Highly antibacterial bopp film and method for preparing the same

Abstract

This invention discloses a high-antibacterial BOPP film and its preparation method, belonging to the field of BOPP film technology. The method includes the following steps: Step 1: Modified silica, polypropylene resin, antioxidant, lubricant, and light stabilizer are mixed evenly, dried, and then extruded and granulated using a twin-screw extruder, followed by casting to form a standard sample; Step 2: The standard sample is placed in the tensile fixture of a biaxial tensile testing machine for heated stretching to form a film, thus obtaining the high-antibacterial BOPP film. The preparation method provided by this invention not only improves the antibacterial effect of the film but also improves the compatibility between inorganic particles and the organic matrix. The resulting film has good mechanical properties and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of BOPP film technology, specifically, it relates to a high antibacterial BOPP film and its preparation method. Background Technology

[0002] Bis-oriented polypropylene (BOPP) film is widely used in the packaging of food, pharmaceutical, and cosmetic products due to its advantages such as light weight, excellent mechanical properties, good transparency, good electrical insulation, and ease of printing and lamination. However, during packaging and use, bacteria can easily grow and adhere to the film surface, potentially contaminating the packaged goods. Especially in humid environments, it can easily become a medium for the spread of germs, posing a potential threat to consumer health. Therefore, the development of BOPP films with antibacterial properties has become a research hotspot in the industry.

[0003] In existing technologies, a common method for imparting antibacterial properties to BOPP films is to add antibacterial agents, such as silver-based inorganic antibacterial agents or organic quaternary ammonium salt antibacterial agents, to the polypropylene matrix. While silver-based antibacterial agents offer good antibacterial effects, they suffer from high cost, easy oxidation and discoloration, poor dispersibility in the polymer matrix, and potential heavy metal migration risks. Organic quaternary ammonium salt antibacterial agents have attracted attention due to their rapid bactericidal speed and broad antibacterial spectrum, but they exhibit significant drawbacks in non-polar matrices like polypropylene: firstly, quaternary ammonium salts are polar substances with poor compatibility with polypropylene resins, and direct addition can easily lead to agglomeration in the matrix, causing processing problems such as crystal points and decreased mechanical properties in the film; secondly, small-molecule quaternary ammonium salt antibacterial agents are prone to migration and loss during film processing and use, resulting not only in poor antibacterial durability but also potential impacts on the film's appearance and food safety due to precipitation.

[0004] To address the issues of dispersion and compatibility of antibacterial agents in a matrix, existing technologies attempt to load antibacterial agents onto inorganic carriers. However, traditional physical adsorption or simple blending modification results in weak binding forces, and the antibacterial components still face the risk of desorption and migration, making it difficult to achieve long-lasting and stable antibacterial effects.

[0005] Therefore, how to provide a BOPP film that has both excellent and long-lasting antibacterial properties while maintaining good mechanical and processing properties is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high antibacterial BOPP film and its preparation method.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing a highly antibacterial BOPP film includes the following steps: Step 1: Mix the modified silica, polypropylene resin, antioxidant, lubricant and light stabilizer evenly, dry them, extrude and granulate them using a twin-screw extruder, and cast them into standard sample pieces. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film.

[0008] In a more optimized manner, the preparation process of the modified silica is as follows: A1: Under light-protected and nitrogen-protected conditions, silver nitrate aqueous solution was slowly added dropwise to sodium p-benzaldehyde-4-sulfonate aqueous solution. The mixture was stirred vigorously at room temperature for 1-2 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain product A. A2: Mix product A with anhydrous methanol, ultrasonically disperse for 10-12 min, add 1-hexadecyl-3-methylimidazolium bromide under nitrogen protection and light protection, and stir vigorously at room temperature for 2-3 h. After the reaction is completed, perform post-processing to obtain product B. A3: Disperse nano-silica in tetrahydrofuran, add γ-aminopropyltriethoxysilane, raise the temperature to 70-80℃ under a protective atmosphere, react for 3-4 hours, then wash the product and dry it under vacuum to obtain aminated silica. A4: Mix product B, aminated silica, and anhydrous ethanol, stir until homogeneous, add p-toluenesulfonic acid, raise the temperature to 80-90℃, react for 3-4 hours, after the reaction is complete, cool to room temperature, filter, wash, and dry to obtain modified silica.

