Preparation process of bacteriostatic PET (Polyethylene Terephthalate) film

Abstract

The invention relates to the technical field of high polymer materials, in particular to a preparation process of a bacteriostatic PET film. According to the invention, the defects of poor antibacterial property and poor oil stain resistance of the existing PET film are overcome. The modified PET master batch, the composite antibacterial agent, the nano filler, the modified polydimethylsiloxane, the coupling agent, the flame retardant and the ultraviolet light absorber are subjected to melt blending, extrusion and casting to obtain a film sheet; the film sheet is subjected to biaxial directional stretching, thermal stabilization treatment and hot press polishing treatment, and the antibacterial PET film is obtained. The PET master batch is prepared from pretreated PET resin and PET resin; the composite antibacterial agent comprises a rosemary extract and dodecyl dimethyl benzyl ammonium chloride; the nano filler is prepared from nano silicon dioxide, silver nitrate and the like; the modified polydimethylsiloxane is prepared from hydrogen-containing silicone oil and allyl polyether. The PET film prepared by the invention has strong antibacterial property and good oil stain resistance, and is suitable for coating kitchen ware.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a preparation process of an antibacterial PET film. Background Art

[0002] Polyethylene terephthalate (PET), as a thermoplastic polyester with excellent comprehensive properties, is widely used in the field of film preparation due to its outstanding mechanical strength, dimensional stability and good processability. It is widely used in packaging, electronics, architectural decoration and other industries.

[0003] However, unmodified PET has obvious performance defects. Its surface is highly chemically inert and easily forms a breeding ground for bacteria in a humid environment or under long-term contact with organic matter. At the same time, in complex environments such as oil smoke and oil stains, the interaction between PET and oil molecules makes its surface extremely easy to be contaminated and difficult to clean.

[0004] Existing technologies often use copolymerization and blending modification techniques to optimize the performance of PET. Copolymerization modification improves PET's performance at the molecular chain structure level by introducing functional monomers into the polymerization reaction. However, this method is plagued by complex synthesis processes, harsh reaction conditions, and high production costs. In contrast, blending modification involves physically mixing additives or polymers with antimicrobial and anti-oil properties with the PET matrix without altering the PET molecular chain structure. This method offers significant advantages such as simple processing, rapid formulation adjustments, and manageable costs. It can more flexibly and efficiently impart antimicrobial and anti-oil properties to PET. Despite extensive research, PET prepared by existing modification methods still has deficiencies in antimicrobial durability and anti-oil capabilities, making it difficult to meet the needs of applications such as food packaging and kitchenware, which require high hygiene and easy cleanability. Therefore, developing a PET material with both high antimicrobial and excellent anti-oil properties, as well as stable and long-lasting performance, has become an important research direction.

[0005] Therefore, a preparation process of antibacterial PET film was proposed. Summary of the Invention

[0006] The present invention aims to provide a process for preparing an antibacterial PET film. The process comprises melt-blending and extruding a modified PET masterbatch, a composite antibacterial agent, a nanofiller, a modified polydimethylsiloxane, a coupling agent, a flame retardant, and a UV absorber to produce a film sheet; the film sheet is then subjected to biaxial orientation, heat stabilization, and thermal calendering to produce the antibacterial PET film. The PET masterbatch is prepared from pretreated PET resin and PET resin; the composite antibacterial agent includes rosemary extract and dodecyldimethylbenzylammonium chloride; the nanofiller is prepared from nanosilica, silver nitrate, and the like; and the modified polydimethylsiloxane is prepared from hydrogenated silicone oil and allyl polyether. The PET film produced by the present invention has strong antibacterial and oil-resistant properties and is suitable for coating kitchenware.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation process of an antibacterial PET film, which specifically comprises the following steps:

[0009] The modified PET masterbatch, composite antibacterial agent, nanofiller, modified polydimethylsiloxane, coupling agent, flame retardant and ultraviolet absorber are melt-blended and extruded to obtain a film sheet; the film sheet is subjected to biaxial orientation stretching, heat stabilization treatment and hot calendering treatment to obtain an antibacterial PET film;

[0010] The modified PET masterbatch is prepared from pretreated PET resin, PET resin and perfluoropolyether diol; the pretreated resin is prepared from PET resin by hydrolysis; the composite antibacterial agent includes rosemary extract and dodecyldimethylbenzylammonium chloride; the rosemary extract is prepared from rosemary by an extraction method; the nanofiller is prepared from nano-silicon dioxide, γ-methacryloyloxypropyltrimethoxysilane and silver nitrate; and the modified polydimethylsiloxane is prepared from hydrogen-containing silicone oil and allyl polyether.

