtain product B. Finally, product B is chlorinated to obtain chloramine antibacterial agent.

[0020] From the perspective of the performance of chloramine antibacterial agents: chloramine antibacterial agents contain three chloramine antibacterial components, which can release active chlorine (Cl... + The antibacterial agent contains both sodium chloride and hypochlorous acid (HOCl), which destroy the cell structure and biomolecules of microorganisms, achieving broad-spectrum sterilization. Furthermore, the antibacterial agent also contains nano-zinc oxide, which releases Zn... 2+ Adsorbed onto bacterial cell membranes (negatively charged phospholipid bilayers), chloramine neutralizes surface charges, disrupting bacterial membrane stability. It can also bind to -SH, -COOH, and other groups in membrane proteins, causing protein denaturation and thus exerting an antibacterial effect. Therefore, chloramine antibacterial agents can synergistically enhance the antibacterial performance of membranes with nano-zinc oxide. Finally, by introducing a heptadecanyl long carbon chain into the chloramine antibacterial agent, the long chain and good flexibility not only improve the flexibility of the membrane, but its high hydrophobicity also improves the compatibility of the chloramine antibacterial agent with the polyester matrix, making the chloramine antibacterial agent more stable and prolonging the antibacterial effect.

[0021] The beneficial effects of this invention are:

[0022] Advantage 1: By adding nucleating agents such as sodium benzoate and sorbitol derivatives, the uniform crystallization of PET resin can be promoted, the formation of large-sized grains can be reduced, and the haze can be significantly reduced to meet the stringent requirements for transparency in the field of high-end optical displays.

[0023] Advantage 2: Homemade chloramine antibacterial agent. Chloramine antibacterial agent can not only work synergistically with nano zinc oxide to improve the antibacterial properties of the membrane, but also enhance the flexibility of the membrane. It also has good compatibility with the PET matrix, delays the migration of antibacterial components, and prolongs the antibacterial effect.

[0024] Advantage 3: The addition of anti-blocking agents can improve the surface smoothness and processability of the membrane;

[0025] Therefore, this invention solves the problem that traditional BOPET films cannot simultaneously achieve transparency, antibacterial properties, and flexibility, making it suitable for high-end markets with stringent requirements for optical and hygiene performance, and possessing significant application value in the field of polyester film technology. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] Example 1

[0029] Preparation of chloramine antibacterial agents:

[0030] Step 1: In a three-necked round-bottom flask, add 95.1g hydrochloric acid (37% by mass), 12.2g p-hydroxybenzaldehyde and 10.3g biuret in sequence. Stir mechanically at room temperature for 8 hours. After the reaction is complete, add ice water, wash with distilled water until pH≈5, filter, dry and recrystallize to obtain product A.

[0031] Step 2: In a three-necked round-bottom flask, add 150 mL of tetrahydrofuran, 20.7 g of product A and 30.2 g of stearoyl chloride in sequence. After stirring and mixing, add 10.2 g of triethylamine and 0.6 g of 4-dimethylaminopyridine as catalysts. After stirring evenly, heat to 40 °C and maintain the temperature for 6 h. After the reaction is complete, remove the solvent by rotary evaporation and recrystallize with dichloromethane to obtain product B.

[0032] Step 3: In a three-necked round-bottom flask, add 90 mL of sodium hypochlorite solution (12% by mass) and 47.3 g of product B in sequence. Stir the mixture mechanically at room temperature for 2 h. Since the reaction is exothermic, no heating is required. After the reaction is complete, remove the solvent by rotary evaporation, purify by column chromatography, and finally dry under vacuum at 60 °C to obtain the chloramine antibacterial agent.

[0033] Example 2

[0034] Preparation of chloramine antibacterial agents:

[0035] Step 1: In a three-necked round-bottom flask, add 190.2 g hydrochloric acid (37% by mass), 24.4 g p-hydroxybenzaldehyde and 20.6 g biuret in sequence. Stir mechanically at room temperature for 12 h. After the reaction is complete, add ice water, wash with distilled water until pH≈5, filter, dry and recrystallize to obtain product A.