[0009] The structure of product B is shown below: In a more optimized manner, the raw materials for preparing product A include the following components: by weight, 20-25 parts of silver nitrate aqueous solution and 15-20 parts of sodium p-benzaldehyde-4-sulfonate aqueous solution; wherein the concentration of the silver nitrate solution is 1.0 mol / L and the concentration of the sodium p-benzaldehyde-4-sulfonate solution is 1.0 mol / L.

[0010] In a more optimized manner, the raw materials for preparing product B include the following components: by weight, 10-15 parts of product A, 100-120 parts of anhydrous methanol, and 15-20 parts of 1-hexadecyl-3-methylimidazolium bromide.

[0011] In a more optimized manner, the raw materials for preparing the aminated nano-silica include the following components: by weight, 20-25 parts nano-silica, 200-250 parts tetrahydrofuran, and 15-20 parts γ-aminopropyltriethoxysilane.

[0012] In a more optimized manner, the raw materials for preparing the modified silica include the following components: by weight, 10-15 parts of product B, 25-30 parts of aminated silica, 200-250 parts of anhydrous ethanol, and 0.5-0.8 parts of p-toluenesulfonic acid.

[0013] In a more optimized manner, the raw materials for preparing the high antibacterial BOPP film include the following components: by weight, 3-8 parts modified silica, 80-100 parts polypropylene resin, 0.1-0.2 parts antioxidant, 0.1-0.5 parts lubricant, and 0.1-0.5 parts light stabilizer.

[0014] Ideally, the temperatures of each zone of the extruder are 170°C, 180°C, 190°C, 200°C, and 240°C.

[0015] Ideally, the preheating temperature of the tensile testing machine is 150℃, the tensile temperature is 160℃, the tensile ratio is 5×5, and the tensile rate is 300% / s.

[0016] The beneficial effects of this invention are: This invention successfully grafts imidazole quaternary ammonium salt antibacterial monomers with both aldehyde and sulfonic acid groups onto the surface of nano-silica via covalent bonding, thus preparing a modified silica antibacterial agent. This modification process fully utilizes the high specific surface area of ​​nano-silica as a carrier, effectively solving the problems of easy aggregation and poor compatibility of quaternary ammonium salt antibacterial agents in a polypropylene matrix.

[0017] Specifically, in the preparation of modified silica, firstly, sodium p-benzaldehyde-4-sulfonate is reacted with silver nitrate to generate silver p-benzaldehyde-4-sulfonate intermediate, which then undergoes anion exchange reaction with 1-hexadecyl-3-methylimidazolium bromide. The extremely low solubility product of silver bromide drives the reaction to proceed to completion, thereby obtaining an imidazolium quaternary ammonium salt monomer containing aldehyde functional groups. Subsequently, this monomer undergoes a condensation reaction between the aldehyde group and the amino group on the surface of aminated silica to form a stable carbon-nitrogen double bond, thus firmly loading the quaternary ammonium salt antibacterial component onto the silica surface through chemical bonding.