[0011] Preferably, the modified PET masterbatch is prepared by mixing a pretreated PET resin and a PET resin in a weight ratio of 1.5-2.5:7.5-8.5 to obtain a mixture, adding 4-5% by weight of a perfluoropolyether diol to the mixture, and then melt-extruding and pelletizing the mixture; wherein the pretreated PET resin is prepared by constant temperature treatment of the PET resin at a relative humidity of 65-75% for 3.5-4.5 hours and then drying the obtained mixture; and the intrinsic viscosity of the PET resin is 0.65-0.75 dL / g.

[0012] Preferably, the composite antibacterial agent is prepared from rosemary extract and dodecyldimethylbenzyl ammonium chloride in a weight ratio of 1-1.5:1, wherein the preparation method of the rosemary extract is: mixing rosemary with a 70% ethanol aqueous solution in a weight ratio of 1:10, and soaking in a 90°C water bath for 5 hours; filtering to separate the soaking liquid and soaking residue; drying the soaking residue; reflux distilling the dried soaking residue with anhydrous ethanol in a weight ratio of 1:7 for 1.5-2.5 hours; separating to obtain a distillate and a distillation residue; combining the soaking liquid and the distillate; and concentrating the combined liquid by reduced pressure evaporation to 5-7% of the original volume to obtain the rosemary extract.

[0013] Preferably, the preparation method of the nanofiller is: ultrasonically dispersing nano-silica in an ethanol solution, adding a silane coupling agent and reacting at a constant temperature for 2.5-3.5 hours to obtain pretreated nano-silica; ultrasonically dispersing the pretreated nano-silica in a 5-7wt% silver nitrate aqueous solution, adding sodium citrate and reacting for 2-2.5 hours to obtain the nanofiller.

[0014] Preferably, the preparation method of modified polydimethylsiloxane is: mixing hydrogenated silicone oil, allyl polyether and toluene; heating to 95°C and maintaining nitrogen protection; adding platinum carbon catalyst dropwise; stirring and reacting at 95°C for 4-5 hours, then cooling to room temperature, filtering and vacuum distilling the filtrate to obtain modified polydimethylsiloxane; the number average molecular weight of the allyl polyether is 1000-2000.

[0015] Preferably, the preparation method of the film sheet is as follows: by weight, modified PET masterbatch, 6-8 parts of nanofiller, 4-5 parts of modified polydimethylsiloxane, coupling agent, ultraviolet absorber, and flame retardant are mixed and added to a twin-screw extruder for melt blending, and 5-7 parts of composite antibacterial agent are added in the fourth zone of the twin-screw extruder.

[0016] Preferably, the working conditions of the twin-screw extruder are: the processing temperature of the first zone of the screw extruder is 250-255°C, the processing temperature of the second and third zones is 255-265°C, the processing temperature of the fourth and fifth zones is 250-260°C, the die processing temperature is 250-260°C, and the screw speed is 250-350rpm.

[0017] Preferably, the biaxial stretching method is: the transverse stretching temperature is 90-110° C., and the transverse stretching ratio is 3-4 times; the longitudinal stretching temperature is 90-110° C., and the longitudinal stretching ratio is 3-4 times.

[0018] Preferably, the conditions for the hot calendering treatment are: a calendering temperature of 180-220° C., and a pressure of 10-20 kN / m.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses an organic-inorganic composite synergistic system consisting of rosemary extract, dodecyldimethylbenzyl ammonium chloride, and nanofillers to provide broad-spectrum, highly efficient, instantaneous, and long-lasting silver ion antibacterial functions. The antioxidant effect of rosemary can protect the nanosilver in the system from oxidation and maintain its activity. Dodecyldimethylbenzyl ammonium chloride synergistically broadens the antibacterial spectrum and improves instantaneous efficiency, while the nanofillers provide long-lasting inorganic antibacterial effects by slowly releasing silver ions. Silver-loaded nanosilica is anchored to the matrix via γ-methacryloyloxypropyltrimethoxysilane coupling, ensuring its uniform dispersion and sustained release, significantly improving the duration and durability of the antibacterial effect.

[0021] 2. In the present invention, excellent and durable anti-oil and easy-to-clean functions are achieved through the synergistic effect of fluorine-containing modification of the matrix and additives. PET resin is grafted with perfluoropolyether segments, which impart anti-oil capabilities at the molecular level and preferentially accumulate on the surface. Polyether-modified polydimethylsiloxane synergistically provides low surface energy and slipperiness to jointly construct an extremely low surface energy layer, significantly reducing oil adhesion and providing easy-to-wipe properties. Nanofillers, as multifunctional fillers, enhance the hardness and wear resistance of the membrane material as a whole and on the surface, helping to support the anti-oil surface layer and reduce performance degradation caused by wear. Covalent fixation of fluorine-containing segments enhances anti-oil durability.

[0022] 3. This invention utilizes a nanoparticle reinforcement and lubrication-based wear reduction technology to achieve excellent and durable wear resistance. The high-hardness nanofiller resists cutting and scratching, while the polyether-modified polydimethylsiloxane provides lubrication and wear reduction, creating a synergistic composite wear-resistant system. Silver-loaded nanosilica is firmly anchored to the matrix via γ-methacryloxypropyltrimethoxysilane coupling, ensuring the nanoparticles effectively bear the load without falling off, significantly enhancing the durability of the wear resistance provided by the nanoparticles and lubricant.