[0036] Step 2: In a three-necked round-bottom flask, add 300 mL of tetrahydrofuran, 41.4 g of product A and 60.4 g of stearoyl chloride in sequence. After stirring and mixing, add 20.4 g of triethylamine and 1.2 g of 4-dimethylaminopyridine as catalysts. After stirring evenly, heat to 60 °C and maintain the temperature for 8 h. After the reaction is complete, remove the solvent by rotary evaporation and recrystallize with dichloromethane to obtain product B.

[0037] Step 3: In a three-necked round-bottom flask, add 180 mL of sodium hypochlorite solution (12% by mass) and 94.6 g of product B in sequence. Stir mechanically at room temperature for 4 h. Since the reaction is exothermic, no heating is required. After the reaction is complete, remove the solvent by rotary evaporation, purify by column chromatography, and finally dry under vacuum at 70 °C to obtain the chloramine antibacterial agent.

[0038] Example 3

[0039] Preparation of high-transmittance, low-haze BOPET film:

[0040] S1. The polyethylene terephthalate resin is vacuum dried at 100℃ for 4 hours, and the moisture content is controlled at ≤50ppm to prevent hydrolysis and degradation during melt processing.

[0041] S2. Mix 73g of dried polyethylene terephthalate resin, 0.5g of sodium benzoate, 1g of erucamide and 1.2g of triphenyl phosphite to obtain the substrate layer raw material;

[0042] S3. Mix 67g of dried polyethylene terephthalate resin, 1g of nano zinc oxide and 2g of chloramine antibacterial agent prepared in Example 1 to obtain functional surface layer raw material;

[0043] S4. The substrate layer material and the functional surface layer material are added to the twin-screw extruder for melting, and then co-extruded through the co-extrusion die at a ratio of 90:10. After rapid cooling, the material is biaxially stretched and heat-set, and then wound up to obtain a high-transparency, low-haze BOPET film.

[0044] Example 4

[0045] Preparation of high-transmittance, low-haze BOPET film:

[0046] S1. The polyethylene terephthalate resin is vacuum dried at 120℃ for 6 hours, and the moisture content is controlled at ≤50ppm to prevent hydrolysis and degradation during melt processing.

[0047] S2. Mix 79g of dried polyethylene terephthalate resin, 0.7g of sorbitol derivative (DBS), 1.5g of oleamide and 2.0g of tris(2,4-di-tert-butylphenyl) phosphite to obtain the substrate layer raw material;

[0048] S3. Mix 73g of dried polyethylene terephthalate resin, 2g of nano zinc oxide and 4g of chloramine antibacterial agent prepared in Example 1 to obtain functional surface layer raw material;

[0049] S4. The substrate layer material and the functional surface layer material are added to a twin-screw extruder for melting and then co-extruded through a co-extrusion die at a ratio of 85:15. After rapid cooling, the material is biaxially stretched and heat-set, and then wound up to obtain a high-transparency, low-haze BOPET film.

[0050] Example 5

[0051] Preparation of high-transmittance, low-haze BOPET film:

[0052] S1. The polyethylene terephthalate resin is vacuum dried at 120℃ for 6 hours, and the moisture content is controlled at ≤50ppm to prevent hydrolysis and degradation during melt processing.

[0053] S2. Mix 85g of dried polyethylene terephthalate resin, 0.9g of sorbitol derivative (DBS), 2g of stearamide and 2.8g of tri(nonylphenyl) phosphite to obtain the substrate layer raw material;

[0054] S3. Mix 79g of dried polyethylene terephthalate resin, 3g of nano zinc oxide and 6g of chloramine antibacterial agent prepared in Example 1 to obtain functional surface layer raw material;

[0055] S4. The substrate layer material and the functional surface layer material are added to the twin-screw extruder for melting, and then co-extruded through the co-extrusion die at a ratio of 80:20. After rapid cooling, the material is biaxially stretched and heat-set, and then wound up to obtain a high-transparency, low-haze BOPET film.

[0056] Comparative Example 1

[0057] Using 9g of chloramine-T as an antibacterial agent to replace the nano zinc oxide and the chloramine antibacterial agent prepared in Example 1 in Example 5, the remaining steps were the same as in Example 5, and a BOPET film was obtained.