[0018] The resulting modified silica combines the rigidity of inorganic particles with the activity of organic antibacterial components. The long alkyl chains on its surface synergistically interact with quaternary ammonium cations to disrupt bacterial cell membrane integrity through electrostatic adsorption, thereby achieving highly efficient and broad-spectrum contact bactericidal performance. Simultaneously, because the antibacterial components are covalently grafted onto the silica surface, they are less prone to migration and loss during film processing and use, endowing the BOPP film with a long-lasting and stable antibacterial effect. Furthermore, the modified silica surface, due to the grafting of organic segments, improves its interfacial compatibility with polypropylene resin, allowing for uniform dispersion within the matrix during melt blending. This avoids film defects caused by inorganic particle agglomeration, thus enhancing antibacterial performance while maintaining the BOPP film's excellent mechanical properties and optical transparency. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A method for preparing a high antibacterial BOPP film, comprising the following steps: Step 1: Mix 3 parts modified silica, 80 parts polypropylene resin, 0.1 parts antioxidant 1010, 0.1 parts lubricant (calcium stearate), and 0.1 parts light stabilizer evenly. After drying, granulate the mixture using a twin-screw extruder, then cast it into standard sample sheets. The temperatures of each zone of the extruder are 170℃, 180℃, 190℃, 200℃, and 240℃. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film; the preheating temperature of the tensile testing machine is 150℃, the stretching temperature is 160℃, the stretching ratio is 5×5, and the stretching rate is 300% / s. The preparation process of modified silica is as follows: A1: Under light-protected and nitrogen-protected conditions, 20 parts of silver nitrate aqueous solution (1.0 mol / L) were slowly added dropwise to 15 parts of sodium p-benzaldehyde-4-sulfonate aqueous solution (1.0 mol / L). The mixture was stirred vigorously at room temperature for 1 hour. After the reaction was completed, the mixture was filtered, washed, and dried to obtain product A. A2: Mix 10 parts of product A and 100 parts of anhydrous methanol, ultrasonically disperse for 10 min, add 15 parts of 1-hexadecyl-3-methylimidazolium bromide under nitrogen protection and light protection, stir vigorously at room temperature for 2 h, and after the reaction is completed, perform post-processing to obtain product B; A3: 20 parts of nano-silica were dispersed in 200 parts of tetrahydrofuran, and 15 parts of γ-aminopropyltriethoxysilane were added. Under a protective atmosphere, the temperature was raised to 70°C and the reaction was carried out for 3 hours. The product was then washed and dried under vacuum to obtain aminated silica. A4: Mix 10 parts of product B, 25 parts of aminated silica, and 200 parts of anhydrous ethanol, stir well, add 0.5 parts of p-toluenesulfonic acid, raise the temperature to 80°C, react for 3 hours, after the reaction is complete, cool to room temperature, filter, wash, and dry to obtain modified silica.

[0021] Example 2: A method for preparing a high antibacterial BOPP film, comprising the following steps: Step 1: Mix 8 parts modified silica, 100 parts polypropylene resin, 0.2 parts antioxidant 1010, 0.5 parts lubricant (calcium stearate), and 0.5 parts light stabilizer evenly. After drying, granulate the mixture using a twin-screw extruder, then cast it into standard sample sheets. The temperatures of each zone of the extruder are 170℃, 180℃, 190℃, 200℃, and 240℃. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film; the preheating temperature of the tensile testing machine is 150℃, the stretching temperature is 160℃, the stretching ratio is 5×5, and the stretching rate is 300% / s. The preparation process of modified silica is as follows: A1: Under light-protected and nitrogen-protected conditions, 25 parts of silver nitrate aqueous solution (1.0 mol / L) were slowly added dropwise to 20 parts of sodium p-benzaldehyde-4-sulfonate aqueous solution (1.0 mol / L). The mixture was stirred vigorously at room temperature for 2 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain product A. A2: Mix 15 parts of product A and 120 parts of anhydrous methanol, ultrasonically disperse for 12 min, add 20 parts of 1-hexadecyl-3-methylimidazolium bromide under nitrogen protection and light protection, and stir vigorously at room temperature for 3 h. After the reaction is completed, post-process to obtain product B. A3: 25 parts of nano-silica were dispersed in 250 parts of tetrahydrofuran, and 20 parts of γ-aminopropyltriethoxysilane were added. Under a protective atmosphere, the temperature was raised to 80°C and the reaction was carried out for 4 hours. The product was then washed and dried under vacuum to obtain aminated silica. A4: Mix 15 parts of product B, 30 parts of aminated silica, and 250 parts of anhydrous ethanol, stir well, add 0.8 parts of p-toluenesulfonic acid, raise the temperature to 90°C, react for 4 hours, after the reaction is completed, cool to room temperature, filter, wash, and dry to obtain modified silica.