[0023] 4. In the present invention, part of the PET resin is pretreated by hydrolysis and reacted with untreated PET resin and perfluoropolyether diol for extrusion to prepare a fluorine-containing modified matrix; all components are mixed by co-extrusion, and the activity and dispersibility of the antibacterial substance are guaranteed by optimizing the temperature, shear rate, and the late addition of heat-sensitive antibacterial substances; stretching and heat setting give the body strength, toughness and dimensional stability, enhance the matrix support, and improve the mechanical and wear resistance; hot calendering increases the surface density and smoothness, strongly promotes the surface enrichment and physical locking of functional components, and each process and component synergistically improves the antibacterial performance, anti-oil performance, wear resistance, and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of wear resistance retention rate of Example 1, Example 4, Examples 6-7 and Comparative Example 3, Comparative Example 5, Comparative Example 12, Comparative Examples 14-15, and Comparative Example 17 of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a preparation process of an antibacterial PET film, and the technical solution is as follows:

[0027] Example 1

[0028] Preparation of modified PET masterbatch

[0029] The pretreated PET resin and the PET resin are mixed in a weight ratio of 1.5:8.5 to obtain a mixture, and then 4% by weight of perfluoropolyether diol is added to the mixture, followed by melt extrusion and pelletizing. The processing temperature of the screw extruder zone 1 is set to 270°C, the processing temperature of the second zone is set to 275°C, the processing temperature of the third zone is set to 275°C, the processing temperature of the fourth zone is set to 265°C, the processing temperature of the fifth zone is set to 265°C, the processing temperature of the die head is set to 250°C, and the screw speed is 150 rpm. The preparation method of the pretreated PET resin is as follows: the PET resin is constant-temperature treated at a relative humidity of 65% for 3.5 hours and then dried to obtain the mixture, and the intrinsic viscosity of the PET resin is 0.75 dL / g.

[0030] The composite antibacterial agent is prepared from rosemary extract and dodecyldimethylbenzyl ammonium chloride in a weight ratio of 1:1. The preparation method of the rosemary extract is as follows: rosemary is mixed with a 70% ethanol aqueous solution in a weight ratio of 1:10, and the mixture is soaked in a 90°C water bath for 5 hours; the soaking liquid and soaking residue are separated by filtration; the soaking residue is dried; the dried soaking residue is refluxed and distilled with anhydrous ethanol in a weight ratio of 1:7 for 1.5 hours; a distillate and a distillation residue are separated; the soaking liquid and the distillate are combined; and the combined liquid is concentrated by reduced pressure evaporation to 5% of the original volume to obtain the rosemary extract.

[0031] Preparation of nanofillers

[0032] The nano-silica was ultrasonically dispersed in an ethanol solution, and a silane coupling agent was added and reacted for 2.5 hours to obtain pretreated nano-silica; the pretreated nano-silica was ultrasonically dispersed in a 5wt% silver nitrate aqueous solution, and sodium citrate was added and reacted for 2 hours to obtain a nano-filler.

[0033] Preparation of modified polydimethylsiloxane

[0034] 100 parts of hydrogenated silicone oil (hydrogen content 1.58-1.60%, viscosity 20-30 mm at 25°C) 2 / s), 50 parts of allyl polyether and 100 parts of toluene; heated to 95°C under nitrogen protection; 0.3 parts of platinum-carbon catalyst were added dropwise; the mixture was stirred at 95°C for 4 hours and then cooled to room temperature. The filtrate was filtered and vacuum distilled to obtain modified polydimethylsiloxane; the number average molecular weight of the allyl polyether was 1000.

[0035] Preparation of thin film sheets

[0036] By weight, 100 parts of PET masterbatch, 6 parts of nanofiller, 4 parts of modified polydimethylsiloxane, 1.5 parts of coupling agent γ-methacryloxypropyltrimethoxysilane, 1.5 parts of ultraviolet absorber 2-(2H-benzotriazole-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol, and 1 part of flame retardant magnesium hydroxide were mixed and added to a twin-screw extruder for melt blending. 5 parts of composite antibacterial agent were added in the fourth zone of the twin-screw extruder.

[0037] The working conditions of the twin-screw extruder are as follows: the processing temperature of the first zone of the screw extruder is 250°C, the processing temperature of the second and third zones is 255°C, the processing temperature of the fourth and fifth zones is 260°C, the processing temperature of the die head is 255°C, and the screw speed is 250rpm.

[0038] The biaxial stretching method is as follows: the transverse stretching temperature is 90°C and the transverse stretching ratio is 3 times; the longitudinal stretching temperature is 90°C and the longitudinal stretching ratio is 3 times.