[0058] Comparative Example 2

[0059] BOPET film produced by Xiongxian Aote Packaging Materials Co., Ltd. was used.

[0060] The following performance tests were conducted on Examples 3, 4, and 5, and on Examples 1 and 2:

[0061] According to ISO 178:2019 standard, the flexural modulus is measured. The higher the flexural modulus, the stronger the rigidity of the film and the worse its flexibility.

[0062] Transmittance and haze were measured according to GB / T 2410-2008 standard;

[0063] The antibacterial properties were determined according to GB / T 31402-2015 standard, using Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538).

[0064] The BOPET films of Examples 3, 4, 5 and Comparative Example 1 were washed with water 30 times and their antibacterial properties were determined using the same standard.

[0065]

[0066] As can be seen from the table above, the antibacterial properties and flexibility of the embodiments of the present invention are higher than those of the comparative example after the addition of antibacterial agents, with less impact on the transparency of the film. Furthermore, the antibacterial properties remain stable after 30 washes and the antibacterial lifespan is longer. Therefore, the present invention is suitable for high-end markets with stringent requirements for optical and hygienic performance and has important application value in the field of polyester film technology.

[0067] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A high-transmittance, low-haze BOPET film, comprising a substrate layer and a functional surface layer, characterized in that, The functional surface layer accounts for 10-20% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 67-79 parts polyethylene terephthalate resin and 3-9 parts antibacterial agent. The antibacterial agent is obtained by compounding nano-zinc oxide and chloramine antibacterial agent in a mass ratio of 1:2; wherein the chloramine antibacterial agent is prepared through the following steps: Step 1: In a flask, add hydrochloric acid, p-hydroxybenzaldehyde and biuret in sequence. Stir the mixture at room temperature for 8-12 hours until the reaction is complete. After post-processing, obtain product A. Step 2: In a flask, add tetrahydrofuran, product A and stearoyl chloride in sequence, stir and mix, then add triethylamine and 4-dimethylaminopyridine, stir evenly, and react at 40-60℃ for 6-8 hours. After the reaction is complete, perform post-processing to obtain product B. Step 3: Add sodium hypochlorite solution and product B to the flask in sequence. Stir mechanically at room temperature for 2-4 hours until the reaction is complete. After post-processing, obtain chloramine antibacterial agent.

2. The high-transmittance, low-haze BOPET film according to claim 1, characterized in that, In step 1, the ratio of hydrochloric acid, p-hydroxybenzaldehyde, and biuret is 95.1g:12.2g:10.3g.

3. The high-transmittance, low-haze BOPET film according to claim 1, characterized in that, In step 2, the ratio of tetrahydrofuran, product A, stearoyl chloride, triethylamine, and 4-dimethylaminopyridine is 150 mL: 20.7 g: 30.2 g: 10.2 g: 0.6 g.

4. The high-transmittance, low-haze BOPET film according to claim 1, characterized in that, In step 3, the ratio of sodium hypochlorite solution to product B is 90 mL: 47.3 g.

5. The high-transmittance, low-haze BOPET film according to claim 1, characterized in that, The substrate layer accounts for 80-90% of the total mass of the BOPET film and is composed of the following raw materials in parts by weight: 73-85 parts polyethylene terephthalate resin, 0.5-0.9 parts nucleating agent, 1-2 parts anti-blocking agent, and 1.2-2.8 parts antioxidant.

6. The high-transmittance, low-haze BOPET film according to claim 5, characterized in that, The nucleating agent is one of sodium benzoate, aluminum p-tert-butylbenzoate, and sorbitol derivatives.

7. The high-transmittance, low-haze BOPET film according to claim 5, characterized in that, The antioxidant is one of triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, pentaerythritol diphosphite (2,4-di-tert-butylphenyl) phosphite, and tris(nonylphenyl) phosphite.

8. The high-transmittance, low-haze BOPET film according to claim 5, characterized in that, The anti-blocking agent is one of erucamide, oleamide, and stearamide.

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