[0022] Example 3: A method for preparing a high antibacterial BOPP film, comprising the following steps: Step 1: Mix 5.5 parts modified silica, 90 parts polypropylene resin, 0.15 parts antioxidant 1010, 0.3 parts lubricant (calcium stearate), and 0.3 parts light stabilizer evenly. After drying, granulate the mixture using a twin-screw extruder, then cast it into standard sample sheets. The temperatures of each zone of the extruder are 170℃, 180℃, 190℃, 200℃, and 240℃. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film; the preheating temperature of the tensile testing machine is 150℃, the stretching temperature is 160℃, the stretching ratio is 5×5, and the stretching rate is 300% / s. The preparation process of modified silica is as follows: A1: Under light-protected and nitrogen-protected conditions, 22.5 parts of silver nitrate aqueous solution (1.0 mol / L) were slowly added dropwise to 17.5 parts of sodium p-benzaldehyde-4-sulfonate aqueous solution (1.0 mol / L). The mixture was stirred vigorously at room temperature for 1.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain product A. A2: Mix 12.5 parts of product A and 110 parts of anhydrous methanol, and ultrasonically disperse for 11 min. Under nitrogen protection and light protection, add 17.5 parts of 1-hexadecyl-3-methylimidazolium bromide. Stir vigorously at room temperature for 2.5 h. After the reaction is completed, perform post-processing to obtain product B. A3: 22.5 parts of nano-silica were dispersed in 225 parts of tetrahydrofuran, and 17.5 parts of γ-aminopropyltriethoxysilane were added. Under a protective atmosphere, the temperature was raised to 75°C and the reaction was carried out for 3.5 h. The product was then washed and dried under vacuum to obtain aminated silica. A4: Mix 12.5 parts of product B, 27.5 parts of aminated silica, and 225 parts of anhydrous ethanol, stir well, add 0.65 parts of p-toluenesulfonic acid, raise the temperature to 85°C, and react for 3.5 hours. After the reaction is complete, cool to room temperature, filter, wash, and dry to obtain modified silica.

[0023] Comparative Example 1: Silica was modified using only γ-aminopropyltriethoxysilane, as detailed below: Step 1: Mix 5.5 parts modified silica, 90 parts polypropylene resin, 0.15 parts antioxidant 1010, 0.3 parts lubricant (calcium stearate), and 0.3 parts light stabilizer evenly. After drying, granulate the mixture using a twin-screw extruder, then cast it into standard sample sheets. The temperatures of each zone of the extruder are 170℃, 180℃, 190℃, 200℃, and 240℃. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film; the preheating temperature of the tensile testing machine is 150℃, the stretching temperature is 160℃, the stretching ratio is 5×5, and the stretching rate is 300% / s. The preparation process of modified silica is as follows: 22.5 parts of nano silica are dispersed in 225 parts of tetrahydrofuran, 17.5 parts of γ-aminopropyltriethoxysilane are added, the temperature is raised to 75°C under a protective atmosphere, and the reaction is carried out for 3.5 hours. After that, the product is washed and vacuum dried to obtain modified silica.

[0024] Testing and experimentation: (1) In accordance with GB13022-91, the tensile strength of the high antibacterial BOPP film of the examples and comparative examples was tested using a universal tensile testing machine at a tensile rate of 200 mm / min. (2) Referring to QB / T2591, the antibacterial properties of the high antibacterial BOPP films of the examples and comparative examples were tested. The test strains were Escherichia coli and Staphylococcus aureus. The obtained data is shown in the table below: Conclusion: This invention successfully prepared a modified silica antibacterial agent by grafting imidazole quaternary ammonium salt antibacterial monomers containing aldehyde and sulfonic acid groups onto the surface of nano-silica, and applied it to the preparation of BOPP films. This modification method fully utilizes the high specific surface area of ​​nano-silica, solves the problems of easy aggregation and poor compatibility of quaternary ammonium salt antibacterial agents in polypropylene matrices, and simultaneously firmly loads the antibacterial components onto the silica surface through covalent bonds, endowing the film with durable and stable antibacterial properties.

[0025] Experimental results show that the high antibacterial BOPP film prepared by this invention maintains high tensile strength while achieving antibacterial rates of over 97% against Escherichia coli and Staphylococcus aureus, with a maximum of 99.9%, significantly better than the comparative example modified only with aminosilane. In summary, the preparation method provided by this invention not only improves the antibacterial effect of the film but also enhances the compatibility between inorganic particles and the organic matrix. The resulting film possesses excellent mechanical properties and has broad application prospects.