[0039] The conditions for the hot calendering treatment were as follows: a calendering temperature of 180° C. and a pressure of 10 kN / m.

[0040] The difference between Example 2 and Example 1 is that the weight ratio of rosemary extract to dodecyldimethylbenzyl ammonium chloride in the preparation of the composite antibacterial agent is 1.2:1, the reflux distillation time for the preparation of the rosemary extract is 2 hours, the concentration multiple of the rosemary extract is 6%, the silver-loaded reaction time for the nanofiller preparation is 2.3 hours, the concentration of the silver nitrate aqueous solution in the nanofiller preparation is 6wt%, and the amount of the composite antibacterial agent added to the film formula is 6 parts.

[0041] The difference between Example 3 and Example 1 is that the weight ratio of rosemary extract to dodecyldimethylbenzyl ammonium chloride in the preparation of the composite antibacterial agent is 1.5:1, the reflux distillation time for the preparation of the rosemary extract is 2.5 hours, the concentration multiple of the rosemary extract is 7%, the silver-loaded reaction time for the nanofiller preparation is 2.5 hours, the concentration of the silver nitrate aqueous solution in the nanofiller preparation is 7wt%, and the amount of the composite antibacterial agent added to the film formula is 7 parts.

[0042] The difference between Example 4 and Example 2 is that the number average molecular weight of the modified polydimethylsiloxane used to prepare the allyl polyether is 1500, the stirring reaction time for the modified polydimethylsiloxane preparation is 4.5 hours, and the amount of modified polydimethylsiloxane added to the film formulation is 4.5 parts.

[0043] The difference between Example 5 and Example 2 is that the number average molecular weight of the modified polydimethylsiloxane used to prepare the allyl polyether is 2000, the stirring reaction time for the modified polydimethylsiloxane preparation is 5 hours, and the amount of modified polydimethylsiloxane added to the film formulation is 5 parts.

[0044] The difference between Example 6 and Example 4 is that the reaction time of the nano-silica pretreatment for preparing the nano-filler is 3 hours, and the amount of the nano-filler added in the film formulation is 7 parts.

[0045] The difference between Example 7 and Example 4 is that the reaction time of the nano-silica pretreatment for preparing the nano-filler is 3.5 hours, and the amount of the nano-filler added in the film formulation is 8 parts.

[0046] The difference between Example 8 and Example 6 is that the weight ratio of pretreated PET to PET resin in the modified PET masterbatch is 2:8, the preparation humidity of the pretreated PET resin is 70% relative humidity, the preparation time of the pretreated PET resin is 4 hours, the film blending extrusion working temperature is 255°C in zone 1, 260°C in zone 2 and zone 3, and the die head in zone 4 and zone 5 is 255°C, the film blending extrusion screw speed is 300 rpm, the biaxial orientation stretching temperature is 100°C in the transverse / longitudinal direction, the biaxial orientation stretching ratio is 3.5 times in the transverse / longitudinal direction, the hot calendering treatment temperature is 200°C, and the hot calendering treatment pressure is 15 kN / m.

[0047] The difference between Example 9 and Example 6 is that the weight ratio of pretreated PET to PET resin in the modified PET masterbatch is 2.5:8.5, the preparation humidity of the pretreated PET resin is 75% relative humidity, the preparation time of the pretreated PET resin is 4.5 hours, the film blending extrusion working temperature is 255°C in zone 1, 265°C in zones 2 and 3, and 260°C in the die head of zones 4 and 5, the film blending extrusion screw speed is 350rpm, the biaxial orientation stretching temperature is 110°C in the transverse / longitudinal direction, the biaxial orientation stretching ratio is 4 times in the transverse / longitudinal direction, the hot calendering treatment temperature is 220°C, and the hot calendering treatment pressure is 20 kN / m.

[0048] The only difference between Comparative Example 1 and Example 1 is that no rosemary extract is added.

[0049] The only difference between Comparative Example 2 and Example 1 is that dodecyldimethylbenzyl ammonium chloride is not added.

[0050] The only difference between Comparative Example 3 and Example 1 is that no nanofiller is added.

[0051] The only difference between Comparative Example 4 and Example 1 is that the composite antibacterial agent is added in the second zone of the twin-screw extruder.

[0052] The only difference between Comparative Example 5 and Example 1 is that the screw speed of the twin-screw extruder is 150 rpm.

[0053] The only difference between Comparative Example 6 and Example 1 is that the processing temperature of the twin-screw extruder zone 1 is 275°C, the processing temperature of zones 2 and 3 is 280°C, the processing temperature of zones 4 and 5 is 270°C, and the die processing temperature is 255°C.

[0054] The only difference between Comparative Example 7 and Example 1 is that nano-silicon dioxide is not subjected to silver loading treatment to prepare nano-filler, but nano-silicon dioxide is directly used to replace the nano-filler, and nano-silver is directly added during the blending process.

[0055] The only difference between Comparative Example 8 and Example 1 is that PET masterbatch without any treatment is used instead of the modified PET masterbatch.

[0056] The only difference between Comparative Example 9 and Example 1 is that no perfluoropolyether diol is added during the preparation of the modified PET masterbatch.

[0057] The only difference between Comparative Example 10 and Example 1 is that the PET resin is not pretreated, but the PET resin is reacted with perfluoropolyether diol to prepare a modified PET masterbatch.

[0058] The only difference between Comparative Example 11 and Example 1 is that when preparing the film sheet, a mixture of PET resin and perfluoropolyether diol is used instead of the modified PET resin.

[0059] The only difference between Comparative Example 12 and Example 1 is that modified polydimethylsiloxane is not added.

[0060] The only difference between Comparative Example 13 and Example 1 is that hydrogenated silicone oil is used instead of modified polydimethylsiloxane when preparing the modified PET masterbatch.

[0061] The only difference between Comparative Example 14 and Example 1 is that when preparing the nanofiller, the nano-silica is not modified with γ-methacryloxypropyltrimethoxysilane.

[0062] The only difference between Comparative Example 15 and Example 1 is that in the biaxial directional stretching process, the transverse and longitudinal stretching ratios are both 5 times.

[0063] The only difference between Comparative Example 16 and Example 1 is that the weight ratio of pretreated PET to PET resin in the modified PET masterbatch is 4:6.

[0064] The only difference between Comparative Example 17 and Example 1 is that the hot calendering process is removed.

[0065] Test Example 1

[0066] Test objects: Antibacterial tests were performed on the films prepared in Examples 1-3, Comparative Examples 1-7, and Comparative Example 17 before and after aging.

[0067] Test method: E. coli was used as the test strain, and the aging method was PCT 72h aging. The final test results are shown in Table 1.

[0068] Table 1 Antibacterial performance test results

[0069]

[0070]

[0071] Comparative Example 1 omitted rosemary extract, resulting in a composite antibacterial system lacking natural broad-spectrum antibacterial components, weakening the composite system's ability to kill certain bacterial species. Furthermore, the absence of antioxidants in rosemary extract reduced the protective effect of nanosilver, affecting the activity and long-term release of nanosilver. Comparative Example 2 omitted dodecyldimethylbenzyl ammonium chloride, resulting in a composite antibacterial system lacking the antibacterial activity of a cationic surfactant, reducing the composite system's instantaneous antibacterial efficiency and antibacterial spectrum. Although other components still possessed antibacterial activity, the overall antibacterial function was incomplete. Comparative Example 3 omitted the addition of nanofillers, resulting in the film losing the long-lasting inorganic antibacterial function provided by nanosilver. Although the organic antibacterial agent provided some antibacterial activity, these components were easily degraded, resulting in a film lacking sustained antibacterial capacity and a significant decline in antibacterial performance after aging. Comparative Example 4 added the composite antibacterial agent in the second zone ahead of time, prolonging the residence time of the heat-sensitive organic antibacterial component in the high-temperature melt, leading to thermal decomposition and degradation of its active ingredients, reducing the initial antibacterial activity of the composite antibacterial system. Comparative Example 5 used a lower screw speed, which prolonged the material's residence time in the high-temperature region and increased the heating time of the heat-sensitive organic antimicrobial components, promoting their decomposition and loss, thereby affecting the antimicrobial activity and durability of the composite antimicrobial system. Comparative Example 6 used an excessively high extrusion temperature, which accelerated the decomposition of the organic components in the composite antimicrobial agent, rendering a large number of active ingredients ineffective and significantly reducing the antimicrobial performance of the composite antimicrobial system. Comparative Example 7 added nanosilver directly without silver-loading the nanosilica. Lacking the fixation and protection of the nanocarrier, the nanosilver easily aggregated, oxidized, and lost, preventing slow release. This resulted in significantly lower long-term antimicrobial activity and durability than the silver-loaded nanofiller. Comparative Example 17 eliminated the hot calendering process, resulting in a lack of physical densification of the film surface and physical locking of the near-surface antimicrobial components and silver-loaded nanosilica. These functional components were prone to shedding and loss during use. Although the components themselves were active, the surface functional layer was damaged, significantly reducing antimicrobial durability.

[0072] A comprehensive analysis of the first group of comparative examples shows that the integrity of the components of the composite antibacterial system and the protection of the activity of these components by process control and their fixation on the surface microstructure are crucial to achieving efficient and long-lasting antibacterial performance. The failure to add rosemary extract, dodecyldimethylbenzyl ammonium chloride or nanofillers directly weakens the antibacterial ability and long-term effectiveness of the composite system. In particular, nanofillers are the key to long-lasting inorganic antibacterial and carrier anchoring. In terms of process, high temperature, long residence time or early addition of heat-sensitive components will lead to their thermal decomposition, which directly reduces the antibacterial activity. If nanosilver is not silver-loaded, the stable release and fixation of nanosilver cannot be achieved, resulting in the failure of long-term antibacterial performance. Removing hot calendering destroys the physical locking of surface functional components, affecting antibacterial durability. These comparative examples show that through the coordinated design of components and process optimization control, activity is guaranteed at the molecular level, fixation and sustained release are achieved at the microstructural level, thereby improving the overall antibacterial performance and durability.