[0026] 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.

[0027] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a high antibacterial BOPP film, characterized in that, Includes the following steps: Step 1: Mix the modified silica, polypropylene resin, antioxidant, lubricant and light stabilizer evenly, dry them, extrude and granulate them using a twin-screw extruder, and then cast them into standard sample pieces. Step 2: Place the standard sample in the tensile fixture of the biaxial tensile testing machine for heating and stretching to form a film, thus obtaining a high antibacterial BOPP film.

2. The method for preparing a high antibacterial BOPP film according to claim 1, characterized in that, The preparation process of the modified silica is as follows: A1: Under light-protected and nitrogen-protected conditions, silver nitrate aqueous solution was slowly added dropwise to sodium p-benzaldehyde-4-sulfonate aqueous solution. The mixture was stirred vigorously at room temperature for 1-2 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain product A. A2: Mix product A with anhydrous methanol, ultrasonically disperse for 10-12 min, add 1-hexadecyl-3-methylimidazolium bromide under nitrogen protection and light protection, and stir vigorously at room temperature for 2-3 h. After the reaction is completed, perform post-processing to obtain product B. A3: Disperse nano-silica in tetrahydrofuran, add γ-aminopropyltriethoxysilane, raise the temperature to 70-80℃ under a protective atmosphere, react for 3-4 hours, then wash the product and dry it under vacuum to obtain aminated silica. A4: Mix product B, aminated silica, and anhydrous ethanol, stir until homogeneous, add p-toluenesulfonic acid, raise the temperature to 80-90℃, react for 3-4 hours, after the reaction is complete, cool to room temperature, filter, wash, and dry to obtain modified silica.

3. The method for preparing a high antibacterial BOPP film according to claim 2, characterized in that, The raw materials for preparing product A include the following components: by weight, 20-25 parts of silver nitrate aqueous solution and 15-20 parts of sodium p-benzaldehyde-4-sulfonate aqueous solution; wherein the concentration of the silver nitrate solution is 1.0 mol / L and the concentration of the sodium p-benzaldehyde-4-sulfonate solution is 1.0 mol / L.

4. The method for preparing a high antibacterial BOPP film according to claim 2, characterized in that, The raw materials for preparing product B include the following components: by weight, 10-15 parts of product A, 100-120 parts of anhydrous methanol, and 15-20 parts of 1-hexadecyl-3-methylimidazolium bromide.

5. The method for preparing a high antibacterial BOPP film according to claim 2, characterized in that, The raw materials for preparing the aminated nano-silica include the following components: by weight, 20-25 parts nano-silica, 200-250 parts tetrahydrofuran, and 15-20 parts γ-aminopropyltriethoxysilane.

6. The method for preparing a high antibacterial BOPP film according to claim 2, characterized in that, The raw materials for preparing the modified silica include the following components: by weight, 10-15 parts of product B, 25-30 parts of aminated silica, 200-250 parts of anhydrous ethanol, and 0.5-0.8 parts of p-toluenesulfonic acid.

7. The method for preparing a high antibacterial BOPP film according to claim 1, characterized in that, The raw materials for preparing the high antibacterial BOPP film include the following components: by weight, 3-8 parts modified silica, 80-100 parts polypropylene resin, 0.1-0.2 parts antioxidant, 0.1-0.5 parts lubricant, and 0.1-0.5 parts light stabilizer.

8. The method for preparing a high antibacterial BOPP film according to claim 1, characterized in that, The temperatures of each zone of the extruder are 170℃, 180℃, 190℃, 200℃, and 240℃.

9. The method for preparing a high antibacterial BOPP film according to claim 1, characterized in that, The preheating temperature of the tensile testing machine is 150℃, the tensile temperature is 160℃, the tensile ratio is 5×5, and the tensile rate is 300% / s.

10. The high antibacterial BOPP film obtained by the preparation method of a high antibacterial BOPP film according to any one of claims 1-9.

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