[0073] Test Example 2

[0074] Test objects: Examples 1-2, Examples 4-5 and Comparative Examples 8-13, Comparative Example 17.

[0075] Test method: Octadecenoic acid was dropped onto the surface of a PET film, and the film's oleophobic properties were tested using a contact angle meter. The final test results are shown in Table 2.

[0076] Table 2 Anti-oil performance test results

[0077] serial number Oil contact angle (°) Example 1 63 Example 2 66 Example 4 69 Example 5 68 Comparative Example 8 49 Comparative Example 9 50 Comparative Example 10 55 Comparative Example 11 51 Comparative Example 12 53 Comparative Example 13 56 Comparative Example 17 58

[0078] Comparative Example 8 uses untreated PET masterbatch instead of the modified PET masterbatch. The film matrix lacks the fluorinated segments introduced by chemical grafting, and thus lacks molecular-level oleophobicity. The untreated matrix exhibits poor interfacial compatibility with oil-repellent additives such as polyether-modified polydimethylsiloxane, hindering their dispersion within the matrix and migration to the surface. While the polyether-modified polydimethylsiloxane provides some ease of cleaning, it lacks the bulk oleophobicity provided by the fluorinated modified matrix, allowing oil to spread and penetrate more easily, resulting in a reduced oil contact angle and poor oil repellency. In Comparative Example 9, the modified PET masterbatch is prepared without the addition of perfluoropolyether diol, resulting in no fluorinated modification. The film matrix lacks the extremely low-surface-energy perfluoropolyether segments, lacking molecular-level oleophobicity and failing to effectively repel oil. While the polyether-modified polydimethylsiloxane provides easy cleaning, it lacks the extremely low-surface-energy layer synergistically constructed by the fluorinated segments, resulting in a reduced oil contact angle and poor oil repellency. In Comparative Example 10, the PET resin was not subjected to a hydrolysis pretreatment, resulting in a low initial carboxyl group count and a low grafting rate with the perfluoropolyether diol. This resulted in insufficient fluorine-containing modification, limited oleophobicity of the film as a whole, a weak low-surface-energy effect, a reduced oil contact angle, and compromised oil resistance. In Comparative Example 11, a physical mixture of PET resin and perfluoropolyether diol was directly used instead of the modified PET masterbatch. The perfluoropolyether diol had poor compatibility with the PET resin and was not chemically bonded, making it prone to aggregation, precipitation, or loss during processing and use. The low-surface-energy components on the film surface were unevenly distributed and unstable, significantly reducing the oil contact angle, resulting in poor oil resistance and low durability. In Comparative Example 12, modified polydimethylsiloxane was omitted, resulting in a film lacking the low surface energy and slipperiness it provides. Although the fluorine-containing modified matrix possesses bulk oleophobicity, without the synergistic surface energy reduction and lubrication provided by the modified polydimethylsiloxane, oil droplets spread more easily on the surface, reducing the oil contact angle and impairing oil resistance. Comparative Example 13 uses hydrogenated silicone oil instead of modified polydimethylsiloxane. Hydrogenated silicone oil lacks the compatibility with the PET matrix provided by the polyether segment, and also lacks the specific low surface energy and smooth structure of polyether-modified polydimethylsiloxane. As a result, its dispersion in the matrix, its ability to migrate to the surface, and its anti-oil and smooth effect on the surface are not as good as those of polyether-modified polydimethylsiloxane, and the oil contact angle is reduced, affecting the anti-oil performance. Comparative Example 17 removes the hot calendering process, and the film surface lacks physical densification and physical locking of low surface energy components. The enrichment and uniformity of low surface energy components on the surface are reduced, and the lack of physical locking makes it easy to fall off or wear and tear during use. This results in a reduced oil contact angle, reduced anti-oil performance and reduced durability.

[0079] The comprehensive analysis of the first group of comparative examples reveals that the key to achieving anti-oil performance lies in constructing a stable and low surface energy surface layer. Fluorine-containing modification of the matrix is ​​the basis for providing the bulk oleophobicity, and its effectiveness depends on whether fluorine-containing modification is performed, whether the reaction grafting rate is increased by hydrolysis pretreatment, and whether chemical grafting is superior to physical blending. Modified polydimethylsiloxane, as a synergistic auxiliary agent, provides additional low surface energy and slipperiness, and its specific structure and function are necessary. In terms of process, hot calendering is an important means to improve the durability of anti-oil by promoting the enrichment and physical locking of low surface energy components. These comparative examples show that this patent has jointly constructed an efficient and durable anti-oil function through the synergy of matrix modification and auxiliary agents, and the optimization of the surface structure in the process. The lack of any link or insufficient optimization will lead to poor anti-oil performance.

[0080] Test Example 3

[0081] Test objects: Example 1, Example 4, Examples 6-7 and Comparative Example 3, Comparative Example 5, Comparative Example 12, Comparative Examples 14-15, and Comparative Example 17.

[0082] Test method: PET film was placed under CS-17 grinding wheel for friction, with a pressure of 150g and 100 friction cycles. After friction, the oil contact angle was tested according to the method of Test Example 1. The wear retention rate = (oil contact angle before friction - oil contact angle after friction) / oil contact angle before friction. The higher the wear retention rate, the better the wear resistance. The final test results are shown in Table 3 and Figure 1 shown.

[0083] Table 3 Wear resistance test results

[0084]

[0085]

[0086] In Comparative Example 3, no nanofiller is added. The film lacks a hard reinforcing component and cannot effectively resist cutting and scraping stress, resulting in poor wear resistance and reduced wear resistance retention. In Comparative Example 5, a lower screw speed is used, which affects the uniformity of nanofiller dispersion, makes it easy to agglomerate, causes stress concentration, and cannot effectively bear the dispersed friction load, making it easy to fall off. As a result, the wear resistance enhancement effect of the nanofiller is not fully exerted, and the wear resistance retention is reduced. In Comparative Example 12, no modified polydimethylsiloxane is added. The film lacks internal and external lubricants, the friction coefficient increases, adhesive wear and fatigue wear are aggravated, the wear resistance deteriorates, and the wear resistance retention is reduced. In Comparative Example 14, when preparing nanofillers, nanosilica is not silane-modified, and the interfacial bonding force with the polyethylene terephthalate matrix is ​​weak. The nanoparticles are difficult to disperse and are easily pulled out during friction. As a result, the wear resistance enhancement effect of the nanofiller is not fully exerted, the wear resistance deteriorates, and the wear resistance retention is reduced. In Comparative Example 15, the use of an excessively high stretching ratio may lead to excessive orientation or even breakage of the polyethylene terephthalate molecular chains, reducing the strength and toughness of the matrix, weakening its ability to support the nanofillers, affecting wear resistance, and reducing wear resistance retention. In Comparative Example 17, the removal of the hot calendering process resulted in a lack of densification of the film surface and physical anchoring of the near-surface nanoparticles. This lack of physical anchoring of the near-surface nanoparticles makes them susceptible to detachment during use, resulting in poor surface wear resistance and reduced wear resistance retention.

[0087] A comprehensive analysis of the second group of comparative examples shows that achieving wear resistance depends on hard reinforcement, lubrication and wear reduction, as well as the firm fixation and good dispersion of these functional components in the matrix. Nanofillers are the source of hardness, and modified polydimethylsiloxane is the source of lubrication. Both are indispensable and work together to build a wear-resistant system. The silane modification of nanofillers and the coupling and anchoring with the matrix are the key to ensuring that the hard particles play an effective role and prevent them from falling off. In terms of process, co-blending extrusion dispersion is a prerequisite, and low speed may affect dispersion. The stretching ratio affects the support of the matrix. Hot calendering is an important process for improving surface wear resistance and durability through surface densification and physical locking. These comparative examples show that this patent uses the synergy of nano-enhancement and lubrication, and optimizes dispersion, interface bonding and surface structure in the process to jointly improve the wear resistance of the film. The lack of any link will lead to poor wear resistance.

[0088] Test Example 4

[0089] Test objects: Example 1, Example 6, Examples 8-9 and Comparative Example 6, Comparative Example 8, Comparative Example 15.

[0090] Test method: The test was conducted in accordance with the method in GB / T528-2009. The final test results are shown in Table 4.

[0091] Table 4 Mechanical properties test results

[0092]

[0093]

[0094] Comparative Example 6 uses an extrusion temperature that is too high, resulting in thermal degradation of the polyethylene terephthalate matrix, a significant decrease in molecular weight, and severe deterioration in the bulk strength and toughness of the film. Comparative Example 8 uses untreated PET masterbatch. The mechanical properties of the film matrix depend on the molecular weight of the original PET. There is a lack of synergistic effect of the modified matrix on the filler, and the overall mechanical properties may be insufficient. Comparative Example 15 uses an overly high stretching ratio, which may cause excessive orientation or even breakage of the polyethylene terephthalate molecular chains, resulting in a decrease in the bulk strength and toughness of the film and deterioration in mechanical properties. Comparative Example 16: The weight ratio of pretreated PET to PET resin in the modified PET masterbatch is 4:6. The proportion of pretreated PET is too high. Due to the decrease in molecular weight caused by hydrolysis pretreatment, the excessive proportion of low-molecular-weight pretreated PET significantly reduces the overall molecular weight of the mixed matrix, resulting in a decrease in the bulk strength and toughness of the film.

[0095] A comprehensive analysis of the fourth set of comparative examples demonstrates that achieving excellent mechanical properties depends on the influence of the co-extrusion process and matrix properties. Improper process control or an imbalance in the component ratios can compromise the reinforcing effect of the matrix or filler, leading to decreased mechanical properties. These comparative examples demonstrate that mechanical properties can be improved by optimizing matrix composition and process control.

[0096] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing an antibacterial PET film, characterized in that: The specific steps include: The modified PET masterbatch, composite antibacterial agent, nanofiller, modified polydimethylsiloxane, coupling agent, flame retardant and ultraviolet absorber are melt-blended and extruded to obtain a film sheet; the film sheet is subjected to biaxial orientation stretching, heat stabilization treatment and hot calendering treatment to obtain the antibacterial PET film; The modified PET masterbatch is prepared from pretreated PET resin, PET resin and perfluoropolyether diol; the pretreated resin is prepared from the PET resin by hydrolysis; the composite antibacterial agent includes rosemary extract and dodecyldimethylbenzylammonium chloride; the rosemary extract is prepared from rosemary by an extraction method; the nanofiller is prepared from nanosilica, γ-methacryloyloxypropyltrimethoxysilane and silver nitrate; and the modified polydimethylsiloxane is prepared from hydrogen-containing silicone oil and allyl polyether.

2. The process for preparing an antibacterial PET film according to claim 1, wherein: The modified PET masterbatch is prepared by mixing the pretreated PET resin and the PET resin in a weight ratio of 1.5-2.5:7.5-8.5 to obtain a mixture, adding 4-5% by weight of the perfluoropolyether diol to the mixture, and then melt-extruding and pelletizing the mixture. The pretreated PET resin is prepared by constant temperature treatment of the PET resin at a relative humidity of 65-75% for 3.5-4.5 hours and then drying the mixture.

3. The process for preparing an antibacterial PET film according to claim 1, wherein: The composite antibacterial agent is prepared from rosemary extract and dodecyldimethylbenzyl ammonium chloride in a weight ratio of 1-1.5:1, wherein the preparation method of the rosemary extract comprises: mixing rosemary with an ethanol aqueous solution and soaking at a constant temperature; filtering to separate the soaking liquid and soaking residue; drying the soaking residue; mixing the dried soaking residue with anhydrous ethanol and refluxing and distilling for 1.5-2.5 hours; separating to obtain a distillate and a distillation residue; combining the soaking liquid and the distillate; and concentrating the combined liquid by reduced pressure evaporation to 5-7% of the original volume to obtain the rosemary extract.

4. The process for preparing an antibacterial PET film according to claim 1, wherein: The preparation method of the nanofiller comprises: ultrasonically dispersing nano-silica in an ethanol solution, adding a silane coupling agent and reacting for 2.5-3.5 hours to obtain pretreated nano-silica; ultrasonically dispersing the pretreated nano-silica in a 5-7wt% silver nitrate aqueous solution, adding sodium citrate and reacting for 2-2.5 hours to obtain the nanofiller.

5. The process for preparing an antibacterial PET film according to claim 1, wherein: The modified polydimethylsiloxane is prepared by mixing hydrogenated silicone oil, allyl polyether, and toluene; heating to 95° C. while maintaining nitrogen protection; dropwise adding a platinum-carbon catalyst; stirring and reacting at 95° C. for 4-5 hours, then cooling to room temperature, filtering, and vacuum distilling the filtrate to obtain the modified polydimethylsiloxane; the number average molecular weight of the allyl polyether is 1000-2000.

6. The process for preparing an antibacterial PET film according to claim 1, wherein: The film sheet is prepared by mixing the modified PET masterbatch, 6-8 parts of the nanofiller, 4-5 parts of the modified polydimethylsiloxane, a coupling agent, an ultraviolet absorber, and a flame retardant, and then adding the mixture to a twin-screw extruder for melt blending; and 5-7 parts of the composite antibacterial agent are added in the fourth zone of the twin-screw extruder.

7. The process for preparing an antibacterial PET film according to claim 6, wherein: The working conditions of the twin-screw extruder are as follows: the processing temperature of the first zone of the screw extruder is 250-255°C, the processing temperature of the second and third zones is 255-265°C, the processing temperature of the fourth and fifth zones is 250-260°C, the processing temperature of the die head is 250-260°C, and the screw speed is 250-350rpm.

8. The process for preparing an antibacterial PET film according to claim 1, wherein: The biaxial directional stretching method is as follows: the transverse stretching temperature is 90-110° C., and the transverse stretching ratio is 3-4 times; the longitudinal stretching temperature is 90-110° C., and the longitudinal stretching ratio is 3-4 times.

9. The process for preparing an antibacterial PET film according to claim 1, wherein: The conditions of the hot calendering treatment are: calendering temperature is 180-220° C., and pressure is 10-20 kN / m.

Images